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Sample records for arctic aquatic ecosystem

  1. Energy flow in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1988-12-31

    Natural isotope abundances to trace major pathways of energy flow to consumers in Imnavait Creek and the tundra ecosystem of the R4D watershed with comparative work in the coastal tundra. Our overall goals are to a determine if carbon is accumulating in upland and coastal tundra; determine the role of eroded peat carbon in the aquatic ecosystem; and to determine the distribution of carbon and nitrogen isotopes in the tundra-pond ecosystem to establish the feasibility of using natural differences as tracers. Past work on fishes, birds, and the prey species of insects and aquatic crustaceans has shown that peat carbon is very important in the energy supply supporting the food webs over the course of the year. Obligate freshwater fishes from the coastal lakes and Colville River have been shown to contain up to 60 percent peat carbon at the end of the winter season. In contrast, migratory shorebirds and passerines contained much smaller radiocarbon abundances in summer, indicating a major shift to recent in situ primary production in pond and stream ecosystems in summer months. For the past two years, we have narrowed our focus to the processes supplying carbon to the beaded stream system at MS-117 and have concentrated on determining the transfer and accumulation rates of carbon in the watershed.

  2. [Energy flow in arctic aquatic ecosystems

    SciTech Connect

    Schell, D.M.

    1985-12-31

    This study is aimed at determining the major pathways of energy flow in freshwater ecosystems of the Alaskan arctic coastal plain. Selected sites for study of the processes supplying energy to streams and lakes to verify the generality of past findings will be surveyed for collection of organisms including the Colville River drainage and the lake region around Teshekpuk Lake. Specific objectives are to collect food web apex organisms (fish and birds) from a variety of sites in the coastal plain to verify descriptive models of ecosystem structure and food web pathways and to compare the utilization rates by insect larvae of fresh litter and in situ primary production relative to more refractory peaty materials through seasonal sampling for isotopic analysis.

  3. [Energy flow in arctic aquatic ecosystems

    SciTech Connect

    Schell, D.M.

    1985-01-01

    This study is aimed at determining the major pathways of energy flow in freshwater ecosystems of the Alaskan arctic coastal plain. Selected sites for study of the processes supplying energy to streams and lakes to verify the generality of past findings will be surveyed for collection of organisms including the Colville River drainage and the lake region around Teshekpuk Lake. Specific objectives are to collect food web apex organisms (fish and birds) from a variety of sites in the coastal plain to verify descriptive models of ecosystem structure and food web pathways and to compare the utilization rates by insect larvae of fresh litter and in situ primary production relative to more refractory peaty materials through seasonal sampling for isotopic analysis.

  4. Energy flow in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1983-12-31

    This component of the terrestrial-aquatic interaction group seeks to use the natural stable carbon isotope ratios and radiocarbon abundances to trace the movement of photosynthate from the terrestrial environment to the stream system at MS-117. In addition to estimating the total flux, we will also attempt to describe the relative fractions derived from modern primary production and that derived from delayed inputs of eroded peat. We will also seek to determine the coupling efficiency of these energy sources to the invertebrate faunal populations in the tundra soils and streams.

  5. Energy flow in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1983-01-01

    This component of the terrestrial-aquatic interaction group seeks to use the natural stable carbon isotope ratios and radiocarbon abundances to trace the movement of photosynthate from the terrestrial environment to the stream system at MS-117. In addition to estimating the total flux, we will also attempt to describe the relative fractions derived from modern primary production and that derived from delayed inputs of eroded peat. We will also seek to determine the coupling efficiency of these energy sources to the invertebrate faunal populations in the tundra soils and streams.

  6. AQUATIC ECOSYSTEMS,

    EPA Science Inventory

    Aquatic ecosystems are a vital part of the urban water cycle (and of urban areas more broadly), and, if healthy, provide a range of goods and services valued by humans (Meyer 1997). For example, aquatic ecosystems (e.g., rivers, lakes, wetlands) provide potable water, food resou...

  7. Changing seasonality of Arctic hydrology disrupts key biotic linkages in Arctic aquatic ecosystems.

    NASA Astrophysics Data System (ADS)

    Deegan, L.; MacKenzie, C.; Peterson, B. J.; Fishscape Project

    2011-12-01

    Arctic grayling (Thymallus arcticus) is an important circumpolar species that provide a model system for understanding the impacts of changing seasonality on arctic ecosystem function. Grayling serve as food for other biota, including lake trout, birds and humans, and act as top-down controls in stream ecosystems. In Arctic tundra streams, grayling spend their summers in streams but are obligated to move back into deep overwintering lakes in the fall. Climatic change that affects the seasonality of river hydrology could have a significant impact on grayling populations: grayling may leave overwintering lakes sooner in the spring and return later in the fall due to a longer open water season, but the migration could be disrupted by drought due to increased variability in discharge. In turn, a shorter overwintering season may impact lake trout dynamics in the lakes, which may rely on the seasonal inputs of stream nutrients in the form of migrating grayling into these oligotrophic lakes. To assess how shifting seasonality of Arctic river hydrology may disrupt key trophic linkages within and between lake and stream components of watersheds on the North Slope of the Brooks Mountain Range, Alaska, we have undertaken new work on grayling and lake trout population and food web dynamics. We use Passive Integrated Transponder (PIT) tags coupled with stream-width antenna units to monitor grayling movement across Arctic tundra watersheds during the summer, and into overwintering habitat in the fall. Results indicate that day length may prime grayling migration readiness, but that flooding events are likely the cue grayling use to initiate migration in to overwintering lakes. Many fish used high discharge events in the stream as an opportunity to move into lakes. Stream and lake derived stable isotopes also indicate that lake trout rely on these seasonally transported inputs of stream nutrients for growth. Thus, changes in the seasonality of river hydrology may have broader

  8. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO[sub 2] increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  9. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO{sub 2} increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  10. Reviews and Syntheses: Effects of permafrost thaw on arctic aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Vonk, J. E.; Tank, S. E.; Bowden, W. B.; Laurion, I.; Vincent, W. F.; Alekseychik, P.; Amyot, M.; Billet, M. F.; Canário, J.; Cory, R. M.; Deshpande, B. N.; Helbig, M.; Jammet, M.; Karlsson, J.; Larouche, J.; MacMillan, G.; Rautio, M.; Anthony, K. M. Walter; Wickland, K. P.

    2015-07-01

    dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO2 and CH4), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to address the key gaps in understanding in order to predict the full effects of permafrost thaw on aquatic ecosystems throughout the Arctic, and their consequential feedbacks to climate.

  11. Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Vonk, J. E.; Tank, S. E.; Bowden, W. B.; Laurion, I.; Vincent, W. F.; Alekseychik, P.; Amyot, M.; Billet, M. F.; Canário, J.; Cory, R. M.; Deshpande, B. N.; Helbig, M.; Jammet, M.; Karlsson, J.; Larouche, J.; MacMillan, G.; Rautio, M.; Anthony, K. M. Walter; Wickland, K. P.

    2015-12-01

    of dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO2 and CH4), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to quantify how permafrost thaw is affecting aquatic ecosystems across diverse Arctic landscapes, and the implications of this change for further climate warming.

  12. Methane turnover and methanotrophic communities in arctic aquatic ecosystems of the Lena Delta, Northeast Siberia.

    PubMed

    Osudar, Roman; Liebner, Susanne; Alawi, Mashal; Yang, Sizhong; Bussmann, Ingeborg; Wagner, Dirk

    2016-08-01

    Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a flood plain area. Though, in all aquatic systems, we detected both, Type I and II MOB, in lake systems, we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity. PMID:27230921

  13. BIOGEOCHEMICAL INDICATORS IN AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Loadings of excess organic wastes and associated nutrients to aquatic systems has numerous deleterious consequences with respect to the ecosystem services provided by these important ecosystems including perturbation of organic matter and nutrient cycling rates, reduction in diss...

  14. Systems and Cycles: Learning about Aquatic Ecosystems

    ERIC Educational Resources Information Center

    Hmelo-Silver, Cindy E.; Jordan, Rebecca; Eberbach, Catherine; Rugaber, Spencer; Goel, Ashok

    2011-01-01

    In this research, the authors present both the design and preliminary testing of a technology-intensive classroom intervention designed to support middle schools students' understanding of an aquatic ecosystem. The goals of their intervention are to help learners develop deep understanding of ecosystems and to use tools that make the relationships…

  15. Diversity and Distribution of Aquatic Fungal Communities in the Ny-Ålesund Region, Svalbard (High Arctic) : Aquatic Fungi in the Arctic.

    PubMed

    Zhang, Tao; Wang, Neng-Fei; Zhang, Yu-Qin; Liu, Hong-Yu; Yu, Li-Yan

    2016-04-01

    We assessed the diversity and distribution of fungi in 13 water samples collected from four aquatic environments (stream, pond, melting ice water, and estuary) in the Ny-Ålesund Region, Svalbard (High Arctic) using 454 pyrosequencing with fungi-specific primers targeting the internal transcribed spacer (ITS) region of the ribosomal rRNA gene. Aquatic fungal communities in this region showed high diversity, with a total of 43,061 reads belonging to 641 operational taxonomic units (OTUs) being found. Of these OTUs, 200 belonged to Ascomycota, 196 to Chytridiomycota, 120 to Basidiomycota, 13 to Glomeromycota, and 10 to early diverging fungal lineages (traditional Zygomycota), whereas 102 belonged to unknown fungi. The major orders were Helotiales, Eurotiales, and Pleosporales in Ascomycota; Chytridiales and Rhizophydiales in Chytridiomycota; and Leucosporidiales and Sporidiobolales in Basidiomycota. The common fungal genera Penicillium, Rhodotorula, Epicoccum, Glaciozyma, Holtermanniella, Betamyces, and Phoma were identified. Interestingly, the four aquatic environments in this region harbored different aquatic fungal communities. Salinity, conductivity, and temperature were important factors in determining the aquatic fungal diversity and community composition. The results suggest the presence of diverse fungal communities and a considerable number of potentially novel fungal species in Arctic aquatic environments, which can provide reliable data for studying the ecological and evolutionary responses of fungi to climate change in the Arctic ecosystem. PMID:26492897

  16. Changing Arctic ecosystems: ecology of loons in a changing Arctic

    USGS Publications Warehouse

    Uher-Koch, Brian; Schmutz, Joel; Whalen, Mary; Pearce, John M.

    2014-01-01

    The U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative informs key resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a changing climate. From 2010 to 2014, a key study area for the USGS CAE initiative has been the Arctic Coastal Plain of northern Alaska. This region has experienced rapid warming during the past 30 years, leading to the thawing of permafrost and changes to lake and river systems. These changes, and projections of continued change, have raised questions about effects on wildlife populations that rely on northern lake ecosystems, such as loons. Loons rely on freshwater lakes for nesting habitat and the fish and invertebrates inhabiting the lakes for food. Loons live within the National Petroleum Reserve-Alaska (NPR-A) on Alaska’s northern coast, where oil and gas development is expected to increase. Research by the USGS examines how breeding loons use the Arctic lake ecosystem and the capacity of loons to adapt to future landscape change.

  17. Delineating resource sheds in aquatic ecosystems (presentation)

    EPA Science Inventory

    Analysis of spatially-explicit ecological phenomena in aquatic ecosystems is impeded by a lack of knowledge of, and tools to delimit, spatial patterns of material supply to point locations. Here we apply the concept of "resource sheds" to coasts and watersheds. Resource sheds ar...

  18. Effective Best Management Practices for Nitrogen Removal in Aquatic Ecosystems

    EPA Science Inventory

    Elevated nitrate levels in streams and groundwater are detrimental to human and ecosystem health. The Ground Water and Ecosystems Restoration Division (GWERD) of the USEPA investigates best management practices (BMP’s) that enhance nitrogen removal in aquatic ecosystems througho...

  19. Assessment of potential aquatic herbicide impacts to California aquatic ecosystems.

    PubMed

    Siemering, Geoffrey S; Hayworth, Jennifer D; Greenfield, Ben K

    2008-10-01

    A series of legal decisions culminated in 2002 with the California State Water Resources Control Board funding the San Francisco Estuary Institute to develop and implement a 3-year monitoring program to determine the potential environmental impacts of aquatic herbicide applications. The monitoring program was intended to investigate the behavior of all aquatic pesticides in use in California, to determine potential impacts in a wide range of water-body types receiving applications, and to help regulators determine where to direct future resources. A tiered monitoring approach was developed to achieve a balance between program goals and what was practically achievable within the project time and budget constraints. Water, sediment, and biota were collected under "worst-case" scenarios in close association with herbicide applications. Applications of acrolein, copper sulfate, chelated copper, diquat dibromide, glyphosate, fluridone, triclopyr, and 2,4-D were monitored. A range of chemical analyses, toxicity tests, and bioassessments were conducted. At each site, risk quotients were calculated to determine potential impacts. For sediment-partitioning herbicides, sediment quality triad analysis was performed. Worst-case scenario monitoring and special studies showed limited short-term and no long-term toxicity directly attributable to aquatic herbicide applications. Risk quotient calculations called for additional risk characterizations; these included limited assessments for glyphosate and fluridone and more extensive risk assessments for diquat dibromide, chelated copper products, and copper sulfate. Use of surfactants in conjunction with aquatic herbicides was positively associated with greater ecosystem impacts. Results therefore warrant full risk characterization for all adjuvant compounds. PMID:18293029

  20. Pressure and Buoyancy in Aquatic Ecosystems. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Cowan, Christina E.

    This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module explores some of the characteristics of aquatic organisms which can be…

  1. [Virus and prophages in aquatic ecosystems].

    PubMed

    Sime-Ngando, Télesphore; Colombet, Jonathan

    2009-02-01

    In this review, available data on the structure (diversity, abundance, biomass) and functional imprints (bacteriolysis, lysogeny, gene transfers, regulation of prokaryotic diversity) of natural viruses in the context of food webs in aquatic microbial ecology, and the related biogeochemical cycles, are summarized. Viruses are the most abundant, and probably the most diverse, biological entities in aquatic ecosystems and in the biosphere (i.e., viriosphere). Aquatic viruses typically exceed 107 particles/mL in mesotrophic conditions, the majority being represented by phages without tails and by tailed-phages such as members of the family Siphoviridae. Both types of phages have a small capsid and a small genome size, which is considered an evolutionary adaptation to planktonic life. Their contribution to microbial mortality is significant. There is strong evidence that phages exert a significant pressure on the community structure and diversity and on the diversification of potential hosts, mainly through two major pathways: biogeochemical catalysis from lysis products and horizontal gene transfers. In turn, phages are sensitive to environmental factors, both in terms of integrity and of infectivity. Some phages contain typical viral genes that code for biological functions of interest, such as photosynthesis. In general, development in viral ecology is a source of new knowledge for the scientific community in the domain of environmental sciences, but also in the context of evolutionary biology of living cellular organisms, the obligatory hosts for viruses. For example, the recent discovery of a giant virus that becomes ill through infection by another virus (i.e., a viriophage) is fuelling debate about whether viruses are alive. Finally, future research directions are identified in the context of general aquatic ecology, including ecological researches on cyanophages and other phytoplanktonic phages as a priority, primarily in freshwater lakes. PMID:19295641

  2. Long-term changes in pigmentation of arctic Daphnia provide potential for reconstructing aquatic UV exposure

    NASA Astrophysics Data System (ADS)

    Nevalainen, Liisa; Rantala, Marttiina V.; Luoto, Tomi P.; Ojala, Antti E. K.; Rautio, Milla

    2016-07-01

    Despite the biologically damaging impacts of solar ultraviolet radiation (UV) in nature, little is known about its natural variability, forcing mechanisms, and long-term effects on ecosystems and organisms. Arctic zooplankton, for example the aquatic keystone genus Daphnia (Crustacea, Cladocera) responds to biologically damaging UV by utilizing photoprotective strategies, including pigmentation. We examined the preservation and content of UV-screening pigments in fossil Daphnia remains (ephippia) in two arctic lake sediment cores from Cornwallis Island (Lake R1), Canada, and Spitsbergen (Lake Fugledammen), Svalbard. The aims were to document changes in the degree of UV-protective pigmentation throughout the past centuries, elucidate the adaptive responses of zooplankton to long-term variations in UV exposure, and estimate the potential of fossil zooplankton pigments in reconstructing aquatic UV regimes. The spectroscopic absorbance measurements of fossil Daphnia ephippia under UV (280-400 nm) and visible light (400-700 nm) spectral ranges indicated that melanin (absorbance maxima at UV wavebands 280-350 nm) and carotenoids (absorbance maxima at 400-450 nm) pigments were preserved in the ephippia in both sediment cores. Downcore measurements of the most important UV-protective pigment melanin (absorbance measured at 305 and 340 nm) showed marked long-term variations in the degree of melanisation. These variations likely represented long-term trends in aquatic UV exposure and were positively related with solar radiation intensity. The corresponding trends in melanisation and solar activity were disrupted at the turn of the 20th century in R1, but remained as strong in Fugledammen. The reversed trends in the R1 core were simultaneous with a significant aquatic community reorganization taking place in the lake, suggesting that recent environmental changes, likely related to climate warming had a local effect on pigmentation strategies. This time horizon is also

  3. [Radioecological problems of aquatic ecosystems of the Chernobyl exclusion zone].

    PubMed

    Gudkov, D I; Kuz'menko, M I; Kireev, S I; Nazarov, A B; Shevtsova, N L; Dziubenko, E V; Kaglian, A E

    2009-01-01

    The results of radioactive contamination dynamics in the main components of aquatic ecosystems and the absorbed dose rate for hydrobionts within the Chernobyl accident exclusion zone was analysed. Some cytogenetical and haematological effects of long-term irradiation on aquatic organisms as well as damage of higher aquatic plants by parasitic fungi and gall-producing arthropods were considered. PMID:19507688

  4. The Role of Aquatic Ecosystems in the Elimination of Pollutants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Contamination of aquatic ecosystems is always of concern to environmental scientists; however, these systems also possess unique capabilities allowing them to eliminate or mitigate certain levels of pollutants. Primarily through the presence of vegetation, aquatic ecosystems are known to be capable...

  5. Changing Arctic ecosystems--research to understand and project changes in marine and terrestrial ecosystems of the Arctic

    USGS Publications Warehouse

    Geiselman, Joy; DeGange, Anthony R.; Oakley, Karen; Derksen, Dirk; Whalen, Mary

    2012-01-01

    Ecosystems and their wildlife communities are not static; they change and evolve over time due to numerous intrinsic and extrinsic factors. A period of rapid change is occurring in the Arctic for which our current understanding of potential ecosystem and wildlife responses is limited. Changes to the physical environment include warming temperatures, diminishing sea ice, increasing coastal erosion, deteriorating permafrost, and changing water regimes. These changes influence biological communities and the ways in which human communities interact with them. Through the new initiative Changing Arctic Ecosystems (CAE) the U.S. Geological Survey (USGS) strives to (1) understand the potential suite of wildlife population responses to these physical changes to inform key resource management decisions such as those related to the Endangered Species Act, and (2) provide unique insights into how Arctic ecosystems are responding under new stressors. Our studies examine how and why changes in the ice-dominated ecosystems of the Arctic are affecting wildlife and will provide a better foundation for understanding the degree and manner in which wildlife species respond and adapt to rapid environmental change. Changes to Arctic ecosystems will be felt broadly because the Arctic is a production zone for hundreds of species that migrate south for the winter. The CAE initiative includes three major research themes that span Arctic ice-dominated ecosystems and that are structured to identify and understand the linkages between physical processes, ecosystems, and wildlife populations. The USGS is applying knowledge-based modeling structures such as Bayesian Networks to integrate the work.

  6. Crossing the Threshold - Reviewed Evidence for Regime Shifts in Arctic Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Mård Karlsson, J.; Destouni, G.; Peterson, G.; Gordon, L.

    2009-12-01

    The Arctic is rapidly changing, and the Arctic terrestrial ecosystems may respond to changing conditions in different ways. We review the evidence of regime shifts (ecosystem change from one set of mutually reinforcing feedbacks to another) in Arctic terrestrial ecosystems in relation to the hydrological cycle, as part of a larger interdisciplinary research project on Pan-Arctic ice-water-biogeochemical system responses and social-ecological resilience effects in a warming climate, which has in turn been part of the International Polar Year project Arctic-HYDRA. Such regime shifts may have implications for the Earth system as a whole, through changes in water flows and energy balance that yield feedbacks to hydrology and the local and global climate. Because the presence or absence of permafrost is a main control on local hydrological processes in the Arctic, we use the ecological response to permafrost warming to define three types of regime shifts: 1) Conversion of aquatic to terrestrial ecosystems due to draining of lakes and wetlands caused by permafrost degradation and thermokarst processes, which may have a large impact on local people and animals that depend on these ecosystems for food, domestic needs, and habitat, and on climate as the water conditions influence the direction of CO2 exchange. 2) Conversion of terrestrial to aquatic ecosystems as forests are being replaced by wet sedge meadows, bogs, and thermokarst ponds that favor aquatic birds and mammals, as thawing permafrost atop continuous permafrost undermines and destroys the root zone, leading to collapse and death of the trees. 3) Shifts in terrestrial ecosystems due to transition from tundra to shrubland and/or forest, caused by warming of air and soil, resulting in increased surface energy exchanges and albedo, which may in turn feed back to enhanced warming at the local-regional scale. We compare the impact, scale and key processes for each of these regime shifts, and assess the degree to

  7. Development of resource shed delineation in aquatic ecosystems

    EPA Science Inventory

    Environmental issues in aquatic ecosystems of high management priority involve spatially explicit phenomena that occur over vast areas. A "landscape" perspective is thus necessary, including an understanding of how ecological phenomena at a local scale are affected by physical fo...

  8. Risk Assessment Considerations for Veterinary Medicines in Aquatic Ecosystems

    EPA Science Inventory

    This chapter provides a critical evaluation of prospective and retrospective risk assessment approaches for veterinary medicines in aquatic ecosystems and provides recommendations for possible alternative approaches for hazard characterization.

  9. Review on environmental alterations propagating from aquatic to terrestrial ecosystems.

    PubMed

    Schulz, Ralf; Bundschuh, Mirco; Gergs, René; Brühl, Carsten A; Diehl, Dörte; Entling, Martin H; Fahse, Lorenz; Frör, Oliver; Jungkunst, Hermann F; Lorke, Andreas; Schäfer, Ralf B; Schaumann, Gabriele E; Schwenk, Klaus

    2015-12-15

    Terrestrial inputs into freshwater ecosystems are a classical field of environmental science. Resource fluxes (subsidy) from aquatic to terrestrial systems have been less studied, although they are of high ecological relevance particularly for the receiving ecosystem. These fluxes may, however, be impacted by anthropogenically driven alterations modifying structure and functioning of aquatic ecosystems. In this context, we reviewed the peer-reviewed literature for studies addressing the subsidy of terrestrial by aquatic ecosystems with special emphasis on the role that anthropogenic alterations play in this water-land coupling. Our analysis revealed a continuously increasing interest in the coupling of aquatic to terrestrial ecosystems between 1990 and 2014 (total: 661 studies), while the research domains focusing on abiotic (502 studies) and biotic (159 studies) processes are strongly separated. Approximately 35% (abiotic) and 25% (biotic) of the studies focused on the propagation of anthropogenic alterations from the aquatic to the terrestrial system. Among these studies, hydromorphological and hydrological alterations were predominantly assessed, whereas water pollution and invasive species were less frequently investigated. Less than 5% of these studies considered indirect effects in the terrestrial system e.g. via food web responses, as a result of anthropogenic alterations in aquatic ecosystems. Nonetheless, these very few publications indicate far-reaching consequences in the receiving terrestrial ecosystem. For example, bottom-up mediated responses via soil quality can cascade over plant communities up to the level of herbivorous arthropods, while top-down mediated responses via predatory spiders can cascade down to herbivorous arthropods and even plants. Overall, the current state of knowledge calls for an integrated assessment on how these interactions within terrestrial ecosystems are affected by propagation of aquatic ecosystem alterations. To fill

  10. DNA barcodes for assessment of the biological integrity of aquatic ecosystems

    EPA Science Inventory

    Water quality regulations and aquatic ecosystem monitoring increasingly rely on direct assessments of biological integrity. Because these aquatic “bioassessments” evaluate the incidence and abundance of sensitive aquatic species, they are able to measure cumulative ecosystem eff...

  11. Carbon Cycling in Permafrost Aquatic Systems of Bylot Island, Eastern Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Bouchard, F.; Preskienis, V.; Laurion, I.; Fortier, D.

    2014-12-01

    Aquatic systems are widespread in permafrost environments and play a crucial role in biogeochemical cycles, especially in GHG emissions (CO2, CH4). Amount, rate and age of carbon released from permafrost thawing can be strongly influenced by local geomorphology, which affects the biogeochemical dynamics of ponds and lakes. Bylot Island (Nunavut) is located in the heart of the Eastern Canadian Arctic and comprises numerous glacial and periglacial aquatic landscapes. Several glacial valleys of the island represent highly dynamic biogeosystems rich in permafrost ground ice, peat, and aquatic environments. We aimed at characterizing the influence of geomorphology and permafrost degradation processes on aquatic system biogeochemistry. We sampled gas, water, permafrost and lacustrine sediment in different types of aquatic systems: polygonal ponds, collapsed ice-wedge trough ponds, and larger lakes overlying unfrozen soil ('talik'). Preliminary results and field observations indicate a relationship between pond/lake morphology, processes of permafrost degradation, and the age of carbon processed - ultimately released as GHG - in these aquatic systems. Small and shallow ponds produced modern or young (< 500 yr BP) CO2 and CH4, whereas larger and deeper lakes released older (< 2000 yr BP) gases. We also observed a substantial difference in gas fluxes between similar ponds of comparable size and depth. When pond margins were actively eroding (eroded and collapsed peat blocks), fluxes were several orders of magnitude higher than when their margins were stabilized. Such findings underscore the strong impact of local geomorphology and permafrost degradation processes on aquatic system biogeochemistry. Upscaling of GHG emissions at the watershed scale requires a better understanding of the emissions from different types of ecosystems.

  12. Endocrine-Disrupting Compounds in Aquatic Ecosystems.

    EPA Science Inventory

    Endocrine disrupting chemicals (EDCs) are a ubiquitous issue of concern in our aquatic systems. Commonly detected EDCs include natural and synthetic hormones, surfactants, plasticizers, disinfectants, herbicides and metals. The potency of these chemicals varies substantially, as ...

  13. Watershed geomorphology modifies the temperature sensitivity of aquatic ecosystem metabolism

    NASA Astrophysics Data System (ADS)

    Jankowski, K. J.; Schindler, D.

    2015-12-01

    How carbon cycles are regulated by temperature remains a substantial uncertainty in our understanding of how watersheds will respond to ongoing climate change. Aquatic ecosystems are significant components of carbon flux to the atmosphere and ocean, yet we have limited understanding of how changing thermal regimes will alter rates of ecosystem metabolic processes, and, therefore, aquatic contributions to carbon cycles at watershed to global scales. Watershed geomorphology controls the landscape-scale distribution of organic material that can form the metabolic base of aquatic ecosystems, which will likely affect the temperature sensitivity of aquatic ecosystem metabolism. Across 23 streams in a boreal river basin, we estimated how temperature sensitivity of ecosystem respiration (ER), an important component of the aquatic C cycle, varied among streams with different watershed characteristics. We found that geomorphic conditions imposed strong ultimate controls on temperature sensitivity: ER in streams draining flat watersheds was much more sensitive to temperature than streams draining steeper watersheds. Further, we show that the link between watershed geomorphology and temperature sensitivity was related to changes in the quality of carbon substrates across the gradient in watershed slope. These results suggest that geomorphic conditions will ultimately control how carbon processing responds to warming climate, thereby affecting carbon transport and storage, and likely food web responses, in river networks.

  14. Exploratory hydrocarbon drilling impacts to Arctic lake ecosystems.

    PubMed

    Thienpont, Joshua R; Kokelj, Steven V; Korosi, Jennifer B; Cheng, Elisa S; Desjardins, Cyndy; Kimpe, Linda E; Blais, Jules M; Pisaric, Michael F J; Smol, John P

    2013-01-01

    Recent attention regarding the impacts of oil and gas development and exploitation has focused on the unintentional release of hydrocarbons into the environment, whilst the potential negative effects of other possible avenues of environmental contamination are less well documented. In the hydrocarbon-rich and ecologically sensitive Mackenzie Delta region (NT, Canada), saline wastes associated with hydrocarbon exploration have typically been disposed of in drilling sumps (i.e., large pits excavated into the permafrost) that were believed to be a permanent containment solution. However, failure of permafrost as a waste containment medium may cause impacts to lakes in this sensitive environment. Here, we examine the effects of degrading drilling sumps on water quality by combining paleolimnological approaches with the analysis of an extensive present-day water chemistry dataset. This dataset includes lakes believed to have been impacted by saline drilling fluids leaching from drilling sumps, lakes with no visible disturbances, and lakes impacted by significant, naturally occurring permafrost thaw in the form of retrogressive thaw slumps. We show that lakes impacted by compromised drilling sumps have significantly elevated lakewater conductivity levels compared to control sites. Chloride levels are particularly elevated in sump-impacted lakes relative to all other lakes included in the survey. Paleolimnological analyses showed that invertebrate assemblages appear to have responded to the leaching of drilling wastes by a discernible increase in a taxon known to be tolerant of elevated conductivity coincident with the timing of sump construction. This suggests construction and abandonment techniques at, or soon after, sump establishment may result in impacts to downstream aquatic ecosystems. With hydrocarbon development in the north predicted to expand in the coming decades, the use of sumps must be examined in light of the threat of accelerated permafrost thaw, and the

  15. Exploratory Hydrocarbon Drilling Impacts to Arctic Lake Ecosystems

    PubMed Central

    Thienpont, Joshua R.; Kokelj, Steven V.; Korosi, Jennifer B.; Cheng, Elisa S.; Desjardins, Cyndy; Kimpe, Linda E.; Blais, Jules M.; Pisaric, Michael FJ.; Smol, John P.

    2013-01-01

    Recent attention regarding the impacts of oil and gas development and exploitation has focused on the unintentional release of hydrocarbons into the environment, whilst the potential negative effects of other possible avenues of environmental contamination are less well documented. In the hydrocarbon-rich and ecologically sensitive Mackenzie Delta region (NT, Canada), saline wastes associated with hydrocarbon exploration have typically been disposed of in drilling sumps (i.e., large pits excavated into the permafrost) that were believed to be a permanent containment solution. However, failure of permafrost as a waste containment medium may cause impacts to lakes in this sensitive environment. Here, we examine the effects of degrading drilling sumps on water quality by combining paleolimnological approaches with the analysis of an extensive present-day water chemistry dataset. This dataset includes lakes believed to have been impacted by saline drilling fluids leaching from drilling sumps, lakes with no visible disturbances, and lakes impacted by significant, naturally occurring permafrost thaw in the form of retrogressive thaw slumps. We show that lakes impacted by compromised drilling sumps have significantly elevated lakewater conductivity levels compared to control sites. Chloride levels are particularly elevated in sump-impacted lakes relative to all other lakes included in the survey. Paleolimnological analyses showed that invertebrate assemblages appear to have responded to the leaching of drilling wastes by a discernible increase in a taxon known to be tolerant of elevated conductivity coincident with the timing of sump construction. This suggests construction and abandonment techniques at, or soon after, sump establishment may result in impacts to downstream aquatic ecosystems. With hydrocarbon development in the north predicted to expand in the coming decades, the use of sumps must be examined in light of the threat of accelerated permafrost thaw, and the

  16. Observation Platforms and Data Streams of the Arctic Next Generation Ecosystem Experiment (NGEE-Arctic)

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.; Wullschleger, S. D.; Graham, D. E.; Hubbard, S. S.; Norby, R. J.; Rogers, A.; Torn, M. S.; Wilson, C. J.

    2013-12-01

    The goal of the Arctic Next Generation Ecosystem Experiment (NGEE-Arctic) is to deliver a process-rich ecosystem model, extending from bedrock to the top of the vegetative canopy, in which the evolution of Arctic ecosystems in a changing climate can be modeled at the scale of a high resolution Earth System Model grid cell. Increasing our confidence in climate projections for high-latitude regions of the world requires a coordinated set of observation platforms that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. Initial research has focused upon the highly dynamic landscapes of the North Slope (Barrow, Alaska) where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. This vision includes mechanistic studies in the field and in the laboratory; modeling of critical and interrelated water, nitrogen, carbon, and energy dynamics; and characterization of important interactions from molecular to landscape scales that drive feedbacks to the climate system. To complete these investigations, an integrated program of field monitoring has been initiated. These include observations of meteorological, hydrological, ecological and geophysical processes. These data streams are intended to supplement and extend existing polar data sets to advance our understanding of the Arctic environment and its response to a rapidly changing climate.

  17. Mercury bioaccumulation and biomagnification in a small Arctic polynya ecosystem.

    PubMed

    Clayden, Meredith G; Arsenault, Lilianne M; Kidd, Karen A; O'Driscoll, Nelson J; Mallory, Mark L

    2015-03-15

    Recurring polynyas are important areas of biological productivity and feeding grounds for seabirds and mammals in the Arctic marine environment. In this study, we examined food web structure (using carbon and nitrogen isotopes, δ(13)C and δ(15)N) and mercury (Hg) bioaccumulation and biomagnification in a small recurring polynya ecosystem near Nasaruvaalik Island (Nunavut, Canada). Methyl Hg (MeHg) concentrations increased by more than 50-fold from copepods (Calanus hyperboreus) to Arctic terns (Sterna paradisaea), the abundant predators at this site. The biomagnification of MeHg through members of the food web - using the slope of log MeHg versus δ(15)N - was 0.157 from copepods (C. hyperboreus) to fish. This slope was higher (0.267) when seabird chicks were included in the analyses. Collectively, our results indicate that MeHg biomagnification is occurring in this small polynya and that its trophic transfer is at the lower end of the range of estimates from other Arctic marine ecosystems. In addition, we measured Hg concentrations in some poorly studied members of Arctic marine food webs [e.g. Arctic alligatorfish (Ulcina olrikii) and jellyfish, Medusozoa], and found that MeHg concentrations in jellyfish were lower than expected given their trophic position. Overall, these findings provide fundamental information about food web structure and mercury contamination in a small Arctic polynya, which will inform future research in such ecosystems and provide a baseline against which to assess changes over time resulting from environmental disturbance. PMID:25149682

  18. Environmental estrogens in an urban aquatic ecosystem: II. Biological effects.

    PubMed

    Schultz, Melissa M; Minarik, Thomas A; Martinovic-Weigelt, Dalma; Curran, Erin M; Bartell, Stephen E; Schoenfuss, Heiko L

    2013-11-01

    Urban aquatic ecosystems are often overlooked in toxicological studies even though they serve many ecosystem functions and sustain fish populations despite large-scale habitat alterations. However, urban fish populations are likely exposed to a broad range of stressors, including environmental estrogens (EEs) that may affect anatomy, physiology and reproduction of exposed fish. Although significant progress has been made in establishing ecological consequences of EE exposure, these studies have focused largely on hydrologically simple systems that lack the complexity of urban aquatic environments. Therefore, the objective of this study was to assess the occurrence and biological effects of EEs across a large urbanized aquatic ecosystem. A multi-pronged study design was employed relying on quantitative determination of select EEs by liquid chromatography tandem mass spectrometry and repeated biological monitoring of wild-caught and caged fish for indications of endocrine disruption. Over three years, EEs were measured in aqueous samples (n=42 samples) and biological effects assessed in >1200 male fish across the 2000km(2) aquatic ecosystems of the Greater Metropolitan Area of Chicago, IL. Our study demonstrated that in addition to water reclamation plant (WRP) effluents, non-WRP sources contribute significant EE loads to the aquatic ecosystem. While resident and caged male fish responded with the induction of the egg-yolk protein vitellogenin, an indicator of EE exposure, neither resident nor caged sunfish exhibited prevalent histopathological changes to their reproductive organs (i.e., intersex) that have been reported in other studies. Vitellogenin induction was greater in spring than the fall and was not correlated with body condition factor, gonadosomatic index or hepatosomatic index. Exposure effects were not correlated with sites downstream of treated effluent discharge further affirming the complexity of sources and effects of EEs in urban aquatic ecosystems

  19. Geologic processes influence the effects of mining on aquatic ecosystems

    USGS Publications Warehouse

    Schmidt, Travis S.; Clements, William H.; Wanty, Richard B.; Verplanck, Philip L.; Church, Stanley E.; San Juan, Carma A.; Fey, David L.; Rockwell, Barnaby W.; DeWitt, Ed H.; Klein, Terry L.

    2012-01-01

    Geologic processes strongly influence water and sediment quality in aquatic ecosystems but rarely are geologic principles incorporated into routine biomonitoring studies. We test if elevated concentrations of metals in water and sediment are restricted to streams downstream of mines or areas that may discharge mine wastes. We surveyed 198 catchments classified as “historically mined” or “unmined,” and based on mineral-deposit criteria, to determine whether water and sediment quality were influenced by naturally occurring mineralized rock, by historical mining, or by a combination of both. By accounting for different geologic sources of metals to the environment, we were able to distinguish aquatic ecosystems limited by metals derived from natural processes from those due to mining. Elevated concentrations of metals in water and sediment were not restricted to mined catchments; depauperate aquatic communities were found in unmined catchments. The type and intensity of hydrothermal alteration and the mineral deposit type were important determinants of water and sediment quality as well as the aquatic community in both mined and unmined catchments. This study distinguished the effects of different rock types and geologic sources of metals on ecosystems by incorporating basic geologic processes into reference and baseline site selection, resulting in a refined assessment. Our results indicate that biomonitoring studies should account for natural sources of metals in some geologic environments as contributors to the effect of mines on aquatic ecosystems, recognizing that in mining-impacted drainages there may have been high pre-mining background metal concentrations.

  20. BIOGEOCHEMISTRY OF CHLORINATED ORGANIC CONTAMINANTS IN AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Over the last several years we have conducted both laboratory and field studies to develop a better understanding of the movement of chlorinated organic compounds through aquatic ecosystems, with special emphasis on the differential movement of these compounds due to physical/che...

  1. Developing an Interdisciplinary Curriculum Framework for Aquatic-Ecosystem Modeling

    ERIC Educational Resources Information Center

    Saito, Laurel; Segale, Heather M.; DeAngelis, Donald L.; Jenkins, Stephen H.

    2007-01-01

    This paper presents results from a July 2005 workshop and course aimed at developing an interdisciplinary course on modeling aquatic ecosystems that will provide the next generation of practitioners with critical skills for which formal training is presently lacking. Five different course models were evaluated: (1) fundamentals/general principles…

  2. ABIOTIC TRANSFORMATION PATHWAYS OF ORGANIC CHEMICALS IN AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Information is presented for assessing the potential of an organic chemical to undergo abiotic transformation in aquatic ecosystems. hen predicting the environmental fate of an organic chemical, two primary questions must be addressed. irst, what are the reaction kinetics for the...

  3. AQUATIC ECOSYSTEM MONITORING AND ASSESSMENT ACROSS SCALES

    EPA Science Inventory

    The mission of the United States Environmental Protection Agency (USEPA) is to protect human health and the environment. As part of the Office of Research and Development within the USEPA, the Ecosystems Research Branch of the National Exposure Research Laboratory, located in Ci...

  4. Measurement of undisturbed di-nitrogen emissions from aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Qin, Shuping, Clough, Timothy, Lou, Jiafa; Hu, Chunsheng; Oenema, Oene; Wrage-Mönnig, Nicole; Zhang, Yuming

    2016-04-01

    Increased production of reactive nitrogen (Nr) from atmospheric di-nitrogen (N2) during the last century has greatly contributed to increased food production1-4. However, enriching the biosphere with Nr through N fertilizer production, combustion, and biological N2 fixation has also caused a series of negative effects on global ecosystems 5,6, especially aquatic ecosystems7. The main pathway converting Nr back into the atmospheric N2 pool is the last step of the denitrification process, i.e., the reduction of nitrous oxide (N2O) into N2 by micro-organisms7,8. Despite several attempts9,10, there is not yet an accurate, fast and direct method for measuring undisturbed N2 fluxes from denitrification in aquatic sediments at the field scale11-14. Such a method is essential to study the feedback of aquatic ecosystems to Nr inputs1,2,7. Here we show that the measurement of both N2O emission and its isotope signature can be used to infer the undisturbed N2 fluxes from aquatic ecosystems. The microbial reduction of N2O increases the natural abundance of 15N-N2O relative to 14N-N2O (δ15N-N2O). We observed linear relationships between δ15N-N2O and the logarithmic transformed N2O/(N2+N2O) emission ratios. Through independent measurements, we verified that the undisturbed N2 flux from aquatic ecosystems can be inferred from measurements of N2O emissions and the δ15N-N2O signature. Our method allows the determination of field-scale N2 fluxes from undisturbed aquatic ecosystems, and thereby allows model predictions of denitrification rates to be tested. The undisturbed N2 fluxes observed are almost one order of magnitude higher than those estimated by the traditional method, where perturbation of the system occurs, indicating that the ability of aquatic ecosystems to remove Nr may have been severely underestimated.

  5. A new way to study the changing Arctic ecosystem

    ScienceCinema

    Hubbard, Susan

    2013-05-29

    Berkeley Lab scientists Susan Hubbard and Margaret Torn discuss the proposed Next Generation Ecosystem Experiment, which is designed to answer one of the most urgent questions facing researchers today: How will a changing climate impact the Arctic, and how will this in turn impact the planet's climate? More info: http://newscenter.lbl.gov/feature-stories/2011/09/14/alaska-climate-change/

  6. A new way to study the changing Arctic ecosystem

    SciTech Connect

    Hubbard, Susan

    2011-01-01

    Berkeley Lab scientists Susan Hubbard and Margaret Torn discuss the proposed Next Generation Ecosystem Experiment, which is designed to answer one of the most urgent questions facing researchers today: How will a changing climate impact the Arctic, and how will this in turn impact the planet's climate? More info: http://newscenter.lbl.gov/feature-stories/2011/09/14/alaska-climate-change/

  7. Communicating Climate and Ecosystem Change in the Arctic

    NASA Astrophysics Data System (ADS)

    Soreide, N. N.; Overland, J. E.; Calder, J. A.; Rodionov, S.

    2005-12-01

    There is an explosion of interest in Northern Hemisphere climate, highlighting the importance of recent changes in the Arctic on mid-latitude climate and its impact on marine and terrestrial ecosystems. Traditional sea ice and tundra dominated arctic ecosystems are being reorganizing into warmer sub-arctic ecosystem types. Over the previous two years we have developed a comprehensive, near real-time arctic change detection protocol to track physical and biological changes for presentation on the web: http://www.arctic.noaa.gov/detect. The effort provides a continuous update to the Arctic Climate Impact Assessment (ACIA) Report, released in November 2004. Principles for the protocol include an accessible narrative style, scientifically credible and objective indicators, notes multiple uses for the information, acknowledges uncertainties, and balances having too many indicators-which leads to information overload-and too few-which does not capture the complexity of the system. Screening criteria include concreteness, public awareness, being understandable, availability of historical time series, and sensitivity. The site provides sufficient information for an individual to make their own assessment regarding the balance of the evidence for tracking change. The product provides an overview, recent news, links to many arctic websites, and highlights climate, global impacts, land and marine ecosystems, and human consequences. Since its inception a year ago, it has averaged about 9000 hits an day on the web, and is a major information source as determined by Google search. The future direction focuses on understanding the causes for change. In spring 2005 we also presented a near real-time ecological and climatic surveillance website for the Bering Sea: www.beringclimate.noaa.gov. The site provides up-to-date information which ties northward shifts of fish, invertebrate and marine mammal populations to physical changes in the Arctic. This site is more technical than the

  8. A successful closed aquatic ecosystem in SZ-8 mission

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyan; Wang, Gaohong; Richter, Peter; Liu, Yongding; Schuster, Martin; Lebert, Michael

    2012-07-01

    Aquatic ecosystem is a useful means to explore complex interaction among different species, and data got from this kind of system can be used to re-constructer or bio-remedy damaged ecosystem or explore other planet, such as Mars. To deeply investigate interactions of different species in space environment, we established a closed aquatic ecosystem of 60 milliliter with Chlorella, Euglena and Bulinus. As a major oxygen producer, Euglena was put into the lower chamber. The initial concentration of Euglena was adjusted to 40000 cells per milliliter to avoid damage of high oxygen concentration to other organisms. As a secondary oxygen producer and food provider, Chlorella was put into the upper chamber together with 3 bulinus. The initial concentration of Chlorella was 3.2*105 cells per milliliter. After 17.5 days of duration, the system run well with 1 bulinus alive in the spaceflight group and all kept alive in the ground control.

  9. Pulses, linkages, and boundaries of coupled aquatic-terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Tockner, K.

    2009-04-01

    Riverine floodplains are linked ecosystems where terrestrial and aquatic habitats overlap, creating a zone where they interact, the aquatic-terrestrial interface. The interface or boundary between aquatic and terrestrial habitats is an area of transition, contact or separation; and connectivity between these habitats may be defined as the ease with which organisms, matter or energy traverse these boundaries. Coupling of aquatic and terrestrial systems generates intertwining food webs, and we may predict that coupled systems are more productive than separated ones. For example, riparian consumers (aquatic and terrestrial) have alternative prey items external to their respective habitats. Such subsidized assemblages occupy a significant higher trophic position than assemblages in unsubsidized areas. Further, cross-habitat linkages are often pulsed; and even small pulses of a driver (e.g. short-term increases in flow) can cause major resource pulses (i.e. emerging aquatic insects) that control the recipient community. For example, short-term additions of resources, simulating pulsed inputs of aquatic food to terrestrial systems, suggest that due to resource partitioning and temporal separation among riparian arthropod taxa the resource flux from the river to the riparian zone increases with increasing riparian consumer diversity. I will discuss the multiple transfer and transformation processes of matter and organisms across aquatic-terrestrial habitats. Key landscape elements along river corridors are vegetated islands that function as instream riparian areas. Results from Central European rivers demonstrate that islands are in general more natural than fringing riparian areas, contribute substantially to total ecotone length, and create diverse habitats in the aquatic and terrestrial realm. In braided rivers, vegetated islands are highly productive landscape elements compared to the adjacent aquatic area. However, aquatic habitats exhibit a much higher decomposition

  10. Freshwater ecosystems and aquatic insects: a paradox in biological invasions.

    PubMed

    Fenoglio, Stefano; Bonada, Núria; Guareschi, Simone; López-Rodríguez, Manuel J; Millán, Andrés; Tierno de Figueroa, J Manuel

    2016-04-01

    Biological invasions have increased significantly in response to global change and constitute one of the major causes of biodiversity loss. Insects make up a large fraction of invasive species, in general, and freshwaters are among the most invaded ecosystems on our planet. However, even though aquatic insects dominate most inland waters, have unparalleled taxonomic diversity and occupy nearly all trophic niches, there are almost no invasive insects in freshwaters. We present some hypotheses regarding why aquatic insects are not common among aquatic invasive organisms, suggesting that it may be the result of a suite of biological, ecological and anthropogenic factors. Such specific knowledge introduces a paradox in the current scientific discussion on invasive species; therefore, a more in-depth understanding could be an invaluable aid to disentangling how and why biological invasions occur. PMID:27072403

  11. Global ecological impacts of invasive species in aquatic ecosystems.

    PubMed

    Gallardo, Belinda; Clavero, Miguel; Sánchez, Marta I; Vilà, Montserrat

    2016-01-01

    alteration). Considering the strong trophic links that characterize aquatic ecosystems, this framework is relevant to anticipate the far-reaching consequences of biological invasions on the structure and functionality of aquatic ecosystems. PMID:26212892

  12. Aquatic ecosystem condition: The Fraser River Action Plan approach

    SciTech Connect

    Tuominen, T.; Raymond, B.; Sekela, M.; Reynoldson, T.

    1995-12-31

    A major goal of the Canadian government`s Fraser River Action Plan (FRAP) is to clean up existing pollution problems in the Fraser River Basin. In support of this goal, the Environmental Quality Assessment Program is assessing the quality of the aquatic environment, particularly with respect to contaminants. The program, conducted from 1993 to 1998, is to establish a baseline condition for the aquatic ecosystem against which the success of clean up efforts can be measured. The FRAP approach is to use a combination of contaminant exposure or stressor indicators and organism ``effects`` indicators. The focus is on three components of the aquatic ecosystem: (1) bed sediment, (2) resident fish and (3) benthos. A priority for the program is integration of the three components, wherever possible. Bed sediments, as indicators of contaminant stress, are sampled at fourteen reaches in the river and major tributaries. Two species of resident fish are sampled and analyzed for condition factors, enzyme induction, histopathology and contaminant content at each of nine sites in the basin. The resident fish data are providing a measure of contaminant exposure and effect. Organism community effects will be assessed by a study which is classifying approximately 200 tributary and mainstem sites based on benthos community structure. For the first time in a large river system in Canada, this benthos study uses a multivariate approach which relates a suite of chemical and physical characteristics to benthos community structure.

  13. Aquatic biodiversity in forests: A weak link in ecosystem services resilience

    USGS Publications Warehouse

    Penaluna, Brooke E.; Olson, Deanna H.; Flitcroft, Rebecca L; Weber, Matthew A.; Bellmore, James R.; Wondzell, Steven M.; Dunham, Jason; Johnson, Sherri L.; Reeves, Gordon H.

    2016-01-01

    The diversity of aquatic ecosystems is being quickly reduced on many continents, warranting a closer examination of the consequences for ecological integrity and ecosystem services. Here we describe intermediate and final ecosystem services derived from aquatic biodiversity in forests. We include a summary of the factors framing the assembly of aquatic biodiversity in forests in natural systems and how they change with a variety of natural disturbances and human-derived stressors. We consider forested aquatic ecosystems as a multi-state portfolio, with diverse assemblages and life-history strategies occurring at local scales as a consequence of a mosaic of habitat conditions and past disturbances and stressors. Maintaining this multi-state portfolio of assemblages requires a broad perspective of ecosystem structure, various functions, services, and management implications relative to contemporary stressors. Because aquatic biodiversity provides multiple ecosystem services to forests, activities that compromise aquatic ecosystems and biodiversity could be an issue for maintaining forest ecosystem integrity. We illustrate these concepts with examples of aquatic biodiversity and ecosystem services in forests of northwestern North America, also known as Northeast Pacific Rim. Encouraging management planning at broad as well as local spatial scales to recognize multi-state ecosystem management goals has promise for maintaining valuable ecosystem services. Ultimately, integration of information from socio-ecological ecosystems will be needed to maintain ecosystem services derived directly and indirectly from forest aquatic biota.

  14. DEVELOPMENT OF A DISTURBANCE INDEX TO ASSESS THE CONDITION OF AQUATIC ECOSYSTEMS

    EPA Science Inventory

    An objective of aquatic monitoring is to assess the condition of aquatic habitats and biota. To rationally interpret aquatic condition, we must identify the range of human activities and the risks they pose to aquatic ecosystems. Placing stream reaches and their watersheds on a...

  15. Improved Climate Prediction through a System Level Understanding of Arctic Terrestrial Ecosystems: Next Generation Ecosystem Experiments (NGEE-Arctic)*

    NASA Astrophysics Data System (ADS)

    Hubbard, S. S.; Graham, D. E.; Hinzman, L. D.; Liang, L.; Liljedahl, A.; Norby, R. J.; Rogers, A.; Rowland, J. C.; Thornton, P. E.; Torn, M. S.; Riley, W. J.; Wilson, C. J.; Wullschleger, S. D.

    2013-12-01

    Characterized by vast amounts of carbon stored in permafrost and a rapidly evolving landscape, the Arctic has emerged as an important focal point for the study of climate change. Although recognized as an ecosystem highly vulnerable to climate change, mechanisms that govern feedbacks between the terrestrial and climate system are not well understood. Increasing our confidence in climate projections for high-latitude regions of the world requires coordinated investigations that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE-Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. The NGEE-Arctic project is a large, multi-disciplinary activity sponsored by the Department of Energy, Office of Science. Recent NGEE-Arctic research has focused on the highly dynamic landscapes of the North Slope Arctic tundra where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. The project is working on the Barrow Environmental Observatory to study interactions that drive critical climate feedbacks within these environments through greenhouse gas fluxes and changes in surface energy balance associated with permafrost degradation and the many other processes that arise as a result of these landscape dynamics. Ongoing are mechanistic studies in the field and in the laboratory; modeling of critical and interrelated water, nitrogen, carbon, and energy dynamics; and characterization of important interactions from molecular to landscape scales that drive feedbacks to the climate system. A suite of climate-, intermediate- and fine-scale models are being used to guide observations and interpret data, while characterization information and process studies serve to initialize state variables in models, provide new algorithms and

  16. Alaska's Arctic Landscapes: Land cover, Monitoring and Assessing Arctic Ecosystems and their Change Agents

    NASA Astrophysics Data System (ADS)

    Guyer, P. S.

    2013-12-01

    The challenge for agencies who manage the 89,000 square miles constituting Alaska's arctic ecoregion is in understanding what, where and to what extent important ecosystems exist. How do each of these ecosystems function? What are the key components of these ecosystems? How are they affected by the changing climate, fire, permafrost changes and development? Answers to these management questions come not from one specific project or program but from a series of data gathering efforts. Landcover mapping of Alaska's arctic using satellite imagery began in the mid 1990's. Over the past three years the land cover has been updated using additional ground truth data and the most up to date image processing software. In 2012, the updated map was used for the first time to select sites for an inventory and monitoring pilot project. The project established a baseline of information for long-term monitoring of regional ecological components. That same year the Bureau of Land Management began a Rapid Ecoregional Assessment across the North Slope of Alaska. This effort will utilize the known environments established by the land cover map and will model the effects of climate change, fire, permafrost change and development. The assessment and modeling effort will show how the effect of these change agents would shape long term conservation, restoration and development efforts. These interactions together will advance the understanding of the arctic ecoregion its values, processes and functions and how the agents of change will shape the future.

  17. Brominated flame retardants in aquatic organisms from the North Sea in comparison with biota from the high Arctic marine environment.

    PubMed

    Sørmo, Eugen G; Jenssen, Bjørn M; Lie, Elisabeth; Skaare, Janneche U

    2009-10-01

    The extent of trophic transfer of brominated flame retardants (BFRs), including hexabromocyclododecane (HBCD) and seven polybrominated diphenyl ethers (PBDEs), were examined in pelagic and benthic aquatic animals (invertebrates and fish) in a near-shore estuary environment of the southeastern North Sea (Norway; 59 degrees N). Whole-body burdens of HBCD and several of the most abundant PBDEs biomagnified with increasing trophic position in the food web. Biomagnification of HBCD was particularly strong, resulting in whole-body burdens of this compound comparable to those of total PBDEs in the higher-trophic-level species. Body burdens of PBDEs were higher in pelagic than in benthic aquatic organisms. This was particularly evident for the lesser-brominated and volatile PBDE congeners. Atmospheric gas-water-phytoplankton exchange of these volatile compounds over the water surface may account for this observation. The PBDE burdens in pelagic zooplankton from the North Sea were more than 60-fold greater than those in corresponding pelagic zooplankton from the colder high Arctic latitudes (>78 degrees N) of Norway (Svalbard). This great difference may relate to reduced chemical gas-water exchange over open waters at the colder Arctic latitudes. However, previously measured whole-body burdens of BFRs in other aquatic marine organisms from the high Arctic were comparable or even exceeded those in the North Sea samples of the present study. These include sympagic (sea ice-associated) invertebrates and fish accumulating high burdens of particle-associated BFRs. The present study provides new insight regarding the distribution of BFRs in ecologically different compartments of marine ecosystems, essential information for understanding the food-web transfer and geographical dispersal of these compounds. PMID:19459721

  18. Satellite Monitoring of Disturbances in Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Prieto-Blanco, A.; Disney, M.; Lewis, P.

    2008-12-01

    We explored the capability of satellite remote sensing to detect temporal changes in northern Fennoscandian regions through the application of a temporal model of surface bidirectional reflectance. Remote sensing offers the potential to monitor changes over large areas and at hard to access locations. Specifically in remote Arctic locations, where ground surveys and aircraft observations are constrained by weather conditions and logistics, remote sensing provides a unique capability for repetitive and frequent sampling. A major disturbance in mountain birch forests typical of northern Sweden and Finland is caused by outbreaks of defoliating insects such as the autumn moth (Epirrita autumnata) and the winter moth (Operophtera brumata). These outbreaks occur more or less cyclically every 9-10 years and attack mainly birch (Betula spp.) leaving a mosaic of open woodland within the forest. It is expected that global warming will affect the incidence and the intensity of this outbreaks. The ecological and economical consequences can be severe hence the importance of close monitoring of shifts in the distribution of events. Defoliated areas of up to 6000 to 7000 ha of birch forest have been reported. Severely affected areas could potentially be detected by satellite providing valuable data to understand the behavior, estimate the damage and predict the development of forest pests. Quantification of the impact of such outbreaks will also permit far more accurate estimation of the terrestrial carbon budget of such regions. Here we applied a generic algorithm to detect sudden changes on land surface cover to daily 500m MODIS surface reflectance data over the Fennoscandian area. Moderate Resolution Imaging Spectraradiometer (MODIS) sensors on board the polar orbiting satellites Terra and Aqua provide an overpass at least once a day over the area of interest. Unfortunately, frequent cloud cover limits the acquisition of satellite imagery and persistent cloud cover may

  19. Arctic epishelf lakes as sentinel ecosystems: Past, present and future

    NASA Astrophysics Data System (ADS)

    Veillette, Julie; Mueller, Derek R.; Antoniades, Dermot; Vincent, Warwick F.

    2008-12-01

    Ice shelves are a prominent but diminishing feature of the northern coastline of Ellesmere Island in the Canadian High Arctic (latitude 82-83°N). By blocking embayments and fiords, this thick coastal ice can create epishelf lakes, which are characterized by a perennially ice-capped water column of freshwater overlying seawater. The goal of this study was to synthesize new, archived, and published data on Arctic epishelf lakes in the context of climate change. Long-term changes along this coastline were evaluated using historical reports, cartographic analysis, RADARSAT imagery, and field measurements. These data, including salinity-temperature profiling records from Disraeli Fiord spanning 54 years, show the rapid decline and near disappearance of this lake type in the Arctic. Salinity-temperature profiling of Milne Fiord, currently blocked by the Milne Ice Shelf, confirmed that it contained an epishelf lake composed of a 16-m thick freshwater layer overlying seawater. A profiling survey along the coast showed that there was a continuum of ice-dammed lakes from shallow systems dammed by multiyear landfast sea ice to deep epishelf lakes behind ice shelves. The climate warming recently observed in this region likely contributed to the decline of epishelf lakes over the last century, and the air temperature trend predicted for the Arctic over the next several decades implies the imminent loss of this ecosystem type. Our results underscore the distinctive properties of coastal ice-dammed lakes and their value as sentinel ecosystems for the monitoring of regional and global climate change.

  20. The Northern Bering Sea: An Arctic Ecosystem in Change

    NASA Astrophysics Data System (ADS)

    Grebmeier, J. M.; Cooper, L. W.

    2004-12-01

    Arctic systems can be rich and diverse habitats for marine life in spite of the extreme cold environment. Benthic faunal populations and associated biogeochemical cycling processes are influenced by sea-ice extent, seawater hydrography (nutrients, salinity, temperature, currents), and water column production. Benthic organisms on the Arctic shelves and margins are long-term integrators of overlying water column processes. Because these organisms have adapted to living at cold extremes, it is reasonable to expect that these communities will be among the most susceptible to climate warming. Recent observations show that Arctic sea ice in the North American Arctic is melting and retreating northward earlier in the season and the timing of these events can have dramatic impacts on the biological system. Changes in overlying primary production, pelagic-benthic coupling, and benthic production and community structure can have cascading effects to higher trophic levels, particularly benthic feeders such as walruses, gray whales, and diving seaducks. Recent indicators of contemporary Arctic change in the northern Bering Sea include seawater warming and reduction in ice extent that coincide with our time-series studies of benthic clam population declines in the shallow northern Bering shelf in the 1990's. In addition, declines in benthic amphipod populations have also likely influenced the movement of feeding gray whales to areas north of Bering Strait during this same time period. Finally a potential consequence of seawater warming and reduced ice extent in the northern Bering Sea could be the northward movement of bottom feeding fish currently in the southern Bering Sea that prey on benthic fauna. This would increase the feeding pressure on the benthic prey base and enhance competition for this food source for benthic-feeding marine mammals and seabirds. This presentation will outline recent biological changes observed in the northern Bering Sea ecosystem as documented in

  1. Physical Thresholds as Ecological Proxies in Aquatic Ecosystems

    NASA Astrophysics Data System (ADS)

    Hausner, M. B.; Gaines, D. B.; Morrison, R. R.; Sada, D. W.; Scoppettone, G. G.; Stone, M. C.; Suarez, F. I.; Tyler, S. W.; Wilson, K. P.

    2015-12-01

    It is often difficult to directly quantify ecological thresholds and predict ecological responses to changing environmental conditions. Here, we present two case studies from Death Valley National Park - Devils Hole and Travertine Springs - in which physical parameters are used as proxies for ecological processes to assess the consequences of environmental change on aquatic ecosystems. In Devils Hole, seasonal thresholds for water temperature and food availability are defined to quantify the optimal recruitment window for the Devils Hole pupfish (Cyprinodon diabolis). At Travertine Springs, physical thresholds of water depth, velocity, and temperature are used to define the spatial extent of the preferred habitat of several threatened macroinvertebrate species. In both systems, mechanistic models are developed to predict the response of those physical thresholds to changing environmental conditions informed by climate change scenarios and potential changes in water availability. By examining the temporal and spatial response of targeted physical parameters to alternative scenarios, we can assess potential ecosystem impacts without direct measurement of ecological processes.

  2. Three month performances of Closed Aquatic Ecosystem on ground

    NASA Astrophysics Data System (ADS)

    Wang, Gaohong; Hao, Zongjie; Hu, Chunxiang; Liu, Yongding

    A Closed Aquatic Ecosystem (CAES) was developed to study on performance of closed ecosystems for three month as a preparation for future spaceflight experiments. The system housed three small freshwater snails (Bulinus australianus) and autotrophic green algae (Chlorella pyrenoidosa) in a 500mL box with light and temperature control. The special sensors for pH value, oxygen concentration, biomass, temperature and light were developed for long-time performance. It was found that algae biomass increased for several days and then leveled off, and light and temperature control indicated normally, pH and oxygen concentration was affect by light cycle but they met the snails' requirement for live. After three month experiment, the snails survive successfully and laid some eggs in box, and the atmosphere and biomass for food were met snails' requirement. The results on ground demonstrated the biological stability and technical reliability for future spaceflight experiment.

  3. Aquatic noise pollution: implications for individuals, populations, and ecosystems.

    PubMed

    Kunc, Hansjoerg P; McLaughlin, Kirsty Elizabeth; Schmidt, Rouven

    2016-08-17

    Anthropogenically driven environmental changes affect our planet at an unprecedented scale and are considered to be a key threat to biodiversity. According to the World Health Organization, anthropogenic noise is one of the most hazardous forms of anthropogenically driven environmental change and is recognized as a major global pollutant. However, crucial advances in the rapidly emerging research on noise pollution focus exclusively on single aspects of noise pollution, e.g. on behaviour, physiology, terrestrial ecosystems, or on certain taxa. Given that more than two-thirds of our planet is covered with water, there is a pressing need to get a holistic understanding of the effects of anthropogenic noise in aquatic ecosystems. We found experimental evidence for negative effects of anthropogenic noise on an individual's development, physiology, and/or behaviour in both invertebrates and vertebrates. We also found that species differ in their response to noise, and highlight the potential underlying mechanisms for these differences. Finally, we point out challenges in the study of aquatic noise pollution and provide directions for future research, which will enhance our understanding of this globally present pollutant. PMID:27534952

  4. Aquatic noise pollution: implications for individuals, populations, and ecosystems

    PubMed Central

    Kunc, Hansjoerg P.; McLaughlin, Kirsty Elizabeth; Schmidt, Rouven

    2016-01-01

    Anthropogenically driven environmental changes affect our planet at an unprecedented scale and are considered to be a key threat to biodiversity. According to the World Health Organization, anthropogenic noise is one of the most hazardous forms of anthropogenically driven environmental change and is recognized as a major global pollutant. However, crucial advances in the rapidly emerging research on noise pollution focus exclusively on single aspects of noise pollution, e.g. on behaviour, physiology, terrestrial ecosystems, or on certain taxa. Given that more than two-thirds of our planet is covered with water, there is a pressing need to get a holistic understanding of the effects of anthropogenic noise in aquatic ecosystems. We found experimental evidence for negative effects of anthropogenic noise on an individual's development, physiology, and/or behaviour in both invertebrates and vertebrates. We also found that species differ in their response to noise, and highlight the potential underlying mechanisms for these differences. Finally, we point out challenges in the study of aquatic noise pollution and provide directions for future research, which will enhance our understanding of this globally present pollutant. PMID:27534952

  5. Pleistocene graminoid-dominated ecosystems in the Arctic

    NASA Astrophysics Data System (ADS)

    Blinnikov, Mikhail S.; Gaglioti, Benjamin V.; Walker, Donald A.; Wooller, Matthew J.; Zazula, Grant D.

    2011-10-01

    We review evidence obtained from analyses of multiple proxies (floristics, mammal remains, paleoinsects, pollen, macrofossils, plant cuticles, phytoliths, stable isotopes, and modeling) that elucidate the composition and character of the graminoid-dominated ecosystems of the Pleistocene Arctic. The past thirty years have seen a renewed interest in this now-extinct biome, sometimes referred to as "tundra-steppe" (steppe-tundra in North American sources). While many questions remain, converging evidence from many new terrestrial records and proxies coupled with better understanding of paleoclimate dynamics point to the predominance of xeric and cold adapted grassland as the key former vegetation type in the Arctic confirming earlier conjectures completed in the 1960s-1980s. A variety of still existing species of grasses and forbs played key roles in the species assemblages of the time, but their mixtures were not analogous to the tundras of today. Local mosaics based on topography, proximity to the ice sheets and coasts, soil heterogeneity, animal disturbance, and fire regimes were undoubtedly present. However, inadequate coverage of terrestrial proxies exist to resolve this spatial heterogeneity. These past ecosystems were maintained by a combination of dry and cold climate and grazing pressure/disturbance by large (e.g., mammoth and horse) and small (e.g., ground squirrels) mammals. Some recent studies from Eastern Beringia (Alaska) suggest that more progress will be possible when analyses of many proxies are combined at local scales.

  6. Environmental bacteriophages: viruses of microbes in aquatic ecosystems

    PubMed Central

    Sime-Ngando, Télesphore

    2014-01-01

    Since the discovery 2–3 decades ago that viruses of microbes are abundant in marine ecosystems, viral ecology has grown increasingly to reach the status of a full scientific discipline in environmental sciences. A dedicated ISVM society, the International Society for Viruses of Microorganisms, (http://www.isvm.org/) was recently launched. Increasing studies in viral ecology are sources of novel knowledge related to the biodiversity of living things, the functioning of ecosystems, and the evolution of the cellular world. This is because viruses are perhaps the most diverse, abundant, and ubiquitous biological entities in the biosphere, although local environmental conditions enrich for certain viral types through selective pressure. They exhibit various lifestyles that intimately depend on the deep-cellular mechanisms, and are ultimately replicated by members of all three domains of cellular life (Bacteria, Eukarya, Archaea), as well as by giant viruses of some eukaryotic cells. This establishes viral parasites as microbial killers but also as cell partners or metabolic manipulators in microbial ecology. The present chapter sought to review the literature on the diversity and functional roles of viruses of microbes in environmental microbiology, focusing primarily on prokaryotic viruses (i.e., phages) in aquatic ecosystems, which form the bulk of our knowledge in modern environmental viral ecology. PMID:25104950

  7. Environmental bacteriophages: viruses of microbes in aquatic ecosystems.

    PubMed

    Sime-Ngando, Télesphore

    2014-01-01

    Since the discovery 2-3 decades ago that viruses of microbes are abundant in marine ecosystems, viral ecology has grown increasingly to reach the status of a full scientific discipline in environmental sciences. A dedicated ISVM society, the International Society for Viruses of Microorganisms, (http://www.isvm.org/) was recently launched. Increasing studies in viral ecology are sources of novel knowledge related to the biodiversity of living things, the functioning of ecosystems, and the evolution of the cellular world. This is because viruses are perhaps the most diverse, abundant, and ubiquitous biological entities in the biosphere, although local environmental conditions enrich for certain viral types through selective pressure. They exhibit various lifestyles that intimately depend on the deep-cellular mechanisms, and are ultimately replicated by members of all three domains of cellular life (Bacteria, Eukarya, Archaea), as well as by giant viruses of some eukaryotic cells. This establishes viral parasites as microbial killers but also as cell partners or metabolic manipulators in microbial ecology. The present chapter sought to review the literature on the diversity and functional roles of viruses of microbes in environmental microbiology, focusing primarily on prokaryotic viruses (i.e., phages) in aquatic ecosystems, which form the bulk of our knowledge in modern environmental viral ecology. PMID:25104950

  8. Guided Inquiry Learning Unit on Aquatic Ecosystems for Seventh Grade Students

    ERIC Educational Resources Information Center

    To-im, Jongdee; Ruenwongsa, Pintip

    2009-01-01

    Using mini-aquaria experiments, a learning unit on the effects of light period on aquatic ecosystems was developed for 7th grade students. This guided inquiry unit was aimed at helping students understand basic ecological principles involved in relationships among physical, chemical, and biological components in aquatic ecosystems. It involved…

  9. Climate change on arctic environment, ecosystem services and society (CLICHE)

    NASA Astrophysics Data System (ADS)

    Weckström, J.; Korhola, A.; Väliranta, M.; Seppä, H.; Luoto, M.; Tuittila, E.-S.; Leppäranta, M.; Kahilainen, K.; Saarinen, J.; Heikkinen, H.

    2012-04-01

    The predicted climate warming has raised many questions and concerns about its impacts on the environment and society. As a respond to the need of holistic studies comprising both of these areas, The Academy of Finland launched The Finnish Research Programme on Climate Change (FICCA 2011-2014) in spring 2010 with the main aim to focus on the interaction between the environment and society. Ultimately 11 national consortium projects were funded (total budget 12 million EUR). Here we shortly present the main objectives of the largest consortium project "Climate change on arctic environment, ecosystem services and society" (CLICHE). The CLICHE consortium comprises eight interrelated work packages (treeline, diversity, peatlands, snow, lakes, fish, tourism, and traditional livelihoods), each led by a prominent research group and a team leader. The research consortium has three main overall objectives: 1) Investigate, map and model the past, present and future climate change-induced changes in central ecosystems of the European Arctic with unprecedented precision 2) Deepen our understanding of the basic principles of ecosystem and social resilience and dynamics; identify key taxa, structures or processes that clearly indicate impending or realised global change through their loss, occurrence or behaviour, using analogues from the past (e.g. Holocene Thermal Maximum, Medieval Warm Period), experiments, observations and models 3) Develop adaptation and mitigation strategies to minimize the adverse effects of climate change on local communities, traditional livelihoods, fisheries, and tourism industry, and promote sustainable development of local community structures and enhance the quality of life of local human populations. As the project has started only recently no final results are available yet. However, the fieldwork as well as the co-operation between the research teams has thus far been very successful. Thus, the expectations for the final outcome of the project

  10. Selection of candidate aquatic high plants as producer of closed aquatic ecosystem

    NASA Astrophysics Data System (ADS)

    Wang, Gaohong; Hao, Zongjie; Liu, Yongding

    Controlled Ecological Life Support Systems (CELSS) is very important for long-term manned space flight. Aquatic organism was regarded to be suitable for this study because of their great adaptation to the weightless condition which approximate to their wild condition in water. In order to study of operation of CELSS in space, the first step is to choose good candidate species for study. In this report, we compared the characteristics of nutrient content, growth and suitability with animals among five types of aquatic high plants including Ceratophyllum demersum L., Vallisneria spiralis L., Hydrilla verticillata Royle, Brasenia schreberi, Wolfia arrhiza under control condition. It was found that B. schreberi had the best nutrients content, but it growth depended on gas interface which may be a big problem in microgravity. C. demersum and W. arrhiza had the better nutrient content than other types, and V. spiralis and H. verticillata had the worst nutrient content. The closed aquatic system can provided condition for the growth of other plants than B. schreberi. So we selected C. demersum and W. arrhiza as the candidate of producer for establish Closed Aquatic Ecosystem. We also established a simple system& by housing three small freshwater snails (Bulinus australianus) and C. demersum in a 500mL box with light and temperature control. The values about pH, oxygen concentration, temperature and light had been acquired by sensors in real time for about 3 month. It was found that plant's biomass increased for several days and then leveled off and the snails survive, and the atmosphere and biomass for food met snails' requirement during experiments.

  11. Ecological Relationships Between Components in Closed Aquatic Ecosystems

    NASA Astrophysics Data System (ADS)

    Pisman, Tamara; Somova, Lydia

    The work considers the problems of relationships between algae and other microorganisms in aquatic ecosystems. Using small-scale laboratory "autotroph-heterotroph" ecosystems with different types of closure, we showed the results of the investigation into the ecological relation-ships of algae in biocenoses. The autotrophic component was represented by green microalgae, and the heterotrophic component -by yeast and bacteria. An important role in functioning of algobacterial communities is played by 2 -2 (oxygen -carbon dioxide) exchange. The gas exchange between algae and yeast was studied in the "autotroph-heterotroph" gas-closed ecosystem with space-divided components. It was shown that the gas exchange closure of the components into a system prolongs its existence. Hav-ing increased the degree of the system closure by introducing two yeast species with positive metabolic interaction to the heterotrophic component, we observed a significant increase in the gas exchange between the components and thus in the biomass of algae and yeast. The most ancient and ecologically relevant symbioses known in nature are symbiotic associa-tions of algae and heterotrophic organisms. The main symbionts of algae in aquatic ecosystems are bacteria. The cenosis-forming role of algae is based on two characteristics: firstly, their mucous covers and membranes are able to absorb and retain large amounts of water; secondly, many algae evolve various organic substances during their lifetime. An example of algobacterial associations are microalgae Chlorella vulgaris and accompanying microbial flora. Experiments with non-sterile batch culture of algae showed that the increase in the algae biomass was accompanied by the increase in the bacterial biomass. As a result of theoretical and experi-mental investigation into their relationships, it was shown that the largest biomass of bacteria is achieved when using organic substances evolved by algae and having bacteria grow on dead algae; i

  12. Developing Meaningful Measures and Guidelines for Particulates in Aquatic Ecosystems

    NASA Astrophysics Data System (ADS)

    Bilotta, G. S.; Harrison, C.; Joyce, C.; Peacock, C.

    2010-12-01

    Managing global water resources is one of the greatest challenges of the 21st Century. It is a resource that is under growing pressure as global populations rise and the natural supply, in the form of precipitation, is becoming increasingly variable and uncertain with climate change. It is therefore essential that water resources (surface and groundwaters) are managed sustainably in terms of both their quantity and quality. One of the most common causes for the impairment of water quality in surface waters and groundwaters is the presence of particulate matter. Particulate matter, from nano-scale particles and colloids to silt-sized sediments, can have a range of detrimental effects on water resources, from aesthetic issues and higher costs of water treatment, to a decline in the fisheries resource and serious ecological degradation. However at present, there is a poor understanding of the particulate conditions that water quality managers should aim to achieve in order to support good ecological status in different environments. There is also currently a general lack of rigour and standardisation in measurements of particulate matter in aquatic ecosystems, which in turn limits our understanding of the effects of these particles, and importantly, limits our ability to guide effective remediation. This poster describes a research approach that is currently being developed in the UK to address these issues; supporting (1) the development of ecosystem-specific water quality guidelines for particulate matter, and (2) the innovation of more advanced monitoring technologies for particulate matter in aquatic environments. The research project will utilise an established network of 13 reference condition sites (i.e. sites that have minimal anthropogenic disturbance) that contain distinct aquatic communities and are located in contrasting environment types. Hydrological and biological monitoring will be carried-out concurrently with analysis of the physical and geochemical

  13. Changing Arctic ecosystems: resilience of caribou to climatic shifts in the Arctic

    USGS Publications Warehouse

    Gustine, David; Adams, Layne; Whalen, Mary; Pearce, John

    2014-01-01

    The U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative strives to inform key resource management decisions for Arctic Alaska by providing scientific information and forecasts for current and future ecosystem response to a warming climate. Over the past 5 years, a focal area for the USGS CAE initiative has been the North Slope of Alaska. This region has experienced a warming trend over the past 60 years, yet the rate of change has been varied across the North Slope, leading scientists to question the future response and resilience of wildlife populations, such as caribou (Rangifer tarandus), that rely on tundra habitats for forage. Future changes in temperature and precipitation to coastal wet sedge and upland low shrub tundra are expected, with unknown consequences for caribou that rely on these plant communities for food. Understanding how future environmental change may affect caribou migration, nutrition, and reproduction is a focal question being addressed by the USGS CAE research. Results will inform management agencies in Alaska and people that rely on caribou for food.

  14. Hydrological and geochemical response and recovery in disturbed Arctic ecosystems

    SciTech Connect

    Not Available

    1992-01-01

    This progress report is a funding, extension request to continue the database work for the Hydrological and Geochemical Response and Recovery in Disturbed Arctic Ecosystems Program. Throughout the period from 1985 to 1992 the Department of Energy supported research on the hydrology and geochemistry of the headwater basin of Imnavait Creek has focused on the quantification of the input from atmospheric sources of biologically significant and other related chemical variables; the transport of these variables in surface and subsurface flow and their efflux from the basin; and the development of geochemical budgets. The acquisition of multi-year data sets (the longest and most detailed sets in the Arctic) have made it possible to define seasonal ranges and amplitudes; determine spatial and temporal relationships within the different flow compartments; to begin to model the pathways and rates of movement through and across different landscape units. The length of record has also made it possible to examine the quantity and influence of local and extra-regional additions.

  15. The Closed Equilibrated Biological Aquatic System: A 12 months Test of an Artificial Aquatic Ecosystem

    NASA Astrophysics Data System (ADS)

    Blüm, V.; Andriske, M.; Ludwig, Ch.; Paaßen, U.; Voeste, D.

    1999-01-01

    The ``Closed Equilibrated Biological Aquatic System'' (C.E.B.A.S.) is finally disposed for long-term multi-generation experiments with aquatic organisms in a space station. Therefore a minimum operation time of three month is required. It is verified in three versions of laboratory prototypes. The third one passed successfully a 12 months mid-term test in 1995/96 thus demonstrating its high biological stability. The third version of the C.E.B.A.S. consists of a 100 l animal tank, two plant cultivators with a volume of 15 l each with independent illuminations, a 3.0 l semibiological ``mechanical'' filter, a 3.0 l bacteria filter, a heating/cooling device and a dummy filter unit. The live-bearing teleost Xiphophorus helleri is the vertebrate and the pulmonate water snail Biomphalaria glabrata the invertebrate experimental animal in the system. The rootless higher water plant Ceratophyllum demersum is the producer organism. Ammonia oxidizing bacteria and other microorganisms settle in the filters. A simple data acquisition is combined with temperature and plant illumination control. Besides of the space aspects the C.E.B.A.S. proved to be an extremely suitable tool to investigate the organism and subcomponent interactions in a well defined terrestrial aquatic closed ecosystem by providing physical, chemical and biological data which allow an approach to a comprehensive system analysis. Moreover the C.E.B.A.S. is the base for the development of innovative combined animal-plant aquaculture systems for human nutrition on earth which could be implemented into bioregenerative life support systems with a higher degree of complexity suitable for lunar or planetary bases.

  16. Fire and aquatic ecosystems of the western USA: Current knowledge and key questions

    USGS Publications Warehouse

    Bisson, P.A.; Rieman, B.; Luce, C.; Hessburg, Paul F.; Lee, D.; Kershner, J.; Reeves, G.H.; Gresswell, Robert E.

    2003-01-01

    Understanding of the effects of wildland fire and fire management on aquatic and riparian ecosystems is an evolving field, with many questions still to be resolved. Limitations of current knowledge, and the certainty that fire management will continue, underscore the need to summarize available information. Integrating fire and fuels management with aquatic ecosystem conservation begins with recognizing that terrestrial and aquatic ecosystems are linked and dynamic, and that fire can play a critical role in maintaining aquatic ecological diversity. To protect aquatic ecosystems we argue that it will be important to: (1) accommodate fire-related and other ecological processes that maintain aquatic habitats and biodiversity, and not simply control fires or fuels; (2) prioritize projects according to risks and opportunities for fire control and the protection of aquatic ecosystems; and (3) develop new consistency in the management and regulatory process. Ultimately, all natural resource management is uncertain; the role of science is to apply experimental design and hypothesis testing to management applications that affect fire and aquatic ecosystems. Policy-makers and the public will benefit from an expanded appreciation of fire ecology that enables them to implement watershed management projects as experiments with hypothesized outcomes, adequate controls, and replication.

  17. Acid deposition in aquatic ecosystems: Setting limits empirically

    NASA Astrophysics Data System (ADS)

    Newcombe, Charles P.

    1985-07-01

    The problem of acid deposition and its harmful effects on aquatic ecosystems has created a new branch of science that is called upon to provide the knowledge on which legislative controls can be based. However, because of the nature of existing legislation, which requires evidence of cause and effect between industrial emissions and pollution, and because of science's inability to provide this information over the short term, considerable controversy has arisen about whether sufficient information exists to warrant control measures at this time. Among those who advocate controls, there is genuine divergence of opinion about how stringent the controls must be to achieve any desired level of protection. The controversy has led to an impasse between the scientific and political participants, which is reflected in the slow pace of progress toward an effective management strategy. Resolution of the impasse, at least in the short term, may demand that science and politics rely on empirical models rather than explanatory ones. The empirical model, which is the major proposal in this article, integrates all of the major variables and many of the minor ones, and constructs a three-dimensionally curved surface capable of representing the status of any waterbody subjected to the effects of acid deposition. When suitably calibrated—a process involving the integration of knowledge and data from aquatic biology, geochemistry, meteorology, and limnology—it can be used to depict limits to the rate of acid deposition required for any level of environmental protection. Because it can generate a pictorial display of the effects of management decisions and legislative controls, the model might serve as a basis for enhancing the quality of communication among all the scientific and political participants and help to resolve many of their controversies.

  18. Responses of arctic and alpine ecosystems to altered seasonality under climate change

    NASA Astrophysics Data System (ADS)

    Ernakovich, J. G.; Hopping, K. A.; Berdanier, A.; Simpson, R. T.; Kachergis, E. J.; Steltzer, H.; Wallenstein, M. D.

    2012-12-01

    Arctic and alpine ecosystems are largely structured by strong seasonal patterns in abiotic drivers, including solar radiation and air and soil temperature. Because air temperature and precipitation patterns are changing rapidly, the length of the growing season is increasing due to shifts in snowfall, earlier snowmelt in spring, and delayed snowfall in autumn. Although arctic and alpine environments are both characterized by short growing seasons, they differ in fundamental ways that will affect their responses to changing seasonality. We compare meteorological data from sixteen arctic and alpine sites and biological data from two arctic and two alpine sites. We propose that although alpine and arctic ecosystems appear similar under historical climate conditions, especially during the growing season, winter conditions and climate change will result in divergent responses. Biotic responses to changing seasonality will affect belowground and aboveground community composition, trophic dynamics, and the functioning of these ecosystems, including net carbon balance.

  19. Monitoring ecosystem dynamics in an Arctic tundra ecosystem using hyperspectral reflectance and a robotic tram system

    NASA Astrophysics Data System (ADS)

    Goswami, Santonu

    Global change, which includes climate change and the impacts of human disturbance, is altering the provision and sustainability of ecosystem goods and services. These changes have the capacity to initiate cascading affects and complex feedbacks through physical, biological and human subsystems and interactions between them. Understanding the future state of the earth system requires improved knowledge of ecosystem dynamics and long term observations of how these are being impacted by global change. Improving remote sensing methods is essential for such advancement because satellite remote sensing is the only means by which landscape to continental-scale change can be observed. The Arctic appears to be impacted by climate change more than any other region on Earth. Arctic terrestrial ecosystems comprise only 6% of the land surface area on Earth yet contain an estimated 25% of global soil organic carbon, most of which is stored in permafrost. If projected increases in plant productivity do not offset forecast losses of soil carbon to the atmosphere as greenhouse gases, regional to global greenhouse warming could be enhanced. Soil moisture is an important control of land-atmosphere carbon exchange in arctic terrestrial ecosystems. However, few studies to date have examined using remote sensing, or developed remote sensing methods for observing the complex interplay between soil moisture and plant phenology and productivity in arctic landscapes. This study was motivated by this knowledge gap and addressed the following questions as a contribution to a large scale, multi investigator flooding and draining experiment funded by the National Science Foundation near Barrow, Alaska (71°17'01" N, 156°35'48" W): (1) How can optical remote sensing be used to monitor the surface hydrology of arctic landscapes? (2) What are the spatio-temporal dynamics of land-surface phenology (NDVI) in the study area and do hydrological treatment has any effect on inter-annual patterns? (3

  20. Nutrient sources and transport along urban flowpaths to aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Finlay, J. C.; Janke, B.; Baker, L. A.; Hobbie, S. E.; Nidzgorski, D.; Sterner, R.; Wilson, B. N.

    2012-12-01

    Water quality of urban freshwater ecosystems is widely impaired by eutrophication, with little recent improvement and much potential for further degradation due to urban expansion and intensification. Despite the degradation of water quality in urban streams and lakes and adjacent coastal areas, relatively little is known about the relative importance of specific nutrient sources and the processes that regulate their movement across highly modified land-water interfaces. To better understand the nutrient sources and cycling that affect aquatic ecosystems, we assess nutrient movement through urban drainage networks in St. Paul, Minnesota. Nutrient concentrations and flux in stormwater at six intensively monitored sites show consistent seasonal patterns, with peaks in total nitrogen (N) and phosphorus (P) in the late spring. Trees contributed to nutrient movement via litterfall and throughfall to impervious surfaces, with peaks in inputs that corresponded to stormwater nutrient patterns. Despite runoff generated primarily from impervious surfaces, organic carbon and nitrogen concentrations were high, with organic N accounting for >80% of stormwater N loading. Together, these data suggested an important role for urban tree canopies in nutrient mobilization in stormwater. Base flow, present in larger storm drains and buried streams, results primarily from groundwater seepage and from outflow of surface water connected to drains. Base flow contributed significantly to nutrient export, particularly for N (33 to 68% of warm season export) but also for P (8 to 34%). Sites with upstream hydrologic connections to lakes and remnant above-ground stream reaches had higher baseflow organic carbon and P, and reduced N concentrations compared to sites dominated by groundwater. Together, these data show that the characteristics of urban vegetation and the nature of human alterations to hydrologic connections are dominant features influencing the form and amount of nutrient movement

  1. Aquatic Ecosystem Enhancement at Mountaintop Mining Sites Symposium

    SciTech Connect

    Black, D. Courtney; Lawson, Peter; Morgan, John; Maggard, Randy; Schor, Horst; Powell, Rocky; Kirk, Ed. J.

    2000-01-12

    Welcome to this symposium which is part of the ongoing effort to prepare an Environmental Impact Statement (EIS) regarding mountaintop mining and valley fills. The EIS is being prepared by the U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, U.S. Office of Surface Mining, and U.S. Fish and Wildlife Service, in cooperation with the State of West Virginia. Aquatic Ecosystem Enhancement (AEE) at mountaintop mining sites is one of fourteen technical areas identified for study by the EIS Interagency Steering Committee. Three goals were identified in the AEE Work Plan: 1. Assess mining and reclamation practices to show how mining operations might be carried out in a way that minimizes adverse impacts to streams and other environmental resources and to local communities. Clarify economic and technical constraints and benefits. 2. Help citizens clarify choices by showing whether there are affordable ways to enhance existing mining, reclamation, mitigation processes and/or procedures. 3. Ide identify data needed to improve environmental evaluation and design of mining projects to protect the environment. Today’s symposium was proposed in the AEE Team Work Plans but coordinated planning for the event began September 15, 1999 when representatives from coal industry, environmental groups and government regulators met in Morgantown. The meeting participants worked with a facilitator from the Canaan Valley Institute to outline plans for the symposium. Several teams were formed to carry out the plans we outlined in the meeting.

  2. Performance of a simple closed aquatic ecosystem (CAES) in space

    NASA Astrophysics Data System (ADS)

    Wang, G.-H.; Li, G.-B.; Hu, C.-X.; Liu, Y.-D.; Song, L.-R.; Tong, G.-H.; Liu, X.-M.; Cheng, E.-T.

    2004-01-01

    A simple Closed Aquatic Ecosystem (CAES) consisting of single-celled green algae ( Chlorella pyrenoidosa, producer), a spiral snail ( Bulinus australianus, consumer) and a data acquisition and control unit was flown on the Chinese Spacecraft SHENZHOU-II in January 2001 for 7 days. In order to study the effect of microgravity on the operation of CAES, a 1 g centrifuge reference group in space, a ground 1 g reference group and a ground 1 g centrifuge reference group (1.4 g group) were run concurrently. Real-time data about algae biomass (calculated from transmission light intensity), temperature, light and centrifugation of the CAES were logged at minute intervals. It was found that algae biomass of both the microgravity group and the ground 1 g centrifuge reference group (1.4 g) fluctuated during the experiment, but the algae biomass of the 1 g centrifuge reference group in space and the ground 1 g reference group increased during the experiment. The results may be attributable to influences of microgravity and 1.4 g gravity on the algae and snails metabolisms. Microgravity is the main factor to affect the operation of CAES in space and the contribution of microgravity to the effect was also estimated. These data may be valuable for the establishment of a complex CELSS in the future.

  3. Effects of solar UV-B radiation on aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Häder, D.-P.

    Solar UV degrades dissolved organic carbon photolytically so that they can readily be taken up by bacterioplankton. On the other hand solar UV radiation inhibits bacterioplankton activity. Bacterioplankton productivity is far greater than previously thought and is comparable to phytoplankton primary productivity. According to the "microbial loop hypothesis," bacterioplankton is seen in the center of a food web, having a similar function to phytoplankton and protists. The penetration of UV and PAR into the water column can be measured. Marine waters show large temporal and regional differences in their concentrations of dissolved and particulate absorbing substances. A network of dosimeters (ELDONET) has been installed in Europe ranging from Abisko in Northern Sweden to Gran Canaria. Cyanobacteria are capable of fixing atmospheric nitrogen which is then made available to higher plants. The agricultural potential of cyanobacteria has been recognized as a biological fertilizer for wet soils such as in rice paddies. UV-B is known to impair processes such as growth, survival, pigmentation, motility, as well as the enzymes of nitrogen metabolism and CO 2 fixation. The marine phytoplankton represents the single most important ecosystem on our planet and produces about the same biomass as all terrestrial ecosystems taken together. It is the base of the aquatic food chain and any changes in the size and composition of phytoplankton communities will directly affect food production for humans from marine sources. Another important role of marine phytoplankton is to serve as a sink for atmospheric carbon dioxide. Recent investigations have shown a large sensitivity of most phytoplankton organisms toward solar short-wavelength ultraviolet radiation (UV-B); even at ambient levels of UV-B radiation many organisms seem to be under UV stress. Because of their requirement for solar energy, the phytoplankton dwell in the top layers of the water column. In this near-surface position

  4. Effects of solar UV-B radiation on aquatic ecosystems.

    PubMed

    Hader, D P

    2000-01-01

    Solar UV degrades dissolved organic carbon photolytically so that they can readily be taken up by bacterioplankton. On the other hand solar UV radiation inhibits bacterioplankton activity. Bacterioplankton productivity is far greater than previously thought and is comparable to phytoplankton primary productivity. According to the "microbial loop hypothesis," bacterioplankton is seen in the center of a food web, having a similar function to phytoplankton and protists. The penetration of UV and PAR into the water column can be measured. Marine waters show large temporal and regional differences in their concentrations of dissolved and particulate absorbing substances. A network of dosimeters (ELDONET) has been installed in Europe ranging from Abisko in Northern Sweden to Gran Canaria. Cyanobacteria are capable of fixing atmospheric nitrogen which is then made available to higher plants. The agricultural potential of cyanobacteria has been recognized as a biological fertilizer for wet soils such as in rice paddies. UV-B is known to impair processes such as growth, survival, pigmentation, motility, as well as the enzymes of nitrogen metabolism and CO2 fixation. The marine phytoplankton represents the single most important ecosystem on our planet and produces about the same biomass as all terrestrial ecosystems taken together. It is the base of the aquatic food chain and any changes in the size and composition of phytoplankton communities will directly affect food production for humans from marine sources. Another important role of marine phytoplankton is to serve as a sink for atmospheric carbon dioxide. Recent investigations have shown a large sensitivity of most phytoplankton organisms toward solar short-wavelength ultraviolet radiation (UV-B); even at ambient levels of UV-B radiation many organisms seem to be under UV stress. Because of their requirement for solar energy, the phytoplankton dwell in the top layers of the water column. In this near-surface position

  5. Determining the Effectiveness of Aquatic Ecosystem Restoration, Conservation, and Management Practices.

    EPA Science Inventory

    The science of aquatic ecosystem restoration and management is still in its infancy, largely because most projects are inadequately tracked and monitored for assessing their success. Historically, evaluating the effectiveness of best management practices (BMPs) has relied heavily...

  6. UV EFFECTS ON MARINE AND AQUATIC ECOSYSTEMS. IN: PHOTOBIOLOGY FOR THE 21ST CENTURY.

    EPA Science Inventory

    Authors present a review of the literature dealing with UV effects on marine and aquatic ecosystems. Topic headings include Direct Effects, Interactive Effects, Indirect Effects, Response Variability, and The Future.

  7. CONCEPTUAL MODELS AND METHODS TO GUIDE DIAGNOSTIC RESEARCH INTO CAUSES OF IMPAIRMENT TO AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Methods and conceptual models to guide the development of tools for diagnosing the causes of biological impairment within aquatic ecosystems of the United States are described in this report. The conceptual models developed here address nutrients, suspended and bedded sediments (...

  8. Geologic sources of nutrients for aquatic ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    Dahlgren, R. A.; Jeffres, C.; Nichols, A. L.; Deas, M.; Willis, A.; Mount, J.

    2010-12-01

    Nutrient inputs from geologic materials are not typically considered an ecologically significant source of nutrients for freshwater aquatic ecosystems. However, in volcanic terrains where regional groundwater interacts with volcanic and underlying sedimentary deposits, nutrients (nitrogen and phosphorus) from geologic sources can provide ecologically significant inputs of nutrients to fuel aquatic food webs. The Big Springs-Shasta River complex emanating from the flanks of Mt. Shasta, a stratovolcano in northern California, creates a unique ecological niche that we propose as the explanation for the exceptionally high historical abundances and productivity of salmonids in the Shasta River. The Big Springs complex is a slightly-thermal springs (natural flow of 2.6 m3/s) that is the primary source of water for the Shasta River. The spring waters have a mean recharge elevation of 2880 m on Mt. Shasta. During the 20-50 years of transport as groundwater, both nitrogen and phosphorus are released from the underlying marine sedimentary and volcanic rocks. Mean NO3-N and soluble-reactive PO4-P concentrations over a two year period were 0.48 mg/L and 0.15 mg/L, respectively. The PO4 concentrations are in equilibrium with hydroxyapatite (Ca2OHPO4) suggesting that release of PO4 by chemical weathering of the highly weatherable volcanic deposits is the primary source of the PO4. The primary source of nitrogen is from detrital organic matter incorporated in the marine sedimentary rocks during diagensis. This “geologic” nitrogen is released from rocks by hydrothermal waters and transported with the groundwater. The nitrogen and phosphorus coupled with year round consistent water flow volumes and thermal buffering (10-12o C) fuel primary productivity and enhance food web productivity. Abundant nutrients allow for high rates of primary productivity, providing food for invertebrates, which ultimately comprise the primary food source for salmonids. These volcanic-derived, spring

  9. Concentrated standing tailwater: a mechanism for nutrient delivery to downstream aquatic ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Contribution of first flush runoff events from intense rainfall to downstream aquatic ecosystems are often reported in terms of sediment and nutrient delivery, with hardly any consideration to the contribution that standing, concentrated tailwater in primary aquatic systems makes to downstream nutri...

  10. MICROBIAL INDICATORS OF AQUATIC ECOSYSTEM CHANGE: CURRENT APPLICATIONS TO EUTROPHICATION STUDIES. (R828677C001)

    EPA Science Inventory

    Human encroachment on aquatic ecosystems is increasing at an unprecedented rate. The impacts of human pollution and habitat alteration are most evident and of greatest concern at the microbial level, where a bulk of production and nutrient cycling takes place. Aquatic ecosyste...

  11. Biogeochemistry and nitrogen cycling in an Arctic, volcanic ecosystem

    NASA Astrophysics Data System (ADS)

    Fogel, M. L.; Benning, L.; Conrad, P. G.; Eigenbrode, J.; Starke, V.

    2007-12-01

    As part of a study on Mars Analogue environments, the biogeochemistry of Sverrefjellet Volcano, Bocfjorden, Svalbard, was conducted and compared to surrounding glacial, thermal spring, and sedimentary environments. An understanding of how nitrogen might be distributed in a landscape that had extinct or very cold adapted, slow- growing extant organisms should be useful for detecting unknown life forms. From high elevations (900 m) to the base of the volcano (sea level), soil and rock ammonium concentrations were uniformly low, typically less than 1- 3 micrograms per gm of rock or soil. In weathered volcanic soils, reduced nitrogen concentrations were higher, and oxidized nitrogen concentrations lower. The opposite was found in a weathered Devonian sedimentary soil. Plants and lichens growing on volcanic soils have an unusually wide range in N isotopic compositions from -5 to +12‰, a range rarely measured in temperate ecosystems. Nitrogen contents and isotopic compositions of volcanic soils and rocks were strongly influenced by the presence or absence of terrestrial herbivores or marine avifauna with higher concentrations of N and elevated N isotopic compositions occurring as patches in areas immediately influenced by reindeer, Arctic fox ( Alopex lagopus), and marine birds. Because of the extreme conditions in this area, ephemeral deposition of herbivore feces results in a direct and immediate N pulses into the ecosystem. The lateral extent and distribution of marine- derived nitrogen was measured on a landscape scale surrounding an active fox den. Nitrogen was tracked from the bones of marine birds to soil to vegetation. Because of extreme cold, slow biological rates and nitrogen cycling, a mosaic of N patterns develops on the landscape scale.

  12. Changing Arctic ecosystems--the role of ecosystem changes across the Boreal-Arctic transition zone on the distribution and abundance of wildlife populations

    USGS Publications Warehouse

    McNew, Lance; Handel, Colleen; Pearce, John; DeGange, Anthony R.; Holland-Bartels, Leslie; Whalen, Mary

    2013-01-01

    Arctic and boreal ecosystems provide important breeding habitat for more than half of North America’s migratory birds as well as many resident species. Northern landscapes are projected to experience more pronounced climate-related changes in habitat than most other regions. These changes include increases in shrub growth, conversion of tundra to forest, alteration of wetlands, shifts in species’ composition, and changes in the frequency and scale of fires and insect outbreaks. Changing habitat conditions, in turn, may have significant effects on the distribution and abundance of wildlife in these critical northern ecosystems. The U.S. Geological Survey (USGS) is conducting studies in the Boreal–Arctic transition zone of Alaska, an environment of accelerated change in this sensitive margin between Arctic tundra and boreal forest.

  13. Soil Biota and Litter Decay in High Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    González, G.; Rivera, F.; Makarova, O.; Gould, W. A.

    2006-12-01

    Frost heave action contributes to the formation of non-sorted circles in the High Arctic. Non-sorted circles tend to heave more than the surrounding tundra due to deeper thaw and the formation of ice lenses. Thus, the geomorphology, soils and vegetation on the centers of the patterned-ground feature (non-sorted circles) as compared to the surrounding soils (inter-circles) can be different. We established a decomposition experiment to look at in situ decay rates of the most dominant graminoid species on non-sorted circles and adjacent inter-circle soils along a climatic gradient in the Canadian High Arctic as a component of a larger study looking at the biocomplexity of small-featured patterned ground ecosystems. Additionally, we investigated variation in soil chemical properties and biota, including soil microarthropods and microbial composition and biomass, as they relate to climate, topographic position, and litter decay rates. Our three sites locations, from coldest to warmest, are Isachsen, Ellef Ringnes Island (ER), NU (bioclimatic subzone A); Mould Bay (MB), Prince Patrick Island, NT (bioclimatic subzone B), and Green Cabin (GC), Aulavik National Park, Thomsen River, Banks Island, NT (bioclimatic subzone C). Our sample design included the selection of 15 non-sorted circles and adjacent inter-circle areas within the zonal vegetation at each site (a total of 90 sites), and a second set of 3 non-sorted circles and adjacent inter-circle areas in dry, mesic and wet tundra at each of the sites. Soil invertebrates were sampled at each site using both pitfall traps, soil microbial biomass was determined using substrate induced respiration and bacterial populations were determined using the most probable number method. Decomposition rates were measured using litterbags and as the percent of mass remaining of Carex misandra, Luzula nivalis and Alopecuris alpinus in GC, MB and ER, respectively. Our findings indicate these graminoid species decayed significantly over

  14. Influence of the Tussock Growth Form on Arctic Ecosystem Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Curasi, S.; Rocha, A. V.; Sonnentag, O.; Wullschleger, S. D.; Myers-Smith, I. H.; Fetcher, N.; Mack, M. C.; Natali, S.; Loranty, M. M.; Parker, T.

    2015-12-01

    The influence of plant growth forms on ecosystem carbon (C) cycling has been under appreciated. In arctic tundra, environmental factors and plant traits of the sedge Eriophorum vaginatum cause the formation of mounds that are dense amalgamations of belowground C called tussocks. Tussocks have important implications for arctic ecosystem biogeochemistry and C stocks, but the environmental and biological factors controlling their size and distribution across the landscape are poorly understood. In order to better understand how landscape variation in tussock size and density impact ecosystem C stocks, we formed the Carbon in Arctic Tussock Tundra (CATT) network and recruited an international team to sample locations across the arctic. The CATT network provided a latitudinal and longitudinal gradient along which to improve our understanding of tussocks' influence on ecosystem structure and function. CATT data revealed important insights into tussock formation across the arctic. Tussock density generally declined with latitude, and tussock size exhibited substantial variation across sites. The relationship between height and diameter was similar across CATT sites indicating that both biological and environmental factors control tussock formation. At some sites, C in tussocks comprised a substantial percentage of ecosystem C stocks that may be vulnerable to climate change. It is concluded that the loss of this growth form would offset C gains from projected plant functional shifts from graminoid to shrub tundra. This work highlights the role of plant growth forms on the magnitude and retention of ecosystem C stocks.

  15. 75 FR 18499 - The Effects of Mountaintop Mines and Valley Fills on Aquatic Ecosystems of the Central...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-12

    ... Coalfields and a Field-Based Aquatic Life Benchmark for Conductivity in Central Appalachian Streams AGENCY...) ``A Field-based Aquatic Life Benchmark for Conductivity in Central Appalachian Streams'' (EPA/600/R... Fills on Aquatic Ecosystems of the Central Appalachian Coalfields'' and ``A Field-based Aquatic...

  16. Turbulence and Fluid Flow: Perspectives. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Simpson, James R.

    This module is part of a series on Physical Processes in Terrestrial and Aquatic Ecosystems. The materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process.…

  17. Biological Production in Lakes. Physical Processes in Terrestrial and Aquatic Ecosystems, Ecological Processes.

    ERIC Educational Resources Information Center

    Walters, R. A.; Carey, G. F.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. Primary production in aquatic ecosystems is carried out by phytoplankton, microscopic plants…

  18. Stimulation of microbial nitrogen cycling in aquatic ecosystems by benthic macrofauna: mechanisms and environmental implications

    NASA Astrophysics Data System (ADS)

    Stief, P.

    2013-12-01

    Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal-microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal-microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments is enhanced more strongly than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies reveal that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification-denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and

  19. Stimulation of microbial nitrogen cycling in aquatic ecosystems by benthic macrofauna: mechanisms and environmental implications

    NASA Astrophysics Data System (ADS)

    Stief, P.

    2013-07-01

    Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal-microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal-microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments often is enhanced even more than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies revealed that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification-denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover

  20. Critical review of mercury fates and contamination in the Arctic tundra ecosystem.

    PubMed

    Poissant, Laurier; Zhang, Hong H; Canário, João; Constant, Philippe

    2008-08-01

    Mercury (Hg) contamination in tundra region has raised substantial concerns, especially since the first report of atmospheric mercury depletion events (AMDEs) in the Polar Regions. During the past decade, steady progress has been made in the research of Hg cycling in the Polar Regions. This has generated a unique opportunity to survey the whole Arctic in respect to Hg issue and to find out new discoveries. However, there are still considerable knowledge gaps and debates on the fate of Hg in the Arctic and Antarctica, especially regarding the importance and significance of AMDEs vs. net Hg loadings and other processes that burden Hg in the Arctic. Some studies argued that climate warming since the last century has exerted profound effects on the limnology of High Arctic lakes, including substantial increases in autochthonous primary productivity which increased in sedimentary Hg, whereas some others pointed out the importance of the formation and postdeposition crystallographic history of the snow and ice crystals in determining the fate and concentration of mercury in the cryosphere in addition to AMDEs. Is mercury re-emitted back to the atmosphere after AMDEs? Is Hg methylation effective in the Arctic tundra? Where the sources of MeHg are? What is its fate? Is this stimulated by human made? This paper presents a critical review about the fate of Hg in the Arctic tundra, such as pathways and process of Hg delivery into the Arctic ecosystem; Hg concentrations in freshwater and marine ecosystems; Hg concentrations in terrestrial biota; trophic transfer of Hg and bioaccumulation of Hg through food chain. This critical review of mercury fates and contamination in the Arctic tundra ecosystem is assessing the impacts and potential risks of Hg contamination on the health of Arctic people and the global northern environment by highlighting and "perspectiving" the various mercury processes and concentrations found in the Arctic tundra. PMID:18707754

  1. Lowering the Barriers to Integrative Aquatic Ecosystem Science: Semantic Provenance, Open Linked Data, and Workflows

    NASA Astrophysics Data System (ADS)

    Harmon, T.; Hofmann, A. F.; Utz, R.; Deelman, E.; Hanson, P. C.; Szekely, P.; Villamizar, S. R.; Knoblock, C.; Guo, Q.; Crichton, D. J.; McCann, M. P.; Gil, Y.

    2011-12-01

    Environmental cyber-observatory (ECO) planning and implementation has been ongoing for more than a decade now, and several major efforts have recently come online or will soon. Some investigators in the relevant research communities will use ECO data, traditionally by developing their own client-side services to acquire data and then manually create custom tools to integrate and analyze it. However, a significant portion of the aquatic ecosystem science community will need more custom services to manage locally collected data. The latter group represents enormous intellectual capacity when one envisions thousands of ecosystems scientists supplementing ECO baseline data by sharing their own locally intensive observational efforts. This poster summarizes the outcomes of the June 2011 Workshop for Aquatic Ecosystem Sustainability (WAES) which focused on the needs of aquatic ecosystem research on inland waters and oceans. Here we advocate new approaches to support scientists to model, integrate, and analyze data based on: 1) a new breed of software tools in which semantic provenance is automatically created and used by the system, 2) the use of open standards based on RDF and Linked Data Principles to facilitate sharing of data and provenance annotations, 3) the use of workflows to represent explicitly all data preparation, integration, and processing steps in a way that is automatically repeatable. Aquatic ecosystems workflow exemplars are provided and discussed in terms of their potential broaden data sharing, analysis and synthesis thereby increasing the impact of aquatic ecosystem research.

  2. Development of scientific tools for monitoring the health of aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Caldararu, Aurelia; Voiculescu, Mirela; Georgescu, Lucian P.

    2010-05-01

    Humanity is faced nowadays with the major problem of water availability and quality which is a conseqquence of growing demand for water as well as the decline of water quality and quantity. It is not an exaggeration to claim that, without effective management of aquatic ecosystems, the future social and economic development of the world will suffer serious constraints or will be placed significantly at risk. Taking into consideration the fact that the world is rapidly changing, current practices of water management must also change. Developed and developing countries will have to adopt the most effective policies for the management of aquatic ecosystems. They will also have to start using the best techniques for water monitoring. The nature of future problems that could arise in aquatic ecosystems must be carefully anticipated and then objectively analysed in the light of the expected changes. The Water Framework Directive (WFD) requires a holistic knowledge of abiotic and biotic structure and processes that determine the functioning of aquatic ecosystems. Ecological indicators are provided to monitor the ecosystem responses to anthropogenic pressures. We will summarize in this presentation ecological indices that can be used for effective and accurate monitoring of aquatic ecosystems. Different contexts where these indices can be used for environmental health monitoring will be also analysed.

  3. A source of terrestrial organic carbon to investigate the browning of aquatic ecosystems.

    PubMed

    Lennon, Jay T; Hamilton, Stephen K; Muscarella, Mario E; Grandy, A Stuart; Wickings, Kyle; Jones, Stuart E

    2013-01-01

    There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago. This "browning" phenomenon will alter the chemistry, physics, and biology of inland water bodies in complex and difficult-to-predict ways. Experiments provide an opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems. However, it is challenging to obtain sources of DOC that can be used for manipulations at ecologically relevant scales. In this study, we evaluated a commercially available source of humic substances ("Super Hume") as an analog for natural sources of terrestrial DOC. Based on chemical characterizations, comparative surveys, and whole-ecosystem manipulations, we found that the physical and chemical properties of Super Hume are similar to those of natural DOC in aquatic and terrestrial ecosystems. For example, Super Hume attenuated solar radiation in ways that will not only influence the physiology of aquatic taxa but also the metabolism of entire ecosystems. Based on its chemical properties (high lignin content, high quinone content, and low C:N and C:P ratios), Super Hume is a fairly recalcitrant, low-quality resource for aquatic consumers. Nevertheless, we demonstrate that Super Hume can subsidize aquatic food webs through 1) the uptake of dissolved organic constituents by microorganisms, and 2) the consumption of particulate fractions by larger organisms (i.e., Daphnia). After discussing some of the caveats of Super Hume, we conclude that commercial sources of humic substances can be used to help address pressing ecological questions concerning the increased export of terrestrial DOC to aquatic ecosystems. PMID:24124511

  4. A Source of Terrestrial Organic Carbon to Investigate the Browning of Aquatic Ecosystems

    PubMed Central

    Lennon, Jay T.; Hamilton, Stephen K.; Muscarella, Mario E.; Grandy, A. Stuart; Wickings, Kyle; Jones, Stuart E.

    2013-01-01

    There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago. This “browning” phenomenon will alter the chemistry, physics, and biology of inland water bodies in complex and difficult-to-predict ways. Experiments provide an opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems. However, it is challenging to obtain sources of DOC that can be used for manipulations at ecologically relevant scales. In this study, we evaluated a commercially available source of humic substances (“Super Hume”) as an analog for natural sources of terrestrial DOC. Based on chemical characterizations, comparative surveys, and whole-ecosystem manipulations, we found that the physical and chemical properties of Super Hume are similar to those of natural DOC in aquatic and terrestrial ecosystems. For example, Super Hume attenuated solar radiation in ways that will not only influence the physiology of aquatic taxa but also the metabolism of entire ecosystems. Based on its chemical properties (high lignin content, high quinone content, and low C:N and C:P ratios), Super Hume is a fairly recalcitrant, low-quality resource for aquatic consumers. Nevertheless, we demonstrate that Super Hume can subsidize aquatic food webs through 1) the uptake of dissolved organic constituents by microorganisms, and 2) the consumption of particulate fractions by larger organisms (i.e., Daphnia). After discussing some of the caveats of Super Hume, we conclude that commercial sources of humic substances can be used to help address pressing ecological questions concerning the increased export of terrestrial DOC to aquatic ecosystems. PMID:24124511

  5. NON-TRADITIONAL RESPONSES TO PHARMACEUTICALS IN AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Quantitation of human and veterinary pharmaceuticals in environmental matrices has resulted in pharmaceuticals in the environment receiving unprecedented attention from the scientific community. Aquatic hazard assessments often use quantitative structure activity relationships an...

  6. Changing Arctic ecosystems: sea ice decline, permafrost thaw, and benefits for geese

    USGS Publications Warehouse

    Flint, Paul; Whalen, Mary; Pearce, John M.

    2014-01-01

    Through the Changing Arctic Ecosystems (CAE) initiative, the U.S. Geological Survey (USGS) strives to inform resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a warming climate. A key area for the USGS CAE initiative has been the Arctic Coastal Plain of northern Alaska. This region has experienced a warming trend over the past 30 years, leading to reductions in sea ice and thawing of permafrost. Loss of sea ice has increased ocean wave action, leading to erosion and salt water inundation of coastal habitats. Saltwater tolerant plants are now thriving in these areas and this appears to be a positive outcome for geese in the Arctic. This finding is contrary to the deleterious effects that declining sea ice is having on habitats of ice-dependent animals, such as polar bear and walrus.

  7. Simulating net ecosystem productivity and the sensitivity of a sub-arctic boreal forest ecosystem

    NASA Astrophysics Data System (ADS)

    Ueyama, M.; Harazono, Y.; Kim, Y.; Tanaka, N.

    2005-12-01

    BIOME-BGC was used to examine how air temperature and precipitation affect NEP in a sub-arctic black spruce forest. The model was tuned using data from the eddy correlation measurement site in UAF black spruce forest during 2003 and 2004. The climate dataset of Fairbanks airport between 1949 and 2004 was used for the model spin-up. The model almost reproduced the observed NEE, in which climate in 2003 was normal and that in 2004 was drought in summer. The model, however, failed to simulate the late winter NEE, during which obvious daytime uptake were observed under extreme low temperature. Annual simulation of GPP and ecosystem respiration was 2.2 and 1.8 kg CO2 m-2 yr-1 in 2003 and 2.4 and 1.9 kg CO2 m-2 yr-1 in 2004. While warm growing season temperature enhanced the photosynthesis and respiration in 2004, significant drought in August 2004 were restricted both the photosynthesis and heterotrophic respiration. Simulated annual NEE was 0.2 kg CO2 m-2 yr-1 in 2003 and 0.3 kg CO2 m-2 yr-1 in 2004. The simulation explored the impact of seasonal warmer (+5oC), wetter (120% of precipitation) and drier (80% of precipitation) spells on net ecosystem productivity, comparing the long term Fairbanks weather between 1980 and 2000. Wetter condition in either season did not significantly affect annual NEP. While drought summer decreased annual NEP by 30% mainly due to reduction in GPP by 9%, low snowfall winter also reduced the annual NEP by 19%, in which low snow water brought drought stress in following summer and then suppressed both GPP to 93% and ecosystem respiration to 96%. Warmer summer and autumn decreased annual NEP to 37% and 65%. In this case, GPP did not increase and maintenance and heterotrophic respiration were enhanced to 120% and 126%, respectively, in warmer summer and 103% and 107%, respectively, in warmer autumn. The simulation unambiguously showed productivity of the sub-arctic boreal forest was significantly sensitive to warmer temperature in summer and

  8. Cyanotoxins in arctic lakes of southwestern Greenland and the potential for toxin transfer within-lake and across the aquatic-terrestrial boundary

    NASA Astrophysics Data System (ADS)

    Trout-Haney, J. V.; Cottingham, K. L.

    2015-12-01

    Arctic lakes are often characterized as low-resource environments in which the autotrophic community is limited by factors such as nutrients, temperature, and light. Studies of cyanotoxins have traditionally focused on nutrient-rich lakes with conspicuous blooms, however toxigenic cyanobacteria are confined to neither high nutrient environments nor planktonic taxa. We quantified the occurrence of cyanotoxins across 19 arctic lakes of varying size and depth in the Kangerlussuaq region of southwestern Greenland. Whole lake water microcystins (MC) were detected in all lakes and ranged from low (<5 ng/L) to moderate (>100 ng/L) concentrations. Benthic colonial cyanobacteria of the genus Nostoc are a prominent feature of certain lakes in this region, with estimated densities ranging between 500 and >500,000 colonies per lake. MC were present in the tissue of Nostoc colonies (95% CI, 1638.9 - 3237.6 pg MC (g wet weight)-1) and were actively released by colonies into surrounding water in laboratory trials. These results highlight the potential importance of toxic benthic cyanobacteria in lake ecosystems. Further, we investigated the transfer of these cyanotoxins to other organisms in the lake as well as several mechanisms (i.e., emerging insects, aerosols) that may influence the movement of toxins into the terrestrial ecosystem. The presence and movement of cyanotoxins in the coupled terrestrial-aquatic ecosystem demonstrate that high-latitude lakes can support toxigenic cyanobacteria, and that we may be underestimating the potential for these systems to develop high levels of toxicity in the future.

  9. Rough-legged buzzards, Arctic foxes and red foxes in a tundra ecosystem without rodents.

    PubMed

    Pokrovsky, Ivan; Ehrich, Dorothée; Ims, Rolf A; Kondratyev, Alexander V; Kruckenberg, Helmut; Kulikova, Olga; Mihnevich, Julia; Pokrovskaya, Liya; Shienok, Alexander

    2015-01-01

    Small rodents with multi-annual population cycles strongly influence the dynamics of food webs, and in particular predator-prey interactions, across most of the tundra biome. Rodents are however absent from some arctic islands, and studies on performance of arctic predators under such circumstances may be very instructive since rodent cycles have been predicted to collapse in a warming Arctic. Here we document for the first time how three normally rodent-dependent predator species-rough-legged buzzard, arctic fox and red fox - perform in a low-arctic ecosystem with no rodents. During six years (in 2006-2008 and 2011-2013) we studied diet and breeding performance of these predators in the rodent-free Kolguev Island in Arctic Russia. The rough-legged buzzards, previously known to be a small rodent specialist, have only during the last two decades become established on Kolguev Island. The buzzards successfully breed on the island at stable low density, but with high productivity based on goslings and willow ptarmigan as their main prey - altogether representing a novel ecological situation for this species. Breeding density of arctic fox varied from year to year, but with stable productivity based on mainly geese as prey. The density dynamic of the arctic fox appeared to be correlated with the date of spring arrival of the geese. Red foxes breed regularly on the island but in very low numbers that appear to have been unchanged over a long period - a situation that resemble what has been recently documented from Arctic America. Our study suggests that the three predators found breeding on Kolguev Island possess capacities for shifting to changing circumstances in low-arctic ecosystem as long as other small - medium sized terrestrial herbivores are present in good numbers. PMID:25692786

  10. Rough-Legged Buzzards, Arctic Foxes and Red Foxes in a Tundra Ecosystem without Rodents

    PubMed Central

    Pokrovsky, Ivan; Ehrich, Dorothée; Ims, Rolf A.; Kondratyev, Alexander V.; Kruckenberg, Helmut; Kulikova, Olga; Mihnevich, Julia; Pokrovskaya, Liya; Shienok, Alexander

    2015-01-01

    Small rodents with multi-annual population cycles strongly influence the dynamics of food webs, and in particular predator-prey interactions, across most of the tundra biome. Rodents are however absent from some arctic islands, and studies on performance of arctic predators under such circumstances may be very instructive since rodent cycles have been predicted to collapse in a warming Arctic. Here we document for the first time how three normally rodent-dependent predator species—rough-legged buzzard, arctic fox and red fox – perform in a low-arctic ecosystem with no rodents. During six years (in 2006-2008 and 2011-2013) we studied diet and breeding performance of these predators in the rodent-free Kolguev Island in Arctic Russia. The rough-legged buzzards, previously known to be a small rodent specialist, have only during the last two decades become established on Kolguev Island. The buzzards successfully breed on the island at stable low density, but with high productivity based on goslings and willow ptarmigan as their main prey – altogether representing a novel ecological situation for this species. Breeding density of arctic fox varied from year to year, but with stable productivity based on mainly geese as prey. The density dynamic of the arctic fox appeared to be correlated with the date of spring arrival of the geese. Red foxes breed regularly on the island but in very low numbers that appear to have been unchanged over a long period – a situation that resemble what has been recently documented from Arctic America. Our study suggests that the three predators found breeding on Kolguev Island possess capacities for shifting to changing circumstances in low-arctic ecosystem as long as other small - medium sized terrestrial herbivores are present in good numbers. PMID:25692786

  11. Modeling evapotranspiration in Arctic coastal plain ecosystems using a modified BIOME-BGC model

    NASA Astrophysics Data System (ADS)

    Engstrom, Ryan; Hope, Allen; Kwon, Hyojung; Harazono, Yoshinobu; Mano, Masayoshi; Oechel, Walter

    2006-06-01

    Modeling evapotranspiration (ET) in Arctic coastal plain ecosystems is challenging owing to the unique conditions present in this environment, including permafrost, nonvascular vegetation, and a large standing dead vegetation component. In this study the ecosystem process model, BIOME-BGC, was adapted to represent these unique conditions in Arctic ecosystems by including a new water storage and evaporation routine that accounts for nonvascular vegetation and the effects of permafrost, adding ground heat flux as an input, and representing ground shading by dead vegetation. The new Arctic version and the original BIOME-BGC models are compared to observed ET from two eddy flux towers in Barrow, Alaska over four summer seasons (1999-2002). The two towers are located less than 1 km apart, yet represent contrasting moisture conditions. One is located in a drained thaw lake, marsh area, while the other is located in a drier, upland area characterized by mesic tundra. Results indicate that the original BIOME-BGC model substantially underestimated ET, while the Arctic version slightly overestimated ET at both sites. The new Arctic model version worked particularly well at the wet tower because the model was able to capture energy limitations better than water limitations. Errors in the simulation of snowmelt date led to errors in the ET estimates at both sites. Finally, the substantial differences in soil moisture led to substantially different ET rates between the sites that were difficult to simulate and indicates that soil moisture heterogeneity is a strong controller on ET in these ecosystems.

  12. Effects of selenium supplementation in cattle on aquatic ecosystems in northern California

    SciTech Connect

    Norman, B.; Nader, G.; Oliver, M.; Delmas, R.; Drake, D.; George, H. )

    1992-09-15

    The potential impact on aquatic ecosystems of supplementing the diets of beef cattle with selenium (Se) was studied on 4 northern California ranches. All study sites included an area of concentrated use by cattle that had diets supplemented with Se. In each case, a stream flowed through the site and provided a control sampling area upstream and a treated sampling area downstream. Specimens of water, sediment, algae, aquatic plants, aquatic invertebrates, and fish were analyzed fluorometrically for total Se content. Significant differences in Se concentration were not found between specimens from upstream control areas and those from downstream areas subjected to use by Se-treated cattle. Evidence was not found that Se supplementation in cattle at maximal permitted concentrations caused Se accumulation in associated aquatic ecosystems.

  13. Technology-Supported Inquiry for Learning about Aquatic Ecosystems

    ERIC Educational Resources Information Center

    Hmelo-Silver, Cindy E.; Eberbach, Catherine; Jordan, Rebecca

    2014-01-01

    Understanding ecosystems is challenging, but important for becoming environmentally-literate citizens of today's society. People have difficulty considering how different components, mechanisms, and phenomena, both visible and invisible, are interconnected within ecosystems. This research presents both the design and initial testing of an…

  14. Increases in Growing Season Length and Changes in Precipitation at Six Different Arctic and Subarctic Ecosystems from 1906-Present

    NASA Astrophysics Data System (ADS)

    Culler, L. E.; Finger, R.; Plane, E.; Ayres, M.; Virginia, R. A.

    2015-12-01

    Ecological dynamics across the Arctic are responding to rapid changes in climate. As a whole, the Arctic has warmed at approximately twice the rate of the rest of the world, but changes in temperature and precipitation experienced at regional and local scales are most important for coupled human-natural systems. In addition, biologically-relevant climate indices are necessary for quantifying ecological responses of terrestrial and aquatic systems to varying climate. We compared climatic changes at six different Arctic and sub-Arctic locations, including two in Greenland (Kangerlussuaq, Sisimiut), one in Sweden (Abisko), and three in Alaska (Barrow, Nome, Fairbanks). We amassed weather data (daily temperature and precipitation), dating as far back as 1906, from public-access databases and used these data to calculate indices such as length of growing season, growing season degree days (GDD), and growing season precipitation. Annual GDD increased at all locations (average of 13% increase in GDD since 1980), but especially in western Greenland (16 and 37% in Kangerlussuaq and Sisimiut, respectively). Changes in growing season precipitation were more variable, with only Barrow, AK and Abisko, Sweden experiencing increased precipitation. All other sites experienced stable or slightly declining precipitation. Increasing temperatures and relatively stable precipitation translates to increased evapotranspiration potential, which influences soil moisture, lake depth, vegetation, carbon emissions, and fire susceptibility. Understanding local and regional trends in temperature and precipitation can help explain observed phenological changes and other processes at population, community, and ecosystem levels. In addition, identification of locations most susceptible to future change will allow scientists to closely monitor their ecological dynamics, anticipate changes in coupled human-natural systems, and consider adaptation plans for the most rapidly changing systems.

  15. Agrochemical mitigation of three aquatic macrophytes: implications for ecosystem services

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural runoff containing nitrogen and phosphorus is a major contributor to eutrophication in aquatic systems. Vegetated drainage ditches lining agricultural fields have been investigated for their potential to mitigate runoff, acting similarly to a wetland as they filter contaminants. The ef...

  16. Linking Aquatic Ecosystems to Human Well-Being

    EPA Science Inventory

    While ecological indicators should have relevance to people, a clear methodology to develop and evaluate this characteristic of ecological indicators is not well developed. Economists developed the concept of “Final Ecosystem Goods and Services”. Because these featur...

  17. ACID PRECIPITATION AND ITS EFFECTS ON TERRESTRIAL AND AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Man-induced change in the chemical climate of the earth has increased. Recent research has demonstrated that atmospheric deposition contains both beneficial nutrients and injurious substances; plants, animals, and ecosystems vary greatly in susceptibility; injury is most likely w...

  18. Preventing, controlling, and managing alien species introduction for the health of aquatic and marine ecosystems

    USGS Publications Warehouse

    Short, C.I.; Gross, S.K.; Wilkinson, D.

    2004-01-01

    The introduction and spread of invasive species is an emerging global problem. As economic and ecological impacts continue to grow, there will be an increasing need to develop innovative solutions and global partnerships to combat the increasing rate of invasions and their accompanying impacts. Threats to sustainable fisheries in North America associated with alien species come from many global directions and sources and can be deliberate or the unintended consequence of other actions. Decisions about the role of sustainable fisheries in protecting and restoring the health of aquatic ecosystems become even more complex when economic and social factors are considered along with environmental impacts, because many intentionally introduced species also have associated economic and community costs and benefits. Actions designed to prevent or control alien species in an aquatic ecosystem are often complicated by these nonenvironmental factors as well as public perception and opinion. Aquatic ecosystems are disturbed to varying degrees by alien species, including disease organisms. Prevention is the first and best line of defense. Determining likely pathways and effective countermeasures is more cost-effective than either eradication or control. Our ability to quickly identify new species and their associated risk to ecosystems is critical in designing and implementing effective control and management actions. Lack of infrastructure and necessary resources, clear-cut authority for regulation and action, and scientific information about the biology of alien species and effective control techniques are often limiting factors that prevent the needed action to protect aquatic ecosystems.

  19. Pan-Arctic modelling of net ecosystem exchange of CO2

    PubMed Central

    Shaver, G. R.; Rastetter, E. B.; Salmon, V.; Street, L. E.; van de Weg, M. J.; Rocha, A.; van Wijk, M. T.; Williams, M.

    2013-01-01

    Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation (PAR). The model was developed in concert with a survey of the light response of NEE in Arctic and subarctic tundras in Alaska, Greenland, Svalbard and Sweden. Model parametrizations based on data collected in one part of the Arctic can be used to predict NEE in other parts of the Arctic with accuracy similar to that of predictions based on data collected in the same site where NEE is predicted. The principal requirement for the dataset is that it should contain a sufficiently wide range of measurements of NEE at both high and low values of LAI, air temperature and PAR, to properly constrain the estimates of model parameters. Canopy N content can also be substituted for leaf area in predicting NEE, with equal or greater accuracy, but substitution of soil temperature for air temperature does not improve predictions. Overall, the results suggest a remarkable convergence in regulation of NEE in diverse ecosystem types throughout the Arctic. PMID:23836790

  20. Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens

    PubMed Central

    Gharajehdaghipour, Tazarve; Roth, James D.; Fafard, Paul M.; Markham, John H.

    2016-01-01

    Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ15N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra. PMID:27045973

  1. Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens.

    PubMed

    Gharajehdaghipour, Tazarve; Roth, James D; Fafard, Paul M; Markham, John H

    2016-01-01

    Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ(15)N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra. PMID:27045973

  2. Pan-Arctic modelling of net ecosystem exchange of CO2.

    PubMed

    Shaver, G R; Rastetter, E B; Salmon, V; Street, L E; van de Weg, M J; Rocha, A; van Wijk, M T; Williams, M

    2013-08-19

    Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation (PAR). The model was developed in concert with a survey of the light response of NEE in Arctic and subarctic tundras in Alaska, Greenland, Svalbard and Sweden. Model parametrizations based on data collected in one part of the Arctic can be used to predict NEE in other parts of the Arctic with accuracy similar to that of predictions based on data collected in the same site where NEE is predicted. The principal requirement for the dataset is that it should contain a sufficiently wide range of measurements of NEE at both high and low values of LAI, air temperature and PAR, to properly constrain the estimates of model parameters. Canopy N content can also be substituted for leaf area in predicting NEE, with equal or greater accuracy, but substitution of soil temperature for air temperature does not improve predictions. Overall, the results suggest a remarkable convergence in regulation of NEE in diverse ecosystem types throughout the Arctic. PMID:23836790

  3. Economic Valuation of Ecosystem Goods and Services in a Melting Arctic

    NASA Astrophysics Data System (ADS)

    O'Garra, T.

    2014-12-01

    The Arctic region is composed of unique ecosystems that provide a range of goods and services to local and global populations. However, Arctic sea-ice is melting at an unprecedented rate, threatening many of these ecosystems and the services they provide. Yet as the ice melts and certain goods and services are lost, other resources such as oil and minerals will become accessible. The question is: how do the losses compare with the opportunities? And how are the losses and potential gains likely to be distributed? To address these questions, this study provides a preliminary assessment of the quantity, distribution and economic value of the ecosystem services (ES) provided by Arctic ecosystems, both now and in the future given a scenario of sure climate change. Using biophysical and economic data from existing studies (and some primary data), preliminary estimates indicate that the Arctic currently provides 357m/yr (in 2014 US) in subsistence hunting value to local communities, of which reindeer/caribou comprise 83%. Reindeer herding provides 110m/yr to Arctic communities. Interestingly, 'non-use (existence/cultural) values' associated with Arctic species are very high at 11bn/yr to members of Arctic states. The Arctic also provides ES that accrue to the global community: oil resources (North Slope; 5bn profits in 2013), commercial fisheries ( 515mn/yr) and most importantly, climate regulation services. Recent models (Whiteman; Euskirchen) estimate that the loss of climate regulation services provided by Arctic ice will cost 200 - 500bn/yr, a value which dwarfs all others. Assuming no change in atmospheric temperature compared to 2014, the net present value of the Arctic by 2050 (1.4% discount rate) comes to over $9 trillion. However, given Wang and Overland (2009) predictions of ice-free summers by 2037, we expect many of these benefits will be lost. For example, it is fairly well-established that endemic species, such as polar bears, will decline with sea-ice melt

  4. Investigating aquatic ecosystems of small lakes in Khorezm, Uzbekistan

    USGS Publications Warehouse

    Saito, L.; Scott, J.; Rosen, M.; Nishonov, Bakhriddin; Chandra, S.; Lamers, John P.A.; Fayzieva, Dilorom; Shanafield, M.

    2009-01-01

    The Khorezm province of Uzbekistan, located in the Aral Sea Basin, suffers from severe environmental and human health problems due to decades of unsustainable land and water management. Agriculture is the dominant land use in Khorezm, and agricultural runoff water has impacted many small lakes. In this water-scarce region, these lakes may provide a water source for irrigation or fish production. Samples have been collected from 13 of these lakes since 2006 to assess water quality, the aquatic food web, and possible limits to aquatic production. Lake salinity varied from 1 to >10 g/L both between and within lakes. Although hydrophobic contaminants concentrations were low (82-241 pg toxic equivalents/mL in June 2006, October 2006, and June 2007), aquatic species diversity and relative density were low in most lakes. Ongoing work is focused on 4 lakes with pelagic food webs to estimate fish production and assess anthropogenic impacts on the food web. Lake sediment cores are also being examined for organic contaminants, and hydrology is being assessed with stable isotopes. ?? 2009 ASCE.

  5. A Survey of Submerged Aquatic Vegetation in Three Sub-arctic Lakes near Abisko, Sweden

    NASA Astrophysics Data System (ADS)

    Sampson, J.; Stilson, K.; Varner, R. K.; Crill, P. M.; Wik, M.; Crawford, M.

    2014-12-01

    We surveyed the submerged aquatic vegetation (SAV) in three sub-arctic lakes (Mellan Harrsjön, Inre Harrsjön, and Villasjön) located near Abisko in northern Sweden. Samples were collected using an extended rake, after which they were photographed and the plants identified. We also collected environmental data including temperature, dissolved oxygen, and secchi depth. Percent cover of SAV was taken twice using a 0.5 m. quadrat in shallow areas to track the changes in vegetation growth over time. In addition, we tested surface sediment samples for grain size and carbon, hydrogen, nitrogen, and sulfur composition. The percent cover of SAV in Mellan Harrsjön varied from 36%-49% and in Inre Harrsjön it averaged 19%. Across all three lakes, the average percent clay, silt, and sand was 3.8%, 50.1%, 46%, respectively. Because little research similar to this has been conducted in the area in such a comprehensive manner, these results are important to establish a baseline. Furthermore, these data will help establish how the SAV and environmental data may contribute to methane production and emission in these sub-arctic lakes.

  6. Mercury in Arctic Marine Ecosystems: Sources, Pathways, and Exposure

    PubMed Central

    Kirk, Jane L.; Lehnherr, Igor; Andersson, Maria; Braune, Birgit M.; Chan, Laurie; Dastoor, Ashu P.; Durnford, Dorothy; Gleason, Amber L.; Loseto, Lisa L.; Steffen, Alexandra; St. Louis, Vincent L.

    2014-01-01

    Mercury in the Arctic is an important environmental and human health issue. The reliance of Northern Peoples on traditional foods, such as marine mammals, for subsistence means that they are particularly at risk from mercury exposure. The cycling of mercury in Arctic marine systems is reviewed here, with emphasis placed on the key sources, pathways and processes which regulate mercury levels in marine food webs and ultimately the exposure of human populations to this contaminant. While many knowledge gaps exist limiting our ability to make strong conclusions, it appears that the long range transport of mercury from Asian emissions is an important source of atmospheric Hg to the Arctic and that mercury methylation resulting in monomethylmercury production (an organic form of mercury which is both toxic and bioaccumulated) in Arctic marine waters is the principal source of mercury incorporated into food webs. Mercury concentrations in biological organisms have increased since the onset of the industrial age and are controlled by a combination of abiotic factors (e.g., monomethylmercury supply), food web dynamics and structure, and animal behavior (e.g., habitat selection and feeding behavior). Finally, although some Northern Peoples have high mercury concentrations of mercury in their blood and hair, harvesting and consuming traditional foods has many nutritional, social, cultural and physical health benefits which must be considered in risk management and communication. PMID:23102902

  7. Fire and aquatic ecosystems in forested biomes of North America

    USGS Publications Warehouse

    Gresswell, Robert E.

    1999-01-01

    Synthesis of the literature suggests that physical, chemical, and biological elements of a watershed interact with long-term climate to influence fire regime, and that these factors, in concordance with the postfire vegetation mosaic, combine with local-scale weather to govern the trajectory and magnitude of change following a fire event. Perturbation associated with hydrological processes is probably the primary factor influencing postfire persistence of fishes, benthic macroinvertebrates, and diatoms in fluvial systems. It is apparent that salmonids have evolved strategies to survive perturbations occurring at the frequency of wildland fires (100a??102 years), but local populations of a species may be more ephemeral. Habitat alteration probably has the greatest impact on individual organisms and local populations that are the least mobile, and reinvasion will be most rapid by aquatic organisms with high mobility. It is becoming increasingly apparent that during the past century fire suppression has altered fire regimes in some vegetation types, and consequently, the probability of large stand-replacing fires has increased in those areas. Current evidence suggests, however, that even in the case of extensive high-severity fires, local extirpation of fishes is patchy, and recolonization is rapid. Lasting detrimental effects on fish populations have been limited to areas where native populations have declined and become increasingly isolated because of anthropogenic activities. A strategy of protecting robust aquatic communities and restoring aquatic habitat structure and life history complexity in degraded areas may be the most effective means for insuring the persistence of native biota where the probability of large-scale fires has increased.

  8. Toxic metals in aquatic ecosystems: a microbiological perspective.

    PubMed Central

    Ford, T; Ryan, D

    1995-01-01

    Microbe-metal interactions in aquatic environments and their exact role in transport and transformations of toxic metals are poorly understood. This paper will briefly review our understanding of these interactions. Ongoing research in Lake Chapala, Mexico, the major water source for the City of Guadalajara, provides an opportunity to study the microbiological aspects of metal-cycling in the water column. Constant resuspension of sediments provides a microbiologically rich aggregate-based system. Data indicate that toxic metals are concentrated on aggregate material and bioaccumulate in the food chain. A provisional model is presented for involvement of microbial aggregates in metal-cycling in Lake Chapala. PMID:7621793

  9. Toxic metals in aquatic ecosystems: a microbiological perspective.

    PubMed

    Ford, T; Ryan, D

    1995-02-01

    Microbe-metal interactions in aquatic environments and their exact role in transport and transformations of toxic metals are poorly understood. This paper will briefly review our understanding of these interactions. Ongoing research in Lake Chapala, Mexico, the major water source for the City of Guadalajara, provides an opportunity to study the microbiological aspects of metal-cycling in the water column. Constant resuspension of sediments provides a microbiologically rich aggregate-based system. Data indicate that toxic metals are concentrated on aggregate material and bioaccumulate in the food chain. A provisional model is presented for involvement of microbial aggregates in metal-cycling in Lake Chapala. PMID:7621793

  10. Challenges of deriving a complete biosphere greenhouse gas balance through integration of terrestrial and aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Peichl, Matthias

    2013-04-01

    Past research efforts have mostly focused on separately investigating the exchange of greenhouse gases (GHGs) within the limits of different terrestrial and aquatic ecosystem types. More recently however, it has been recognized that GHG exchanges and budgets are not limited to boundaries of the terrestrial or aquatic biosphere components and instead are often tightly linked amongst the different ecosystem types. Primarily the aquatic production and export of GHGs due to substrate supply or discharge from surrounding terrestrial ecosystems play a major role in regional GHG budgets. Understanding the mechanisms and drivers of this connectivity between different terrestrial and aquatic ecosystem GHG exchanges is therefore necessary to develop landscape-level GHG budgets and to understand their sensitivity to disturbances of the biosphere. Moreover, the exchange of carbon dioxide (CO2) as the most important GHG species has been the primary research objective with regards to obtaining better estimates of the carbon sequestration potential of the biosphere. However, methane (CH4) and nitrous oxide (N2O) emissions may offset CO2 sinks and considerably affect the complete GHG balance in both terrestrial and aquatic systems. Including their contribution and improved knowledge on the dynamics of these two gas species is therefore essential for complete GHG budget estimates. At present, the integration of terrestrial and aquatic GHG exchanges toward landscape GHG budgets poses numerous challenges. These include the need for a better knowledge of i) the contribution of CH4 and N2O to the GHG budgets within contrasting terrestrial (forests, peatlands, grasslands, croplands) and aquatic (lake, streams) ecosystems when integrated over a full year, ii) the effect of ecosystem properties (e.g. age and/or development stage, size of water body) on the GHG balance, iii) the impact of management effects (e.g. nitrogen fertilizer application), iv) differences among climate regions and v

  11. EFFECTS OF CHLORENDIC ACID, A PRIORITY TOXIC SUBSTANCES, ON LABORATORY AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Experiments were conducted to estimate the effects of chlorendic acid and its neutralized form on laboratory aquatic ecosystems. In short-term flask studies, chlorendic acid concentrations of 500 mg/L (pH 3.5) completely inhibited algal growth and microfaunal activity, 250 mg/L (...

  12. Fuzzy model for risk assessment of persistent organic pollutants in aquatic ecosystems.

    PubMed

    Seguí, X; Pujolasus, E; Betrò, S; Agueda, A; Casal, J; Ocampo-Duque, W; Rudolph, I; Barra, R; Páez, M; Barón, E; Eljarrat, E; Barceló, D; Darbra, R M

    2013-07-01

    We developed a model for evaluating the environmental risk of persistent organic pollutants (POPs) to aquatic organisms. The model is based on fuzzy theory and uses information provided by international experts through a questionnaire. It has been tested in two case studies for a particular type of POPs: brominated flame retardants (BFRs). The first case study is related to the EU-funded AQUATERRA project, with sampling campaigns carried out in two Ebro tributaries in Spain (the Cinca and Vero Rivers). The second one, named the BROMACUA project, assessed different aquatic ecosystems in Chile (San Vicente Bay) and Colombia (Santa Marta Marsh). In both projects, the BFRs under study were polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD). However, the model can be extrapolated to other POPs and to different aquatic ecosystems to provide useful results for decision-makers. PMID:23524177

  13. ECOSYSTEM RESTORATION: MANAGEMENT PRACTICES FOR PROTECTING AND ENHANCING AQUATIC RESOURCES

    EPA Science Inventory

    This poster describes research that addresses the question: Which management practices are most successful for protection and restoration of ecological resources? The Ecosystem Restoration Research Program of EPA/ORD is designed to conduct basic and applied field research to eva...

  14. A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia.

    PubMed

    Rybczynski, Natalia; Dawson, Mary R; Tedford, Richard H

    2009-04-23

    Modern pinnipeds (seals, sea lions and the walrus) are semi-aquatic, generally marine carnivores the limbs of which have been modified into flippers. Recent phylogenetic studies using morphological and molecular evidence support pinniped monophyly, and suggest a sister relationship with ursoids (for example bears) or musteloids (the clade that includes skunks, badgers, weasels and otters). Although the position of pinnipeds within modern carnivores appears moderately well resolved, fossil evidence of the morphological steps leading from a terrestrial ancestor to the modern marine forms has been weak or contentious. The earliest well-represented fossil pinniped is Enaliarctos, a marine form with flippers, which had appeared on the northwestern shores of North America by the early Miocene epoch. Here we report the discovery of a nearly complete skeleton of a new semi-aquatic carnivore from an early Miocene lake deposit in Nunavut, Canada, that represents a morphological link in early pinniped evolution. The new taxon retains a long tail and the proportions of its fore- and hindlimbs are more similar to those of modern terrestrial carnivores than to modern pinnipeds. Morphological traits indicative of semi-aquatic adaptation include a forelimb with a prominent deltopectoral ridge on the humerus, a posterodorsally expanded scapula, a pelvis with relatively short ilium, a shortened femur and flattened phalanges, suggestive of webbing. The new fossil shows evidence of pinniped affinities and similarities to the early Oligocene Amphicticeps from Asia and the late Oligocene and Miocene Potamotherium from Europe. The discovery suggests that the evolution of pinnipeds included a freshwater transitional phase, and may support the hypothesis that the Arctic was an early centre of pinniped evolution. PMID:19396145

  15. Landscape Characterization of Arctic Ecosystems Using Data Mining Algorithms and Large Geospatial Datasets

    NASA Astrophysics Data System (ADS)

    Langford, Z. L.; Kumar, J.; Hoffman, F. M.

    2015-12-01

    Observations indicate that over the past several decades, landscape processes in the Arctic have been changing or intensifying. A dynamic Arctic landscape has the potential to alter ecosystems across a broad range of scales. Accurate characterization is useful to understand the properties and organization of the landscape, optimal sampling network design, measurement and process upscaling and to establish a landscape-based framework for multi-scale modeling of ecosystem processes. This study seeks to delineate the landscape at Seward Peninsula of Alaska into ecoregions using large volumes (terabytes) of high spatial resolution satellite remote-sensing data. Defining high-resolution ecoregion boundaries is difficult because many ecosystem processes in Arctic ecosystems occur at small local to regional scales, which are often resolved in by coarse resolution satellites (e.g., MODIS). We seek to use data-fusion techniques and data analytics algorithms applied to Phased Array type L-band Synthetic Aperture Radar (PALSAR), Interferometric Synthetic Aperture Radar (IFSAR), Satellite for Observation of Earth (SPOT), WorldView-2, WorldView-3, and QuickBird-2 to develop high-resolution (˜5m) ecoregion maps for multiple time periods. Traditional analysis methods and algorithms are insufficient for analyzing and synthesizing such large geospatial data sets, and those algorithms rarely scale out onto large distributed- memory parallel computer systems. We seek to develop computationally efficient algorithms and techniques using high-performance computing for characterization of Arctic landscapes. We will apply a variety of data analytics algorithms, such as cluster analysis, complex object-based image analysis (COBIA), and neural networks. We also propose to use representativeness analysis within the Seward Peninsula domain to determine optimal sampling locations for fine-scale measurements. This methodology should provide an initial framework for analyzing dynamic landscape

  16. Palladium Nanoparticles: Is There a Risk for Aquatic Ecosystems?

    PubMed

    Lüderwald, Simon; Seitz, Frank; Seisenbaeva, Gulaim A; Kessler, Vadim G; Schulz, Ralf; Bundschuh, Mirco

    2016-08-01

    Nano-sized palladium (nano-Pd) is used in catalytic converters of automobiles, where it can be released into the environment by abrasion. Although these particles may subsequently be transported into surface water bodies, no data estimating their fate and toxicity in aquatic systems exists. This study characterized the particle size development of nano-Pd (advertised size ~12 nm; hydrodynamic size ~70 nm) in media with variable ionic strength (IS). Additionally, the particles' acute toxicity for daphnids and chironomids was assessed. While nano-Pd agglomerated more quickly with increasing IS, it caused only marginal effects in both test species after 96 h of exposure. After 144 h of exposure, however, an EC50 value of 1.23 mg nano-Pd/L for daphnids was determined indicating effects over the long run. When considering the relatively low environmental concentration of elemental Pd in surface waters (usually ng/L), though, this study suggests only a low aquatic risk in response to nano-Pd. PMID:27107586

  17. Aquatic polymers can drive pathogen transmission in coastal ecosystems

    PubMed Central

    Shapiro, Karen; Krusor, Colin; Mazzillo, Fernanda F. M.; Conrad, Patricia A.; Largier, John L.; Mazet, Jonna A. K.; Silver, Mary W.

    2014-01-01

    Gelatinous polymers including extracellular polymeric substances (EPSs) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. Yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. We used the zoonotic parasite Toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived pathogens to marine fauna and humans. We show that transparent exopolymer particles, a particulate form of EPS, enhance T. gondii association with marine aggregates, material consumed by organisms otherwise unable to access micrometre-sized particles. Adhesion to EPS biofilms on macroalgae also captures T. gondii from the water, enabling uptake of pathogens by invertebrates that feed on kelp surfaces. We demonstrate the acquisition, concentration and retention of T. gondii by kelp-grazing snails, which can transmit T. gondii to threatened California sea otters. Results highlight novel mechanisms whereby aquatic polymers facilitate incorporation of pathogens into food webs via association with particle aggregates and biofilms. Identifying the critical role of invisible polymers in transmission of pathogens in the ocean represents a fundamental advance in understanding and mitigating the health impacts of coastal habitat pollution with contaminated runoff. PMID:25297861

  18. Aquatic polymers can drive pathogen transmission in coastal ecosystems.

    PubMed

    Shapiro, Karen; Krusor, Colin; Mazzillo, Fernanda F M; Conrad, Patricia A; Largier, John L; Mazet, Jonna A K; Silver, Mary W

    2014-11-22

    Gelatinous polymers including extracellular polymeric substances (EPSs) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. Yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. We used the zoonotic parasite Toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived pathogens to marine fauna and humans. We show that transparent exopolymer particles, a particulate form of EPS, enhance T. gondii association with marine aggregates, material consumed by organisms otherwise unable to access micrometre-sized particles. Adhesion to EPS biofilms on macroalgae also captures T. gondii from the water, enabling uptake of pathogens by invertebrates that feed on kelp surfaces. We demonstrate the acquisition, concentration and retention of T. gondii by kelp-grazing snails, which can transmit T. gondii to threatened California sea otters. Results highlight novel mechanisms whereby aquatic polymers facilitate incorporation of pathogens into food webs via association with particle aggregates and biofilms. Identifying the critical role of invisible polymers in transmission of pathogens in the ocean represents a fundamental advance in understanding and mitigating the health impacts of coastal habitat pollution with contaminated runoff. PMID:25297861

  19. ELF communications system ecological monitoring program: Aquatic ecosystem studies

    NASA Astrophysics Data System (ADS)

    Burton, Thomas M.; Stout, R. J.; Winterstein, Scott; Coon, Thomas; Novinger, Doug

    1994-11-01

    The U.S. Navy has completed a program that monitored biota and ecological miationships for possible effects from electromagnetic (EM) fields produced by its Extremely Low Frequency (ELF) Communications System. This report documents the results and conclusions of aquatic studies conducted near its transmitting antenna in Michigan. From 1982 through 1993 researchers from the Michigan State University (MSU) monitored aquatic flora and fauna on matched reaches of the Ford River. A treatment site was located immediately adjacent to the antenna, whereas a control site was situated at a distance downstream. Functional and structural components of the periphyton, insect, and fish communities were monitored. The research team also measured ambient factors such as temperature, discharge, and water quality indicators. Data were analyzed using a variety of statistical tests; however, BACI techniques were emphasized. Results indicated a relative increase in algal biomass at the treatment site after the antenna became fully operational, but no changes in any other parameter or organism. MSU concludes that algal biomass was affected by ELF EM exposure. Since neither the other ecological characteristics of the periphyton nor the insect and fish communities showed any effects, MSU infers little EM impact to riverine habitats.

  20. Endoparasites in the feces of arctic foxes in a terrestrial ecosystem in Canada

    PubMed Central

    Elmore, Stacey A.; Lalonde, Laura F.; Samelius, Gustaf; Alisauskas, Ray T.; Gajadhar, Alvin A.; Jenkins, Emily J.

    2013-01-01

    The parasites of arctic foxes in the central Canadian Arctic have not been well described. Canada’s central Arctic is undergoing dramatic environmental change, which is predicted to cause shifts in parasite and wildlife species distributions, and trophic interactions, requiring that baselines be established to monitor future alterations. This study used conventional, immunological, and molecular fecal analysis techniques to survey the current gastrointestinal endoparasite fauna currently present in arctic foxes in central Nunavut, Canada. Ninety-five arctic fox fecal samples were collected from the terrestrial Karrak Lake ecosystem within the Queen Maud Gulf Migratory Bird Sanctuary. Samples were examined by fecal flotation to detect helminths and protozoa, immunofluorescent assay (IFA) to detect Cryptosporidium and Giardia, and quantitative PCR with melt-curve analysis (qPCR-MCA) to detect coccidia. Positive qPCR-MCA products were sequenced and analyzed phylogenetically. Arctic foxes from Karrak Lake were routinely shedding eggs from Toxascaris leonina (63%). Taeniid (15%), Capillarid (1%), and hookworm eggs (2%), Sarcocystis sp. sporocysts 3%), and Eimeria sp. (6%), and Cystoisospora sp. (5%) oocysts were present at a lower prevalence on fecal flotation. Cryptosporidium sp. (9%) and Giardia sp. (16%) were detected by IFA. PCR analysis detected Sarcocystis (15%), Cystoisospora (5%), Eimeria sp., and either Neospora sp. or Hammondia sp. (1%). Through molecular techniques and phylogenetic analysis, we identified two distinct lineages of Sarcocystis sp. present in arctic foxes, which probably derived from cervid and avian intermediate hosts. Additionally, we detected previously undescribed genotypes of Cystoisospora. Our survey of gastrointestinal endoparasites in arctic foxes from the central Canadian Arctic provides a unique record against which future comparisons can be made. PMID:24533320

  1. Delayed responses of an Arctic ecosystem to an extreme summer: impacts on net ecosystem exchange and vegetation functioning

    NASA Astrophysics Data System (ADS)

    Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

    2014-10-01

    The importance and consequences of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. In the summer of 2007 in Barrow, Arctic Alaska, there were unusually high air temperatures (the fifth warmest summer over a 65-year period) and record low precipitation (the lowest over a 65-year period). These abnormal conditions were associated with substantial desiccation of the Sphagnum layer and a reduced net Sphagnum CO2 sink but did not affect net ecosystem exchange (NEE) from this wet-sedge arctic tundra ecosystem. Microbial biomass, NH4+ availability, gross primary production (GPP), and ecosystem respiration (Reco) were generally greater during this extreme summer. The cumulative ecosystem CO2 sink in 2007 was similar to the previous summers, suggesting that vascular plants were able to compensate for Sphagnum CO2 uptake, despite the impact on other functions and structure such as desiccation of the Sphagnum layer. Surprisingly, the lowest ecosystem CO2 sink over a five summer record (2005-2009) was observed during the 2008 summer (~70% lower), directly following the unusually warm and dry summer, rather than during the extreme summer. This sink reduction cannot solely be attributed to the potential damage to mosses, which typically contribute ~40% of the entire ecosystem CO2 sink. Importantly, the return to a substantial cumulative CO2 sink occurred two summers after the extreme event, which suggests a substantial resilience of this tundra ecosystem to at least an isolated extreme event. Overall, these results show a complex response of the CO2 sink and its sub-components to atypically warm and dry conditions. The impact of multiple extreme events requires further investigation.

  2. Potential Effects of Climate Change on Aquatic Ecosystems of the Great Plains of North America

    NASA Astrophysics Data System (ADS)

    Covich, A. P.; Fritz, S. C.; Lamb, P. J.; Marzolf, R. D.; Matthews, W. J.; Poiani, K. A.; Prepas, E. E.; Richman, M. B.; Winter, T. C.

    1997-06-01

    The Great Plains landscape is less topographically complex than most other regions within North America, but diverse aquatic ecosystems, such as playas, pothole lakes, ox-bow lakes, springs, groundwater aquifers, intermittent and ephemeral streams, as well as large rivers and wetlands, are highly dynamic and responsive to extreme climatic fluctuations. We review the evidence for climatic change that demonstrates the historical importance of extremes in north-south differences in summer temperatures and east-west differences in aridity across four large subregions. These physical driving forces alter density stratification, deoxygenation, decomposition and salinity. Biotic community composition and associated ecosystem processes of productivity and nutrient cycling respond rapidly to these climatically driven dynamics. Ecosystem processes also respond to cultural effects such as dams and diversions of water for irrigation, waste dilution and urban demands for drinking water and industrial uses. Distinguishing climatic from cultural effects in future models of aquatic ecosystem functioning will require more refinement in both climatic and economic forecasting. There is a need, for example, to predict how long-term climatic forecasts (based on both ENSO and global warming simulations) relate to the permanence and productivity of shallow water ecosystems. Aquatic ecologists, hydrologists, climatologists and geographers have much to discuss regarding the synthesis of available data and the design of future interdisciplinary research.

  3. Potential effects of climate change on aquatic ecosystems of the Great Plains of North America

    USGS Publications Warehouse

    Covich, A.P.; Fritz, S.C.; Lamb, P.J.; Marzolf, R.D.; Matthews, W.J.; Poiani, K.A.; Prepas, E.E.; Richman, M.B.; Winter, T.C.

    1997-01-01

    The Great Plains landscape is less topographically complex than most other regions within North America, but diverse aquatic ecosystems, such as playas, pothole lakes, ox-bow lakes, springs, groundwater aquifers, intermittent and ephemeral streams, as well as large rivers and wetlands, are highly dynamic and responsive to extreme climatic fluctuations. We review the evidence for climatic change that demonstrates the historical importance of extremes in north-south differences in summer temperatures and east-west differences in aridity across four large subregions. These physical driving forces alter density stratification, deoxygenation, decomposition and salinity. Biotic community composition and associated ecosystem processes of productivity and nutrient cycling respond rapidly to these climatically driven dynamics. Ecosystem processes also respond to cultural effects such as dams and diversions of water for irrigation, waste dilution and urban demands for drinking water and industrial uses. Distinguishing climatic from cultural effects in future models of aquatic ecosystem functioning will require more refinement in both climatic and economic forecasting. There is a need, for example, to predict how long-term climatic forecasts (based on both ENSO and global warming simulations) relate to the permanence and productivity of shallow water ecosystems. Aquatic ecologists, hydrologists, climatologists and geographers have much to discuss regarding the synthesis of available data and the design of future interdisciplinary research. ?? 1997 by John Wiley & Sons, Ltd.

  4. Oceanic periglacial in the evolution of the Arctic marine ecosystem

    SciTech Connect

    Matishov, G.G.

    1996-12-31

    A study of the Arctic marine and land environment and biota is connected with the analysis of the global climatic changes and the general history of Arctic and subarctic ecological systems. Ancient glaciation not only influenced the geomorphology of landscapes, physical and chemical properties of the ocean and its seas, but also caused the global change of the morphoclimatic zonality in the ocean as a whole. Submarine and subaqual hydrological, geomorphological and biological processes on the shelves of polar and temperate latitudes had intensified especially during the melting of continental glaciers. The study of the periglacial problem consists, as a whole, in the research of the geological and biological phenomena which take place in the pelagial and the benthal outside the ice sheets and are connected with them by causal, spatial and temporal relations.

  5. Climate Change Experiments in Arctic Ecosystems: Scientific Strategy and Design Criteria

    NASA Astrophysics Data System (ADS)

    Wullschleger, S. D.; Hinzman, L. D.; McGuire, A. D.; Oberbauer, S. F.; Oechel, W. C.; Norby, R. J.; Thornton, P. E.; Schuur, E. A.; Shugart, H. H.; Walsh, J. E.; Wilson, C. J.

    2010-12-01

    Arctic and subarctic ecosystems are sensitive to changes in climate. These are among the largest and coldest of all ecosystems and are perceived by many as especially vulnerable to environmental change. Warming, in particular, is expected to be greatest in northern latitudes with potentially significant consequences for tundra, taiga, and peat lands. Observational evidence suggests that warming is already affecting physical and ecological processes in high-latitude ecosystems. Models predict that permafrost degradation and the northward expansion of shrubs into tundra represent important feedbacks on climate. Manipulative experiments can help understand the vulnerability of ecosystems to climate warming. Previous attempts to manipulate the environment of ecosystems in arctic and subarctic regions have focused on warming plant and soils, but treatments have been limited to small scales and modest increases in temperature. Manipulating the environment at larger scales and exposing ecosystems to higher temperatures for longer periods of time will be required to fully describe the physical, chemical, and biological mechanisms that govern land-atmosphere interactions. A variety of logistical and engineering challenges must be overcome and new approaches developed before we can address the questions being asked of the scientific community especially as we continue to move toward large-scale and long-term experiments. In light of the many uncertainties that surround the response of high-latitude ecosystems to global climate change, it is important that the scientific community consider how manipulative experiments can address and resolve ecosystem impacts and feedbacks to climate. A workshop sponsored by the Department of Energy, Office of Science was recently held at the University of Alaska, Fairbanks. The goal of the workshop was to highlight conclusions from observational and modeling studies about the response of arctic and subarctic ecosystems to a changing climate

  6. The influence of glacial meltwater on alpine aquatic ecosystems: a review.

    PubMed

    Slemmons, Krista E H; Saros, Jasmine E; Simon, Kevin

    2013-10-01

    The recent and rapid recession of alpine glaciers over the last 150 years has major implications for associated aquatic communities. Glacial meltwater shapes many of the physical features of high altitude lakes and streams, producing turbid environments with distinctive hydrology patterns relative to nival systems. Over the past decade, numerous studies have investigated the chemical and biological effects of glacial meltwater on freshwater ecosystems. Here, we review these studies across both lake and stream ecosystems. Focusing on alpine regions mainly in the Northern Hemisphere, we present examples of how glacial meltwater can affect habitat by altering physical and chemical features of aquatic ecosystems, and review the subsequent effects on the biological structure and function of lakes and streams. Collectively or separately, these factors can drive the overall distribution, diversity and behavior of primary producers, triggering cascading effects throughout the food web. We conclude by proposing areas for future research, particularly in regions where glaciers are soon projected to disappear. PMID:24056713

  7. Biophysical interactions in fluvial ecosystems: effects of submerged aquatic macrophytes on hydro-morphological processes and ecosystem functioning

    NASA Astrophysics Data System (ADS)

    Cornacchia, Loreta; Davies, Grieg; Grabowski, Robert; van der Wal, Daphne; van de Koppel, Johan; Wharton, Geraldene; Bouma, Tjeerd

    2016-04-01

    Strong mutual interactions occur at the interface between biota and physical processes in biogeomorphic ecosystems, possibly resulting in self-organized spatial patterns. While these interactions and feedbacks have been increasingly studied in a wide range of landscapes previously, they are still poorly understood in lower energy fluvial systems. Consequently, their impact on the functioning of aquatic ecosystems is largely unknown. In this study we investigate the role of aquatic macrophytes as biological engineers of flow and sediment in lowland streams dominated by water crowfoot (Ranunculus spp.). Using field measurements from two annual growth cycles, we demonstrate that seasonally-changing macrophyte cover maintains relative constant flow rates, both within and between vegetation, despite temporal changes in channel flow discharge. By means of a mathematical model representing the interaction between hydrodynamics and vegetation dynamics, we reveal that scale-dependent feedbacks between plant growth and flow redistribution explain the influence of macrophytes on stabilizing flow rates. Our analysis reveals important implications for ecosystem functions. The creation of fast-flowing channels allows an adequate conveyance of water throughout the annual cycle; yet, patches also have a significant influence on sediment dynamics leading to heterogeneous habitats, thereby facilitating other species. As a last step we investigate the consequences on stream ecosystem functioning, by exploring the relationship between changes in macrophyte cover and the provision of different ecosystem functions (e.g. water conveyance, sediment trapping). Our results highlight that self-organization promotes the combination of multiple ecosystem functions through its effects on hydrological and morphological processes within biogeomorphic ecosystems.

  8. Boreal fire influence on Arctic tropospheric ozone, ecosystems and climate forcing

    NASA Astrophysics Data System (ADS)

    Arnold, S.; Monks, S. A.; Emmons, L. K.; Sitch, S.; Rap, A.; Law, K.; Tilmes, S.; Lamarque, J.

    2013-12-01

    Temperature observations show that the Arctic has warmed rapidly in the past few decades compared to the northern hemisphere as a whole. Model calculations suggest that changes in short-lived pollutants such as ozone and aerosol may have contributed significantly to this warming. Arctic tropospheric budgets of short-lived pollutants are impacted by both local anthropogenic emissions and by long-range transport of gases and aerosols from Europe, Asia and N. America, but also by local Boreal wildfires in summer. Our understanding of how fires impact Arctic budgets of climate-relevant atmospheric constituents is limited, and is reliant on sparse observations and models of tropospheric chemistry. A better understanding of Boreal fire influence on Arctic ozone is essential for improving the reliability of our projections of future Arctic and Northern Hemisphere climate change, especially in light of proposed climate-fire feedbacks which may enhance the intensity and extent of high latitude wildfire under a warming climate. Using the NCAR Community Earth System Model (CESM) and a scheme for tagging and tracking NOx emitted by high latitude wildfires and its resultant tropospheric ozone production, we investigate the impacts of fire-sourced ozone on summertime high latitude radiative forcing and on ecosystems. The large fraction of NOy present as PAN in the Arctic suggests there may be a strong sensitivity of NOy and ozone enhancement to the efficiency of vertical transport from source regions, which determines the stability of PAN as air is advected poleward. We use these simulations and aircraft observations to characterise the vertical distributions of sensitivities of Arctic NOy and ozone to remote anthropogenic and local widlfire sources, and use an offline radiative transfer model to quantify impacts on local ozone radiative forcing. We compare these vertical sensitivities with those of a primary-emitted CO-like source tracer, to investigate the role of PAN

  9. Effects of solar UV radiation on aquatic ecosystems and interactions with climate change.

    PubMed

    Häder, D-P; Kumar, H D; Smith, R C; Worrest, R C

    2007-03-01

    Recent results continue to show the general consensus that ozone-related increases in UV-B radiation can negatively influence many aquatic species and aquatic ecosystems (e.g., lakes, rivers, marshes, oceans). Solar UV radiation penetrates to ecological significant depths in aquatic systems and can affect both marine and freshwater systems from major biomass producers (phytoplankton) to consumers (e.g., zooplankton, fish, etc.) higher in the food web. Many factors influence the depth of penetration of radiation into natural waters including dissolved organic compounds whose concentration and chemical composition are likely to be influenced by future climate and UV radiation variability. There is also considerable evidence that aquatic species utilize many mechanisms for photoprotection against excessive radiation. Often, these protective mechanisms pose conflicting selection pressures on species making UV radiation an additional stressor on the organism. It is at the ecosystem level where assessments of anthropogenic climate change and UV-related effects are interrelated and where much recent research has been directed. Several studies suggest that the influence of UV-B at the ecosystem level may be more pronounced on community and trophic level structure, and hence on subsequent biogeochemical cycles, than on biomass levels per se. PMID:17344962

  10. Symptoms of change in multi-scale observations of arctic ecosystem carbon cycling

    NASA Astrophysics Data System (ADS)

    Stoy, P. C.; Williams, M. D.; Hartley, I. P.; Street, L.; Hill, T. C.; Prieto-Blanco, A.; Wayolle, A.; Disney, M.; Evans, J.; Fletcher, B.; Poyatos, R.; Wookey, P.; Merbold, L.; Wade, T. J.; Moncrieff, J.

    2009-12-01

    Arctic ecosystems are responding rapidly to observed climate change. Quantifying the magnitude of these changes, and their implications for the climate system, requires observations of their current structure and function, as well as extrapolation and modelling (i.e. ‘upscaling’) across time and space. Here, we describe the major results of the International Polar Year (IPY) ABACUS project, a multi-scale investigation across arctic Fennoscandia that couples plant and soil process studies, isotope analyses, flux and micrometeorological measurements, process modelling, and aircraft and satellite observations to improve predictions of the response of the arctic terrestrial biosphere to global change. We begin with a synthesis of eddy covariance observations from the global FLUXNET database. We demonstrate that a simple model parameterized using pan-arctic chamber measurements explains over 80% of the variance of half-hourly CO2 fluxes during the growing season across most arctic and montane tundra ecosystems given accurate measurements of leaf area index (LAI), which agrees with the recently proposed ‘functional convergence’ paradigm for tundra vegetation. The ability of MODIS to deliver accurate LAI estimates is briefly discussed and an adjusted algorithm is presented and validated using direct observations. We argue for an Information Theory-based framework for upscaling in Earth science by conceptualizing multi-scale research as a transfer of information across scales. We then demonstrate how error in upscaled arctic C flux estimates can be reduced to less than 4% from their high-resolution counterpart by formally preserving the information content of high spatial and spectral resolution aircraft and satellite imagery. Jaynes’ classic Maximum Entropy (MaxEnt) principle is employed to incorporate logical, biological and physical constraints to reduce error in downscaled flux estimates. Errors are further reduced by assimilating flux, biological and remote

  11. Impact of petroleum pollution on aquatic coastal ecosystems in Brazil

    SciTech Connect

    Silva, E.M. da; Peso-Aguiar, M.C.; Navarro, M.F.T.; Chastinet, C.B.A.

    1997-01-01

    Although oil activities generate numerous forms of environmental impact on biological communities, studies of these impacts on Brazilian coastal ecosystems are rate. Results of tests for the content of oil in sediments and organisms indicate a substantially high rate of degradation. Results for uptake of polycyclic aromatic hydrocarbons in bivalves suggested the recent occurrence of oil spills and that these organisms differed in their capabilities to bioconcentrate oil. The mangrove community has suffered constant inputs of oil and has responded with increased numbers of aerial roots, generation of malformed leaves and fruits by plants, and a decrease in litter production. Studies of the impact of oil on rocky shore communities and the toxicity of oil and its by-products to marine organisms have confirmed the results reported in the literature. Presently most of the available studies deal with the macroscopic effects of oil on organisms and have indicated that the nature of oil, climate characteristics, the physical environment, and the structure of the community influence the symptoms of oil contamination in organisms of coastal waters. Long-term studies should be carried out to assess changes in community structure, sublethal effects in populations, and the resilience of contaminated ecosystems.

  12. Using digital photos and models to analyze episodic winter snowmelt events in low-Arctic ecosystems

    NASA Astrophysics Data System (ADS)

    Pedersen, S. H.; Tamstorf, M. P.; Westergaard-Nielsen, A.; Liston, G. E.; Schmidt, N. M.

    2013-12-01

    Terrestrial snow cover is a key parameter controlling both abiotic and biotic ecosystem processes in the Arctic. Yet knowledge and observations of snow cover in Greenland are limited. However, one exception is Kobbefjord (64°07'N, 51°21'W) in West Greenland. Since 2007, Nuuk Ecological Research Operations (NERO), led by Greenland Ecosystem Monitoring, have run an ecosystem baseline monitoring program responsible for collecting extensive snow observation datasets using manual, automated, and remotely-sensed methods. The available snow datasets provide a unique opportunity to describe and analyze the spatial and temporal distribution of snow-cover features and interactions in a low-Arctic setting where snow-dependent ecosystem components and processes are also observed. The aim of this study is to understand the temporal and spatial snow evolution in a low-Arctic ecosystem where a range of validation data is available, with a particular emphasis on infrequent winter snowmelt events. Extreme winter melt events associated with air temperatures rising abruptly to above 0.0 °C and with wind speeds greater than 20 m/s have been observed. We identified these melt events and quantified their effect on the snowpack and water balance to address possible consequences for a range of biological parameters. Finally, we compared the inter-annual air temperature variation during the last five years (2007-2013) with a 119-year climate record to place these recent variations within a long-term climate perspective. We implemented a spatially distributed snow-evolution modeling system (SnowModel) to provide temporal and spatial descriptions of snow within the study area from 2007 through 2013. SnowModel was driven by climate data collected by NERO. The available snow observations enabled validation of the modeled snow depth through 1) independent manual and automated snow depth measurements, and 2) a spatial validation of the modeled snow cover depletion through snow classification

  13. Phylogenetic signal in diatom ecology: perspectives for aquatic ecosystems biomonitoring.

    PubMed

    Keck, François; Rimet, Frédéric; Franc, Alain; Bouchez, Agnés

    2016-04-01

    Diatoms include a great diversity of taxa and are recognized as powerful bioindicators in rivers. However using diatoms for monitoring programs is costly and time consuming because most of the methodologies necessitate species-level identification. This raises the question of the optimal trade-off between taxonomic resolution and bioassessment quality. Phylogenetic tools may form the bases of new, more efficient approaches for biomonitoring if relationships between ecology and phylogeny can be demonstrated. We estimated the ecological optima of 127 diatom species for 19 environmental parameters using count data from 2119 diatom communities sampled during eight years in eastern France. Using uni- and multivariate analyses, we explored the relationships between freshwater diatom phylogeny and ecology (i.e., the phylogenetic signal). We found a significant phylogenetic signal for many of the ecological optima that were tested, but the strength of the signal varied significantly from one trait to another. Multivariate analysis also showed that the multidimensional ecological niche of diatoms can be strongly related to phylogeny. The presence of clades containing species that exhibit homogeneous ecology suggests that phylogenetic information can be useful for aquatic biomonitoring. This study highlights the presence of significant patterns of ecological optima for freshwater diatoms in relation to their phylogeny. These results suggest the presence of a signal above the species level, which is encouraging for the development of simplified methods for biomonitoring survey. PMID:27411256

  14. Modeling an aquatic ecosystem: application of an evolutionary algorithm with genetic doping to reduce prediction uncertainty

    NASA Astrophysics Data System (ADS)

    Friedel, Michael; Buscema, Massimo

    2016-04-01

    Aquatic ecosystem models can potentially be used to understand the influence of stresses on catchment resource quality. Given that catchment responses are functions of natural and anthropogenic stresses reflected in sparse and spatiotemporal biological, physical, and chemical measurements, an ecosystem is difficult to model using statistical or numerical methods. We propose an artificial adaptive systems approach to model ecosystems. First, an unsupervised machine-learning (ML) network is trained using the set of available sparse and disparate data variables. Second, an evolutionary algorithm with genetic doping is applied to reduce the number of ecosystem variables to an optimal set. Third, the optimal set of ecosystem variables is used to retrain the ML network. Fourth, a stochastic cross-validation approach is applied to quantify and compare the nonlinear uncertainty in selected predictions of the original and reduced models. Results are presented for aquatic ecosystems (tens of thousands of square kilometers) undergoing landscape change in the USA: Upper Illinois River Basin and Central Colorado Assessment Project Area, and Southland region, NZ.

  15. Ecosystem-Vegetation Dynamics in sub-arctic Stordalen Mire, Sweden

    NASA Astrophysics Data System (ADS)

    Mugnani, M. P.; Varner, R. K.; Steele, K.; Frey, S. D.; Crill, P. M.

    2012-12-01

    Increased global temperatures have contributed to the thaw of permafrost and a subsequent atmospheric release of stored methane (CH4) from sub-arctic ecosystems. Palsas, small frost uplifted mounds that support specialized dry-tolerant vegetation species, degrade when permafrost thaws, allowing other species such a Sphagnum and Eriophorum to encroach on the microhabitats and outcompete other species, altering the carbon feedback into the thin arctic soil. Other climate change-related events including increased precipitation, seasonal temperature abnormalities and changes in humidity and nutrient availability may alter vegetation dynamics in terms of diversity and abundance in sub-arctic regions. During July 2012, measurements of vegetation composition and species abundance estimates were made in Stordalen Mire (68° 21' N, 19° 03' E), Abisko Sweden, two hundred kilometers north of the Arctic Circle. The mire is an area of discontinuous permafrost populated by micro-ecosystems that vary in vegetation species and abundance depending on growth conditions. All ecosystems provide beneficial services to support a range of life forms including rodents, birds, insects and reindeer. Five representative ecosystems of the mire were chosen to conduct studies on vegetation diversity and percent cover-based abundance: palsa, Eriophorum-dominated fen, Sphagnum-dominated peatland, lakeshore edge and lakeside heath. In each ecosystem vegetation species were recorded in six transects with quadrats along with a corresponding percent cover estimation and scale number based on the Braun-Blanquet percent cover method. To determine nutrient dynamics between ecosystems, soil peat samples were also taken at random from all ecosystem transects. These were analyzed for carbon and inorganic nitrogen as well as ammonium and nitrate. In the vegetation data analysis, the Shannon-Wiener Diversity Index showed that the lakeside heath ecosystem was the most diverse and even in species distribution

  16. Long-Term Release of Carbon Dioxide from Arctic Tundra Ecosystems in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Bret-Harte, M. S.; Edgar, C.; Shaver, G. R.

    2014-12-01

    Recent data syntheses and modeling studies of arctic tundra carbon dioxide (CO2) balance have suggested that the tundra is a CO2 sink, a source or neutral. Much of this uncertainty arises from a lack of data pertaining to winter CO2 flux, as well as how these ecosystems have responded to recent warming trends. Due to a harsh, remote environment, long-term, continuous measurements of arctic tundra CO2 fluxes over the full annual cycle have been non-existent. In September 2007, we began eddy covariance measurements of net ecosystem exchange (NEE, where a negative value denotes a sink) of CO2 in northern Alaska at two ecosystems, heath and wet sedge tundra. These measurements continue to the present, and represent the longest continuous record of arctic tundra NEE currently available. From January 2008 - December 2013, the ecosystems were annual sources of CO2, with the wet sedge tundra acting as a greater source (mean ± standard deviation of 50 ± 30 g C m-2 y-1) than the heath tundra (16 ± 6 g C m-2 y-1). During these same years, the ecosystems were sinks of CO2 in the summer (June - August), with less variability between the ecosystems, -77 ± 15 g C m-2 in the wet sedge tundra, and -70 ± 12 g C m-2 in the heath. Environmental controls over NEE differed between ecosystems and seasons, with the wet sedge tundra acting particularly responsive in terms of CO2 release during periods with warm air temperatures from fall to early winter. During cold winter periods, CO2 release from the snowpack in both ecosystems was related to increases in wind speed and drops in atmospheric pressure. Overall, the measured differences in the annual versus summer NEE illustrate how the sink strength of the tundra can be overestimated if data are only collected during the growing season. Furthermore, eddy covariance measurements of methane (CH4) in the wet sedge tundra during late spring to early fall from 2012 to present show that this ecosystem releases 0.34 ± 11 mg CH4 m-2 d-1

  17. Heavy Metal Pollution Characteristics of Surface Sediments in Different Aquatic Ecosystems in Eastern China: A Comprehensive Understanding

    PubMed Central

    Tang, Wenzhong; Shan, Baoqing; Zhang, Wenqiang; Zhang, Hong; Wang, Lishuo; Ding, Yuekui

    2014-01-01

    Aquatic ecosystems in eastern China are suffering threats from heavy metal pollution because of rapid economic development and urbanization. Heavy metals in surface sediments were determined in five different aquatic ecosystems (river, reservoir, estuary, lake, and wetland ecosystems). The average Cd, Cr, Cu, Ni, Pb, and Zn concentrations were 0.716, 118, 37.3, 32.7, 56.6, and 204 mg/kg, respectively, and the higher concentrations were mainly found in sediment samples from river ecosystems. Cd was the most anthropogenically enriched pollutant, followed by Zn and Pb, indicated by enrichment factors >1.5. According to consensus-based sediment quality guidelines, potential ecological risk indices, and risk assessment codes, all five types of aquatic ecosystems were found to be polluted with heavy metals, and the most polluted ecosystems were mainly rivers. Cd was the most serious pollutant in all five aquatic ecosystems, and it was mainly found in the exchangeable fraction (about 30% of the total Cd concentration, on average). The results indicate that heavy metal contamination, especially of Cd, in aquatic ecosystems in eastern China should be taken into account in the development of management strategies for protecting the aquatic environment. PMID:25268385

  18. Diversity and Expression of Bacterial Metacaspases in an Aquatic Ecosystem

    PubMed Central

    Asplund-Samuelsson, Johannes; Sundh, John; Dupont, Chris L.; Allen, Andrew E.; McCrow, John P.; Celepli, Narin A.; Bergman, Birgitta; Ininbergs, Karolina; Ekman, Martin

    2016-01-01

    Metacaspases are distant homologs of metazoan caspase proteases, implicated in stress response, and programmed cell death (PCD) in bacteria and phytoplankton. While the few previous studies on metacaspases have relied on cultured organisms and sequenced genomes, no studies have focused on metacaspases in a natural setting. We here present data from the first microbial community-wide metacaspase survey; performed by querying metagenomic and metatranscriptomic datasets from the brackish Baltic Sea, a water body characterized by pronounced environmental gradients and periods of massive cyanobacterial blooms. Metacaspase genes were restricted to ~4% of the bacteria, taxonomically affiliated mainly to Bacteroidetes, Alpha- and Betaproteobacteria and Cyanobacteria. The gene abundance was significantly higher in larger or particle-associated bacteria (>0.8 μm), and filamentous Cyanobacteria dominated metacaspase gene expression throughout the bloom season. Distinct seasonal expression patterns were detected for the three metacaspase genes in Nodularia spumigena, one of the main bloom-formers. Clustering of normalized gene expression in combination with analyses of genomic and assembly data suggest functional diversification of these genes, and possible roles of the metacaspase genes related to stress responses, i.e., sulfur metabolism in connection to oxidative stress, and nutrient stress induced cellular differentiation. Co-expression of genes encoding metacaspases and nodularin toxin synthesis enzymes was also observed in Nodularia spumigena. The study shows that metacaspases represent an adaptation of potentially high importance for several key organisms in the Baltic Sea, most prominently Cyanobacteria, and open up for further exploration of their physiological roles in microbes and assessment of their ecological impact in aquatic habitats. PMID:27458440

  19. Drought sensitivity predicts habitat size sensitivity in an aquatic ecosystem.

    PubMed

    Amundrud, Sarah L; Srivastava, Diane S

    2015-07-01

    Species and trophic richness often increase with habitat size. Although many ecological processes have been evoked to explain both patterns, the environmental stress associated with small habitats has rarely been considered. We propose that larger habitats may be species rich simply because their environmental conditions are within the fundamental niche of more species; larger habitats may also have more trophic levels if traits of predators render them vulnerable to environmental stress. We test this hypothesis using the aquatic insect larvae in water-filled bromeliads. In bromeliads, the probability of desiccation is greatest in small plants. For the 10 most common bromeliad insect taxa, we ask whether differences in drought tolerance and regional abundances between taxa predict community and trophic composition over a gradient of bromeliad size. First, we used bromeliad survey data to calculate the mean habitat size of occurrence of each taxon. Comparing the observed mean habitat size of occurrence to that expected from random species assembly based on differences in their regional abundances allowed us to obtain habitat size sensitivity indices (as Z scores) for the various insect taxa. Second, we obtained drought sensitivity indices by subjecting individual insects to drought and measuring the effects on relative growth rates in a mesocosm experiment. We found that drought sensitivity strongly, predicts habitat size sensitivity in bromeliad insects. However, an increase in trophic richness with habitat size could not be explained by an increased sensitivity of predators to drought, but rather by sampling effects, as predators were rare compared to lower trophic levels. This finding suggests that physiological tolerance to environmental stress can be relevant in explaining the universal increase in species with habitat size. PMID:26378317

  20. Diversity and Expression of Bacterial Metacaspases in an Aquatic Ecosystem.

    PubMed

    Asplund-Samuelsson, Johannes; Sundh, John; Dupont, Chris L; Allen, Andrew E; McCrow, John P; Celepli, Narin A; Bergman, Birgitta; Ininbergs, Karolina; Ekman, Martin

    2016-01-01

    Metacaspases are distant homologs of metazoan caspase proteases, implicated in stress response, and programmed cell death (PCD) in bacteria and phytoplankton. While the few previous studies on metacaspases have relied on cultured organisms and sequenced genomes, no studies have focused on metacaspases in a natural setting. We here present data from the first microbial community-wide metacaspase survey; performed by querying metagenomic and metatranscriptomic datasets from the brackish Baltic Sea, a water body characterized by pronounced environmental gradients and periods of massive cyanobacterial blooms. Metacaspase genes were restricted to ~4% of the bacteria, taxonomically affiliated mainly to Bacteroidetes, Alpha- and Betaproteobacteria and Cyanobacteria. The gene abundance was significantly higher in larger or particle-associated bacteria (>0.8 μm), and filamentous Cyanobacteria dominated metacaspase gene expression throughout the bloom season. Distinct seasonal expression patterns were detected for the three metacaspase genes in Nodularia spumigena, one of the main bloom-formers. Clustering of normalized gene expression in combination with analyses of genomic and assembly data suggest functional diversification of these genes, and possible roles of the metacaspase genes related to stress responses, i.e., sulfur metabolism in connection to oxidative stress, and nutrient stress induced cellular differentiation. Co-expression of genes encoding metacaspases and nodularin toxin synthesis enzymes was also observed in Nodularia spumigena. The study shows that metacaspases represent an adaptation of potentially high importance for several key organisms in the Baltic Sea, most prominently Cyanobacteria, and open up for further exploration of their physiological roles in microbes and assessment of their ecological impact in aquatic habitats. PMID:27458440

  1. Overarching perspectives of contemporary and future ecosystems in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Wassmann, Paul

    2015-12-01

    The Arctic region has a number of specific characteristics that provide the region an exceptional global position. It comprises 5% of the earth surface, 1% of world ocean volume, 3% of world ocean area, 25% of world continental shelf, 35% of world coastline, 11% of global river runoff and 20 of worlds 100 longest rivers. The Arctic region encompasses only 0.05% of the global population, but 22% undiscovered petroleum, 15% of global petroleum production, many metals and non-metals resources and support major global fisheries (60 and 80°N). In times of increasing resource demand and limitation the world focuses increasingly onto the Arctic Ocean (AO) and adjacent regions. This development is emphasised by the recent awareness of rapid climate change in the AO, the most significant on the globe, and has resulted in increased attention to the oceanography of the high north. The loss of Arctic sea ice has emerged as a leading signal of global warming. It is taking place at a rate 2-3 times faster than global rates and sea-ice cover has decreased more than 10% per decade, while sea-ice volume may have been reduced by minimum 40% over the last 30 years (Meier et al., 2014). The reduction of ice cover and thickness makes the region available for commercial interest. The region drives also critical effects on the biophysical, political and economic system of the Northern Hemisphere (e.g., Grambling, 2015). These striking changes in physical forcing have left marine ecological footprints of climate change in the Arctic ecosystem (Wassmann et al., 2011). However, predicting the future of the pan-Arctic ecosystem remains a challenge not only because of the ever-accelerating nature of both physical and biological alterations, but also because of lack of marine ecological knowledge, that is staggering for the majority of regions (except the Barents, Chukchi and Beaufort seas).

  2. Staunton 1 reclamation demonstration project. Aquatic ecosystems. Final report

    SciTech Connect

    Vinikour, W. S.

    1981-02-01

    To provide long-term indications of the potential water quality improvements following reclamation efforts at the Staunton 1 Reclamation Demonstration Project, macroinvertebrates were collected from three on-site ponds and from the receiving stream (Cahokia Creek) for site drainage. Implications for potential benthic community differences resulting from site runoff were disclosed, but macroinvertebrate diversity throughout Cahokia Creek was limited due to an unstable, sandy substrate. The three ponds sampled were the New Pond, which was created as part of the reclamation activities; the Shed Pond, which and the Old Pond, which, because it was an existing, nonimpacted pond free of site runoff, served as a control. Comparisons of macroinvertebrates from the ponds indicated the potential for the New Pond to develop into a productive ecosystem. Macroinvertebrates in the New Pond were generally species more tolerant of acid mine drainage conditions. However, due to the present limited faunal densities and the undesirable physical and chemical characteristics of the New Pond, the pond should not be stocked with fish at this time.

  3. Human effects on ecological connectivity in aquatic ecosystems: Integrating scientific approaches to support management and mitigation.

    PubMed

    Crook, David A; Lowe, Winsor H; Allendorf, Frederick W; Erős, Tibor; Finn, Debra S; Gillanders, Bronwyn M; Hadwen, Wade L; Harrod, Chris; Hermoso, Virgilio; Jennings, Simon; Kilada, Raouf W; Nagelkerken, Ivan; Hansen, Michael M; Page, Timothy J; Riginos, Cynthia; Fry, Brian; Hughes, Jane M

    2015-11-15

    Understanding the drivers and implications of anthropogenic disturbance of ecological connectivity is a key concern for the conservation of biodiversity and ecosystem processes. Here, we review human activities that affect the movements and dispersal of aquatic organisms, including damming of rivers, river regulation, habitat loss and alteration, human-assisted dispersal of organisms and climate change. Using a series of case studies, we show that the insight needed to understand the nature and implications of connectivity, and to underpin conservation and management, is best achieved via data synthesis from multiple analytical approaches. We identify four key knowledge requirements for progressing our understanding of the effects of anthropogenic impacts on ecological connectivity: autecology; population structure; movement characteristics; and environmental tolerance/phenotypic plasticity. Structuring empirical research around these four broad data requirements, and using this information to parameterise appropriate models and develop management approaches, will allow for mitigation of the effects of anthropogenic disturbance on ecological connectivity in aquatic ecosystems. PMID:25917446

  4. ANN application for prediction of atmospheric nitrogen deposition to aquatic ecosystems.

    PubMed

    Palani, Sundarambal; Tkalich, Pavel; Balasubramanian, Rajasekhar; Palanichamy, Jegathambal

    2011-06-01

    The occurrences of increased atmospheric nitrogen deposition (ADN) in Southeast Asia during smoke haze episodes have undesired consequences on receiving aquatic ecosystems. A successful prediction of episodic ADN will allow a quantitative understanding of its possible impacts. In this study, an artificial neural network (ANN) model is used to estimate atmospheric deposition of total nitrogen (TN) and organic nitrogen (ON) concentrations to coastal aquatic ecosystems. The selected model input variables were nitrogen species from atmospheric deposition, Total Suspended Particulates, Pollutant Standards Index and meteorological parameters. ANN models predictions were also compared with multiple linear regression model having the same inputs and output. ANN model performance was found relatively more accurate in its predictions and adequate even for high-concentration events with acceptable minimum error. The developed ANN model can be used as a forecasting tool to complement the current TN and ON analysis within the atmospheric deposition-monitoring program in the region. PMID:21481425

  5. Possible Limiting Nutrient Factor in Long Term Operation of Closed Aquatic Ecosystem

    NASA Astrophysics Data System (ADS)

    Hao, Zongjie; Wang, Gaohong; Liu, Yongding

    A lab mini-module of Closed Aquatic Ecosystem consisting of Chlorella pyrenoidosa and Bulinus australianus was constructed to study the effect of nutrient limitation on long term operation. A series of tests were taken, the first introduced was consumer part Bulinus australianus, the second nutrient introduced was inorganic carbon source, organic carbon source glucose was injected into a third set of the systems, The fourth one is Chlorella pyrenoidosa only, acting as the control.Results showed the one with Bulinus australianus came to a steady state 17 days after closure, and algae in those introduced carbon source grew better than monoculture. It is inferred that nutrient limitation is inevitable in Long term operation of Closed Aquatic Ecosystem, especially carbon which is partly restored as carbon pool is out of element cycle.

  6. Ecosystem model intercomparison of under-ice and total primary production in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Jin, Meibing; Popova, Ekaterina E.; Zhang, Jinlun; Ji, Rubao; Pendleton, Daniel; Varpe, Øystein; Yool, Andrew; Lee, Younjoo J.

    2016-01-01

    Previous observational studies have found increasing primary production (PP) in response to declining sea ice cover in the Arctic Ocean. In this study, under-ice PP was assessed based on three coupled ice-ocean-ecosystem models participating in the Forum for Arctic Modeling and Observational Synthesis (FAMOS) project. All models showed good agreement with under-ice measurements of surface chlorophyll-a concentration and vertically integrated PP rates during the main under-ice production period, from mid-May to September. Further, modeled 30-year (1980-2009) mean values and spatial patterns of sea ice concentration compared well with remote sensing data. Under-ice PP was higher in the Arctic shelf seas than in the Arctic Basin, but ratios of under-ice PP over total PP were spatially correlated with annual mean sea ice concentration, with higher ratios in higher ice concentration regions. Decreases in sea ice from 1980 to 2009 were correlated significantly with increases in total PP and decreases in the under-ice PP/total PP ratio for most of the Arctic, but nonsignificantly related to under-ice PP, especially in marginal ice zones. Total PP within the Arctic Circle increased at an annual rate of between 3.2 and 8.0 Tg C/yr from 1980 to 2009. This increase in total PP was due mainly to a PP increase in open water, including increases in both open water area and PP rate per unit area, and therefore much stronger than the changes in under-ice PP. All models suggested that, on a pan-Arctic scale, the fraction of under-ice PP declined with declining sea ice cover over the last three decades.

  7. Effects of future land use on biogeography of aquatic ecosystems of Amazonia

    NASA Astrophysics Data System (ADS)

    Howard, E. A.; Coe, M. T.; Foley, J. A.; Costa, M. H.

    2006-12-01

    Amazonian ecosystems provide key ecosystem services, such as regulating the amount and timing of water and carbon flows through the Amazon Basin. Land use in these ecosystems affects regional water balance, which in turn affects biogeography of aquatic ecosystems, including wetlands and floodplains. We combined a hydrological model (Terrestrial Hydrology Model with Biogeochemistry, THMB), remote sensing observations (Hess et al. 2003), and empirical data to identify the distribution of aquatic biogeographic types throughout the central Amazon basin over time. We explored how future land-use scenarios for the Amazon Basin through 2030 (Soares-Filho et al. 2004) would modify the spatial and temporal patterns of aquatic ecosystems as compared to a baseline of natural potential vegetation cover under historical climate variability for the 20th century. We calibrated monthly simulation results with remotely sensed observations of flooded area and extent of different wetland categories for high and low water periods over a 1.7 million sq. km region of the central Amazon. Two additional dimensions of floodplain biogeography (river size and color) were added to provide insight into the geographic distribution of key ecosystem types and their flooding seasonality. For historical conditions, the model results reproduced regional differences in seasonal flood extent and timing north and south of the Amazon mainstem, reflecting the dominant climatic regimes. Black-water streams and medium-sized rivers, followed by large white-water rivers, were the most extensive types across the study region. However much of the black water was in areas likely to be influenced by white-water rivers while flooded. The monthly extent of flooded areas dominated by woody vegetation was consistently more strongly seasonal than non-woody areas. Also, the extent of flooding in muddy and semi-muddy rivers and floodplains tended to be more highly seasonal than in black- and clear-water areas. We

  8. Diverging Plant and Ecosystem Strategies in Response to Climate Change in the High Arctic

    NASA Astrophysics Data System (ADS)

    Maseyk, K. S.; Welker, J. M.; Czimczik, C. I.; Lupascu, M.; Lett, C.; Seibt, U. H.

    2014-12-01

    Increasing summer precipitation means Arctic growing seasons are becoming wetter as well as warmer, but the effect of these coupled changes on tundra ecosystem functioning remains largely unknown. We have determined how warmer and wetter summers affect coupled carbon-water cycling in a High Arctic polar semi-desert ecosystem in NW Greenland. Measurements of ecosystem CO2 and water fluxes throughout the growing season and leaf ecophysiological traits (gas exchange, morphology, leaf chemistry) were made at a long-term climate change experiment. After 9 years of exposure to warmer (+ 4°C) and / or wetter (+ 50% precipitation) treatments, we found diverging plant strategies between the responses to warming with or without an increase in summer precipitation. Warming alone resulted in an increase in leaf nitrogen, mesophyll conductance and leaf-mass per area and higher rates of leaf-level photosynthesis, but with warming and wetting combined leaf traits remain largely unchanged. However, total leaf area increased with warming plus wetting but was unchanged with warming alone. The combined effect of these leaf trait and canopy adjustments is a decrease in ecosystem water-use efficiency (the ratio of net productivity to evapotranspiration) with warming only, but a substantial increase with combined warming and wetting. We conclude that increasing summer precipitation will alter tundra ecohydrological responses to warming; that leaf-level changes in ecophysiological traits have an upward cascading consequence for ecosystem and land surface-climate interactions; and the current relative resistance of High Arctic ecosystems to warming may mask biochemical and carbon cycling changes already underway.

  9. Selenium biotransformations in an engineered aquatic ecosystem for bioremediation of agricultural wastewater via brine shrimp production.

    PubMed

    Schmidt, Radomir; Tantoyotai, Prapakorn; Fakra, Sirine C; Marcus, Matthew A; Yang, Soo In; Pickering, Ingrid J; Bañuelos, Gary S; Hristova, Krassimira R; Freeman, John L

    2013-05-21

    An engineered aquatic ecosystem was specifically designed to bioremediate selenium (Se), occurring as oxidized inorganic selenate from hypersalinized agricultural drainage water while producing brine shrimp enriched in organic Se and omega-3 and omega-6 fatty acids for use in value added nutraceutical food supplements. Selenate was successfully bioremediated by microalgal metabolism into organic Se (seleno-amino acids) and partially removed via gaseous volatile Se formation. Furthermore, filter-feeding brine shrimp that accumulated this organic Se were removed by net harvest. Thriving in this engineered pond system, brine shrimp ( Artemia franciscana Kellogg) and brine fly (Ephydridae sp.) have major ecological relevance as important food sources for large populations of waterfowl, breeding, and migratory shore birds. This aquatic ecosystem was an ideal model for study because it mimics trophic interactions in a Se polluted wetland. Inorganic selenate in drainage water was metabolized differently in microalgae, bacteria, and diatoms where it was accumulated and reduced into various inorganic forms (selenite, selenide, or elemental Se) or partially incorporated into organic Se mainly as selenomethionine. Brine shrimp and brine fly larva then bioaccumulated Se from ingesting aquatic microorganisms and further metabolized Se predominately into organic Se forms. Importantly, adult brine flies, which hatched from aquatic larva, bioaccumulated the highest Se concentrations of all organisms tested. PMID:23621086

  10. Time series analysis and the analysis of aquatic and riparian ecosystems

    USGS Publications Warehouse

    Milhous, R.T.

    2003-01-01

    Time series analysis of physical instream habitat and the riparian zone is not done as frequently as would be beneficial in understanding the fisheries aspects of the aquatic ecosystem. This paper presents two case studies have how time series analysis may be accomplished. Time series analysis is the analysis of the variation of the physical habitat or the hydro-period in the riparian zone (in many situations, the floodplain).

  11. K-Pg events facilitated lineage transitions between terrestrial and aquatic ecosystems.

    PubMed

    Procheş, Serban; Polgar, Gianluca; Marshall, David J

    2014-06-01

    We use dated phylogenetic trees for tetrapod vertebrates to identify lineages that shifted between terrestrial and aquatic ecosystems in terms of feeding or development, and to assess the timing of such events. Both stem and crown lineage ages indicate a peak in transition events in correspondence with the K-Pg mass extinction. This meets the prediction that changes in competitive pressure and resource availability following mass extinction events should facilitate such transitions. PMID:24919699

  12. Arctic ecosystem functional zones: identification and quantification using an above and below ground monitoring strategy

    NASA Astrophysics Data System (ADS)

    Hubbard, Susan S.; Ajo-Franklin, Jonathan B.; Dafflon, Baptiste; Dou, Shan; Kneafsey, Tim J.; Peterson, John E.; Tas, Neslihan; Torn, Margaret S.; Phuong Tran, Anh; Ulrich, Craig; Wainwright, Haruko; Wu, Yuxin; Wullschleger, Stan

    2015-04-01

    Although accurate prediction of ecosystem feedbacks to climate requires characterization of the properties that influence terrestrial carbon cycling, performing such characterization is challenging due to the disparity of scales involved. This is particularly true in vulnerable Arctic ecosystems, where microbial activities leading to the production of greenhouse gasses are a function of small-scale hydrological, geochemical, and thermal conditions influenced by geomorphology and seasonal dynamics. As part of the DOE Next-Generation Ecosystem Experiment (NGEE-Arctic), we are advancing two approaches to improve the characterization of complex Arctic ecosystems, with an initial application to an ice-wedge polygon dominated tundra site near Barrow, AK, USA. The first advance focuses on developing a new strategy to jointly monitor above- and below- ground properties critical for carbon cycling in the tundra. The strategy includes co-characterization of properties within the three critical ecosystem compartments: land surface (vegetation, water inundation, snow thickness, and geomorphology); active layer (peat thickness, soil moisture, soil texture, hydraulic conductivity, soil temperature, and geochemistry); and permafrost (mineral soil and ice content, nature, and distribution). Using a nested sampling strategy, a wide range of measurements have been collected at the study site over the past three years, including: above-ground imagery (LiDAR, visible, near infrared, NDVI) from various platforms, surface geophysical datasets (electrical, electromagnetic, ground penetrating radar, seismic), and point measurements (such as CO2 and methane fluxes, soil properties, microbial community composition). A subset of the coincident datasets is autonomously collected daily. Laboratory experiments and new inversion approaches are used to improve interpretation of the field geophysical datasets in terms of ecosystem properties. The new strategy has significantly advanced our ability

  13. Modeling Active Layer and Permafrost Dynamics of Ice Wedge Polygon Dominated Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Kumar, J.; Bisht, G.; Liljedahl, A.; Mills, R. T.; Karra, S.; Painter, S. L.; Thornton, P. E.

    2013-12-01

    Permafrost soils contains vast stock of frozen organic carbon. As warming climate accelerates the thaw of the permafrost, increasing amount of organic matter is exposed to respiration leading to release of carbon to the atmosphere in the form of CO2 and CH4 . Permafrost thermal dynamics play a key role influencing hydrologic and biogeochemical processes in these ecosystems. Large areas of Arctic landscape are covered by the patterned ground features created by repeated freezing and thawing of soil underlain by aerially continuous permafrost. These microtopographic features in the landscape controls the local surface-subsurface hydrology and thermal regimes through differential transport of heat and water. Study of these interacting thermal-hydrologic-biogeochemical in permafrost soils are further complicated by the complex topography and heterogeneity of subsurface. We have developed and applied a coupled multiscale-multiphase-multicomponent surface-subsurface flow and reactive transport model PFLOTRAN for modeling of thermal-hydrologic-biogeochemical processes in permafrost soils. We study the permafrost thermal dynamics, role of microtopography in local scale hydrology at the Department of Energy's Next Generation Ecosystem Experiment (NGEE) - Arctic field sites near Barrow, Alaska. High resolution LiDAR data is used to represent the microtopography at sub-meter resolution in PFLOTRAN. Long term simulations have been conducted at the field sites informed by the observations from field and laboratory campaigns to study and understand the hydrologic and biogeochemical processes in these Arctic ecosystems.

  14. Two mechanisms of aquatic and terrestrial habitat change along an Alaskan Arctic coastline

    USGS Publications Warehouse

    Arp, Christopher D.; Jones, Benjamin M.; Schmutz, Joel A.; Urban, Frank E.; Jorgenson, M. Torre

    2010-01-01

    Arctic habitats at the interface between land and sea are particularly vulnerable to climate change. The northern Teshekpuk Lake Special Area (N-TLSA), a coastal plain ecosystem along the Beaufort Sea in northern Alaska, provides habitat for migratory waterbirds, caribou, and potentially, denning polar bears. The 60-km coastline of N-TLSA is experiencing increasing rates of coastline erosion and storm surge flooding far inland resulting in lake drainage and conversion of freshwater lakes to estuaries. These physical mechanisms are affecting upland tundra as well. To better understand how these processes are affecting habitat, we analyzed long-term observational records coupled with recent short-term monitoring. Nearly the entire coastline has accelerating rates of erosion ranging from 6 m/year from 1955 to 1979 and most recently peaking at 17 m/year from 2007 to 2009, yet an intensive monitoring site along a higher bluff (3–6 masl) suggested high interannual variability. The frequency and magnitude of storm events appears to be increasing along this coastline and these patterns correspond to a greater number of lake tapping and flooding events since 2000. For the entire N-TLSA, we estimate that 6% of the landscape consists of salt-burned tundra, while 41% is prone to storm surge flooding. This offset may indicate the relative frequency of low-magnitude flood events along the coastal fringe. Monitoring of coastline lakes confirms that moderate westerly storms create extensive flooding, while easterly storms have negligible effects on lakes and low-lying tundra. This study of two interacting physical mechanisms, coastal erosion and storm surge flooding, provides an important example of the complexities and data needs for predicting habitat change and biological responses along Arctic land–ocean interfaces.

  15. EcoCasting: Using NetLogo models of aquatic ecosystems to teach scientific inquiry

    NASA Astrophysics Data System (ADS)

    Buzby, C. K.; Jona, K.

    2010-12-01

    The EcoCasting project from the Office of STEM Education Partnerships (OSEP) at Northwestern University has developed a computer model-based curriculum for high school environmental science classes to study complexity in aquatic ecosystems. EcoCasting aims to deliver cutting edge scientific research on bioaccumulation in invaded Great Lakes food webs to high school classes. Scientists and environmental engineers at Northwestern are investigating unusual bioaccumulation patterns in invaded food webs of the Great Lakes. High school students are exploring this authentic data to understand what is causing the anomalies in the data. Students use a series of NetLogo agent-based models of an aquatic ecosystem to study how toxins accumulate in the food web. Using these models, students learn about predator-prey relationships, bioaccumulation, and invasive species. Students are confronted with contradictory data collected by scientists and investigate alternative food web mechanisms at work. By studying the individual variables, students learn common scientific principles. When multiple variables are combined in a unifying model, students learn that the interactions lead to unexpected outcomes. Students learn about the complexity of the ecosystem and gain proficiency interpreting computer models and scientific data collection in this curriculum. Model of aquatic food chain

  16. Possible nutrient limiting factor in long term operation of closed aquatic ecosystem

    NASA Astrophysics Data System (ADS)

    Hao, Zongjie; Li, Yanhui; Cai, Wenkai; Wu, Peipei; Liu, Yongding; Wang, Gaohong

    2012-03-01

    To investigate nutrient limitation effect on the community metabolism of closed aquatic ecosystem and possible nutrient limiting factors in the experimental food chains, depletion of inorganic chemicals including carbon, nitrogen and phosphorous was tested. A closed aquatic ecosystem lab module consisting of Chlorella pyrenoidosa and Chlamydomonas reinhardtii, Daphnia magna and associated unidentified microbes was established. Closed ecological systems receive no carbon dioxide; therefore, we presumed carbon as a first limiting factor. The results showed that the algae population in the nutrient saturated group was statistically higher than that in the nutrient limited groups, and that the chlorophyll a content of algae in the phosphorus limited group was the highest among the limited groups. However, the nitrogen limited group supported the most Daphnia, followed by the carbon limited group, the nutrient saturated group and the phosphorus limited group. Redundancy analysis showed that the total phosphorus contents were correlated significantly with the population of algae, and that the amount of soluble carbohydrate as feedback of nutrient depletion was correlated with the number of Daphnia. Thus, these findings suggest that phosphorus is the limiting factor in the operation of closed aquatic ecosystem. The results presented herein have important indications for the future construction of long term closed ecological system.

  17. Environmental fate and biodegradability of benzene derivatives as studied in a model aquatic ecosystem.

    PubMed Central

    Lu, P Y; Metcalf, R L

    1975-01-01

    A model aquatic ecosystem is devised for studying relatively volatile organic compounds and simulating direct discharge of chemical wastes into aquatic ecosystems. Six simple benzene derivatives (aniline, anisole, benzoic acid, chlorobenzene, nitrobenzene, and phthalic anhydride) and other important specialty chemicals: hexachlorobenzene, pentachlorophenol, 2,6-diethylaniline, and 3,5,6-trichloro-2-pyridinol were also chosen for study of environmental behavior and fate in the model aquatic ecosystem. Quantitative relationships of the intrinsic molecular properties of the environmental micropollutants with biological responses are established, e.g., water solubility, partition coefficient, pi constant, sigma constant, ecological magnification, biodegradability index, and comparative detoxication mechanisms, respectively. Water solubility, pi constant, and sigma constant are the most significant factors and control the biological responses of the food chain members. Water solubility and pi constant control the degree of bioaccumulation, and sigma constant limits the metabolism of the xenobiotics via microsomal detoxication enzymes. These highly significant correlations should be useful for predicting environmental fate of organic chemicals. PMID:1157796

  18. Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment.

    PubMed

    Camargo, Julio A; Alonso, Alvaro

    2006-08-01

    We provide a global assessment, with detailed multi-scale data, of the ecological and toxicological effects generated by inorganic nitrogen pollution in aquatic ecosystems. Our synthesis of the published scientific literature shows three major environmental problems: (1) it can increase the concentration of hydrogen ions in freshwater ecosystems without much acid-neutralizing capacity, resulting in acidification of those systems; (2) it can stimulate or enhance the development, maintenance and proliferation of primary producers, resulting in eutrophication of aquatic ecosystems; (3) it can reach toxic levels that impair the ability of aquatic animals to survive, grow and reproduce. Inorganic nitrogen pollution of ground and surface waters can also induce adverse effects on human health and economy. Because reductions in SO2 emissions have reduced the atmospheric deposition of H2SO4 across large portions of North America and Europe, while emissions of NOx have gone unchecked, HNO3 is now playing an increasing role in the acidification of freshwater ecosystems. This acidification process has caused several adverse effects on primary and secondary producers, with significant biotic impoverishments, particularly concerning invertebrates and fishes, in many atmospherically acidified lakes and streams. The cultural eutrophication of freshwater, estuarine, and coastal marine ecosystems can cause ecological and toxicological effects that are either directly or indirectly related to the proliferation of primary producers. Extensive kills of both invertebrates and fishes are probably the most dramatic manifestation of hypoxia (or anoxia) in eutrophic and hypereutrophic aquatic ecosystems with low water turnover rates. The decline in dissolved oxygen concentrations can also promote the formation of reduced compounds, such as hydrogen sulphide, resulting in higher adverse (toxic) effects on aquatic animals. Additionally, the occurrence of toxic algae can significantly

  19. Changing snow cover in tundra ecosystems tips the Arctic carbon balance

    NASA Astrophysics Data System (ADS)

    Zona, D.; Hufkens, K.; Gioli, B.; Kalhori, A. A. M.; Oechel, W. C.

    2014-12-01

    The Arctic environment has witnessed important changes due to global warming, resulting in increased surface air temperatures and rain events which both exacerbate snow cover deterioration (Semmens et al, 2013; Rennert et al, 2009; White et al, 2007; Min et al, 2008; Sharp et al, 2013; Schaeffer et al, 2013). Snow cover duration is declining by almost 20% per decade, a far higher rate than model estimates (Derksen and Brown, 2012). Concomitant with increasing temperatures and decreasing snow cover duration, the length of the arctic growing season is reported to have increased by 1.1 - 4.9 days per decade since 1951 (Menzel et al, 2006), and, plant productivity and CO2 uptake from arctic vegetation are strongly influenced by changes in growing season length (Myneni et al., 1997; Schaefer et al., 2005; Euskirchen et al., 2006). Based on more than a decade of eddy flux measurements in Arctic tundra ecosystems across the North slope of Alaska, and remotely sensed snow cover data, we show that earlier snow melt in the spring increase C uptake while an extended snow free period in autumn is associated with a higher C loss. Here we present the impacts of changes in snow cover dynamics between spring and autumn in arctic tundra ecosystems on the carbon dynamics and net C balance of the Alaskan Arctic. ReferencesDerksen, C., Brown R. (2012) Geophys. Res. Lett., doi:10.1029/2012GL053387 Euskirchen, E.S., et al. (2006) Glob. Change Biol., 12, 731-750. Menzel, A., et al. 2006. Glob. Change Biol., 12, 1969-1976. Min SK, Zhang X, Zweirs F (2008) Science 320: 518-520. Rennert K J, Roe G, Putkonen J and Bitz C M (2009) J. Clim. 22 2302-15. Schaefer, K., Denning A.S., Leonard O. (2005) Global Biogeochem. Cycles, 19, GB3017. Schaeffer, S. M., Sharp, E., Schimel, J. P. & Welker, J. M. (2013). Soil- plant N processes in a High Arctic ecosystem, NW Greenland are altered by long-term experimental warming and higher rainfall. Glob. Change Biol., 11, 3529-39. doi: 10.1111/gcb.12318

  20. Measurement-based upscaling of Pan Arctic Net Ecosystem Exchange: the PANEEx project

    NASA Astrophysics Data System (ADS)

    Njuabe Mbufong, Herbert; Kusbach, Antonin; Lund, Magnus; Persson, Andreas; Christensen, Torben R.; Tamstorf, Mikkel P.; Connolly, John

    2016-04-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) can be attributed to the high spatial heterogeneity of Arctic tundra due to the complex topography. Current models of C exchange handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple pan Arctic NEE (PANEEx) model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide (CO2) data from 12 Arctic tundra sites. The model input parameters (Fcsat, Rd and α) were estimated as a function of air temperature (AirT) and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship, including the saturation flux, dark respiration and initial light use efficiency, respectively. LAI and air temperature were respectively estimated from empirical relationships with remotely sensed normalized difference vegetation index (NDVI) and land surface temperature (LST). These are available as MODIS Terra product MOD13Q1 and MOD11A1 respectively. Therefore, no specific knowledge of the vegetation type is required. The PANEEx model captures the spatial heterogeneity of the Arctic tundra and was effective in simulating 77% of the measured fluxes (r2 = 0.72, p < 0.001) at the 12 sites used in the calibration of the model. Further, the model effectively estimates NEE in three disparate Alaskan ecosystems (heath, tussock and fen) with an estimation ranging between 10 - 36% of the measured fluxes. We suggest that the poor agreement between the measured and modeled NEE may result from the disparity between ground-based measured LAI (used in model calibration) and remotely sensed LAI (estimated from NDVI and used in NEE estimation). Moreover, our results suggests that using simple linear regressions may be inadequate as parameters estimated

  1. Field flume reveals aquatic vegetation's role in sediment and particulate phosphorus transport in a shallow aquatic ecosystem

    NASA Astrophysics Data System (ADS)

    Harvey, Judson W.; Noe, Gregory B.; Larsen, Laurel G.; Nowacki, Daniel J.; McPhillips, Lauren E.

    2011-03-01

    Flow interactions with aquatic vegetation and effects on sediment transport and nutrient redistribution are uncertain in shallow aquatic ecosystems. Here we quantified sediment transport in the Everglades by progressively increasing flow velocity in a field flume constructed around undisturbed bed sediment and emergent macrophytes. Suspended sediment < 100 μm was dominant in the lower range of laminar flow and was supplied by detachment from epiphyton. Sediment flux increased by a factor of four and coarse flocculent sediment > 100 μm became dominant at higher velocity steps after a threshold shear stress for bed floc entrainment was exceeded. Shedding of vortices that had formed downstream of plant stems also occurred on that velocity step which promoted additional sediment detachment from epiphyton. Modeling determined that the potentially entrainable sediment reservoir, 46 g m - 2 , was similar to the reservoir of epiphyton (66 g m - 2 ) but smaller than the reservoir of flocculent bed sediment (330 g m - 2 ). All suspended sediment was enriched in phosphorus (by approximately twenty times) compared with bulk sediment on the bed surface and on plant stems, indicating that the most easily entrainable sediment is also the most nutrient rich (and likely the most biologically active).

  2. Field flume reveals aquatic vegetation's role in sediment and particulate phosphorus transport in a shallow aquatic ecosystem

    USGS Publications Warehouse

    Harvey, J.W.; Noe, G.B.; Larsen, L.G.; Nowacki, D.J.; McPhillips, L.E.

    2011-01-01

    Flow interactions with aquatic vegetation and effects on sediment transport and nutrient redistribution are uncertain in shallow aquatic ecosystems. Here we quantified sediment transport in the Everglades by progressively increasing flow velocity in a field flume constructed around undisturbed bed sediment and emergent macrophytes. Suspended sediment 100 μm became dominant at higher velocity steps after a threshold shear stress for bed floc entrainment was exceeded. Shedding of vortices that had formed downstream of plant stems also occurred on that velocity step which promoted additional sediment detachment from epiphyton. Modeling determined that the potentially entrainable sediment reservoir, 46 g m−2, was similar to the reservoir of epiphyton (66 g m−2) but smaller than the reservoir of flocculent bed sediment (330 g m−2). All suspended sediment was enriched in phosphorus (by approximately twenty times) compared with bulk sediment on the bed surface and on plant stems, indicating that the most easily entrainable sediment is also the most nutrient rich (and likely the most biologically active).

  3. Aquatic Ecosystems, Water Quality, and Global Change: Challenges of conducting Multi-Stressor Vulnerability Assessments (External Review Draft)

    EPA Science Inventory

    This draft report investigates the issues and challenges associated with identifying, calculating, and mapping indicators of the relative vulnerability of water quality and aquatic ecosystems, across the United States, to the potential impacts of global change. Using a large set...

  4. Approach for Developing a National Atlas of Vulnerabilities for U.S. Water Quality and Aquatic Ecosystems

    EPA Science Inventory

    The purpose of the Atlas project is to support national- and regional-scale water quality and aquatic ecosystem vulnerability assessments by providing quantitative information on the relative vulnerability to climate change of different geographic regions and watershed systems ac...

  5. A REVIEW OF SINGLE SPECIES TOXICITY TESTS: ARE THE TESTS RELIABLE PREDICTORS OF AQUATIC ECOSYSTEM COMMUNITY RESPONSES?

    EPA Science Inventory

    This document provides a comprehensive review to evaluate the reliability of indicator species toxicity test results in predicting aquatic ecosystem impacts, also called the ecological relevance of laboratory single species toxicity tests.

  6. IMPACT OF HIGH CHEMICAL CONTAMINANT CONCENTRATIONS ON TERRESTRIAL AND AQUATIC ECOSYSTEMS: A STATE-OF-THE-ART REVIEW

    EPA Science Inventory

    The state-of-the-art of available methods for predicting the effects of high chemical concentrations on the properties, processes, functions, cycles, and responses of terrestrial and aquatic ecosystems was reviewed. Environmental problems associated with high chemical concentrati...

  7. Aquatic ecosystem protection and restoration: Advances in methods for assessment and evaluation

    USGS Publications Warehouse

    Bain, M.B.; Harig, A.L.; Loucks, D.P.; Goforth, R.R.; Mills, K.E.

    2000-01-01

    Many methods and criteria are available to assess aquatic ecosystems, and this review focuses on a set that demonstrates advancements from community analyses to methods spanning large spatial and temporal scales. Basic methods have been extended by incorporating taxa sensitivity to different forms of stress, adding measures linked to system function, synthesizing multiple faunal groups, integrating biological and physical attributes, spanning large spatial scales, and enabling simulations through time. These tools can be customized to meet the needs of a particular assessment and ecosystem. Two case studies are presented to show how new methods were applied at the ecosystem scale for achieving practical management goals. One case used an assessment of biotic structure to demonstrate how enhanced river flows can improve habitat conditions and restore a diverse fish fauna reflective of a healthy riverine ecosystem. In the second case, multitaxonomic integrity indicators were successful in distinguishing lake ecosystems that were disturbed, healthy, and in the process of restoration. Most methods strive to address the concept of biological integrity and assessment effectiveness often can be impeded by the lack of more specific ecosystem management objectives. Scientific and policy explorations are needed to define new ways for designating a healthy system so as to allow specification of precise quality criteria that will promote further development of ecosystem analysis tools.

  8. Exploring the Use of Participatory Information to Improve Monitoring, Mapping and Assessment of Aquatic Ecosystem Services at Landascape Scales

    EPA Science Inventory

    Traditionally, the EPA has monitored aquatic ecosystems using statistically rigorous sample designs and intensive field efforts which provide high quality datasets. But by their nature they leave many aquatic systems unsampled, follow a top down approach, have a long lag between ...

  9. LINKING COMMUNITY STRUCTURE AND ECOSYSTEM FUNCTION IN AQUATIC ECOSYSTEMS DEGRADED BY MOUNTAINTOP MINING

    EPA Science Inventory

    The Clean Water Act and its subsequent amendments recognize the importance of protecting biological integrity, a concept synonymous with preserving structure and function within lotic ecosystems. This research will improve current taxonomically based risk assessment models,...

  10. Transitions in Arctic ecosystems: Ecological implications of a changing hydrological regime

    NASA Astrophysics Data System (ADS)

    Wrona, Frederick J.; Johansson, Margareta; Culp, Joseph M.; Jenkins, Alan; Mârd, Johanna; Myers-Smith, Isla H.; Prowse, Terry D.; Vincent, Warwick F.; Wookey, Philip A.

    2016-03-01

    Numerous international scientific assessments and related articles have, during the last decade, described the observed and potential impacts of climate change as well as other related environmental stressors on Arctic ecosystems. There is increasing recognition that observed and projected changes in freshwater sources, fluxes, and storage will have profound implications for the physical, biogeochemical, biological, and ecological processes and properties of Arctic terrestrial and freshwater ecosystems. However, a significant level of uncertainty remains in relation to forecasting the impacts of an intensified hydrological regime and related cryospheric change on ecosystem structure and function. As the terrestrial and freshwater ecology component of the Arctic Freshwater Synthesis, we review these uncertainties and recommend enhanced coordinated circumpolar research and monitoring efforts to improve quantification and prediction of how an altered hydrological regime influences local, regional, and circumpolar-level responses in terrestrial and freshwater systems. Specifically, we evaluate (i) changes in ecosystem productivity; (ii) alterations in ecosystem-level biogeochemical cycling and chemical transport; (iii) altered landscapes, successional trajectories, and creation of new habitats; (iv) altered seasonality and phenological mismatches; and (v) gains or losses of species and associated trophic interactions. We emphasize the need for developing a process-based understanding of interecosystem interactions, along with improved predictive models. We recommend enhanced use of the catchment scale as an integrated unit of study, thereby more explicitly considering the physical, chemical, and ecological processes and fluxes across a full freshwater continuum in a geographic region and spatial range of hydroecological units (e.g., stream-pond-lake-river-near shore marine environments).

  11. An eddy covariance derived annual carbon budget for an arctic terrestrial ecosystem (Disko, Greenland)

    NASA Astrophysics Data System (ADS)

    McConnell, Alistair; Lund, Magnus; Friborg, Thomas

    2016-04-01

    Ecosystems with underlying permafrost cover nearly 25% of the ice-free land area in the northern hemisphere and store almost half of the global soil carbon. Future climate changes are predicted to have the most pronounced effect in northern latitudes. These Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost. This will impact global climate through the mobilization of carbon and nitrogen accompanied by release of greenhouses gases, including carbon dioxide. This study presents the initial findings and first full annual carbon (CO2) budget, derived from eddy covariance measurements, for an Arctic landscape in West Greenland. The study site, a terrestrial Arctic maritime climate, is located at Østerlien, near Qeqertarsuaq, on the southern coast of Disko Island in central West Greenland (69° 15' N, 53° 34' W) within the transition zone from continuous to discontinuous permafrost. The mean annual air temperature is -5 C and the annual precipitation as rain is 150-200 mm. Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. This is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interactions of microorganisms, vegetation and soil. The eddy covariance method allows us to interrogate the processes and drivers of land-atmosphere carbon exchange at extremely high temporary frequency (10 Hz), providing landscape-scale measurements of CO2, H2O and heat fluxes for the site, which are processed to derive daily, monthly and now, annual carbon fluxes. We discuss the scientific methodology, challenges, and analysis, as well as the practical and logistic challenges of working in the Arctic, and present an annual carbon budget

  12. Seasonal dynamics of bacterial biomass and production in a coastal arctic ecosystem: Franklin Bay, western Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Garneau, Marie-Ã. Ve; Roy, SéBastien; Lovejoy, Connie; Gratton, Yves; Vincent, Warwick F.

    2008-07-01

    The Canadian Arctic Shelf Exchange Study (CASES) included the overwintering deployment of a research platform in Franklin Bay (70°N, 126°W) and provided a unique seasonal record of bacterial dynamics in a coastal region of the Arctic Ocean. Our objectives were (1) to relate seasonal bacterial abundance (BA) and production (BP) to physico-chemical characteristics and (2) to quantify the annual bacterial carbon flux. BA was estimated by epifluorescence microscopy and BP was estimated from 3H-leucine and 3H-thymidine assays. Mean BA values for the water column ranged from 1.0 (December) to 6.8 × 105 cells mL-1 (July). Integral BP varied from 1 (February) to 80 mg C m-2 d-1 (July). During winter-spring, BP was uncorrelated with chlorophyll a (Chl a), but these variables were significantly correlated during summer-autumn (rs = 0.68, p < 0.001, N = 38), suggesting that BP was subject to bottom-up control by carbon supply. Integrated BP data showed three distinct periods: fall-winter, late winter-late spring, and summer. A baseline level of BB and BP was maintained throughout late winter-late spring despite the persistent cold and darkness, with irregular fluctuations that may be related to hydrodynamic events. During this period, BP rates were correlated with colored dissolved organic matter (CDOM) but not Chl a (rs BP.CDOM∣Chl a = 0.20, p < 0.05, N = 176). Annual BP was estimated as 6 g C m-2 a-1, implying a total BP of 4.8 × 1010 g C a-1 for the Franklin Bay region. These results show that bacterial processes continue throughout all seasons and make a large contribution to the total biological carbon flux in this coastal arctic ecosystem.

  13. Aquatic Ecosystem Response to Timber Harvesting for the Purpose of Restoring Aspen

    PubMed Central

    Jones, Bobette E.; Krupa, Monika; Tate, Kenneth W.

    2013-01-01

    The removal of conifers through commercial timber harvesting has been successful in restoring aspen, however many aspen stands are located near streams, and there are concerns about potential aquatic ecosystem impairment. We examined the effects of management-scale conifer removal from aspen stands located adjacent to streams on water quality, solar radiation, canopy cover, temperature, aquatic macroinvertebrates, and soil moisture. This 8-year study (2003–2010) involved two projects located in Lassen National Forest. The Pine-Bogard Project consisted of three treatments adjacent to Pine and Bogard Creeks: (i) Phase 1 in January 2004, (ii) Phase 2 in August 2005, and (iii) Phase 3 in January 2008. The Bailey Project consisted of one treatment adjacent to Bailey Creek in September 2006. Treatments involved whole tree removal using track-laying harvesters and rubber tire skidders. More than 80% of all samples analyzed for NO3-N, NH4-N, and PO4-P at Pine, Bogard, and Bailey Creeks were below the detection limit, with the exception of naturally elevated PO4-P in Bogard Creek. All nutrient concentrations (NO3-N, NH4-N, PO4-P, K, and SO4-S) showed little variation within streams and across years. Turbidity and TSS exhibited annual variation, but there was no significant increase in the difference between upstream and downstream turbidity and TSS levels. There was a significant decrease in stream canopy cover and increase in the potential fraction of solar radiation reaching the streams in response to the Pine-Bogard Phase 3 and Bailey treatments; however, there was no corresponding increase in stream temperatures. Macroinvertebrate metrics indicated healthy aquatic ecosystem conditions throughout the course of the study. Lastly, the removal of vegetation significantly increased soil moisture in treated stands relative to untreated stands. These results indicate that, with careful planning and implementation of site-specific best management practices, conifer removal to

  14. Aquatic ecosystem response to timber harvesting for the purpose of restoring aspen.

    PubMed

    Jones, Bobette E; Krupa, Monika; Tate, Kenneth W

    2013-01-01

    The removal of conifers through commercial timber harvesting has been successful in restoring aspen, however many aspen stands are located near streams, and there are concerns about potential aquatic ecosystem impairment. We examined the effects of management-scale conifer removal from aspen stands located adjacent to streams on water quality, solar radiation, canopy cover, temperature, aquatic macroinvertebrates, and soil moisture. This 8-year study (2003-2010) involved two projects located in Lassen National Forest. The Pine-Bogard Project consisted of three treatments adjacent to Pine and Bogard Creeks: (i) Phase 1 in January 2004, (ii) Phase 2 in August 2005, and (iii) Phase 3 in January 2008. The Bailey Project consisted of one treatment adjacent to Bailey Creek in September 2006. Treatments involved whole tree removal using track-laying harvesters and rubber tire skidders. More than 80% of all samples analyzed for NO₃-N, NH₄-N, and PO₄-P at Pine, Bogard, and Bailey Creeks were below the detection limit, with the exception of naturally elevated PO₄-P in Bogard Creek. All nutrient concentrations (NO₃-N, NH₄-N, PO₄-P, K, and SO₄-S) showed little variation within streams and across years. Turbidity and TSS exhibited annual variation, but there was no significant increase in the difference between upstream and downstream turbidity and TSS levels. There was a significant decrease in stream canopy cover and increase in the potential fraction of solar radiation reaching the streams in response to the Pine-Bogard Phase 3 and Bailey treatments; however, there was no corresponding increase in stream temperatures. Macroinvertebrate metrics indicated healthy aquatic ecosystem conditions throughout the course of the study. Lastly, the removal of vegetation significantly increased soil moisture in treated stands relative to untreated stands. These results indicate that, with careful planning and implementation of site-specific best management practices

  15. In the dark: A review of ecosystem processes during the Arctic polar night

    NASA Astrophysics Data System (ADS)

    Berge, Jørgen; Renaud, Paul E.; Darnis, Gerald; Cottier, Finlo; Last, Kim; Gabrielsen, Tove M.; Johnsen, Geir; Seuthe, Lena; Weslawski, Jan Marcin; Leu, Eva; Moline, Mark; Nahrgang, Jasmine; Søreide, Janne E.; Varpe, Øystein; Lønne, Ole Jørgen; Daase, Malin; Falk-Petersen, Stig

    2015-12-01

    Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated high levels of feeding and reproduction in a wide range of taxa and habitats. Second, as more knowledge emerges, it is evident that a coupled physical and biological perspective of the ecosystem will redefine seasonality beyond the "calendar perspective". Third, it appears that many organisms may exhibit endogenous rhythms that trigger fitness-maximizing activities in the absence of light-based cues. Indeed a common adaptation appears to be the ability to utilize the dark season for reproduction. This and other processes are most likely adaptations to current environmental conditions and community and trophic structures of the ecosystem, and may have implications for how Arctic ecosystems can change under continued climatic warming.

  16. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  17. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  18. Heavy metal pollution in aquatic ecosystems and its phytoremediation using wetland plants: an ecosustainable approach.

    PubMed

    Rai, Prabhat Kumar

    2008-01-01

    This review addresses the global problem of heavymetal pollution originating from increased industrialization and urbanization and its amelioration by using wetland plants both in a microcosm as well as natural/field condition. Heavymetal contamination in aquatic ecosystems due to discharge of industrial effluents may pose a serious threat to human health. Alkaline precipitation, ion exchange columns, electrochemical removal, filtration, and membrane technologies are the currently available technologies for heavy metal removal. These conventional technologies are not economical and may produce adverse impacts on aquatic ecosystems. Phytoremediation of metals is a cost-effective "green" technology based on the use of specially selected metal-accumulating plants to remove toxic metals from soils and water. Wetland plants are important tools for heavy metal removal. The Ramsar convention, one of the earlier modern global conservation treaties, was adopted at Ramsar, Iran, in 1971 and became effective in 1975. This convention emphasized the wise use of wetlands and their resources. This review mentions salient features of wetland ecosystems, their vegetation component, and the pros and cons involved in heavy metal removal. Wetland plants are preferred over other bio-agents due to their low cost, frequent abundance in aquatic ecosystems, and easy handling. The extensive rhizosphere of wetland plants provides an enriched culture zone for the microbes involved in degradation. The wetland sediment zone provides reducing conditions that are conducive to the metal removal pathway. Constructed wetlands proved to be effective for the abatement of heavymetal pollution from acid mine drainage; landfill leachate; thermal power; and municipal, agricultural, refinery, and chlor-alkali effluent. the physicochemical properties of wetlands provide many positive attributes for remediating heavy metals. Typha, Phragmites, Eichhornia, Azolla, Lemna, and other aquatic macrophytes are some

  19. Photodemethylation of Methylmercury in Eastern Canadian Arctic Thaw Pond and Lake Ecosystems.

    PubMed

    Girard, Catherine; Leclerc, Maxime; Amyot, Marc

    2016-04-01

    Permafrost thaw ponds of the warming Eastern Canadian Arctic are major landscape constituents and often display high levels of methylmercury (MeHg). We examined photodegradation potentials in high-dissolved organic matter (DOC) thaw ponds on Bylot Island (BYL) and a low-DOC oligotrophic lake on Cornwallis Island (Char Lake). In BYL, the ambient MeHg photodemethylation (PD) rate over 48 h of solar exposure was 6.1 × 10(-3) m(2) E(-1), and the rate in MeHg amended samples was 9.3 × 10(-3) m(2) E(-1). In contrast, in low-DOC Char Lake, PD was only observed in the first 12 h, which suggests that PD may not be an important loss process in polar desert lakes. Thioglycolic acid addition slowed PD, while glutathione and chlorides did not impact northern PD rates. During an ecosystem-wide experiment conducted in a covered BYL pond, there was neither net MeHg increase in the dark nor loss attributable to PD following re-exposure to sunlight. We propose that high-DOC Arctic thaw ponds are more prone to MeHg PD than nearby oligotrophic lakes, likely through photoproduction of reactive species rather than via thiol complexation. However, at the ecosystem level, these ponds, which are widespread through the Arctic, remain likely sources of MeHg for neighboring systems. PMID:26938195

  20. The Role of Biomarkers in the Assessment of Aquatic Ecosystem Health

    PubMed Central

    Hook, Sharon E; Gallagher, Evan P; Batley, Graeme E

    2016-01-01

    Ensuring the health of aquatic ecosystems and identifying species at risk from the detrimental effects of environmental contaminants can be facilitated by integrating analytical chemical analysis with carefully selected biological endpoints measured in tissues of species of concern. These biological endpoints include molecular, biochemical and physiological markers (i.e. biomarkers) that when integrated, can clarify issues of contaminant bioavailability, bioaccumulation and ecological effects while enabling a better understanding of the effects of non-chemical stressors. In the case of contaminant stressors, an understanding of chemical modes of toxicity can be incorporated with diagnostic markers of aquatic animal physiology to help understand the health status of aquatic organisms in the field. Furthermore, new approaches in functional genomics and bioinformatics can help discriminate individual chemicals, or groups of chemicals among complex mixtures that may contribute to adverse biological effects. While the use of biomarkers is not a new paradigm, such approaches have been underutilized in the context of ecological risk assessment and natural resource damage assessment. From a regulatory standpoint, these approaches can help better assess the complex effects from coastal development activities to assessing ecosystem integrity pre- and post-development or site remediation. PMID:24574147

  1. Heavy metal pollution in aquatic ecosystems and its phytoremediation using wetland plants: An ecosustainable approach

    SciTech Connect

    Rai, P.K.

    2008-07-01

    This review addresses the global problem of heavy metal pollution originating from increased industrialization and urbanization and its amelioration by using wetland plants both in a microcosm as well as natural/field condition. This review mentions salient features of wetland ecosystems, their vegetation component, and the pros and cons involved in heavy metal removal. Wetland plants are preferred over other bio-agents due to their low cost, frequent abundance in aquatic ecosystems, and easy handling. Constructed wetlands proved to be effective for the abatement of heavy metal pollution from acid mine drainage; landfill leachate; thermal power; and municipal, agricultural, refinery, and chlor-alkali effluent. the physicochemical properties of wetlands provide many positive attributes for remediating heavy metals. Typha, Phragmites, Eichhornia, Azolla, Lemna, and other aquatic macrophytes are some of the potent wetland plants for heavy metal removal. Biomass disposal problem and seasonal growth of aquatic macrophytes are some limitations in the transfer of phytoremediation technology from the laboratory to the field. However, the disposed biomass of macrophytes may be used for various fruitful applications. An ecosustainable model has been developed through the author's various works, which may ameliorate some of the limitations. The creation of more areas for phytoremediation may also aid in wetlands conservation. Genetic engineering and biodiversity prospecting of endangered wetland plants are important future prospects in this regard.

  2. Aquatic ecosystems in Central Colorado are influenced by mineral forming processes and historical mining

    USGS Publications Warehouse

    Schmidt, T.S.; Church, S.E.; Clements, W.H.; Mitchell, K.A.; Fey, D. L.; Wanty, R.B.; Verplanck, P.L.; San, Juan C.A.; Klein, T.L.; deWitt, E.H.; Rockwell, B.W.

    2009-01-01

    Stream water and sediment toxicity to aquatic insects were quantified from central Colorado catchments to distinguish the effect of geologic processes which result in high background metals concentrations from historical mining. Our sampling design targeted small catchments underlain by rocks of a single lithology, which allowed the development of biological and geochemical baselines without the complication of multiple rock types exposed in the catchment. By accounting for geologic sources of metals to the environment, we were able to distinguish between the environmental effects caused by mining and the weathering of different mineralized areas. Elevated metal concentrations in water and sediment were not restricted to mined catchments. Impairment of aquatic communities also occurred in unmined catchments influenced by hydrothermal alteration. Hydrothermal alteration style, deposit type, and mining were important determinants of water and sediment quality and aquatic community structure. Weathering of unmined porphyry Cu-Mo occurrences resulted in water (median toxic unit (TU) = 108) and sediment quality (TU = 1.9) that exceeded concentrations thought to be safe for aquatic ecosystems (TU = 1). Metalsensitive aquatic insects were virtually absent from streams draining catchments with porphyry Cu-Mo occurrences (1.1 individuals/0.1 m2 ). However, water and sediment quality (TU = 0.1, 0.5 water and sediment, respectively) and presence of metalsensitive aquatic insects (204 individuals/0.1 m2 ) for unmined polymetallic vein occurrences were indistinguishable from that for unmined and unaltered streams (TU = 0.1, 0.5 water and sediment, respectively; 201 individuals/0.1 m2 ). In catchments with mined quartz-sericite-pyrite altered polymetallic vein deposits, water (TU = 8.4) and sediment quality (TU = 3.1) were degraded and more toxic to aquatic insects (36 individuals/0.1 m2 ) than water (TU = 0.4) and sediment quality (TU = 1.7) from mined propylitically altered

  3. The First Law of Thermodynamics for Ecosystems. Physical Processes in Terrestrial and Aquatic Ecosystems, Thermodynamics.

    ERIC Educational Resources Information Center

    Stevenson, R. D.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module and a comparison module are concerned with elementary concepts of thermodynamics as…

  4. Watershed land use and aquatic ecosystem response: Ecohydrologic approach to conservation policy

    NASA Astrophysics Data System (ADS)

    Randhir, Timothy O.; Hawes, Ashley G.

    2009-01-01

    SummaryLand use activities change the natural functions of a watershed impacting the flow of water and water quality, and impair aquatic ecosystems. Optimal allocation of land use depends on attributes related to terrestrial and aquatic environments. A dynamic model that links land use, overland flow, suspended sediment, and an aquatic species is used to evaluate alternate land use policies. The dwarf wedge mussel that is classified as endangered in the region is used as an indicator species of aquatic health in a watershed in Massachusetts. The simulation model is used to evaluate spatial nature of processes and land use policies. Spatial and temporal changes in runoff, sediment loading, and mussel population are modeled over a period of 4 years. Ten policy scenarios represent combinations of best management practices and development of agriculture and urban land at spatial locations of headwaters, main stem regions, riparian, and entire watershed. Increasing the proportion of agriculture and high density residential land use increased runoff, while increasing the frequency and magnitude of peak flows in the watershed. Sediment loading increased with an increased proportion of agriculture area and decreased with an expansion of high density residential area. Scenarios with an increase in sediment loading above the baseline mean exhibited an irregular recovery of the mussel population from high loading events. Policy implications include the need for best management practices to decrease runoff and sediment loading in the watershed, through education and incentive programs.

  5. A review of ecological effects and environmental fate of illicit drugs in aquatic ecosystems.

    PubMed

    Rosi-Marshall, E J; Snow, D; Bartelt-Hunt, S L; Paspalof, A; Tank, J L

    2015-01-23

    Although illicit drugs are detected in surface waters throughout the world, their environmental fate and ecological effects are not well understood. Many illicit drugs and their breakdown products have been detected in surface waters and temporal and spatial variability in use translates into "hot spots and hot moments" of occurrence. Illicit drug occurrence in regions of production and use and areas with insufficient wastewater treatment are not well studied and should be targeted for further study. Evidence suggests that illicit drugs may not be persistent, as their half-lives are relatively short, but may exhibit "pseudo-persistence" wherein continual use results in persistent occurrence. We reviewed the literature on the ecological effects of these compounds on aquatic organisms and although research is limited, a wide array of aquatic organisms, including bacteria, algae, invertebrates, and fishes, have receptors that make them potentially sensitive to these compounds. In summary, illicit drugs occur in surface waters and aquatic organisms may be affected by these compounds; research is needed that focuses on concentrations of illicit drugs in areas of production and high use, environmental fate of these compounds, and effects of these compounds on aquatic ecosystems at the concentrations that typically occur in the environment. PMID:25062553

  6. Transfer of a cyanobacterial neurotoxin within a temperate aquatic ecosystem suggests pathways for human exposure

    PubMed Central

    Jonasson, Sara; Eriksson, Johan; Berntzon, Lotta; Spáčil, Zdenĕk; Ilag, Leopold L.; Ronnevi, Lars-Olof; Rasmussen, Ulla; Bergman, Birgitta

    2010-01-01

    β-methylamino-L-alanine (BMAA), a neurotoxic nonprotein amino acid produced by most cyanobacteria, has been proposed to be the causative agent of devastating neurodegenerative diseases on the island of Guam in the Pacific Ocean. Because cyanobacteria are widespread globally, we hypothesized that BMAA might occur and bioaccumulate in other ecosystems. Here we demonstrate, based on a recently developed extraction and HPLC-MS/MS method and long-term monitoring of BMAA in cyanobacterial populations of a temperate aquatic ecosystem (Baltic Sea, 2007–2008), that BMAA is biosynthesized by cyanobacterial genera dominating the massive surface blooms of this water body. BMAA also was found at higher concentrations in organisms of higher trophic levels that directly or indirectly feed on cyanobacteria, such as zooplankton and various vertebrates (fish) and invertebrates (mussels, oysters). Pelagic and benthic fish species used for human consumption were included. The highest BMAA levels were detected in the muscle and brain of bottom-dwelling fishes. The discovery of regular biosynthesis of the neurotoxin BMAA in a large temperate aquatic ecosystem combined with its possible transfer and bioaccumulation within major food webs, some ending in human consumption, is alarming and requires attention. PMID:20439734

  7. Mediterranean coastal lagoons in an ecosystem and aquatic resources management context

    NASA Astrophysics Data System (ADS)

    Pérez-Ruzafa, A.; Marcos, C.; Pérez-Ruzafa, I. M.

    Aquatic ecosystems, water resources and their management are some of the main problems facing humanity. These problems vary from water scarcity and deteriorating quality for human consumption and use, to floods in areas with torrential rainfall, rising sea levels in coastal zones, the overexploitation of living resources and the loss of ecological quality and biodiversity. Proper water management needs to follow a hierarchical perspective, ranging from the whole planet to individual water bodies. Spatio-temporal scales change at each level, as do driving forces, impacts, and the processes and responses involved. Recently, the European Union adopted the Water Framework Directive (WFD) to establish the basic principles of sustainable water policy in member states, one of the main concerns being the need to consider the vulnerability of coastal aquatic ecosystems and to establish their ecological status. However, from a Mediterranean point of view, the actions of European countries (under the WFD regulations) and non-EU countries need to be coordinated. There are more than 100 coastal lagoons in the Mediterranean. They are habitats with an important ecological role, but also provide essentials goods and services for humans. In the present work, we look at the problems involved in understanding their definition and management. At water body management level, we emphasise that scientific cooperation is necessary to deal with the conceptual and ecological difficulties derived from inter and intra-lagoon variability in hydrology and biological assemblages, inherent factors in the functioning of these complex ecosystems.

  8. Impacts of aquatic nonindigenous invasive species on the Lake Erie ecosystem

    USGS Publications Warehouse

    Austen, Madeline J.W.; Ciborowski, Jan J.H.; Corkum, Lynda D.; Johnson, Tim B.; MacIsaac, Hugh J.; Metcalfe-Smith, Janice L.; Schloesser, Donald W.; George, Sandra E.

    2002-01-01

    Lake Erie is particularly vulnerable to the introduction and establishment of aquatic nonindigenous invasive species (NIS) populations. A minimum of 144 aquatic NIS have been recorded in the Lake Erie basin including several species [e.g., Eurasian watermilfoil (Myriophyllum spicatum); zebra mussel (Dreissena polymorpha); quagga mussel (Dreissena bugensis); an amphipod (Echinogammarus ischnus); round goby (Neogobius melanostomus); and sea lamprey (Petromyzon marinus)] that have had discernible impacts on the lake's ecology. NIS pose threats to the Lake Erie ecosystem for a variety of reasons including their ability to proliferate quickly, compete with native species, and transfer contaminants (e.g., PCBs) and disease through the food web. Six of the 14 beneficial use impairments listed in Annex 2 of the Great Lakes Water Quality Agreement are impaired in Lake Erie, in part as a result of the introduction of NIS. The Lake Erie Lakewide Management Plan (LaMP) has adopted an ecosystem approach to restore beneficial use impairments in the lake. Furthermore, a research consortium, known as the Lake Erie Millennium Network, is working alongside the LaMP, to address research problems regarding NIS, the loss of habitat, and the role of contaminants in the Lake Erie ecosystem.

  9. Measures to reduce pesticide spray drift in a small aquatic ecosystem in vineyard estate.

    PubMed

    Vischetti, Costantino; Cardinali, Alessandra; Monaci, Elga; Nicelli, Marco; Ferrari, Federico; Trevisan, Marco; Capri, Ettore

    2008-01-25

    A field experiment is reported to ascertain the drift of two pesticides (chlorpyrifos and metalaxyl) in a vineyard in Italian climatic conditions and the effect of mitigation measures, such as buffer zones and tree rows, on pesticide drift contamination in a small aquatic system located inside the field. Results indicated that, in typical Italian agricultural conditions, spray drift in vineyards occurs at a distance of more than 24 m and adequate buffer zones are required to protect surface water bodies from direct contamination. The presence of tree rows in front of the water body inside the agricultural field, against the main wind direction, resulted in a very high reduction of the spray drift and of the ecotoxicological risk for aquatic ecosystem. In addition, a comparison between the data obtained in the experiment and the Drift Calculator procedure showed that the model failed when the procedure is used for short distances. However, concordance was found in terms of maximum drift distances. PMID:17936878

  10. Quantifying Biogeochemical Cycles of CO2 and CH4 over the Land and Aquatic Ecosystems in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Zhuang, Q.

    2015-12-01

    Under the auspices of the NASA Land-Use and Land-Cover Change Program, we have made a significant progress on quantifying both CO2 and CH4 biogeochemical cycles of the land and aquatic systems in Northern Eurasia over the last several decades. Our quantification is based on in situ and satellite data of ecosystem distribution, land cover distribution, carbon, water and energy fluxes, fire disturbances, plant biomass inventory, atmospheric CO2 and CH4, and meteorology. The evaluated process-based modeling systems for both land and aquatic ecosystems for the historical period have been used to project carbon fluxes during the 21st century over this region. The uncertainty associated with these carbon-based gases is also quantified. This presentation will update these quantifications by examining: 1) the impacts of fire disturbances on land ecosystem CO2 budget in the last few decades; 2) net CO2 and CH4 exchanges of the land and aquatic ecosystems in both historical and future periods. Our study has also assessed the role of permafrost dynamics in both land and aquatic ecosystem carbon and water dynamics in this region. Our research provides an integrated land and aquatic ecosystem model that can be used to address biogeochemical cycles of carbon and water in this climate-sensitive region.

  11. Water quality assessment of aquatic ecosystems using ecological criteria – case study in Bulgaria

    PubMed Central

    Damyanova, Sonya; Ivanova, Iliana; Ignatova, Nadka

    2014-01-01

    Four aquatic ecosystems (two rivers and two dams) situated in the western part of Bulgaria were investigated over a three years’ period. The River Egulya and Petrohan dam are situated in mountainous regions at about 1000 m altitude, and are not influenced by any anthropogenic sources. Petrohan dam is a site for long-term ecosystem research as a part of Bulgarian long-term ecological research network. The other two systems belong to populated industrial areas. The River Martinovska flows through a region with former long-term mining activity, while Ogosta dam is near a battery production factory. Both the geochemical and geographical ecosystems’ conditions are different, and their social usage as well. Ogosta dam water is used for irrigation and Petrohan dam for electric supply. The ecosystem sensitivity to heavy metals was evaluated by a critical load approach. Two criteria were used for risk assessment: critical load exceedance and microbial toxicity test. All studied ecosystems were more sensitive to cadmium than to lead deposition. The potential risk of Cd damage is higher for Petrohan dam and the River Egulya, where critical load exceedance was calculated for two years. Pseudomonas putida growth inhibition test detected a lack of toxicity for all studied ecosystems at the time of investigation with the exception of the low water September sample of the River Martinovska. The fast bacterial test is very suitable for a regular measurement of water toxicity because of its simplicity, lack of sophisticated equipment and clear results. PMID:26019591

  12. Arctic ecosystem structure and functioning shaped by climate and herbivore body size

    NASA Astrophysics Data System (ADS)

    Legagneux, P.; Gauthier, G.; Lecomte, N.; Schmidt, N. M.; Reid, D.; Cadieux, M.-C.; Berteaux, D.; Bêty, J.; Krebs, C. J.; Ims, R. A.; Yoccoz, N. G.; Morrison, R. I. G.; Leroux, S. J.; Loreau, M.; Gravel, D.

    2014-05-01

    Significant progress has been made in our understanding of species-level responses to climate change, but upscaling to entire ecosystems remains a challenge. This task is particularly urgent in the Arctic, where global warming is most pronounced. Here we report the results of an international collaboration on the direct and indirect effects of climate on the functioning of Arctic terrestrial ecosystems. Our data from seven terrestrial food webs spread along a wide range of latitudes (~1,500 km) and climates (Δ mean July temperature = 8.5 °C) across the circumpolar world show the effects of climate on tundra primary production, food-web structure and species interaction strength. The intensity of predation on lower trophic levels increased significantly with temperature, at approximately 4.5% per °C. Temperature also affected trophic interactions through an indirect effect on food-web structure (that is, diversity and number of interactions). Herbivore body size was a major determinant of predator-prey interactions, as interaction strength was positively related to the predator-prey size ratio, with large herbivores mostly escaping predation. There is potential for climate warming to cause a switch from bottom-up to top-down regulation of herbivores. These results are critical to resolving the debate on the regulation of tundra and other terrestrial ecosystems exposed to global change.

  13. Assessment of variables controlling nitrate dynamics in groundwater: is it a threat to surface aquatic ecosystems?

    PubMed

    Rasiah, V; Armour, J D; Cogle, A L

    2005-01-01

    The impact of fertilised cropping on nitrate-N dynamics in groundwater (GW) was assessed in a catchment from piezometers installed: (i) to different depths, (ii) in different soil types, (iii) on different positions on landscape, and (iv) compared with the Australian and New Zealand Environmental and Conservation Council guideline values provided for different aquatic ecosystems. The GW and NO(3)-N concentration dynamics were monitored in 39 piezometer wells, installed to 5-90 m depth, under fertilized sugarcane (Saccharum officinarum-S) in the Johnstone River Catchment, Australia, from 1999 January through September 2002. The median nitrate-N concentration ranged from 14 to 1511 microg L(-1), and the 80th percentile from 0 to 1341 microg L(-1). In 34 out of the 39 piezometer wells the 80th percentile or 80% of the nitrate-N values were higher than 30 microg L(-1), which is the maximum trigger value provided in the ANZECC table for sustainable health of different aquatic ecosystems. Nitrate-N concentration decreased with increasing well depth, increasing depth of water in wells, and with decreasing relief on landscape. Nitrate-N was higher in alluvial soil profiles than on those formed in-situ. Nitrate-N increased with increasing rainfall at the beginning of the rainy season, fluctuated during the peak rainy period, and then decreased when the rain ceased. The rapid decrease in GW after the rains ceased suggested potential existed for nitrate-N to be discharged as lateral-flow into streams. This may contribute towards the deterioration in the health of down-stream aquatic ecosystems. PMID:15757708

  14. Imperiled mammalian fauna of aquatic ecosystems in the Southeast: A historical perspective: Chapter 9

    USGS Publications Warehouse

    Harvey, M.J.; Clark, J.D.

    1997-01-01

    The passage of the U.S. Endangered Species Act of 1973 resulted in an increased need for information concerning distribution and status of all native species. However, relatively little is known concerning the historical distribution and current status of many mammalian taxa, and this is particularly so for small non-game species. In this chapter we provide species accounts of mammals commonly associated with aquatic ecosystems that we consider to be imperiled in the southeastern United States. In these accounts we have included information which we feel is valuable toward best understanding the threats that challenge each considered taxon.

  15. Hydro-Geomorphic Variability as an Ecological Template for Aquatic and Riparian Ecosystems

    NASA Astrophysics Data System (ADS)

    Montgomery, D. R.

    2002-12-01

    Hydro-geomorphic processes act as ecological disturbances that shape ecosystem characteristics and dynamics and play key roles in creating, modifying, and destroying aquatic habitat. Within the broad regional context set by general patterns of climate, geology, topography, and vegetation, the combined influences of the hydrologic, geomorphic, and vegetation regimes dominate the variability of river systems. Of particular relevance to aquatic and riparian ecosystems are the main processes that transport and store water, sediment, and wood, and how differences in current and potential conditions are related to both local conditions and basin-wide tends. The concept of process domains, distinct areas of a landscape that correspond to different disturbance regimes, provides a framework for integrating the inherent interplay of spatial and temporal variability in channel processes. The intensity of the impact, the size of the area affected, and the frequency of occurrence together define the disturbance regime associated with particular hydro-geomorphic processes. The disturbance regime sets the physical habitat template that influences potentially successful behavioral and life-history strategies of stream dwelling organisms. The distribution of some organisms is strongly associated with different process domains, whereas that of habitat generalists are not. Three general principles apply to the use of hydro-geomorphic variability as an ecological template for aquatic and riparian ecosystems. (1) What constitutes a disturbance is species specific and will vary according to the system or community under consideration and focusing on needs of a single target species and life stage can unintentionally degrade the system for other species or life stages. For example, river restoration efforts focused on spawning reaches and water levels for chinook salmon may ignore or exacerbate the loss of off-channel habitat such as side channels, groundwater-fed floodplain channels

  16. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events.

    PubMed

    Choudhary, Sonal; Blaud, Aimeric; Osborn, A Mark; Press, Malcolm C; Phoenix, Gareth K

    2016-06-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem (15)N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g Nm(-2)yr(-1), applied as (15)NH4(15)NO3 in Svalbard (79(°)N), during the summer. Separate applications of (15)NO3(-) and (15)NH4(+) were also made to determine the importance of N form in their retention. More than 95% of the total (15)N applied was recovered after one growing season (~90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants>vascular plants>organic soil>litter>mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of (15)N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater (15)NO3(-) than (15)NH4(+), suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events may represent a major source of eutrophication. PMID:26956177

  17. Impacts of a recent storm surge on an Arctic delta ecosystem examined in the context of the last millennium.

    PubMed

    Pisaric, Michael F J; Thienpont, Joshua R; Kokelj, Steven V; Nesbitt, Holly; Lantz, Trevor C; Solomon, Steven; Smol, John P

    2011-05-31

    One of the most ominous predictions related to recent climatic warming is that low-lying coastal environments will be inundated by higher sea levels. The threat is especially acute in polar regions because reductions in extent and duration of sea ice cover increase the risk of storm surge occurrence. The Mackenzie Delta of northwest Canada is an ecologically significant ecosystem adapted to freshwater flooding during spring breakup. Marine storm surges during the open-water season, which move saltwater into the delta, can have major impacts on terrestrial and aquatic systems. We examined growth rings of alder shrubs (Alnus viridis subsp. fruticosa) and diatoms preserved in dated lake sediment cores to show that a recent marine storm surge in 1999 caused widespread ecological changes across a broad extent of the outer Mackenzie Delta. For example, diatom assemblages record a striking shift from freshwater to brackish species following the inundation event. What is of particular significance is that the magnitude of this recent ecological impact is unmatched over the > 1,000-year history of this lake ecosystem. We infer that no biological recovery has occurred in this lake, while large areas of terrestrial vegetation remain dramatically altered over a decade later, suggesting that these systems may be on a new ecological trajectory. As climate continues to warm and sea ice declines, similar changes will likely be repeated in other coastal areas of the circumpolar Arctic. Given the magnitude of ecological changes recorded in this study, such impacts may prove to be long lasting or possibly irreversible. PMID:21576496

  18. Hydrology modifies ecosystem responses to warming through interactions between soil, leaf and canopy processes in a high Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Maseyk, K. S.; Welker, J. M.; Lett, C.; Czimczik, C. I.; Lupascu, M.; Seibt, U. H.

    2013-12-01

    Arctic ecosystems are experiencing temperature increases more strongly than the global average, and increases in precipitation are also expected amongst the climate impacts on this region in the future. These changes are expected to strongly influence both plant physiology and soil biogeochemistry, and therefore ecosystem carbon balance, hydrology and nutrient cycling. We have investigated the effects of a long-term (10 years) increase in temperature (T2), soil water (W) and the combination of both (T2W) on leaf-level structure and function and ecosystem CO2 and water fluxes in a tundra ecosystem at a field manipulation experiment in NW Greenland. Leaf-level gas exchange, chlorophyll fluorescence, carbon (C), nitrogen (N) and morphology were measured on Salix arctica plants in treatment and control plots in June-July 2011, and continuous measurements of net ecosystem fluxes of carbon and water were made using automatic chambers coupled to a trace gas analyzer. Contrasting responses to the treatments were observed between leaf-level and net ecosystem fluxes. Plants in the elevated temperature treatment had the highest leaf-level photosynthetic capacity in terms of net CO2 assimilation rates and photosystem II efficiencies, and lowest rates of non-photochemical energy dissipation during photosynthesis. The plants in the plots with both elevated temperatures and additional water had the lowest photosystem II efficiencies and the highest rates of non-photochemical energy dissipation. However, net photosynthetic rates remained similar to control plants with additional water, due in part to higher stomatal conductance (W) and lower dark respiration rates (T2W). In contrast, net ecosystem CO2 and water fluxes were highest in the T2W plots, due largely to a 35% increase in leaf area. Total growing season C accumulation was 3-5 times greater, water fluxes were 1.5-2 times higher, and water use efficiency was about 3 times higher in the combined treatment than the control

  19. Adaptive genetic variation mediates bottom-up and top-down control in an aquatic ecosystem

    PubMed Central

    Rudman, Seth M.; Rodriguez-Cabal, Mariano A.; Stier, Adrian; Sato, Takuya; Heavyside, Julian; El-Sabaawi, Rana W.; Crutsinger, Gregory M.

    2015-01-01

    Research in eco-evolutionary dynamics and community genetics has demonstrated that variation within a species can have strong impacts on associated communities and ecosystem processes. Yet, these studies have centred around individual focal species and at single trophic levels, ignoring the role of phenotypic variation in multiple taxa within an ecosystem. Given the ubiquitous nature of local adaptation, and thus intraspecific variation, we sought to understand how combinations of intraspecific variation in multiple species within an ecosystem impacts its ecology. Using two species that co-occur and demonstrate adaptation to their natal environments, black cottonwood (Populus trichocarpa) and three-spined stickleback (Gasterosteus aculeatus), we investigated the effects of intraspecific phenotypic variation on both top-down and bottom-up forces using a large-scale aquatic mesocosm experiment. Black cottonwood genotypes exhibit genetic variation in their productivity and consequently their leaf litter subsidies to the aquatic system, which mediates the strength of top-down effects from stickleback on prey abundances. Abundances of four common invertebrate prey species and available phosphorous, the most critically limiting nutrient in freshwater systems, are dictated by the interaction between genetic variation in cottonwood productivity and stickleback morphology. These interactive effects fit with ecological theory on the relationship between productivity and top-down control and are comparable in strength to the effects of predator addition. Our results illustrate that intraspecific variation, which can evolve rapidly, is an under-appreciated driver of community structure and ecosystem function, demonstrating that a multi-trophic perspective is essential to understanding the role of evolution in structuring ecological patterns. PMID:26203004

  20. Adaptive genetic variation mediates bottom-up and top-down control in an aquatic ecosystem.

    PubMed

    Rudman, Seth M; Rodriguez-Cabal, Mariano A; Stier, Adrian; Sato, Takuya; Heavyside, Julian; El-Sabaawi, Rana W; Crutsinger, Gregory M

    2015-08-01

    Research in eco-evolutionary dynamics and community genetics has demonstrated that variation within a species can have strong impacts on associated communities and ecosystem processes. Yet, these studies have centred around individual focal species and at single trophic levels, ignoring the role of phenotypic variation in multiple taxa within an ecosystem. Given the ubiquitous nature of local adaptation, and thus intraspecific variation, we sought to understand how combinations of intraspecific variation in multiple species within an ecosystem impacts its ecology. Using two species that co-occur and demonstrate adaptation to their natal environments, black cottonwood (Populus trichocarpa) and three-spined stickleback (Gasterosteus aculeatus), we investigated the effects of intraspecific phenotypic variation on both top-down and bottom-up forces using a large-scale aquatic mesocosm experiment. Black cottonwood genotypes exhibit genetic variation in their productivity and consequently their leaf litter subsidies to the aquatic system, which mediates the strength of top-down effects from stickleback on prey abundances. Abundances of four common invertebrate prey species and available phosphorous, the most critically limiting nutrient in freshwater systems, are dictated by the interaction between genetic variation in cottonwood productivity and stickleback morphology. These interactive effects fit with ecological theory on the relationship between productivity and top-down control and are comparable in strength to the effects of predator addition. Our results illustrate that intraspecific variation, which can evolve rapidly, is an under-appreciated driver of community structure and ecosystem function, demonstrating that a multi-trophic perspective is essential to understanding the role of evolution in structuring ecological patterns. PMID:26203004

  1. Presence of the Neurotoxin BMAA in Aquatic Ecosystems: What Do We Really Know?

    PubMed Central

    Faassen, Elisabeth J.

    2014-01-01

    The neurotoxin β-N-methylamino-l-alanine (BMAA) is suspected to play a role in the neurological diseases amyotrophic lateral sclerosis, Alzheimer’s disease, and Parkinson’s disease. BMAA production by cyanobacteria has been reported and contact with cyanobacteria infested waters or consumption of aquatic organisms are possible pathways to human exposure. However, there is little consensus regarding whether BMAA is present in cyanobacteria or not, and if so, at what concentrations. The aim of this review is to indicate the current state of knowledge on the presence of BMAA in aquatic ecosystems. Some studies have convincingly shown that BMAA can be present in aquatic samples at the µg/g dry weight level, which is around the detection limit of some equally credible studies in which no BMAA was detected. However, for the majority of the reviewed articles, it was unclear whether BMAA was correctly identified, either because inadequate analytical methods were used, or because poor reporting of analyses made it impossible to verify the results. Poor analysis, reporting and prolific errors have shaken the foundations of BMAA research. First steps towards estimation of human BMAA exposure are to develop and use selective, inter-laboratory validated methods and to correctly report the analytical work. PMID:24662480

  2. Presence of the neurotoxin BMAA in aquatic ecosystems: what do we really know?

    PubMed

    Faassen, Elisabeth J

    2014-03-01

    The neurotoxin β-N-methylamino-L-alanine (BMAA) is suspected to play a role in the neurological diseases amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease. BMAA production by cyanobacteria has been reported and contact with cyanobacteria infested waters or consumption of aquatic organisms are possible pathways to human exposure. However, there is little consensus regarding whether BMAA is present in cyanobacteria or not, and if so, at what concentrations. The aim of this review is to indicate the current state of knowledge on the presence of BMAA in aquatic ecosystems. Some studies have convincingly shown that BMAA can be present in aquatic samples at the µg/g dry weight level, which is around the detection limit of some equally credible studies in which no BMAA was detected. However, for the majority of the reviewed articles, it was unclear whether BMAA was correctly identified, either because inadequate analytical methods were used, or because poor reporting of analyses made it impossible to verify the results. Poor analysis, reporting and prolific errors have shaken the foundations of BMAA research. First steps towards estimation of human BMAA exposure are to develop and use selective, inter-laboratory validated methods and to correctly report the analytical work. PMID:24662480

  3. Does the current fungicide risk assessment provide sufficient protection for key drivers in aquatic ecosystem functioning?

    PubMed

    Zubrod, Jochen P; Englert, Dominic; Feckler, Alexander; Koksharova, Natalia; Konschak, Marco; Bundschuh, Rebecca; Schnetzer, Nadja; Englert, Katja; Schulz, Ralf; Bundschuh, Mirco

    2015-01-20

    The level of protection provided by the present environmental risk assessment (ERA) of fungicides in the European Union for fungi is unknown. Therefore, we assessed the structural and functional implications of five fungicides with different modes of action (azoxystrobin, carbendazim, cyprodinil, quinoxyfen, and tebuconazole) individually and in mixture on communities of aquatic hyphomycetes. This is a polyphyletic group of fungi containing key drivers in the breakdown of leaf litter, governing both microbial leaf decomposition and the palatability of leaves for leaf-shredding macroinvertebrates. All fungicides impaired leaf palatability to the leaf-shredder Gammarus fossarum and caused structural changes in fungal communities. In addition, all compounds except for quinoxyfen altered microbial leaf decomposition. Our results suggest that the European Union’s first-tier ERA provides sufficient protection for the tested fungicides, with the exception of tebuconazole and the mixture, while higher-tier ERA does not provide an adequate level of protection for fungicides in general. Therefore, our results show the need to incorporate aquatic fungi as well as their functions into ERA testing schemes to safeguard the integrity of aquatic ecosystems. PMID:25517729

  4. Modern to millennium-old greenhouse gases emitted from freshwater ecosystems of the eastern Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Bouchard, F.; Laurion, I.; Preskienis, V.; Fortier, D.; Xu, X.; Whiticar, M. J.

    2015-07-01

    Ponds and lakes are widespread across the rapidly changing permafrost environments. Aquatic systems play an important role in global biogeochemical cycles, especially in greenhouse gas (GHG) exchanges between terrestrial systems and the atmosphere. The source, speciation and emission of carbon released from permafrost landscapes are strongly influenced by local specific conditions rather than general environmental setting. This study reports on GHG ages and emission rates from aquatic systems on Bylot Island in the eastern Canadian Arctic. Dissolved and ebullition gas samples were collected during the summer season from different types of water bodies located in a highly dynamic periglacial valley: polygonal ponds, collapsed ice-wedge trough ponds, and larger lakes overlying unfrozen soils (talik). The results showed strikingly different ages and fluxes depending on aquatic system types. Polygonal ponds were net sinks of dissolved CO2, but variable sources of dissolved CH4. They presented the highest ebullition fluxes, one or two orders of magnitude higher than from other ponds and lakes. Trough ponds appeared as substantial GHG sources, especially when their edges were actively eroding. Both types of ponds produced modern to hundreds of years old (<550 yr BP) GHG, even if trough ponds could contain much older carbon (>2000 yr BP) derived from freshly eroded peat. Lakes had small dissolved and ebullition fluxes, however they released much older GHG, including millennium-old CH4 (up to 3500 yr BP) sampled from lake central areas. Acetoclastic methanogenesis dominated at all study sites and there was minimal, if any, methane oxidation in gas emitted through ebullition. These findings provide new insights on the variable role of permafrost aquatic systems as a positive feedback mechanism on climate.

  5. Life cycle impacts of topsoil erosion on aquatic ecosystems: case study on Eucalyptus globulus forest

    NASA Astrophysics Data System (ADS)

    Quinteiro, Paula; Van de Broek, Marijn; Cláudia Dias, Ana; Ridoutt, Bradley; Arroja, Luís

    2016-04-01

    High concentrations of suspended solids (SS), particularly in the clay and silt size fractions, reaching lotic environments and remaining in suspension can be a significant stressors to the biodiversity of these aquatic systems, degrading the water quality and directly affecting the aquatic biota, namely macroinvertebrates, algae and macrophytes. This damage is presently not considered in Life Cycle Assessment studies. This study is devoted to the effects of SS into freshwater systems due to topsoil erosion by water (environmental mechanism), translated into damage to aquatic ecosystem diversity (endpoint impact category), namely to macroinvertebrates, algae and macrophytes. For this, we have developed a framework to conduct an erosion inventory using the WaTEM/SEDEM model and linked this with, a method to derive regional characterisation for endpoint damage on aquatic ecosystem diversity. A case study was performed for Eucalyptus globulus stands in Portugal, with a functional unit of one hectare of land under production forestry management. To demonstrate how this newly SS ecosystem method can help to improve the environmental assessment in forestry, results were compared with the earlier commonly used impact categories from ReCiPe method. The relevance of the impact from SS delivery to freshwater streams is shown, providing a more comprehensive assessment of the SS impact from land use systems on aquatic environments. The SS impacts ranged from 15.5 to 1234.9 PDF.m3.yr.ha-1.revolution-1 for macroinvertebrates, and from 5.2 to 411.9 PDF.m3.yr.ha-1.revolution-1 for algae and macrophytes. For some stands, SS potential impacts on macroinvertebrates have the same order of magnitude than freshwater eutrophication, freshwater ecotoxicity, terrestrial ecotoxicity and terrestrial acidification impacts. For algae and macrophytes, most of the stands present SS impacts of the same order of magnitude as terrestrial ecotoxicity, one order of magnitude higher than freshwater

  6. Spatial and temporal trends of contaminants in Canadian Arctic freshwater and terrestrial ecosystems: a review.

    PubMed

    Braune, B; Muir, D; DeMarch, B; Gamberg, M; Poole, K; Currie, R; Dodd, M; Duschenko, W; Eamer, J; Elkin, B; Evans, M; Grundy, S; Hebert, C; Johnstone, R; Kidd, K; Koenig, B; Lockhart, L; Marshall, H; Reimer, K; Sanderson, J; Shutt, L

    1999-06-01

    The state of knowledge of contaminants in Canadian Arctic biota of the freshwater and terrestrial ecosystems has advanced enormously since the publication of the first major reviews by Lockhart et al. and Thomas et al. in The Science of the Total Environment in 1992. The most significant gains are new knowledge of spatial trends of organochlorines and heavy metal contaminants in terrestrial animals, such as caribou and mink, and in waterfowl, where no information was previously available. Spatial trends in freshwater fish have been broadened, especially in the Yukon, where contaminant measurements of, for example, organochlorines were previously non-existent. A review of contaminants data for fish from the Northwest Territories, Yukon and northern Quebec showed mercury as the one contaminant which consistently exceeds guideline limits for subsistence consumption or commercial sale. Lake trout and northern pike in the Canadian Shield lakes of the Northwest Territories and northern Quebec generally had the most elevated levels. Levels of other heavy metals were generally not elevated in fish. Toxaphene was the major organochlorine contaminant in all fish analyzed. The concentrations of organochlorine contaminants in fish appear to be a function not only of trophic level but of other aspects of the lake ecosystem. Among Arctic terrestrial mammals, PCBs and cadmium were the most prominent contaminants in the species analyzed. Relatively high levels (10-60 micrograms g-1) of cadmium were observed in kidney and liver of caribou from the Yukon, the Northwest Territories and northern Quebec, with concentrations in western herds being higher than in those from the east. For the organochlorine contaminants, a west to east increase in zigma PCBs, HCB and zigma HCH was found in caribou, probably as a result of the predominant west to east/north-east atmospheric circulation pattern which delivers these contaminants from industrialized regions of central and eastern North

  7. Effects of Conversion from Boreal Forest to Arctic Steppe on Soil Communities and Ecosystem Carbon Pools

    NASA Astrophysics Data System (ADS)

    Han, P. D.; Natali, S.; Schade, J. D.; Zimov, N.; Zimov, S. A.

    2014-12-01

    The end of the Pleistocene marked the extinction of a great variety of arctic megafauna, which, in part, led to the conversion of arctic grasslands to modern Siberian larch forest. This shift may have increased the vulnerability of permafrost to thawing because of changes driven by the vegetation shift; the higher albedo of grassland and low insulation of snow trampled by animals may have decreased soil temperatures and reduced ground thaw in the grassland ecosystem, resulting in protection of organic carbon in thawed soil and permafrost. To test these hypothesized impacts of arctic megafauna, we examined an experimental reintroduction of large mammals in northeast Siberia, initiated in 1988. Pleistocene Park now contains 23 horses, three musk ox, one bison, and several moose in addition to the native fauna. The park is 16 square km with a smaller enclosure (< 1 km) where animals spend most of their time and our study was focused. We measured carbon-pools in forested sites (where scat surveys showed low animal use), and grassy sites (which showed higher use), within the park boundaries. We also measured thaw depth and documented the soil invertebrate communities in each ecosystem. There was a substantial difference in number of invertebrates per kg of organic soil between the forest (600 ± 250) and grassland (300 ± 250), though these differences were not statistically significant they suggest faster nutrient turnover in the forest or a greater proportion of decomposition by invertebrates than other decomposers. While thaw depth was deeper in the grassland (60 ± 4 cm) than in the forest (40 ± 6 cm), we did not detect differences in organic layer depth or percent organic matter between grassland and forest. However, soil in the grassland had higher bulk density, and higher carbon stocks in the organic and mineral soil layers. Although deeper thaw depth in the grassland suggests that more carbon is available to microbial decomposers, ongoing temperature monitoring

  8. After the Storm: Assessing the carbon and nitrogen leaching potential from sediments deposited in aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.; Krieg, C.; Canning, C.; Inamdar, S. P.; Rowland, R. D.

    2015-12-01

    The erosive energy of large storms can mobilize, and subsequently deposit large amounts of sediment in receiving aquatic ecosystems. Depending on the character of the sediments there is potential for leaching or sequestration of carbon (C) and nitrogen (N) from the sediments. This could have significant implications for water quality, aquatic metabolism, and global cycling of C and N. This study examines the fate of these sediments by: (1) determining the amount and quality of organic matter that can be leached into the surrounding water from coarse, medium and fine particle classes (2) assessing the C and N contents of various particles classes and the sources of the sediment through isotopic composition. Bed sediment samples were collected along a 1-2nd order stream (eight locations) in a forested catchment in the Piedmont region of Maryland following a large storm event. Samples were sieved into three particle classes - coarse (2mm-1mm), medium (1mm-250µm) and fine (<250µm). Extractions were performed for each of three particle class sizes by leaching with DI water. Organic matter composition for the extracts was characterized using fluorescence. Stable isotopes of 13C and 15N were determined for bed sediment classes and upland source sediments to identify the origins of the eroded sediments. Extracts with low C:N ratios that also exhibit a higher percent protein and lower percent humic carbon content are considered most labile. Within the bed sediment deposits, differences were found in the distribution of labile compounds between each particle class size. Generally, course particle size exhibited the most labile characteristics, closely followed by medium particle size. Fine particle size exhibited the most refractory characteristics in all locations. These results are critical since climate-change predictions reveal more intense and large storms for the northeast US, with potentially greater impacts on aquatic ecosystems from eroded upland sediments.

  9. Cascading effects of induced terrestrial plant defences on aquatic and terrestrial ecosystem function

    PubMed Central

    Jackrel, Sara L.; Wootton, J. Timothy

    2015-01-01

    Herbivores induce plants to undergo diverse processes that minimize costs to the plant, such as producing defences to deter herbivory or reallocating limited resources to inaccessible portions of the plant. Yet most plant tissue is consumed by decomposers, not herbivores, and these defensive processes aimed to deter herbivores may alter plant tissue even after detachment from the plant. All consumers value nutrients, but plants also require these nutrients for primary functions and defensive processes. We experimentally simulated herbivory with and without nutrient additions on red alder (Alnus rubra), which supplies the majority of leaf litter for many rivers in western North America. Simulated herbivory induced a defence response with cascading effects: terrestrial herbivores and aquatic decomposers fed less on leaves from stressed trees. This effect was context dependent: leaves from fertilized-only trees decomposed most rapidly while leaves from fertilized trees receiving the herbivory treatment decomposed least, suggesting plants funnelled a nutritionally valuable resource into enhanced defence. One component of the defence response was a decrease in leaf nitrogen leading to elevated carbon : nitrogen. Aquatic decomposers prefer leaves naturally low in C : N and this altered nutrient profile largely explains the lower rate of aquatic decomposition. Furthermore, terrestrial soil decomposers were unaffected by either treatment but did show a preference for local and nitrogen-rich leaves. Our study illustrates the ecological implications of terrestrial herbivory and these findings demonstrate that the effects of selection caused by terrestrial herbivory in one ecosystem can indirectly shape the structure of other ecosystems through ecological fluxes across boundaries. PMID:25788602

  10. Dynamic exchanges between DOM and POM pools in coastal and inland aquatic ecosystems: A review.

    PubMed

    He, Wei; Chen, Meilian; Schlautman, Mark A; Hur, Jin

    2016-05-01

    Dynamic exchanges between dissolved organic matter (DOM) and particulate organic matter (POM) plays a critical role in organic carbon cycling in coastal and inland aquatic ecosystems, interactions with aquatic organisms, mobility and bioavailability of pollutants, among many other ecological and geochemical phenomena. Although DOM-POM exchange processes have been widely studied from different aspects, little to no effort has been made to date to provide a comprehensive, mechanistic, and micro-spatial schema for understanding various exchange processes occurring in different aquatic ecosystems in a unified way. The phenomena occurring between DOM and POM were explained here with the homogeneous and heterogeneous mechanisms. In the homogeneous mechanism, the participating components are only organic matter (OM) constituents themselves with aggregation and dissolution involved, whereas OM is associated with other components such as minerals and particulate colloids in the heterogeneous counterpart. Besides the generally concerned processes of aggregation/dissolution and adsorption/desorption, other ecological factors such as sunlight and organisms can also participate in DOM-POM exchanges through altering the chemical nature of OM. Despite the limitation of current analytical technologies, many unknown and/or unquantified processes need to be identified to unravel the complicated exchanges of OM between its dissolved and particulate states. Based on the review of several previous mathematical models, we proposed a unified conceptual model to describe all major dynamic exchange mechanisms on the basis of exergy theory. More knowledge of dynamic DOM-POM exchanges is warranted to overcome the potential problems arising from a simple division of OM into dissolved versus particulate states and to further develop more sophisticated mathematic models. PMID:26881732

  11. Cascading effects of induced terrestrial plant defences on aquatic and terrestrial ecosystem function.

    PubMed

    Jackrel, Sara L; Wootton, J Timothy

    2015-04-22

    Herbivores induce plants to undergo diverse processes that minimize costs to the plant, such as producing defences to deter herbivory or reallocating limited resources to inaccessible portions of the plant. Yet most plant tissue is consumed by decomposers, not herbivores, and these defensive processes aimed to deter herbivores may alter plant tissue even after detachment from the plant. All consumers value nutrients, but plants also require these nutrients for primary functions and defensive processes. We experimentally simulated herbivory with and without nutrient additions on red alder (Alnus rubra), which supplies the majority of leaf litter for many rivers in western North America. Simulated herbivory induced a defence response with cascading effects: terrestrial herbivores and aquatic decomposers fed less on leaves from stressed trees. This effect was context dependent: leaves from fertilized-only trees decomposed most rapidly while leaves from fertilized trees receiving the herbivory treatment decomposed least, suggesting plants funnelled a nutritionally valuable resource into enhanced defence. One component of the defence response was a decrease in leaf nitrogen leading to elevated carbon : nitrogen. Aquatic decomposers prefer leaves naturally low in C : N and this altered nutrient profile largely explains the lower rate of aquatic decomposition. Furthermore, terrestrial soil decomposers were unaffected by either treatment but did show a preference for local and nitrogen-rich leaves. Our study illustrates the ecological implications of terrestrial herbivory and these findings demonstrate that the effects of selection caused by terrestrial herbivory in one ecosystem can indirectly shape the structure of other ecosystems through ecological fluxes across boundaries. PMID:25788602

  12. Effects of UV radiation on aquatic ecosystems and interactions with other environmental factors.

    PubMed

    Häder, Donat-P; Williamson, Craig E; Wängberg, Sten-Åke; Rautio, Milla; Rose, Kevin C; Gao, Kunshan; Helbling, E Walter; Sinha, Rajeshwar P; Worrest, Robert

    2015-01-01

    Interactions between climate change and UV radiation are having strong effects on aquatic ecosystems due to feedback between temperature, UV radiation, and greenhouse gas concentration. Higher air temperatures and incoming solar radiation are increasing the surface water temperatures of lakes and oceans, with many large lakes warming at twice the rate of regional air temperatures. Warmer oceans are changing habitats and the species composition of many marine ecosystems. For some, such as corals, the temperatures may become too high. Temperature differences between surface and deep waters are becoming greater. This increase in thermal stratification makes the surface layers shallower and leads to stronger barriers to upward mixing of nutrients necessary for photosynthesis. This also results in exposure to higher levels of UV radiation of surface-dwelling organisms. In polar and alpine regions decreases in the duration and amount of snow and ice cover on lakes and oceans are also increasing exposure to UV radiation. In contrast, in lakes and coastal oceans the concentration and colour of UV-absorbing dissolved organic matter (DOM) from terrestrial ecosystems is increasing with greater runoff from higher precipitation and more frequent extreme storms. DOM thus creates a refuge from UV radiation that can enable UV-sensitive species to become established. At the same time, decreased UV radiation in such surface waters reduces the capacity of solar UV radiation to inactivate viruses and other pathogens and parasites, and increases the difficulty and price of purifying drinking water for municipal supplies. Solar UV radiation breaks down the DOM, making it more available for microbial processing, resulting in the release of greenhouse gases into the atmosphere. In addition to screening solar irradiance, DOM, when sunlit in surface water, can lead to the formation of reactive oxygen species (ROS). Increases in carbon dioxide are in turn acidifying the oceans and inhibiting

  13. Conceptual data modeling of wildlife response indicators to ecosystem change in the Arctic

    USGS Publications Warehouse

    Walworth, Dennis; Pearce, John M.

    2015-01-01

    Large research studies are often challenged to effectively expose and document the types of information being collected and the reasons for data collection across what are often a diverse cadre of investigators of differing disciplines. We applied concepts from the field of information or data modeling to the U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative to prototype an application of information modeling. The USGS CAE initiative is collecting information from marine and terrestrial environments in Alaska to identify and understand the links between rapid physical changes in the Arctic and response of wildlife populations to these ecosystem changes. An associated need is to understand how data collection strategies are informing the overall science initiative and facilitating communication of those strategies to a wide audience. We explored the use of conceptual data modeling to provide a method by which to document, describe, and visually communicate both enterprise and study level data; provide a simple means to analyze commonalities and differences in data acquisition strategies between studies; and provide a tool for discussing those strategies among researchers and managers.

  14. Aquatic bird disease and mortality as an indicator of changing ecosystem health

    USGS Publications Warehouse

    Newman, Scott H.; Chmura, Aleksei; Converse, Kathy; Kilpatrick, A. Marm; Patel, Nikkita; Lammers, Emily; Daszak, Peter

    2007-01-01

    We analyzed data from pathologic investigations in the United States, collected by the USGS National Wildlife Health Center between 1971 and 2005, into aquatic bird mortality events. A total of 3619 mortality events was documented for aquatic birds, involving at least 633 708 dead birds from 158 species belonging to 23 families. Environmental causes accounted for the largest proportion of mortality events (1737 or 48%) and dead birds (437 258 or 69%); these numbers increased between 1971 and 2000, with biotoxin mortalities due to botulinum intoxication (Types C and E) being the leading cause of death. Infectious diseases were the second leading cause of mortality events (20%) and dead birds (20%), with both viral diseases, including duck plague (Herpes virus), paramyxovirus of cormorants (Paramyxovirus PMV1) and West Nile virus (Flavivirus), and bacterial diseases, including avian cholera (Pasteurella multocida), chlamydiosis (Chalmydia psittici), and salmonellosis (Salmonella sp.), contributing. Pelagic, coastal marine birds and species that use marine and freshwater habitats were impacted most frequently by environmental causes of death, with biotoxin exposure, primarily botulinum toxin, resulting in mortalities of both coastal and freshwater species. Pelagic birds were impacted most severely by emaciation and starvation, which may reflect increased anthropogenic pressure on the marine habitat from over-fishing, pollution, and other factors. Our study provides important information on broad trends in aquatic bird mortality and highlights how long-term wildlife disease studies can be used to identify anthropogenic threats to wildlife conservation and ecosystem health. In particular, mortality data for the past 30 yr suggest that biotoxins, viral, and bacterial diseases could have impacted >5 million aquatic birds.

  15. Aquatic bird disease and mortality as an indicator of changing ecosystem health

    USGS Publications Warehouse

    Newman, S.H.; Chmura, A.; Converse, K.; Kilpatrick, A.M.; Patel, N.; Lammers, E.; Daszak, P.

    2007-01-01

    We analyzed data from pathologic investigations in the United States, collected by the USGS National Wildlife Health Center between 1971 and 2005, into aquatic bird mortality events. A total of 3619 mortality events was documented for aquatic birds, involving at least 633 708 dead birds from 158 species belonging to 23 families. Environmental causes accounted for the largest proportion of mortality events (1737 or 48%) and dead birds (437 258 or 69%); these numbers increased between 1971 and 2000, with biotoxin mortalities due to botulinum intoxication (Types C and E) being the leading cause of death. Infectious diseases were the second leading cause of mortality events (20%) and dead birds (20 %), with both viral diseases, including duck plague (Herpes virus), paramyxovirus of cormorants (Paramyxovirus PMV1) and West Nile virus (Flavivirus), and bacterial diseases, including avian cholera (Pasteurella multocida), chlamydiosis (Chalmydia psittici), and salmonellosis (Salmonella sp.), contributing. Pelagic, coastal marine birds and species that use marine and freshwater habitats were impacted most frequently by environmental causes of death, with biotoxin exposure, primarily botulinum toxin, resulting in mortalities of both coastal and freshwater species. Pelagic birds were impacted most severely by emaciation and starvation, which may reflect increased anthropogenic pressure on the marine habitat from over-fishing, pollution, and other factors. Our study provides important information on broad trends in aquatic bird mortality and highlights how long-term wildlife disease studies can be used to identify anthropogenic threats to wildlife conservation and ecosystem health. In particular, mortality data for the past 30 yr suggest that biotoxins, viral, and bacterial diseases could have impacted >5 million aquatic birds. ?? Inter-Research 2007.

  16. The relation between productivity and species diversity in temperate-Arctic marine ecosystems.

    PubMed

    Witman, Jon D; Cusson, Mathieu; Archambault, Philippe; Pershing, Andrew J; Mieszkowska, Nova

    2008-11-01

    Energy variables, such as evapotranspiration, temperature, and productivity explain significant variation in the diversity of many groups of terrestrial plants and animals at local to global scales. Although the ocean represents the largest continuous habitat on earth with a vast spectrum of primary productivity and species richness, little is known about how productivity influences species diversity in marine systems. To search for general relationships between productivity and species richness in the ocean, we analyzed data from three different benthic marine ecosystems (epifaunal communities on subtidal rock walls, on navigation buoys in the Gulf of St. Lawrence, and Canadian Arctic macrobenthos) across local to continental spatial scales (<20 to >1000 km) using a standardized proxy for productivity, satellite-derived chlorophyll a. Theoretically, the form of the function between productivity and species richness is either monotonically increasing or decreasing, or curvilinear (hump- or U-shaped). We found three negative linear and three hump-shaped relationships between chlorophyll a and species richness out of 10 independent comparisons. Scale dependence was suggested by more prevalent diversity-productivity relationships at smaller (local, landscape) than larger (regional, continental) spatial scales. Differences in the form of the functions were more closely allied with community type than with scale, as negative linear functions were restricted to sessile epifauna while hump-shaped functions occurred in Arctic macrobenthos (mixed epifauna, infauna). In two of the data sets, (St. Lawrence epifauna and Arctic macrobenthos) significant effects of chlorophyll a co-varied with the effects of salinity, suggesting that environmental stress as well as productivity influences diversity in these marine systems. The co-varying effect of salinity may commonly arise in broad-scale studies of productivity and diversity in marine ecosystems when attempting to sample the

  17. Spatial and temporal trends and effects of contaminants in the Canadian Arctic marine ecosystem: a review.

    PubMed

    Muir, D; Braune, B; DeMarch, B; Norstrom, R; Wagemann, R; Lockhart, L; Hargrave, B; Bright, D; Addison, R; Payne, J; Reimer, K

    1999-06-01

    Recent studies have added substantially to our knowledge of spatial and temporal trends of persistent organic pollutants and heavy metals in the Canadian Arctic marine ecosystem. This paper reviews the current state of knowledge of contaminants in marine biota in the Canadian Arctic and where possible, discusses biological effects. The geographic coverage of information on contaminants such as persistent organochlorines (OCs) (PCBs, DDT- and chlordane-related compounds, hexachlorocyclohexanes, toxaphene) and heavy metals (mercury, selenium, cadmium, lead) in tissues of marine mammal and sea birds is relatively complete. All major beluga, ringed seal and polar bear stocks along with several major sea bird colonies have been sampled and analysed for OC and heavy metal contaminants. Studies on contaminants in walrus are limited to Foxe Basin and northern Québec stocks, while migratory harp seals have only been studied recently at one location. Contaminant measurements in bearded seal, harbour seal, bowhead whale and killer whale tissues from the Canadian Arctic are very limited or non-existent. Many of the temporal trend data for contaminants in Canadian Arctic biota are confounded by changes in analytical methodology, as well as by variability due to age/size, or to dietary and population shifts. Despite this, studies of OCs in ringed seal blubber at Holman Island and in sea birds at Prince Leopold Island in Lancaster Sound show declining concentrations of PCBs and DDT-related compounds from the 1970s to 1980s then a levelling off during the 1980s and early 1990s. For other OCs, such as chlordane, HCH and toxaphene, limited data for the 1980s to early 1990s suggests few significant declines in concentrations in marine mammals or sea birds. Temporal trend studies of heavy metals in ringed seals and beluga found higher mean concentrations of mercury in more recent (1993/1994) samples than in earlier collections (1981-1984 in eastern Arctic, 1972-1973 in western Arctic

  18. Diets of aquatic birds reflect changes in the Lake Huron ecosystem

    USGS Publications Warehouse

    Hebert, Craig E.; Weseloh, D.V. Chip; Idrissi, Abode; Arts, Michael T.; Roseman, Edward F.

    2009-01-01

    Human activities have affected the Lake Huron ecosystem, in part, through alterations in the structure and function of its food webs. Insights into the nature of food web change and its ecological ramifications can be obtained through the monitoring of high trophic level predators such as aquatic birds. Often, food web change involves alterations in the relative abundance of constituent species and/or the introduction of new species (exotic invaders). Diet composition of aquatic birds is influenced, in part, by relative prey availability and therefore is a sensitive measure of food web structure. Using bird diet data to make inferences regarding food web change requires consistent measures of diet composition through time. This can be accomplished by measuring stable chemical and/or biochemical “ecological tracers” in archived avian samples. Such tracers provide insights into pathways of energy and nutrient transfer. In this study, we examine the utility of two groups of naturally-occurring intrinsic tracers (stable isotopes and fatty acids) to provide such information in a predatory seabird, the herring gull (Larus argentatus). Retrospective stable nitrogen and carbon isotope analysis of archived herring gull eggs identified declines in gull trophic position and shifts in food sources in Lake Huron over the last 25 years and changes in gull diet composition were inferred from egg fatty acid patterns. These independent groups of ecological tracers provided corroborating evidence of dietary change in this high trophic level predator. Gull dietary shifts were related to declines in prey fish abundance which suggests large-scale alterations to the Lake Huron ecosystem. Dietary shifts in herring gulls may be contributing to reductions in resources available for egg formation. Further research is required to evaluate how changes in resource availability may affect population sustainability in herring gulls and other waterbird species. Long-term biological monitoring

  19. A synthesis of the effects of pesticides on microbial persistence in aquatic ecosystems.

    PubMed

    Staley, Zachery R; Harwood, Valerie J; Rohr, Jason R

    2015-01-01

    Pesticides have a pervasive presence in aquatic ecosystems throughout the world. While pesticides are intended to control fungi, insects, and other pests, their mechanisms of action are often not specific enough to prevent unintended effects, such as on non-target microbial populations. Microorganisms, including algae and cyanobacteria, protozoa, aquatic fungi, and bacteria, form the basis of many food webs and are responsible for crucial aspects of biogeochemical cycling; therefore, the potential for pesticides to alter microbial community structures must be understood to preserve ecosystem services. This review examines studies that focused on direct population-level effects and indirect community-level effects of pesticides on microorganisms. Generally, insecticides, herbicides, and fungicides were found to have adverse direct effects on algal and fungal species. Insecticides and fungicides also had deleterious direct effects in the majority of studies examining protozoa species, although herbicides were found to have inconsistent direct effects on protozoans. Our synthesis revealed mixed or no direct effects on bacterial species among all pesticide categories, with results highly dependent on the target species, chemical, and concentration used in the study. Examination of community-level, indirect effects revealed that all pesticide categories had a tendency to reduce higher trophic levels, thereby diminishing top-down pressures and favoring lower trophic levels. Often, indirect effects exerted greater influence than direct effects. However, few studies have been conducted to specifically address community-level effects of pesticides on microorganisms, and further research is necessary to better understand and predict the net effects of pesticides on ecosystem health. PMID:26565685

  20. Spatial and temporal effects of olive mill wastewaters to stream macroinvertebrates and aquatic ecosystems status.

    PubMed

    Karaouzas, Ioannis; Skoulikidis, Nikolaos T; Giannakou, Urania; Albanis, Triantafyllos A

    2011-12-01

    Olive mill wastewater (OMW) is one of the major and most challenging organic pollutants in olive oil production countries. However, the knowledge about the in-situ effects of olive mill wastewaters to lotic ecosystems and their benthic organisms is very limited. To resolve this, eight sampling sites were selected upstream and downstream the outflow of several olive mills to assess the spatial and temporal effects of OMW to stream macroinvertebrates and to ecological status of stream ecosystems. Biotic (macroinvertebrates) and abiotic (physicochemical, hydromorphological) data were monitored for two years thus following the biennial cycle of olive growth and production and hydrological variation (drought-wet years). The results of this study revealed the spatial and temporal structural deterioration of the aquatic community due to OMW pollution with consequent reduction of the river capacity for reducing the effects of polluting substances through internal mechanisms of self-purification. OMW, even highly diluted, had dramatic impacts on the aquatic fauna and to the ecological status of the receiving stream ecosystems. The organic load of the wastewater expressed as BOD(5), COD and TSS, substrate contamination (sewage bacteria) and distance from the mill outlet, were the most important factors affecting macroinvertebrate assemblages while the typology (i.e. slope, altitude) and hydrology of the stream site (i.e. mountainous-lowland) and the intensity and volume of the wastewater were the most important determinants of self-purification processes. As OMW are usually being discharged in small size streams that are not considered in the Water Framework Directive 2000/60/EC, there is a need for including such systems into monitoring and assessment schemes as they may significantly contribute to the pollution load of the river basin. Furthermore, guidelines to manage these wastes through technologies that minimise their environmental impact and lead to a sustainable use

  1. Ecosystem Metabolism and Air-Water Fluxes of Greenhouse Gases in High Arctic Wetland Ponds

    NASA Astrophysics Data System (ADS)

    Lehnherr, I.; Venkiteswaran, J.; St. Louis, V. L.; Emmerton, C.; Schiff, S. L.

    2012-12-01

    Freshwater lakes and wetlands can be very productive systems on the Arctic landscape compared to terrestrial tundra ecosystems and provide valuable resources to many organisms, including waterfowl, fish and humans. Rates of ecosystem productivity dictate how much energy flows through food webs, impacting the abundance of higher-level organisms (e.g., fish), as well as the net carbon balance, which determines whether a particular ecosystem is a source or sink of carbon. Climate change is predicted to result in warmer temperatures, increased precipitation and permafrost melting in the Arctic and is already altering northern ecosystems at unprecedented rates; however, it is not known how freshwater systems are responding to these changes. To predict how freshwater systems will respond to complex environmental changes, it is necessary to understand the key processes, such as primary production and ecosystem respiration, that are driving these systems. We sampled wetland ponds (n=8) and lakes (n=2) on northern Ellesmere Island (81° N, Nunavut, Canada) during the open water season for a suite of biogeochemical parameters, including concentrations of dissolved gases (O2, CO2, CH4, N2O) as well as stable-isotope ratios of dissolved inorganic carbon (δ13C-DIC), dissolved oxygen (δ18O-DO), and water (δ18O-H2O). We will present rates of primary production and ecosystem respiration, modeled from the concentration and stable isotope ratios of DIC and DO, as well as air-water gas exchange of greenhouse gases in these high Arctic ponds and lakes. Preliminary results demonstrate that ecosystem metabolism in these ponds was high enough to result in significant deviations in the isotope ratios of DIC and DO from atmospheric equilibrium conditions. In other words ecosystem rates of primary production and respiration were faster than gas exchange even in these small, shallow, well-mixed ponds. Furthermore, primary production was elevated enough at all sites except Lake Hazen, a

  2. Next Generation Ecosystem Experiment: Quantification and prediction of coupled processes in the terrestrial Arctic system

    NASA Astrophysics Data System (ADS)

    Hubbard, S. S.; Hinzman, L. D.; Graham, D. E.; Liang, L.; Norby, R.; Riley, W. J.; Rogers, A.; Rowland, J. C.; Thornton, P. E.; Torn, M. S.; Wilson, C. J.; Wullschleger, S. D.; NGEE Scientific Team

    2011-12-01

    Predicting the evolution of Arctic ecosystems to a changing climate is complicated by the many interactions and feedbacks that occur within and between components of the system. A new DOE Biological and Environmental Research project, called the Next-Generation Ecosystem Experiments (NGEE) is being initiated to address "how does permafrost degradation in a warming Arctic, and the associated changes in landscape evolution, hydrology, soil biogeochemical processes, and plant community succession, affect feedbacks to the climate system?". A multi-disciplinary team will use observations, experiments, and simulations carried out from the pore to the landscape scales to address these questions. We will combine field research (performed around thermokarst features in Alaska on the North Slope and Seward Peninsula), laboratory research using a variety of approaches and techniques, and remote sensing observations to improve modeling capabilities for high-latitude systems. Our research is organized into four interrelated 'Challenges' to quantify: (1) environmental controls on permafrost degradation and its influence on hydrological state, stocks, fluxes and pathways; (2) mechanisms that drive structural and functional responses of the tundra plant community to changing resource availability; (3) controls, mechanisms and rates driving biodegradation of soil organic matter; and (4) the impact of permafrost degradation on ecosystem albedo, energy partitioning and total climate forcing. Coordinated data acquisition will be performed using a variety of commonly-used terrestrial ecosystem characterization approaches as well as novel molecular microbiological, geophysical, isotopic and synchrotron techniques. These datasets will be used in parallel with models to identify the key controls on coupled geomechanical, hydrological, soil biogeochemical, vegetation and land-surface processes, as well as the manifestation of these coupled processes over a broad range of space and time

  3. How is climate warming altering the carbon cycle of a tundra ecosystem in the Siberian Arctic?

    NASA Astrophysics Data System (ADS)

    Belelli Marchesini, Luca; (Ko) van Huissteden, Jacobus; van der Molen, Michiel; Parmentier, Frans-Jan W.; Maximov, Trofim; Budishchev, Artem; Gallagher, Angela; (Han) Dolman, Albertus J.

    2015-04-01

    Climate has been warming over the the Arctic region with the strongest anomalies taking place in autumn and winter for the period 2000-2010, particularly in northern Eurasia. The quantification of the impact on climate warming on the degradation of permafrost and the associated potential release to the atmosphere of carbon stocked in the soil under the form of greenhouse gases, thus further increasing the radiative forcing of the atmosphere, is currently a matter of scientific debate. The positive trend in primary productivity in the last decades inferred by vegetation indexes (NDVI) and confirmed by observations on the enhanced growth of shrub vegetation represents indeed a contrasting process that, if prevalent could offset GHG emissions or even strengthen the carbon sink over the Arctic tundra. At the site of Kytalyk, in north-eastern Siberia, net fluxes of CO2 at ecosystem scale (NEE) have been monitored by eddy covariance technique since 2003. While presenting the results of the seasonal (snow free period) and inter-annual variability of NEE, conceived as the interplay between meteorological drivers and ecosystem responses, we test the role of climate as the main source of NEE variability in the last decade using a data oriented statistical approach. The impact of the timing and duration of the snow free period on the seasonal carbon budget is also considered. Finally, by including the results of continuous micrometeorological observations of methane fluxes taken during summer 2012, corroborated with seasonal CH4 budgets from two previous shorter campaigns (2008, 2009), as well as an experimentally determined estimate of dissolved organic carbon (DOC) flux, we provide an assessment of the carbon budget and its stability over time. The examined tundra ecosystem was found to sequester CO2 during the snow free season with relatively small inter-annual variability (-97.9±12.1gC m-2) during the last decade and without any evident trend despite the carbon uptake

  4. Advanced Ecosystem Mapping Techniques for Large Arctic Study Domains Using Calibrated High-Resolution Imagery

    NASA Astrophysics Data System (ADS)

    Macander, M. J.; Frost, G. V., Jr.

    2015-12-01

    Regional-scale mapping of vegetation and other ecosystem properties has traditionally relied on medium-resolution remote sensing such as Landsat (30 m) and MODIS (250 m). Yet, the burgeoning availability of high-resolution (<=2 m) imagery and ongoing advances in computing power and analysis tools raises the prospect of performing ecosystem mapping at fine spatial scales over large study domains. Here we demonstrate cutting-edge mapping approaches over a ~35,000 km² study area on Alaska's North Slope using calibrated and atmospherically-corrected mosaics of high-resolution WorldView-2 and GeoEye-1 imagery: (1) an a priori spectral approach incorporating the Satellite Imagery Automatic Mapper (SIAM) algorithms; (2) image segmentation techniques; and (3) texture metrics. The SIAM spectral approach classifies radiometrically-calibrated imagery to general vegetation density categories and non-vegetated classes. The SIAM classes were developed globally and their applicability in arctic tundra environments has not been previously evaluated. Image segmentation, or object-based image analysis, automatically partitions high-resolution imagery into homogeneous image regions that can then be analyzed based on spectral, textural, and contextual information. We applied eCognition software to delineate waterbodies and vegetation classes, in combination with other techniques. Texture metrics were evaluated to determine the feasibility of using high-resolution imagery to algorithmically characterize periglacial surface forms (e.g., ice-wedge polygons), which are an important physical characteristic of permafrost-dominated regions but which cannot be distinguished by medium-resolution remote sensing. These advanced mapping techniques provide products which can provide essential information supporting a broad range of ecosystem science and land-use planning applications in northern Alaska and elsewhere in the circumpolar Arctic.

  5. The resilience and functional role of moss in boreal and arctic ecosystems

    SciTech Connect

    Turetsky, Merritt; Bond-Lamberty, Benjamin; Euskirchen, Eugenie S.; Talbot, Julie; Frolking, Steve; McGuire, A. David; Tuittila, Eeva-Stiina

    2012-08-24

    Mosses in boreal and arctic ecosystems are ubiquitous components of plant communities, represent an important component of plant diversity, and strongly influence the cycling of water, nutrients, energy and carbon. Here we use a literature review and synthesis as well as model simulations to explore the role of moss in ecological stability and resilience. Our literature review of moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories in boreal and arctic regions. Our modeling simulations suggest that loss of moss within northern plant communities will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. While two models (HPM and STM-TEM) showed a significant effect of moss removal, results from the Biome-BGC and DVM-TEM models suggest that northern, moss-rich ecosystems would need to experience extreme perturbation before mosses were eliminated. We highlight a number of issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, phenotypical plasticity in traits, and whether the effects of moss on ecosystem processes scale with local abundance. We also suggest that as more models explore issues related to ecological resilience, issues related to both parameter and conceptual uncertainty should be addressed: are the models more limited by uncertainty in the parameterization of the processes included or by what is not represented in the model at all? It seems clear from our review that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species.

  6. Observed and Potential Responses of Upland Tundra Ecosystems to a Changing Climate: Results from the Arctic Long-Term Ecological Research Project, North Slope, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Bowden, W. B.

    2014-12-01

    permafrost in the arctic region approaches the 0ºC tipping point, the combination of presses and pulses may radically and rapidly alter upland tundra terrestrial and aquatic ecosystems. These changes will almost certainly occur more rapidly than would be the case if the region were influenced by the press of warming temperature alone.

  7. Review: Potential catastrophic reduction of sea ice in the western Arctic Ocean: Its impact on biogeochemical cycles and marine ecosystems

    NASA Astrophysics Data System (ADS)

    Harada, Naomi

    2016-01-01

    The reduction of sea ice in the Arctic Ocean, which has progressed more rapidly than previously predicted, has the potential to cause multiple environmental stresses, including warming, acidification, and strengthened stratification of the ocean. Observational studies have been undertaken to detect the impacts on biogeochemical cycles and marine ecosystems of these environmental stresses in the Arctic Ocean. Satellite analyses show that the reduction of sea ice has been especially great in the western Arctic Ocean. Observations and model simulations have both helped to clarify the impact of sea-ice reductions on the dynamics of ecosystem processes and biogeochemical cycles. In this review, I focus on the western Arctic Ocean, which has experienced the most rapid retreat of sea ice in the Arctic Ocean and, very importantly, has a higher rate of primary production than any other area of the Arctic Ocean owing to the supply of nutrient-rich Pacific water. I report the impact of the current reduction of sea ice on marine biogeochemical cycles in the western Arctic Ocean, including lower-trophic-level organisms, and identify the key mechanism of changes in the biogeochemical cycles, based on published observations and model simulations. The retreat of sea ice has enhanced primary production and has increased the frequency of appearance of mesoscale anticyclonic eddies. These eddies enhance the light environment and replenish nutrients, and they also represent a mechanism that can increase the rate of the biological pump in the Arctic Ocean. Various unresolved issues that require further investigation, such as biological responses to environmental stressors such as ocean acidification, are also discussed.

  8. Improved Climate Prediction through a System Level Understanding of Arctic Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Wullschleger, S. D.; Graham, D. E.; Hinzman, L. D.; Hubbard, S. S.; Liang, L.; Liljedahl, A. K.; Norby, R. J.; Rogers, A.; Rowland, J. C.; Thornton, P. E.; Torn, M. S.; Riley, W. J.; Wilson, C. J.

    2012-12-01

    Characterized by vast amounts of carbon stored in permafrost and a rapidly evolving landscape, the Arctic has emerged as an important focal point for the study of climate change. These are sensitive systems, yet the mechanisms responsible for those sensitivities are not well understood and many remain uncertain in terms of their representation in Earth System models. Increasing our confidence in climate projections for high-latitude regions of the world will require a coordinated set of investigations that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. Initial research focuses on the highly dynamic landscapes of the North Slope where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. Activities in the early stage of the project are focused on the Barrow Environmental Observatory (BEO), where a multi-disciplinary team of scientists will study interactions that drive critical climate feedbacks within these environments through greenhouse gas fluxes and changes in surface energy balance associated with permafrost degradation, and the many processes that arise as a result of these landscape dynamics. Our scaling approach builds on the hypothesis that the transfer of information across spatial scales can be organized around these discrete geomorphological units for which processes are represented explicitly at finer scales, with information passed to coarser scales through sub-grid parameterization of Earth System models. By extending an already well-established framework for fractional sub-grid area representations to allow dynamic sub-grid areas and hydrological and geophysical connections among sub-grid units, we expect to be able to characterize

  9. Ecosystem dynamics of the Pacific-influenced Northern Bering and Chukchi Seas in the Amerasian Arctic

    NASA Astrophysics Data System (ADS)

    Grebmeier, Jacqueline M.; Cooper, Lee W.; Feder, Howard M.; Sirenko, Boris I.

    2006-10-01

    The shallow continental shelves and slope of the Amerasian Arctic are strongly influenced by nutrient-rich Pacific waters advected over the shelves from the northern Bering Sea into the Arctic Ocean. These high-latitude shelf systems are highly productive both as the ice melts and during the open-water period. The duration and extent of seasonal sea ice, seawater temperature and water mass structure are critical controls on water column production, organic carbon cycling and pelagic-benthic coupling. Short food chains and shallow depths are characteristic of high productivity areas in this region, so changes in lower trophic levels can impact higher trophic organisms rapidly, including pelagic- and benthic-feeding marine mammals and seabirds. Subsistence harvesting of many of these animals is locally important for human consumption. The vulnerability of the ecosystem to environmental change is thought to be high, particularly as sea ice extent declines and seawater warms. In this review, we focus on ecosystem dynamics in the northern Bering and Chukchi Seas, with a more limited discussion of the adjoining Pacific-influenced eastern section of the East Siberian Sea and the western section of the Beaufort Sea. Both primary and secondary production are enhanced in specific regions that we discuss here, with the northern Bering and Chukchi Seas sustaining some of the highest water column production and benthic faunal soft-bottom biomass in the world ocean. In addition, these organic carbon-rich Pacific waters are periodically advected into low productivity regions of the nearshore northern Bering, Chukchi and Beaufort Seas off Alaska and sometimes into the East Siberian Sea, all of which have lower productivity on an annual basis. Thus, these near shore areas are intimately tied to nutrients and advected particulate organic carbon from the Pacific influenced Bering Shelf-Anadyr water. Given the short food chains and dependence of many apex predators on sea ice, recent

  10. Effects on the structure of Arctic ecosystems in the short- and long-term perspectives.

    PubMed

    Callaghan, Terry V; Björn, Lars Olof; Chernov, Yuri; Chapin, Terry; Christensen, Torben R; Huntley, Brian; Ims, Rolf A; Johansson, Margareta; Jolly, Dyanna; Jonasson, Sven; Matveyeva, Nadya; Panikov, Nicolai; Oechel, Walter; Shaver, Gus; Henttonen, Heikki

    2004-11-01

    Species individualistic responses to warming and increased UV-B radiation are moderated by the responses of neighbors within communities, and trophic interactions within ecosystems. All of these responses lead to changes in ecosystem structure. Experimental manipulation of environmental factors expected to change at high latitudes showed that summer warming of tundra vegetation has generally led to smaller changes than fertilizer addition. Some of the factors manipulated have strong effects on the structure of Arctic ecosystems but the effects vary regionally, with the greatest response of plant and invertebrate communities being observed at the coldest locations. Arctic invertebrate communities are very likely to respond rapidly to warming whereas microbial biomass and nutrient stocks are more stable. Experimentally enhanced UV-B radiation altered the community composition of gram-negative bacteria and fungi, but not that of plants. Increased plant productivity due to warmer summers may dominate food-web dynamics. Trophic interactions of tundra and sub-Arctic forest plant-based food webs are centered on a few dominant animal species which often have cyclic population fluctuations that lead to extremely high peak abundances in some years. Population cycles of small rodents and insect defoliators such as the autumn moth affect the structure and diversity of tundra and forest-tundra vegetation and the viability of a number of specialist predators and parasites. Ice crusting in warmer winters is likely to reduce the accessibility of plant food to lemmings, while deep snow may protect them from snow-surface predators. In Fennoscandia, there is evidence already for a pronounced shift in small rodent community structure and dynamics that have resulted in a decline of predators that specialize in feeding on small rodents. Climate is also likely to alter the role of insect pests in the birch forest system: warmer winters may increase survival of eggs and expand the range

  11. Effects of wildfire on source-water quality and aquatic ecosystems, Colorado Front Range

    USGS Publications Warehouse

    Writer, Jeffrey H.; McClelskey, R. Blaine; Murphy, Sheila F.

    2012-01-01

    Watershed erosion can dramatically increase after wildfire, but limited research has evaluated the corresponding influence on source-water quality. This study evaluated the effects of the Fourmile Canyon wildfire (Colorado Front Range, USA) on source-water quality and aquatic ecosystems using high-frequency sampling. Dissolved organic carbon (DOC) and nutrient loads in stream water were evaluated for a one-year period during different types of runoff events, including spring snowmelt, and both frontal and summer convective storms. DOC export from the burned watershed did not increase relative to the unburned watershed during spring snowmelt, but substantial increases in DOC export were observed during summer convective storms. Elevated nutrient export from the burned watershed was observed during spring snowmelt and summer convective storms, which increased the primary productivity of stream biofilms. Wildfire effects on source-water quality were shown to be substantial following high-intensity storms, with the potential to affect drinking-water treatment processes.

  12. Introduction to the effects of wildland fire on aquatic ecosystems in the Western USA

    USGS Publications Warehouse

    Rieman, B.; Gresswell, Robert E.; Young, M.; Luce, C.

    2003-01-01

    The management of wildfire has long been controversial. The role of fire and fire-related management in terrestrial and aquatic ecosystems has become an important focus in recent years, but the general debate is not new. In his recent book, Stephen Pyne (2001)describes the political and scientific debate surrounding the creation of the U.S. Forest Service and the emergence of fire suppression as a central tenet of wildland management. Essentially, views in the first decade of the 20th century focused on fire as good or evil: a tool that might benefit other resources or interests (e.g. Indian burning) and mitigate larger more destructive fires, or a threat to the recruitment and productivity of newly designated forest reserves. The “great fires” in the Western USA in 1910 and the associated loss of human life and property largely forged the public and political will to suppress fire on a massive scale.

  13. Mapping critical loads of nitrogen deposition for aquatic ecosystems in the Rocky Mountains, USA

    USGS Publications Warehouse

    Nanus, Leora; Clow, David W.; Saros, Jasmine E.; Stephens, Verlin C.; Campbell, Donald H.

    2012-01-01

    Spatially explicit estimates of critical loads of nitrogen (N) deposition (CLNdep) for nutrient enrichment in aquatic ecosystems were developed for the Rocky Mountains, USA, using a geostatistical approach. The lowest CLNdep estimates (-1 yr-1) occurred in high-elevation basins with steep slopes, sparse vegetation, and abundance of exposed bedrock and talus. These areas often correspond with areas of high N deposition (>3 kg N ha-1 yr-1), resulting in CLNdep exceedances ≥1.5 ± 1 kg N ha-1 yr-1. CLNdep and CLNdep exceedances exhibit substantial spatial variability related to basin characteristics and are highly sensitive to the NO3- threshold at which ecological effects are thought to occur. Based on an NO3- threshold of 0.5 μmol L-1, N deposition exceeds CLNdep in 21 ± 8% of the study area; thus, broad areas of the Rocky Mountains may be impacted by excess N deposition, with greatest impacts at high elevations.

  14. Managing wastewater effluent to enhance aquatic receiving ecosystem productivity: a coastal lagoon in Western Australia.

    PubMed

    Machado, Daniel A; Imberger, Jörg

    2012-05-30

    Large amounts of waste are generated in urban centers that if properly managed could promote ecological services. In order to promote nutrient cycling and productivity without endangering aquatic ecosystems, management of wastewater treatment and effluent discharges to receiving waters must be assessed on a case-by-case basis. We applied this premise to examine a municipal wastewater treated effluent discharge in a shallow oligotrophic coastal lagoon in Western Australia. Three-dimensional hydrodynamic-ecological modeling (ELCOM-CAEDYM) was used to assess the reaction of ecosystem for effluent quality. Two scenarios were evaluated for the summer 2000-2001 period, the actual or "current" (conventional secondary treatment) and an "alternative" (involving substitution of biological nutrient removal by advanced treatment). The residence time of the simulated numerical domain averaged 8.4 ± 1.3 days. For the current scenario the model successfully estimated phytoplankton biomass, as chlorophyll-a concentration (Chl-a), that is within field-measured ranges and previously recorded levels. The model was able to reproduce nitrogen as the main limiting nutrient for primary production in the coastal ecosystem. Simulated surface Chl-a means were 0.26 (range 0.19-0.38) μg Chl-a/L for the current scenario and 0.37 (range 0.19-0.67) μg Chl-a/L for the alternative one. Comparison of the alternative scenario with field-measured Chl-a levels suggests moderate primary production increase (16-42%), within local historical variability. These results, suggest that such a scenario could be used, as part of a comprehensive wastewater management optimization strategy, to foster receiving ecosystem's productivity and related ecological services maintaining its oligotrophic state. PMID:22322127

  15. Trophic interactions determine the effects of drought on an aquatic ecosystem.

    PubMed

    Amundrud, Sarah L; Srivastava, Diane S

    2016-06-01

    Species interactions can be important mediators of community and ecosystem responses to environmental stressors. However, we still lack a mechanistic understanding of the indirect ecological effects of stress that arise via altered species interactions. To understand how species interactions will be altered by environmental stressors, we need to know if the species that are vulnerable to such stressors also have large impacts on the ecosystem. As predators often exhibit certain traits that are linked to a high vulnerability to stress (e.g., large body size, long generation time), as well as having large effects on communities (e.g., top-down trophic effects), predators may be particularly likely to mediate ecological effects of environmental stress. Other functional groups, like facilitators, are known to have large impacts on communities, but their vulnerability to perturbations remains undocumented. Here, we use aquatic insect communities in bromeliads to examine the indirect effects of an important stressor (drought) on community and ecosystem responses. In a microcosm experiment, we manipulated predatory and facilitative taxa under a range of experimental droughts, and quantified effects on community structure and ecosystem function. Drought, by adversely affecting the top predator, had indirect cascading effects on the entire food web, altering community composition and decomposition. We identified the likely pathway of how drought cascaded through the food web from the top-down as drought -->predator --> shredder --> decomposition. This stress-induced cascade depended on predators exhibiting both a strong vulnerability to drought and large impacts on prey (especially shredders), as well as shredders exhibiting high functional importance as decomposers. PMID:27459778

  16. Progestins as endocrine disrupters in aquatic ecosystems: Concentrations, effects and risk assessment.

    PubMed

    Fent, Karl

    2015-11-01

    In aquatic ecosystems, progesterone (P4) and synthetic progestins (gestagens) originate from excretion by humans and livestock. Synthetic progestins are used for contraception and as P4 for medical treatments as well. Despite significant use, their ecotoxicological implications are poorly understood. Only about 50% of the progestins in use have been analyzed for their environmental occurrence and effects in aquatic organisms. Here we critically summarize concentrations and effects of progestins in aquatic systems. P4 and progestins were mostly detected when analyzed for, and they occurred in the low ng/L range in wastewater and surface water. In animal farm waste and runoff, they reached up to several μg/L. P4 and synthetic progestins act through progesterone receptors but they also interact with other steroid hormone receptors. They act on the hypothalamus-pituitary-gonad axis, lead to oocyte maturation in female and sperm motility in male fish. Additionally, other pathways are affected as well, including the circadian rhythm. Effects of P4, mifepristone and eleven synthetic progestins have been studied in fish and a few compounds in frogs and mussels. Environmental risks may be associated with P4, dydrogesterone and medroxyprogesterone acetate, where transcriptional effects were found at highest environmental levels. Reproductive effects occurred at higher levels. However, norethindrone, levonorgestrel and norgestrel compromised reproduction at environmental (ng/L) concentrations. Thus, some of the progestins are very active endocrine disrupters. This review summarizes the current state of the art and highlights risks for fish. Further research is needed into environmental concentrations and effects of non-investigated progestins, unexplored modes of action, and the activity of mixtures of progestins and other steroids to fully assess their environmental risks. PMID:26276056

  17. Bioaccumulation of heavy metals in Mbaa River and the impact on aquatic ecosystem.

    PubMed

    Ajima, M N O; Nnodi, P C; Ogo, O A; Adaka, G S; Osuigwe, D I; Njoku, D C

    2015-12-01

    The bioaccumulation and toxic effects of heavy metals have caused ecological damage to aquatic ecosystem. In this study, concentration of heavy metals including zinc, lead, cadmium, iron, and copper were determined in the sediment and water as well as in the muscle, gill, and intestine of two fish species (Pelmatochromis guentheri and Pelmatochromis pulcher) of Mbaa River in Southeastern Nigeria. Samples were collected at three different spots from the river, and the level of heavy metals specified above were determined by atomic absorption spectroscopy (AAS) after a modified wet digestion process. The results indicated that sediment had the highest concentration of the heavy metals investigated while water had the lowest concentration. Fish tissues showed appreciable bioaccumulation of these metals as evidenced by a higher concentration profile when compared with that of water. Furthermore, the concentration of these heavy metals in water and their bioconcentration factor in the fish were above the recommended limit by WHO and FEPA, indicating that Mbaa River along Inyishi may not be suitable for drinking nor the fish safe for human consumption. The study also reveals the use of fish as bioindicator of aquatic environment. PMID:26597816

  18. Annual Cycle of Bacterial Secondary Production in Five Aquatic Habitats of the Okefenokee Swamp Ecosystem

    PubMed Central

    Murray, Robert E.; Hodson, Robert E.

    1985-01-01

    Rates of bacterial secondary production by free-living bacterioplankton in the Okefenokee Swamp are high and comparable to reported values for a wide variety of marine and freshwater ecosystems. Bacterial production in the water column of five aquatic habitats of the Okefenokee Swamp was substantial despite the acidic (pH 3.7), low-nutrient, peat-accumulating character of the environment. Incorporation of [3H]thymidine into cold-trichloroacetic acid-insoluble material ranged from 0.03 to 2.93 nmol liter−1 day−1) and corresponded to rates of bacterial secondary production of 3.4 to 342.2 μg of carbon liter−1 day−1 (mean, 87.8 μg of carbon liter−1 day−1). Bacterial production was strongly seasonal and appeared to be coupled to annual changes in temperature and primary production. Bacterial doubling times ranged from 5 h to 15 days and were fastest during the warm months of the year, when the biomass of aquatic macrophytes was high, and slowest during the winter, when the plant biomass was reduced. The high rates of bacterial turnover in Okefenokee waters suggest that bacterial growth is an important mechanism in the transformation of dissolved organic carbon into the nutrient-rich bacterial biomass which is utilized by microconsumers. PMID:16346757

  19. Characterizing the oxygen isotopic composition of phosphate sources to aquatic ecosystems.

    PubMed

    Young, Megan B; McLaughlin, Karen; Kendall, Carol; Stringfellow, William; Rollog, Mark; Elsbury, Katy; Donald, Elizabeth; Paytan, Adina

    2009-07-15

    The oxygen isotopic composition of dissolved inorganic phosphate (delta18Op) in many aquatic ecosystems is not in isotopic equilibrium with ambient water and, therefore, may reflect the source delta18Op. Identification of phosphate sources to water bodies is critical for designing best management practices for phosphate load reduction to control eutrophication. In order for delta18Op to be a useful tool for source tracking, the delta18Op of phosphate sources must be distinguishable from one another; however, the delta18Op of potential sources has not been well characterized. We measured the delta18Op of a variety of known phosphate sources, including fertilizers, semiprocessed phosphorite ore, particulate aerosols, detergents, leachates of vegetation, soil, animal feces, and wastewater treatment plant effluent. We found a considerable range of delta18Op, values (from +8.4 to +24.9 per thousand) for the various sources, and statistically significant differences were found between several of the source types. delta18Op measured in three different fresh water systems was generally not in equilibrium with ambient water. Although there is overlap in delta18Op values among the groups of samples, our results indicate that some sources are isotopically distinct and delta18Op can be used for identifying phosphate sources to aquatic systems. PMID:19708340

  20. PCB Food Web Dynamics Quantify Nutrient and Energy Flow in Aquatic Ecosystems.

    PubMed

    McLeod, Anne M; Paterson, Gordon; Drouillard, Ken G; Haffner, G Douglas

    2015-11-01

    Measuring in situ nutrient and energy flows in spatially and temporally complex aquatic ecosystems represents a major ecological challenge. Food web structure, energy and nutrient budgets are difficult to measure, and it is becoming more important to quantify both energy and nutrient flow to determine how food web processes and structure are being modified by multiple stressors. We propose that polychlorinated biphenyl (PCB) congeners represent an ideal tracer to quantify in situ energy and nutrient flow between trophic levels. Here, we demonstrate how an understanding of PCB congener bioaccumulation dynamics provides multiple direct measurements of energy and nutrient flow in aquatic food webs. To demonstrate this novel approach, we quantified nitrogen (N), phosphorus (P) and caloric turnover rates for Lake Huron lake trout, and reveal how these processes are regulated by both growth rate and fish life history. Although minimal nutrient recycling was observed in young growing fish, slow growing, older lake trout (>5 yr) recycled an average of 482 Tonnes·yr(-1) of N, 45 Tonnes·yr(-1) of P and assimilated 22 TJ yr(-1) of energy. Compared to total P loading rates of 590 Tonnes·yr(-1), the recycling of primarily bioavailable nutrients by fish plays an important role regulating the nutrient states of oligotrophic lakes. PMID:26437236

  1. Characterizing the oxygen isotopic composition of phosphate sources to aquatic ecosystems

    USGS Publications Warehouse

    Young, M.B.; McLaughlin, K.; Kendall, C.; Stringfellow, W.; Rollog, M.; Elsbury, K.; Donald, E.; Paytan, A.

    2009-01-01

    The oxygen isotopic composition of dissolved inorganic phosphate (δ18Op) in many aquatic ecosystems is not in isotopic equilibrium with ambient water and, therefore, may reflect the source δ18Op. Identification of phosphate sources to water bodies is critical for designing best management practices for phosphate load reduction to control eutrophication. In order for δ18O p to be a useful tool for source tracking, the δ18Op of phosphate sources must be distinguishable from one another; however, the δ18Op of potential sources has not been well characterized. We measured the δ18O p of a variety of known phosphate sources, including fertilizers, semiprocessed phosphorite ore, particulate aerosols, detergents, leachates of vegetation, soil, animal feces, and wastewater treatment plant effluent. We found a considerable range of δ18Op values (from +8.4 to +24.9‰) for the various sources, and statistically significant differences were found between several of the source types. δ18Op measured in three different fresh water systems was generally not in equilibrium with ambient water. Although there is overlap in δ18Op values among the groups of samples, our results indicate that some sources are isotopically distinct and δ18Op can be used for identifying phosphate sources to aquatic systems.

  2. Scaling hyporheic exchange and its influence on biogeochemical reactions in aquatic ecosystems

    USGS Publications Warehouse

    O'Connor, B.L.; Harvey, J.W.

    2008-01-01

    Hyporheic exchange and biogeochemical reactions are difficult to quantify because of the range in fluid-flow and sediment conditions inherent to streams, wetlands, and nearshore marine ecosystems. Field measurements of biogeochemical reactions in aquatic systems are impeded by the difficulty of measuring hyporheic flow simultaneously with chemical gradients in sediments. Simplified models of hyporheic exchange have been developed using Darcy's law generated by flow and bed topography at the sediment-water interface. However, many modes of transport are potentially involved (molecular diffusion, bioturbation, advection, shear, bed mobility, and turbulence) with even simple models being difficult to apply in complex natural systems characterized by variable sediment sizes and irregular bed geometries. In this study, we synthesize information from published hyporheic exchange investigations to develop a scaling relationship for estimating mass transfer in near-surface sediments across a range in fluid-flow and sediment conditions. Net hyporheic exchange was quantified using an effective diffusion coefficient (De) that integrates all of the various transport processes that occur simultaneously in sediments, and dimensional analysis was used to scale De to shear stress velocity, roughness height, and permeability that describe fluid-flow and sediment characteristics. We demonstrated the value of the derived scaling relationship by using it to quantify dissolved oxygen (DO) uptake rates on the basis of DO profiles in sediments and compared them to independent flux measurements. The results support a broad application of the De scaling relationship for quantifying coupled hyporheic exchange and biogeochemical reaction rates in streams and other aquatic ecosystems characterized by complex fluid-flow and sediment conditions.

  3. Non-native earthworms in riparian soils increase nitrogen flux into adjacent aquatic ecosystems.

    PubMed

    Costello, David M; Lamberti, Gary A

    2008-12-01

    Riparian zones are an important transition between terrestrial and aquatic ecosystems, and they function in nutrient cycling and removal. Non-native earthworms invading earthworm-free areas of North America can affect nutrient cycling in upland soils and have the potential to affect it in riparian soils. We examined how the presence of earthworms can affect riparian nutrient cycling and nutrient delivery to streams. Two mesocosm experiments were conducted to determine how (1) the biomass of earthworms and (2) earthworm species can affect nutrient flux from riparian zones to nearby streams and how this flux can affect streamwater nutrients and periphyton growth. In separate experiments, riparian soil cores were amended with one of four mixed earthworm biomasses (0, 4, 10, or 23 g m(-2) ash-free dry mass) or with one of three earthworm species (Aporrectodea caliginosa, Lumbricus terrestris, L. rubellus) or no earthworm species. Riparian soil cores were coupled to artificial streams, and over a 36-day period, we measured nutrient leaching rates, in-stream nutrient concentrations, and periphyton growth. Ammonium leaching increased with increasing biomass and was greatest from the A. caliginosa treatments. Nitrate leaching increased through time and increased at a greater rate with higher biomass and from cores containing A. caliginosa. We suggest that the overall response of increased nitrate leaching [90% of total nitrogen (N)] was due to a combination of ammonium excretion and burrowing by earthworms, which increased nitrification rates. During both experiments, periphyton biomass increased through time but did not differ across treatments despite high in-stream inorganic N. Through time, in-stream phosphorus (P) concentration declined to <5 microg l(-1), and periphyton growth was likely P-limited. We conclude that activities of non-native earthworms (particularly A. caliginosa) can alter biogeochemical cycling in riparian zones, potentially reducing the N

  4. Mammalian herbivores confer resilience of Arctic shrub-dominated ecosystems to changing climate.

    PubMed

    Kaarlejärvi, Elina; Hoset, Katrine S; Olofsson, Johan

    2015-09-01

    Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub-dominated systems to warming by studying the change of shrub biomass after a cessation of long-term experimental warming in a forest-tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low-biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub-dominated ecosystems to climate warming. PMID:25967156

  5. Solar energy development and aquatic ecosystems in the southwestern United States: potential impacts, mitigation, and research needs.

    PubMed

    Grippo, Mark; Hayse, John W; O'Connor, Ben L

    2015-01-01

    The cumulative impacts of utility-scale solar energy facilities on aquatic ecosystems in the Southwestern United States are of concern, considering the many existing regional anthropogenic stressors. We review the potential impacts of solar energy development on aquatic habitat and biota. The greatest potential for impacts is related to the loss, fragmentation, or prolonged drying of ephemeral water bodies and drainage networks resulting from the loss of desert washes within the construction footprint of the facility. Groundwater-dependent aquatic habitat may also be affected by operational groundwater withdrawal in the case of water-intensive solar technologies. Solar panels have also been found to attract aquatic insects and waterbirds, potentially resulting in mortality. Avoiding construction activity near perennial and intermittent surface waters is the primary means of reducing impacts on aquatic habitats, followed by measures to minimize erosion, sedimentation, and contaminant inputs into waterways. Currently, significant data gaps make solar facility impact assessment and mitigation more difficult. Examples include the need for more regional and site-specific studies of surface-groundwater connectivity, more detailed maps of regional stream networks and riparian vegetation corridors, as well as surveys of the aquatic communities inhabiting ephemeral streams. In addition, because they often lack regulatory protection, there is also a need to develop valuation criteria for ephemeral waters based on their ecological and hydrologic function within the landscape. By addressing these research needs, we can achieve the goal of greater reliance on solar energy, while at the same time minimizing impacts on desert ecosystems. PMID:25331641

  6. Solar Energy Development and Aquatic Ecosystems in the Southwestern United States: Potential Impacts, Mitigation, and Research Needs

    NASA Astrophysics Data System (ADS)

    Grippo, Mark; Hayse, John W.; O'Connor, Ben L.

    2015-01-01

    The cumulative impacts of utility-scale solar energy facilities on aquatic ecosystems in the Southwestern United States are of concern, considering the many existing regional anthropogenic stressors. We review the potential impacts of solar energy development on aquatic habitat and biota. The greatest potential for impacts is related to the loss, fragmentation, or prolonged drying of ephemeral water bodies and drainage networks resulting from the loss of desert washes within the construction footprint of the facility. Groundwater-dependent aquatic habitat may also be affected by operational groundwater withdrawal in the case of water-intensive solar technologies. Solar panels have also been found to attract aquatic insects and waterbirds, potentially resulting in mortality. Avoiding construction activity near perennial and intermittent surface waters is the primary means of reducing impacts on aquatic habitats, followed by measures to minimize erosion, sedimentation, and contaminant inputs into waterways. Currently, significant data gaps make solar facility impact assessment and mitigation more difficult. Examples include the need for more regional and site-specific studies of surface-groundwater connectivity, more detailed maps of regional stream networks and riparian vegetation corridors, as well as surveys of the aquatic communities inhabiting ephemeral streams. In addition, because they often lack regulatory protection, there is also a need to develop valuation criteria for ephemeral waters based on their ecological and hydrologic function within the landscape. By addressing these research needs, we can achieve the goal of greater reliance on solar energy, while at the same time minimizing impacts on desert ecosystems.

  7. Net Ecosystem Exchange of CO2 with Rapidly Changing High Arctic Landscapes

    NASA Astrophysics Data System (ADS)

    Emmerton, C. A.

    2015-12-01

    High Arctic landscapes are expansive and changing rapidly. However our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest-latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near zero sink of atmospheric CO2 (NEE: -0.3±13.5 g C m-2). A nearby meadow wetland accumulated over two magnitudes more carbon (NEE: -79.3±20.0 g C m-2) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southern latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely-detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote-sensing, however high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases substantially, climate-related changes of dry high Arctic landscapes may be restricted by poor soil moisture retention, and therefore have some inertia against

  8. Aquatic Ecosystems, Water Quality, and Global Change: Challenges of Conducting Multi-Stressor Vulnerability Assessments (Final Report)

    EPA Science Inventory

    This report investigates the issues and challenges associated with identifying, calculating, and mapping indicators of the relative vulnerability of water quality and aquatic ecosystems, across the United States, to the potential impacts of global change. Using a large set of en...

  9. Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

    USGS Publications Warehouse

    Stow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.; Noyle, B.; Silapaswan, C.; Douglas, D.; Griffith, B.; Jia, G.; Epstein, H.; Walker, D.; Daeschner, S.; Petersen, A.; Zhou, L.; Myneni, R.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. ?? 2003 Elsevier Inc. All rights reserved.

  10. Remote sensing of vegetation and land-cover change in Arctic tundra ecosystems

    USGS Publications Warehouse

    Checkstow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.

  11. The response of aboveground plant productivity to earlier snowmelt and summer warming in an Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Livensperger, C.; Steltzer, H.; Darrouzet-Nardi, A.; Sullivan, P.; Wallenstein, M. D.; Weintraub, M. N.

    2012-12-01

    Plant communities in the Arctic are undergoing changes in structure and function due to shifts in seasonality from changing winters and summer warming. These changes will impact biogeochemical cycling, surface energy balance, and functioning of vertebrate and invertebrate communities. To examine seasonal controls on aboveground net primary production (ANPP) in a moist acidic tundra ecosystem in northern Alaska, we shifted the growing season by accelerating snowmelt (using radiation absorbing shadecloth) and warming air and soil temperature (using 1 m2 open-top chambers), individually and in combination. After three years, we measured ANPP by harvesting up to 16 individual ramets, tillers and rhizomes for each of 7 plant species, including two deciduous shrubs, two graminoids, two evergreen shrubs and one forb during peak season. Our results show that ANPP per stem summed across the 7 species increased when snow melt occurred earlier. However, standing biomass, excluding current year growth, was also greater. The ratio of ANPP/standing biomass decreased in all treatments compared to the control. ANPP per unit standing biomass summed for the four shrub species decreases due to summer warming alone or in combination with early snowmelt; however early snowmelt alone did not lead to lower ANPP for the shrubs. ANPP per tiller or rhizome summed for the three herbaceous species increased in response to summer warming. Understanding the differential response of plants to changing seasonality will inform predictions of future Arctic plant community structure and function.

  12. Hydrological and geochemical response and recovery in disturbed Arctic ecosystems. Progress report

    SciTech Connect

    Not Available

    1992-07-01

    This progress report is a funding, extension request to continue the database work for the Hydrological and Geochemical Response and Recovery in Disturbed Arctic Ecosystems Program. Throughout the period from 1985 to 1992 the Department of Energy supported research on the hydrology and geochemistry of the headwater basin of Imnavait Creek has focused on the quantification of the input from atmospheric sources of biologically significant and other related chemical variables; the transport of these variables in surface and subsurface flow and their efflux from the basin; and the development of geochemical budgets. The acquisition of multi-year data sets (the longest and most detailed sets in the Arctic) have made it possible to define seasonal ranges and amplitudes; determine spatial and temporal relationships within the different flow compartments; to begin to model the pathways and rates of movement through and across different landscape units. The length of record has also made it possible to examine the quantity and influence of local and extra-regional additions.

  13. Influences of seasonality, geomorphology, and hydrology on primary production and respiration in Arctic stream ecosystems

    NASA Astrophysics Data System (ADS)

    Herstand, M. R.; Bowden, W. B.; Gooseff, M. N.; Whittinghill, K. A.; Wlostowski, A. N.; Wollheim, W. M.

    2011-12-01

    Stream ecosystem processes in the Arctic are poorly understood in the spring and fall 'shoulder' seasons. We hypothesize that seasonal changes in solar radiation, hydrologic conditions, and landscape inputs are all reflected in the seasonal patterns of Gross Primary Productivity (GPP) and Community Respiration (CR). We continuously monitored the GPP and CR of three streams with different geomorphic characteristics (alluvial lake inlet, alluvial lake outlet, and beaded peat) near Toolik Lake Field Station, Alaska from breakup to freeze-up during 2011. We used open-system whole stream metabolism (WSM) methods, with dissolved oxygen estimates every five minutes. Dissolved and particulate nutrient chemistry, benthic chlorophyll, and nutrient uptake rates from solute injections were also measured across the seasons, and had correlations with GPP and CR. The fall freeze-up season was especially productive, as the well-developed benthic community responded to either lower flows (preventing sloughing) and/or increasing dissolved nutrient loads during landscape plant senescence. Storm events and high flow conditions (observed throughout seasons) decreased the GPP:CR ratio. Average monthly air temperatures have increased on the North Slope, especially during the shoulder seasons, increasing the duration of the ice-free stream season. Increasing the fall shoulder season may increase the annual stream GPP and nutrient uptake, with uncertain impacts on nutrient loading to the Arctic Ocean.

  14. Derivation of guideline values for gold (III) ion toxicity limits to protect aquatic ecosystems.

    PubMed

    Nam, Sun-Hwa; Lee, Woo-Mi; Shin, Yu-Jin; Yoon, Sung-Ji; Kim, Shin Woong; Kwak, Jin Il; An, Youn-Joo

    2014-01-01

    This study focused on estimating the toxicity values of various aquatic organisms exposed to gold (III) ion (Au(3+)), and to propose maximum guideline values for Au(3+) toxicity that protect the aquatic ecosystem. A comparative assessment of methods developed in Australia and New Zealand versus the European Community (EC) was conducted. The test species used in this study included two bacteria (Escherichia coli and Bacillus subtilis), one alga (Pseudokirchneriella subcapitata), one euglena (Euglena gracilis), three cladocerans (Daphnia magna, Moina macrocopa, and Simocephalus mixtus), and two fish (Danio rerio and Oryzias latipes). Au(3+) induced growth inhibition, mortality, immobilization, and/or developmental malformations in all test species, with responses being concentration-dependent. According to the moderate reliability method of Australia and New Zealand, 0.006 and 0.075 mg/L of guideline values for Au(3+) were obtained by dividing 0.33 and 4.46 mg/L of HC5 and HC50 species sensitivity distributions (SSD) with an FACR (Final Acute to Chronic Ratio) of 59.09. In contrast, the EC method uses an assessment factor (AF), with the 0.0006 mg/L guideline value for Au(3+) being divided with the 48-h EC50 value for 0.60 mg/L (the lowest toxicity value obtained from short term results) by an AF of 1000. The Au(3+) guideline value derived using an AF was more stringent than the SSD. We recommend that more toxicity data using various bioassays are required to develop more accurate ecological risk assessments. More chronic/long-term exposure studies on sensitive endpoints using additional fish species and invertebrates not included in the current dataset will be needed to use other derivation methods (e.g., US EPA and Canadian Type A) or the "High Reliability Method" from Australia/New Zealand. Such research would facilitate the establishment of guideline values for various pollutants that reflect the universal effects of various pollutants in aquatic ecosystems. To

  15. Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections

    USGS Publications Warehouse

    Kaplan, J.O.; Bigelow, N.H.; Prentice, I.C.; Harrison, S.P.; Bartlein, P.J.; Christensen, T.R.; Cramer, W.; Matveyeva, N.V.; McGuire, A.D.; Murray, D.F.; Razzhivin, V.Y.; Smith, B.; Walker, D. A.; Anderson, P.M.; Andreev, A.A.; Brubaker, L.B.; Edwards, M.E.; Lozhkin, A.V.

    2003-01-01

    Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55??N, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to > 700 ppm) at high latitudes were slight compared with the effects of the change in climate.

  16. Are Hotspots Always Hotspots? The Relationship between Diversity, Resource and Ecosystem Functions in the Arctic

    PubMed Central

    Link, Heike; Piepenburg, Dieter; Archambault, Philippe

    2013-01-01

    The diversity-ecosystem function relationship is an important topic in ecology but has not received much attention in Arctic environments, and has rarely been tested for its stability in time. We studied the temporal variability of benthic ecosystem functioning at hotspots (sites with high benthic boundary fluxes) and coldspots (sites with lower fluxes) across two years in the Canadian Arctic. Benthic remineralisation function was measured as fluxes of oxygen, silicic acid, phosphate, nitrate and nitrite at the sediment-water interface. In addition we determined sediment pigment concentration and taxonomic and functional macrobenthic diversity. To separate temporal from spatial variability, we sampled the same nine sites from the Mackenzie Shelf to Baffin Bay during the same season (summer or fall) in 2008 and 2009. We observed that temporal variability of benthic remineralisation function at hotspots is higher than at coldspots and that taxonomic and functional macrobenthic diversity did not change significantly between years. Temporal variability of food availability (i.e., sediment surface pigment concentration) seemed higher at coldspot than at hotspot areas. Sediment chlorophyll a (Chl a) concentration, taxonomic richness, total abundance, water depth and abundance of the largest gallery-burrowing polychaete Lumbrineristetraura together explained 42% of the total variation in fluxes. Food supply proxies (i.e., sediment Chl a and depth) split hot- from coldspot stations and explained variation on the axis of temporal variability, and macrofaunal community parameters explained variation mostly along the axis separating eastern from western sites with hot- or coldspot regimes. We conclude that variability in benthic remineralisation function, food supply and diversity will react to climate change on different time scales, and that their interactive effects may hide the detection of progressive change, particularly at hotspots. Time-series of benthic functions and

  17. Effects of anthropogenic nitrogen input on the aquatic food webs of river ecosystem in central Japan

    NASA Astrophysics Data System (ADS)

    Ohte, N.; Togashi, H.; Tokuchi, N.; Yoshimura, M.; Kato, Y.; Ishikawa, N. F.; Osaka, K.; Kondo, M.; Tayasu, I.

    2014-12-01

    To evaluate the impact of the anthropogenic nitrogen input to the river ecosystem, we conducted the monitoring on nutrient status of river waters and food web structures of aquatic organisms. Especially, changes of sources and concentration of nitrate (NO3-) in river water were focused to evaluate the impact of anthropogenic nitrogen loadings from agricultural and residential areas. Stable nitrogen isotope ratio (δ15N) of aquatic organisms has also intensively been monitored not only to describe their food web structure, but also to detect the influences of extraneous nitrogen inputs. Field samplings an observation campaigns were conducted in the Arida river watershed located in central part of Japan at four different seasons from September 2011 to October 2012. Five observation points were set from headwaters to the point just above the brackish waters starts. Water samples for chemical analysis were taken at the observation points for each campaign. Organisms including leaf litters, benthic algae, aquatic insects, crustacean, and fishes were sampled at each point quantitatively. Results of the riverine survey utilizing 5 regular sampling points showed that δ15N of nitrate (NO3-) increased from forested upstream (˜2 ‰) to the downstream (˜7 ‰) due to the sewage loads and fertilizer effluents from agricultural area. Correspondingly the δ15N of benthic algae and aquatic insects increased toward the downstream. This indicates that primary producers of each reach strongly relied on the local N sources and it was utilized effectively in their food web. Simulation using a GIS based mixing model considering the spatial distributions of human population density and fertilizer effluents revealed that strongest impacts of N inputs was originated from organic fertilizers applied to orchards in the middle to lower parts of catchment. Differences in δ15N between primary producers and predators were 6-7 ‰ similarly at all sampling points. Food web structural

  18. Estimating Pan Arctic Net Ecosystem Exchange using Functional Relationships with Air temperature, Leaf Area Index and Photosynthetic Active Radiation

    NASA Astrophysics Data System (ADS)

    Mbufong, H.; Kusbach, A.; Lund, M.; Persson, A.; Christensen, T. R.; Tamstorf, M. P.; Connolly, J.

    2015-12-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) is often attributed to the high spatial heterogeneity of Arctic tundra. Current models of carbon exchange thus handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple NEE model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide data from 12 Arctic tundra sites. The model input parameters (fcsat, Rd and α) were estimated as a function of air temperature and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship. They describe the saturation flux, dark respiration and initial light use efficiency, respectively. While remotely sensed LAI is readily available as a MODIS Terra product (MCD15A3), air temperature was estimated from a direct relationship with MODIS land surface temperature (MOD11A2, LST). Therefore, no specific knowledge of the vegetation type is required. Preliminary results show the model captures the spatial heterogeneity of the Arctic tundra but so far, overestimates NEE on all 17 test sites which include heaths, bogs, fens, and tussock tundra vegetation. The final updated results and error assessment will be presented at the conference in December.

  19. Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem

    NASA Astrophysics Data System (ADS)

    Wilkman, E.; Oechel, W. C.; Zona, D.

    2013-12-01

    Eric Wilkman, Walter Oechel, Donatella Zona Comprising an area of more than 7 x 106 km2 and containing over 11% of the world's organic matter pool, Arctic terrestrial ecosystems are vitally important components of the global carbon cycle, yet their structure and functioning are sensitive to subtle changes in climate and many of these functional changes can have large effects on the atmosphere and future climate regimes (Callaghan & Maxwell 1995, Chapin et al. 2002). Historically these northern ecosystems have acted as strong C sinks, sequestering large stores of atmospheric C due to photosynthetic dominance in the short summer season and low rates of decomposition throughout the rest of the year as a consequence of cold, nutrient poor, and generally water-logged conditions. Currently, much of this previously stored carbon is at risk of loss to the atmosphere due to accelerated soil organic matter decomposition in warmer future climates (Grogan & Chapin 2000). Although there have been numerous studies on Arctic carbon dynamics, much of the previous soil flux work has been done at limited time intervals, due to both the harshness of the environment and labor and time constraints. Therefore, in June of 2013 an Ultraportable Greenhouse Gas Analyzer (UGGA - Los Gatos Research Inc.) was deployed in concert with the LI-8100A Automated Soil Flux System (LI-COR Biosciences) in Barrow, AK to gather high temporal frequency soil CO2 and CH4 fluxes from a wet sedge tundra ecosystem. An additional UGGA in combination with diffusive probes, installed in the same location, provides year-round soil and snow CO2 and CH4 concentrations. When used in combination with the recently purchased AlphaGUARD portable radon monitor (Saphymo GmbH), continuous soil and snow diffusivities and fluxes of CO2 and CH4 can be calculated (Lehmann & Lehmann 2000). Of particular note, measuring soil gas concentration over a diffusive gradient in this way allows one to separate both net production and

  20. Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

    NASA Astrophysics Data System (ADS)

    Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T. J.

    2016-05-01

    High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term data set on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted 7 days earlier over the past 33 years and that spring weather conditions—especially snowfall—drive yearly variation in ice-off timing. In the most well studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

  1. Stable isotope analysis of energy dynamics in aquatic ecosystems suggests trophic shifts following severe wildfire

    NASA Astrophysics Data System (ADS)

    Martens, A. M.; Silins, U.; Bladon, K. D.; Williams, C.; Wagner, M. J.; Luchkow, E.

    2015-12-01

    Wildfire alters landscapes and can have significant impacts on stream ecosystems. The 2003 Lost Creek wildfire was one of the most severe on Alberta's eastern rocky mountain slopes, resulting in elevated sediment production and nutrient (phosphorus, nitrogen, and carbon) export in impacted streams. These resulted in increased algal productivity and macroinvertebrate abundance and diversity, and as a result, fish in watersheds draining wildfire affected catchments were larger than those in the same age class from reference (unburned) watersheds. In the present investigation, stable isotope analysis of C and N was utilized to evaluate ecosystem energy dynamics and describe trophic relationships in those watersheds. Aquatic invertebrates from burned catchments showed enrichment in δ13C and δ15N relative to algae suggesting a reliance on algae (autochthony) as a primary source of energy. Invertebrates from unburned systems were depleted in δ13C relative to algae indicating reliance on allochthonous or terrestrial primary energy sources. Preliminary analysis of δ15N in macroinvertebrates showed slight enrichment in burned catchments suggesting a trophic shift. More comprehensive macroinvertebrate sampling and identification has been conducted; isotopic analysis will provide greater resolution of how specific families within feeding guilds have been affected by wildfire. This will provide more robust insights into how wildfires may impact stream ecology in mountain environments.

  2. Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

    USGS Publications Warehouse

    Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T.J.

    2016-01-01

    High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term dataset on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted seven days earlier over the past 33 years and that spring weather conditions – especially snowfall – drive yearly variation in ice-off timing. In the most well-studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll-a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

  3. Bioassessment of contaminant transport and distribution in aquatic ecosystems by chemical analysis of burrowing mayflies (Hexagenia)

    USGS Publications Warehouse

    Steingraeber, M.T.; Wiener, J.G.

    1995-01-01

    Burrowing mayfly nymphs (Ephemeroptera) inhabit and ingest fine-grained sediments and detritus that may be enriched with metals and persistent organic compounds. The burrowing nymphs can externally adsorb and internally assimilate these contaminants, providing a link for the food chain transfer of potentially toxic substances from sediments to organisms in higher trophic levels. The emergent adults are short-lived and do not feed, thus their gut contents do not contribute greatly to their total contaminant burden. These characteristics make Hexagenia spp. And certain other burrowing mayflies useful for assessing ecosystem contamination. General protocols are presented for the collection, processing and analysis of emergent mayflies to assess the spatial distribution and bioaccumulation of sediment-associated contaminants in aquatic ecosystems. Two essential components of this bioassessment approach are a network of on-site volunteers with the materials and instructions needed to correctly collect and store samples and quality assurance procedures to estimate the accuracy of chemical analyses. The utility of this approach is demonstrated with an example of its application to the Upper Mississippi River (USA). Determination of cadmium, mercury and polychlorinated biphenyl congeners in emergent Hexagenia bilineata from a 1250 km reach of this river revealed (1) several source areas of contaminants and (2) distinct patterns in the bioaccumulation (and apparent sediment-associated transport) of each residue on both small and large spatial scales.

  4. Isolating the effects of storm events on arctic aquatic bacteria: temperature, nutrients, and community composition as controls on bacterial productivity

    PubMed Central

    Adams, Heather E.; Crump, Byron C.; Kling, George W.

    2015-01-01

    Storm events can pulse nutrients and carbon from soils and provide an important subsidy to food webs in oligotrophic streams and lakes. Bacterial nutrient limitation and the potential response of stream aquatic bacteria to storm events was investigated in arctic tundra environments by manipulating both water temperature and inorganic nutrient concentrations in short (up to 4 days) and long duration (up to 2 weeks) laboratory mesocosm experiments. Inorganic N and P additions increased bacterial production (14C-labeled leucine uptake) up to seven times over controls, and warmer incubation temperatures increased the speed of this response to added nutrients. Bacterial cell numbers also increased in response to temperature and nutrient additions with cell-specific carbon uptake initially increasing and then declining after 2 days. Bacterial community composition (BCC; determined by means of 16S denaturing gradient gel electrophoresis fingerprinting) shifted rapidly in response to changes in incubation temperature and the addition of nutrients, within 2 days in some cases. While the bacteria in these habitats responded to nutrient additions with rapid changes in productivity and community composition, water temperature controlled the speed of the metabolic response and affected the resultant change in bacterial community structure, constraining the potential responses to pulsed nutrient subsidies associated with storm events. In all cases, at higher nutrient levels and temperatures the effect of initial BCC on bacterial activity was muted, suggesting a consistent, robust interaction of temperature, and nutrients controlling activity in these aquatic systems. PMID:25873916

  5. The Role of Remote Sensing in Modeling Landscape Change and Its Associated Carbon Cycle Impacts Across Terrestrial Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Hayes, D. J.; Goswami, S.; Jones, B. M.; Grosse, G.; Balser, A.; Wullschleger, S. D.

    2014-12-01

    Terrestrial ecosystems across the circumpolar Arctic region are undergoing unprecedented changes in structure and function as a result of rapid climate warming. Such changes have substantially altered energy, water and biogeochemical cycling in these regions, which has important global-scale consequences for climate and society. Recognizing the vulnerability of these ecosystems to change, scientists and decision-makers have identified a critical need for research that employs existing and new remote sensing technologies and methodologies to observe, monitor and understand changes in Arctic ecosystems. The unique capabilities provided by remote sensing imagery and data products have allowed us novel views of ecosystems and their dynamics over multiple scales in time and space across all regions of the globe. Here we offer a synthetic discussion of the recent and emerging science focused on understanding the dynamic landscape processes in Arctic terrestrial ecosystems using a variety of remotely-sensed information collected from passive and active sensors on ground-, aircraft- and satellite- based platforms. To consider the evolution of these technologies, methods and applications over recent decades, we look at key examples from the scientific literature that range from the use of radar sensors for local-scale characterization of active layer dynamics to the circumpolar-scale assessment of changes in vegetation productivity using long-term records of optical satellite imagery. This discussion has a particular focus on the use of remotely sensed data and products to parameterize, drive, evaluate and benchmark the modeling of Arctic ecosystem processes. We use these examples to demonstrate the opportunities for model-data integration, as well as to highlight the challenges of remote sensing studies in northern high latitude regions.

  6. Challenges in Modeling Disturbance Regimes and Their Impacts in Arctic and Boreal Ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    McGuire, A. D.; Rupp, T. S.; Kurz, W.

    2013-12-01

    Disturbances in arctic and boreal terrestrial ecosystems influence services provided by these ecosystems to society. In particular, changes in disturbance regimes in northern latitudes have uncertain consequences for the climate system. A major challenge for the scientific community is to develop the capability to predict how the frequency, severity and resultant impacts of disturbance regimes will change in response to future changes in climate projected for northern high latitudes. Here we compare what is known about drivers and impacts of wildfire, phytophagous insect pests, and thermokarst disturbance to illustrate the complexities in predicting future changes in disturbance regimes and their impacts in arctic and boreal regions. Much of the research on predicting fire has relied on the use of drivers related to fire weather. However, changes in vegetation, such as increases in broadleaf species, associated with intensified fire regimes have the potential to influence future fire regimes through negative feedbacks associated with reduced flammability. Phytophagous insect outbreaks have affected substantial portions of the boreal region in the past, but frequently the range of the tree host is larger than the range of the insect. There is evidence that a number of insect species are expanding their range in response to climate change. Major challenges to predicting outbreaks of phytophagous insects include modeling the effects of climate change on insect growth and maturation, winter mortality, plant host health, the synchrony of insect life stages and plant host phenology, and changes in the ranges of insect pests. Moreover, Earth System Models often simplify the representation of vegetation characteristics, e.g. the use of plant functional types, providing insufficient detail to link to insect population models. Thermokarst disturbance occurs when the thawing of ice-rich permafrost results in substantial ground subsidence. In the boreal forest, thermokarst can

  7. Managing aquatic ecosystems and water resources under multiple stress--an introduction to the MARS project.

    PubMed

    Hering, Daniel; Carvalho, Laurence; Argillier, Christine; Beklioglu, Meryem; Borja, Angel; Cardoso, Ana Cristina; Duel, Harm; Ferreira, Teresa; Globevnik, Lidija; Hanganu, Jenica; Hellsten, Seppo; Jeppesen, Erik; Kodeš, Vit; Solheim, Anne Lyche; Nõges, Tiina; Ormerod, Steve; Panagopoulos, Yiannis; Schmutz, Stefan; Venohr, Markus; Birk, Sebastian

    2015-01-15

    Water resources globally are affected by a complex mixture of stressors resulting from a range of drivers, including urban and agricultural land use, hydropower generation and climate change. Understanding how stressors interfere and impact upon ecological status and ecosystem services is essential for developing effective River Basin Management Plans and shaping future environmental policy. This paper details the nature of these problems for Europe's water resources and the need to find solutions at a range of spatial scales. In terms of the latter, we describe the aims and approaches of the EU-funded project MARS (Managing Aquatic ecosystems and water Resources under multiple Stress) and the conceptual and analytical framework that it is adopting to provide this knowledge, understanding and tools needed to address multiple stressors. MARS is operating at three scales: At the water body scale, the mechanistic understanding of stressor interactions and their impact upon water resources, ecological status and ecosystem services will be examined through multi-factorial experiments and the analysis of long time-series. At the river basin scale, modelling and empirical approaches will be adopted to characterise relationships between multiple stressors and ecological responses, functions, services and water resources. The effects of future land use and mitigation scenarios in 16 European river basins will be assessed. At the European scale, large-scale spatial analysis will be carried out to identify the relationships amongst stress intensity, ecological status and service provision, with a special focus on large transboundary rivers, lakes and fish. The project will support managers and policy makers in the practical implementation of the Water Framework Directive (WFD), of related legislation and of the Blueprint to Safeguard Europe's Water Resources by advising the 3rd River Basin Management Planning cycle, the revision of the WFD and by developing new tools for

  8. Regional-Scale Vegetation Dynamics in Patterned-Ground Ecosystems of Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Kelley, A. M.; Walker, D. A.; Jia, G. J.; Raynolds, M. K.

    2006-12-01

    Regional-scale patterns of vegetation have been analyzed along a number of climate gradients throughout the world; these spatial dynamics provide important insights into the controlling factors of vegetation and the potential plant responses to environmental change. Only a few studies to date have collectively examined the vegetation biomass and production of arctic tundra ecosystems and their relationships to broadly ranging climate variables. No prior study has taken a systematic and consistent approach to examining vegetation biomass patterns along the full temperature gradient of the arctic biome. An additional complicating factor for studying vegetation of arctic tundra is the high spatial variability associated with small patterned-ground features (e.g. non-sorted circles and small non-sorted polygons), resulting from intense freeze-thaw processes. In this study, we sampled and analyzed the aboveground plant biomass components of patterned-ground ecosystems in the Arctic of northern Alaska and Canada along an 1800-km north-south gradient that spans approximately 11 degrees C of mean July temperatures. At each of ten locations along the regional temperature gradient, we ran several 50-m transects and harvested the aboveground biomass of three 20 x 50 cm plots for each transect. Vegetation biomass was dried, sorted by plant functional groups and tissue types, weighed, and analyzed as functions of the summer warmth index (SWI sum of mean monthly temperatures > 0). The absolute biomass (g/m2) of shrubs and graminoids increased exponentially with SWI, whereas forb and lichen biomass showed no change along the gradient. Moss biomass increased linearly with SWI, but with greater variabiliy than the other types. Relative aboveground biomass (% of total) of shrubs and graminoids increased with SWI, whereas percent lichen biomass decreased, and forbs again exhibited no significant change. Percentage of moss biomass was a parabolic function of SWI, with high relative

  9. Inuit exposure to organochlorines through the aquatic food chain in arctic Quebec

    SciTech Connect

    Dewailly, E.; Ayotte, P.; Laliberte, C. ); Bruneau, S. ); Muir, D.C.G. ); Norstrom, R.J. )

    1993-12-01

    Inuit people (Eskimos) are likely exposed to persistent organochlorine compounds because their traditional diet includes fatty tissues of the arctic marine biota. Here we present the results of organochlorine compound analysis in milk fat samples from artic Quebec Inuit women and in fat tissues from various animal species inhabiting that region. The total concentration of polychlorinated biphenyl congeners in Inuit milk fat was similar to that of the beluga, while the profile of the 10 congeners resembled that of the polar bear. Mean concentrations of various organochlorines in milk-fat samples from Inuit women were between 2 and 10 times greater than those found in samples previously collected from southern Quebec women. The Inuit mothers exhibit the greatest body burden known to occur from exposure to organochlorine residues present in the environment by virtue of their location at the highest trophic level of the arctic food web. 18 refs., 2 tabs.

  10. A multi-stable isotope framework to understand eutrophication in aquatic ecosystems.

    PubMed

    Gooddy, Daren C; Lapworth, Dan J; Bennett, Sarah A; Heaton, Tim H E; Williams, Peter J; Surridge, Ben W J

    2016-01-01

    Eutrophication is a globally significant challenge facing aquatic ecosystems, associated with human induced enrichment of these ecosystems with nitrogen (N) and phosphorus (P). However, the limited availability of inherent labels for P and N has constrained understanding of the triggers for eutrophication in natural ecosystems and appropriate targeting of management responses. This paper proposes and evaluates a new multi-stable isotope framework that offers inherent labels to track biogeochemical reactions governing both P and N in natural ecosystems. The framework couples highly novel analysis of the oxygen isotope composition of phosphate (δ(18)OPO4) with dual isotope analysis of oxygen and N within nitrate (δ(15)NNO3, δ(18)ONO3) and with stable N isotope analysis in ammonium (δ(15)NNH4). The River Beult in England is used as an exemplar system for initial evaluation of this framework. Our data demonstrate the potential to use stable isotope labels to track the input and downstream fate of nutrients from point sources, on the basis of isotopic differentiation for both P and N between river water and waste water treatment work effluent (mean difference = +1.7‰ for δ(18)OPO4; +15.5‰ for δ(15)NNH4 (under high flow); +7.3‰ for δ(18)ONO3 and +4.4‰ for δ(15)NNO3). Stable isotope data reveal nutrient inputs to the river upstream of the waste water treatment works that are consistent with partially denitrified sewage or livestock sources of nitrate (δ(15)NNO3 range = +11.5 to +13.1‰) and with agricultural sources of phosphate (δ(18)OPO4 range = +16.6 to +19.0‰). The importance of abiotic and metabolic processes for the in-river fate of N and P are also explored through the stable isotope framework. Microbial uptake of ammonium to meet metabolic demand for N is suggested by substantial enrichment of δ(15)NNH4 (by 10.2‰ over a 100 m reach) under summer low flow conditions. Whilst the concentration of both nitrate and phosphate

  11. Assessing Sources of Stress to Aquatic Ecosystems: Using Biomarkers and Bioindicators to Characterize Exodure-Response Profiles of Anthropogenic Activities

    SciTech Connect

    Adams, S.M.

    1999-03-29

    Establishing causal relationships between sources of environmental stressors and aquatic ecosystem health if difficult because of the many biotic and abiotic factors which can influence or modify responses of biological systems to stress, the orders of magnitude involved in extrapolation over both spatial and temporal scales, and compensatory mechanisms such as density-dependent responses that operate in populations. To address the problem of establishing causality between stressors and effects on aquatic systems, a diagnostic approach, based on exposure-response profiles for various anthropogenic activities, was developed to help identify sources of stress responsible for effects on aquatic systems at ecological significant levels of biological organization (individual, population, community). To generate these exposure-effects profiles, biomarkers of exposure were plotted against bioindicators of corresponding effects for several major anthropogenic activities including petrochemical , pulp and paper, domestic sewage, mining operations, land-development activities, and agricultural activities. Biomarkers of exposure to environmental stressors varied depending on the type of anthropogenic activity involved. Bioindicator effects, however, including histopathological lesions, bioenergetic status, individual growth, reproductive impairment, and community-level responses were similar among many of the major anthropogenic activities. This approach is valuable to help identify and diagnose sources of stressors in environments impacted by multiple stressors. By identifying the types and sources of environmental stressors, aquatic ecosystems can be more effectively protected and managed to maintain acceptable levels of environmental quality and ecosystem fitness.

  12. Bottom-up nutrient and top-down fish impacts on insect-mediated mercury flux from aquatic ecosystems.

    PubMed

    Jones, Taylor A; Chumchal, Matthew M; Drenner, Ray W; Timmins, Gabrielle N; Nowlin, Weston H

    2013-03-01

    Methyl mercury (MeHg) is one of the most hazardous contaminants in the environment, adversely affecting the health of wildlife and humans. Recent studies have demonstrated that aquatic insects biotransport MeHg and other contaminants to terrestrial consumers, but the factors that regulate the flux of MeHg out of aquatic ecosystems via emergent insects have not been studied. The authors used experimental mesocosms to test the hypothesis that insect emergence and the associated flux of MeHg from aquatic to terrestrial ecosystems is affected by both bottom-up nutrient effects and top-down fish consumer effects. In the present study, nutrient addition led to an increase in MeHg flux primarily by enhancing the biomass of emerging insects whose tissues were contaminated with MeHg, whereas fish decreased MeHg flux primarily by reducing the biomass of emerging insects. Furthermore, the authors found that these factors are interdependent such that the effects of nutrients are more pronounced when fish are absent, and the effects of fish are more pronounced when nutrient concentrations are high. The present study is the first to demonstrate that the flux of MeHg from aquatic to terrestrial ecosystems is strongly enhanced by bottom-up nutrient effects and diminished by top-down consumer effects. PMID:23180684

  13. Ice Shelf Microbial Ecosystems in the High Arctic and Implications for Life on Snowball Earth

    NASA Astrophysics Data System (ADS)

    Vincent, W. F.; Gibson, J. A. E.; Pienitz, R.; Villeneuve, V.; Broady, P. A.; Hamilton, P. B.; Howard-Williams, C.

    The Ward Hunt Ice Shelf (83°N, 74°W) is the largest remaining section of thick (>10m) landfast sea ice along the northern coastline of Ellesmere Island, Canada. Extensive meltwater lakes and streams occur on the surface of the ice and are colonized by photosynthetic microbial mat communities. This High Arctic cryo-ecosystem is similar in several of its physical, biological and geochemical features to the McMurdo Ice Shelf in Antarctica. The ice-mats in both polar regions are dominated by filamentous cyanobacteria but also contain diatoms, chlorophytes, flagellates, ciliates, nematodes, tardigrades and rotifers. The luxuriant Ward Hunt consortia also contain high concentrations (107-108cm-2) of viruses and heterotrophic bacteria. During periods of extensive ice cover, such as glaciations during the Proterozoic, cryotolerant mats of the type now found in these polar ice shelf ecosystems would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes.

  14. Ice shelf microbial ecosystems in the high arctic and implications for life on snowball earth.

    PubMed

    Vincent, W F; Gibson, J A; Pienitz, R; Villeneuve, V; Broady, P A; Hamilton, P B; Howard-Williams, C

    2000-03-01

    The Ward Hunt Ice Shelf (83 degrees N, 74 degrees W) is the largest remaining section of thick (> 10 m) land-fast sea ice along the northern coastline of Ellesmere Island, Canada. Extensive meltwater lakes and streams occur on the surface of the ice and are colonized by photosynthetic microbial mat communities. This High Arctic cryo-ecosystem is similar in several of its physical, biological and geochemical features to the McMurdo Ice Shelf in Antarctica. The ice-mats in both polar regions are dominated by filamentous cyanobacteria but also contain diatoms, chlorophytes, flagellates, ciliates, nematodes, tardigrades and rotifers. The luxuriant Ward Hunt consortia also contain high concentrations (10(7)-10(8) cm-2) of viruses and heterotrophic bacteria. During periods of extensive ice cover, such as glaciations during the Proterozoic, cryotolerant mats of the type now found in these polar ice shelf ecosystems would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes. PMID:10798200

  15. Coupled ecosystem carbon and nutrient cycling in a High Arctic ecosystem are altered by long-term experimental warming and higher rainfall

    NASA Astrophysics Data System (ADS)

    Schaeffer, S. M.; Schimel, J.; Welker, J. M.

    2013-12-01

    The rapid changes in temperature and precipitation in High Arctic tundra ecosystems are altering the biogeochemical cycles of nitrogen (N) and carbon (C), but in ways that are difficult to anticipate. The challenge grows from the complexity of tundra soil organic matter, the uncertainty of N cycle responses and the extent to which shifts in soil N processes are coupled with the C cycle, including leaf-level photosynthesis, gross ecosystem photosynthesis (GEP-productivity) and net CO2 exchange (NEE-C sequestration). Understanding the processes that are leading to changes in High Arctic biogeochemical processes are especially important today as soil organic C pools in the High Arctic are up to 6 times greater than previously estimated, and are sensitive to being oxidized to the atmosphere through changes in microbial decomposition associated with warmer and wetter conditions. We used a long-term (since 2003) experiment of summer warming and supplemental summer water additions to a High Arctic ecosystem in NW Greenland to determine the impact of interactions between temperature, water availability, and microbial metabolism on the cycling of C and plant-available N in High Arctic tundra soil. We have found that water availability plays a critical role in these cycles in High Arctic tundra, over and above that from temperature increases. On seasonal time scales, we observed greater net N mineralization under both global change scenarios, yet water addition also significantly increased net nitrification rates, loss of NO3--N via leaching from surface soil layers, and lowered rates of labile organic C and N production. We also expected the chronic warming and watering would lead to long-term changes in soil N-cycling that would be reflected in soil δ15N values. However, we found that soil δ15N decreased under the different climate change scenarios. Our findings indicate that warmer, wetter High Arctic tundra will be cycling N and C in ways that may transform these

  16. Development of an advanced regional climate-ecosystem model for Arctic applications

    NASA Astrophysics Data System (ADS)

    Chaudhary, Nitin; Smith, Benjamin; Miller, Paul

    2013-04-01

    Cryospheric processes together with their feedbacks play a crucial role in determining rates and patterns of future warming over high-latitude regions. Cryospheric processes including permafrost as well as peatland and associated vegetation, hydrological and biogeochemical dynamics are not well represented in land surface schemes (LSS) of most climate models. As a step in this direction, we describe a scheme to include the coupled dynamics of vegetation, hydrology and peat accumulation under climate forcing within a detailed vegetation dynamics-biogeochemistry model, LPJ GUESS (Smith et al. 2001; Miller et al., in preparation). In the first step, a one-dimensional (1D) landscape scale peat accumulation and two dimensional (2D) micro-topographical models have been developed. For the parameterisation and validation of these models, good quality datasets are being used which are collected at various locations around the Arctic. Building on these, a three-dimensional (3D) scheme will be incorporated in a version of LPJ-GUESS that already includes patch-scale vegetation dynamics and soil carbon cycling, as well as a one-dimensional hydrology scheme. The patches in the 3D model will be treated as adjacent micro-patches in a grid and depending on underlying micro-topography water will flow from higher to lower patches. The 2D and 3D models will help in simulating hummock and hollow structure which is typical for Northern peatlands based on the cyclic regeneration theory (von Post and Sernander, 1910). The resulting models will be incorporated within the biospheric component of a regional climate-ecosystem model, RCA-GUESS (Smith et al., 2010) and used to investigate feedbacks related to the dynamics of peatlands, permafrost and emissions of the greenhouse gases, mainly CO2 and CH4 across the Arctic region. References- Smith B, Prentice IC, and Skyes MT. 2001. Representation of vegetation dynamics in modelling of European ecosystems: comparison of two contrasting

  17. A case study of high Arctic anthropogenic disturbance to polar desert permafrost and ecosystems

    NASA Astrophysics Data System (ADS)

    Becker, M. S.; Pollard, W. H.

    2013-12-01

    One of the indirect impacts of climate change on Arctic ecosystems is the expected increase of industrial development in high latitudes. The scale of terrestrial impacts cannot be known ahead of time, particularly due to a lack of long-term impact studies in this region. With one of the slowest community recovery rates of any ecosystem, the high Artic biome will be under a considerable threat that is exacerbated by a high susceptibility to change in the permafrost thermal balance. One such area that provides a suitable location for study is an old airstrip near Eureka, Ellesmere Island, Nunavut (80.0175°N, 85.7340°W). While primarily used as an ice-runway for winter transport, the airstrip endured a yearly summer removal of vegetation that continued from 1947 until its abandonment in 1951. Since then, significant vegetative and geomorphic differences between disturbed and undisturbed areas have been noted in the literature throughout the decades (Bruggemann, 1953; Beschel, 1963; Couture and Pollard, 2007), but no system wide assessment of both the ecosystem and near-surface permafrost has been conducted. Key to our study is that the greatest apparent geomorphic and vegetative changes have occurred and persisted in areas where underlying ice-wedges have been disturbed. This suggests that the colonizing communities rapidly filled new available thermokarst niches and have produced an alternative ice-wedge stable state than the surrounding polar desert. We hypothesize that disturbed areas will currently have greater depths of thaw (deeper active layers) and degraded ice-wedges, with decreased vegetation diversity but higher abundance due to a changed hydrological balance. To test this a comprehensive set of near-surface active layer and ecosystem measurements were conducted. Permafrost dynamics were characterized using probing and high-frequency Ground Penetrating Radar (500 MHz) to map the near-surface details of ice-wedges and active layer. Vegetation was measured

  18. Relationships between ecosystem metabolism, benthic macroinvertebrate densities, and environmental variables in a sub-arctic Alaskan river

    USGS Publications Warehouse

    Benson, Emily R.; Wipfli, Mark S.; Clapcott, Joanne E.; Hughes, Nicholas F.

    2013-01-01

    Relationships between environmental variables, ecosystem metabolism, and benthos are not well understood in sub-arctic ecosystems. The goal of this study was to investigate environmental drivers of river ecosystem metabolism and macroinvertebrate density in a sub-arctic river. We estimated primary production and respiration rates, sampled benthic macroinvertebrates, and monitored light intensity, discharge rate, and nutrient concentrations in the Chena River, interior Alaska, over two summers. We employed Random Forests models to identify predictor variables for metabolism rates and benthic macroinvertebrate density and biomass, and calculated Spearman correlations between in-stream nutrient levels and metabolism rates. Models indicated that discharge and length of time between high water events were the most important factors measured for predicting metabolism rates. Discharge was the most important variable for predicting benthic macroinvertebrate density and biomass. Primary production rate peaked at intermediate discharge, respiration rate was lowest at the greatest time since last high water event, and benthic macroinvertebrate density was lowest at high discharge rates. The ratio of dissolved inorganic nitrogen to soluble reactive phosphorus ranged from 27:1 to 172:1. We found that discharge plays a key role in regulating stream ecosystem metabolism, but that low phosphorous levels also likely limit primary production in this sub-arctic stream.

  19. Arctic and boreal ecosystems of western North America as components of the climate system

    USGS Publications Warehouse

    Chapin, F. S., III; McGuire, A.D.; Randerson, J.; Pielke, R., Sr.; Baldocchi, D.; Hobbie, S.E.; Roulet, Nigel; Eugster, W.; Kasischke, E.; Rastetter, E.B.; Zimov, S.A.; Running, S.W.

    2000-01-01

    Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3??C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3-6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50-80% higher evapotranspiration, and therefore only 30-50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming. Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These

  20. Initial Impacts of the Mount Polley Tailings Pond Breach on Adjacent Aquatic Ecosystems

    NASA Astrophysics Data System (ADS)

    Petticrew, Ellen; Gantner, Nikolaus; Albers, Sam; Owens, Philip

    2015-04-01

    On August 4th 2014, the Mount Polley Tailings pond breach near Likely, B.C., released approximately 24 million cubic metres of tailings material into Polley Lake, Hazeltine Creek and Quesnel Lake. The discharge scoured and eroded a swath of soil and sediment delivering an unknown amount of metals and sediment into this tributary ecosystem of the Fraser River. Subsequent efforts by the mine operator to remediate by pumping tailings water from Polley Lake into Hazeltine Creek, which flows into Quesnel Lake, resulted in additional and continuous release of unknown volumes of contaminated water and sediments into the watershed. Heavy metals (e.g., selenium, copper, or mercury) reported as stored in the tailings pond entered the downstream aquatic environment and have been monitored in the water column of Quesnel Lake since August. These contaminants are likely particle-bound and thus subject to transport over long distances without appreciable degradation, resulting in the potential for chronic exposures and associated toxicological effects in exposed biota. While significant dilution is expected during aquatic transport, and the resulting concentrations in the water will likely be low, concentrations in exposed biota may become of concern over time. Metals such as mercury and selenium undergo bioaccumulation and biomagnification, once incorporated into the food chain/web. Thus, even small concentrations of such contaminants in water can lead to greater concentrations (~100 fold) in top predators. Over time, our predictions are that food web transfer will lead to an increase in concentrations from water (1-2 years)->invertebrates (1-2 yrs) ->fishes (2-5 yrs). Pacific salmon travel great distances in this watershed and may be exposed to contaminated water during their migrations. Resident species will be exposed to the contaminated waters and sediments in the study lakes year round. Little or no background/baseline data for metals in biota from Quesnel Lake exists

  1. Land use Controls on Water Quality and Aquatic Ecosystems in the Andean Amazon, Peru

    NASA Astrophysics Data System (ADS)

    Waggoner, L. A.; McClain, M. E.

    2007-05-01

    Agro-pastoral systems are replacing many of the tropical forests in the world, and much of this deforestation occurs in watersheds where people's livelihoods rely directly on water and aquatic resources in local streams and rivers. We examined relationships between land use and aquatic ecosystems in 34 catchments exhibiting a gradient of land use disturbance and human settlement in the Andean Amazon of Peru. Our research objectives were to 1) classify and characterize watershed land use and physical properties using remotely sensed data, 2) characterize the physical, biological and chemical conditions of streams 3) examine relationships between land use and water quality parameters at 3 scales: watershed, riparian and reach habitat and 4) translate research findings into management strategies that minimize disturbance and maximize ecosystem services. Primary forest was the dominant cover (68%) across the catchments, and the remaining study area was composed of: mixed forest (11.5%), grassland (10.75%) cropland (9.17%) and bare rock (0.02%). Among watersheds, forest cover ranged from 14% to 100%, mixed forest ranged from 0% to 26%, grassland ranged from 0% to 45% and cropland ranged from 0% to 26%. Physical habitat index scores ranged from 12.80 (very impaired) to 29.50 (reference conditions). Although nitrogen, phosphorous, dissolved organic carbon (DOC), pH, electric conductivity, and dissolved oxygen (DO), varied across sites, total concentrations remained within acceptable levels. Simpson's diversity and Family Biotic Index (FBI) were calculated for macroinvertebrates collected at each site; Simpson's diversity ranged from 0.24 to 0.95 and FBI ranged from 1.97 (excellent) to 7.49 (fairly poor). Forest cover at the watershed scale was the best explanatory variable and was positively correlated with inorganic phosphate (0.50), DO (0.90) and Simpson's diversity (0.46) and negatively correlated with organic phosphate (- 0.64), DOC (-0.75), water temperature (-0

  2. Ecosystems on ice: the microbial ecology of Markham Ice Shelf in the high Arctic.

    PubMed

    Vincent, Warwick F; Mueller, Derek R; Bonilla, Sylvia

    2004-04-01

    Microbial communities occur throughout the cryosphere in a diverse range of ice-dominated habitats including snow, sea ice, glaciers, permafrost, and ice clouds. In each of these environments, organisms must be capable of surviving freeze-thaw cycles, persistent low temperatures for growth, extremes of solar radiation, and prolonged dormancy. These constraints may have been especially important during global cooling events in the past, including the Precambrian glaciations. One analogue of these early Earth conditions is the thick, landfast sea ice that occurs today at certain locations in the Arctic and Antarctic. These ice shelves contain liquid water for a brief period each summer, and support luxuriant microbial mat communities. Our recent studies of these mats on the Markham Ice Shelf (Canadian high Arctic) by high performance liquid chromatography (HPLC) showed that they contain high concentrations of chlorophylls a and b, and several carotenoids notably lutein, echinenone and beta-carotene. The largest peaks in the HPLC chromatograms were two UV-screening compounds known to be produced by cyanobacteria, scytonemin, and its decomposition product scytonemin-red. Microscopic analyses of the mats showed that they were dominated by the chlorophyte genera cf. Chlorosarcinopsis, Pleurastrum, Palmellopsis, and Bracteococcus, and cyanobacteria of the genera Nostoc, Phormidium, Leptolyngbya, and Gloeocapsa. From point transects and localized sampling we estimated a total standing stock on this ice shelf of up to 11,200 tonnes of organic matter. These observations underscore the ability of microbial communities to flourish despite the severe constraints imposed by the cryo-ecosystem environment. PMID:15094087

  3. Transgenic Bacillus thuringiensis (Bt) rice is safer to aquatic ecosystems than its non-transgenic counterpart.

    PubMed

    Li, Guangsheng; Wang, Yongmo; Liu, Biao; Zhang, Guoan

    2014-01-01

    Rice lines genetically modified with the crystal toxin genes from Bacillus thuringiensis (Bt) have experienced rapid development, with biosafety certificates for two Bt rice lines issued in 2009. There has still been no commercial release of these lines yet due to public concerns about human health and environmental risks. Some studies confirmed that Bt rice was as safe as conventional rice to non-target organisms when pesticides were not applied, however, pesticides are still required in Bt rice to control non-lepidopteran pests. In this study, we assessed the environmental effects of two Bt rice lines expressing either the cry1Ab/1Ac or cry2A genes, respectively, by using zooplanktons as indicator species under normal field management practices using pesticides when required. In the whole rice growing season, non-Bt rice was sprayed 5 times while Bt rice was sprayed 2 times, which ensured both rice achieved a normal yield. Field investigations showed that rice type (Bt and non-Bt) significantly influenced zooplankton abundance and diversity, which were up to 95% and 80% lower in non-Bt rice fields than Bt rice fields. Laboratory rearing showed that water from non-Bt rice fields was significantly less suitable for the survival and reproduction of Daphnia magna and Paramecium caudatum in comparison with water from Bt rice fields. Higher pesticide residues were detected in the water from non-Bt than Bt rice fields, accounting for the bad performance of zooplankton in non-Bt field water. Our results demonstrate that Bt rice is safer to aquatic ecosystems than non-Bt rice, and its commercialization will be beneficial for biodiversity restoration in rice-based ecosystems. PMID:25105299

  4. Transgenic Bacillus thuringiensis (Bt) Rice Is Safer to Aquatic Ecosystems than Its Non-Transgenic Counterpart

    PubMed Central

    Li, Guangsheng; Wang, Yongmo; Liu, Biao; Zhang, Guoan

    2014-01-01

    Rice lines genetically modified with the crystal toxin genes from Bacillus thuringiensis (Bt) have experienced rapid development, with biosafety certificates for two Bt rice lines issued in 2009. There has still been no commercial release of these lines yet due to public concerns about human health and environmental risks. Some studies confirmed that Bt rice was as safe as conventional rice to non-target organisms when pesticides were not applied, however, pesticides are still required in Bt rice to control non-lepidopteran pests. In this study, we assessed the environmental effects of two Bt rice lines expressing either the cry1Ab/1Ac or cry2A genes, respectively, by using zooplanktons as indicator species under normal field management practices using pesticides when required. In the whole rice growing season, non-Bt rice was sprayed 5 times while Bt rice was sprayed 2 times, which ensured both rice achieved a normal yield. Field investigations showed that rice type (Bt and non-Bt) significantly influenced zooplankton abundance and diversity, which were up to 95% and 80% lower in non-Bt rice fields than Bt rice fields. Laboratory rearing showed that water from non-Bt rice fields was significantly less suitable for the survival and reproduction of Daphnia magna and Paramecium caudatum in comparison with water from Bt rice fields. Higher pesticide residues were detected in the water from non-Bt than Bt rice fields, accounting for the bad performance of zooplankton in non-Bt field water. Our results demonstrate that Bt rice is safer to aquatic ecosystems than non-Bt rice, and its commercialization will be beneficial for biodiversity restoration in rice-based ecosystems. PMID:25105299

  5. Spatial Variation of Atmospheric Nitrogen Deposition and Estimated Critical Loads for Aquatic Ecosystems in the Greater Yellowstone Area

    NASA Astrophysics Data System (ADS)

    Nanus, L.; McMurray, J. A.; Clow, D. W.; Saros, J. E.; Blett, T.

    2015-12-01

    Aquatic ecosystems at high-elevations in the Greater Yellowstone Area (GYA) are sensitive to the effects of atmospheric nitrogen (N) deposition. Current and historic N deposition has impacted aquatic ecosystems in the GYA and N deposition is increasing in many areas. Anticipated changes in atmospheric emissions may further affect these sensitive ecosystems. Understanding the spatial variation in atmospheric N deposition is needed to develop estimates of air pollution critical loads for aquatic ecosystems in complex terrain. For the GYA, high resolution (400 meter) maps were developed for 1993-2014 to identify areas of high loading of mean annual Total N deposition (wet + dry) and wet deposition of inorganic N (nitrate and ammonium). Total N deposition estimates in the GYA range from ≤ 1.4 to 7.5 kg N ha-1 yr-1 and show greater variability than inorganic N deposition. Spatially explicit estimates of critical loads of N deposition (CLNdep) for nutrient enrichment in aquatic ecosystems were developed using a geostatistical approach. CLNdep in the GYA ranges from less than 1.5 kg N ha-1 yr-1 to over 10 kg N ha-1 yr-1 and variability is controlled by differences in basin characteristics. The lowest CLNdep estimates occurred in high-elevation basins with steep slopes, sparse vegetation, and exposed bedrock, including areas within GYA Wilderness boundaries. These areas often have high inorganic N deposition (>3 kg N ha-1 yr-1), resulting in CLNdep exceedances greater than 1.5 kg N ha-1 yr-1. The N deposition maps were used to identify CLNdep exceedances for aquatic ecosystems, and to explore scale dependence and boundary issues related to estimating CLNdep. Based on a NO3- threshold of 1.0 μmol L-1, inorganic N deposition exceeds CLNdep in 12% of the GYA, and Total N deposition is in exceedance for 23% of the GYA. These maps can be used to help identify and protect sensitive ecosystems that may be impacted by excess N deposition in the GYA.

  6. CONTAMINATION OF U. S. ARCTIC ECOSYSTEMS BY LONG-RANGE TRANSPORT OF ATMOSPHERIC CONTAMINANTS

    EPA Science Inventory

    Various kinds of atmospheric pollutants are found in Arctic environments, including organic contaminants, radionuclides, and pollutants associated with fossil fuel combustion, smelting, and industrial development. hile some of these contaminants originate in the Arctic itself, ot...

  7. Ecosystem Respiration Rates of Arctic Tundra Mesocosms in Response to Cold-Season Temperatures

    NASA Astrophysics Data System (ADS)

    Oberbauer, S. F.; Moser, J. G.; Olivas, P. C.; Starr, G.; Mortazavi, B.

    2013-12-01

    The cold season in the Arctic extends over 8 to 9 mo, during which air temperatures often reach as low as -40 °C. However, as a result of the insulating layer created by snow cover, temperatures seldom fall below -15 °C, and are likely warm enough to support some metabolism. Little research has been conducted on arctic plants and tundra during the cold season, despite its length and the fact that warming is predicted to be greatest during this period. The primary focus of cold-season research has been on rates of winter ecosystem respiration (ER) for estimates of annual carbon balance. The majority of these measurements during the winter or at winter temperatures indicate that some respiration is occurring. Although rates are low, they may contribute substantially to the annual carbon balance because of the length of the cold season. However, estimates of respiration at low temperatures differ substantially, have been taken at different temperatures using different methodologies, and importantly almost none provide quantitative relationships across a range of temperatures. We measured respiration rates of intact arctic tundra monoliths from 15 to -15 °C at 5 °C steps to facilitate improved model estimates of tundra respiration. Six tundra monoliths (~900 cm2) taken from Toolik Field Station, Alaska were conditioned for the cold season in growth chambers at shortened photoperiods and low, but above-freezing temperatures. Desired temperatures were obtained with a combination of growth chambers and a modified freezer. The average of five samplings of [CO2] at each temperature step was used to estimate the ER rates. Measurements were conducted with a closed system using incubation periods of 30 to 180 min, depending on the temperature. Carbon dioxide concentrations were measured by syringe samples injected into a N2 gas stream flowing through an infrared gas analyzer. Rates of ER calculated on an area basis were close to zero at -15 °C, but increased steadily with

  8. Structural and functional effects of herbicides on non-target organisms in aquatic ecosystems with an emphasis on atrazine

    USGS Publications Warehouse

    Fairchild, James

    2011-01-01

    Agricultural production accounts for approximately 90% of herbicide use in the U.S. (Kiely et al., 2004). Gianessi and Reigner (2007) indicated that herbicides are routinely used on more than 90% of the area designated for large commercial crops including corn, soybeans, cotton, sugar beets, peanuts, and rice. Increased farm mechanization, technological advancements in production of inexpensive sources of inorganic nitrogen fertilizer (e.g., anhydrous ammonia), and conversion of forest, grassland, and wetland habitats to cropland has led to a tremendous increase in global food production over the past half-century. Herbicides have augmented advances in large-scale agricultural systems and have largely replaced mechanical and hand-weeding control mechanisms (Gianessi and Reigner, 2007). The wide-spread use of herbicides in agriculture has resulted in frequent chemical detections in surface and groundwaters (Gilliom, 2007). The majority of herbicides used are highly water soluble and are therefore prone to runoff from terrestrial environments. In additon, spray drift and atmospheric deposition can contribute to herbicide contamination of aquatic environments. Lastly, selected herbicides are deliberately applied to aquatic environments for controlling nuisance aquatic vegetation. Although aquatic herbicide exposure has been widely documented, these exposures are not necessarily related to adverse non-target ecological effects on natural communities in aquatic environments. This chapter evaluates the potential for effects of herbicides on the structure and function of aquatic envrionments at the population, community, and ecosystem levels of biological organization. In this manuscript I examine several critical aspects of the subject matter area: primary herbicides in use and chemical modes of action; the regulatory process used for registration and risk assessment of herbicides; data regarding non-target risks and the relative sensitivity of aquatic plants

  9. Ecological risk assessment of zinc from stormwater runoff to an aquatic ecosystem.

    PubMed

    Brix, Kevin V; Keithly, James; Santore, Robert C; DeForest, David K; Tobiason, Scott

    2010-03-15

    Zinc (Zn) risks from stormwater runoff to an aquatic ecosystem were studied. Monitoring data on waterborne, porewater, and sediment Zn concentrations collected at 20 stations throughout a stormwater collection/detention facility consisting of forested wetlands, a retention pond and first order stream were used to conduct the assessment. Bioavailability in the water column was estimated using biotic ligand models for invertebrates and fish while bioavailability in the sediment was assessed using acid volatile sulfide-simultaneously extracted metal (AVS-SEM). The screening level assessment indicated no significant risks were posed to benthic organisms from Zn concentrations in sediments and pore water. As would be expected for stormwater, Zn concentrations were temporally quite variable within a storm event, varying by factors of 2 to 4. Overall, probabilistic assessment indicated low (5-10% of species affected) to negligible risks in the system, especially at the discharge to the first order stream. Moderate to high risks (10-50% of species affected) were identified at sampling locations most upgradient in the collection system. The largest uncertainty with the assessment is associated with how best to estimate chronic exposure/risks from time-varying exposure concentrations. Further research on pulse exposure metal toxicity is clearly needed to assess stormwater impacts on the environment. PMID:20035970

  10. A methodological approach to characterize the resilience of aquatic ecosystems with application to Lake Annecy, France

    NASA Astrophysics Data System (ADS)

    Pinault, J.-L.; Berthier, F.

    2007-01-01

    We propose a methodological approach to characterize the resilience of aquatic ecosystems with respect to the evolution of environmental parameters as well as their aptitude to adapt to forcings. This method that is applied to Lake Annecy, France, proceeds in three stages. First, according to the depth, variations of physicochemical parameters versus time are separated into three components related to (1) energy transfer through the surface of the lake, (2) the flow of rivers and springs that feed the lake, and (3) long-term evolution of the benthic zone as a consequence of mineral and organic matter loads. Second, dynamics of the lake are deduced by analyzing the physicochemical parameter components related to the three boundary conditions. Third, a stochastic process associated with the transfer models aims to characterize the resilience of the lakes according to forcings. For Lake Annecy, whose dynamics are representative of oligotrophic stratified lakes controlled by decarbonation processes where turnover and mixing occurring once a year in winter, the major consequence is the impoverishment of dissolved oxygen in deep water in autumn due to a temperature increase of the surface water in summer. The simulation raises relevant questions about whether a connection exists between physicochemical parameters and global warming, which should not induce harmful consequences on water quality and biodiversity in deep water. This methodological approach is general since it does not use any physical conceptual model to predict the hydrosystem behavior but uses directly observed data.

  11. Aquatic ecotoxicology: from the ecosystem to the cellular and molecular levels.

    PubMed Central

    Boudou, A; Ribeyre, F

    1997-01-01

    This review of aquatic ecotoxicology is presented in three parts. First, we discuss the fundamental concepts and stress the importance of its ecological basis and the complexity and diversity of the field of investigation, which result from actions and interactions between the physicochemical characteristics of the biotopes, the structural and functional properties of the living organisms, and the contamination modalities. Ecotoxicological mechanisms, regardless of the level of biological complexity, primarily depend on the bioavailability of the toxic products. Numerous processes control the chemical fate of contaminants in the water column and/or sediment compartments; accessibility to the biological barriers that separate the organisms from their surrounding medium depends directly on bioavailability. Second, we review the principal methodologies of the field, from in situ studies at the ecosystem/ecocomplex level to bioassays or single species tests. Third, we focus on mercury, selected as a reference contaminant, in order to illustrate the main ecotoxicological concepts, the complementarity between field and laboratory studies, and the indispensable multidisciplinarity of the approaches. PMID:9114275

  12. A methodology for assessing the impact of mutagens on aquatic ecosystems. Final report

    SciTech Connect

    Knezovich, J.P.; Martinelli, R.E.

    1995-03-01

    Assessments of impacts of hazardous agents (i.e., chemical and physical mutagens) on human health have focused on defining the effects of chronic exposure on individuals, with cancer being the main effect of concern. In contrast, impacts on ecosystems have traditionally been gauged by the assessment of near-term organism mortality, which is clearly not a useful endpoint for assessing the long-term effects of chronic exposures. Impacts on individual organisms that affect the long-term survival of populations are much more important but are also more difficult to define. Therefore, methods that provide accurate measures of sub-lethal effects that are linked to population survival are required so that accurate assessments of environmental damage can be made and remediation efforts, if required, can be initiated. Radioactive substances have entered aquatic environments as a result of research and production activities, intentional disposal, and accidental discharges. At several DOE sites, surface waters and sediments are contaminated with radioactive and mutagenic materials. The accident at the Chernobyl power station in the former Soviet Union (FSU) has resulted in the contamination of biota present in the Kiev Reservoir. This documents presents a methodology which addresses the effects of a direct-acting mutagen (radiation) on aquantic organisms by applying sensitive techniques for assessing damage to genetic material.

  13. The combination of different carbon sources enhances bacterial growth efficiency in aquatic ecosystems.

    PubMed

    Fonte, Ellen S; Amado, André M; Meirelles-Pereira, Frederico; Esteves, Francisco A; Rosado, Alexandre S; Farjalla, Vinicius F

    2013-11-01

    The dissolved organic carbon (DOC) pool is composed of several organic carbon compounds from different carbon sources. Each of these sources may support different bacterial growth rates, but few studies have specifically analyzed the effects of the combination of different carbon sources on bacterial metabolism. In this study, we evaluated the response of several metabolic parameters, including bacterial biomass production (BP), bacterial respiration (BR), bacterial growth efficiency (BGE), and bacterial community structure, on the presence of three DOC sources alone and in combination. We hypothesized that the mixture of different DOC sources would increase the efficiency of carbon use by bacteria (BGE). We established a full-factorial substitutive design (seven treatments) in which the effects of the number and identity of DOC sources on bacterial metabolism were evaluated. We calculated the expected metabolic rates of the combined DOC treatments based on the single-DOC treatments and observed a positive interaction on BP, a negative interaction on BR, and, consequently, a positive interaction on BGE for the combinations. The bacterial community composition appeared to have a minor impact on differences in bacterial metabolism among the treatments. Our data indicate that mixtures of DOC sources result in a more efficient biological use of carbon. This study provides strong evidence that the mixture of different DOC sources is a key factor affecting the role of bacteria in the carbon flux of aquatic ecosystems. PMID:23963223

  14. Scaling relationships among drivers of aquatic respiration from the smallest to the largest freshwater ecosystems

    USGS Publications Warehouse

    Hall, Ed K; Schoolmaster, Donald; Amado, A.M; Stets, Edward G.; Lennon, J.T.; Domaine, L.; Cotner, J.B.

    2016-01-01

    To address how various environmental parameters control or constrain planktonic respiration (PR), we used geometric scaling relationships and established biological scaling laws to derive quantitative predictions for the relationships among key drivers of PR. We then used empirical measurements of PR and environmental (soluble reactive phosphate [SRP], carbon [DOC], chlorophyll a [Chl-a)], and temperature) and landscape parameters (lake area [LA] and watershed area [WA]) from a set of 44 lakes that varied in size and trophic status to test our hypotheses. We found that landscape-level processes affected PR through direct effects on DOC and temperature and indirectly via SRP. In accordance with predictions made from known relationships and scaling laws, scale coefficients (the parameter that describes the shape of a relationship between 2 variables) were found to be negative and have an absolute value 1, others <1). We also found evidence of a significant relationship between temperature and SRP. Because our dataset included measurements of respiration from small pond catchments to the largest body of freshwater on the planet, Lake Superior, these findings should be applicable to controls of PR for the great majority of temperate aquatic ecosystems.

  15. Mapping critical loads of nitrogen deposition for aquatic ecosystems in the Rocky Mountains, USA

    USGS Publications Warehouse

    Nanus, Leora; Clow, David W.; Saros, Jasmine E.; Stephens, Verlin C.; Campbell, Donald H.

    2012-01-01

    Spatially explicit estimates of critical loads of nitrogen (N) deposition (CLNdep) for nutrient enrichment in aquatic ecosystems were developed for the Rocky Mountains, USA, using a geostatistical approach. The lowest CLNdep estimates (−1 yr−1) occurred in high-elevation basins with steep slopes, sparse vegetation, and abundance of exposed bedrock and talus. These areas often correspond with areas of high N deposition (>3 kg N ha−1 yr−1), resulting in CLNdep exceedances ≥1.5 ± 1 kg N ha−1 yr−1. CLNdep and CLNdep exceedances exhibit substantial spatial variability related to basin characteristics and are highly sensitive to the NO3− threshold at which ecological effects are thought to occur. Based on an NO3− threshold of 0.5 μmol L−1, N deposition exceeds CLNdep in 21 ± 8% of the study area; thus, broad areas of the Rocky Mountains may be impacted by excess N deposition, with greatest impacts at high elevations.

  16. Assessment of the impact of chlorophyll derivatives to control parasites in aquatic ecosystems.

    PubMed

    Erzinger, Gilmar Sidnei; Souza, Suellen Carolina; Pinto, Luciano Henrique; Hoppe, Roberto; Del Ciampo, Lineu Fernando; Souza, Ozair; Correia, Cláudia Hack Gumz; Häder, Donat-Peter

    2015-05-01

    Several research groups have studied new biopesticides which are less toxic to the environment and capable of controlling the vectors of parasitic diseases, especially in aquatic ecosystems. Pest control by photodynamic substances is an alternative to chemical or other measures, with chlorophyll and its derivatives as the most studied substances supported by their easy availability and low production costs. The impact of chlorophyll derivatives on four different species, a small crustacean (Daphnia similis), a unicellular alga (Euglena gracilis) and two species of fish (Astyanax bimaculatus and Cyprynus carpio) were tested under short-term conditions. In addition, the effects of long-term exposure were evaluated in D. similis and E. gracilis. In short-term tests, mortality of D. similis (EC50 = 7.75 mg/L) was most strongly affected by chlorophyllin, followed by E. gracilis (EC50 = 12.73 mg/L). The fish species showed a greater resistance documented by their EC50 values of 17.58 and 29.96 mg/L in C. carpio and A. bimaculatus, respectively. A risk quotient is calculated by dividing an estimate of exposure by an estimate of effect. It indicated that chlorophyll derivatives can be applied in nature to control the vectors of parasitic diseases under short-term conditions, but long-term exposure requires new formulations. PMID:25750014

  17. Tracking Biological and Ecosystem Responses to Changing Environmental Conditions in the Pacific Arctic

    NASA Astrophysics Data System (ADS)

    Grebmeier, J. M.; Cooper, L. W.; Frey, K. E.; Moore, S. E.

    2014-12-01

    Changing seasonal sea ice conditions and seawater temperatures strongly influence biological processes and marine ecosystems at high latitudes. In the Pacific Arctic, persistent regions termed "hotspots", are localized areas with high benthic macroinfaunal biomass that have been documented over four decades (see Figure). These regions are now being more formally tracked to relate physical forcing and ecosystem response as an Arctic Distributed Biological Observatory (DBO) supported by the US National Ocean Policy Implementation Plan and international partners. These hotspots are important foraging areas for upper trophic level benthic feeders, such as marine mammals and seabirds. South of St. Lawrence Island (SLI) in the northern Bering Sea, benthic feeding spectacled eiders, bearded seals and walruses are important winter consumers of infauna, such as bivalves and polychaetes. Gray whales have historically been a major summer consumer of benthic amphipods in the Chirikov Basin to the north of SLI, although summertime sightings of gray whales declined in the Chirikov from the 1980s up until at least 2002. The SE Chukchi Sea hotspot, as are the other hotspots, is maintained by export of high chlorophyll a that is produced locally as well as advected by water masses transiting northward through the system. Both walrus and gray whales are known to forage in this hotspot seasonally on high biomass levels of benthic prey. Notably the center of the highest benthic biomass regions has shifted northward in three of the DBO hotspots in recent years. This has coincided with changing sediment grain size, an indicator of current speed, and is also likely a response to changes in primary production in the region. Studies of these broad biological responses to changing physical drivers have been facilitated through development of the DBO cooperative effort by both US and international scientists. The DBO includes a series of coordinated, multi-trophic level observations that

  18. Floods, fish, and people: Connecting biogeochemical fluxes to aquatic ecosystem functions and people (Invited)

    NASA Astrophysics Data System (ADS)

    Holtgrieve, G. W.; Arias, M. E.; Chheng, P.

    2013-12-01

    The Lower Mekong River basin, including Tonle Sap Lake (TSL), is the largest inland fishery in the world and a dominant source of protein and income for much of Southeast Asia. Maintaining ecosystem productivity in the face of large-scale environmental change from hydroelectric dams and climate change is critical for economic and social well-being in the region. Yet, we currently lack the most basic understanding of how hydrologic variation relates to fisheries production, nutritional quality, and ultimately livelihoods of people. We will describe past, present, and future research to establish mechanistic connections between the hydrology, ecology, and sustainability of the Mekong ecosystem. Past research includes application of a state-space oxygen mass balance model and continuous dissolved oxygen measurements from four locations to provide the first estimates of gross primary productivity (GPP) and ecosystem respiration (ER) for the Tonle Sap. GPP averaged 4.1 × 2.3 g O2 m-3 d-1 with minimal differences among sites, while ER averaged 24.9 × 20.0 g O2 m-3 d-1, but had greater than six-fold variation among sites. Using our measurements of GPP, we calibrated a hydrodynamic-productivity model and predicted aquatic net primary production of 2.0 × 0.2 g C m-2 d-1 (2.4 × 0.2 million tonnes C y-1). Present research is using stable isotope and fatty acid methyl ester biomarkers to investigate basal carbon sources to the fishery, focusing specifically on the role of biogenic methane oxidation in supporting the food web. Individuals a wide variety of taxa had tissue carbon isotope values (δ13C) ranging from -36 to -57 per mil. These extremely depleted values are best explained by utilization of biogenic methane by methane oxidizing bacteria (MOB) and subsequent grazing of these bacterial by benthic insects and ultimately fishes. The presence of MOB in the food web was confirmed by identifying 16:1ω8 and 18:1ω8 FAME biomarkers specific to these bacteria in fish

  19. Old river beds under urbanization pressure. Can we protect valuable aquatic ecosystems within the cities?

    NASA Astrophysics Data System (ADS)

    Sikorska, Daria; Sikorski, Piotr

    2016-04-01

    Old river channels are valuable ecosystems in the scale of whole Europe. Protected as Natura 2000 habitats they are characterized by high biodiversity and provide various ecosystem services. River regulation, eutrophication or lack of annual flooding result in an impoverishment and disappearance of these habitats. Moreover they are subjected to severe pressure from uncontrolled expansion of the cities. The aim of this study was to determine factors associated with urbanization mostly contributing to impoverishment of the vegetation associated with the old channels and to identify landscape characteristics favouring high diversity and naturalness. We were seeking for indices that could be implemented in spatial management for preservation of these ecosystems. Vegetation inventory of 28 lakes, being former river Vistula beds near Warsaw was held. The lakes were located in an urban-rural gradient from the city centre, suburban zone to rural areas. Mapping of vegetation was performed for aquatic vegetation, rushes and vegetation of the shores (321 relevés). Human pressure was assessed on the basis of landscape composition of the lakes neighbourhood, characteristic features of the reservoir and water physio-chemical properties. High diversity and naturalness of the vegetation associated with former Vistula River beds was proved. Effects of the human pressure in the vegetation composition were recognized in high share of alien species and impoverishment of native plants. Composition was dependant on the intensity of human pressure in the neighbourhood and was mostly related to percentage of built-up areas and road density. Selected measures allowed to explain not more than 30% of plants composition variation which implies strong effect of local factors. Vegetation composition of former river beds changed significantly along urban-rural gradient, though the trend could be noted only to the city border. Several protection activities were proposed favouring high

  20. Springs as Model Systems for Aquatic Ecosystems Ecology: Stoichiometry, Metabolism and Nutrient Limitation

    NASA Astrophysics Data System (ADS)

    Cohen, M. J.; Nifong, R. L.; Kurz, M. J.; Martin, J. B.; Cropper, W. P.; Korhnak, L. V.

    2013-12-01

    Springs have been called nature's chemostats, where low variation in discharge, temperature and chemistry creates a natural laboratory in which to address basic questions about aquatic ecosystems. Ecological stoichiometry posits that patterns of metabolism, trophic energy transfer and community structure arise in response to coupled elemental cycles. In this work we synthesize several recent studies in Florida's iconic springs to explore the overarching hypothesis that stoichiometry can be used to indicate the nutrient limitation status of autotrophs and ecosystem metabolism. Of foremost importance is that the chemically stable conditions observed in springs ensures that autotroph tissue elemental composition, which is thought to vary with environmental supply, is near steady state. Moreover, the elemental ratios of discharging water vary dramatically across our study springs (for example, molar N:P ranges from 0.4:1 to 400:1), subjecting the communities of autotrophs, which are largely conserved across systems, to dramatically different nutrient supply. At the scale of whole ecosystem metabolism, we show that C:N:P ratios are strongly conserved across a wide gradient of environmental supplies, counter to the prediction of stoichiometric plasticity. Moreover, the absence of a relationship between gross primary production and nutrient concentrations or stoichiometry suggests that metabolic homeostasis may be a diagnostic symptom of nutrient saturation. At the scale of individual autotrophs, both submerged vascular plants and filamentous algae, this finding is strongly reinforced, with remarkable within-species tissue C:N:P homeostasis over large gradients, and no statistically significant evidence that gradients in nutrient supply affect autotroph composition. Expanding the suite of elements for which contemporaneous environment and tissue measurements are available to include 19 metals and micronutrients revealed that, while plants were homeostatic across large N

  1. Large Aquatic Ecosystem Restoration Monitoring for Decision Makers: Monitoring to Target and Evaluate Success of Ecosystem Restoration

    EPA Science Inventory

    Monitoring ecosystem restoration at various scales in LAEs can be challenging, frustrating and rewarding. Some of the major ecosystem restoration monitoring occurring in LAEs include: seagrass expansion/contraction; dead zone sizes; oyster reefs; sea turtle nesting; toxic and nu...

  2. The interactive effects of excess reactive nitrogen and climate change on aquatic ecosystems and water resources of the United States

    USGS Publications Warehouse

    Baron, J.S.; Hall, E.K.; Nolan, B.T.; Finlay, J.C.; Bernhardt, E.S.; Harrison, J.A.; Chan, F.; Boyer, E.W.

    2012-01-01

    Nearly all freshwaters and coastal zones of the US are degraded from inputs of excess reactive nitrogen (Nr), sources of which are runoff, atmospheric N deposition, and imported food and feed. Some major adverse effects include harmful algal blooms, hypoxia of fresh and coastal waters, ocean acidification, long-term harm to human health, and increased emissions of greenhouse gases. Nitrogen fluxes to coastal areas and emissions of nitrous oxide from waters have increased in response to N inputs. Denitrification and sedimentation of organic N to sediments are important processes that divert N from downstream transport. Aquatic ecosystems are particularly important denitrification hotspots. Carbon storage in sediments is enhanced by Nr, but whether carbon is permanently buried is unknown. The effect of climate change on N transport and processing in fresh and coastal waters will be felt most strongly through changes to the hydrologic cycle, whereas N loading is mostly climate-independent. Alterations in precipitation amount and dynamics will alter runoff, thereby influencing both rates of Nr inputs to aquatic ecosystems and groundwater and the water residence times that affect Nr removal within aquatic systems. Both infrastructure and climate change alter the landscape connectivity and hydrologic residence time that are essential to denitrification. While Nr inputs to and removal rates from aquatic systems are influenced by climate and management, reduction of N inputs from their source will be the most effective means to prevent or to minimize environmental and economic impacts of excess Nr to the nation’s water resources.

  3. Marine ecosystem synthesis: From physics to whales in the Pacific Arctic

    NASA Astrophysics Data System (ADS)

    Sheffield Guy, Lisa; Moore, Sue E.; Stabeno, Phyllis

    2012-11-01

    Synthesis of Arctic Research (SOAR) Workshop; Anchorage, Alaska, 14-16 March 2012 The Synthesis of Arctic Research (SOAR) program brings together a multidisciplinary group of Arctic scientists and Alaskan coastal community residents to explore and integrate marine research information in the Pacific Arctic region. The goal of SOAR is to increase scientific understanding of the relationships among oceanographic conditions (physics, chemistry, sea ice), benthic organisms, lower trophic pelagic species (forage fish and zooplankton), and higher trophic species (i.e., seabirds, walrus, whales) in the Pacific Arctic, with particular emphasis on the Chukchi Sea oil and gas lease sale areas.

  4. Biomarker/bioindicator response profiles of organisms can help differentiate between sources of anthropogenic stressors in aquatic ecosystems.

    PubMed

    Adams, S M

    2001-01-01

    Aquatic ecosystems can be chronically stressed by multiple environmental factors which originate from a variety of point and non-point sources. In addition, these stressors may vary both spatially and temporally, and, combined with synergestic and cumulative interactions of these stressors, complicate the interpretation and evaluation of stress responses in organisms. To help identify and differentiate between sources of anthropogenic stressors in aquatic systems, a diagnostic approach based on exposure-response profiles in sentinel organisms was developed from the known effects of various anthropogenic activities on biological systems. To generate these exposure-effects profiles, biomarkers of exposure were plotted against bioindicators of corresponding effects for several major anthropogenic activities including petrochemical, pulp and paper, domestic sewage, mining operations, land-development, and agricultural activities. Biomarkers of exposure to environmental stressors varied widely depending on the type of anthropogenic activity involved. Bioindicator effects, however, including histopathological lesions, bioenergetic status, growth, reproductive impairment, and community-level endpoints were similar among several of the major anthropogenic activities because responses at these higher levels are less specific to stressors than are biomarkers. This approach appears useful for helping to identify and diagnose sources of stress in environments impacted by multiple stressors. By identifying the types and sources of environmental stressors impacting key components of biological systems, aquatic ecosystems can be more effectively protected, regulated, and managed to help improve and maintain environmental quality and ecosystem fitness. PMID:23886055

  5. Changing the seasonality of an Arctic tundra ecosystem: earlier snowmelt and warmer temperatures

    NASA Astrophysics Data System (ADS)

    Steltzer, H.; Weintraub, M. N.; Darrouzet-Nardi, A.; Melle, C.; Segal, A.; Sullivan, P.; Landry, C.; Wallenstein, M. D.

    2010-12-01

    In the Arctic and around the world, earlier plant growth is an indication that warmer temperatures or other global changes are changing the seasonality of the Earth’s ecosystems. To determine how changes in seasonality affect plant life histories and biogeochemical cycles in tussock tundra, we established a factorial experiment that includes two approaches to changing the seasonality of this ecosystem. In early May, we placed radiation absorbing fabric on the snow surface to accelerate the timing of snowmelt. We monitored the rate of snowmelt over a 10 day period and removed the fabric on the 10th day when the accelerated plots were 80% snowfree. Instrument arrays placed in the plots collected daily data that characterize an increase in energy absorption in these snowfree areas over the 4 day period prior to when control areas were snowfree. In addition, when the plots became snowfree we placed open-top-chambers in areas with and without accelerated snowmelt. The chambers increased air temperatures especially during mid-day early in the growing season. The instrument arrays included light sensors to monitor the plant community life history by observing surface greenness. Our results suggest that the plant community initiated growth earlier when snowmelt occurred earlier and that warming speeded the development of the plant canopy. However, plant species’ life history responses to these changes in seasonality were variable. Experimental alteration of the timing of plant life history events will provide a useful tool to examine controls on the seasonality of biogeochemical processes, such as nutrient availability to plants and nutrient limitation of decomposition. Accelerated snowmelt and warmer temperatures in tussock tundra, AK.

  6. Timing, Magnitude and Sources of Ecosystem Respiration in High Arctic Tundra of NW Greenland

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Xu, X.; Lett, C.; Maseyk, K. S.; Lindsey, D. S.; Thomas, J. S.; Welker, J. M.; Czimczik, C. I.

    2011-12-01

    High arctic ecosystems with low vegetation density contain significant stocks of organic carbon (C) in the form of soil organic matter that range in age from modern to ancient. How rapidly these C pools can be mineralized and lost to the atmosphere as CO2 (ecosystem respiration, ER) as a consequence of warming and, or changes in precipitation is a major uncertainty in our understanding of current and future arctic biogeochemistry and for predicting future levels of atmospheric CO2. In a 2-year study (2010-2011), we monitored seasonal changes in the magnitude, timing and sources of ER and soil pore space CO2 in the High Arctic of NW Greenland under current and simulated, future climate conditions. Measurements were taken from May to August at a multi-factorial, long-term climate change experiment in prostrate dwarf-shrub tundra on patterned ground with 5 treatments: (T1) +2oC warming, (T2) +4oC warming, (W) +50% summer precipitation, (T2W) +4oC + 50% summer precipitation, and (C) control. ER (using opaque chambers) and soil CO2 concentrations (wells) were monitored daily via infrared spectroscopy (LI-COR 800 & 840). The source of CO2 was inferred from its radiocarbon (14C) content analyzed at the AMS facility in UCI. CO2 was sampled monthly using molecular sieve traps (chambers) or evacuated canisters (wells). Highest rates of ER are observed on vegetated ground with a maximum in mid summer - reflecting a peak in plant productivity and soil temperature. Respiration rates from bare ground remain similar throughout the summer. Additional soil moisture, administered or due to precipitation events, strongly enhances ER from both vegetated and bare ground. Daily ER budget for the sampling period was of 53.1 mmol C m-2 day-1 for the (C) vegetated areas compared to the 60.0 for the (T2), 68.1 for the (T2W) or the 79.9 for the (W) treatment. ER was highly correlated to temperature (eg. C = 0.8; T2W = 0.8) until middle of July, when heavy precipitation started to occur. In

  7. Hydrologic Connectivity as a Window into Pattern Conditions and Formation Processes in Aquatic Ecosystems

    NASA Astrophysics Data System (ADS)

    Larsen, L. G.; Choi, J.; Nungesser, M. K.; Harvey, J. W.

    2011-12-01

    Patterned aquatic ecosystems exhibit different types and degrees of hydrologic connectivity, from isolated open-water patches in some inland marshes, to cross-slope strings and flarks of striped fens, to along-slope ridges and sloughs of low-gradient subtropical wetlands, to dendritic channels of coastal marshes. The nature and degree of this connectivity are closely linked to landscape function. For example, hydrologic connectivity perpendicular to river channel thalwegs relates to the exchange of sediment and nutrients between channels and floodplains, whereas connectivity parallel to a dominant flow direction affects fish migration or the likelihood of contaminant transport. Characteristics of hydrologic connectivity reflect not only the results of landscape pattern but also the mechanisms responsible for pattern creation. Quantifying those connectivity characteristics provides a robust means to identify landscapes likely formed under a consistent set of processes or to compare the output of landscape simulation models to actual landscapes in order to determine whether the models capture the most relevant landscape formation processes. However, established methods for quantifying isotropic patch connectivity are often ill suited for strongly patterned landscapes or hydroscapes in which directional flow is important. Using graph theory principles, we developed two alternative indices of directional hydrologic connectivity: the maximum flow index (MFI) and directional connectivity index (DCI), which quantify the connectivity of flow paths along a particular axis of interest. The MFI is sensitive to the existence of any hydrologic connection along the direction of interest, whereas the DCI is sensitive to the linearity of connections along that direction. Curves of directional connectivity over a range of angular bearings provide a quantitative, information-dense representation of landscape structure that can be related to subtle differences in the physical

  8. Foliar Expression of Parent Lithologic Composition in the Sub-Arctic: Examples from Heath Ecosystems of Abisko, Sweden.

    NASA Astrophysics Data System (ADS)

    Heim, E. W.; Tomczyk, N.; Remiszewski, K.; Bryce, J. G.; Frey, S. D.; Prado, M. F.; Varner, R. K.

    2014-12-01

    Climatic evolution and its effect on ecosystem stability through macronutrient acquisition is of particular interest in the fringe ecosystems of the Arctic and Sub-Arctic, regions predicted to face the most extreme temperature increases in Earth's changing climate. Accordingly enhanced understanding of climate change impacts on nutrient mobilization in recently glaciated terrains will factor importantly into accurate predictive models for future ecosystem health. Lithologic variation can lead to differences in geomorphic processes and thus influence landscape evolution [1]. Heath ecosystems in the region are developed on thin soils which place them close to parent material bedrock. Given the abundance of thin soils mantling bedrock, we assessed how bedrock geochemical content links with foliar composition of key macronutrients. We focused our studies on four sites near Abisko, Sweden (68°21'N 19°02'E) in metamorphosed sedimentary bedrock. In our sites the average annual air temperature has crossed the 0o threshold and has been linked to many cryospheric and ecological impacts [2]. Sites were chosen at the same elevation (700 m absl) and shared similar vegetation coverage. Three dominant species across our sampling sites include Betula nana, Empetrum nigrum, and Salix lapponum. E. Nigrum had consistent concentrations of foliar magnesium (Mg) and phosphorus (P) across the bedrock compositional gradients. B. nana and S. lapponum had consistently higher foliar Mg and P concentrations than E. nigrum across the gradients. Across a soil calcium (Ca) gradient, dominant species had a weak correlation between soil Ca and foliar Ca contents, R2 = 0.106. Soil Mg and P gradients were similarly poorly correlated with foliar abundances, R2 = -0.0228, and R2= -0.034 respectively. Expansion of our work into other lithologies will contribute towards improved predictive biogeochemical models of macronutrient acquisition and ecological evolution across changing Arctic ecosystems.

  9. Hematology of southern Beaufort Sea polar bears (2005-2007): Biomarker for an arctic ecosystem health sentinel

    USGS Publications Warehouse

    Kirk, Cassandra M.; Amstrup, S.; Swor, Rhonda; Holcomb, Darce; O'Hara, T. M.

    2010-01-01

    Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ???5, than lactating adult females ages ???5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel. ?? 2010 International Association for Ecology and Health.

  10. Long-term experimentally deepened snow decreases growing-season respiration in a low- and high-arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Semenchuk, Philipp R.; Christiansen, Casper T.; Grogan, Paul; Elberling, Bo; Cooper, Elisabeth J.

    2016-05-01

    Tundra soils store large amounts of carbon (C) that could be released through enhanced ecosystem respiration (ER) as the arctic warms. Over time, this may change the quantity and quality of available soil C pools, which in-turn may feedback and regulate ER responses to climate warming. Therefore, short-term increases in ER rates due to experimental warming may not be sustained over longer periods, as observed in other studies. One important aspect, which is often overlooked, is how climatic changes affecting ER in one season may carry-over and determine ER in following seasons. Using snow fences, we increased snow depth and thereby winter soil temperatures in a high-arctic site in Svalbard (78°N) and a low-arctic site in the Northwest Territories, Canada (64°N), for 5 and 9 years, respectively. Deepened snow enhanced winter ER while having negligible effect on growing-season soil temperatures and soil moisture. Growing-season ER at the high-arctic site was not affected by the snow treatment after 2 years. However, surprisingly, the deepened snow treatments significantly reduced growing-season ER rates after 5 years at the high-arctic site and after 8-9 years at the low-arctic site. We speculate that the reduction in ER rates, that became apparent only after several years of experimental manipulation, may, at least in part, be due to prolonged depletion of labile C substrate as a result of warmer soils over multiple cold seasons. Long-term changes in winter climate may therefore significantly influence annual net C balance not just because of increased wintertime C loss but also because of "legacy" effects on ER rates during the following growing seasons.

  11. Effect of pesticides used in banana and pineapple plantations on aquatic ecosystems in Costa Rica.

    PubMed

    Diepens, Noël J; Pfennig, Sascha; Van den Brink, Paul J; Gunnarsson, Jonas S; Ruepert, Clemens; Castillo, Luisa E

    2014-01-01

    Current knowledge on fate and effect of agricultural pesticides comes is mainly from temperate ecosystems. More studies are needed in tropical systems in order to assess contamination risks to nontarget endemic tropical species from the extensive use of pesticides e.g. in banana and pineapple plantations. In this study, acute laboratory toxicity tests with organophosphate pesticides ethoprophos and chlorpyrifos were conducted on two Costa Rican species, cladoceran Daphnia ambigua and fish Parachromis dovii. Tests showed that chlorpyrifos was more toxic than ethoprophos to D. ambigua and P. dovii and that D. ambigua was also more sensitive than P. dovii to both pesticides. Additionally, bioassays were performed by exposing D. magna and P. dovii to contaminated water collected from the field. Chemical analyses of field water revealed that fungicides were generally the most frequent pesticide group found, followed by insecticides/nematicides and herbicides. The bioassays and values obtained from the literature confirmed that D. magna was more sensitive to pesticide contamination than P. dovii and that D. ambigua was more sensitive than D. magna, suggesting that the native cladoceran is a more suitable test species than its temperate counterpart. Species sensitivity distributions showed no significant difference in sensitivity between tropical and temperate fish and the arthropod species exposed to chlorpyrifos in this study. Choline esterase activity (ChE) was measured in P. dovii in laboratory tests in order to assess the applicability of this biomarker. ChE inhibition in P. dovii was observed in the laboratory at levels below the LC10 of both ethoprophos and chlorpyrifos, confirming that ChE is an efficient biomarker of exposure. Both indigenous Costa Rican species used in this study were found to be suitable standard tropical test species. Further studies are needed to investigate how protective the safe environmental concentrations, derived from LC50 of native

  12. Organic-matter loading determines regime shifts and alternative states in an aquatic ecosystem

    PubMed Central

    Sirota, Jennie; Baiser, Benjamin; Gotelli, Nicholas J.; Ellison, Aaron M.

    2013-01-01

    Slow changes in underlying state variables can lead to “tipping points,” rapid transitions between alternative states (“regime shifts”) in a wide range of complex systems. Tipping points and regime shifts routinely are documented retrospectively in long time series of observational data. Experimental induction of tipping points and regime shifts is rare, but could lead to new methods for detecting impending tipping points and forestalling regime shifts. By using controlled additions of detrital organic matter (dried, ground arthropod prey), we experimentally induced a shift from aerobic to anaerobic states in a miniature aquatic ecosystem: the self-contained pools that form in leaves of the carnivorous northern pitcher plant, Sarracenia purpurea. In unfed controls, the concentration of dissolved oxygen ([O2]) in all replicates exhibited regular diurnal cycles associated with daytime photosynthesis and nocturnal plant respiration. In low prey-addition treatments, the regular diurnal cycles of [O2] were disrupted, but a regime shift was not detected. In high prey-addition treatments, the variance of the [O2] time series increased until the system tipped from an aerobic to an anaerobic state. In these treatments, replicate [O2] time series predictably crossed a tipping point at ∼45 h as [O2] was decoupled from diurnal cycles of photosynthesis and respiration. Increasing organic-matter loading led to predictable changes in [O2] dynamics, with high loading consistently driving the system past a well-defined tipping point. The Sarracenia microecosystem functions as a tractable experimental system in which to explore the forecasting and management of tipping points and alternative regimes. PMID:23613583

  13. Aquatic risk assessment of herbicides in freshwater ecosystems of South Florida.

    PubMed

    Schuler, Lance J; Rand, Gary M

    2008-05-01

    Widespread, high-volume use and subsequent off-site transport of herbicides, specifically photosystem II inhibitors (PSII), on agricultural and noncultivated lands in south Florida has resulted in frequent detections in freshwater systems. In light of the current restoration efforts as part of the Comprehensive Environmental Restoration Plan (CERP), increased water flows containing detectable herbicide levels into the Everglades ecosystem and adjacent areas may have adverse consequences to the unique plant communities present in the region. The potential impact of individual herbicides to aquatic plant and algae species was examined using a probabilistic risk assessment approach. Risk was characterized for nine PSII herbicides (four triazines: ametryn, atrazine, simazine, and prometryn; two triazinones: hexazinone and metribuzin; two substituted ureas: diuron and linuron; and a uracil: bromacil) and a pyridazinone herbicide (norflurazon) by comparing the overlap of the 90th percentile surface water concentration (exposure benchmark) from the exposure distributions to the 10th percentile of effects (effects benchmark) determined from species sensitivity distributions of acute laboratory toxicity data. Overall, the risk of the individual herbicides was generally low. A Multiple Substance Potentially Affected Fraction (msPAF) risk approach also was utilized to examine the joint toxicity of the herbicide mixtures based on a concentration addition model. The risk associated with the herbicide mixture (mainly bromacil, diuron, and norflurazon) was determined to be high for Lee (site S79 on the Caloosahatchee River), Martin (site S80 on St. Lucie Canal), and St. Lucie (site S99 on C25 emptying into Indian River Lagoon) counties in south Florida. This study highlights the need to consider joint action of chemical mixtures as part of an ecological risk assessment. PMID:18094912

  14. Quantification and Composition Analysis of Small Mobile Colloids from Different Aquatic Ecosystem

    NASA Astrophysics Data System (ADS)

    Yan, Jing; Lazouskaya, Volha; Jin, Yan

    2014-05-01

    Natural colloids, often defined as entities with sizes < 1.0 μm, have attracted much attention due to their small size and large surface area, leading to their high reactivity with and ability to facilitate the transport of contaminants in the subsurface environment. However, the role of mobile colloids in carbon and phosphorus cycling is largely unknown, especially on the role of smaller colloids (< 0.45 μm), which are operationally considered as "dissolved" species in most studies. Our special focus is on smaller colloids in different size fractions. Colloids are sampled from different aquatic ecosystems, such as freshwater, wetland and estuary area, and include soil solution, stream water and groundwater samples. Colloids of various size fractions are separated using centrifugation or membrane filters and quantified gravimetrically and characterized using SEM or TEM with XEDs to analyze the morphology and compositions of colloidal organo-mineral associations. Preliminary results based on stream water at base flow, during storm event and wetland soil water showed that, in general, small natural colloids (0.1 - 0.45 µm or 0.2 - 0.4 µm) contribute significantly to the whole colloidal pools (< 0.7 or 1.2 µm), and even dominant in some samples and play an important role in carbon and phosphorus mobilization. However, colloid concentrations varied with many factors such as stream order, precipitation time and intensity, and redox conditions. In this presentation, we will present results on quantification and characterization of mobile colloids from field samples and factors that control their mobilization and stabilization, and their role in carbon and phosphorus fate and transport.

  15. Importance of particle-associated bacterial heterotrophy in a coastal Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Garneau, Marie-Ève; Vincent, Warwick F.; Terrado, Ramon; Lovejoy, Connie

    2009-01-01

    estuarine stations with highest POM content. Particle-associated bacteria are an important functional component of this Arctic ecosystem. Under a warmer climate, they are likely to play an increasing role in coastal biogeochemistry and carbon fluxes as a result of permafrost melting and increased particle transport from the tundra to coastal waters.

  16. Net ecosystem exchange of CO2 with rapidly changing high Arctic landscapes.

    PubMed

    Emmerton, Craig A; St Louis, Vincent L; Humphreys, Elyn R; Gamon, John A; Barker, Joel D; Pastorello, Gilberto Z

    2016-03-01

    High Arctic landscapes are expansive and changing rapidly. However, our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near-zero sink of atmospheric CO2 (NEE: -0.3 ± 13.5 g C m(-2) ). A nearby meadow wetland accumulated over 300 times more carbon (NEE: -79.3 ± 20.0 g C m(-2) ) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southerly latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on-site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote sensing; however, high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases enough to offset poor soil moisture retention, climate-related changes to productivity on polar semideserts may be restricted. PMID:26279166

  17. Possible Cretaceous Arctic terrestrial ecosystem dynamics based on a rich dinosaur record from Alaska

    NASA Astrophysics Data System (ADS)

    Fiorillo, A. R.; McCarthy, P. J.; Flaig, P. P.

    2010-12-01

    The widespread occurrence of large-bodied herbivores, specifically hadrosaurian and ceratopsian dinosaurs, in the Cretaceous of Alaska presents a proxy for understanding polar terrestrial ecosystem biological productivity in a warm Arctic world. These dinosaurs lived in Alaska at time when this region was at or near current latitudes. Thus these dinosaurs present a paradox. The warmer Cretaceous high-latitude climate, likely related to higher levels of CO2, may have increased plant productivity but the polar light regime fluctuations must have limited the available food during the winter months. The most detailed sedimentological data available regarding the paleoenvironments supporting these dinosaurs are from the Prince Creek Formation of northern Alaska and to a lesser extent the Cantwell Formation of the Alaska Range. The sediments of the Late Cretaceous Prince Creek Formation represent a continental succession deposited on a high-latitude, low-gradient, alluvial/coastal plain. The Prince Creek Formation records numerous paleosols that are consistent with seasonality and successional vegetative cover. Drab colors in fine-grained sediments, abundant carbonaceous plant material, and common siderite nodules and jarosite suggest widespread reducing conditions on poorly-drained floodplains influenced in more distal areas by marine waters. In addition, these rocks contain high levels of organic carbon and charcoal. Carbonaceous root-traces found ubiquitously within all distributary channels and most floodplain facies, along with common Fe-oxide mottles, indicate that the alluvial system likely experienced flashy, seasonal, or ephemeral flow and a fluctuating water table. The flashy nature of the alluvial system may have been driven by recurring episodes of vigorous seasonal snowmelt in the Brooks Range orogenic belt as a consequence of the high paleolatitude of northern Alaska in the Late Cretaceous. The presence of dinosaurian megaherbivores suggests that water was

  18. Late Pleistocene paleoecology of arctic ground squirrel ( Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA

    NASA Astrophysics Data System (ADS)

    Gaglioti, Benjamin V.; Barnes, Brian M.; Zazula, Grant D.; Beaudoin, Alwynne B.; Wooller, Matthew J.

    2011-11-01

    Botanical analyses of fossil and modern arctic ground squirrel ( Urocitellus parryii) caches and nests have been used to reconstruct the past vegetation from some parts of Beringia, but such archives are understudied in Alaska. Five modern and four fossil samples from arctic ground squirrel caches and nests provide information on late Pleistocene vegetation in Eastern Beringia. Modern arctic ground squirrel caches from Alaska's arctic tundra were dominated by willow and grass leaves and grass seeds and bearberries, which were widespread in the local vegetation as confirmed by vegetation surveys. Late Pleistocene caches from Interior Alaska were primarily composed of steppe and dry tundra graminoid and herb seeds. Graminoid cuticle analysis of fossil leaves identified Calamagrostis canadensis, Koeleria sp. and Carex albonigra as being common in the fossil samples. Stable carbon isotopes analysis of these graminoid specimens indicated that plants using the C 3 photosynthetic pathways were present and functioning with medium to high water-use efficiency. Fossil plant taxa and environments from ground squirrel caches in Alaska are similar to other macrofossil assemblages from the Yukon Territory, which supports the existence of a widespread mammoth steppe ecosystem type in Eastern Beringia that persisted throughout much of the late Pleistocene.

  19. Assessing the Utility of Alternate Digital Image Color Space for Deriving Phenological Dynamics in a High-Arctic Tundra Ecosystem

    NASA Astrophysics Data System (ADS)

    Vargas, S. A., Jr.; Oberbauer, S. F.; Ramirez, G.; Ramirez, G. A.; Tweedie, C. E.; Hollister, R. D.; Escarzaga, S. M.; Ochoa, E.

    2015-12-01

    The need to improve the spatial and temporal scaling and extrapolation of plot level ecosystem properties and processes to the landscape level remains a persistent research challenge in the Arctic. Plant and landscape phenology is sensitive to a number of spatiotemporally variable environmental factors such as soil moisture, temperature, and radiation. Seasonal and inter-annual differences in phenology can affect surface energy balance and land-atmosphere carbon flux. Considering the relative importance of the Arctic to global carbon balance, improved scaling and extrapolation of phenological dynamics from the plot level to the landscape level is important for advancing our understanding of the impact of climate and other environmental change in arctic terrestrial ecosystems. Seasonal and interannual landscape phenology was observed over the Mobile Instrumented Sensor Platform (MISP) grid (2 x 50 meters) located in Barrow and Atqasuk, Alaska using imagery acquired from kite aerial photography (KAP), a hyperspectral ground-based spectrometer, and a phenocam. These data were analyzed in RGB and non-traditional HSV and l*a*b*color spaces to determine site, plant community seasonal, and inter annual phenological dynamics. Results were also compared to high spatial resolution satellite imagery to determine optimal indices for scaling vegetation dynamics from plot to landscape level. These results show that greenness indices similar to those acquired from hyperspectral remote sensing platforms can be derived using low-cost and low-tech techniques that could be deployed at multiple sites at low cost.

  20. Estimations of moisture content in the active layer in an Arctic ecosystem by using ground-penetrating radar profiling

    NASA Astrophysics Data System (ADS)

    Gacitúa, Guisella; Tamstorf, Mikkel Peter; Kristiansen, Søren Munch; Uribe, José Andrés

    2012-04-01

    We applied high-frequency GPR at a study site in the high arctic ecosystem of Northeast Greenland to evaluate its usefulness in assessing depth of, and water content in, the active layer at Zackenberg Valley (74°N; 20°W) to evaluate its usefulness in the high arctic ecosystems. The study site includes different vegetation types, and it well represents of the entire valley, for which we aimed to determine the conditions and characteristics that influence the GPR performance in the active layer. The spatial distribution of moisture content along the transect studied was estimated using GPR data (400 MHz antenna), depth to permafrost, soil samples and vegetation observations. Vertical distribution of the water content in the unfrozen soil bulk was predicted for several points on the transect by combining data that influence the behavior of the radar waves with that of capacitive moisture probes. The statistical models resulted to be highly significant, thus assuming common conditions of the soil to the classified vegetation, we can obtain from the GPR data, truthful estimations of water content, and, moreover, we can predict the distribution to the bottom of the active layer. Hence, we conclude that GPR is a viable option for improving active layer spatial quantification of water contents that can be used to assess changes in the active layer in arctic regions.

  1. Mycobacterium ulcerans dynamics in aquatic ecosystems are driven by a complex interplay of abiotic and biotic factors

    PubMed Central

    Garchitorena, Andrés; Guégan, Jean-François; Léger, Lucas; Eyangoh, Sara; Marsollier, Laurent; Roche, Benjamin

    2015-01-01

    Host–parasite interactions are often embedded within complex host communities and can be influenced by a variety of environmental factors, such as seasonal variations in climate or abiotic conditions in water and soil, which confounds our understanding of the main drivers of many multi-host pathogens. Here, we take advantage of a combination of large environmental data sets on Mycobacterium ulcerans (MU), an environmentally persistent microorganism associated to freshwater ecosystems and present in a large variety of aquatic hosts, to characterize abiotic and biotic factors driving the dynamics of this pathogen in two regions of Cameroon. We find that MU dynamics are largely driven by seasonal climatic factors and certain physico-chemical conditions in stagnant and slow-flowing ecosystems, with an important role of pH as limiting factor. Furthermore, water conditions can modify the effect of abundance and diversity of aquatic organisms on MU dynamics, which suggests a different contribution of two MU transmission routes for aquatic hosts (trophic vs environmental transmission) depending on local abiotic factors. DOI: http://dx.doi.org/10.7554/eLife.07616.001 PMID:26216042

  2. Think before you flush! A sustainable aquatic eco-system's relation to human health.

    PubMed

    McKeown, Elaine; Pawloski, Judith

    2013-01-01

    What we do every day at work and in our home lives can make a difference in the quality of our environment. Consider, for example, the flushing of pharmaceuticals into the sewer system can lead to water pollution resulting in a threat to aquatic and human life. In contrast, keeping aquatic life healthy may contribute to human health. Some aquatic-based medications are currently on the market. Others are in various stages of development. In this article the authors argue that, for the benefit of both human and marine life, it is time to implement safer disposal methods for unwanted medications. The authors begin by sharing nursing's guiding principles for environmental health; after which they review research related to pharmaceutical pollution of water resources; describe health care treatments derived from marine life; and discuss suggestions for promoting aquatic health. They conclude that by taking care to preserve aquatic life, we contribute to the quality of our own human lives. PMID:23452193

  3. Canopy Spectral Imaging (NDVI) As A Proxy For Shrub Biomass And Ecosystem Carbon Fluxes Across Arctic Tundra Habitats

    NASA Astrophysics Data System (ADS)

    Flower, C. E.; Welker, J. M.; Gonzalez-Meler, M. A.

    2015-12-01

    There is widespread consensus that climate change is contributing to rapid vegetation shifts in the ecologically sensitive Arctic tundra. These tussock grass dominated systems are shifting to tussock/woody shrub communities leading to likely alterations in carbon (C) sequestration and ecosystem productivity, which in turn can manifest in "greening" and changes in normalized difference vegetation index values (NDVI). While the expansion of woody vegetation is well established, our understanding of the ecosystem dynamics associated with this new habitat remain largely unknown. To untangle how the Arctic tundra may be impacted by these vegetation shifts we paired vegetation measurements (i.e. shrub biomass, leaf area, and shrub canopy area) and ecosystem C fluxes (e.g. net ecosystem exchange, NEE, and ecosystem respiration) with ground-level measurements of NDVI. Measurements were conducted at the Toolik Field Station in dry heath and moist acidic tundra habitats which are two primary habitat types on the North Slope of Alaska. We found strong positive relationships between shrub leaf area and biomass as well as shrub canopy area and biomass, relationships that were corroborated with NDVI measurements. This lends support for the use of NDVI as a proxy measurement of leaf area and shrub biomass. Additionally, NDVI was negatively correlated with ecosystem respiration across habitats, with respiratory fluxes consistently higher in the moist acidic relative to the dry heath tundra. Finally, we observed a significant positive nonlinear relationship between NEE and NDVI (R2~0.8; P<0.01). Shrub removal revealed that NEE was strongly controlled by woody shrubs. The positive relationship between NDVI and NEE highlights the potential shifts in the C balance of the Arctic tundra associated with woody encroachment. This increased plant productivity may offset greenhouse gas losses from permafrost degradation contributing some resilience to this system otherwise considered a

  4. ARCTIC BIODIVERSITY: FROM DISCOVERY TO FAUNAL BASELINES-REVEALING THE HISTORY OF A DYNAMIC ECOSYSTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of parasite biodiversity contributes to new and exciting approaches to understand the structure, history and future of the Arctic fauna. As a discovery- based process the Beringian Coevolution Project and activities under the umbrella of the Research Group for Arctic Parasitology serve as...

  5. Novel wildlife in the Arctic: the influence of changing riparian ecosystems and shrub habitat expansion on snowshoe hares.

    PubMed

    Tape, Ken D; Christie, Katie; Carroll, Geoff; O'Donnell, Jonathan A

    2016-01-01

    Warming during the 20th century has changed the arctic landscape, including aspects of the hydrology, vegetation, permafrost, and glaciers, but effects on wildlife have been difficult to detect. The primary aim of this study is to examine the physical and biological processes contributing to the expanded riparian habitat and range of snowshoe hares (Lepus americanus) in northern Alaska. We explore linkages between components of the riparian ecosystem in Arctic Alaska since the 1960s, including seasonality of stream flow, air temperature, floodplain shrub habitat, and snowshoe hare distributions. Our analyses show that the peak discharge during spring snowmelt has occurred on average 3.4 days per decade earlier over the last 30 years and has contributed to a longer growing season in floodplain ecosystems. We use empirical correlations between cumulative summer warmth and riparian shrub height to reconstruct annual changes in shrub height from the 1960s to the present. The effects of longer and warmer growing seasons are estimated to have stimulated a 78% increase in the height of riparian shrubs. Earlier spring discharge and the estimated increase in riparian shrub height are consistent with observed riparian shrub expansion in the region. Our browsing measurements show that snowshoe hares require a mean riparian shrub height of at least 1.24-1.36 m, a threshold which our hindcasting indicates was met between 1964 and 1989. This generally coincides with observational evidence we present suggesting that snowshoe hares became established in 1977 or 1978. Warming and expanded shrub habitat is the most plausible reason for recent snowshoe hare establishment in Arctic Alaska. The establishment of snowshoe hares and other shrub herbivores in the Arctic in response to increasing shrub habitat is a contrasting terrestrial counterpart to the decline in marine mammals reliant on decreasing sea ice. PMID:26527375

  6. The feasibility of automated online flow cytometry for in-situ monitoring of microbial dynamics in aquatic ecosystems

    PubMed Central

    Besmer, Michael D.; Weissbrodt, David G.; Kratochvil, Bradley E.; Sigrist, Jürg A.; Weyland, Mathias S.; Hammes, Frederik

    2014-01-01

    Fluorescent staining coupled with flow cytometry (FCM) is often used for the monitoring, quantification and characterization of bacteria in engineered and environmental aquatic ecosystems including seawater, freshwater, drinking water, wastewater, and industrial bioreactors. However, infrequent grab sampling hampers accurate characterization and subsequent understanding of microbial dynamics in all of these ecosystems. A logic technological progression is high throughput and full automation of the sampling, staining, measurement, and data analysis steps. Here we assess the feasibility and applicability of automated FCM by means of actual data sets produced with prototype instrumentation. As proof-of-concept we demonstrate examples of microbial dynamics in (i) flowing tap water from a municipal drinking water supply network and (ii) river water from a small creek subject to two rainfall events. In both cases, automated measurements were done at 15-min intervals during 12–14 consecutive days, yielding more than 1000 individual data points for each ecosystem. The extensive data sets derived from the automated measurements allowed for the establishment of baseline data for each ecosystem, as well as for the recognition of daily variations and specific events that would most likely be missed (or miss-characterized) by infrequent sampling. In addition, the online FCM data from the river water was combined and correlated with online measurements of abiotic parameters, showing considerable potential for a better understanding of cause-and-effect relationships in aquatic ecosystems. Although several challenges remain, the successful operation of an automated online FCM system and the basic interpretation of the resulting data sets represent a breakthrough toward the eventual establishment of fully automated online microbiological monitoring technologies. PMID:24917858

  7. The feasibility of automated online flow cytometry for in-situ monitoring of microbial dynamics in aquatic ecosystems.

    PubMed

    Besmer, Michael D; Weissbrodt, David G; Kratochvil, Bradley E; Sigrist, Jürg A; Weyland, Mathias S; Hammes, Frederik

    2014-01-01

    Fluorescent staining coupled with flow cytometry (FCM) is often used for the monitoring, quantification and characterization of bacteria in engineered and environmental aquatic ecosystems including seawater, freshwater, drinking water, wastewater, and industrial bioreactors. However, infrequent grab sampling hampers accurate characterization and subsequent understanding of microbial dynamics in all of these ecosystems. A logic technological progression is high throughput and full automation of the sampling, staining, measurement, and data analysis steps. Here we assess the feasibility and applicability of automated FCM by means of actual data sets produced with prototype instrumentation. As proof-of-concept we demonstrate examples of microbial dynamics in (i) flowing tap water from a municipal drinking water supply network and (ii) river water from a small creek subject to two rainfall events. In both cases, automated measurements were done at 15-min intervals during 12-14 consecutive days, yielding more than 1000 individual data points for each ecosystem. The extensive data sets derived from the automated measurements allowed for the establishment of baseline data for each ecosystem, as well as for the recognition of daily variations and specific events that would most likely be missed (or miss-characterized) by infrequent sampling. In addition, the online FCM data from the river water was combined and correlated with online measurements of abiotic parameters, showing considerable potential for a better understanding of cause-and-effect relationships in aquatic ecosystems. Although several challenges remain, the successful operation of an automated online FCM system and the basic interpretation of the resulting data sets represent a breakthrough toward the eventual establishment of fully automated online microbiological monitoring technologies. PMID:24917858

  8. Interactions of carbon nanotubes with aqueous/aquatic media containing organic/inorganic contaminants and selected organisms of aquatic ecosystems--A review.

    PubMed

    Boncel, Sławomir; Kyzioł-Komosińska, Joanna; Krzyżewska, Iwona; Czupioł, Justyna

    2015-10-01

    Due to their unique molecular architecture translating into numerous every-day applications, carbon nanotubes (CNTs) will be ultimately an increasingly significant environmental contaminant. This work reviews qualitative/quantitative analyses of interactions of various types of CNTs and their chemically modified analogues with aqueous/aquatic media containing organic and inorganic contaminants and selected organisms of aquatic ecosystems. A special emphasis was placed on physicochemical interactions between CNTs as adsorbents of heavy metal cations and aromatic compounds (dyes) with its environmental consequences. The studies revealed CNTs as more powerful adsorbents of aromatic compounds (an order of magnitude higher adsorption capacity) than metal cations. Depending on the presence of natural organic matter (NOM) and/or co-contaminants, CNTs may act as Trojan horse while passing through biological membranes (in the absence of NOM coordinating metal ions). Nanotubes, depending on flow conditions and their morphology/surface chemistry, may travel with natural waters or sediment with immobilized PAHs or metals and/or increase cyto- and ecotoxicity of PAHs/metal ions by their release via competitive complexation, or cause synergic ecotoxicity while adsorbing nutrients. Additionally, toxicity of CNTs against exemplary aquatic microorganisms was reviewed. It was found for Daphnia magna that longer exposures to CNTs led to higher ecotoxicity with a prolonged CNTs excretion. SWCNTs were more toxic than MWCNTs, while hydrophilization of CNTs via oxidation or anchoring thereto polar/positively charged polymer chains enhanced stability of nanotubes dispersion in aqueous media. On the other hand, bioavailability of functionalized CNTs was improved leading to more complex both mechanisms of uptake and cytotoxic effects. PMID:26022284

  9. Aboveground and belowground responses to nutrient additions and herbivore exclusion in Arctic tundra ecosystems in northern Alaska

    NASA Astrophysics Data System (ADS)

    Moore, J. C.; Gough, L.; Simpson, R.; Johnson, D. R.

    2011-12-01

    The Arctic has experienced significant increased regional warming over the past 30 years. Warming generally increases tundra soil nutrient availability by creating a more favorable environment for plant growth, decomposition and nutrient mineralization. Aboveground there has been a "greening" of the Arctic with increased net primary productivity (NPP), and an increase in woody vegetation. Concurrent with the changes aboveground has been an increase in root growth at lower depths and a loss of soil organic C (40 -100 g C m-2 yr-1). Given that arctic soils contain 14% of the global soil C pool, understanding the mechanisms behind shifts of this magnitude that are changing arctic soils from a net sink to a net source of atmospheric C is critical. We took an integrated multi-trophic level approach to examine how altering soil nutrients and mammalian herbivore activity affects vegetation, soil fauna, and microbial communities as well as soil physical characteristics in moist acidic (MAT) and dry heath (DH) tundra. Our work was conducted at the Arctic LTER site in northern Alaska. We sampled the nutrient (controls and annual N+P additions) and herbivore (controls and exclosures) manipulations established in 1996 after 10 years of treatment. Models that incorporated the biomass estimates from the field were used to characterize the trophic structure of the belowground food web and to estimate carbon flux among soil organisms and C-mineralization rates. Both MAT and DH exhibited significant increases in NPP and root growth and changes in vegetation structure with transitions from a mixed community to deciduous shrubs in MAT and from lichens to grasses and shrubs in DH, with nutrient additions and herbivore exclosures. Belowground responses to the treatments were dependent on ecosystem type, but exposed alterations in trophic structure that included changes in microbial biomass, the establishment of microbivorous enchytreaids, increases in root-feeding nematodes, and

  10. Formation, transformation and transport of black carbon (charcoal) in terrestrial and aquatic ecosystems.

    PubMed

    Forbes, M S; Raison, R J; Skjemstad, J O

    2006-10-15

    Black carbon (BC) is ubiquitous in terrestrial environments and its unique physical and chemical properties suggest that it may play an important role in the global carbon budget (GCB). A critical issue is whether the global production of BC results in significant amounts of carbon (C) being removed from the short-term bio-atmospheric carbon cycle and transferred to the long-term geological carbon cycle. Several dozen field and laboratory based studies of BC formation during the burning of biomass have been documented. Findings are difficult to interpret because they have been expressed in an inconsistent manner, and because different physical and chemical methods have been used to derive them. High error terms documented in many of these studies also highlight the problems associated with the quantification of the amount of biomass C consumed in fire, the amount of residue produced and the constituents of that residue. To be able to estimate the potential for BC as a carbon sink, issues regarding its definition, the methods used in its identification and measurement, and the way it is expressed in relation to other components of the carbon cycle need to be addressed. This paper presents BC data in a standard way; BC production as a percentage of the amount of C consumed by fire (BC/CC), which can be readily integrated into a larger carbon budget. Results from previous studies and new data from Australian ecosystems were recalculated in this way. As part of this process, several BC estimates derived solely from physical methods were discarded, based on their inability to accurately identify and quantify the BC component of the post-fire residue. Instead, more focus was placed on BC estimates obtained by chemical methods. This recalculated data lowered the estimate for BC formation in forest fires from 4% to 5% to <3% BC/CC. For savannah and grassland fires a value of <3% is consistent with reported data, but considerable variation among estimates remains. An

  11. A National Pilot Study of Mercury Contamination of Aquatic Ecosystems Along Multiple Gradients: Bioaccumulation in Fish

    USGS Publications Warehouse

    Brumbaugh, William G.; Krabbenhoft, David P.; Helsel, Dennis R.; Wiener, James G.; Echols, Kathy R.

    2001-01-01

    Water, sediment, and fish were sampled in the summer and fall of 1998 at 106 sites from 20 U.S. watershed basins to examine relations of mercury (Hg) and methylmercury (MeHg) in aquatic ecosystems. Bioaccumulation of Hg in fish from these basins was evaluated in relation to species, Hg and MeHg in surficial sediment and water, and watershed characteristics. Bioaccumulation was strongly (positively) correlated with MeHg in water (r = 0.63, p < 0.001) but only moderately with the MeHg in sediment (r = 0.33, p < 0.001) or total Hg in water (r = 0.28, p < 0.01). Of the other significantly measured parameters, pH, DOC, sulfate, sediment LOI, and the percent wetlands of each basin were also significantly correlated with Hg bioaccumulation in fish. The best model for predicting Hg bioaccumulation included Me Hg in water, PH of the water, % wetlands in the basin, and the AVS content of the sediment. These four variables accounted for 45% of the variability of the fish fillet Hg concentration normalized (divided) by total length; however, the majority was described by MeHg in water. A MeHg water concentration 0.12 ng/L was on average, associated with a fish fillet Hg concentration of 0.3 mg/kg wet weight for an age-3 fish when all species were considered. For age-3 largemouth bass, a MeHg water concentration of 0.058 ng/L was associated with the 0.3 mg/kg fillet concentration. Based on rankings for Hg in sediment, water, and fish, sampling sites from the following five study basins had the greatest Hg contamination: Nevada Basin and Range, South Florida Basin, Sacramento River Basin (California), Santee River Basin and Caostal Drainages (South Carolina), and the Long Island and New Jersey Coastal DRainags. A sampling and analysis strategy based on this pilot study is planned for all USGS/NAWQA study units over the next decade.

  12. Effects of experimental floods on riparian and aquatic ecosystems: Bill Williams River, Arizona

    NASA Astrophysics Data System (ADS)

    Shafroth, P. B.; Andersen, D. C.; Wilcox, A. C.; Kui, L.; Stella, J. C.

    2013-12-01

    Development of flow prescriptions for environmental purposes along rivers is relatively common, but implementation of these 'environmental flows' occurs infrequently. Implementation is critical for testing hypotheses relating flow regime to biotic response, which ultimately can inform adaptive flow management. We describe the development of flow prescriptions and evaluate responses of riparian vegetation, beaver dams, and associated aquatic habitat to experimental floods and intervening base flows associated with an environmental flow program on the Bill Williams River (BWR), in semiarid Arizona. First, we assessed effects of flow releases between 1993 and 2009 designed to favor the establishment and maintenance of native riparian trees (Populus and Salix) and disfavor an invasive, nonnative shrub (Tamarix spp.) downstream of Alamo Dam on the BWR. Our data are multi-scaled and include a several-decade assessment of changes to major vegetation types based on a time series of aerial photography, an assessment of species composition and abundance sampled in permanent vegetation quadrats, and targeted seedling surveys following experimental floods. Between 1993 and 2009, we observed significant increases in Populus and Salix forests and essentially no change in Tamarix. Experimental floods in 2006 and 2007 resulted in higher mortality of Tamarix seedlings than Salix. These results illustrate the potential for managing streamflow to influence riparian vegetation dynamics, including management of nonnative species. Second, we examined the role of beaver as ecosystem engineers in the BWR and linkages to flow releases between 2004 and 2013. Beaver convert lotic stream habitat to lentic through dam construction and maintenance during low flow periods, and the process is reversed when a flood or other event causes dam failure. We estimated the extent of lotic and beaver-created lentic (beaver pond) habitat along the BWR and related the likelihood of damage or destruction of

  13. The Life Cycle of Mercury Within the Clear Lake Aquatic Ecosystem: From Ore to Organism

    NASA Astrophysics Data System (ADS)

    Suchanek, T. H.; Suchanek, T. H.; Nelson, D. C.; Nelson, D. C.; Zierenberg, R. A.; King, P.; King, P.; McElroy, K.; McElroy, K.

    2001-12-01

    Clear Lake (Lake County) is located in the geologically active Clear Lake volcanics mercury (Hg) bearing Franciscan formation within the Coast Range of California, which includes over 300 abandoned Hg mines and prospects. Intermittent mining at the Sulphur Bank Mercury Mine (from 1872-1957), now a USEPA SuperFund site, has resulted in approximately 100 metric tonnes of Hg being deposited into the aquatic ecosystem of Clear Lake, with sediment concentrations of total-Hg as high as 650 mg/kg (parts per million = ppm) near the mine, making Clear Lake one of the most Hg contaminated lakes in the world. As a result, largemouth bass and other top predatory fish species often exceed both the Federal USFDA recommended maximum recommended concentrations of 1.0 ppm and the State of California level of 0.5 ppm. Acid rock drainage leaches Hg and high concentrations of sulfate from the mine site through wasterock and subsurface conduits through subsediment advection and eventually upward diffusion into lake sediments and water. When mineral-laden pH 3 fluids from the mine mix with Clear Lake water (pH 8), an alumino-silicate precipitate (floc) is produced that promotes the localized production of toxic methyl Hg. Floc "hot spots" in sediments near the mine exhibit low pH, high sulfate, anoxia and high organic loading which create conditions that promote Hg methylation by microbial activity, especially in late summer and fall. Wind-driven currents transport methyl-Hg laden floc particles throughout Clear Lake, where they are consumed by plankton and benthic invertebrates and bioaccumulated throughout the food web. While Clear Lake biota have elevated concentrations of methyl-Hg, they are not as elevated as might be expected based on the total Hg loading into the lake. A science-based management approach, utilizing over 10 years of data collected on Hg cycling within the physical and biological compartments of Clear Lake, is necessary to affect a sensible remediation plan.

  14. Recent aquatic ecosystem response to environmental events revealed from 210Pb sediment profiles.

    PubMed

    Mulsow, S; Piovano, E; Cordoba, F

    2009-01-01

    The (210)Pb dating method was first introduced by Goldberg (1963), and since then has been applied to study sediment from lakes, estuaries and coastal marine environments. Hundreds of studies around the world have used (210)Pb as a geochronological tool in aquatic ecosystems. However little attention has been paid to the potential of this naturally occurring isotope as an environmental tracer of ecological events. Here we report three instances in which (210)Pb profiles measured on undisturbed sediment cores from lakes, rivers and fjords show us the potential of (210)Pb profile as a tracer of natural and anthropogenic processes. The methodology used here is a suite of techniques combining biogeochemistry (micro-electrodes), paleomagnetism (susceptibility), sediment characteristics (LOI) and visualization (SPI and X-ray) applied to the interpretation of (210)Pb profiles. We measured (210)Pb profiles on sediments from a river, Cruces River (Chile), which recorded a clear shift in the water chemistry caused by a pulp mill effluent to the river. Here metal mobilization and remobilization of the tracer may be the cause of the observed profile. We also measured (210)Pb profiles in sediment from two fjords of Southern Chile (Pillan and Reñihue), the sudden deposition change of fresh (210)Pb with depth observed could very well be the result of bioturbation but it occurred in a seafloor area deprived of bioturbators. In this case, (210)Pb recorded the onset of aquaculture activities (fish farming) that took place two decades ago. Finally, (210)Pb profiles measured in two lakes in the "pampa Argentina": Epecuen and Venado showed a particular shape with depth. These profiles apparently registered a sudden depositional event with recent (210)Pb material, probably related to strong shifts in precipitation and drought cycles in that part of the world. These three examples show that (210)Pb profiles provide valuable information not only on geochronology, but also related to

  15. Characterizing subsurface controls on the Arctic ecosystem carbon cycling across scales using geophysical, in-situ and remote sensing datasets

    NASA Astrophysics Data System (ADS)

    Wainwright, H. M.; Hubbard, S. S.; Dafflon, B.; Ulrich, C.; Peterson, J. E.; Wu, Y.; Hahn, M. S.; Torn, M. S.; Gangodagamage, C.; Rowland, J. C.; Wilson, C. J.; Liljedahl, A.; Gusmeroli, A.; Wullschleger, S. D.

    2013-12-01

    Recent studies suggest that warming climate has significant impacts on the Arctic ecosystems, which could in turn create feedbacks to the climate system. Predicting Arctic ecosystem evolution and feedbacks requires a mechanistic understanding of complex subsurface processes (e.g., permafrost degradation and carbon decomposition) and characterization of key controls on those processes - such as soil moisture, active layer thickness and aqueous geochemistry - from native scales (where the processes occur) to landscape scales considered in climate models. Among others, developing such a predictive understanding requires two advances that we consider in this study: (1) approaches to characterize heterogeneous geocryological and hydrogeochemical properties in high resolution, and their uncertainties, inter-correlations, and correlations to land surface variables; (2) identification of possible zonation that can distinguish between suites of subsurface properties. Our study is carried out at the Department of Energy, Office of Science, Next Generation Ecosystem Experiment (NGEE-Arctic) Site in Barrow, Alaska. Given the importance of quantifying heterogeneous subsurface properties in both high resolution and over large spatial scales, we take advantage of geophysical datasets. We first develop and implement a multiscale Bayesian method to estimate subsurface properties using disparate datasets. We consider in-situ, surface geophysical and remote-sensing datasets along two 500m transects that traverse various ice-wedge polygon features. The method is based on site-specific correlations between geophysical datasets and in-situ measured subsurface properties. The Markov-chain Monte-Carlo sampling is used to compute the posterior distributions. For example, thaw depth and soil moisture are estimated by integrating ground-penetrating radar (GPR), electrical resistivity tomography and in-situ point data. Snow depth coverage is estimated by integrating GPR and point data. The

  16. Site-specific water quality criteria for aquatic ecosystems: A case study of pentachlorophenol for Tai Lake, China.

    PubMed

    Chen, Yi; Yu, Shuangying; Tang, Song; Li, Yabing; Liu, Hongling; Zhang, Xiaohui; Su, Guanyong; Li, Bing; Yu, Hongxia; Giesy, John P

    2016-01-15

    Given the widely varying types of aquatic ecosystems and bioavailability of chemicals, it is important to develop site-specific water quality criteria (WQC) to ensure criteria are neither over- nor under-protective. In the study, using pentachlorophenol (PCP) as an example, several approaches to derive site-specific WQC were investigated, including the conventional species sensitivity distribution (SSD), weighted SSD based on the proportion of each trophic level, and water effect ratio (WER) method. When corrected to a pH of 7.8, the conventional SSD approach resulted in criteria maximum concentration (CMC) and criteria continuous concentration (CCC) of 18.11 and 1.74 μg/L, respectively. If SSD was weighted according to the current species composition in Tai Lake, the CMC and CCC were 32.81 and 4.48 μg/L, respectively. However, available data suggest that many sensitive species inhabiting Tai Lake during 1980s were disappeared. Considering the species composition of the healthier ecosystem in 1980s, the CMC and CCC were 10.99 and 0.38 μg/L, respectively, which provide more protective water quality standards. Water effect ratio (WER) was further used to correct for co-occurrence of other toxicants and factors affecting bioavailability of PCP. A final WER of 4.72 was applied to adjust the criteria derived by using the weighted SSD for the 1980s aquatic community, and the final CMC and CCC obtained were 51.87 and 1.79 μg/L, respectively, at a pH of 7.8. Water quality criteria derived using the 1980s species composition and adjusted with WER were deemed the most appropriate WQC for water management and aquatic life protection. Merits of the various approaches for developing WQC for protection of aquatic species were discussed. PMID:26398452

  17. Aquatic ecosystem responses to Holocene climate change and biome development in boreal, central Asia

    NASA Astrophysics Data System (ADS)

    Mackay, Anson W.; Bezrukova, Elena V.; Leng, Melanie J.; Meaney, Miriam; Nunes, Ana; Piotrowska, Natalia; Self, Angela; Shchetnikov, Alexander; Shilland, Ewan; Tarasov, Pavel; Wang, Luo; White, Dustin

    2012-05-01

    were also significant, but considerably less important. The potential importance of climate and biome development (tundra, steppe, cold deciduous forest and taiga) on different trophic levels (i.e. chironomid and diatom communities) in lake ESM-1 was also assessed using RDA. Climate predictors had a more significant influence on Holocene chironomid assemblages, especially July insolation at 60 °N, estimates of regional precipitation and estimates of northern hemisphere temperature, while only the development of the taiga biome had a significant impact on these primary consumers. Diatom communities also had a small, but significant influence on Holocene chironomid populations, perhaps linked to variation in faunal feeding strategies. In contrast, climatic and biome predictors explained similar amounts of variation in the Holocene diatom assemblage (approximately 20% each), while chironomids themselves as predictors explained just under 7% of diatom variation. Lake acidity was inferred using a diatom inference model. Results suggest that after deglaciation, the lake did not undergo a process of gradual acidification, most likely due to the presence of continuous permafrost and low levels of precipitation, preventing base cations and dissolved organic carbon entering the lake (except for the period between 1.7 and 0.7 ka BP). We conclude that lakes in continental, boreal regions undergo different models of lake ontogeny than oceanic boreal regions. Unlike other regions discussed, climate is a more important driver of ecosystem change than catchment changes. We also demonstrate that the start of the period coincident with the onset of the Little Ice Age resulted in important thresholds crossed in catchment vegetation and aquatic communities.

  18. Burrowing mayflies (Hexagenia) as indicators of aquatic ecosystem health at Sleeping Bear Dunes National Lakeshore, Michigan

    USGS Publications Warehouse

    Edsall, T.A.; Phillips, W.E.

    2004-01-01

    With concern running high for the ecological effects of nutrient introductions in waters near the park, researchers document baseline conditions of aquatic park resources, applying a method that can be fine-tuned for future trend monitoring.

  19. A METHODOLOGY FOR INFERRING THE CAUSES OF OBSERVED IMPAIRMENTS IN AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Biological surveys have become a common technique for determining whether aquatic communities have been injured. However, their results are not useful for identifying management options until the causes of apparent injuries have been identified. Techniques for determining causa...

  20. [Ecological risk assessment of organophosphorus pesticides in aquatic ecosystems of Pearl River Estuary].

    PubMed

    Guo, Qiang; Tian, Hui; Mao, Xiao-Xuan; Huang, Tao; Gao, Hong; Ma, Jian-Min; Wu, Jun-Nian

    2014-03-01

    The risk quotient method and a probabilistic risk assessment method were applied for assessing aquatic ecological risk of nine organophosphorus pesticides, including thimet, dichlorovos, disulfoton, dimethoate, dimethyl parathion, chlorpyrifos, ethoprophos, sumithion and malathion on eight aquatic organisms in the Pearl River Estuary. Results using the risk quotient method revealed that the risk level of opossum shrimp was the highest among eight aquatic organisms of the Pearl River Estuary. The risk of water flea and midge was in medium level, followed by the rest six aquatic organisms, including diatom, oyster, carp, catfish and eel, which were in the low risk by the examined organophosphorus pesticides. It was found that thimet made the largest contribution to total aquatic ecological risk among nine organophosphorus pesticides to every organism. The results from probabilistic risk assessment showed that the total ecological risk in high water period was higher than that in low water period determined by the HC5 under the 95% confidence level. The largest contribution of thimet to total aquatic ecological risk subject to the HC5 in 50% confidence level was regarded as the toxic reference value. The probabilistic risk of a single contaminant showed that thimet and disulfoton were harmful to exceeded 10% organisms in the estuarine. The probabilistic risk of nine pesticides mixture in high water period was also higher than that in low water period, and both risks were greater than 5% which exceeded safety threshold for 95% organisms in the Pearl River Estuary. PMID:24881393

  1. Microbial Biomass and Population Densities of Non-Sorted Circles in High Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Rivera-Figueroa, F.; González, G.; Gould, W. A.; Cantrell, S.; Pérez, J.

    2006-12-01

    Non-sorted circles are small patterned-ground features that occur in arctic soils as a result of intensive frost heave action. This tundra feature has been extensively described. However, little is known about the ecological relationships between this pattern and above- and belowground organisms. In this study, we compare the biomass and populaton densities of microbes in non-sorted circles and the vegetated surrounding soils (inter-circles) in the High Arctic. We collected soil samples during the summer of 2004 and 2005 on Banks and Prince Patrick and Ellef Ringnes Islands, Canada. Soil samples (0-10 cm) were gathered from non- sorted circles and inter-circles along a topographic sequence: dry (ridge), mesic (mid slope) and wet (valley) and along three transects in zonal (mesic) sites on each island. We estimated total microbial biomass and bacterial population densities using substrate induce respiration (SIR) and the most probable number method (MPN), respectively. We also isolated soil fungi using Rose Bengal and Saboraud Dextrose culture media. We are in the process of analyzing the catena samples using a terminal restriction fragment length polymorphism (TRFLP) technique of PCR-amplified 16S rRNA. Based on the SIR trials, the average microbial biomass at the mid slope position in the Banks site (Green Cabin) was 0.49 mg C g-1 dry soil in the non- sorted circles and 0.95 mg C g-1 dry soil in the inter-circles. At Prince Patrick Island (Mould Bay) the microbial biomass was 0.54 mg C g-1 dry soil in the non-sorted circles and 0.74 mg C g-1 dry soil in the inter-circles. In Ellef Ringnes (Isachsen) the microbial biomass was 0.09 mg C g-1 dry soil in the non- sorted circles and 0.14 mg C g-1 dry soil in the inter-circles. At the mesic site at Green Cabin, bacteria vary from 2.92 x 106 cell g-1 dry soil in the non-sorted circles to 6.74 x 106 cell g-1 dry soil in the inter-circles. At Mould Bay the range was 7.67 x 105 cells g-1 dry soil in the non-sorted circles

  2. The Barents and Chukchi Seas: Comparison of two Arctic shelf ecosystems

    NASA Astrophysics Data System (ADS)

    Hunt, George L.; Blanchard, Arny L.; Boveng, Peter; Dalpadado, Padmini; Drinkwater, Kenneth F.; Eisner, Lisa; Hopcroft, Russ R.; Kovacs, Kit M.; Norcross, Brenda L.; Renaud, Paul; Reigstad, Marit; Renner, Martin; Skjoldal, Hein Rune; Whitehouse, Andy; Woodgate, Rebecca A.

    2013-01-01

    This paper compares and contrasts the ecosystems of the Barents and Chukchi Seas. Despite their similarity in a number of features, the Barents Sea supports a vast biomass of commercially important fish, but the Chukchi does not. Here we examine a number of aspects of these two seas to ascertain how they are similar and how they differ. We then indentify processes and mechanisms that may be responsible for their similarities and differences. Both the Barents and Chukchi Seas are high latitude, seasonally ice covered, Arctic shelf-seas. Both have strongly advective regimes, and receive water from the south. Water entering the Barents comes from the deep, ice-free and "warm" Norwegian Sea, and contains not only heat, but also a rich supply of zooplankton that supports larval fish in spring. In contrast, Bering Sea water entering the Chukchi in spring and early summer is cold. In spring, this Bering Sea water is depleted of large, lipid-rich zooplankton, thus likely resulting in a relatively low availability of zooplankton for fish. Although primary production on average is similar in the two seas, fish biomass density is an order of magnitude greater in the Barents than in the Chukchi Sea. The Barents Sea supports immense fisheries, whereas the Chukchi Sea does not. The density of cetaceans in the Barents Sea is about double that in the Chukchi Sea, as is the density of nesting seabirds, whereas, the density of pinnipeds in the Chukchi is about double that in the Barents Sea. In the Chukchi Sea, export of carbon to the benthos and benthic biomass may be greater. We hypothesize that the difference in fish abundance in the two seas is driven by differences in the heat and plankton advected into them, and the amount of primary production consumed in the upper water column. However, we suggest that the critical difference between the Chukchi and Barents Seas is the pre-cooled water entering the Chukchi Sea from the south. This cold water, and the winter mixing of the

  3. Relevance of risk predictions derived from a chronic species sensitivity distribution with cadmium to aquatic populations and ecosystems

    USGS Publications Warehouse

    Mebane, C.A.

    2010-01-01

    Criteria to protect aquatic life are intended to protect diverse ecosystems, but in practice are usually developed from compilations of single-species toxicity tests using standard test organisms that were tested in laboratory environments. Species sensitivity distributions (SSDs) developed from these compilations are extrapolated to set aquatic ecosystem criteria. The protectiveness of the approach was critically reviewed with a chronic SSD for cadmium comprising 27 species within 21 genera. Within the data set, one genus had lower cadmium effects concentrations than the SSD fifth percentile-based criterion, so in theory this genus, the amphipod Hyalella, could be lost or at least allowed some level of harm by this criteria approach. However, population matrix modeling projected only slightly increased extinction risks for a temperate Hyalella population under scenarios similar to the SSD fifth percentile criterion. The criterion value was further compared to cadmium effects concentrations in ecosystem experiments and field studies. Generally, few adverse effects were inferred from ecosystem experiments at concentrations less than the SSD fifth percentile criterion. Exceptions were behavioral impairments in simplified food web studies. No adverse effects were apparent in field studies under conditions that seldom exceeded the criterion. At concentrations greater than the SSD fifth percentile, the magnitudes of adverse effects in the field studies were roughly proportional to the laboratory-based fraction of species with adverse effects in the SSD. Overall, the modeling and field validation comparisons of the chronic criterion values generally supported the relevance and protectiveness of the SSD fifth percentile approach with cadmium. ?? 2009 Society for Risk Analysis.

  4. Changing Arctic ecosystems--measuring and forecasting the response of Alaska's terrestrial ecosystem to a warming climate

    USGS Publications Warehouse

    Pearce, John; DeGange, Anthony R.; Flint, Paul; Fondell, Tom F.; Gustine, David; Holland-Bartels, Leslie; Hope, Andrew G.; Hupp, Jerry; Koch, Josh; Schmutz, Joel; Talbot, Sandra; Ward, David; Whalen, Mary

    2012-01-01

    The Arctic Coastal Plain of northern Alaska is a complex landscape of lakes, streams, and wetlands scattered across low relief tundra that is underlain by permafrost. This region of the Arctic has experienced a warming trend over the past three decades, leading to thawing of on-shore permafrost and the disappearance of sea ice at an unprecedented rate. The loss of sea ice has increased ocean wave action, leading to higher rates of erosion and salt water inundation of coastal habitats. Warming temperatures also have advanced the overall phenology of the region, including earlier snowmelt, lake ice thaw, and plant growth. As a result, many migratory species now arrive in the Arctic several days earlier in spring than in the 1970s. Predicted warming trends for the future will continue to alter plant growth, ice thaw, and other basic landscape processes. These changes will undoubtedly result in different responses by wildlife (fish, birds, and mammals) and the food they rely upon (plants, invertebrates, and fish). However, the type of response by different wildlife populations and their habitats-either positively or negatively-remains largely unknown.

  5. Optical properties of natural dissolved organic matter (DOM) in aquatic ecosystems: Applications in ecosystem studies from headwater streams to the deep ocean. (Invited)

    NASA Astrophysics Data System (ADS)

    Jaffe, R.

    2010-12-01

    The study of natural dissolved organic material (DOM) contributes to the better understanding of ecosystem function as the carbon flux between environmental compartments represents an important linkage between terrestrial and aquatic ecosystems. Within freshwater and marine ecosystems, DOM typically represents the largest pool of detrital organic carbon and greatly exceeds the organic carbon present in living biomass. Thus, the sources and fate of DOM are important terms in carbon budgets. DOM can also influence ecosystem function by controlling microbial food webs, act as a means of nutrient transport, buffer pH and influence toxicity and bioavailability of pollutants, among others. DOM composition influences its ‘quality’ and thus its photo- and bio-reactivity, both of which exert a strong control of the diagenetic reworking of this carbon pool. However, the molecular composition of DOM is highly complex and diverse, and its characterization is a serious challenge to analytical chemists. In recent years, several novel analytical approaches to the characterization of DOM have evolved, including those that are highly structure specific and others that provide information on broader molecular characteristics. Whilst the former are usually expensive and time consuming, the latter, often based on optical properties measurements, feature high sample throughput at a reduced cost but at the expense of structural specificity. While both approaches are complementary under ideal conditions, the latter are best suited for studies involving large spatial and temporal scales. The analysis of DOM optical properties, in particular excitation emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC), has emerged as a practical tool for the broad characterization of DOM quality. This presentation will provide examples for the application of EEM-PARAFAC in assessing environmental dynamics of DOM on both spatial and temporal scales, and in both

  6. Marcellus and mercury: Assessing potential impacts of unconventional natural gas extraction on aquatic ecosystems in northwestern Pennsylvania.

    PubMed

    Grant, Christopher J; Weimer, Alexander B; Marks, Nicole K; Perow, Elliott S; Oster, Jacob M; Brubaker, Kristen M; Trexler, Ryan V; Solomon, Caroline M; Lamendella, Regina

    2015-01-01

    Mercury (Hg) is a persistent element in the environment that has the ability to bioaccumulate and biomagnify up the food chain with potentially harmful effects on ecosystems and human health. Twenty-four streams remotely located in forested watersheds in northwestern PA containing naturally reproducing Salvelinus fontinalis (brook trout), were targeted to gain a better understanding of how Marcellus shale natural gas exploration may be impacting water quality, aquatic biodiversity, and Hg bioaccumulation in aquatic ecosystems. During the summer of 2012, stream water, stream bed sediments, aquatic mosses, macroinvertebrates, crayfish, brook trout, and microbial samples were collected. All streams either had experienced hydraulic fracturing (fracked, n = 14) or not yet experienced hydraulic fracturing (non-fracked, n = 10) within their watersheds at the time of sampling. Analysis of watershed characteristics (GIS) for fracked vs non-fracked sites showed no significant differences (P > 0.05), justifying comparisons between groups. Results showed significantly higher dissolved total mercury (FTHg) in stream water (P = 0.007), lower pH (P = 0.033), and higher dissolved organic matter (P = 0.001) at fracked sites. Total mercury (THg) concentrations in crayfish (P = 0.01), macroinvertebrates (P = 0.089), and predatory macroinvertebrates (P = 0.039) were observed to be higher for fracked sites. A number of positive correlations between amount of well pads within a watershed and THg in crayfish (r = 0.76, P < 0.001), THg in predatory macroinvertebrates (r = 0.71, P < 0.001), and THg in brook trout (r = 0.52, P < 0.01) were observed. Stream-water microbial communities within the Deltaproteobacteria also shared a positive correlation with FTHg and to the number of well pads, while stream pH (r = -0.71, P < 0.001), fish biodiversity (r = -0.60, P = 0.02), and macroinvertebrate taxa richness (r = -0.60, P = 0.01) were negatively correlated with the number of well pads within a

  7. The effect of cannibalism intensity on net primary production and dynamics of trophic links in aquatic ecosystems.

    PubMed

    Shirobokova, I M; Pechurkin, N S

    2003-01-01

    A mathematical model was used to investigate the effect of cannibalism intensity on the net primary production and the dynamics of trophic links in an aquatic ecosystem characterized by cannibalism at the upper trophic level. A mathematical model of an aquatic ecosystem has been constructed, with the following principal trophic links: limiting nutrient concentration, producers (phytoplankton), nonpredatory and predatory zooplankton. The model takes into account the age structure of the predator and includes two age groups (the young and adults). The adult predators are cannibals feeding on both nonpredatory zooplankton and their own young, which consume phytoplankton. It has been found that when cannibalism intensity increases above a certain level, the concentrations of both adults and the young of the predators decrease. At the same time, the concentrations of the nonpredatory zooplankton and of nutrients increase, while the biomass of producers decreases. When the cannibalism intensity is low, the net primary production of the system increases to a certain level correlated with the increase in cannibalism intensity and drops sharply when the level of consumption of young is high. There is an optimal intensity of cannibalism, at which the productivity in the photosynthesis link is maximal. PMID:14503511

  8. Conducting a battery of bioassays for gold nanoparticles to derive guideline value for the protection of aquatic ecosystems.

    PubMed

    Nam, Sun-Hwa; Shin, Yu-Jin; Lee, Woo-Mi; Kim, Shin Woong; Kwak, Jin Il; Yoon, Sung-Ji; An, Youn-Joo

    2015-05-01

    Gold nanoparticles (Au-NPs) are used in many applications, including the manufacture of products like cosmetics, paints, and electrochemical immunosensors, and in the detection, diagnosis, and treatment of tumors. However, there are no legal or recommended guidelines for protecting aquatic ecosystems from Au-NPs. In this study, we conducted a battery of bioassays and present toxicity values for two bacteria, one alga, one euglena, three cladoceran, and two fish species that were exposed to Au-NPs. Guideline values for protecting aquatic ecosystems from Au-NPs were derived using methods that are generally used to derive water-quality guidelines and are used in Australia, New Zealand, Canada, the European Community (EC), and the USA. Au-NPs had adverse effects on all test species, including growth inhibition of both bacteria, the alga, and the euglena; mortality and immobilization in the three cladocerans; and developmental malformations in the embryos and larvae of the two fish. Guideline values of 0.15 and 0.04 × 10(10) particles/mL were derived for Au-NPs using a species sensitivity distribution (SSD) and assessment factor. The guideline value derived for Au-NPs using an assessment factor was more stringent than that derived using SSD. This is the first study to derive guideline values for nanoparticles in water environments. PMID:24983899

  9. Exploring new Routes for Identifying Phosphorus Species in Terrestrial and Aquatic Ecosystems with 31P NMR

    NASA Astrophysics Data System (ADS)

    Vestergren, Johan; Persson, Per; Sundman, Annelie; Ilstedt, Ulrik; Giesler, Reiner; Schleucher, Jürgen; Gröbner, Gerhard

    2014-05-01

    Phosphorus (P) is the primary growth-limiting nutrient in some of the world's biomes. Rock phosphate is a non-renewable resource and the major source of agricultural fertilizers. Predictions of P consumption indicate that rock phosphate mining may peak within 35 years, with severe impacts on worldwide food production1. Organic P compounds constitute a major fraction of soil P, but little is known about the dynamics and bioavailability of organic P species. Our aim is to develop new liquid and solid state 31P-NMR (nuclear magnetic resonance) techniques to identify P-species in water and soils; information required for correlating P speciation with plant and soil processes2, and eventually to improve P use. Soil organic P is frequently extracted using NaOH/EDTA, followed by characterization of the extract by solution 31P-NMR. However, the obtained NMR spectra usually have poor resolution due to line broadening caused by the presence of paramagnetic ions. Therefore, we successfully developed an approach to avoid paramagnetic line broadening by precipitation of metal sulfides. Sulfide precipitation dramatically reduces NMR line widths for soil extracts, without affecting P-composition. The resulting highly improved resolution allowed us to apply for the first time 2D 1H,31P-NMR methods to identify different P monoesters in spectral regions which are extremely crowded in 1D NMR spectra.3 By exploiting 2D 1H-31P NMR spectra of soil extracts we were able to unambiguously identify individual organic P species by combining 31P and 1H chemical shifts and coupling constants. This approach is even suitable for a structural characterization of unknown P-components and for tracing degradation pathways between diesters and monoesters3,4.Currently we apply our approach on boreal4 and tropical soils with focus on Burkina Faso. In addition we also monitor P-species in aqueos ecosystems. For this purpose stream water from the Krycklan catchment in northern Sweden5 has been used to

  10. The nearshore western Beaufort Sea ecosystem: Circulation and importance of terrestrial carbon in arctic coastal food webs

    NASA Astrophysics Data System (ADS)

    Dunton, Kenneth H.; Weingartner, Thomas; Carmack, Eddy C.

    2006-10-01

    . Calculations from isotopic mixing equations indicate cod from lagoons may derive 70% of their carbon from terrestrial sources. The δ15N values of lagoon fish were also 4‰ lower than coastal specimens, reflective of the lower δ15N values of terrestrially derived nitrogen (0-1.5‰ compared to 5-7‰ for phytoplankton). The role of terrestrial carbon in arctic estuarine food webs is especially important in view of the current warming trend in the arctic environment and the role of advective processes that transport carbon along the nearshore shelf. Biogeochemical studies of the arctic coastal estuarine environment may provide more insights into the function of these biologically complex ecosystems.

  11. Spatial and temporal variation of an ice-adapted predator's feeding ecology in a changing Arctic marine ecosystem.

    PubMed

    Yurkowski, David J; Ferguson, Steven H; Semeniuk, Christina A D; Brown, Tanya M; Muir, Derek C G; Fisk, Aaron T

    2016-03-01

    Spatial and temporal variation can confound interpretations of relationships within and between species in terms of diet composition, niche size, and trophic position (TP). The cause of dietary variation within species is commonly an ontogenetic niche shift, which is a key dynamic influencing community structure. We quantified spatial and temporal variations in ringed seal (Pusa hispida) diet, niche size, and TP during ontogeny across the Arctic-a rapidly changing ecosystem. Stable carbon and nitrogen isotope analysis was performed on 558 liver and 630 muscle samples from ringed seals and on likely prey species from five locations ranging from the High to the Low Arctic. A modest ontogenetic diet shift occurred, with adult ringed seals consuming more forage fish (approximately 80 versus 60 %) and having a higher TP than subadults, which generally decreased with latitude. However, the degree of shift varied spatially, with adults in the High Arctic presenting a more restricted niche size and consuming more Arctic cod (Boreogadus saida) than subadults (87 versus 44 %) and adults at the lowest latitude (29 %). The TPs of adult and subadult ringed seals generally decreased with latitude (4.7-3.3), which was mainly driven by greater complexity in trophic structure within the zooplankton communities. Adult isotopic niche size increased over time, likely due to the recent circumpolar increases in subarctic forage fish distribution and abundance. Given the spatial and temporal variability in ringed seal foraging ecology, ringed seals exhibit dietary plasticity as a species, suggesting adaptability in terms of their diet to climate change. PMID:26210748

  12. From a microcosm to the catchment scale: studying the fate of organic runoff pollutants in aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Böttcher, T.; Schroll, R.

    2009-04-01

    Spray-drift, drainage, erosion and runoff events are the major causes responsible for deportation of agrochemicals as micropollutants to aquatic non-target sites. These processes can lead to the contamination of nearby freshwater ecosystems with considerably high concentrations of xenobiotics. Thus, it is important to unravel the fate of these pollutants and to evaluate their ecological effects. A novel approach to address this goal was established by the development of a microcosm with multiple sampling abilities enabling quantitative assessment of organic volatilisation, mineralization, metabolization and distribution within the aquatic ecosystem. This microcosm system was designed to support modelling approaches of the catchment scale and gain insights into the fate of pesticides simulating a large scale water body. The potential of this microcosm was exemplified for Isoproturon (IPU), a phenylurea derived systemic herbicide, which is frequently found as contaminant in water samples and with the free-floating macrophyte Lemna minor as non-target species, that is common to occur in rural water bodies. During 21 days exposure time, only a small amount of 14C labeled IPU was removed from the aquatic medium. The major portion (about 5%) was accumulated by Lemna minor resulting in a BCF of 15.8. IPU-volatilisation was very low with 0.13% of the initially applied herbicide. Only a minor amount of IPU was completely metabolized, presumably by rhizosphere microorganisms and released as 14CO2. The novel experimental system allowed to quantitatively investigate the fate of IPU and showed a high reproducibility with a mean average 14C-recovery rate of 97.1

  13. Terrestrial and aquatic ecosystem responses to late Holocene climate change recorded in the sediments of Lochan Uaine, Cairngorms, Scotland

    NASA Astrophysics Data System (ADS)

    Oldfield, Frank; Battarbee, Richard W.; Boyle, John F.; Cameron, Nigel G.; Davis, Basil; Evershed, Richard P.; McGovern, Andrew D.; Jones, Vivienne; Thompson, Roy; Walker (née Wake), Rebecca

    2010-04-01

    We summarise the results of a range of sediment-based studies at Lochan Uaine, a remote corrie lake in the heart of the Cairngorm massif in Scotland. The site lies above the Holocene forest limit and has been minimally affected by human activities. The results presented are mainly based on magnetic measurements, element analysis, granulometry, organic geochemical analysis and pollen analysis carried out over a period of some 15 years. The magnetic properties and element concentrations record a coherent sequence of changes reflecting mainly stages in catchment erosion. In terms of the chronology developed for the sedimentary record from the site, increases in allochthonous, minerogenic sediment delivery to the lake occurred around 1000 BC, AD 330-480 and AD 1260-1410. The only notable change in the pollen diagram records a period of deforestation at lower altitude predating the last of the periods of increased erosion. The organic geochemistry analyses record a series of higher frequency responses in the aquatic ecosystem, already noted in previous papers, e.g. Battarbee et al. (2001). These include fluctuations in organic carbon content and in the concentrations of biomarkers indicative of changing lake productivity. Both the terrestrial and aquatic ecosystem responses are superimposed on a longer-term trend of declining aquatic productivity, progressive catchment weathering and increasing erosion. The sediments of Lochan Uaine thus appear to have recorded complex system responses on three timescales reflecting (a) the long term decline in northern hemisphere insolation during the Holocene, (b) the millennial scale forcing of the kind found in many other mid-late Holocene records and (c) much shorter term, quasi-cyclic but clearly a-periodic sub-millennial fluctuations.

  14. Development of a dynamic model for estimating the food web transfer of chemicals in small aquatic ecosystems.

    PubMed

    Nfon, Erick; Armitage, James M; Cousins, Ian T

    2011-11-15

    A dynamic combined fate and food web model was developed to estimate the food web transfer of chemicals in small aquatic ecosystems (i.e. ponds). A novel feature of the modeling approach is that aquatic macrophytes (submerged aquatic vegetation) were included in the fate model and were also a food item in the food web model. The paper aims to investigate whether macrophytes are effective at mitigating chemical exposure and to compare the modeling approach developed here with previous modeling approaches recommended in the European Union (EU) guideline for risk assessment of pesticides. The model was used to estimate bioaccumulation of three hypothetical chemicals of varying hydrophobicity in a pond food web comprising 11 species. Three different macrophyte biomass densities were simulated in the model experiments to determine the influence of macrophytes on fate and bioaccumulation. Macrophytes were shown to have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log KOW>=5. Modeled peak concentrations in biota were highest for the scenarios with the lowest macrophyte biomass density. The distribution and food web transfer of the hypothetical compound with the lowest hydrophobicity (log KOW=3) was not affected by the inclusion of aquatic macrophytes in the pond environment. For the three different hypothetical chemicals and at all macrophyte biomass densities, the maximum predicted concentrations in the top predator in the food web model were at least one order of magnitude lower than the values estimated using methods suggested in EU guidelines. The EU guideline thus provides a highly conservative estimate of risk. In our opinion, and subject to further model evaluation, a realistic assessment of dynamic food web transfer and risk can be obtained using the model presented here. PMID:21962596

  15. Heavy metal contents in water, sediment and fish in a karst aquatic ecosystem of the Plitvice Lakes National Park (Croatia).

    PubMed

    Vukosav, Petra; Mlakar, Marina; Cukrov, Neven; Kwokal, Zeljko; Pižeta, Ivanka; Pavlus, Natalija; Spoljarić, Ivanka; Vurnek, Maja; Brozinčević, Andrijana; Omanović, Dario

    2014-03-01

    An evaluation of the quality status of the pristine karst, tufa depositing aquatic environment of the Plitvice Lakes National Park based on the analysis of heavy (ecotoxic) metals was examined for the first time. Analyses of trace metals in water, sediment and fish (Salmo trutta, Oncorhynchus mykiss, Squalius cephalus) samples were conducted either by stripping voltammetry (Zn, Cd, Pb and Cu) or cold vapour atomic absorption spectrometry (Hg). The concentration of dissolved trace metals in water was very low revealing a pristine aquatic environment (averages were, in ng/L: 258 (Zn), 10.9 (Cd), 11.7 (Pb), 115 (Cu) and 1.22 (Hg)). Slightly enhanced concentrations of Cd (up to 50 ng/L) and Zn (up to 900 ng/L) were found in two main water springs and are considered as of natural origin. Observed downstream decrease in concentration of Cd, Zn and Cu in both water and sediments is a consequence of the self-purification process governed by the formation and settling of authigenic calcite. Anthropogenic pressure was spotted only in the Kozjak Lake: Hg concentrations in sediments were found to be up to four times higher than the baseline value, while at two locations, Pb concentrations exceeded even a probable effect concentration. The increase of Hg and Pb was not reflected on their levels in the fish tissues; however, significant correlations were found between Cd level in fish tissues (liver and muscle) and in the water/sediment compartments, while only partial correlations were estimated for Zn and Cu. A high discrepancy between values of potentially bioavailable metal fraction estimated by different modelling programs/models raised the question about the usefulness of these data as a parameter in understanding/relating the metal uptake and their levels in aquatic organism. The aquatic environment of the Plitvice Lakes National Park is characterized, in general, as a clean ecosystem. PMID:24288066

  16. Patterns of Life in the Water. Student Field Studies of Two of Franklin County's Aquatic Ecosystems.

    ERIC Educational Resources Information Center

    O'Toole, Kathleen P.

    Described in this manual are two field investigations which utilize the natural environment to teach ecological principles to high school students. In groups of five to ten, students study two aquatic environments and then prepare a booklet which summarizes their work. The manual is divided into four parts: (1) teacher's guide; (2) student's…

  17. A FRAMEWORK TO ASSESS THE RELATIVE VULNERABILITY OF AQUATIC ECOSYSTEM SERVICES TO GLOBAL STRESSORS

    EPA Science Inventory

    Over the next several years, the Environmental Protection Agency's (EPA's) Global Change Research Program within the Office of Research and Development (ORD) will conduct a series of case studies in different regions of the United States to evaluate potential changes in aquatic e...

  18. Aquatic Ecosystem Services in the 21st Century Northeast Corridor: Assessment Using a Regional Earth System Model

    NASA Astrophysics Data System (ADS)

    Rosenzweig, B.; Miara, A.; Stewart, R. J.; Wollheim, W. M.; Vorosmarty, C. J.

    2012-12-01

    Aquatic ecosystems of the Northeast United States will be significantly impacted by both global climate change and the regional-scale strategic management decisions made in the next few years. We have developed a Regional Earth System Model for the Northeast Corridor (NE-RESM) that simulates the impacts of climate, land use, and development policy on the interacting cycles of energy, water, carbon and nutrients. The NE-RESM will provide a unique and critically needed tool for policymakers to understand how their current decisions will impact ecosystem services over the 21st Century. To test our modeling framework, we conducted a retrospective experiment focusing on the water-energy-economy nexus during the period 2000-2010. Component models were developed to 'translate' physical outputs from the NE-RESM - such as stream discharge and water temperature - into ecosystem services including water regulation for thermoelectric cooling and the ability for streams to serve as a refugia for wildlife. Simulations were performed both with and without Clean Water Act limits on thermal pollution. Through this work, we were able to obtain spatially distributed information on how these laws impact power generation by the thermoelectric sector but also enable Northeast streams to serve as habitat for temperature-sensitive aquatic species (Brook Trout, Atlantic Salmon, River Herring and the American Eel). Our ongoing research examines future climate and policy scenarios through 2100. We are considering the impact of changing land cover patterns (a return to agriculture vs. suburban sprawl) and various strategies to meet energy and municipal water needs under different Representative Concentration Pathways (RCPs) developed for the Intergovernmental Panel on Climate Change's Fifth Assessment Report (IPCC AR5).

  19. Project AProWa: a national view on managing trade-offs between agricultural production and conservation of aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Dietzel, Anne; Rahn, Eric; Stamm, Christian

    2014-05-01

    Swiss agriculture is legally committed to fulfill several, partially conflicting goals such as agricultural production on the one hand and the conservation of natural resources on the other hand. In the context of the research project AProWa ("Agricultural Production and Water"), the relationships between the production aspect and the conservation of aquatic ecosystems is analyzed with a holistic approach. Agricultural production and the protection of water resources have high potential for conflicts: Farmers use ground and surface water to irrigate their fields. On the other hand, drainage systems enable the production on otherwise unfavorably wet soils. These in turn often affect ground water recharge and divert precipitation directly into surface waters, which changes their hydrological regime. Typically, drainage systems also elevate the input of nutrients and pesticides into the water bodies. In general, applied fertilizers, plant protection products, veterinary drugs and phytohormones of cultivated plants are introduced into the ground and surface waters through different processes such as drift, leaching, runoff, preferential flow or erosion. They influence the nutrient cycles and ecological health of aquatic systems. The nutrient and pesticide loss processes themselves can be altered by tillage operations and other agricultural practices. Furthermore, the competition for space can lead to additional conflicts between agriculture and the protection of aquatic ecosystems. For example, channelized or otherwise morphologically changed rivers do not have a natural discharge pattern and are often not suitable for the local flora and fauna; but naturally meandering rivers need space that cannot be used for agriculture. In a highly industrialized and densely populated country like Switzerland, all these potential conflicts are of importance. Although it is typically seen as a water-rich country, local and seasonal overexploitation of rivers through water extraction

  20. The remote sensing of aquatic macrophytes Part 1: Color-infrared aerial photography as a tool for identification and mapping of littoral vegetation. Part 2: Aerial photography as a quantitative tool for the investigation of aquatic ecosystems. [Lake Wingra, Wisconsin

    NASA Technical Reports Server (NTRS)

    Gustafson, T. D.; Adams, M. S.

    1973-01-01

    Research was initiated to use aerial photography as an investigative tool in studies that are part of an intensive aquatic ecosystem research effort at Lake Wingra, Madison, Wisconsin. It is anticipated that photographic techniques would supply information about the growth and distribution of littoral macrophytes with efficiency and accuracy greater than conventional methods.

  1. Mercury in freshwater ecosystems of the Canadian Arctic: recent advances on its cycling and fate.

    PubMed

    Chételat, John; Amyot, Marc; Arp, Paul; Blais, Jules M; Depew, David; Emmerton, Craig A; Evans, Marlene; Gamberg, Mary; Gantner, Nikolaus; Girard, Catherine; Graydon, Jennifer; Kirk, Jane; Lean, David; Lehnherr, Igor; Muir, Derek; Nasr, Mina; Poulain, Alexandre J; Power, Michael; Roach, Pat; Stern, Gary; Swanson, Heidi; van der Velden, Shannon

    2015-03-15

    The Canadian Arctic has vast freshwater resources, and fish are important in the diet of many Northerners. Mercury is a contaminant of concern because of its potential toxicity and elevated bioaccumulation in some fish populations. Over the last decade, significant advances have been made in characterizing the cycling and fate of mercury in these freshwater environments. Large amounts of new data on concentrations, speciation and fluxes of Hg are provided and summarized for water and sediment, which were virtually absent for the Canadian Arctic a decade ago. The biogeochemical processes that control the speciation of mercury remain poorly resolved, including the sites and controls of methylmercury production. Food web studies have examined the roles of Hg uptake, trophic transfer, and diet for Hg bioaccumulation in fish, and, in particular, advances have been made in identifying determinants of mercury levels in lake-dwelling and sea-run forms of Arctic char. In a comparison of common freshwater fish species that were sampled across the Canadian Arctic between 2002 and 2009, no geographic patterns or regional hotspots were evident. Over the last two to four decades, Hg concentrations have increased in some monitored populations of fish in the Mackenzie River Basin while other populations from the Yukon and Nunavut showed no change or a slight decline. The different Hg trends indicate that the drivers of temporal change may be regional or habitat-specific. The Canadian Arctic is undergoing profound environmental change, and preliminary evidence suggests that it may be impacting the cycling and bioaccumulation of mercury. Further research is needed to investigate climate change impacts on the Hg cycle as well as biogeochemical controls of methylmercury production and the processes leading to increasing Hg levels in some fish populations in the Canadian Arctic. PMID:24993511

  2. Effects of Disturbances on Vegetation Composition and Permafrost Thaw in Boreal Forests and Tundra Ecosystems of the Siberian Arctic

    NASA Astrophysics Data System (ADS)

    Ramos, E.; Alexander, H. D.; Natali, S.

    2014-12-01

    In Arctic ecosystems, climate-driven changes to the thermal regime of permafrost soils have the potential to create surface disturbances that influence vegetation dynamics and underlying soil properties. Disturbance-mediated changes in vegetation are important because vegetation and the accumulation of soil organic matter drive ecosystem carbon (C) dynamics and contribute to the insulation of soils and protection of permafrost from thaw. We examined the effect of two disturbance types—thermokarsts and frost boils—to determine disturbance effects on the vegetation community and soil properties in northeast Siberia. In summer 2014, we measured vegetation cover, soil moisture, soil temperature, and thaw depth in two thermokarst sites within boreal forests, two frost boil sites in tundra, and in adjacent undisturbed sites within both ecosystems. Both thermokarst and frost boils resulted in decreased vegetation cover and greater exposure of mineral soils (10-40% bare soils vs. 0% in undisturbed), and consequently, 2-3 times higher soil temperature and deeper thaw depth. Compared to undisturbed areas, soil moisture was 3-4 times higher in thermokarst areas but 1.2-2 times lower in frost boil areas, which reflected differences in microtopography between these two disturbance types. In both thermokarst and frost boil disturbed areas, deciduous and evergreen shrubs covered only 5 and 10%, respectively, compared to approximately 10 and 20%, respectively, in undisturbed areas. In general, graminoids were substantially more abundant (2-20 times) in disturbed areas than in those undisturbed. These results highlight important linkages between disturbances, vegetation communities, and permafrost soils, and contribute to our understanding of how changes in arctic vegetation dynamics as direct and/or indirect consequences of climate change have the potential to impact permafrost C pools.

  3. ORGANIZATION AND ADAPTATION OF AQUATIC LABORATORY ECOSYSTEMS EXPOSED TO THE PESTICIDE DIELDRIN

    EPA Science Inventory

    A system of generalizations pertaining to the organization, development and persistence, adaptation, and productivity of ecological systems and their response to toxic substances was formulated. Laboratory ecosystems composed of persistent populations of guppies, amphipods, snail...

  4. 76 FR 55060 - Aquatic Ecosystems, Water Quality, and Global Change: Challenges of Conducting Multi-Stressor...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-06

    ... resilience of ecosystems and human systems to a variety of existing stresses and mal- adaptations. DATES: The... a result of existing global change stresses and mal-adaptations. The work described in this...

  5. Interacting effects of elevated temperature and additional water on plant physiology and net ecosystem carbon fluxes in a high Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Maseyk, Kadmiel; Seibt, Ulrike; Lett, Céline; Lupascu, Massimo; Czimczik, Claudia; Sullivan, Patrick; Welker, Jeff

    2013-04-01

    Arctic ecosystems are experiencing temperature increases more strongly than the global average, and increases in precipitation are also expected amongst the climate impacts on this region in the future. These changes are expected to strongly influence plant physiology and soil biogeochemistry with subsequent implications for system carbon balance. We have investigated the effects of a long-term (10 years) increase in temperature, soil water and the combination of both on a tundra ecosystem at a field manipulation experiment in NW Greenland. Leaf gas exchange, chlorophyll fluorescence, carbon (C) and nitrogen (N) content and leaf isotopic composition, and leaf morphology were measured on Salix arctica plants in treatment and control plots in June-July 2011, and continuous measurements of net plant and soil fluxes of CO2 and water were made using automatic chambers coupled to a trace gas laser analyzer. Plants in the elevated temperature (T2) treatment had the highest photosynthetic capacity in terms of net CO2 assimilation rates and photosystem II efficiencies, and lowest rates of non-photochemical energy dissipation during photosynthesis. T2 plants also had the highest leaf N content, specific leaf area (SLA) and saturation light level of photosynthesis. It appears that warming increases soil N availability, which the plants direct towards increasing photosynthetic capacity and producing larger thinner leaves. On the other hand, the plants in the plots with both elevated temperatures and additional water (T2W) had the lowest photosystem II efficiencies and the highest rates of non-photochemical energy dissipation, due more to higher levels of constitutive energy dissipation than regulated thermal quenching. Watering, both in combination with higher temperatures and alone (W treatment), also reduced leaf SLA and leaf N relative to control plots. However, net photosynthetic rates remained similar to control plants, due in part to higher stomatal conductance (W) and

  6. Deglacial and Holocene Evolution of Climate and Terrestrial Ecosystems in the Western Arctic.

    NASA Astrophysics Data System (ADS)

    Edwards, M. E.

    2006-12-01

    The late- and post-glacial history of the Western Arctic land area is distinguished by the region being largely unglaciated (away from the coastal cordillera), and by a considerable reduction in areal extent due to sea-level rise. Between ca. 15 and 10 cal ka B.P. rising summer temperatures and increasing precipitation related to orbital forcing and adjustments in the hemispheric circulation resulted in widespread replacement of herbaceous vegetation with deciduous woody plants, rising lake levels, reduction of eolian activity, and the onset of thermokarst erosion. These changes had impacts at both global and regional levels, e.g., reduced atmospheric dust loading, increased carbon flux to the atmosphere, and feedbacks to the surface energy balance. The Younger Dryas event (ca. 12.9-11.6 cal ka B.P.) is not strongly expressed in terrestrial records. Some localities near the Pacific coast and in eastern Siberia record a weak to moderate climatic reversal, but central, northern, and eastern areas show no consistent signal. This suggests a muted response of the North Pacific and/or adjacent lands to events in the North Atlantic. However, the nearly coincident flooding and eventual breaching of the Bering land bridge probably reduced continentality in adjacent regions and may be linked to early-Holocene increases in effective moisture in both summer and winter. At ca. 10 cal ka B.P. evergreen conifers expanded to dominance or co-dominance much of the forest zone on both sides of the Bering Strait. This appears to be an example of a moisture-driven vegetation change in a region normally expected to respond largely to temperature. Particularly in Alaska and NW Canada, it likely led to two significant ecosystem changes: a vegetation-driven shift in the fire regime and enhanced paludification. The former could have influenced atmospheric chemistry and the latter nutrient availability, the status of permafrost, and the export of organic carbon and other nutrients to

  7. Removal of terrestrial DOC in aquatic ecosystems of a temperate river network

    NASA Astrophysics Data System (ADS)

    Wollheim, W. M.; Stewart, R. J.; Aiken, G. R.; Butler, K. D.; Morse, N. B.; Salisbury, J.

    2015-08-01

    Surface waters play a potentially important role in the global carbon balance. Dissolved organic carbon (DOC) fluxes are a major transfer of terrestrial carbon to river systems, and the fate of DOC in aquatic systems is poorly constrained. We used a unique combination of spatially distributed sampling of three DOC fractions throughout a river network and modeling to quantify the net removal of terrestrial DOC during a summer base flow period. We found that aquatic reactivity of terrestrial DOC leading to net loss is low, closer to conservative chloride than to reactive nitrogen. Net removal occurred mainly from the hydrophobic organic acid fraction, while hydrophilic and transphilic acids showed no net change, indicating that partitioning of bulk DOC into different fractions is critical for understanding terrestrial DOC removal. These findings suggest that river systems may have only a modest ability to alter the amounts of terrestrial DOC delivered to coastal zones.

  8. Mycobacterium ulcerans Ecological Dynamics and Its Association with Freshwater Ecosystems and Aquatic Communities: Results from a 12-Month Environmental Survey in Cameroon

    PubMed Central

    Garchitorena, Andrés; Roche, Benjamin; Kamgang, Roger; Ossomba, Joachim; Babonneau, Jérémie; Landier, Jordi; Fontanet, Arnaud; Flahault, Antoine

    2014-01-01

    Background Mycobacterium ulcerans (MU) is the agent responsible for Buruli Ulcer (BU), an emerging skin disease with dramatic socioeconomic and health outcomes, especially in rural settings. BU emergence and distribution is linked to aquatic ecosystems in tropical and subtropical countries, especially to swampy and flooded areas. Aquatic animal organisms are likely to play a role either as host reservoirs or vectors of the bacilli. However, information on MU ecological dynamics, both in space and time, is dramatically lacking. As a result, the ecology of the disease agent, and consequently its mode of transmission, remains largely unknown, which jeopardizes public health attempts for its control. The objective of this study was to gain insight on MU environmental distribution and colonization of aquatic organisms through time. Methodology/Principal Findings Longitudinal sampling of 32 communities of aquatic macro-invertebrates and vertebrates was conducted from different environments in two BU endemic regions in Cameroon during 12 months. As a result, 238,496 individuals were classified and MU presence was assessed by qPCR in 3,084 sample-pools containing these aquatic organisms. Our study showed a broad distribution of MU in all ecosystems and taxonomic groups, with important regional differences in its occurrence. Colonization dynamics fluctuated along the year, with the highest peaks in August and October. The large variations observed in the colonization dynamics of different taxonomic groups and aquatic ecosystems suggest that the trends shown here are the result of complex ecological processes that need further investigation. Conclusion/Perspectives This is the largest field study on MU ecology to date, providing the first detailed description of its spatio-temporal dynamics in different aquatic ecosystems within BU endemic regions. We argue that coupling this data with fine-scale epidemiological data through statistical and mathematical models will provide a

  9. Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    SciTech Connect

    Wullschleger, Stan

    2012-03-22

    Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

  10. Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    ScienceCinema

    Wullschleger, Stan [ORNL

    2013-01-22

    Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

  11. USING LAKE SEDIMENT MERCURY FLUX RATIOS TO EVALUATE THE REGIONAL AND CONTINENTAL DIMENSIONS OF MERCURY DEPOSITION IN ARCTIC AND BOREAL ECOSYSTEMS

    EPA Science Inventory

    Anthropogenically elevated Hg deposition in arctic and subarctic ecosystems is potentially a serious environmental problem, particularly in northern Europe and North America. To determine the magnitude of this concern, it is necessary to make an evaluation over a broad spatial sc...

  12. The mysteriously variable half-life of dissolved organic matter in aquatic ecosystems: artefact or insight?

    NASA Astrophysics Data System (ADS)

    Evans, Chris; Fovet, Ophelie; Jones, Tim; Jones, Davey; Moldan, Filip; Futter, Martyn

    2016-04-01

    Dissolved organic matter (DOM) fluxes from land to water represent an important loss term in the terrestrial carbon balance, a major pathway in the global carbon cycle, a significant influence on aquatic light, nutrient and energy regimes, and an important concern for drinking water production. Although freshwaters are now recognised as zones of active carbon cycling, rather than passive conduits for carbon transport, evidence regarding the magnitude of, and controls on, DOM cycling in aquatic systems is incomplete and in some cases seemingly contradictory, with DOM 'half-lives' ranging from a few days to many years. Bringing together experimental, isotopic, catchment mass balance and modelling data, we suggest that apparently conflicting results can be reconciled through understanding of differences in: i) the terrestrial sources of DOM within heterogeneous landscapes, and consequent differences in its reactivity and stoichiometry; ii) experimental methodologies (i.e. which reactions are actually being measured), and iii) the extent of prior transformation of DOM upstream of the point of study. We argue that rapid photo-degradation, particularly of peat-derived DOM, is a key process in headwaters, whilst apparently slow DOM turnover in downstream, agriculturally-influenced lakes and rivers can partly be explained by the offsetting effect of in situ DOM production. This production appears to be strongly constrained by nutrient supply, thus linking DOM turnover and composition to the supply of inorganic nutrient inputs from diffuse agricultural pollution, and also providing a possible mechanistic link between aquatic DOM production and terrestrial DOM breakdown via the mineralisation and re-assimilation of organic nutrients. A more complete conceptual understanding of these interlinked processes will provide an improved understanding of the sources and fate of aquatic DOM, its role in the global carbon cycle, and the impact of anthropogenic activities, for example

  13. Techniques for monitoring the environmental impact of insecticides on aquatic ecosystems. Agricultural handbook, (final)

    SciTech Connect

    Not Available

    1984-01-01

    Aquatic sampling has evolved at an exceptional pace in recent years. The manual is designed primarily for the field technician rather than the experienced research ecologist. Its purpose is to describe the equipment, procedures, and hypotheses potentially applicable to or previously used for studies of the impact of spruce budworm pesticides. The manual focuses on the field study of fresh water macroinvertebrates and fish, and covers both lotic (flowing) and lentic (stagnant) environments.

  14. Trophic complexity enhances ecosystem functioning in an aquatic detritus-based model system.

    PubMed

    Jabiol, Jérémy; McKie, Brendan G; Bruder, Andreas; Bernadet, Caroline; Gessner, Mark O; Chauvet, Eric

    2013-09-01

    1. Understanding the functional significance of species interactions in ecosystems has become a major challenge as biodiversity declines rapidly worldwide. Ecosystem consequences arising from the loss of diversity either within trophic levels (horizontal diversity) or across trophic levels (vertical diversity) are well documented. However, simultaneous losses of species at different trophic levels may also result in interactive effects, with potentially complex outcomes for ecosystem functioning. 2. Because of logistical constraints, the outcomes of such interactions have been difficult to assess in experiments involving large metazoan species. Here, we take advantage of a detritus-based model system to experimentally assess the consequences of biodiversity change within both horizontal and vertical food-web components on leaf-litter decomposition, a fundamental process in a wide range of ecosystems. 3. Our concurrent manipulation of fungal decomposer diversity (0, 1 or 5 species), detritivore diversity (0, 1 or 3 species), and the presence of predatory fish scent showed that trophic complexity is key to eliciting diversity effects on ecosystem functioning. Specifically, although fungi and detritivores tended to promote decomposition individually, rates were highest in the most complete community where all trophic levels were represented at the highest possible species richness. In part, the effects were trait-mediated, reflected in the contrasting foraging responses of the detritivore species to predator scent. 4. Our results thus highlight the importance of interactive effects of simultaneous species loss within multiple trophic levels on ecosystem functioning. If a common phenomenon, this outcome suggests that functional ecosystem impairment resulting from widespread biodiversity loss could be more severe than inferred from previous experiments confined to varying diversity within single trophic levels. PMID:23574276

  15. Cumulative effect assessment in Canada: a regional framework for aquatic ecosystems

    SciTech Connect

    Dube, Monique G

    2003-10-01

    Sustainable development of the aquatic environment depends upon routine and defensible cumulative effects assessment (CEA). CEA is the process of predicting the consequences of development relative to an assessment of existing environmental quality. Theoretically, it provides an on-going mechanism to evaluate if levels of development exceed the environment's assimilative capacity; i.e., its ability to sustain itself. In practice, the link between CEA and sustainable development has not been realized because CEA concepts and methods have developed along two dichotomous tracks. One track views CEA as an extension of the environmental assessment (EA) process for project developments. Under this track, stressor-based (S-B) methods have been developed where the emphasis is on local, project-related stressors, their link with aquatic indicators, and the potential for environmental effects through stressor-indicator interactions. S-B methods focus on the proposed development and prediction of project-related effects. They lack a mechanism to quantify existing aquatic quality especially at scales broader than an isolated development. This limitation results in the prediction of potential effects relative to a poorly defined baseline state. The other track views CEA as a broader, regional assessment tool where effects-based (E-B) methods specialize in quantification of existing aquatic effects over broad spatial scales. However, the predictive capabilities of E-B methods are limited because they are retrospective, i.e., the stressor causing the effect is identified after the effect has been measured. When used in isolation, S-B and E-B methods do not address CEA in the context necessary for sustainable development. However, if the strengths of these approaches were integrated into a holistic framework for CEA, an operational mechanism would exist to better monitor and assess sustainable development of our aquatic resources. This paper reviews the existing conceptual basis

  16. Inclusion of Additional Plant Species and Trait Information in Dynamic Vegetation Modeling of Arctic Tundra and Boreal Forest Ecosystem

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Patil, V.; Roach, J.; Griffith, B.; McGuire, A. D.

    2015-12-01

    Dynamic vegetation models (DVMs) have been developed to model the ecophysiological characteristics of plant functional types in terrestrial ecosystems. They have frequently been used to answer questions pertaining to processes such as disturbance, plant succession, and community composition under historical and future climate scenarios. While DVMs have proved useful in these types of applications, it has often been questioned if additional detail, such as including plant dynamics at the species-level and/or including species-specific traits would make these models more accurate and/or broadly applicable. A sub-question associated with this issue is, 'How many species, or what degree of functional diversity, should we incorporate to sustain ecosystem function in modeled ecosystems?' Here, we focus on how the inclusion of additional plant species and trait information may strengthen dynamic vegetation modeling in applications pertaining to: (1) forage for caribou in northern Alaska, (2) above- and belowground carbon storage in the boreal forest and lake margin wetlands of interior Alaska, and (3) arctic tundra and boreal forest leaf phenology. While the inclusion of additional information generally proved valuable in these three applications, this additional detail depends on field data that may not always be available and may also result in increased computational complexity. Therefore, it is important to assess these possible limitations against the perceived need for additional plant species and trait information in the development and application of dynamic vegetation models.

  17. Sedimentation plan to assess the impact of geothermal activities to the aquatic ecosystem in the Geyers Calistoga KGRA

    SciTech Connect

    Ireland, R.R.

    1981-05-19

    The prevention of sedimentation or siltation in aquatic ecosystems is always a key environmental issue in the development and operation of power plant units. This report describes a field program which will assess the amount of sedimentation in the streams and tributaties of the Geysers-Calistoga Known Geothermal Resource Area (KGRA) due to development-related or other site-specific activities. This sediment plan is one part of a four part venture - the others are water quality, benthic invertebrates and fisheries studies - initiated by the California Energy Commission and involving numerous California organizations. Included in this report are the cost breakdowns for each phase, maps and rationale of the sampling sites, the methodology for the laboratory sample processing, and examples of the type of graphic and tabular output expected.

  18. Nonlinear responses to nitrogen and strong interactions with nitrogen and phosphorus additions drastically alter the structure and function of a high arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Arens, Seth J. T.; Sullivan, Patrick F.; Welker, Jeffrey M.

    2008-09-01

    Significant changes in ecosystem CO2 exchange and vegetation characteristics were observed following multiple additions of nitrogen (N) and factorial additions of N and phosphorus (P) to prostrate dwarf-shrub, herb tundra in Northwest Greenland. Ecosystem CO2 exchange and vegetation cover and composition were very sensitive to low rates of N inputs (0.5 g m-2 y-1), indicating that even low rates of atmospheric N deposition may alter high arctic ecosystem structure and function. Increasing N addition from 1 to 5 g N m-2 y-1 did not alter CO2 exchange or vegetation characteristics, suggesting the ecosystem had become N saturated. Factorial additions of both N and P released the ecosystem from N saturation and dramatically increased gross ecosystem photosynthesis (+500%) and ecosystem respiration (+250%), such that the ecosystem switched from a small source of CO2 to a small sink for CO2 at midday during the 2005 growing season. Changes in the component fluxes of CO2 exchange were largely explained by a doubling of the normalized difference vegetation index, a 100% increase in vascular plant cover and dramatic increases in the abundance of several previously rare grass species. Our results clearly demonstrate that high arctic prostrate dwarf-shrub, herb tundra is highly sensitive to low levels of N addition and that future increases in N deposition or N mineralization will likely lead to change in carbon cycling and vegetation characteristics, but the magnitude of the response will be constrained by P availability.

  19. Uptake of uranium by aquatic plants growing in fresh water ecosystem around uranium mill tailings pond at Jaduguda, India.

    PubMed

    Jha, V N; Tripathi, R M; Sethy, N K; Sahoo, S K

    2016-01-01

    Concentration of uranium was determined in aquatic plants and substrate (sediment or water) of fresh water ecosystem on and around uranium mill tailings pond at Jaduguda, India. Aquatic plant/substrate concentration ratios (CRs) of uranium were estimated for different sites on and around the uranium mill tailings disposal area. These sites include upstream and downstream side of surface water sources carrying the treated tailings effluent, a small pond inside tailings disposal area and residual water of this area. Three types of plant groups were investigated namely algae (filamentous and non-filamentous), other free floating & water submerged and sediment rooted plants. Wide variability in concentration ratio was observed for different groups of plants studied. The filamentous algae uranium concentration was significantly correlated with that of water (r=0.86, p<0.003). For sediment rooted plants significant correlation was found between uranium concentration in plant and the substrate (r=0.88, p<0.001). Both for other free floating species and sediment rooted plants, uranium concentration was significantly correlated with Mn, Fe, and Ni concentration of plants (p<0.01). Filamentous algae, Jussiaea and Pistia owing to their high bioproductivity, biomass, uranium accumulation and concentration ratio can be useful for prospecting phytoremediation of stream carrying treated or untreated uranium mill tailings effluent. PMID:26360459

  20. Benthic aquatic ecosystems across the Permian-Triassic transition: record from biogenic structures in fluvial sandstones, central Transantarctic Mountains

    NASA Astrophysics Data System (ADS)

    Miller, M. F.

    2000-07-01

    The effect of the Permian extinction in communities inhabiting sandy stream bottoms can be evaluated using trace fossils as proxies for body fossils. Permian and Triassic sandstones exposed in the Beardmore and Shackleton Glacier areas (central Transantarctic Mountains) were deposited in sandy braided streams and contain four types of trace fossils (vertical shafts and horizontal, bilobed and chevron traces). These traces were produced by a single type of animal that moved in the top 30 cm of sediment and dominated the benthic community. Evidence for a single producer includes similar size (diameter) of all traces and change within single specimens from one trace type to another. The animal was not affected by the Permian extinction event, as evidenced by its equal abundance within the Permian (Buckley Formation) and Triassic (Fremouw Formation) fluvial sandstones in the Beardmore Glacier area. Based on trace morphology and on domination of modern sandy river ecosystems by insects, the producer most likely was an insect, although its more precise identity is problematic. Although families of insects with modern aquatic burrowers are not known before the Jurassic, these trace fossils may show that these burrowers were present earlier than the insect body-fossil record suggests. Alternatively, archaic insect groups, many of which became extinct at the end-Permian and are known to have been aquatic but not infaunal, may have included some active burrowers that were unscathed by the Permian extinction.

  1. Remote Sensing of Arctic-Boreal Terrestrial and Freshwater Ecosystems - Recent Progress and Current and Future Challenges

    NASA Astrophysics Data System (ADS)

    Kasischke, E. S.; Goetz, S. J.

    2015-12-01

    NASA is in the process of starting its next major terrestrial field campaign, the Arctic-Boreal Vulnerability Experiment (ABoVE), with field-based research beginning in 2016 at sites in high northern latitude regions of western North America. In this presentation, we will review the research that is being planned for ABoVE that involves the use of remotely-sensed data, including the development of information products required by end users to assess the societal impacts of environmental change. These plans included taking advantage of recent advances in mapping of key surface and atmospheric characteristics using both airborne and spaceborne remote sensing data. We will also identify current and future challenges for the collection and analysis of additional data needed to assess key ecosystem changes, including the need for use of medium resolution optical and SAR data, and fine resolution optical data.

  2. Radiological bioconcentration factors for aquatic, terrestrial, and wetland ecosystems at the Savannah River site

    SciTech Connect

    Friday, G.P.; Cummins, C.L.; Schwartzman, A.L.

    1996-12-31

    Since the early 1950s, the Savannah River Site (SRS) released over 50 radionuclides into the environment while producing nuclear defense materials. These releases directly exposed aquatic and terrestrial biota to ionizing radiation from surface water, soil, and sediment, and also indirectly by the ingestion of items in the food chain. As part of new missions to develop waste management strategies and identify cost-effective environmental restoration options, knowledge concerning the uptake and distribution of these radionuclides is essential. This report compiles and summarizes site-specific bioconcentration factors for selected radionuclides released at SRS.

  3. RELATIONSHIPS AMONG EXCEEDENCES OF CHEMICAL CRITERIA OR GUIDELINES, THE RESULTS OF AMBIENT TOXICITY TESTS AND COMMUNITY METRICS IN AQUATIC ECOSYSTEMS (FINAL)

    EPA Science Inventory

    The EPA document, Relationships Among Exceedances of Chemical Criteria or Guidelines, the Results of Ambient Toxicity Tests, and Community Metrics in Aquatic Ecosystems, presents two studies where the three general approaches for the ecological assessment of contaminant ex...

  4. global research program: LTG2. Assess the potential impacts of global change on water quality and aquatic ecosystems in the US

    EPA Science Inventory

    Includes research on the effects of land use practices and climate change on terrestrial-aquatic linkages in the Willamette Basin Oregon and implications for water resources; assessment of the vulnerability of Pacific Coast estuarine ecosystems and population viability of key Pac...

  5. Hydrology and biogeochemistry of zero-order channels draining arctic hillslopes

    NASA Astrophysics Data System (ADS)

    Harms, T.; Godsey, S.; Longano, E.; Ludwig, S.; Risser, R. R.; Rushlow, C. R.

    2014-12-01

    Hydrologic flowpaths couple terrestrial and aquatic ecosystems and are responsive to changing climate in the arctic. However, significant uncertainty remains regarding the character and strength of links between terrestrial ecosystems and downstream aquatic ecosystems. We investigated spatial and temporal patterns in solute concentrations and stream discharge of zero-order channels, termed water tracks, draining hillslopes underlain by permafrost within the Kuparuk Basin of northern Alaska. Water tracks are ubiquitous features in this region, and may serve as a key regulator of elemental fluxes between terrestrial and aquatic ecosystems. Flow in water tracks was highly responsive to precipitation. Snowmelt dominated the annual hydrograph and in summer, rapid drying occurred between rain events. Despite widespread drying after snowmelt, isotopes of water indicated that snow-derived water contributed to flow in water tracks and the receiving river for several weeks beyond the snowmelt period, indicating capacity for storage of water in catchments even when thaw depth is shallow. In contrast, the snowmelt-derived flush of dissolved organic carbon, nitrogen, and phosphorus subsided with discharge, indicating limited supplies of these elements, or rapid uptake within catchments. After snowmelt, concentrations of nitrogen and phosphorus, the elements limiting primary production of terrestrial and aquatic ecosystems, respectively, remained low or undetectable in inorganic forms, except during large storms. Thus we expect that changes to the intensity or magnitude of precipitation will alter the availability and distribution of limiting nutrients within tundra catchments. Our observations of zero-order arctic channels indicate that changes in precipitation patterns and thaw dynamics may alter nutrient regimes of arctic ecosystems due to the key functions of nutrient delivery and distribution performed by water tracks. Strong nutrient limitation in terrestrial and aquatic

  6. Foundations of Physical Theory, I: Force and Energy. Physical Processes in Terrestrial and Aquatic Ecosystems, Fundamentals.

    ERIC Educational Resources Information Center

    Pearson, Nolan E.

    This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module is one of two units on the foundations of physical theory and the…

  7. Light and Sound: Evolutionary Aspects. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Roseman, Leonard D.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module is concerned with the exchange of energy between an organism and its environment in…

  8. Exploring Fish Diversity as a Determinant of Ecosystem Properties in Aquatic Food Webs

    ERIC Educational Resources Information Center

    Carey, Michael P.

    2009-01-01

    Dramatic biodiversity changes occurring globally from species loss and invasion have altered native food webs and ecosystem processes. My research objectives are to understand the consequences of fish diversity to freshwater systems by (1) examining the food web consequences of multiple top predators, (2) determining how biodiversity influences…

  9. Calculus-Integration. Physical Processes in Terrestrial and Aquatic Ecosystems, Applied Mathematics.

    ERIC Educational Resources Information Center

    Hertzberg, Richard C.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. The module is directed toward intermediate undergraduate students of the ecological sciences…

  10. Applications of the First Law to Ecological Systems. Physical Processes in Terrestrial and Aquatic Ecosystems, Thermodynamics.

    ERIC Educational Resources Information Center

    Stevenson, R. D.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This report describes concepts presented in another module called "The First Law of…

  11. Fluid Dynamics Applied to Streams. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Cowan, Christina E.

    This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module deals specifically with concepts that are basic to fluid flow and…

  12. Programmer's Guide for FFORM. Physical Processes in Terrestrial and Aquatic Ecosystems, Computer Programs and Graphics Capabilities.

    ERIC Educational Resources Information Center

    Anderson, Lougenia; Gales, Larry

    This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. FFORM is a portable format-free input subroutine package written in ANSI Fortran IV…

  13. Transpiration and Leaf Temperature. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Gates, David M.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This report introduces two models of the thermal energy budget of a leaf. Typical values for…

  14. Thermodynamics of Irreversible Processes. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Levin, Michael; Gallucci, V. F.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module describes the application of irreversible thermodynamics to biology. It begins with…

  15. Calculus - Differentiation. Physical Processes in Terrestrial and Aquatic Ecosystems, Applied Mathematics.

    ERIC Educational Resources Information Center

    Hertzberg, Richard C.

    This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This module is used to introduce the biology student to differential calculus, a…

  16. Soil Heat Flow. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

    ERIC Educational Resources Information Center

    Simpson, James R.

    These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. Soil heat flow and the resulting soil temperature distributions have ecological consequences…

  17. Plankton ecosystem functioning and nitrogen fluxes in the most oligotrophic waters of the Beaufort Sea, Arctic Ocean: a modeling study

    NASA Astrophysics Data System (ADS)

    Le Fouest, V.; Zakardjian, B.; Xie, H.; Raimbault, P.; Joux, F.; Babin, M.

    2012-10-01

    The Arctic Ocean (AO) undergoes profound changes of its physical and biotic environments due to climate change. The greater light exposure and stratification alter its plankton ecosystem structure, functioning and productivity promoting oligotrophy in some areas as the Beaufort Sea. A one-dimension (1-D) physical-biological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used (i) to infer the functioning and nitrogen fluxes within the summer plankton ecosystem and (ii) to assess the model sensitivity to key light-associated processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen (i.e. photoammonification process) was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. It contributed to ca. two-thirds and one-third of the simulated surface (0-10 m) and depth-integrated primary and bacterial production, respectively. The model also suggested that carbon to chlorophyll ratios for small (< 5 μm) phytoplankton (ca. 15-45 g g-1) lower than those commonly used in biogeochemical models applied to the AO were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional groups competition, nutrient recycling and primary production in poorly productive waters of the AO as they are expected to expand rapidly.

  18. Effects of increased snow cover on the rates and sources of ecosystem respiration from high arctic tundra

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Welker, J. M.; Cooper, E.; Xu, X.; Czimczik, C. I.

    2013-12-01

    A key driver of carbon (C) cycling in arctic ecosystems is the amount, onset and duration of snow cover. Arctic tundra is covered in snow for 8-10 months of the year, although spatial and internannual variability of snow cover is high. Anticipated changes in the amount and timing of snow cover as a consequence of climate warming and their implications for regional C budget and biogeochemistry are highly uncertain. Here, we investigated the effects of increased winter snow depth on the rates and sources of ecosystem respiration (Reco) of a polar semi-desert and mesic meadow at two long-term snowpack manipulation experiments in NW Greenland and Svalbard, Norway. We monitored Reco, the concentrations of CO2 in the soil pore space and their radiocarbon (14C) contents (as an age proxy) over the course of three summers in Greenland and one winter in Svalbard. Preliminary results show that wintertime Reco fluxes were 45% higher in areas of deep as compared to ambient snow. Summertime Reco fluxes were positively correlated to total water-year precipitation (summer rain plus winter snow). However, due to the shorter, snow-free vegetation period, cumulative summertime Reco fluxes under increased snow cover were reduced by up to -34.1×5.4% compared to the control. The mean age of soil CO2 was always older during both the winter- and summertime under increased snow cover. Similarly, the mean age of Reco was older under increased snowpack during the wintertime. However, summertime Reco was dominated by decomposition of younger C and plant respiration, and we found no effect of snow cover. Our results demonstrate the vulnerability of permafrost C to increasing snow cover and the strong potential to serve as a positive feedback to global climate change.

  19. Integration of Measurements and Models Across Spatial Scales for Improved Process Understanding in Arctic and Boreal Ecosystems

    NASA Astrophysics Data System (ADS)

    Wullschleger, S. D.; Collier, N.; Kumar, J.; Painter, S. L.; Thornton, P. E.; Wilson, C. J.

    2014-12-01

    Characterizing the spatial variability of properties and processes in Arctic and boreal landscapes is critical for gaining an understanding of ecosystem functioning and for parameterizing process-rich models that simulate feedbacks to a changing climate. However, large-scale models are often poorly informed by process studies and new approaches are needed if we are to better link field and laboratory investigations to climate models. A fundamental goal of the Next-Generation Ecosystem Experiments (NGEE Arctic) project is to accelerate improvements in climate prediction through close integration of field, laboratory, and modeling activities. Geomorphological units, including thaw lakes, drained thaw lake basins, and ice-rich polygonal ground provide the organizing framework for our integrated framework for the coastal plains of the North Slope of Alaska. Process studies and observations of hydrology, geomorphology, biogeochemistry, vegetation patterns, and energy exchange and their couplings are being conducted across nested scales to populate a modeling framework and to achieve a broader goal of optimally informing process representations in global-scale models. We investigate the soil thermal regimes and their control on local scale hydrology for sites near Barrow, Alaska, through simulations at sub-meter scale resolution for low-centered, high-centered and transition polygons. We use high-resolution LiDAR and high-fidelity simulations using several models to couple surface-subsurface processes. A central focus of this challenge is to advance process understanding and predicting the evolution of permafrost thaw, degradation (i.e., thermokarst), and disturbance, and their impact on topography in a warming world and how these changes control the availability of water for biogeochemical, ecological, and physical feedbacks to the climate system.

  20. Two years with extreme and little snowfall: effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Stiegler, Christian; Lund, Magnus; Røjle Christensen, Torben; Mastepanov, Mikhail; Lindroth, Anders

    2016-07-01

    Snow cover is one of the key factors controlling Arctic ecosystem functioning and productivity. In this study we assess the impact of strong variability in snow accumulation during 2 subsequent years (2013-2014) on the land-atmosphere interactions and surface energy exchange in two high-Arctic tundra ecosystems (wet fen and dry heath) in Zackenberg, Northeast Greenland. We observed that record-low snow cover during the winter 2012/2013 resulted in a strong response of the heath ecosystem towards low evaporative capacity and substantial surface heat loss by sensible heat fluxes (H) during the subsequent snowmelt period and growing season. Above-average snow accumulation during the winter 2013/2014 promoted summertime ground heat fluxes (G) and latent heat fluxes (LE) at the cost of H. At the fen ecosystem a more muted response of LE, H and G was observed in response to the variability in snow accumulation. Overall, the differences in flux partitioning and in the length of the snowmelt periods and growing seasons during the 2 years had a strong impact on the total accumulation of the surface energy balance components. We suggest that in a changing climate with higher temperature and more precipitation the surface energy balance of this high-Arctic tundra ecosystem may experience a further increase in the variability of energy accumulation, partitioning and redistribution.

  1. Historical and contemporary imagery to assess ecosystem change on the Arctic coastal plain of northern Alaska

    USGS Publications Warehouse

    Tape, Ken D.; Pearce, John M.; Walworth, Dennis; Meixell, Brandt W.; Fondell, Tom F.; Gustine, David D.; Flint, Paul L.; Hupp, Jerry W.; Schmutz, Joel A.; Ward, David H.

    2014-01-01

    In this report, we describe and make available a set of 61 georectified aerial images of the Arctic Coastal Plain (taken from 1948 to 2010) that were obtained by the USGS to inform research objectives of the USGS CAE Initiative. Here, we describe the origins, metadata, and public availability of these images that were obtained within four main study areas on the Arctic Coastal Plain: Teshekpuk Lake Special Area, Chipp River, the Colville River Delta, and locations along the Dalton Highway Corridor between the Brooks Range and Deadhorse. We also provide general descriptions of observable changes to the geomorphology of landscapes that are apparent by comparing historical and contemporary images. These landscape changes include altered river corridors, lake drying, coastal erosion, and new vegetation communities. All original and georectified images and metadata are available through the USGS Alaska Science Center Portal (search under ‘Project Name’ using title of this report) or by contacting ascweb@usgs.gov.

  2. Significant runoff exports of particulate nitrogen (PN) with large tropical storms: Implications of climate variability for watersheds and aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Inamdar, S. P.; Dhillon, G.

    2014-12-01

    Nitrogen (N) is an important nutrient that contributes to eutrophication of water bodies and plays a key role in various terrestrial and aquatic ecosystem processes. Thus, understanding the amounts and timing of N inputs from watersheds to aquatic ecosystems is critical. Most research to date has focused on the dissolved forms (< 0.45 micron) of N such as nitrate-N and organic N, which constitute a major portion of the N flux during baseflow and small to moderate storm events. The amounts of particulate N (PN > 0.45 micron) in runoff, can however, increase dramatically with large storms such as those associated with tropical depressions and hurricanes and can have a lasting impact on downstream aquatic systems. We determined the exports and storm-event patterns of PN for two (12 and 79 ha) intensively instrumented, headwater, forested, catchments located in the Piedmont Region of Maryland. Stream runoff sampling has been performed for baseflow and storm events since 2011 and has included numerous large tropical storms including Irene (2011) and Sandy (2012). Key questions that we address are: How significant is the PN flux, i.e., what proportion of the annual N is exported as PN during the large tropical events? How does PN export vary with storm magnitude? How do PN exports change with catchment scale? What are the temporal patterns of dissolved and particulate N species during the largest storms? Observations for tropical storm Irene (2011) revealed that in just 59 hours this storm contributed to one-third of the annual (2011) N flux from the 12 ha watershed and 87% of this N was in particulate form. A large portion of this particulate N is likely deposited in the fluvial network, especially in headwater reaches, and could potentially become bioavailable. Understanding these contributions from large events is especially important considering that climate-change scenarios indicate increased intensity of hurricanes and tropical storms and thus potentially a greater

  3. Removal of terrestrial dissolved organic carbon in aquatic ecosystems of a temperate river network.

    NASA Astrophysics Data System (ADS)

    Wollheim, W. M.; Stewart, R. J.; Aiken, G.; Butler, K. D.; Morse, N.; Salisbury, J.

    2015-12-01

    Surface waters play an important role in the global carbon balance. Dissolved organic carbon (DOC) fluxes are a major transfer of terrestrial carbon to river systems, and the net removal of terrestrial DOC in aquatic systems is poorly constrained. We used a combination of spatially distributed sampling of three DOC fractions, nitrate, and chloride in streams of different size throughout a river network and modeling to quantify the net removal of terrestrial DOC relative to other constituents during a summer base flow period. The approach was applied to the 400 km2 Ipswich River watershed, MA, USA. We found that aquatic reactivity of terrestrial DOC leading to net loss is low, closer to conservative chloride than to reactive nitrogen. Net removal of DOC occurred mainly from the hydrophobic organic acid fraction, while hydrophilic and transphilic acids showed no net change. Model fits were improved using the different DOC fractions than when using bulk DOC, indicating that partitioning of bulk DOC into different fractions is critical for understanding terrestrial DOC removal. These findings suggest that river systems may have only a modest ability to alter the amounts of terrestrial DOC delivered to coastal zones.

  4. Balanced nitrogen economy as a flexible strategy on yield stabilizing and quality of aquatic food crops in wetland ecosystem.

    PubMed

    Puste, A M; Sarkar, P K; Das, D K

    2005-12-01

    In wetland ecosystem, nitrogen along with other elements and its management is most imperative for the production of so many aquatic food, non-food and beneficial medicinal plants and for the improvement of soil and water characteristics. With great significant importance of INM (integrated nutrient management) as sources, emphasizing on management on nitrogen as a key element and its divergence, a case study was undertaken on such aquatic food crops (starch and protein-rich, most popular and remunerative) in the farmers' field of low-lying 'Tal' situation of New Alluvial Zone of Indian subtropics. The study was designed in factorial randomized block design, where, three important aquatic food crops (water chestnut (Trapa bispinosa Roxb.), makhana (Euryale ferox Salisb.) and water lily (Nymphaea spp.) as major factor and eleven combinations of organic and inorganic sources of nutrients as sub-factor was considered in the experiment. It revealed from the results that the production of fresh kernels or nuts of water chestnut (8.57 t ha(-1)), matured nut yield of makhana (3.06 t ha(-1)) and flower stalks of water-lily as vegetables (6.38 t ha(-1)) including its nutritional quality (starch, protein, sugar and minerals) was remarkably influenced with the application of both organic (neem oilcake @ 0.2 t ha(-1)) and inorganic sources (NPK @ 30:20:20 kg ha(-1) along with spraying of NPK @ 0.5% each over crop canopy at 20 days interval after transplanting) than the other INM combinations applied to the crops. Among the crops, highest WCYE (water chestnut yield equivalence) exhibited in makhana due to its high price of popped-form in the country, which is being exported to other countries at now. Sole application of both (organic and inorganic sources) with lower range did not produce any significant outcome from the study and exhibited lower value for all the crops. Besides production of food crops, INM also greatly influenced the soil and water characterization and it was

  5. Balanced nitrogen economy as a flexible strategy on yield stabilizing and quality of aquatic food crops in wetland ecosystem.

    PubMed

    Puste, A M; Sarkar, P K; Das, D K

    2005-09-01

    In wetland ecosystem, nitrogen along with other elements and its management is most imperative for the production of so many aquatic food, non-food and beneficial medicinal plants and for the improvement of soil and water characteristics. With great significant importance of INM (integrated nutrient management) as sources, emphasizing on management on nitrogen as a key element and its divergence, a case study was undertaken on such aquatic food crops (starch and protein-rich, most popular and remunerative) in the farmers' field of low-lying 'Tal' situation of New Alluvial Zone of Indian subtropics. The study was designed in factorial randomized block design, where, three important aquatic food crops (water chestnut (Trapa bispinosa Roxb.), makhana (Euryale ferox Salisb.) and water lily (Nymphaea spp.) as major factor and eleven combinations of organic and inorganic sources of nutrients as sub-factor was considered in the experiment. It revealed from the results that the production of fresh kernels or nuts of water chestnut (8.57 t ha(-1)), matured nut yield of makhana (3.06 t ha(-1)) and flower stalks of water-lily as vegetables (6.38 t ha(-1)) including its nutritional quality (starch, protein, sugar and minerals) was remarkably influenced with the application of both organic (neem oilcake @ 0.2 t ha(-1)) and inorganic sources (NPK @ 30:20:20 kg ha(-1) along with spraying of NPK @ 0.5% each over crop canopy at 20 days interval after transplanting) than the other INM combinations applied to the crops. Among the crops, highest WCYE (water chestnut yield equivalence) exhibited in makhana due to its high price of popped-form in the country, which is being exported to other countries at now. Sole application of both (organic and inorganic sources) with lower range did not produce any significant outcome from the study and exhibited lower value for all the crops. Besides production of food crops, INM also greatly influenced the soil and water characterization and it was

  6. Novel use of cavity ring-down spectroscopy to investigate aquatic carbon cycling from microbial to ecosystem scales.

    PubMed

    Maher, Damien T; Santos, Isaac R; Leuven, Jasper R F W; Oakes, Joanne M; Erler, Dirk V; Carvalho, Matheus C; Eyre, Bradley D

    2013-11-19

    Development of cavity ring-down spectroscopy (CRDS) has enabled real-time monitoring of carbon stable isotope ratios of carbon dioxide and methane in air. Here we demonstrate that CRDS can be adapted to assess aquatic carbon cycling processes from microbial to ecosystem scales. We first measured in situ isotopologue concentrations of dissolved CO2 ((12)CO2 and (13)CO2) and CH4 ((12)CH4 and (13)CH4) with CRDS via a closed loop gas equilibration device during a survey along an estuary and during a 40 h time series in a mangrove creek (ecosystem scale). A similar system was also connected to an in situ benthic chamber in a seagrass bed (community scale). Finally, a pulse-chase isotope enrichment experiment was conducted by measuring real-time release of (13)CO2 after addition of (13)C enriched phytoplankton to exposed intertidal sediments (microbial scale). Miller-Tans plots revealed complex transformation pathways and distinct isotopic source values of CO2 and CH4. Calculations of δ(13)C-DIC based on CRDS measured δ(13)C-CO2 and published fractionation factors were in excellent agreement with measured δ(13)C-DIC using isotope ratio mass spectroscopy (IRMS). The portable CRDS instrumentation used here can obtain real-time, high precision, continuous greenhouse gas data in lakes, rivers, estuaries and marine waters with less effort than conventional laboratory-based techniques. PMID:24131451

  7. Using paleolimnology to track the impacts of early Arctic peoples on freshwater ecosystems from southern Baffin Island, Nunavut

    NASA Astrophysics Data System (ADS)

    Michelutti, Neal; McCleary, Kathryn M.; Antoniades, Dermot; Sutherland, Patricia; Blais, Jules M.; Douglas, Marianne S. V.; Smol, John P.

    2013-09-01

    Paleolimnological approaches can be used to determine the ways in which past Arctic peoples have affected the ecosystems in which they live, and simultaneously to reconstruct the climate and other aspects of the environment that may have influenced local populations. Here we analyze sediment cores from seven ponds on the south-western coast of Baffin Island, Nunavut, in order to assess the impacts of early Arctic peoples on freshwater ecosystems. Prior to the historic Inuit occupation, the study area was extensively inhabited by Thule culture Inuit (ca 1200-1600 AD) and by an earlier Arctic group, the Dorset culture Palaeo-Eskimos (ca 500 BC-1500 AD) and their predecessors from as early as 2500 BC. The study ponds were selected to cover a gradient of the intensity of human activity in their catchments. The ecological impacts of early hunting societies can be detected using paleolimnology because the butchering of marine mammals released nutrients that eutrophied nearby ponds and left distinct geochemical signals in the sediments. The degree of eutrophication in the small freshwater ponds depended on the length of the occupation, as well as the amount and type of marine mammals taken as primary prey items (eg, whales, walrus, or seals). All sediment cores were AMS 14C dated to establish their chronologies, and analyzed for diatoms and stable isotopes of nitrogen (δ15N). Both diatoms and sedimentary δ15N have been previously demonstrated to respond sensitively to nutrient enrichment from Inuit whalers. Our δ15N and diatom data record nutrient enrichment in lakes surrounded by either long-term Thule or Dorset settlements. The Dorset sites that were the locations of periodic seasonal gatherings did not register any evidence of eutrophication in the nearby ponds, reflecting the shorter, less intensive nature of these occupations. Similarly, nearby control ponds with no evidence of significant human activity in their catchments showed little-to-no changes in δ15N

  8. Managing the effects of multiple stressors on aquatic ecosystems under water scarcity. The GLOBAQUA project.

    PubMed

    Navarro-Ortega, Alícia; Acuña, Vicenç; Bellin, Alberto; Burek, Peter; Cassiani, Giorgio; Choukr-Allah, Redouane; Dolédec, Sylvain; Elosegi, Arturo; Ferrari, Federico; Ginebreda, Antoni; Grathwohl, Peter; Jones, Colin; Rault, Philippe Ker; Kok, Kasper; Koundouri, Phoebe; Ludwig, Ralf Peter; Merz, Ralf; Milacic, Radmila; Muñoz, Isabel; Nikulin, Grigory; Paniconi, Claudio; Paunović, Momir; Petrovic, Mira; Sabater, Laia; Sabaterb, Sergi; Skoulikidis, Nikolaos Th; Slob, Adriaan; Teutsch, Georg; Voulvoulis, Nikolaos; Barceló, Damià

    2015-01-15

    Water scarcity is a serious environmental problem in many European regions, and will likely increase in the near future as a consequence of increased abstraction and climate change. Water scarcity exacerbates the effects of multiple stressors, and thus results in decreased water quality. It impacts river ecosystems, threatens the services they provide, and it will force managers and policy-makers to change their current practices. The EU-FP7 project GLOBAQUA aims at identifying the prevalence, interaction and linkages between stressors, and to assess their effects on the chemical and ecological status of freshwater ecosystems in order to improve water management practice and policies. GLOBAQUA assembles a multidisciplinary team of 21 European plus 2 non-European scientific institutions, as well as water authorities and river basin managers. The project includes experts in hydrology, chemistry, biology, geomorphology, modelling, socio-economics, governance science, knowledge brokerage, and policy advocacy. GLOBAQUA studies six river basins (Ebro, Adige, Sava, Evrotas, Anglian and Souss Massa) affected by water scarcity, and aims to answer the following questions: how does water scarcity interact with other existing stressors in the study river basins? How will these interactions change according to the different scenarios of future global change? Which will be the foreseeable consequences for river ecosystems? How will these in turn affect the services the ecosystems provide? How should management and policies be adapted to minimise the ecological, economic and societal consequences? These questions will be approached by combining data-mining, field- and laboratory-based research, and modelling. Here, we outline the general structure of the project and the activities to be conducted within the fourteen work-packages of GLOBAQUA. PMID:25005236

  9. Managing the effects of multiple stressors on aquatic ecosystems under water scarcity. The GLOBAQUA project

    PubMed Central

    Navarro-Ortega, Alícia; Acuña, Vicenç; Bellin, Alberto; Burek, Peter; Cassiani, Giorgio; Choukr-Allah, Redouane; Dolédec, Sylvain; Elosegi, Arturo; Ferrari, Federico; Ginebreda, Antoni; Grathwohl, Peter; Jones, Colin; Rault, Philippe Ker; Kok, Kasper; Koundouri, Phoebe; Ludwig, Ralf Peter; Merz, Ralf; Milacic, Radmila; Muñoz, Isabel; Nikulin, Grigory; Paniconi, Claudio; Paunović, Momir; Petrovic, Mira; Sabater, Laia; Sabaterb, Sergi; Skoulikidis, Nikolaos Th.; Slob, Adriaan; Teutsch, Georg; Voulvoulis, Nikolaos; Barceló, Damià

    2015-01-01

    Water scarcity is a serious environmental problem in many European regions, and will likely increase in the near future as a consequence of increased abstraction and climate change. Water scarcity exacerbates the effects of multiple stressors, and thus results in decreased water quality. It impacts river ecosystems, threatens the services they provide, and it will force managers and policy-makers to change their current practices. The EU-FP7 project GLOBAQUA aims at identifying the prevalence, interaction and linkages between stressors, and to assess their effects on the chemical and ecological status of freshwater ecosystems in order to improve water management practice and policies. GLOBAQUA assembles a multidisciplinary team of 21 European plus 2 non-European scientific institutions, as well as water authorities and river basin managers. The project includes experts in hydrology, chemistry, biology, geomorphology, modelling, socio-economics, governance science, knowledge brokerage, and policy advocacy. GLOBAQUA studies six river basins (Ebro, Adige, Sava, Evrotas, Anglian and Souss Massa) affected by water scarcity, and aims to answer the following questions: how does water scarcity interact with other existing stressors in the study river basins? How will these interactions change according to the different scenarios of future global change? Which will be the foreseeable consequences for river ecosystems? How will these in turn affect the services the ecosystems provide? How should management and policies be adapted to minimise the ecological, economic and societal consequences? These questions will be approached by combining data-mining, field- and laboratory-based research, and modelling. Here, we outline the general structure of the project and the activities to be conducted within the fourteen work-packages of GLOBAQUA. PMID:25005236

  10. Effects of municipal wastewater on aquatic ecosystem structure and function in the receiving stream.

    PubMed

    Englert, Dominic; Zubrod, Jochen P; Schulz, Ralf; Bundschuh, Mirco

    2013-06-01

    During recent years, increasing incidences of summer droughts - likely driven by climate change - reduced the dilution potential of low-order streams for secondary treated wastewater also in temperate Europe. Despite the potential risks to ecosystem integrity, there is a paucity of knowledge regarding the effects of different wastewater dilution potentials on ecosystem functions. The present study investigated the implications of secondary treated wastewater released into a third-order stream (Queich, southwest Germany) during a season with low dilution potential (summer; ~90% wastewater) as compared to a season with high dilution potential (winter; ~35% wastewater) in terms of leaf litter decomposition and macroinvertebrate communities. Adverse effects in macroinvertebrate mediated leaf mass loss (~65%), gammarids' feeding rate (~80%), leaf associated fungal biomass (>40%) and shifts in macroinvertebrate community structure were apparent up to 100 and 300 m (partially 500 m) downstream of the wastewater treatment plant effluent during winter and summer, respectively. In addition, a Gammarus fossarum laboratory feeding trial demonstrated the potential of powdered activated carbon to reduce the ecotoxicity of released wastewater. These results urge the development and evaluation of adequate management strategies, e.g. the application of advanced wastewater treatment technologies, to protect the integrity of freshwater ecosystems, which is required by the European Water Framework Directive - also considering decreasing dilution potential of streams as projected by climate change scenarios. PMID:23562693

  11. Processes influencing chemical biomagnification and trophic magnification factors in aquatic ecosystems: Implications for chemical hazard and risk assessment.

    PubMed

    Mackay, Donald; Celsie, Alena K D; Arnot, Jon A; Powell, David E

    2016-07-01

    Bioconcentration factors (BCFs) and bioaccumulation factors (BAFs) are widely used in scientific and regulatory programs to assess chemical hazards. There is increasing interest in also using biomagnification factors (BMFs) and trophic magnification factors (TMFs) for this purpose, especially for highly hydrophobic substances that may reach high concentrations in predatory species that occupy high trophic level positions in ecosystems. Measurements of TMFs in specific ecosystems can provide invaluable confirmation that biomagnification or biodilution has occurred across food webs, but their use in a regulatory context can be controversial because of uncertainties related to the reliability of measurements and their regulatory interpretation. The objective of this study is to explore some of the recognized uncertainties and dependencies in field BMFs and TMFs. This is accomplished by compiling a set of three simple food web models (pelagic, demersal and combined pelagic-demersal) consisting of up to seven species to simulate field BMFs and TMFs and to explore their dependences on hydrophobicity (expressed as log KOW), rates of biotransformation and growth, sediment-water fugacity ratios, and extent of food web omnivory and issues that arise when chemical concentration gradients exist in aquatic ecosystems. It is shown that empirical TMFs can be highly sensitive to these factors, thus the use of TMFs in a regulatory context must recognize these sensitivities. It is suggested that simple but realistic evaluative food web models could be used to extend BCF and BAF assessments to include BMFs and TMFs, thus providing a tool to address bioaccumulation hazard and the potential risk of exposures to elevated chemical concentrations in organisms at high trophic levels. PMID:27038905

  12. Cyanobacteria and Cyanotoxins: From Impacts on Aquatic Ecosystems and Human Health to Anticarcinogenic Effects

    PubMed Central

    Zanchett, Giliane; Oliveira-Filho, Eduardo C.

    2013-01-01

    Cyanobacteria or blue-green algae are among the pioneer organisms of planet Earth. They developed an efficient photosynthetic capacity and played a significant role in the evolution of the early atmosphere. Essential for the development and evolution of species, they proliferate easily in aquatic environments, primarily due to human activities. Eutrophic environments are conducive to the appearance of cyanobacterial blooms that not only affect water quality, but also produce highly toxic metabolites. Poisoning and serious chronic effects in humans, such as cancer, have been described. On the other hand, many cyanobacterial genera have been studied for their toxins with anticancer potential in human cell lines, generating promising results for future research toward controlling human adenocarcinomas. This review presents the knowledge that has evolved on the topic of toxins produced by cyanobacteria, ranging from their negative impacts to their benefits. PMID:24152991

  13. Cyanobacteria and cyanotoxins: from impacts on aquatic ecosystems and human health to anticarcinogenic effects.

    PubMed

    Zanchett, Giliane; Oliveira-Filho, Eduardo C

    2013-10-01

    Cyanobacteria or blue-green algae are among the pioneer organisms of planet Earth. They developed an efficient photosynthetic capacity and played a significant role in the evolution of the early atmosphere. Essential for the development and evolution of species, they proliferate easily in aquatic environments, primarily due to human activities. Eutrophic environments are conducive to the appearance of cyanobacterial blooms that not only affect water quality, but also produce highly toxic metabolites. Poisoning and serious chronic effects in humans, such as cancer, have been described. On the other hand, many cyanobacterial genera have been studied for their toxins with anticancer potential in human cell lines, generating promising results for future research toward controlling human adenocarcinomas. This review presents the knowledge that has evolved on the topic of toxins produced by cyanobacteria, ranging from their negative impacts to their benefits. PMID:24152991

  14. Distribution and bioavailability of ceria nanoparticles in an aquatic ecosystem model.

    PubMed

    Zhang, Peng; He, Xiao; Ma, Yuhui; Lu, Kai; Zhao, Yuliang; Zhang, Zhiyong

    2012-10-01

    Along with the increasing utilization of engineered nanoparticles, there is a growing concern for the potential environmental and health effects of exposure to these newly designed materials. Understanding the behavior of nanoparticles in the environment is a basic need. The present study aims to investigate the distribution and fate of ceria nanoparticles in an aquatic system model which consists of sediments, water, hornworts, fish and snails, using a radiotracer technique. Concentrations of ceria in the samples at regular time intervals were measured. Ceria nanoparticles were readily removed from the water column and partitioned between different organisms. Both snail and fish have fast absorption and clearance abilities. Hornwort has the highest bioaccumulation factors. At the end of the experiment, sediments accumulated most of the nanoparticles with a recovery of 75.7 ± 27.3% of total ceria nanoparticles, suggesting that sediments are major sinks of ceria nanoparticles. PMID:22694776

  15. Radiological bioconcentration factors for aquatic, terrestrial, and wetland ecosystems at the Savannah River Site

    SciTech Connect

    Cummins, C.L.

    1994-09-01

    As a result of operations at the Savannah River Site (SRS), over 50 radionuclides have been released to the atmosphere and to onsite streams and seepage basins. Now, many of these radionuclides are available to aquatic and/or terrestrial organisms for uptake and cycling through the food chain. Knowledge about the uptake and cycling of these radionuclides is now crucial in evaluating waste management and clean-up alternatives for the site. Numerous studies have been conducted at the SRS over the past forty years to study the uptake and distribution of radionuclides in the Savannah River Site environment. In many instances, bioconcentration factors have been calculated to quantify the uptake of a radionuclide by an organism from the surrounding medium (i.e., soil or water). In the past, it has been common practice to use bioconcentration factors from the literature because site-specific data were not readily available. However, because of the variability of bioconcentration factors due to experimental or environmental conditions, site-specific data should be used when available. This report compiles and summarizes site-specific bioconcentration factors for selected radionuclides released at the Savannah River Site (SRS). An extensive literature search yielded site-specific bioconcentration factors for cesium, strontium, cobalt, plutonium, americium, curium, and tritium. These eight radionuclides have been the primary radionuclides studied at SRS because of their long half lives or because they are major contributors to radiological dose from exposure. For most radionuclides, it was determined that the site-specific bioconcentration factors were higher than those reported in literature. This report also summarizes some conditions that affect radionuclide bioavailability to and bioconcentration by aquatic and terrestrial organisms.

  16. Carbon and nitrogen isotope studies in an arctic ecosystem. Final report

    SciTech Connect

    Schell, D.M.

    1994-06-01

    The dynamics of carbon fixation and storage in tundra soils has received considerable attention with respect to global carbon cycling. Recent findings by investigators using chamber measurements of fixation/respiration rates in arctic tundra have led to the conclusion that tundra is no longer storing carbon but is instead a source of carbon dioxide to the atmosphere. The author has sought to test these conclusions and to determine methods by which the long-term accumulation or loss of carbon in tundra can be determined. Little is known, however, of the processes that control storage and the current rates of carbon fixation and peat formation in arctic Alaska. This project focused on several aspects of carbon dynamics and the roles of decomposition and herbivory at the DOE research site at Imnavait Creek, Alaska. Through the use of natural abundance stable and radioisotope techniques, several conclusions emerged. Peat carbon continues to accumulate in wetter areas of foothill valleys and on the coastal plain of arctic Alaska. Radiocarbon profiles of bomb {sup 14}C were used to date layers of vegetation and litter to obtain decomposition rates and to extrapolate these values to intersection with the permafrost horizon where further decomposition is assumed to cease. Carbon storage in riparian moss at Imnavait Creek was estimated at 3 g C/m{sup 2}-yr. Profiles of {sup 137}Cs closely matched those of {sup 14}C and may provide a more expeditious means of assessing recent carbon accumulation rates in tundra. Carbon and nitrogen stable isotope ratios in tundra vegetation vary markedly over hydrologic gradients in apparent response to changing growth rates and sources of nitrogenous nutrients. Within a taxon, {delta}{sup 15}N values varied by several {per_thousand} over a tens of meters distance.

  17. Growing season fluxes and sources of CO2 and CH4 in high arctic ecosystems, NW Greenland

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Seibt, U.; Stills, A. K.; Xu, X.; Lindsey, D. S.; Welker, J. M.; Czimczik, C. I.

    2010-12-01

    Arctic tundra soils store vast amounts of organic carbon. Understanding how rapidly this pool can be mineralized as a consequence of warming and changes in the magnitude and timing of precipitation is a major uncertainty in predicting future levels of carbon dioxide in the atmosphere. We quantified the magnitudes and patterns of ecosystem-atmosphere fluxes of carbon dioxide (CO2) and methane (CH4) from polar semi-desert landscapes in NW Greenland. The measurements were undertaken from May to August 2010 at a multi-factorial, long-term climate change experiment started in 2003. In each treatment, fluxes were monitored from vegetated and barren soils. The experimental treatments consist of +2oC warming (T1), +4oC warming (T2), +50% summer precipitation (W), +4oC × +50% summer precipitation (T2W), and control (C). We used radiocarbon analysis to investigate the sources of carbon contributing to ecosystem carbon respiration under current and future climate conditions. Net ecosystem exchange (NEE) of CO2 and CH4 was measured continuously from four clear, automated chambers using cavity ring-down spectroscopy (Picarro 1301) under ambient and under conditions of high warming and added summer water (T2W). In all treatments, ecosystem respiration (R) from opaque chambers and soil pore space CO2 concentrations from soil wells were monitored daily via infrared spectroscopy (LI-COR 800 & 840) and sampled monthly for radiocarbon analysis. NEE fluxes were higher in vegetated than in bare soils and showed a clear seasonal pattern: both C and T2W treatments were a source of CO2 to the atmosphere in the spring and a net CO2 sink during summer. During the summer, NEE fluxes from vegetated soil were up to 5 times higher in the T2W (-11 µmol m-2 s-1) than ambient conditions (~ - 2 µmol m-2 s-1). Bare soils were a net source of CO2 at all times. All plots were a net sink of CH4 and showed a maximum in mid summer (-3 µmol m-2 s-1) when soil moisture was at a minimum. In the T2W

  18. Mercury cycling in aquatic ecosystems and trophic state-related variables--implications from structural equation modeling.

    PubMed

    Pollman, Curtis D

    2014-11-15

    Structural equation modeling (SEM) provides a framework that can more properly handle complex variable interactions inherent in mercury cycling and its bioaccumulation compared to more traditional regression-based methods. SEM was applied to regional data sets for three different types of aquatic ecosystems within Florida, USA--lakes, streams, and the Everglades--to evaluate the underlying nature (i.e., indirect and direct) of the relationships between fish mercury concentrations and trophic state related variables such as nutrients, dissolved organic carbon (DOC), sulfate, and alkalinity. The modeling results indicated some differences in key variable relationships--for example, the effect of nutrients on fish mercury in lakes and streams was uniformly negative through direct and indirect pathways consistent with biodilution or eutrophication-associated effects on food web structure. Somewhat surprisingly, however, was that total phosphorus did not serve as a meaningful variable in the Everglades model, apparently because its effects were masked or secondary to the effects of DOC. What is perhaps a more important result were two key similarities across the three systems. First, the modeling clearly indicates that the dominant influence on fish tissue mercury concentrations in all three systems is related to variations in the methylmercury signal. Second, the modeling demonstrated that the effect of DOC on fish mercury concentrations was exerted through multiple and antagonistic pathways, including facilitated transport of total mercury and methylmercury, enhanced rates of methylation, and limitations imposed on bioavailability. Indeed, while the individual DOC pathways in the models were all highly significant (generally p<0.001), the net effect of DOC in each model was greatly reduced or insignificant. These results can help explain contradictory results obtained previously by other researchers in other systems, and illustrate the importance of SEM as a modeling

  19. C.E.B.A.S. mini module: Test results of an artificial (man-made) aquatic ecosystem

    NASA Astrophysics Data System (ADS)

    Blüm, V.; Kreuzberg, K.; Stretzke, E.

    1994-11-01

    The original Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) is a long-term multi-generation research facility for experiments with aquatic animals and plants in a space station the development of which is surrounded by a large international scientific program. In addition, a miniaturized laboratory prototype, the C.E.B.A.S. MINI MODULE, with a total volume of about 10 - 12 liters for a Spacelab middeck locker was developed and a first version was tested successfully for two weeks with a population of fishes (Xiphophorus helleri) in the animal tank and a Ceratophyllum spec. in the illuminated higher plant growth chamber. The water recycling system consisted of a bacteria filter and a mechanical filter and the silastic tubing gas exchanger was separated by valves for the utilization in emergency cases only. Data were collected with the acquisition module of the original C.E.B.A.S. process control system. In addition, an optimized version was tested for 7 weeks with fishes and plants and thereafter with fish and with plants only for 2 and 1 weeks, resp.. The paper presents the relevant water parameters (e. g., pH, pressure, temperature, oxygen saturation, flow rate, ion concentrations) during the test period as well as morphological and physiological data of the enclosed animals and plants. On the basis of the given results the possible role of the C.E.B.A.S. system as a scientific tool in artificial ecosystem research and for the development of a combined animal-plant intensive aquaculture system and its utilization in bioregenerative life support is discussed.

  20. Environmental effects of dredging: Trophic transfer and biomagnification potential of contaminants in aquatic ecosystems. Technical notes

    SciTech Connect

    Dillon, T.M.; Suedel, B.C.; Peddicord, R.K.; Clifford, P.A.; Boraczek, J.A.

    1995-01-01

    The terms bioconcentration, bioaccumulation, biomagnification, trophic transfer, and trophic transfer coefficient are defined to avoid confusion, as they have been used inconsistently throughout the literature (Dallinger and others 1987). Bioconcentration is the uptake of a contaminant by aquatic organisms where water is the sole containment source. Bioaccumulation is the uptake of a contaminent from both water and dietary sources. Biomagnification refers to the processes of both bioconcentration and bioaccumulation that result in increased tissue concentrations of a contaminant as it passes through two or more trophic levels (Macek, Petrocelli, and Sleight 1979). Trophic transfer is defined as the transport of contaminants between two trophic levels (that is, prey to predator) (Swartz and Lee 1980). Trophic transfer coefficient (FTC) is the concentration of contaminant in consumer tissue divided by the concentration of contaminant in food sources (that is, preceding trophic level). A TTC is an approximate measure of the potential for a contaminant to biomagnify. Biomagnification occurs when concentrations of a material increase between two or more trophic levels (that is, TTC>1) and is a sub- set of trophic transfer, which refers to any movement of a material between trophic levels (that is, TTC can be greater than or less than 1). If trophic transfer is determined to be substantially >1, biomagnification is said to occur. If a TTC value is <1%, biomagnification is judged not to take place.

  1. Environmental control of diatom community size structure varies across aquatic ecosystems

    PubMed Central

    Finkel, Zoe V.; Vaillancourt, Colin Jacob; Irwin, Andrew J.; Reavie, Euan D.; Smol, John P.

    2009-01-01

    Changes in the size structure of photoautotrophs influence food web structure and the biogeochemical cycling of carbon. Decreases in the median size of diatoms within communities, in concert with climate warming and water column stratification, have been observed over the Cenozoic in the ocean and over the last 50 years in Lake Tahoe. Decreases in the proportion of larger plankton are frequently observed in response to reduced concentrations of limiting nutrients in marine systems and large stratified lakes. By contrast, we show a decrease in the median size of planktonic diatoms in response to higher nutrient concentrations in a set of intermediate-sized alkaline lakes. Climate-induced increases in the frequency, duration and strength of water column stratification may select smaller planktonic species in the ocean and larger lakes owing to a reduction in nutrient availability and sinking rates, while light limitation, stimulated by nutrient eutrophication and high chlorophyll concentrations, may select smaller species within a community owing to their high light absorption efficiencies and lower sinking rates. The relative importance of different physiological and ecological rates and processes on the size structure of communities varies in different aquatic systems owing to varying combinations of abiotic and biotic constraints. PMID:19203916

  2. Bioaccumulation of PCBs in aquatic biota from a tidal freshwater marsh ecosystem.

    PubMed

    Crimmins, B S; Brown, P Doelling; Kelso, D P; Foster, G D

    2002-05-01

    Water, sediments, and aquatic biota were sampled in a tidal river-marsh on the Potomac River near Washington, DC (USA) to assess baseline concentrations of polychlorinated biphenyls (PCBs) and bioaccumulation in finish species. The mean sediment total-PCB concentration in the wetland was 50 ng/g dry weight, and mean concentrations in biota ranged from 150 ng/g to 450 ng/g wet weight. The highest PCB concentrations were observed in channel catfish. The median biota-sediment accumulation factor (BSAF) estimated in all finfish species for total-PCBs was 2.9. However, some of the individual and co-eluting PCB congeners had median BSAFs that were substantially greater (e.g., congener numbers 42, 74, 182/187/128, and 171) or lower (e.g., congener numbers 18/15, 45, 185, and 208) than the total-PCB average. Apparent bioaccumulation factors (biota/water PCB concentration ratios) for PCB congeners showed a parabolic relation with n-octanol/water partition coefficients, confirming some previous investigations. There was no clear trend between apparent bioaccumulation factors and trophic level. Organic-carbon-normalized sediment distribution constants (sediment/water PCB concentration ratios) were linearly related to the apparent bioaccumulation factors for all the finfish species investigated. PMID:11994779

  3. The environmental costs of mountaintop mining valley fill operations for aquatic ecosystems of the Central Appalachians.

    PubMed

    Bernhardt, Emily S; Palmer, Margaret A

    2011-03-01

    Southern Appalachian forests are recognized as a biodiversity hot spot of global significance, particularly for endemic aquatic salamanders and mussels. The dominant driver of land-cover and land-use change in this region is surface mining, with an ever-increasing proportion occurring as mountaintop mining with valley fill operations (MTVF). In MTVF, seams of coal are exposed using explosives, and the resulting noncoal overburden is pushed into adjacent valleys to facilitate coal extraction. To date, MTVF throughout the Appalachians have converted 1.1 million hectares of forest to surface mines and buried more than 2,000 km of stream channel beneath mining overburden. The impacts of these lost forests and buried streams are propagated throughout the river networks of the region as the resulting sediment and chemical pollutants are transmitted downstream. There is, to date, no evidence to suggest that the extensive chemical and hydrologic alterations of streams by MTVF can be offset or reversed by currently required reclamation and mitigation practices. PMID:21449964

  4. An adaptive, comprehensive monitoring strategy for chemicals of emerging concern (CECs) in California's Aquatic Ecosystems.

    PubMed

    Maruya, Keith A; Schlenk, Daniel; Anderson, Paul D; Denslow, Nancy D; Drewes, Jörg E; Olivieri, Adam W; Scott, Geoffrey I; Snyder, Shane A

    2014-01-01

    A scientific advisory panel was convened by the State of California to recommend monitoring for chemicals of emerging concern (CECs) in aquatic systems that receive discharge of municipal wastewater treatment plant (WWTP) effluent and stormwater runoff. The panel developed a risk-based screening framework that considered environmental sources and fate of CECs observed in receiving waters across the State. Using existing occurrence and risk threshold data in water, sediment, and biological tissue, the panel applied the framework to identify a priority list of CECs for initial monitoring in three representative receiving water scenarios. The initial screening list of 16 CECs identified by the panel included consumer and commercial chemicals, flame retardants, pesticides, pharmaceuticals and personal care products, and natural hormones. The panel designed an iterative, phased strategy with interpretive guidelines that direct and update management actions commensurate with potential risk identified using the risk-based framework and monitoring data. Because of the ever-changing nature of chemical use, technology, and management practices, the panel offered recommendations to improve CEC monitoring, including development of bioanalytical screening methods whose responses integrate exposure to complex mixtures and that can be linked to higher-order effects; development or refinement of models that predict the input, fate, and effects of future chemicals; and filling of key data gaps on CEC occurrence and toxicity. Finally, the panel stressed the need for adaptive management, allowing for future review of, and if warranted, modifications to the strategy to incorporate the latest science available to the water resources community. PMID:24129960

  5. The Economic Value of the Greater Montreal Blue Network (Quebec, Canada): A Contingent Choice Study Using Real Projects to Estimate Non-Market Aquatic Ecosystem Services Benefits.

    PubMed

    Poder, Thomas G; Dupras, Jérôme; Fetue Ndefo, Franck; He, Jie

    2016-01-01

    This study used a contingent choice method to determine the economic value of improving various ecosystem services (ESs) of the Blue Network of Greater Montreal (Quebec, Canada). Three real projects were used and the evaluation focused on six ESs that are related to freshwater aquatic ecosystems: biodiversity, water quality, carbon sequestration, recreational activities, landscape aesthetics and education services. We also estimated the value associated with the superficies of restored sites. We calculated the monetary value that a household would be willing to pay for each additional qualitative or quantitative unit of different ESs, and these marginal values range from $0.11 to $15.39 per household per unit. Thus, under certain assumptions, we determined the monetary values that all Quebec households wo