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Sample records for abstract seagrass beds

  1. Keeping tabs on seagrass beds

    SciTech Connect

    Kuhl, D.E.; Sargent, F.J.; Leary, T.J.

    1997-06-01

    Seagrasses form the foundation of complex, fragile communities that include marine and estuarine animals, especially larval and juvenile fish, providing critical shelter and sustenance. Seagrasses also have a role in providing habitat for waterfowl, marine turtles and manimals. In addition, seagrasses improve water quality by stabilizing mobile sediments and converting some pollutants into plant biomass. The issue of propeller scarring or propeller dredging in seagrass beds has received much attention since 1990. The scarring of seagrass results from personal watercraft. Heightened interest has instigated numerous monitoring and mapping projects on propeller scarring and regrowth characteristics within seagrasses. The study areas selected for this paper are located within Tampa Bay, Florida. Specifically, they are Shell Island and Miquel Bay. Spatial monitoring for the extent of seagrass scarring in the Tampa Bay region was conducted in two ways, a regional (general) approach and a site specific (detailed) approach. Regional monitoring assessed the status of seagrass in Tampa Bay and identified {open_quote}hot spots{close_quote}. After identifying {open_quote}hot spots{close_quote}, boat surveys were used to confirm or deny the initial assessment. This poster involves the design of a propeller scarring monitoring program using several methods: Hi8 video, digital cameras, film cameras, and differential GPS combined with Arcview. A pilot program to evaluate the adequacy of these monitoring devices and the recommendation of specific actions in areas of severe propeller scarring will be presented.

  2. Carbon Sequestration Within Northeast Pacific Seagrass Beds

    NASA Astrophysics Data System (ADS)

    O'Donnell, B. C.; Hill, T. M.; Gaylord, B.; Kroeker, K.; Sanford, E.; Ward, M.; Ninokawa, A. T.; Susner, G. M.; Calhoun, H. W.

    2016-12-01

    There are clear knowledge gaps in understanding carbon sequestration of seagrass beds in temperate systems. Our ongoing research aims to understand the long and short-term storage of carbon within Zostera marina seagrass environments in Northern California. The objective of this sedimentological research is to quantify the storage of carbon (by weight percent and elemental mass) in seagrass sediments compared to adjacent (non-seagrass) sediments. Our project has targeted seagrass beds of various sizes and shoot densities, as well as seasonal differences, in two estuaries (Tomales Bay and Bodega Harbor, CA) by analysis of push cores. Cores were complemented by estuarine geochemical data from automated sensor deployments (for pH, pCO2, O2, temperature, salinity) and discrete water sampling (pH and alkalinity) with biomass investigations. Push core sediments were analyzed for grain size, carbonate content, total organic matter, and microfossil presence. Results from sedimentological data show that sediment grain size is closely related to carbon burial; seagrass beds that are dominated by fine, mud-sized particles are composed of 7-10% organic material, whereas coarser sediments dominated by sand range from 1-5% organic material. This study highlights the utility of including grain size analyses in all coastal vegetation carbon burial studies. Future work within this project will aim to explore the relationship between seasonal variability and rate of carbon sequestration to further the understanding of carbon sequestration of seagrass on the California Coast.

  3. SULFUR CYCLING IN THALASSIA TESTUDINUM SEAGRASS BED SEDIMENTS

    EPA Science Inventory

    Quarles, Robert L., Jessica A. Rivord and Richard Devereux. In press. Sulfur Cycling in Thalassia testudinum Seagrass Bed Sediments (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems of the Gulf of Mexico and S...

  4. SULFUR CYCLING IN THALASSIA TESTUDINUM SEAGRASS BED SEDIMENTS

    EPA Science Inventory

    Quarles, Robert L., Jessica A. Rivord and Richard Devereux. In press. Sulfur Cycling in Thalassia testudinum Seagrass Bed Sediments (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems of the Gulf of Mexico and S...

  5. Differences in macrofaunal and seagrass assemblages in seagrass beds with and without seaweed farms

    NASA Astrophysics Data System (ADS)

    Eklöf, J. S.; de la Torre Castro, M.; Adelsköld, L.; Jiddawi, N. S.; Kautsky, N.

    2005-05-01

    Since it was introduced to Zanzibar (Tanzania), seaweed farming has significantly contributed to local, socio-economic development. However, several investigations have shown impacts on the coastal environment near where the farms are located. As many seaweed farms are located on seagrass beds, there is a risk that seaweed farming could affect seagrass beds, and thereby disturb important ecosystem functions and the flow of ecological goods and services. This study compares characteristics of macrophytes (focusing on seagrasses), benthic macrofauna and sediment in seagrass beds, with and without seaweed farms, and a sand bank without vegetation in Chwaka Bay, Zanzibar. The results showed that seagrass beds underneath seaweed farms generally had less seagrass and macroalgae, finer sediment, lower sediment organic matter content and a reduced abundance and biomass of macrofauna, than seagrass beds without seaweed farms. Further, the macrofaunal community structure in seaweed farms showed more similarities to that on the sand bank than in the unfarmed seagrass beds. Most of the dissimilarity was attributable to Lucinidae (suspension-feeding bivalves), which were almost absent in the seaweed farms, resulting in the large difference in biomass between the seaweed farms and the unfarmed seagrass beds. When interpreted together with information from farmers, the observed pattern is believed to be caused by the seaweed farming activities. This indicates that more research is needed to establish the effects of seaweed farming on seagrass beds, and that more attention should be given to the location of farms and the choice of farming methods.

  6. Status and threats on seagrass beds using GIS in Vietnam

    NASA Astrophysics Data System (ADS)

    Luong, Cao Van; Thao, Nguyen Van; Komatsu, Teruhisa; Ve, Nguyen Dac; Tien, Dam Duc

    2012-10-01

    Seagrasses, marine flowering plants, are widely distributed along temperate and tropical coastlines of the world. Seagrasses have key ecological roles in coastal ecosystems and can form extensive meadows supporting high biodiversity. Till now, fourteen seagrass species belonging to four families were found in Vietnam: Halophila beccarii, H. decipiens, H. ovalis, H. minor, Thalassia hemprichii, Enhalus acoroides, Ruppia maritima, Halodule pinifolia, H. uninervis, Syringodium isoetifolium, Cymadocea rotundata, C. serrulata and Thalassodendron ciliatum. A total area of seagrass beds in Vietnam is estimated to be approximately 17000 ha by satellite images and GIS technology. In recent years, the distribution areas and densities of seagrass beds in Vietnam have been serious decreased compared with those 10-15 years ago. The decline level depended on the impacts by the natural process, the economical activities and the conservation awareness of local people. Thus, it is different at each coastal area. Generally speaking, the distribution areas and densities of seagrass beds were decreased by more than 50%. Seagrasses on tidal flats in some areas such as Quang Ninh, Hai Phong, Phu Quoc seem to be nearly lost. The distribution areas of seagrass beds in 2009 at Tam Giang-Cau Hai lagoon and Cua Dai estuary was decreased by 50-70% of those in early 1990s.

  7. Coupled Biogeochemical and Hydrodynamic Measurements over a Palauan Seagrass Bed: Can Seagrasses Mitigate Local Acidification Stress?

    NASA Astrophysics Data System (ADS)

    Hirsh, H.; Torres, W.; Shea, M.

    2016-02-01

    Interest in seagrass beds as a tool to locally mitigate ocean acidification is growing rapidly. Much of the interest in seagrasses is motivated by their root structure, which is able to sequester carbon over interannual and longer timescales. Far less is known about their biogeochemistry on shorter diel timescales, yet we know that diel cycle variation in CO2 chemistry on coral reefs can be quite substantial. Understanding short-term seagrass biogeochemistry is critical to evaluating if, and how, seagrasses may eventually be utilized to mitigate OA on coral reefs. We present the results of a high-resolution, 24-hour control volume experiment conducted in the Republic of Palau covering a 50m x 100m seagrass bed. Our dataset includes diel cycles of hydrodynamic (current profiles and turbulence), biogeochemical (pH, pCO2, TA, DIC, and O2), and environmental (temperature and salinity) parameters. We use these coupled hydrodynamic-biogeochemical measurements to estimate ecosystem metabolism and better quantify the capacity of seagrass to mitigate local acidification through the photosynthetic uptake of CO2. Combining our field observations with box model predictions allows us to gain better insight into the mechanisms that control seagrass metabolism and their ability to buffer CO2 for downstream corals.

  8. Biodiversity of seagrass bed in Balanan Resort - Baluran National Park

    NASA Astrophysics Data System (ADS)

    Soedarti, T.; Hariyanto, S.; Wedayanti, A.; Rahmawati, A. D.; Safitri, D. P.; Alificia, R. I.; Suwono

    2017-09-01

    Seagrass beds are flowering plants that live on the seabed. Seagrass provides a habitat for diverse flora and fauna, spawning ground, nursery ground, raising ground, and feeding ground. Balanan Resort - Baluran National Park has many beaches, such as Kajang Beach, Si Banjir Beach, Kakapa Beach, and Serondo Beach. This study was aimed to determine species composition, seagrass dominated, and the diversity index of seagrass and substrate in Resort Balanan - Baluran National Park. This research was carried out in Kajang Beach, Sibanjir Beach, Kakapa Beach, and Sirondo Beach from August to September 2015 using belt transect method, each transect consists of 15 plots (19 transects = 285 plots) and using the frame of 1x1 m. This research found seven genera and ten species : Cymodoce (C rotundata and C. serrulata), Syringodium (S. isoelifolium), Thallassodendron (T. ciliatum), Enhalus (E. acoroides) , Halodule (H. univernis and H. pinifolia), Halophila (H. ovalis and H. decipiens), and Thalassia (T. hemprichii). The diversity index of seagrass bed was moderate [H'=1.90] in Balanan Resort. The substrate of seagrass bed was mud, gravel, sand, clay sand and rubble in Balanan Resort. The dominance index was near zero [C = 0.194], that means no dominant species.

  9. Manatee grazing impacts on a mixed species seagrass bed

    USGS Publications Warehouse

    Lefebvre, Lynn W.; Provancha, Jane A.; Slone, Daniel H.; Kenworthy, W. Judson

    2017-01-01

    The endangered manatee Trichechus manatus is one of few large grazers in seagrass systems. To assess the long-term impacts of repeated grazing on seagrasses, we selected a study site within Kennedy Space Center in the northern Banana River, Brevard County, Florida, that was typically grazed by large numbers of manatees in spring. Two 13x13 m manatee exclosures and 2 paired open plots of equal size were established at the study site in October 1990. Shoot counts, biomass, and species composition of the co-dominant seagrass species, Syringodium filiforme and Halodule wrightii, were sampled 3 times per year in all 4 plots between October 1990 and October 1994. We used a Bayesian modelling approach, accounting for the influence of depth, to detect treatment (exclosed vs. open) effects. S. filiforme shoot counts, total biomass, and frequency of occurrence significantly increased in the exclosures. By July 1993, mean biomass values in the exclosures (167 g dry wt m-2) greatly exceeded those in the open plots (28 g dry wt m-2). H. wrightii decreased in the exclosures by 1994. Initially, both S. filiforme and H. wrightii responded positively to release from manatee grazing pressure. As S. filiforme continued to become denser in the exclosures, it gradually replaced H. wrightii. Our findings may be helpful to biologists and managers interested in predicting seagrass recovery and manatee carrying capacity of repeatedly grazed seagrass beds in areas of special significance to manatees and seagrass conservation.

  10. Microbial biomass and productivity in seagrass beds

    NASA Technical Reports Server (NTRS)

    Moriarty, D. J.; Boon, P. I.; Hansen, J. A.; Hunt, W. G.; Poiner, I. R.; Pollard, P. C.; Skyring, G. W.; White, D. C.

    1985-01-01

    Different methods for measuring the rates of processes mediated by bacteria in sediments and the rates of bacterial cell production have been compared. In addition, net production of the seagrass Zostera capricorni and bacterial production have been compared and some interrelationships with the nitrogen cycle discussed. Seagrass productivity was estimated by measuring the plastochrone interval using a leaf stapling technique. The average productivity over four seasons was 1.28 +/- 0.28 g C m-2 day-1 (mean +/- standard deviation, n = 4). Bacterial productivity was measured five times throughout a year using the rate of tritiated thymidine incorporated into DNA. Average values were 33 +/- 12 mg C m-2 day-1 for sediment and 23 +/- 4 for water column (n = 5). Spatial variability between samples was greater than seasonal variation for both seagrass productivity and bacterial productivity. On one occasion, bacterial productivity was measured using the rate of 32P incorporated into phospholipid. The values were comparable to those obtained with tritiated thymidine. The rate of sulfate reduction was 10 mmol SO4(-2) m-2 day-1. The rate of methanogenesis was low, being 5.6 mg CH4 produced m-2 day-1. A comparison of C flux measured using rates of sulfate reduction and DNA synthesis indicated that anaerobic processes were predominant in these sediments. An analysis of microbial biomass and community structure, using techniques of phospholipid analysis, showed that bacteria were predominant members of the microbial biomass and that of these, strictly anaerobic bacteria were the main components. Ammonia concentration in interstitial water varied from 23 to 71 micromoles. Estimates of the amount of ammonia required by seagrass showed that the ammonia would turn over about once per day. Rapid recycling of nitrogen by bacteria and bacterial grazers is probably important.

  11. Microbial biomass and productivity in seagrass beds.

    PubMed

    Moriarty, D J; Boon, P I; Hansen, J A; Hunt, W G; Poiner, I R; Pollard, P C; Skyring, G W; White, D C

    1985-01-01

    Different methods for measuring the rates of processes mediated by bacteria in sediments and the rates of bacterial cell production have been compared. In addition, net production of the seagrass Zostera capricorni and bacterial production have been compared and some interrelationships with the nitrogen cycle discussed. Seagrass productivity was estimated by measuring the plastochrone interval using a leaf stapling technique. The average productivity over four seasons was 1.28 +/- 0.28 g C m-2 day-1 (mean +/- standard deviation, n = 4). Bacterial productivity was measured five times throughout a year using the rate of tritiated thymidine incorporated into DNA. Average values were 33 +/- 12 mg C m-2 day-1 for sediment and 23 +/- 4 for water column (n = 5). Spatial variability between samples was greater than seasonal variation for both seagrass productivity and bacterial productivity. On one occasion, bacterial productivity was measured using the rate of 32P incorporated into phospholipid. The values were comparable to those obtained with tritiated thymidine. The rate of sulfate reduction was 10 mmol SO4(-2) m-2 day-1. The rate of methanogenesis was low, being 5.6 mg CH4 produced m-2 day-1. A comparison of C flux measured using rates of sulfate reduction and DNA synthesis indicated that anaerobic processes were predominant in these sediments. An analysis of microbial biomass and community structure, using techniques of phospholipid analysis, showed that bacteria were predominant members of the microbial biomass and that of these, strictly anaerobic bacteria were the main components. Ammonia concentration in interstitial water varied from 23 to 71 micromoles. Estimates of the amount of ammonia required by seagrass showed that the ammonia would turn over about once per day. Rapid recycling of nitrogen by bacteria and bacterial grazers is probably important.

  12. Microbial biomass and productivity in seagrass beds

    NASA Technical Reports Server (NTRS)

    Moriarty, D. J.; Boon, P. I.; Hansen, J. A.; Hunt, W. G.; Poiner, I. R.; Pollard, P. C.; Skyring, G. W.; White, D. C.

    1985-01-01

    Different methods for measuring the rates of processes mediated by bacteria in sediments and the rates of bacterial cell production have been compared. In addition, net production of the seagrass Zostera capricorni and bacterial production have been compared and some interrelationships with the nitrogen cycle discussed. Seagrass productivity was estimated by measuring the plastochrone interval using a leaf stapling technique. The average productivity over four seasons was 1.28 +/- 0.28 g C m-2 day-1 (mean +/- standard deviation, n = 4). Bacterial productivity was measured five times throughout a year using the rate of tritiated thymidine incorporated into DNA. Average values were 33 +/- 12 mg C m-2 day-1 for sediment and 23 +/- 4 for water column (n = 5). Spatial variability between samples was greater than seasonal variation for both seagrass productivity and bacterial productivity. On one occasion, bacterial productivity was measured using the rate of 32P incorporated into phospholipid. The values were comparable to those obtained with tritiated thymidine. The rate of sulfate reduction was 10 mmol SO4(-2) m-2 day-1. The rate of methanogenesis was low, being 5.6 mg CH4 produced m-2 day-1. A comparison of C flux measured using rates of sulfate reduction and DNA synthesis indicated that anaerobic processes were predominant in these sediments. An analysis of microbial biomass and community structure, using techniques of phospholipid analysis, showed that bacteria were predominant members of the microbial biomass and that of these, strictly anaerobic bacteria were the main components. Ammonia concentration in interstitial water varied from 23 to 71 micromoles. Estimates of the amount of ammonia required by seagrass showed that the ammonia would turn over about once per day. Rapid recycling of nitrogen by bacteria and bacterial grazers is probably important.

  13. Diurnal changes in pore water sulfide concentrations in the seagrass Thalassia testudinum beds: the effects of seagrasses on sulfide dynamics.

    PubMed

    Lee; Dunton

    2000-12-20

    The dynamics of the seagrass-sulfide interaction were examined in relation to diel changes in sediment pore water sulfide concentrations in Thalassia testudinum beds and adjacent bare areas in Corpus Christi Bay and lower Laguna Madre, Texas, USA, during July 1996. Pore water sulfide concentrations in seagrass beds were significantly higher than in adjacent bare areas and showed strong diurnal variations; levels significantly decreased during mid-day at shallow sediment depths (0-10 cm) containing high below-ground tissue biomass and surface area. In contrast, diurnal variations in sediment sulfide concentrations were absent in adjacent bare patches, and at deeper (>10 cm) sediment depths characterized by low below-ground plant biomass or when the grasses were experimentally shaded. These observations suggest that the mid-day depressions in sulfide levels are linked to the transport of photosynthetically produced oxygen to seagrass below-ground tissues that fuels sediment sulfide oxidation. Lower sulfide concentrations in bare areas are likely a result of low sulfate reduction rates due to low organic matter available for remineralization. Further, high reoxidation rates due to rapid exchange between anoxic pore water and oxic overlying water are probably stimulated in bare areas by higher current velocity on the sediment surface than in seagrass beds. The dynamics of pore water sulfides in seagrass beds suggest no toxic sulfide intrusion into below-ground tissues during photosynthetic periods and demonstrate that the sediment chemical environment is considerably modified by seagrasses. The reduced sediment sulfide levels in seagrass beds during photosynthetic periods will enhance seagrass production through reduced sulfide toxicity to seagrasses and sediment microorganisms related to the nutrient cycling.

  14. Simulation of seagrass bed mapping by satellite images based on the radiative transfer model

    NASA Astrophysics Data System (ADS)

    Sagawa, Tatsuyuki; Komatsu, Teruhisa

    2015-06-01

    Seagrass and seaweed beds play important roles in coastal marine ecosystems. They are food sources and habitats for many marine organisms, and influence the physical, chemical, and biological environment. They are sensitive to human impacts such as reclamation and pollution. Therefore, their management and preservation are necessary for a healthy coastal environment. Satellite remote sensing is a useful tool for mapping and monitoring seagrass beds. The efficiency of seagrass mapping, seagrass bed classification in particular, has been evaluated by mapping accuracy using an error matrix. However, mapping accuracies are influenced by coastal environments such as seawater transparency, bathymetry, and substrate type. Coastal management requires sufficient accuracy and an understanding of mapping limitations for monitoring coastal habitats including seagrass beds. Previous studies are mainly based on case studies in specific regions and seasons. Extensive data are required to generalise assessments of classification accuracy from case studies, which has proven difficult. This study aims to build a simulator based on a radiative transfer model to produce modelled satellite images and assess the visual detectability of seagrass beds under different transparencies and seagrass coverages, as well as to examine mapping limitations and classification accuracy. Our simulations led to the development of a model of water transparency and the mapping of depth limits and indicated the possibility for seagrass density mapping under certain ideal conditions. The results show that modelling satellite images is useful in evaluating the accuracy of classification and that establishing seagrass bed monitoring by remote sensing is a reliable tool.

  15. Seaweed beds support more juvenile reef fish than seagrass beds in a south-western Atlantic tropical seascape

    NASA Astrophysics Data System (ADS)

    Eggertsen, L.; Ferreira, C. E. L.; Fontoura, L.; Kautsky, N.; Gullström, M.; Berkström, C.

    2017-09-01

    Seascape connectivity is regarded essential for healthy reef fish communities in tropical shallow systems. A number of reef fish species use separate adult and nursery habitats, and hence contribute to nutrient and energy transfer between habitats. Seagrass beds and mangroves often constitute important nursery habitats, with high structural complexity and protection from predation. Here, we investigated if reef fish assemblages in the tropical south-western Atlantic demonstrate ontogenetic habitat connectivity and identify possible nurseries on three reef systems along the eastern Brazilian coast. Fish were surveyed in fore reef, back reef, Halodule wrightii seagrass beds and seaweed beds. Seagrass beds contained lower abundances and species richness of fish than expected, while Sargassum-dominated seaweed beds contained significantly more juveniles than all other habitats (average juvenile fish densities: 32.6 per 40 m2 in Sargassum beds, 11.2 per 40 m2 in back reef, 10.1 per 40 m2 in fore reef, and 5.04 per 40 m2 in seagrass beds), including several species that are found in the reef habitats as adults. Species that in other regions worldwide (e.g. the Caribbean) utilise seagrass beds as nursery habitats were here instead observed in Sargassum beds or back reef habitats. Coral cover was not correlated to adult fish distribution patterns; instead, type of turf was an important variable. Connectivity, and thus pathways of nutrient transfer, seems to function differently in east Brazil compared to many tropical regions. Sargassum-dominated beds might be more important as nurseries for a larger number of fish species than seagrass beds. Due to the low abundance of structurally complex seagrass beds we suggest that seaweed beds might influence adult reef fish abundances, being essential for several keystone species of reef fish in the tropical south-western Atlantic.

  16. Mapping seagrass beds and coral reefs in the coastal region of Vietnam using VNREDSAT-1 data

    NASA Astrophysics Data System (ADS)

    Lau, K. V.; Chen, C. F.; Nguyen, S. T.; Chen, C. R.; Tong Phuoc, H. S.; Nguyen, H. H.

    2015-12-01

    Seagrass beds and coral reefs are two important ecosystems in the coastal zone. They play an important role to protect and shelter various marine organisms. Both seagrass beds and coral reefs could prevent the coastline from erosion. While seagrass stabilizes sediments and acts as a biofilter, coral reefs can control carbon dioxide in the ocean water. Besides, seagrass also provides direct food for many fish and marine animals. Therefore, mapping seagrass beds and coral reefs is very important for coastal management and conservation. In May 2013, Vietnam launched the first satellite for earth observations, called Vietnam Natural Resources, Environment and Disaster Monitoring Satellite (VNREDSAT-1). It is a great opportunity for environmental monitoring in the country using the data from this satellite. The objective of this study is to use the VNREDSAT-1 data to map seagrass beds and coral reefs in the coastal region of Ninh Hai district, Ninh Thuan province, Vietnam, where the seagrass still remains in good a condition. We processed the VNREDSAT-1 image through four steps: (1) Atmospheric correction using Second Simulation of the Satellite Signal in the Solar Spectrum radiative transfer model (6S), (2) Sun glint removal by using Hedley method, (3) Water column correction using the depth-variant index (DII) proposed by Lyzenga, and (4) Image classification using the maximum likelihood algorithm. The mapping results verified with the ground reference data showed a good overall accuracy of 75% and Kappa coefficient of 0.7. The total area of seagrass beds was approximately 323.09 ha, which mainly distributed in My Hoa and Thai An villages. The total area of coral reefs was approximately 564.42 ha, located along the coast and on outer area to seagrass and shoreline reefs. This study demonstrates the applicability of VNREDSAT-1 for underwater habitat monitoring. The results could be useful for natural resources managers to devise strategies for management and

  17. Are seagrass beds indicators of anthropogenic nutrient stress in the rocky intertidal?

    PubMed

    Honig, Susanna E; Mahoney, Brenna; Glanz, Jess S; Hughes, Brent B

    2017-01-15

    It is well established that anthropogenic nutrient inputs harm estuarine seagrasses, but the influence of nutrients in rocky intertidal ecosystems is less clear. In this study, we investigated the effect of anthropogenic nutrient loading on Phyllospadix spp., a rocky intertidal seagrass, at local and regional scales. At sites along California, Washington, and Oregon, we demonstrated a significant, negative correlation of urban development and Phyllospadix bed thickness. These results were echoed locally along an urban gradient on the central California coast, where Phyllospadix shoot δ(15)N was negatively associated with Phyllospadix bed thickness, and experimentally, where nutrient additions in mesocosms reduced Phyllospadix shoot formation and increased epiphytic cover on Phyllospadix shoots. These findings provide evidence that coastal development can threaten rocky intertidal seagrasses through increased epiphytism. Considering that seagrasses provide vital ecosystem services, mitigating eutrophication and other factors associated with development in the rocky intertidal coastal zone should be a management priority. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. The effects of sea urchin grazing and drift algal blooms on a subtropical seagrass bed community.

    PubMed

    Maciá

    2000-03-30

    Subtropical seagrass beds can be subject to relatively high levels of direct herbivory and large blooms of drift algae, both of which can have important effects on the floral and faunal components of the community. Caging experiments were used to investigate these factors in a Thalassia testudinum bed in Biscayne Bay, Florida. Abundance of sea urchins, Lytechinus variegatus, and drift algae was manipulated within the cages. Naturally occurring levels of urchin grazing do not appear to affect the T. testudinum population. With experimentally increased urchin densities in the winter, seagrass shoot density and aboveground biomass decreased significantly. Similar effects were not detected in the summer, indicating that the impact of grazing on T. testudinum is lessened during this time of year. Shoot density was more vulnerable to grazing than aboveground biomass. This may be a result of grazing-induced increases in seagrass productivity, in which the remaining shoots produce more or longer leaves. In the winter, drift algal blooms form large mats that cover the seagrass canopy. Under the normal grazing regime these algal blooms do not have significant negative effects on the seagrass. With increased grazing pressure, however, there is a synergistic effect of grazing and drift algae on seagrass shoot density. At intermediate urchin density (10 per m(-2)), cages without algae did not undergo significant decreases in shoot density, while those with algae did. At the high density of urchins, the number of seagrass shoots in cages both with and without algae decreased, but the effect was more pronounced for cages with algae. Invertebrate abundance at the field site was low relative to other seagrass beds. There were no discernible effects, either positive or negative, of urchin and algae manipulations on the sampled invertebrate community.

  19. Quantifying Seagrass Light Requirements Using an Algorithm to Spatially Resolve Depth of Colonization-Conf Abstract

    EPA Science Inventory

    Depth of colonization (Zc) is a useful seagrass growth metric that describes seagrass response to light attenuation. Similarly, percent surface irradiance (% SI) at Zc is a measure of seagrass light requirements with applications in seagrass ecology and management. Methods for ...

  20. Quantifying Seagrass Light Requirements Using an Algorithm to Spatially Resolve Depth of Colonization-Conf Abstract

    EPA Science Inventory

    Depth of colonization (Zc) is a useful seagrass growth metric that describes seagrass response to light attenuation. Similarly, percent surface irradiance (% SI) at Zc is a measure of seagrass light requirements with applications in seagrass ecology and management. Methods for ...

  1. Low-Canopy Seagrass Beds Still Provide Important Coastal Protection Services

    PubMed Central

    Christianen, Marjolijn J. A.; van Belzen, Jim; Herman, Peter M. J.; van Katwijk, Marieke M.; Lamers, Leon P. M.; van Leent, Peter J. M.; Bouma, Tjeerd J.

    2013-01-01

    One of the most frequently quoted ecosystem services of seagrass meadows is their value for coastal protection. Many studies emphasize the role of above-ground shoots in attenuating waves, enhancing sedimentation and preventing erosion. This raises the question if short-leaved, low density (grazed) seagrass meadows with most of their biomass in belowground tissues can also stabilize sediments. We examined this by combining manipulative field experiments and wave measurements along a typical tropical reef flat where green turtles intensively graze upon the seagrass canopy. We experimentally manipulated wave energy and grazing intensity along a transect perpendicular to the beach, and compared sediment bed level change between vegetated and experimentally created bare plots at three distances from the beach. Our experiments showed that i) even the short-leaved, low-biomass and heavily-grazed seagrass vegetation reduced wave-induced sediment erosion up to threefold, and ii) that erosion was a function of location along the vegetated reef flat. Where other studies stress the importance of the seagrass canopy for shoreline protection, our study on open, low-biomass and heavily grazed seagrass beds strongly suggests that belowground biomass also has a major effect on the immobilization of sediment. These results imply that, compared to shallow unvegetated nearshore reef flats, the presence of a short, low-biomass seagrass meadow maintains a higher bed level, attenuating waves before reaching the beach and hence lowering beach erosion rates. We propose that the sole use of aboveground biomass as a proxy for valuing coastal protection services should be reconsidered. PMID:23723969

  2. Low-canopy seagrass beds still provide important coastal protection services.

    PubMed

    Christianen, Marjolijn J A; van Belzen, Jim; Herman, Peter M J; van Katwijk, Marieke M; Lamers, Leon P M; van Leent, Peter J M; Bouma, Tjeerd J

    2013-01-01

    One of the most frequently quoted ecosystem services of seagrass meadows is their value for coastal protection. Many studies emphasize the role of above-ground shoots in attenuating waves, enhancing sedimentation and preventing erosion. This raises the question if short-leaved, low density (grazed) seagrass meadows with most of their biomass in belowground tissues can also stabilize sediments. We examined this by combining manipulative field experiments and wave measurements along a typical tropical reef flat where green turtles intensively graze upon the seagrass canopy. We experimentally manipulated wave energy and grazing intensity along a transect perpendicular to the beach, and compared sediment bed level change between vegetated and experimentally created bare plots at three distances from the beach. Our experiments showed that i) even the short-leaved, low-biomass and heavily-grazed seagrass vegetation reduced wave-induced sediment erosion up to threefold, and ii) that erosion was a function of location along the vegetated reef flat. Where other studies stress the importance of the seagrass canopy for shoreline protection, our study on open, low-biomass and heavily grazed seagrass beds strongly suggests that belowground biomass also has a major effect on the immobilization of sediment. These results imply that, compared to shallow unvegetated nearshore reef flats, the presence of a short, low-biomass seagrass meadow maintains a higher bed level, attenuating waves before reaching the beach and hence lowering beach erosion rates. We propose that the sole use of aboveground biomass as a proxy for valuing coastal protection services should be reconsidered.

  3. Decline, recovery, and site persistence of intertidal seagrass beds in the Northern Wadden Sea since the 1930s

    NASA Astrophysics Data System (ADS)

    Dolch, Tobias; Buschbaum, Christian; Reise, Karsten

    2013-04-01

    Seagrasses fulfil several vital ecological functions and are therefore of high importance for coastal ecosystems. They are furthermore regarded as an indicator for ecosystem health. However, as seagrasses are very sensitive towards a variety of environmental parameters, particularly to human induced eutrophication, they are declining worldwide. In contrast to this global crisis of seagrass ecosystems, intertidal seagrass beds in the Northfrisian Wadden Sea (coastal North Sea) have recovered recently and may constitute the largest intertidal seagrass area in Europe. Aerial photographs taken from the Northfrisian Wadden Sea in the periods 1935 - 1937, 1958 - 1959 and 2005 were used to map long-term variability in extent and spatial distribution of intertidal seagrass beds. Photographs were visually analyzed, and seagrass beds were recorded and quantified with a geographical information system (GIS). This set of long-term records was completed by aerial mapping data until 2011. Today, seagrass beds cover more than 15 % of the tidal flat area of the Northfrisian Wadden Sea, which is rather similar to the extent they had in the 1930s. However, the seagrass development in the last 80 years is characterized by an intermittent loss of bed area of about 34 % in the late 1950s and even 60 % in the 1970s - 1990s. This is followed by a recovery and a strong increase in seagrass bed area since the mid-1990s. It is assumed that the intermittent loss was primarily caused by direct and indirect effects of eutrophication but also by increasing hydrodynamics and associated sediment instability, which are also adverse for seagrasses. The recovery is consequently the result of the decrease of these adverse effects. Despite the variability in seagrass extent, beds show a remarkable persistence at preferred sites and over several decades. Core areas for seagrass were identified in the shelter of high sands and barrier islands where the beds are protected from the prevailing westerly

  4. Diel trophic structuring of seagrass bed fish assemblages in the Wakatobi Marine National Park, Indonesia

    NASA Astrophysics Data System (ADS)

    Unsworth, Richard K. F.; Wylie, Elizabeth; Smith, David J.; Bell, James J.

    2007-03-01

    The faunal communities of seagrass beds throughout SE Asia are highly threatened by continued overexploitation, yet their ecology is poorly understood. Developing a greater understanding of the faunal linkages between seagrass beds and associated coastal habitats can facilitate more informed ecosystem level management. The present study used beach seine netting to sample seagrass bed fish assemblages in the Wakatobi Marine National Park, Indonesia, to investigate diel migrations of fish into and out of seagrass beds. These fish assemblages were found to be diverse relative to other studies within the region, with many species being economically important to local subsistence fisheries. The abundance, species richness and trophic structure of these fish assemblages changed with time of day indicating that fish populations are in a dynamic state. Mean fish abundance increased by ≈45% from day to night (Day: 8.61 ± 0.13 fish 100 m -2; Night: 15.6 ± 1.4 fish 100 m -2) while mean species richness increased from 6.6 ± 1.9 per seine haul to 11.4 ± 0.2. Increasing abundance and diversity of fish at night suggests migration onto these habitats from nearby habitats such as reefs, mangroves or deep water; and/or increased activity of those fish resident within seagrass habitats. Division of species into trophic categories enabled the trophic structure of changing fish assemblages to be examined. Assemblages were dominated during both the day and night by invertebrate and fish feeders; however, a major diel change in trophic structure occurred in the abundance of omnivores. During the day omnivores were abundant, but they were replaced at night by exclusive invertebrate feeders. We therefore propose that diel changes in seagrass fish assemblages are predominantly structured by food availability, although other factors such as increased night-time shelter provision were also found to be important albeit to a much lesser extent.

  5. Mapping spatial resources with GPS animal telemetry: foraging manatees locate seagrass beds in the Ten Thousand Islands, Florida, USA

    USGS Publications Warehouse

    Slone, Daniel H.; Reid, James P.; Kenworthy, W. Judson

    2013-01-01

    Turbid water conditions make the delineation and characterization of benthic habitats difficult by traditional in situ and remote sensing methods. Here, we develop and validate modeling and sampling methodology for detecting and characterizing seagrass beds by analyzing GPS telemetry records from radio-tagged manatees. Between October 2002 and October 2005, 14 manatees were tracked in the Ten Thousand Islands (TTI) in southwest Florida (USA) using Global Positioning System (GPS) tags. High density manatee use areas were found to occur off each island facing the open, nearshore waters of the Gulf of Mexico. We implemented a spatially stratified random sampling plan and used a camera-based sampling technique to observe and record bottom observations of seagrass and macroalgae presence and abundance. Five species of seagrass were identified in our study area: Halodule wrightii, Thalassia testudinum, Syringodium filiforme, Halophila engelmannii, and Halophila decipiens. A Bayesian model was developed to choose and parameterize a spatial process function that would describe the observed patterns of seagrass and macroalgae. The seagrasses were found in depths <2 m and in the higher manatee use strata, whereas macroalgae was found at moderate densities at all sampled depths and manatee use strata. The manatee spatial data showed a strong association with seagrass beds, a relationship that increased seagrass sampling efficiency. Our camera-based field sampling proved to be effective for assessing seagrass density and spatial coverage under turbid water conditions, and would be an effective monitoring tool to detect changes in seagrass beds.

  6. Detection of seagrass beds in Khunk Graben Bay, Thailand, using ALOS AVNI2 image

    NASA Astrophysics Data System (ADS)

    Komatsu, Teruhisa; Noiraksar, Thidarat; Sakamoto, Shingo X.; Sawayama, Shuhei; Miyamoto, Hiroomi; Phauk, Sophany; Thongdee, Pornthep; Jualaong, Suthep; Nishida, Shuhei

    2012-11-01

    Coastal habitats having high productivity provide numerous ecological services such as foods, protection from strong waves through buffering effect, fixation of CO2 through photosynthesis, fostering biodiversity etc. However, increasing human impacts and climate change decrease or degrade coastal habitats. ASEAN region is developing most rapidly in the world. In the developing region, it is necessary to grasp present spatial distributions of habitats as a baseline data with standardized mapping methods. Remote sensing is one of the most effective methods for mapping. Japan Aerospace Exploration Agency (JAXA) provides non-commercial satellite images with ultra-high spatial resolution optical sensors (10 m), AVNIR2, similar to LANDSAT TM. Using ALOS AVNIR2 images it may be possible to make habitat map in the region. In Thailand, shrimp ponds cause degradation of coastal ecosystem through cutting mangroves and eutrophicated discharge from ponds. We examined capability of remote sesing with ALOS AVNIR2 to map seagrass beds in Khung Kraben Bay, Chanthaburi Province, Thailand, surrounded by shrimp ponds. We analyzed ALOS AVNIR2 taken on 25 January 2008. Ground truth survey was conducted in October 2010 using side scan sonar and scuba diving. The survey revealed that there were broad seagrass beds consisting of Enhalus acroides. We used a decision tree to detect seagrass beds in the bay with quite turbid seawater coupled with Depth-Invariant Index proposed by Lyzenga (1985) and bottom reflectances. We could succeed to detect seagrass beds. Thus it is concluded that ALOS AVNIR2 is practical to map seagrass beds in this region.

  7. Tiny Is Mighty: Seagrass Beds Have a Large Role in the Export of Organic Material in the Tropical Coastal Zone

    PubMed Central

    Gillis, Lucy G.; Ziegler, Alan D.; van Oevelen, Dick; Cathalot, Cecile; Herman, Peter M. J.; Wolters, Jan W.; Bouma, Tjeerd J.

    2014-01-01

    Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent systems, but differences in this function among ecosystems remain poorly quantified. Seagrass beds are often a relatively small section of this coastal zone, but have a potentially much larger ecological influence than suggested by their surface area. Using stable isotopes as tracers of oceanic, terrestrial, mangrove and seagrass sources, we investigated the origin of particulate organic matter in nine mangrove bays around the island of Phuket (Thailand). We used a linear mixing model based on bulk organic carbon, total nitrogen and δ13C and δ15N and found that oceanic sources dominated suspended particulate organic matter samples along the mangrove-seagrass-ocean gradient. Sediment trap samples showed contributions from four sources oceanic, mangrove forest/terrestrial and seagrass beds where oceanic had the strongest contribution and seagrass beds the smallest. Based on ecosystem area, however, the contribution of suspended particulate organic matter derived from seagrass beds was disproportionally high, relative to the entire area occupied by mangrove forests, the catchment area (terrestrial) and seagrass beds. The contribution from mangrove forests was approximately equal to their surface area, whereas terrestrial contributions to suspended organic matter under contributed compared to their relative catchment area. Interestingly, mangrove forest contribution at 0 m on the transects showed a positive relationship with the exposed frontal width of the mangrove, indicating that mangrove forest exposure to hydrodynamic energy may be a controlling factor in mangrove outwelling. However we found no relationship between seagrass bed contribution and any physical factors, which we measured. Our results indicate that although seagrass beds occupy a relatively small area of the coastal zone, their role in the export of organic matter is disproportional and should be

  8. Tiny is mighty: seagrass beds have a large role in the export of organic material in the tropical coastal zone.

    PubMed

    Gillis, Lucy G; Ziegler, Alan D; van Oevelen, Dick; Cathalot, Cecile; Herman, Peter M J; Wolters, Jan W; Bouma, Tjeerd J

    2014-01-01

    Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent systems, but differences in this function among ecosystems remain poorly quantified. Seagrass beds are often a relatively small section of this coastal zone, but have a potentially much larger ecological influence than suggested by their surface area. Using stable isotopes as tracers of oceanic, terrestrial, mangrove and seagrass sources, we investigated the origin of particulate organic matter in nine mangrove bays around the island of Phuket (Thailand). We used a linear mixing model based on bulk organic carbon, total nitrogen and δ13C and δ15N and found that oceanic sources dominated suspended particulate organic matter samples along the mangrove-seagrass-ocean gradient. Sediment trap samples showed contributions from four sources oceanic, mangrove forest/terrestrial and seagrass beds where oceanic had the strongest contribution and seagrass beds the smallest. Based on ecosystem area, however, the contribution of suspended particulate organic matter derived from seagrass beds was disproportionally high, relative to the entire area occupied by mangrove forests, the catchment area (terrestrial) and seagrass beds. The contribution from mangrove forests was approximately equal to their surface area, whereas terrestrial contributions to suspended organic matter under contributed compared to their relative catchment area. Interestingly, mangrove forest contribution at 0 m on the transects showed a positive relationship with the exposed frontal width of the mangrove, indicating that mangrove forest exposure to hydrodynamic energy may be a controlling factor in mangrove outwelling. However we found no relationship between seagrass bed contribution and any physical factors, which we measured. Our results indicate that although seagrass beds occupy a relatively small area of the coastal zone, their role in the export of organic matter is disproportional and should be

  9. Habitat fragmentation has some impacts on aspects of ecosystem functioning in a sub-tropical seagrass bed.

    PubMed

    Sweatman, Jennifer L; Layman, Craig A; Fourqurean, James W

    2017-05-01

    Habitat fragmentation impacts ecosystem functioning in many ways, including reducing the availability of suitable habitat for animals and altering resource dynamics. Fragmentation in seagrass ecosystems caused by propeller scarring is a major source of habitat loss, but little is known about how scars impact ecosystem functioning. Propeller scars were simulated in seagrass beds of Abaco, Bahamas, to explore potential impacts. To determine if plant-herbivore interactions were altered by fragmentation, amphipod grazers were excluded from half the experimental plots, and epiphyte biomass and community composition were compared between grazer control and exclusion plots. We found a shift from light limitation to phosphorus limitation at seagrass patch edges. Fragmentation did not impact top-down control on epiphyte biomass or community composition, despite reduced amphipod density in fragmented habitats. Seagrass and amphipod responses to propeller scarring suggest that severely scarred seagrass beds could be subject to changes in internal nutrient stores and amphipod distribution. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Effects of herbivorous birds on intertidal seagrass beds in the northern Wadden Sea

    NASA Astrophysics Data System (ADS)

    Nacken, M.; Reise, K.

    2000-07-01

    During autumn migration (September to December), brent geese (Branta b. bernicla) and wigeon (Anas penelope) feed on the seagrass Zostera noltii in the nearshore, upper tidal zone leeward of the island of Sylt (eastern North Sea). To graze on leaves and shoots above the sediment and on rhizomes and roots below, these birds reworked the entire upper 1 cm layer of sediment eight times within this 3-month period. In addition, brent geese excavated pits 3-10 cm deep by trampling in order to feed on below-ground phytomass. About 12% of the seagrass beds became pitted to an average depth of 4.5 cm. Using net exclosures, it was estimated that birds removed 34 g dry weight m-2 of above-ground and 28 g of below-ground phytomass. This corresponds to 45% of the phytomass in September. Of the overall loss of phytomass from September to December, 63% was caused by birds. Roughly half of the leaves fell off anyway until December and the other half were taken by the birds. Below the ground, phytomass remained almost constant where birds were excluded, while with birds phytomass of rhizomes and roots was halved. In spite of this strong effect, in the next vegetation period the blade density was lower at former exclosure sites compared to the ambient seagrass bed. The underlying process seems to be a self-inhibition of dense overwintering seagrass by mud accretion. Assuming our experimental results can be scaled up to the entire seagrass bed, we hypothesize that in the sheltered upper intertidal zone, seasonal erosion caused by herbivorous geese and ducks is necessary for the persistence of Z. noltii.

  11. Abrupt transitions between macrobenthic faunal assemblages across seagrass bed margins

    NASA Astrophysics Data System (ADS)

    Barnes, R. S. K.; Hamylton, S.

    2013-10-01

    The nature of the transition from one contrasting macrobenthic assemblage to another across interfaces between intertidal seagrass and unvegetated sand was investigated in the subtropical Moreton Bay Marine Park, eastern Australia, via six two-dimensional core lattices. The same pattern of transition was manifested in each lattice. Macrofaunal abundance, species density (both observed and estimated total) and assemblage composition did not vary with distance away from the interface within the 0.75 m wide marginal bands of each habitat type. Neither were there significant differences in assemblage metrics or composition between the marginal and non-edge regions of either habitat. There were, however, very marked differences in assemblage composition, abundance and species density across the 25 cm wide strip on either side of the actual interface, the interacting assemblages reacting symmetrically. All these differences therefore took place over an ecotone distance of only 0.5 m at most. Spatial trends in assemblage metrics across the boundary zone were captured accurately by second and third order polynomial regression models. It also appeared that edge effects on individual species within the seagrass were a variable local response not a consistent effect of closeness to the bare sand.

  12. Level of contamination by metallic trace elements and organic molecules in the seagrass beds of Guadeloupe Island.

    PubMed

    Bouchon, Claude; Lemoine, Soazig; Dromard, Charlotte; Bouchon-Navaro, Yolande

    2016-01-01

    Seagrass bed ecosystems occupy the most important part of coastal shelf in the French West Indies. They also constitute nurseries for many invertebrates and fishes harvested by local fisheries. In Guadeloupe, coastal fish stocks are declining meanwhile several agroecosystems revealed to be heavily contaminated by pollutants (agricultural lands, rivers, mangroves, seagrass beds, and coral reefs). Considering these facts, a study of the contamination of seagrass beds (8000 ha) of the Grand Cul-de-Sac Marin (GCSM) bay was conducted on their sediments and marine phanerogams. The analyses concerned six metals (Cd, Cu, Hg, Pb, V, Zn), tributyltin, 18 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), 38 polychlorobiphenyls (PCBs), dithiocarbamates (CS2 residues), and 225 pesticide molecules.Overall, the level of contamination of the seagrass beds was low for both sediments and phanerogams. Metallic trace elements were the main pollutants but with higher concentrations recorded in coastal sites, and their distribution can be explained by the proximity of river mouths and current patterns. The level of contamination was lower in plants than in sediments. However, the level of contamination between these two compartments was significantly correlated. The conclusion of this study is that, unlike other coastal ecosystems of Guadeloupe such as mangroves, the seagrass beds in the GCSM present a low degree of pollution. The observed level of contaminants does not seem to threaten the role of nursery played by the seagrass beds and does not likely present a risk for the reintroduction of manatees.

  13. Composition and diversity of fish species in seagrass bed ecosystem at Muara Binuangeun, Lebak, Banten

    NASA Astrophysics Data System (ADS)

    Kholis, N.; Patria, M. P.; Soedjiarti, T.

    2017-07-01

    Research of composition and diversity of fish species in seagrass bed ecosystem at Muara Binuangeun, Lebak, Banten, had been conducted in May and November 2015. Catch per Unit of Effort (CPUE) was used as a method with push net and boat net as fishing gear. Fishing was conducted during low tide. Collected samples were preserved with 10 % Formalin Solution and then being identified in the laboratory. In total, 286 fishes were collected from 17 families and 38 species. Moolgarda sp. was the most relative abundant species (17,13 %) and Istiblennius edentulus was a fish species with the highest relative frequency. Diversity index value of seagrass bed ecosystem was 2,973. Different sampling time showed the different composition of fish, in an example of Arothron immaculatus.

  14. Using remote sensing technique for analyzing temporal changes of seagrass beds by human impacts in waters of Cam Ranh Bay, Vietnam

    NASA Astrophysics Data System (ADS)

    Minh Thu, Phan; Hoang Son, Tong Phuoc; Komatsu, Teruhisa

    2012-10-01

    Seagrass beds/meadows are very productive ecosystems with high biodiversities. However, they have been degraded under high pressures of human activities. Combining depth-invariance index and ground-truthing, distribution of seagrass beds in Cam Ranh Bay was identified by analyses of multi-remote sensing images such as LANDSAT, SPOT and ALOS AVNIR-2. Although coverage of seagrass meadows was1178 ha, the seagrass meadows were being degraded by illegal fishing methods, aquaculture and discharges from industries and living domestics. The reducing ratio of seagrass coverage has been increased in recent years. While the depth-invariance index method would help to detect the areas of seagrass beds, this method requires combination of field trip and absorption library methods to increase classification accuracy. Final maps of the status and changes of seagrass beds could help to integrate the sustainable development of economy with protection of natural resources.

  15. Mangrove loss leads to fish hyperutilization of seagrass beds in a UNESCO biosphere reserve.

    PubMed

    Bologna, P A X

    2014-05-01

    Hurricanes severely damaged a mangrove forest in a UNESCO biosphere reserve in the U.S. Virgin Islands. The system has yet to recover and when alternative habitats have been destroyed, it is shown that juvenile fishes will hyperutilize seagrass beds at densities significantly greater than in areas that maintain functioning mangroves. Despite over a decade of recovery time, the affected mangrove system remains inhospitable to juvenile fishes. © 2014 The Fisheries Society of the British Isles.

  16. Carbon and nitrogen stable isotope analysis of an Amphibolis griffithii seagrass bed

    NASA Astrophysics Data System (ADS)

    Smit, A. J.; Brearley, A.; Hyndes, G. A.; Lavery, P. S.; Walker, D. I.

    2005-11-01

    Western Australia has a rich diversity of seagrasses, many of which are meadow-forming species with a high diversity of associated epiphytes. Potential food sources and dominant invertebrates and fishes were collected in a non-quantitative sampling programme designed to examine the variability in naturally occurring isotopes ( 13C/ 12C and 15N/ 14N) within an Amphibolis griffithii dominated seagrass bed in Western Australia. The aims of this study were to determine the isotopic composition of the organisms, and to determine the sources of carbon available to consumers using the variations in the ratio of 15N/ 14N and 13C/ 12C among organisms in the seagrass assemblage. Autotrophs showed a wide distribution of δ13C values, with seagrass material significantly enriched in 13C relative to macroalgal sources by >10‰. This variation allowed us to successfully identify macroalgae as the main contributor of carbon to the trophic structure. δ15N ratios did not vary to the degree that would make it useful as tracer, but it was applied to estimating the total number of trophic transfers of nitrogen. Analysis of δ15N values suggested that four trophic positions were present, with fishes ( Acanthaluteres vittiger, Scobonichthys granulatus and Siphonognathus radiatus, Pelsartia humeralis, Pelates sexlineatus, Leviprora inops, Odax acroptilus and Notolabrus parilus) occupying the top two levels. δ13C of seston (20-200 μm) and sedimentary organic matter indicate that seagrass material is the main contributor to these two carbon pools, and that very little of it is incorporated into the trophic structure.

  17. Material exchange and food web of seagrass beds in the Sylt-Rømø Bight: how significant are community changes at the ecosystem level?

    NASA Astrophysics Data System (ADS)

    Asmus, H.; Asmus, R.

    2000-07-01

    Material exchange, biodiversity and trophic transfer within the food web were investigated in two different types of intertidal seagrass beds: a sheltered, dense Zostera marina bed and a more exposed, sparse Z. noltii bed, in the Northern Wadden Sea. Both types of Zostera beds show a seasonal development of above-ground biomass, and therefore measurements were carried out during the vegetation period in summer. The exchange of particles and nutrients between seagrass beds and the overlying water was measured directly using an in situ flume. Particle sedimentation [carbon (C), nitrogen (N) and phosphorus (P) constituents] from the water column prevailed in dense seagrass beds. In the sheltered, dense seagrass bed, a net particle uptake was found even on windy days (7-8 Beaufort). Dissolved inorganic N and orthophosphate were mainly taken up by the dense seagrass bed. At times of strong winds, nutrients were released from the benthic community to tidal waters. In a budget calculation of total N and total P, the dense seagrass beds were characterised as a material sink. The seagrass beds with sparse Z. noltii were a source of particles even during calm weather. The uptake of dissolved inorganic N in the sparse seagrass bed was low but significant, while the uptake of inorganic phosphate and silicate by seagrasses and their epiphytes was exceeded by release processes from the sediment into the overlying water. Estimates at the ecosystem level showed that material fluxes of seagrass beds in the Sylt-Rømø Bight are dominated by the dense type of Zostera beds. Therefore, seagrass beds act as a sink for particles and for dissolved inorganic nutrients. During storms, seagrass beds are distinct sources for inorganic nutrients. The total intertidal area of the Sylt-Rømø Bight could be described as a sink for particles and a source for dissolved nutrients. This balance of the material budget was estimated by either including or excluding seagrass beds. Including the

  18. Effects of seagrass bed removal for tourism purposes in a Mauritian bay.

    PubMed

    Daby, D

    2003-01-01

    Stresses and shocks are increasing on the main natural assets in Mauritius (Western Indian Ocean) by tourism (marine-based) development activities. Seagrasses are removed by hotels in the belief that they are unsightly or harbour organisms causing injury to bathers. Environmental changes (e.g. sediment characteristics and infauna distribution, water quality, seagrass biomass) resulting from clearing of a seagrass bed to create an aesthetically pleasant swimming zone for clients of a hotel were monitored during June 2000-July 2001, and compared to conditions prevailing in an adjacent undisturbed area. Key observations in the disturbed area were: highly turbid water overlying a destabilized lagoon seabed, complete loss of sediment infauna, and dramatic dry weight biomass declines (e.g. 72 and 65% in S. isoetifolium and H. uninervis, respectively). Such disruptions draw-down resilience rendering the marine habitats less robust and more vulnerable to environmental change and extreme events, with higher risks of chaos and ecological collapse, and constitute a major threat to the industry itself.

  19. A one-century suite of seagrass bed maps: can we trust ancient maps?

    NASA Astrophysics Data System (ADS)

    Leriche, Agathe; Boudouresque, Charles-François; Bernard, Guillaume; Bonhomme, Patrick; Denis, Jacques

    2004-02-01

    To assess the dynamics of seagrass beds, it is necessary to be able to compare their present day and former distribution patterns. In most cases, ancient data are available in the form of maps whose reliability must be estimated before comparison. In the study area (near Marseilles, France), a series of maps of the seagrass Posidonia oceanica beds spanning more than one century (dating from 1883, 1897, 1958, 1975, 1979, 1991 and 2000, respectively) are available. In addition, a new map was established, using aerial photography (shallow areas), side scan sonar (deeper areas) and data validation by ground truth. In order to help assess the value of the ancient maps, a Reliability Index (RI) is proposed. The RI, rated from 0 to 50, weighs three parameters: (i) the initial scale of the map (source map) and the working scale (target map); (ii) the method of data acquisition (e.g. dredges, grabs, aerial photography, side scan sonar, scuba diving); and (iii) the method of data georeferencing. Dramatic differences in the distribution of seagrass beds are apparent between the eight maps. In view of the biological features of P. oceanica (e.g. slow rate of change of the meadow limits under natural conditions and the persistence of rhizomes after its death), it is possible that some of these differences may not reflect change over time but may be due to errors in the ancient maps. In contrast, other differences are plausible and validated by field data, e.g. the regression of the lower limit of the meadow. It was thus possible to compare the calculated RI for each map and the plausibility of observed differences as a basis for calibrating the RI.

  20. Caribbean-wide, long-term study of seagrass beds reveals local variations, shifts in community structure and occasional collapse.

    PubMed

    van Tussenbroek, Brigitta I; Cortés, Jorge; Collin, Rachel; Fonseca, Ana C; Gayle, Peter M H; Guzmán, Hector M; Jácome, Gabriel E; Juman, Rahanna; Koltes, Karen H; Oxenford, Hazel A; Rodríguez-Ramirez, Alberto; Samper-Villarreal, Jimena; Smith, Struan R; Tschirky, John J; Weil, Ernesto

    2014-01-01

    The CARICOMP monitoring network gathered standardized data from 52 seagrass sampling stations at 22 sites (mostly Thalassia testudinum-dominated beds in reef systems) across the Wider Caribbean twice a year over the period 1993 to 2007 (and in some cases up to 2012). Wide variations in community total biomass (285 to >2000 g dry m(-2)) and annual foliar productivity of the dominant seagrass T. testudinum (<200 and >2000 g dry m(-2)) were found among sites. Solar-cycle related intra-annual variations in T. testudinum leaf productivity were detected at latitudes > 16°N. Hurricanes had little to no long-term effects on these well-developed seagrass communities, except for 1 station, where the vegetation was lost by burial below ∼1 m sand. At two sites (5 stations), the seagrass beds collapsed due to excessive grazing by turtles or sea-urchins (the latter in combination with human impact and storms). The low-cost methods of this regional-scale monitoring program were sufficient to detect long-term shifts in the communities, and fifteen (43%) out of 35 long-term monitoring stations (at 17 sites) showed trends in seagrass communities consistent with expected changes under environmental deterioration.

  1. Caribbean-Wide, Long-Term Study of Seagrass Beds Reveals Local Variations, Shifts in Community Structure and Occasional Collapse

    PubMed Central

    van Tussenbroek, Brigitta I.; Cortés, Jorge; Collin, Rachel; Fonseca, Ana C.; Gayle, Peter M. H.; Guzmán, Hector M.; Jácome, Gabriel E.; Juman, Rahanna; Koltes, Karen H.; Oxenford, Hazel A.; Rodríguez-Ramirez, Alberto; Samper-Villarreal, Jimena; Smith, Struan R.; Tschirky, John J.; Weil, Ernesto

    2014-01-01

    The CARICOMP monitoring network gathered standardized data from 52 seagrass sampling stations at 22 sites (mostly Thalassia testudinum-dominated beds in reef systems) across the Wider Caribbean twice a year over the period 1993 to 2007 (and in some cases up to 2012). Wide variations in community total biomass (285 to >2000 g dry m−2) and annual foliar productivity of the dominant seagrass T. testudinum (<200 and >2000 g dry m−2) were found among sites. Solar-cycle related intra-annual variations in T. testudinum leaf productivity were detected at latitudes > 16°N. Hurricanes had little to no long-term effects on these well-developed seagrass communities, except for 1 station, where the vegetation was lost by burial below ∼1 m sand. At two sites (5 stations), the seagrass beds collapsed due to excessive grazing by turtles or sea-urchins (the latter in combination with human impact and storms). The low-cost methods of this regional-scale monitoring program were sufficient to detect long-term shifts in the communities, and fifteen (43%) out of 35 long-term monitoring stations (at 17 sites) showed trends in seagrass communities consistent with expected changes under environmental deterioration. PMID:24594732

  2. Preliminary study of mysid community on seagrass bed of Pulau Tinggi, Johor

    NASA Astrophysics Data System (ADS)

    Siang, Tan Hai; Rahim, Azman Abdul; Ross, Othman Haji

    2015-09-01

    This study aims to elucidate the abundance and species composition of the mysid community from seagrass bed of Pulau Tinggi. Samples were taken from July 2009 until October 2009 excluding September 2009 by using epibenthic sledge from Kampung Pasir Panjang and Kampug Sebirah Kecil. A greater abundance of mysids occurred in the seagrass area of Kampung Pasir Panjang (69.10%) compared to the Kampung Sebirah Kecil (30.90%). Maximum mysid abundance occurred during October at both study sites for the whole study period. A total of 1136 mysid individuals comprising 14 species from 5 subfamilies were identified. They were Erythrops minuta Hansen, 1910, Anchialina dentata Pillai, 1964, Haplostylus bengalensis (Hansen, 1910), Haplostylus sp. 1, Haplostylus sp. 2, Pseudanchialina inermis (Illig, 1906), Prionomysis aspera Ii, 1937, Acanthomysis longispina Fukuoka & Murano, 2002, Acanthomysis platycauda (Pillai, 1961), Acanthomysis quadrispinosa Nouvel, 1965, Anisomysis aikawai Ii, 1964, Lycomysis spinicauda Hansen, 1910 and Siriella vulgaris Hansen, 1910. Maximum species richness occurred in the Kampung Sebirah Kecil (10) during July 2009 followed by October 2009 (9) and August 2009 (8) while for Kampung Pasir Panjang highest species richness occurred during October 2009 (8), July 2009 (7) and August 2009 (6). Siriella vulgaris was the most dominant species consisting 41.20% (195ind/m3) of the total mysids sampled.

  3. Temporal changes in benthic communities of seagrass beds impacted by a tsunami in the Andaman Sea, Thailand

    NASA Astrophysics Data System (ADS)

    Whanpetch, Napakhwan; Nakaoka, Masahiro; Mukai, Hiroshi; Suzuki, Takao; Nojima, Satoshi; Kawai, Takashi; Aryuthaka, Chittima

    2010-04-01

    Seagrass beds are susceptible to various natural and human-induced disturbances. Disturbances affect not only seagrasses, but also the abundance and diversity of associated macrofaunal communities. The Andaman Sea coast of Thailand was heavily affected by the tsunami of December 26, 2004. To examine its impact on seagrass macrofaunal communities, we compared the abundance, diversity and taxa composition by quantitative samplings in 2001 (before the tsunami) and in 2005 and 2006 (after the tsunami). Macrobenthic animals and sediments were collected from vegetated and nonvegetated areas of two sites that had received different levels of tsunami disturbances. A large decline in abundance and diversity was observed in the nonvegetated areas after the tsunami, whereas an increase was observed in the vegetated areas. The magnitude of decline and subsequent recovery of abundance and diversity of macrobenthic animals in nonvegetated areas were similar between the two sites, suggesting that their temporal changes were not solely related to the magnitude of the tsunami disturbance. Similarity of the benthic animals differed greatly between 2001 and 2005-2006 at the nonvegetated areas, whereas it varied less among the 3 years at the seagrass-vegetated areas. This study demonstrated that the presence of seagrass vegetation alters the patterns of temporal variation in macrofaunal assemblages and subsequent recovery processes following a tsunami.

  4. ANALYSIS OF BACTERIAL COMMUNITIES IN SEAGRASS BED SEDIMENTS BY DOUBLE-GRADIENT DENATURING GRADIENT GEL ELECTROPHORESIS OF PCR-AMPLIFIED 16SRRNA GENES

    EPA Science Inventory

    Bacterial communities associated with seagrass bed sediments are not well studied. The work presented here investigated several factors, including the presence or absence of vegetation, depth into sediment, and season, and their impact on bacterial community diversity. Double gra...

  5. ANALYSIS OF BACTERIAL COMMUNITIES IN SEAGRASS BED SEDIMENTS BY DOUBLE-GRADIENT DENATURING GRADIENT GEL ELECTROPHORESIS OF PCR-AMPLIFIED 16SRRNA GENES

    EPA Science Inventory

    Bacterial communities associated with seagrass bed sediments are not well studied. The work presented here investigated several factors, including the presence or absence of vegetation, depth into sediment, and season, and their impact on bacterial community diversity. Double gra...

  6. Stocks and sources of carbon buried in the salt marshes and seagrass beds of Patos Lagoon Estuary, Southern Brazil

    NASA Astrophysics Data System (ADS)

    Patterson, Elizabeth; Johnson, Beverly; Dostie, Philip; Copertino, Margareth

    2016-04-01

    This project investigates carbon stocks in salt marshes and seagrass beds in the Patos Lagoon estuary, the largest choked lagoon in the world, located in Southern Brazil. The study was conducted in the mesohaline region, at three shallow shoals. At each shoal, three sediment cores (50 cm deep) and plant biomass samples (above and belowground) were collected along a transect line, spanning from the marsh to seagrass beds (total = 9 sediment cores). The 50cm cores were subsampled and analyzed for organic carbon (C) and nitrogen (N) content, C/N ratios, and the isotope ratios of 13C/12C, and 15N/14N. The organic carbon content of these sediments ranged between 10% (in surface sediments) and 1% (deeper in the core), suggesting that both the salt marshes and seagrass beds in this region are sequestering carbon. Early results indicate that cores taken in marsh dominated by C3 plants (Scirpus maritimus) tended to be the most depleted in 13C with δ13C values around -25‰. Cores taken in marsh dominated by C4 plants (Spartina alterniflora, Spartina densiflora), seagrass beds (Ruppia maritima) , and non vegetated areas were generally isotopically heavier with δ13C values ranging -20‰ to -15‰, indicating a mix of organic sources in the sediments. The δ15N values and C/N ratios both varied with most values falling in a range of 2-8‰ and 7-20 respectively. Analysis of the δ 34S isotope composition of the sediments is currently underway and may provide better information on the relative contributions of macro and micro algae in the sediments. The present data will reveal the carbon stock size, as well as the types and history of organic matter deposition in Patos Lagoon estuary.

  7. Influence of seagrass beds and oyster parks on the abundance and biomass patterns of meio- and macrobenthos in tidal flats

    NASA Astrophysics Data System (ADS)

    Castel, Jacques; Labourg, Pierre-Jean; Escaravage, Vincent; Auby, Isabelle; Garcia, Maria Elena

    1989-01-01

    In Arcachon Bay, on the south-west coast of France, the intertidal area is mainly occupied by sandbanks, oyster parks ( Crassostrea gigas) and mud flats covered with seagrass beds ( Zostera noltii). In order to estimate the relative contribution of meio- and macrofauna to the benthic ecology of these tidal flats, seven stations were studied seasonally for a year. Relationships between faunal density and biomass, and external factors such as sediment structure, benthic chlorophyll and seagrass debris were investigated. A comparison was made between bare sands, oyster beds and vegetated sediment in semi-exposed conditions and in sheltered areas. Using a stepwise method of multiple linear regression it was shown that high densities of macrobenthos are mostly explained by high quantities of plant debris. For meiofauna, together with plant debris, other effective variables are involved: silt content, organic carbon, chlorophyll pigments. On an average, a correlation between macro- and meiofaunal abundances could be found. However, this general pattern is modified by the biogenic structure created by the oysters and seagrass. When compared to the adjacent sandbanks, oysters clearly enhanced meiofaunal abundance (from 1130-4170 individuals 10 cm -2) but depressed macrofaunal densities (from 640-370 individuals 400 cm -2). The organic-rich oyster biodeposits probably favour meiofauna by an increase of the trophic resources but do not favour macroinfauna by inducing low oxygen concentrations. Moreover, it is likely that macrofauna is more sensitive to predation than meiofauna both in sandbanks and in oyster parks. For both meio- and macrofauna the highest incidences (7200 individuals 10 cm -2 and 2470 individuals 400 cm -2, respectively) are recorded in seagrass bed sediments. Zostera induces an enhancement of organic detritus and provides a refuge against predation. In terms of biomass, the macrofauna/meiofauna ratio is 25·1 in sandbanks, 1·5 in oyster parks and 4·2 in

  8. Drivers of estuarine benthic species distribution patterns following a restoration of a seagrass bed: a functional trait analyses.

    PubMed

    Dolbeth, Marina; Cardoso, Patrícia; Grilo, Tiago; Raffaelli, Dave; Pardal, Miguel Ângelo

    2013-07-15

    We integrate information on functional diversity (FD) patterns from estuarine intertidal benthic communities from different habitats and along a temporal disturbance gradient, to understand the drivers of species coexistence patterns. Species and traits' biomass levels seemed to be first determined by habitat filtering, selecting those traits better adapted to the biologically challenging estuarine environment. Within that subset of traits and within each habitat, biotic interactions were probably high, as evidenced by high α-diversity and community weighted mean differences. The former patterns hold for the disturbance/recovery scenario considered. However, as the estuary recovered, biomass became more distributed among different trait categories, consistent with increases in FD when the seagrass started to increase. Policy towards the restoration of seagrass bed and other biogenic structures, and improving the connectivity within adjacent systems were confirmed and suggested, as this would imply higher FD and potentially higher resilience to disturbance within the estuarine intertidal system.

  9. Application of Dredged Materials and Steelmaking Slag as Basal Media to Restore and Create Seagrass Beds: Mesocosm and Core Incubation Experiments

    NASA Astrophysics Data System (ADS)

    Tsukasaki, A.; Suzumura, M.; Tsurushima, N.; Nakazato, T.; Huang, Y.; Tanimoto, T.; Yamada, N.; Nishijima, W.

    2016-02-01

    Seagrass beds stabilize bottom sediments, improve water quality and light conditions, enhance species diversity, and provide habitat complexity in coastal marine environments. Seagrass beds are now experiencing worldwide decline by rapid environmental changes. Possible options of seagrass bed restoration are civil engineering works including mounding to raise the bottom to elevations with suitable light for seagrass growth. Reuse or recycling of dredged materials (DM) and various industrial by-products including steelmaking slags is a beneficial option to restore and create seagrass beds. To evaluate the applicability of DM and dephosphorization slag (Slag) as basal media of seagrass beds, we carried out mesocosm experiments and core incubation experiments in a land-based flow-through seawater tank over a year. During the mesocosm experiment, no difference was found in growth of eelgrass (Zostera marina L.) and macrobenthic community structures between Slag-based sediments and sand-based control experiments, even though Slag-based sediments exhibited substantially higher pH than sand-based sediments. During the core incubation experiment, we investigated detailed variation and distributions of pH and nutrients, and diffusion fluxes of nutrients between the sediment/seawater interface. Though addition of Slag induced high pH up to 10.7 in deep layers (< 5 cm), the surface pH decreased rapidly within 10 days. Concentrations of dissolved inorganic nitrogen were comparable between Slag- and sand-based sediments, whereas dissolved phosphate concentration was substantially reduced by the addition of Slag. The low concentrations of phosphate was likely due to precipitation with calcium under high pH condition. Diffusion fluxes of nutrients from the cores were comparable with those reported in natural coastal systems. It was suggested that the mixture of Slag and DM is applicable as basal media for construction of artificial seagrass beds.

  10. A MODEL FOR THE DISTRIBUTION OF BACTERIA IN THE SEAGRASS RHIZOSPHERE REDOX GRADIENT

    EPA Science Inventory

    Abstract and Oral presentation for the meeting of Wetland and Estuary Scientists from the US Gulf Coast and S.E. Atlantic.

    A conceptual model of seagrass bed sediments accounts for observations on the distribution and activities of bacteria associated with seagrass roots i...

  11. Determination of in situ biomass and energetics in seagrass beds on the west coast of Florida. Topical report, May 1982-January 1984

    SciTech Connect

    Dawes, C.J.

    1984-01-01

    The Gulf Coastal region of Florida supports extensive grass beds that almost continuously cover the shallow (1-5m) depths from Apalachicola Bay to Anclote Bay and in Tampa Bay. Attached and drift benthic seaweeds occur as well and may have higher energetic yields than the seagrasses. The shallow and continuous beds offer a possible source for plant biomass use in methane production, if sufficient material is available throughout the year and the energetics are high enough. Triweekly samplings at three sites around Tampa Bay and bimonthly samplings at four sites along the west coast of Florida showed highest biomass occurring during the spring through fall months. The available biomass of combined attached and drift seagrasses and seaweeds was lower than that predicted when compared with terrestrial crops. Naturally occurring seagrass and seaweed beds do not have sufficient biomass to justify harvesting for biogass production, although energetics levels are high.

  12. SEDIMENT AND PLANT PHOSPHORUS IN TWO THALASSIA TESTUDINUM SEAGRASS BEDS OF SANTA ROSA SOUND, NW FLORIDA

    EPA Science Inventory

    We investigated phosphorus concentrations in the seagrass, Thalassia testudinum, and the supporting quartz sediments of two meadows in Santa Rosa Sound. One meadow was sampled during 2002, and the other during 2003. Triplicate sediment and biomass cores were obtained from beneath...

  13. SEDIMENT AND PLANT PHOSPHORUS IN TWO THALASSIA TESTUDINUM SEAGRASS BEDS OF SANTA ROSA SOUND, NW FLORIDA

    EPA Science Inventory

    We investigated phosphorus concentrations in the seagrass, Thalassia testudinum, and the supporting quartz sediments of two meadows in Santa Rosa Sound. One meadow was sampled during 2002, and the other during 2003. Triplicate sediment and biomass cores were obtained from beneath...

  14. The relative importance of mangroves and seagrass beds as feeding habitats for resident and transient fishes from Florida and Belize:: evidence from dietary and stable isotope analyses

    EPA Science Inventory

    In the western Atlantic region, the contribution of mangrove food-sources to fish diets has been considered of more limited importance then previously expected due to their constant flooding and proximity to adjacent coastal habitats such as seagrass beds which provide potential ...

  15. The relative importance of mangroves and seagrass beds as feeding habitats for resident and transient fishes from Florida and Belize:: evidence from dietary and stable isotope analyses

    EPA Science Inventory

    In the western Atlantic region, the contribution of mangrove food-sources to fish diets has been considered of more limited importance then previously expected due to their constant flooding and proximity to adjacent coastal habitats such as seagrass beds which provide potential ...

  16. Overgrazing of a large seagrass bed by the sea urchin Lytechinus variegatus in Outer Florida Bay

    USGS Publications Warehouse

    Rose, C.D.; Sharp, W.C.; Kenworthy, W.J.; Hunt, J.H.; Lyons, W.G.; Prager, E.J.; Valentine, J.F.; Hall, M.O.; Whitfield, P.E.; Fourqurean, J.W.

    1999-01-01

    Unusually dense aggregations of the sea urchin Lytechinus variegatus overgrazed at least 0.81 km2 of seagrass habitat in Outer Florida Bay (USA) between August 1997 and May 1998. Initially, sea-urchin densities were as high as 364 sea urchins m-2, but they steadily declined to within a range of 20 to 50 sea urchins m-2 by December 1998. Prior to this event, sea-urchin densities were 95% of the short-shoot apical meristems were removed by sea-urchin grazing in our study area. Such extensive loss may severely limit recovery of this seagrass community by vegetative reproduction. Effects of the removal of seagrass biomass have already resulted in the depletion of epifaunal-infaunal mollusk assemblages and resuspension of fine-grained (<64 ??m) surface sediments - which have caused significant changes in community structure and in the physical properties of the sediments. These changes, coupled with the loss of essential fishery habitat, reductions in primary and secondary production, and degradation of water quality, may lead to additional, longer-term, indirect effects that may extend beyond the boundaries of the grazed areas and into adjacent coastal ecosystems.

  17. Effect of nutrient enrichment on the source and composition of sediment organic carbon in tropical seagrass beds in the South China Sea.

    PubMed

    Liu, Songlin; Jiang, Zhijian; Zhang, Jingping; Wu, Yunchao; Lian, Zhonglian; Huang, Xiaoping

    2016-09-15

    To assess the effect of nutrient enrichment on the source and composition of sediment organic carbon (SOC) beneath Thalassia hemprichii and Enhalus acoroides in tropical seagrass beds, Xincun Bay, South China Sea, intertidal sediment, primary producers, and seawater samples were collected. No significant differences on sediment δ(13)C, SOC, and microbial biomass carbon (MBC) were observed between T. hemprichii and E. acoroides. SOC was mainly of autochthonous origin, while the contribution of seagrass to SOC was less than that of suspended particulate organic matter, macroalgae and epiphytes. High nutrient concentrations contributed substantially to SOC of seagrass, macroalgae, and epiphytes. The SOC, MBC, and MBC/SOC ratio in the nearest transect to fish farming were the highest. This suggested a more labile composition of SOC and shorter turnover times in higher nutrient regions. Therefore, the research indicates that nutrient enrichment could enhance plant-derived contributions to SOC and microbial use efficiency.

  18. Habitat use by fishes in coral reefs, seagrass beds and mangrove habitats in the Philippines.

    PubMed

    Honda, Kentaro; Nakamura, Yohei; Nakaoka, Masahiro; Uy, Wilfredo H; Fortes, Miguel D

    2013-01-01

    Understanding the interconnectivity of organisms among different habitats is a key requirement for generating effective management plans in coastal ecosystems, particularly when determining component habitat structures in marine protected areas. To elucidate the patterns of habitat use by fishes among coral, seagrass, and mangrove habitats, and between natural and transplanted mangroves, visual censuses were conducted semiannually at two sites in the Philippines during September and March 2010-2012. In total, 265 species and 15,930 individuals were recorded. Species richness and abundance of fishes were significantly higher in coral reefs (234 species, 12,306 individuals) than in seagrass (38 species, 1,198 individuals) and mangrove (47 species, 2,426 individuals) habitats. Similarity tests revealed a highly significant difference among the three habitats. Fishes exhibited two different strategies for habitat use, inhabiting either a single (85.6% of recorded species) or several habitats (14.4%). Some fish that utilized multiple habitats, such as Lutjanus monostigma and Parupeneus barberinus, showed possible ontogenetic habitat shifts from mangroves and/or seagrass habitats to coral reefs. Moreover, over 20% of commercial fish species used multiple habitats, highlighting the importance of including different habitat types within marine protected areas to achieve efficient and effective resource management. Neither species richness nor abundance of fishes significantly differed between natural and transplanted mangroves. In addition, 14 fish species were recorded in a 20-year-old transplanted mangrove area, and over 90% of these species used multiple habitats, further demonstrating the key role of transplanted mangroves as a reef fish habitat in this region.

  19. Habitat Use by Fishes in Coral Reefs, Seagrass Beds and Mangrove Habitats in the Philippines

    PubMed Central

    Honda, Kentaro; Nakamura, Yohei; Nakaoka, Masahiro; Uy, Wilfredo H.; Fortes, Miguel D.

    2013-01-01

    Understanding the interconnectivity of organisms among different habitats is a key requirement for generating effective management plans in coastal ecosystems, particularly when determining component habitat structures in marine protected areas. To elucidate the patterns of habitat use by fishes among coral, seagrass, and mangrove habitats, and between natural and transplanted mangroves, visual censuses were conducted semiannually at two sites in the Philippines during September and March 2010–2012. In total, 265 species and 15,930 individuals were recorded. Species richness and abundance of fishes were significantly higher in coral reefs (234 species, 12,306 individuals) than in seagrass (38 species, 1,198 individuals) and mangrove (47 species, 2,426 individuals) habitats. Similarity tests revealed a highly significant difference among the three habitats. Fishes exhibited two different strategies for habitat use, inhabiting either a single (85.6% of recorded species) or several habitats (14.4%). Some fish that utilized multiple habitats, such as Lutjanus monostigma and Parupeneus barberinus, showed possible ontogenetic habitat shifts from mangroves and/or seagrass habitats to coral reefs. Moreover, over 20% of commercial fish species used multiple habitats, highlighting the importance of including different habitat types within marine protected areas to achieve efficient and effective resource management. Neither species richness nor abundance of fishes significantly differed between natural and transplanted mangroves. In addition, 14 fish species were recorded in a 20-year-old transplanted mangrove area, and over 90% of these species used multiple habitats, further demonstrating the key role of transplanted mangroves as a reef fish habitat in this region. PMID:23976940

  20. Functional changes due to invasive species: Food web shifts at shallow Posidonia oceanica seagrass beds colonized by the alien macroalga Caulerpa racemosa

    NASA Astrophysics Data System (ADS)

    Deudero, S.; Box, A.; Alós, J.; Arroyo, N. L.; Marbà, N.

    2011-06-01

    species and consequent trophic guild and niche breadth shifts at invaded Caulerpa beds increase our understanding of the seagrass systems.

  1. Dracograllus trukensis sp. nov. (Draconematidae: Nematoda) from a seagrass bed ( Zostera spp.) in Chuuk Islands, Micronesia, Central Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Min, Wongi; Kim, Dongsung; Decraemer, Wilfrida; Rho, Hyun Soo

    2016-09-01

    A new species of free-living marine draconematid nematode, Dracograllus trukensis sp. nov., is described based on the specimens collected from the sediments of a intertidal seagrass bed from Chuuk Islands, Micronesia. Dracograllus trukensis sp. nov. differs from other species of the genus by the combination of the following characteristics: the presence of numerous minute spiny ornamented body cuticular annules in both sexes, eight cephalic adhesion tubes inserted on the head capsule in both sexes, the presence of stiff posteriorly directed setae anterior to posterior adhesion tubes in both sexes, the shape (large, elongated, open loop-shaped in male and large, elongated, closed loop-shaped in female) and position (longer ventral arm extending to the first body annule in male) of amphideal fovea, shorter spicule length (34-42 μm), the presence of sexual dimorphism in shape and length of the non-annulated tail terminus, and number of posterior sublateral adhesion tubes (10 in male and 13-15 in female) and posterior subventral adhesion tubes (8-10 in male and 9-11 in female). A comparative table on the biogeographical and ecological characteristics of the species of Dracograllus is presented. This is the first taxonomic report on the genus Dracograllus from Chuuk Islands, Micronesia, central western Pacific Ocean.

  2. Effects of Nutrient Enrichment on Primary Production and Biomass of Sediment Microalgae in a Subtropical Seagrass Bed

    USDA-ARS?s Scientific Manuscript database

    Eutrophication of coastal waters often leads to excessive growth of microalgal epiphytes attached to seagrass leaves; however, the effect of increased nutrient levels on sediment microalgae has not been studied within seagrass communities. A slow-release NPK Osmocote fertilizer was added to sedimen...

  3. The impact of 85 years of coastal development on shallow seagrass beds (Posidonia oceanica L. (Delile)) in South Eastern France: A slow but steady loss without recovery

    NASA Astrophysics Data System (ADS)

    Holon, F.; Boissery, P.; Guilbert, A.; Freschet, E.; Deter, J.

    2015-11-01

    Shallow Posidonia oceanica beds (0 to -15 m), the most common seagrass in the Mediterranean, were mapped from aerial photographs dating from the 1920's and from 2012 along 800 km of coastline in South-Eastern France (Provence-Alpes-Côte-d'Azur region). Changes in P. oceanica bed spatial distribution (limits and extent) during these 85 years were analyzed in terms of concordance (remaining areas), positive discordance (expanding areas) or negative discordance (lost areas). Lost areas were linked with direct or indirect impacts of coastal development (artificialized coastlines (namely harbours, ports of refuge, landfills, artificial beaches, groynes and pontoons, submarine pipelines and aquatic farms) visible on the photographs. The comparison showed that 73% of the shallow limits have declined. Considering spatial extent, remaining seagrass meadows areas accounted for the major part (85%), while lost areas accounted for 13% and expanding areas for 1.1%. Lost areas were mainly linked with artificial coastlines but 44% remained with undetermined causes (invisible pressures and/or mixed effects). The analysis of 96 coastal facilities creating the artificial (namely man-made) coastlines showed that the highest impact over the longest distance (5 km) was caused by harbours. Only artificial beaches had such a distant impact. Pontoons were the least surrounded by lost seagrass meadows areas. These quantitative data offer important information for marine conservation.

  4. Seagrass beds as ocean acidification refuges for mussels? High resolution measurements of pCO2 and O2 in a Zostera marina and Mytilus edulis mosaic habitat

    NASA Astrophysics Data System (ADS)

    Saderne, V.; Fietzek, P.; Aßmann, S.; Körtzinger, A.; Hiebenthal, C.

    2015-07-01

    It has been speculated that macrophytes beds might act as a refuge for calcifiers from ocean acidification. In the shallow nearshores of the western Kiel Bay (Baltic Sea), mussel and seagrass beds are interlacing, forming a mosaic habitat. Naturally, the diverse physiological activities of seagrasses and mussels are affected by seawater carbonate chemistry and they locally modify it in return. Calcification by shellfishes is sensitive to seawater acidity; therefore the photosynthetic activity of seagrasses in confined shallow waters creates favorable chemical conditions to calcification at daytime but turn the habitat less favorable or even corrosive to shells at night. In contrast, mussel respiration releases CO2, turning the environment more favorable for photosynthesis by adjacent seagrasses. At the end of summer, these dynamics are altered by the invasion of high pCO2/low O2 coming from the deep water of the Bay. However, it is in summer that mussel spats settle on the leaves of seagrasses until migrating to the permanent habitat where they will grow adult. These early life phases (larvae/spats) are considered as most sensitive with regard to seawater acidity. So far, the dynamics of CO2 have never been continuously measured during this key period of the year, mostly due to the technological limitations. In this project we used a combination of state-of-the-art technologies and discrete sampling to obtain high-resolution time-series of pCO2 and O2 at the interface between a seagrass and a mussel patch in Kiel Bay in August and September 2013. From these, we derive the entire carbonate chemistry using statistical models. We found the monthly average pCO2 more than 50 % (approx. 640 μatm for August and September) above atmospheric equilibrium right above the mussel patch together with large diel variations of pCO2 within 24 h: 887 ± 331 μatm in August and 742 ± 281 μatm in September (mean ± SD). We observed important daily corrosiveness for calcium

  5. Diversity of assimilatory nitrate reductase genes from plankton and epiphytes associated with a seagrass bed.

    PubMed

    Adhitya, Anita; Thomas, Florence I M; Ward, Bess B

    2007-11-01

    Assimilatory nitrate reductase gene fragments were isolated from epiphytes and plankton associated with seagrass blades collected from Tampa Bay, Florida, USA. Nitrate reductase genes from diatoms (NR) and heterotrophic bacteria (nasA) were amplified by polymerase chain reaction (PCR) using two sets of degenerate primers. A total of 129 NR and 75 nasA clones from four clone libraries, two from each of epiphytic and planktonic components, were sequenced and aligned. In addition, genomic DNA sequences for the NR fragment were obtained from Skeletonema costatum and Thalassiosira weissflogii diatom cultures. Rarefaction analysis with an operational taxonomic unit cut-off of 6% indicated that diversity of the NR and nasA clone libraries were similar, and that sequencing of the clone libraries was not yet saturated. Phylogenetic analysis indicated that 121 of the 129 NR clones sequenced were similar to diatom sequences. Of the eight non-diatom sequences, four were most closely related to the sequence of Chlorella vulgaris. Introns were found in 8% of the Tampa Bay NR sequences; introns were also observed in S. costatum, but not T. weissflogii. Introns from within the same clone library exhibited close similarity in nucleotide sequence, position and length; the corresponding exon sequences were unique. Introns from within the same component were similar in position and length, but not in nucleotide sequence. These findings raise questions about the function of introns, and mechanisms or time evolution of intron formation. A large cluster of 14 of the 75 nasA sequences was similar to sequences from Vibrio species; other sequences were closely related to sequences from Alteromonas, alpha-proteobacteria and Marinomonas-like species. Biogeographically consistent patterns were observed for the nasA Tampa Bay sequences compared with sequences from other locations: for example, Tampa Bay sequences were similar to those from the South Atlantic Bight, but not the Barents Sea. The

  6. Differences Among Fish Assemblages Associated with Nearshore Posidonia oceanica Seagrass Beds, Rocky algal Reefs and Unvegetated Sand Habitats in the Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Guidetti, P.

    2000-04-01

    Fish assemblages associated with nearshore Posidonia oceanica seagrass beds, rocky-algal reefs and unvegetated sandy substrates were studied at two sampling localities, Otranto (Apulian coast) and S. Domino (Tremiti Islands), located in the Southern and Central Adriatic Seas (Mediterranean Sea), respectively. Data were collected in situ by using non-destructive diver visual census methodology. A higher species richness and fish density were observed over the Posidonia seagrass and, in turn, the rocky-algal reef and unvegetated sand habitats. Planktivorous fish species ( Spicara maena, Spicara smaris and Chromis chromis) showing patchy distributions were dominant in terms of abundance at both localities. The two former species did not show any particular habitat preference, while C. chromis was common over both the Posidonia and rocky-algal habitats and was only occasionally recorded over sand. Symphodus ocellatus , Diplodus annularis and Spondyliosoma cantharus were the most common species in the P. oceanica seagrass beds. Symphodus roissali, Symphodus tinca and Diplodus sargus were mainly associated with the rocky-algal reef habitats, while other species, such as Gymnammodytes cicerellus, Lithognathus mormyrus , Gobius geniporus, Mullus barbatus and Uranoscopus scaber, were censused over the unvegetated sand habitats. A cluster analysis performed on the entire fish density data set showed distinct groupings for seagrass, rocky-algal and bare sand fish assemblages, regardless of season and sampling site. Fish assemblages in the more structured (seagrass and rocky-algal reef) habitats were relatively similar to each other but quite different from those of the unstructured bare sands. With regard to small-sized specimens (juvenile stages including recruits), those of S. ocellatus, Symphodus mediterraneus, Serranus cabrilla, D. annularis, S. cantharus and Sarpa salpa were mainly censused over P. oceanica beds, while juveniles of C. chromis inhabited predominantly

  7. Diurnal time-activity budgets of redheads (Aythya americana) wintering in seagrass beds and coastal ponds in Louisiana and Texas

    USGS Publications Warehouse

    Michot, T.C.; Woodin, M.C.; Adair, S.E.; Moser, E.B.

    2006-01-01

    Diurnal time-activity budgets were determined for wintering redheads (Aythya americana) from estuarine seagrass beds in Louisiana (Chandeleur Sound) and Texas (Laguna Madre) and from ponds adjacent to the Laguna Madre. Activities differed (p<0.0001) by location, month, and diurnal time period. Resting and feeding were the most frequent activities of redheads at the two estuarine sites, whereas drinking was almost nonexistent. Birds on ponds in Texas engaged most frequently in resting and drinking, but feeding was very infrequent. Redheads from the Louisiana estuarine site rested less than birds in Texas at either the Laguna Madre or freshwater ponds. Redheads in Louisiana fed more than birds in Texas; this was partially because of weather differences (colder temperatures in Louisiana), but the location effect was still significant even when we adjusted the model for weather effects. Redheads in Louisiana showed increased resting and decreased feeding as winter progressed, but redheads in Texas did not exhibit a seasonal pattern in either resting or feeding. In Louisiana, birds maintained a high level of feeding activity during the early morning throughout the winter, whereas afternoon feeding tapered off in mid- to late-winter. Texas birds showed a shift from morning feeding in early winter to afternoon feeding in late winter. Males and females at both Chandeleur Sound and Laguna Madre showed differences in their activities, but because the absolute difference seldom exceeded 2%, biological significance is questionable. Diurnal time-activity budgets of redheads on the wintering grounds are influenced by water salinities and the use of dietary fresh water, as well as by weather conditions, tides, and perhaps vegetation differences between sites. The opportunity to osmoregulate via dietary freshwater, vs. via nasal salt glands, may have a significant effect on behavioral allocations. ?? Springer 2006.

  8. Assessment of propeller and off-road vehicle scarring in seagrass beds and wind-tidal flats of the southwestern Gulf of Mexico

    USGS Publications Warehouse

    Martin, S.R.; Onuf, C.P.; Dunton, K.H.

    2008-01-01

    We used aerial photography and GIS to establish a quantitative baseline of propeller and off-road vehicle (ORV) scarring in seagrass and wind-tidal flats of the upper Laguna Madre in the Padre Island National Seashore (Texas, USA). We also examined scar recovery through comparison of recent (2002, 2005) and historical (1967) aerial photographs of the study area. Scarring intensity was calculated using two different methods. In the first, polygons were visually drawn around groups of scars on digital images. Scarring intensity was estimated as light (20%), based on the total coverage of scars within each polygon (taking into account the length, width, and density of scars). We developed a more objective method that employed creation of vector grid cells and buffers that incorporated the localized ecological impact of scars. Results of spatial and temporal analysis revealed that the polygon approach greatly underestimated the magnitude of scarring. For example, in a single photograph, 7% of seagrass area was lightly scarred according to the polygon method; but light scarring increased to 51% according to grid analysis of the same image. Our results also indicated that propeller scars in Halodule wrightii beds appear to recover in less than three years and ORV tracks have persisted in the wind-tidal flats for at least 38 years. Our approach provides resource managers with procedures for a more objective and efficient assessment of physical disturbances to seagrass and wind-tidal flats caused by boats and ORVs. ?? 2008 by Walter de Gruyter.

  9. The effect of ocean acidification on carbon storage and sequestration in seagrass beds; a global and UK context.

    PubMed

    Garrard, Samantha L; Beaumont, Nicola J

    2014-09-15

    Ocean acidification will have many negative consequences for marine organisms and ecosystems, leading to a decline in many ecosystem services provided by the marine environment. This study reviews the effect of ocean acidification (OA) on seagrasses, assessing how this may affect their capacity to sequester carbon in the future and providing an economic valuation of these changes. If ocean acidification leads to a significant increase in above- and below-ground biomass, the capacity of seagrass to sequester carbon will be significantly increased. The associated value of this increase in sequestration capacity is approximately £500 and 600 billion globally between 2010 and 2100. A proportionally similar increase in carbon sequestration value was found for the UK. This study highlights one of the few positive stories for ocean acidification and underlines that sustainable management of seagrasses is critical to avoid their continued degradation and loss of carbon sequestration capacity. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Florida seagrass habitat evaluation: A comparative survey for chemical quality

    EPA Science Inventory

    Contaminant concentrations were determined for media associated with 13 Florida seagrass beds. Concentrations of 10 trace metals were more commonly detected in surface water, sediment and two seagrass species than PAHs, pesticides and PCBs. Concentrations of copper and arsenic ...

  11. Florida seagrass habitat evaluation: A comparative survey for chemical quality

    EPA Science Inventory

    Contaminant concentrations were determined for media associated with 13 Florida seagrass beds. Concentrations of 10 trace metals were more commonly detected in surface water, sediment and two seagrass species than PAHs, pesticides and PCBs. Concentrations of copper and arsenic ...

  12. Colored Dissolved Organic Matter in Sediments and Seagrass Beds and Its Impact on Shallow Water Benthic Optical Properties

    DTIC Science & Technology

    2001-09-30

    Island (LSI), Exuma , the Bahamas. A limited field study was also undertaken in seagrass sediments in Monterey Bay. Finally, in our first tear of CoBOP...indicate that there was a net flux of CDOM off the shallow banks to Exuma Sound. Both CDOM absorbance and total DOC show a positive relationship with

  13. Whole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds (Palma Bay, NW Mediterranean)

    NASA Astrophysics Data System (ADS)

    Gazeau, F.; Duarte, C. M.; Gattuso, J.-P.; Barrón, C.; Navarro, N.; Ruiz, S.; Prairie, Y. T.; Calleja, M.; Delille, B.; Frankignoulle, M.; Borges, A. V.

    Planktonic and benthic incubations (bare and Posidonia oceanica vegetated sediments) were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the Bay of Palma (Mallorca, Spain). Results showed a contrast between the planktonic compartment, which was on average near metabolic balance (-4.6±5.9 mmol O2 m-2 d-1) and the benthic compartment, which was autotrophic (17.6±8.5 mmol O2 m-2 d-1). During two cruises in March and June 2002, planktonic and benthic incubations were performed at several stations in the bay to estimate the whole-system metabolism and to examine its relationship with partial pressure of CO2 (pCO2) and apparent oxygen utilisation (AOU) spatial patterns. Moreover, during the second cruise, when the residence time of water was long enough, net ecosystem production (NEP) estimates based on incubations were compared, over the Posidonia oceanica meadow, to rates derived from dissolved inorganic carbon (DIC) and oxygen (O2) mass balance budgets. These budgets provided NEP estimates in fair agreement with those derived from direct metabolic estimates based on incubated samples over the Posidonia oceanica meadow. Whereas the seagrass community was autotrophic, the excess organic carbon production therein could only balance the planktonic heterotrophy in shallow waters relative to the maximum depth of the bay (55 m). This generated a horizontal gradient from autotrophic or balanced communities in the shallow seagrass-covered areas, to strongly heterotrophic communities in deeper areas of the bay. It seems therefore that, on an annual scale in the whole bay, the organic matter production by the Posidonia oceanica may not be sufficient to fully compensate the heterotrophy of the planktonic compartment, which may require external organic carbon inputs, most likely from land.

  14. Benthic community responses to macroalgae invasions in seagrass beds: Diversity, isotopic niche and food web structure at community level

    NASA Astrophysics Data System (ADS)

    Deudero, S.; Box, A.; Vázquez-Luis, M.; Arroyo, N. L.

    2014-04-01

    Trophic paths between species are a useful tool for analysing the impact of species invasions of a biotic community. Species invasions produce changes at trophic level and diversity shifts by replacing native species with species of similar ecological niche. This study focused on the effects of macroalgal invasions on seagrass ecosystems. We conducted two - year bimonthly sampling of a pristine Posidonia oceanica seagrass meadow and dead matte colonized by three Caulerpa species bimonthly. The largest changes in faunal composition were found in meadows colonized by Caulerpa prolifera, where major differences in infaunal taxonomic distinctness were apparent. On the other hand, the infaunal community was quite similar between the two invasive Caulerpa species (Caulerpa taxifolia and Caulerpa racemosa). The isotopic niche based on the main trophic guilds established using stable isotope signatures at community level resulted in a highly compacted and 15N-enriched C. prolifera food web structure, indicating high overlap of food source utilization among faunal components, which is typical of degraded systems. Conversely, the P. oceanica ecosystem presented the most complex food web, while the influence of the 2 invasive species were similar. An attempt to reconstruct the food web at each vegetated habitat revealed high trophic linkages among the different trophic levels with a continuous transition among them by the various trophic guilds suggesting an adaptation response of the different organisms to the new habitat forming species.

  15. Use of a seagrass residency index to apportion commercial fishery landing values and recreation fisheries expenditure to seagrass habitat service.

    PubMed

    Jackson, Emma L; Rees, Siân E; Wilding, Catherine; Attrill, Martin J

    2015-06-01

    Where they dominate coastlines, seagrass beds are thought to have a fundamental role in maintaining populations of exploited species. Thus, Mediterranean seagrass beds are afforded protection, yet no attempt to determine the contribution of these areas to both commercial fisheries landings and recreational fisheries expenditure has been made. There is evidence that seagrass extent continues to decline, but there is little understanding of the potential impacts of this decline. We used a seagrass residency index, that was trait and evidence based, to estimate the proportion of Mediterranean commercial fishery landings values and recreation fisheries total expenditure that can be attributed to seagrass during different life stages. The index was calculated as a weighted sum of the averages of the estimated residence time in seagrass (compared with other habitats) at each life stage of the fishery species found in seagrass. Seagrass-associated species were estimated to contribute 30%-40% to the value of commercial fisheries landings and approximately 29% to recreational fisheries expenditure. These species predominantly rely on seagrass to survive juvenile stages. Seagrass beds had an estimated direct annual contribution during residency of €58-91 million (4% of commercial landing values) and €112 million (6% of recreation expenditure) to commercial and recreational fisheries, respectively, despite covering <2% of the area. These results suggest there is a clear cost of seagrass degradation associated with ineffective management of seagrass beds and that policy to manage both fisheries and seagrass beds should take into account the socioeconomic implications of seagrass loss to recreational and commercial fisheries. © 2015 Society for Conservation Biology.

  16. AUTOMATED PRODUCTION OF SEAGRASS MAPS FROM SIDESCAN SONAR IMAGERY: ACCURACY, VARIABILITY AND PATCH RESOLUTION

    EPA Science Inventory

    Maps of seagrass beds are useful for monitoring estuarine condition, managing habitats, and modeling estuarine processes. We recently developed inexpensive methods for collecting and classifying sidescan sonar (SSS) imagery for seagrass presence in turbid waters as shallow as 1-...

  17. AUTOMATED PRODUCTION OF SEAGRASS MAPS FROM SIDESCAN SONAR IMAGERY: ACCURACY, VARIABILITY AND PATCH RESOLUTION

    EPA Science Inventory

    Maps of seagrass beds are useful for monitoring estuarine condition, managing habitats, and modeling estuarine processes. We recently developed inexpensive methods for collecting and classifying sidescan sonar (SSS) imagery for seagrass presence in turbid waters as shallow as 1-...

  18. Seagrass ecosystems in the Western Indian Ocean.

    PubMed

    Gullström, Martin; de la Torre Castro, Maricela; Bandeira, Salomão; Björk, Mats; Dahlberg, Mattis; Kautsky, Nils; Rönnbäck, Patrik; Ohman, Marcus C

    2002-12-01

    Seagrasses are marine angiosperms widely distributed in both tropical and temperate coastal waters creating one of the most productive aquatic ecosystems on earth. In the Western Indian Ocean (WIO) region, with its 13 reported seagrass species, these ecosystems cover wide areas of near-shore soft bottoms through the 12 000 km coastline. Seagrass beds are found intertidally as well as subtidally, sometimes down to about 40 m, and do often occur in close connection to coral reefs and mangroves. Due to the high primary production and a complex habitat structure, seagrass beds support a variety of benthic, demersal and pelagic organisms. Many fish and shellfish species, including those of commercial interest, are attracted to seagrass habitats for foraging and shelter, especially during their juvenile life stages. Examples of abundant and widespread fish species associated to seagrass beds in the WIO belong to the families Apogonidae, Blenniidae, Centriscidae, Gerreidae, Gobiidae, Labridae, Lethrinidae Lutjanidae, Monacanthidae, Scaridae, Scorpaenidae, Siganidae, Syngnathidae and Teraponidae. Consequently, seagrass ecosystems in the WIO are valuable resources for fisheries at both local and regional scales. Still, seagrass research in the WIO is scarce compared to other regions and it is mainly focusing on botanic diversity and ecology. This article reviews the research status of seagrass beds in the WIO with particular emphasis on fish and fisheries. Most research on this topic has been conducted along the East African coast, i.e. in Kenya, Tanzania, Mozambique and eastern South Africa, while less research was carried out in Somalia and the Island States of the WIO (Seychelles, Comoros, Reunion (France), Mauritius and Madagascar). Published papers on seagrass fish ecology in the region are few and mainly descriptive. Hence, there is a need of more scientific knowledge in the form of describing patterns and processes through both field and experimental work

  19. Abstracts

    ERIC Educational Resources Information Center

    American Biology Teacher, 1977

    1977-01-01

    Included are over 50 abstracts of papers being presented at the 1977 National Association of Biology Teachers Convention. Included in each abstract are the title, author, and summary of the paper. Topics include photographic techniques environmental studies, and biological instruction. (MA)

  20. Coastal resource degradation in the tropics: does the tragedy of the commons apply for coral reefs, mangrove forests and seagrass beds.

    PubMed

    Wilkinson, Clive; Salvat, Bernard

    2012-06-01

    The keynote paper by Garrett Hardin 44 years ago introduced the term 'tragedy of the commons' into our language (Hardin, 1968); this term is now used widely, but it is neither universally accepted nor fully understood. Irrespective, the 'tragedy of the commons' is an increasing reality for more than 500 million people that rely on the biodiversity resources and services of tropical coral reefs, mangrove forests, seagrass beds and associated fisheries. These natural resources continue to decline despite major advances in our scientific understanding of how ecosystems and human populations interact, and the application of considerable conservation and management efforts at scales from local user communities to oceans. Greater effort will be required to avert increasing damage from over-exploitation, pollution and global climate change; all deriving from increasing exploitation driven by poverty and progress i.e. continuing to expand development indefinitely and extraction of resources at industrial scales. However, the 'tragedy' concept has been widely criticized as a simple metaphor for a much larger set of problems and solutions. We argue that the 'tragedy' is essentially real and will continue to threaten the lives of millions of people unless there are some major moral and policy shifts to reverse increasing damage to coastal habitats and resources. We agree with the conclusion by Hardin that the solution to the tragedy will not be through the application of natural sciences, but via implementing exceedingly difficult and controversial moral decisions. An extreme example of a moral and controversial direction suggested by Hardin was in re-examining the 'freedom to breed' as an inherent human value. The need for 'moral decisions' is even greater in 2012. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Nitrogen Cycling in Seagrass Beds Dominated by Thalassia testudinum and Halodule wrightii: the Role of Nitrogen Fixation and Ammonium Oxidation in Regulating Ammonium Availability

    NASA Astrophysics Data System (ADS)

    Capps, R.; Caffrey, J. M.; Hester, C.

    2016-02-01

    Seagrass meadows provide key ecosystem services including nursery and foraging grounds, storm and erosion buffers, biodiversity enhancers and global carbon and nutrient cycling. Nitrogen concentrations are often very low in coastal waters and sediments, which may limit primary productivity. Biological nitrogen fixation is a microbial process that converts dinitrogen to ammonium, which is readily taken up by seagrasses. In the oxygenated rhizospheres, diazotrophs provide the plant with ammonium and use root exudates as an energy source. Nitrogen fixation rates and nutrient concentrations differ between seagrass species and substrate types. Thalassia testudinum has a higher biomass and is a climax species than Halodule wrightii, which is a pioneer species. Nitrogen fixation rates are relatively consistent in Thalassia testudinum dominated sediments. However, it is relatively variable in sediments occupied by Halodule wrightii. Nitrogen fixation rates are higher in bare substrate compared to areas with Thalassia testudinum, which may be due to T. testudinum's greater efficiency in nutrient retention because it is a climax species. We hypothesize that seasonal shifts in nitrogen fixation will coincide with seasonal shifts in seagrass biomass due to higher nutrient requirements during peak growth and lower requirements during senescence and dormancy. The ratio of porewater ammonium to phosphate suggests that seagrass growth may be nitrogen limited as does nitrogen demand, estimated from gross primary productivity. Significant rates of ammonium oxidation in both surface and rhizosphere sediments contribute to this imbalance. Thus, nitrogen fixation may be critical in supporting plant growth.

  2. SULFATE-REDUCING BACTERIA IN THE SEAGRASS RHIZOSPHERE

    EPA Science Inventory

    Seagrasses are rooted in anoxic sediments that support high levels of microbial activity including utilization of sulfate as a terminal electron acceptor which is reduced to sulfide. Sulfate reduction in seagrass bed sediments is stimulated by input of organic carbon through the ...

  3. SULFATE-REDUCING BACTERIA IN THE SEAGRASS RHIZOSPHERE

    EPA Science Inventory

    Seagrasses are rooted in anoxic sediments that support high levels of microbial activity including utilization of sulfate as a terminal electron acceptor which is reduced to sulfide. Sulfate reduction in seagrass bed sediments is stimulated by input of organic carbon through the ...

  4. Colored Dissolved Organic Matter in Sediments and Seagrass Beds and its Impact on Benthic Optical Properties of Shallow Water Marine Environments - Data Analysis and Synthesis, and Student Support

    DTIC Science & Technology

    2002-09-30

    flux of CDOM off the shallow banks to the deeper waters of Exuma Sound. The CDOM spectral slope also varied with the tidal cycle implying that...We conducted studies of seagrass-carbonate sediment interactions around Lee Stocking Island, Exuma Islands, Bahamas to further examine this problem

  5. Changes in Seagrass Species Composition in Northwestern Gulf of Mexico Estuaries: Effects on Associated Seagrass Fauna

    PubMed Central

    Ray, Brandon R.; Johnson, Matthew W.; Cammarata, Kirk; Smee, Delbert L.

    2014-01-01

    The objective of this study was to measure the communities associated with different seagrass species to predict how shifts in seagrass species composition may affect associated fauna. In the northwestern Gulf of Mexico, coverage of the historically dominant shoal grass (Halodule wrightii) is decreasing, while coverage of manatee grass (Syringodium filiforme) and turtle grass (Thalassia testudinum) is increasing. We conducted a survey of fishes, crabs, and shrimp in monospecific beds of shoal, manatee, and turtle grass habitats of South Texas, USA to assess how changes in sea grass species composition would affect associated fauna. We measured seagrass parameters including shoot density, above ground biomass, epiphyte type, and epiphyte abundance to investigate relationships between faunal abundance and these seagrass parameters. We observed significant differences in communities among three seagrass species, even though these organisms are highly motile and could easily travel among the different seagrasses. Results showed species specific relationships among several different characteristics of the seagrass community and individual species abundance. More work is needed to discern the drivers of the complex relationships between individual seagrass species and their associated fauna. PMID:25229897

  6. Changes in seagrass species composition in northwestern Gulf of Mexico estuaries: effects on associated seagrass fauna.

    PubMed

    Ray, Brandon R; Johnson, Matthew W; Cammarata, Kirk; Smee, Delbert L

    2014-01-01

    The objective of this study was to measure the communities associated with different seagrass species to predict how shifts in seagrass species composition may affect associated fauna. In the northwestern Gulf of Mexico, coverage of the historically dominant shoal grass (Halodule wrightii) is decreasing, while coverage of manatee grass (Syringodium filiforme) and turtle grass (Thalassia testudinum) is increasing. We conducted a survey of fishes, crabs, and shrimp in monospecific beds of shoal, manatee, and turtle grass habitats of South Texas, USA to assess how changes in sea grass species composition would affect associated fauna. We measured seagrass parameters including shoot density, above ground biomass, epiphyte type, and epiphyte abundance to investigate relationships between faunal abundance and these seagrass parameters. We observed significant differences in communities among three seagrass species, even though these organisms are highly motile and could easily travel among the different seagrasses. Results showed species specific relationships among several different characteristics of the seagrass community and individual species abundance. More work is needed to discern the drivers of the complex relationships between individual seagrass species and their associated fauna.

  7. Lugworm ( Abarenicola affinis) in seagrass and unvegetated habitats

    NASA Astrophysics Data System (ADS)

    Goerlitz, Stefan; Berkenbusch, Katrin; Probert, P. Keith

    2015-06-01

    In Otago, southern New Zealand, the lugworm Abarenicola affinis resides in neighbouring tidal inlets with and without seagrass ( Zostera muelleri). A comparison of abundance, body size and biomass of A. affinis between seagrass habitat (Papanui Inlet) and unvegetated habitat (Hoopers Inlet) showed little seasonal variation of these parameters in each habitat and relatively similar abundances between both habitats. In contrast, lugworm biomass was considerably lower in the seagrass habitat due to the lack of large individuals compared with unvegetated habitat. In the seagrass habitat, there was a significant negative influence of Z. muelleri below-ground biomass on abundance and biomass of A. affinis, indicating that seagrass affected lugworm burrowing and/or feeding processes. In contrast to the unvegetated habitat, where lugworms spread relatively evenly across the intertidal area, lugworms were mostly restricted to the upper intertidal zone in the seagrass habitat. The findings suggest that the extensive seagrass bed in the mid and low intertidal zones of Papanui Inlet limited lugworm distribution in an otherwise suitable habitat. Whereas small lugworms colonised seagrass areas, the largest individuals occurred only in unvegetated sediment and seemed to be more hampered by the presence of seagrass than smaller individuals. The findings highlight negative feedback between antagonistic ecosystem engineers, with the potential of seagrass physical structures (autogenic engineering) to impact negatively on lugworm activity (allogenic engineering).

  8. (abstract) Development of Sorbent Bed Assembly for a Periodic 10K Solid Hydrogen Cryocooler

    NASA Technical Reports Server (NTRS)

    Wade, L. A.; Bowman, R. C., Jr.; Gilkinson, D. R.; Sywulka, P. H.

    1993-01-01

    A closed-cycle 10K sorption cryocooler is being fabricated for microgravity testing during a future space shuttle mission. A critical component of this cryogenic refrigerator is the metal hydride sorbent bed assembly (SBA). The SBA uses hydrides which absorb hydrogen gas at low pressure, (i.e., about 0.25 MPa from liquid hydrogen at 25K and below 0.2 kPa from solid hydrogen near 10K) and subsequently delivers hydrogen at nearly 10 MPa to a storage reservoir to repeat the Joule-Thomson (J-T) expansion process. The SBA includes three independent hydride beds where two contain LaNi(sub 4.8)Sn(sub 0.2) alloy and the third ZrNi. Detailed descriptions will be given for the three beds, which have specialized design features to enhance performance at each step of operation. In particular, two beds must rapidly absorb hydrogen in order for the J-T cold stage to reach 10K within two minutes from a 65K holding temperature. Performance characterization results will be compared to model analyses of the SBA.

  9. Accelerating Tropicalization and the Transformation of Temperate Seagrass Meadows

    PubMed Central

    Hyndes, Glenn A.; Heck, Kenneth L.; Vergés, Adriana; Harvey, Euan S.; Kendrick, Gary A.; Lavery, Paul S.; McMahon, Kathryn; Orth, Robert J.; Pearce, Alan; Vanderklift, Mathew; Wernberg, Thomas; Whiting, Scott; Wilson, Shaun

    2016-01-01

    Abstract Climate-driven changes are altering production and functioning of biotic assemblages in terrestrial and aquatic environments. In temperate coastal waters, rising sea temperatures, warm water anomalies and poleward shifts in the distribution of tropical herbivores have had a detrimental effect on algal forests. We develop generalized scenarios of this form of tropicalization and its potential effects on the structure and functioning of globally significant and threatened seagrass ecosystems, through poleward shifts in tropical seagrasses and herbivores. Initially, we expect tropical herbivorous fishes to establish in temperate seagrass meadows, followed later by megafauna. Tropical seagrasses are likely to establish later, delayed by more limited dispersal abilities. Ultimately, food webs are likely to shift from primarily seagrass-detritus to more direct-consumption-based systems, thereby affecting a range of important ecosystem services that seagrasses provide, including their nursery habitat role for fishery species, carbon sequestration, and the provision of organic matter to other ecosystems in temperate regions. PMID:28533562

  10. Consumer Depletion Alters Seagrass Resistance to an Invasive Macroalga

    PubMed Central

    Caronni, Sarah; Calabretti, Chiara; Delaria, Maria Anna; Bernardi, Giuseppe; Navone, Augusto; Occhipinti-Ambrogi, Anna; Panzalis, Pieraugusto; Ceccherelli, Giulia

    2015-01-01

    Few field studies have investigated how changes at one trophic level can affect the invasibility of other trophic levels. We examined the hypothesis that the spread of an introduced alga in disturbed seagrass beds with degraded canopies depends on the depletion of large consumers. We mimicked the degradation of seagrass canopies by clipping shoot density and reducing leaf length, simulating natural and anthropogenic stressors such as fish overgrazing and water quality. Caulerpa racemosa was transplanted into each plot and large consumers were excluded from half of them using cages. Potential cage artifacts were assessed by measuring irradiance, scouring by leaf movement, water flow, and sedimentation. Algal invasion of the seagrass bed differed based on the size of consumers. The alga had higher cover and size under the cages, where the seagrass was characterized by reduced shoot density and canopy height. Furthermore, canopy height had a significant effect depending on canopy density. The alteration of seagrass canopies increased the spread of C. racemosa only when large consumers were absent. Our results suggest that protecting declining habitats and/or restoring fish populations will limit the expansion of C. racemosa. Because MPAs also enhance the abundance and size of fish consuming seagrass they can indirectly promote algal invasion. The effects of MPAs on invasive species are context dependent and require balancing opposing forces, such as the conservation of seagrass canopy structure and the protection of fish grazing the seagrass. PMID:25723466

  11. Carbon storage in the seagrass meadows of Gazi Bay, Kenya

    PubMed Central

    Githaiga, Michael N.; Kairo, James G.; Gilpin, Linda; Huxham, Mark

    2017-01-01

    Vegetated marine habitats are globally important carbon sinks, making a significant contribution towards mitigating climate change, and they provide a wide range of other ecosystem services. However, large gaps in knowledge remain, particularly for seagrass meadows in Africa. The present study estimated biomass and sediment organic carbon (Corg) stocks of four dominant seagrass species in Gazi Bay, Kenya. It compared sediment Corg between seagrass areas in vegetated and un-vegetated ‘controls’, using the naturally patchy occurence of seagrass at this site to test the impacts of seagrass growth on sediment Corg. It also explored relationships between the sediment and above-ground Corg, as well as between the total biomass and above-ground parameters. Sediment Corg was significantly different between species, range: 160.7–233.8 Mg C ha-1 (compared to the global range of 115.3 to 829.2 Mg C ha-1). Vegetated areas in all species had significantly higher sediment Corg compared with un-vegetated controls; the presence of seagrass increased Corg by 4–6 times. Biomass carbon differed significantly between species with means ranging between 4.8–7.1 Mg C ha-1 compared to the global range of 2.5–7.3 Mg C ha-1. To our knowledge, these are among the first results on seagrass sediment Corg to be reported from African seagrass beds; and contribute towards our understanding of the role of seagrass in global carbon dynamics. PMID:28489880

  12. Observation of typhoon-induced seagrass die-off using remote sensing

    NASA Astrophysics Data System (ADS)

    Kim, Keunyong; Choi, Jong-Kuk; Ryu, Joo-Hyung; Jeong, Hae Jin; Lee, Kitack; Park, Myung Gil; Kim, Kwang Young

    2015-03-01

    Satellite remote sensing has been used as an effective tool to monitor and manage seagrass beds, but this tool is not appropriate to use in highly turbid waters along the coast of Korea. In this study, satellite data were used to identify the method for detecting seagrass beds in turbid bay waters and describing temporal changes over the past 24 years. Moreover, we found the cause of seagrass die-off phenomenon by observing the long-term satellite images and evaluating the impact of the typhoon on seagrass beds. All seagrass spectra from different sensors (Landsat TM/ETM+, Aster, Spot-4, and Kompsat-2) have low reflectance in green and high in NIR regions, whereas unvegetated seawater has the opposite spectrum features. A training area in the green band and Mahalanobis Distance Classification algorithm was adopted for classification and mapping of seagrass beds. The error matrix using the in situ reference data for Kompsat-2 image classification was 72.9% accurate. The average area of seagrass beds was 4.6 km2 from May 1990 to January 2012, and it was consistently >4.0 km2. A die-off of seagrass beds was observed in September 2012 after Typhoon Bolaven, Tembin, and Sanba consecutively passed the study site. When Typhoon Sanba passed the study site, it had sustained maximum wind speed (147.6 km h-1) during low tide, unlike the other typhoons. We found that the water column buffer did not have any effect on resistance of seagrass bed to disturbance, which led to greater damage. Additionally, the three sequential typhoons that passed through during the short time probably produced a cumulative effect. These results allow an understanding of past changes, and reveal the sudden and influential changes in seagrass distribution. As seagrass removal might have negative effect on other associated communities, comprehensive monitoring is required to ensure that disturbed seagrass habitats is recovered naturally.

  13. Trophic cascades on the edge: fostering seagrass resilience via a novel pathway.

    PubMed

    Hughes, Brent B; Hammerstrom, Kamille K; Grant, Nora E; Hoshijima, Umi; Eby, Ron; Wasson, Kerstin

    2016-09-01

    Despite widespread degradation, some coastal ecosystems display remarkable resilience. For seagrasses, a century-old paradigm has implicated macroalgal blooms stimulated by anthropogenic nutrient, loading as a primary driver of seagrass decline, yet relatively little attention has been given to drivers of seagrass resilience. In Elkhorn Slough, CA, an estuarine system characterized by extreme anthropogenic nutrient loading and macroalgal (Ulva spp.) blooms, seagrass (Zostera marina) beds have recovered concurrent with colonization of the estuary by top predators, sea otters (Enhydra lutris). Here, we follow up on the results of a previous experiment at the seagrass interior, showing how sea otters can generate a trophic cascade that promotes seagrass. We conducted an experiment and constructed structural equation models to determine how sea otters, through a trophic cascade, might affect the edge of seagrass beds where expansion occurs. We found that at the edge, sea otters promoted both seagrass and ephemeral macroalgae, with the latter contributing beneficial grazers to the seagrass. The surprising results that sea otters promote two potentially competing vegetation types, and a grazer assemblage at their boundary provides a mechanism by which seagrasses can expand in eutrophic environments, and contributes to a growing body of literature demonstrating that ephemeral macroalgae are not always negatively associated with seagrass. Our results highlight the potential for top predator recovery to enhance ecosystem resilience to anthropogenic alterations through several cascading mechanisms.

  14. Integrating scales of seagrass monitoring to meet conservation needs

    USGS Publications Warehouse

    Neckles, Hilary A.; Kopp, Blaine S.; Peterson, Bradley J.; Pooler, Penelope S.

    2012-01-01

    We evaluated a hierarchical framework for seagrass monitoring in two estuaries in the northeastern USA: Little Pleasant Bay, Massachusetts, and Great South Bay/Moriches Bay, New York. This approach includes three tiers of monitoring that are integrated across spatial scales and sampling intensities. We identified monitoring attributes for determining attainment of conservation objectives to protect seagrass ecosystems from estuarine nutrient enrichment. Existing mapping programs provided large-scale information on seagrass distribution and bed sizes (tier 1 monitoring). We supplemented this with bay-wide, quadrat-based assessments of seagrass percent cover and canopy height at permanent sampling stations following a spatially distributed random design (tier 2 monitoring). Resampling simulations showed that four observations per station were sufficient to minimize bias in estimating mean percent cover on a bay-wide scale, and sample sizes of 55 stations in a 624-ha system and 198 stations in a 9,220-ha system were sufficient to detect absolute temporal increases in seagrass abundance from 25% to 49% cover and from 4% to 12% cover, respectively. We made high-resolution measurements of seagrass condition (percent cover, canopy height, total and reproductive shoot density, biomass, and seagrass depth limit) at a representative index site in each system (tier 3 monitoring). Tier 3 data helped explain system-wide changes. Our results suggest tiered monitoring as an efficient and feasible way to detect and predict changes in seagrass systems relative to multi-scale conservation objectives.

  15. Seagrass blue carbon dynamics in the Gulf of Mexico: Stocks, losses from anthropogenic disturbance, and gains through seagrass restoration.

    PubMed

    Thorhaug, Anitra; Poulos, Helen M; López-Portillo, Jorge; Ku, Timothy C W; Berlyn, Graeme P

    2017-12-15

    Seagrasses comprise a substantive North American and Caribbean Sea blue carbon sink. Yet fine-scale estimates of seagrass carbon stocks, fluxes from anthropogenic disturbances, and potential gains in sedimentary carbon from seagrass restoration are lacking for most of the Western Hemisphere. To begin to fill this knowledge gap in the subtropics and tropics, we quantified organic carbon (Corg) stocks, losses, and gains from restorations at 8 previously-disturbed seagrass sites around the Gulf of Mexico (GoM) (n=128 cores). Mean natural seagrass Corg stocks were 25.7±6.7MgCorgha(-1) around the GoM, while mean Corg stocks at adjacent barren sites that had previously hosted seagrass were 17.8MgCorgha(-1). Restored seagrass beds contained a mean of 38.7±13.1MgCorgha(-1). Mean Corg losses differed by anthropogenic impact type, but averaged 20.98±7.14MgCorgha(-1). Corg gains from seagrass restoration averaged 20.96±8.59Mgha(-1). These results, when combined with the similarity between natural and restored Corg content, highlight the potential of seagrass restoration for mitigating seagrass Corg losses from prior impact events. Our GoM basin-wide estimates of natural Corg totaled ~36.4Tg for the 947,327ha for the USA-GoM. Including Mexico, the total basin contained an estimated 37.2-37.5Tg Corg. Regional US-GoM losses totaled 21.69Tg Corg. Corg losses differed significantly among anthropogenic impacts. Yet, seagrass restoration appears to be an important climate change mitigation strategy that could be implemented elsewhere throughout the tropics and subtropics. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Seagrass distribution and abundance in Eastern Gulf of Mexico coastal waters

    NASA Astrophysics Data System (ADS)

    Iverson, Richard L.; Bittaker, Henry F.

    1986-05-01

    The marine angiosperms Thalassia testudinum, Syringodium filiforme, and Halodule wrightii form two of the largest reported seagrass beds along the northwest and southern coasts of Florida where they cover about 3000 square km in the Big Bend area and about 5500 square km in Florida Bay, respectively. Most of the leaf biomass in the Big Bend area and outer Florida Bay was composed of Thalassia testudinum and Syringodium filiforme which were distributed throughout the beds but which were more abundant in shallow depths. A short-leaved form of Halodule wrightii grew in monotypic stands in shallow water near the inner edges of the beds, while Halophila decipiens and a longer-leaved variety of H. wrightii grew scattered throughout the beds, in monotypic stands near the outer edges of the beds, and in deeper water outside the beds. Halophila engelmanni was observed scattered at various depths throughout the seagrass beds and in monospecific patches in deep water outside the northern bed. Ruppia maritima grew primarily in brackish water around river mouths. The cross-shelf limits of the two major seagrass beds are controlled nearshore by increased water turbidity and lower salinity around river mouths and off-shore by light penetration to depths which receive 10% or more of sea surface photosynthetically active radiation. Seagrasses form large beds only along low energy reaches of the coast. The Florida Bay seagrass bed contained about twice the short-shoot density of both Thalassia testudinum and Syringodium filiforme, for data averaged over all depths, and about four times the average short-shoot density of both species in shallow water compared with the Big Bend seagrass bed. The differences in average seagrass abundance between Florida Bay and the Big Bend area may be a consequence of the effects of greater seasonal solar radiation and water temperature fluctuations experienced by plants in the northern bed, which lies at the northern distribution limit for American

  17. The contribution of scarid herbivory to seagrass ecosystem dynamics in the Indo-Pacific

    NASA Astrophysics Data System (ADS)

    Unsworth, Richard K. F.; Taylor, Joe D.; Powell, Abigail; Bell, James J.; Smith, David J.

    2007-08-01

    The functional importance of herbivory is well established within terrestrial ecosystems yet within marine ecosystems, specifically seagrass beds, consumption by herbivores has generally been considered to be of little importance due to its minor contribution to turnover of growth. The present paper challenges this assumption within the Indo-Pacific and shows that scarid (parrotfish) herbivory may have a functionally important role in the export of seagrass detrital material. Estimation of scarid herbivory on dominant Indo-Pacific seagrass species was conducted using a three pronged approach. We estimated: background levels of scarid seagrass bites; in-situ rates of grazing using tethering experiments; and seagrass grazing effect per individual scarid, which was scaled up to estimate the grazing effects of the local scarid population. All research was carried out within the Wakatobi Marine National Park, Indonesia. Research found scarid herbivory to be an important process within an Indo-Pacific seagrass bed causing the loss of up to ten times (average, four times) the daily seagrass growth. T. hemprichii was found to be lost at a rate of 0.28 ± 0.08 g DW day -1, while E. acoroides was lost at a rate of 2.85 ± 0.43 g DW day -1. We propose that such high rates of seagrass consumption are the combined effects of seasonally high grazing rates by resident scarids and short-term effects from shoals of juvenile reef scarids. Scarid grazing was indiscriminate between seagrass species and grazing was dependant on seagrass availability rather than nutritional quality. In conclusion, the present research finds scarids to be major herbivores within an Indo-Pacific seagrass bed; they not only take up carbon into the food chain through direct seagrass consumption, but also make an important indirect contribution to the detrital food chain through the export of discarded decaying seagrass material.

  18. The ecology of the seagrass meadows of the west coast of Florida: A community profile

    SciTech Connect

    Zieman, J.C.; Zieman, R.T. . Dept. of Environmental Sciences)

    1989-09-01

    This report summarizes information on the ecology of seagrass meadows on the west coast of Florida, from south of Tampa Bay to Pensacola. This area contains more than 3500 ha of seagrass beds, dominated by three species, Thalasia testudinum (turtle grass), Syringodium filiforme (manatee grass), and Halodule wrightii (shoal grass). Beds occur both on the shallow, zero-energy Continental Shelf and in inshore bays and estuaries. Species ecology, distribution, biomass, and productivity of these dominant seagrass species are discussed. Seagrass beds support a very diverse and abundant algal flora and fauna, and these organisms, and seagrass detritus form the base of a productive food chain. Seagrass beds are important nursery areas providing both cover and food, for a number of commercial and sports fishery species. Along the west Florida coast, estuarine grass beds are noticeably more stressed and impacted by human activities than the more pristine nearshore beds. Urban development and dredging and filling are the major threates to seagrass beds in this region. 500 refs., 28 figs., 14 tabs.

  19. SEAGRASS RHIZOSPHERE MICROBIAL COMMUNITIES

    EPA Science Inventory

    Devereux, Richard. 2005. Seagrass Rhizosphere Microbial Communities. In: Interactions Between Macro- and Microorganisms in Marine Sediments. E. Kristense, J.E. Kostka and R.H. Haese, Editors. American Geophysical Union, Washington, DC. p199-216. (ERL,GB 1213).

    Seagrasses ...

  20. SEAGRASS RHIZOSPHERE MICROBIAL COMMUNITIES

    EPA Science Inventory

    Devereux, Richard. 2005. Seagrass Rhizosphere Microbial Communities. In: Interactions Between Macro- and Microorganisms in Marine Sediments. E. Kristense, J.E. Kostka and R.H. Haese, Editors. American Geophysical Union, Washington, DC. p199-216. (ERL,GB 1213).

    Seagrasses ...

  1. SEAGRASS STRESS RESPONSE MODEL: THE IMPORTANCE OF LIGHT, TEMPERATURE, SEDIMENTATION AND GEOCHEMISTRY

    EPA Science Inventory

    Our objective is to define interactions between seagrass and water-column and sediment stressors. The model was developed and optimized for sediments in Thalassia testudinum seagrass beds of Lower Laguna Madre, Texas, USA and is composed of a plant sub-model and a sediment diagen...

  2. EFFECTS OF GREEN MACROALGAE ON CLASSIFICATION OF SEAGRASS IN SIDE SCAN SONAR IMAGERY

    EPA Science Inventory

    High resolution maps of seagrass beds are useful for monitoring estuarine condition, managing fish habitats, and modeling estuarine processes. Side scan sonar (SSS) is one method for producing spatially accurate seagrass maps, although it has not been used widely. Our team rece...

  3. SEAGRASS STRESS RESPONSE MODEL: THE IMPORTANCE OF LIGHT, TEMPERATURE, SEDIMENTATION AND GEOCHEMISTRY

    EPA Science Inventory

    Our objective is to define interactions between seagrass and water-column and sediment stressors. The model was developed and optimized for sediments in Thalassia testudinum seagrass beds of Lower Laguna Madre, Texas, USA and is composed of a plant sub-model and a sediment diagen...

  4. EFFECTS OF GREEN MACROALGAE ON CLASSIFICATION OF SEAGRASS IN SIDE SCAN SONAR IMAGERY

    EPA Science Inventory

    High resolution maps of seagrass beds are useful for monitoring estuarine condition, managing fish habitats, and modeling estuarine processes. Side scan sonar (SSS) is one method for producing spatially accurate seagrass maps, although it has not been used widely. Our team rece...

  5. Utilizing Depth of Colonization of Seagrasses to Develop ...

    EPA Pesticide Factsheets

    US EPA is working with state and local partners in Florida to develop numeric water quality criteria to protect estuaries from nutrient pollution. Similar to other nutrient management programs in Florida, EPA is considering status of seagrass habitats as an indicator of biological integrity, with depth of colonization of seagrasses used to relate potential seagrass extent to water quality requirements (especially water clarity). We developed and validated an automated methodology for evaluating depth of colonization and applied it to generate 228 estimates of seagrass colonization depth for coverage years spanning 67 years (1940-2007) in a total of 100 segments within 19 estuarine and coastal areas in Florida. A validation test showed that two parameters that were computed, Zc50 and ZcMax, approximated the average and 95th percentile depth at the deep-water margin of seagrass beds. Zc50 was estimated separately for continuous seagrass vs. all seagrass. Average values for Zc50 as well as long-term trends were evaluated for the entire state, illustrating a decline on average from early years (e.g., 1940-1953) to a middle period (1982-1999) and a variable degree of recovery since 2000. The largest decrease in Zc50 occurred in Florida panhandle estuaries. Extensive water quality data compiled in the Florida DEP’s Impaired Waters Rule database was evaluated to characterize Secchi depth, CDOM, TSS, and chlorophyll-a in relation to depth of colonization estima

  6. Relative foraminiferan abundance as an indicator of seagrass sediment health:

    NASA Astrophysics Data System (ADS)

    Cajandig, P.; Quiros, A.; Nolan, H.; Tallman, R.; Cooper, N.; Ayala, J.; Courtier, C.

    2013-12-01

    Authors: Patrick Cajandig*, Jose Ayala**, Nathaniel Cooper**, Catherine Courtier**, Hannah Nolan**, Rachelle Tallman**, T.E. Angela L. Quiros** * Davis High-School CA, **University of California Santa Cruz, Ecology and Evolutionary Biology Department Seagrasses are a key component in coastal ecosystems. Found in shallow marine environments, they make a large contribution to coastal ecosystem health by sustaining water quality, stabilizing the sea bottom, and providing habitat as well as food for other organisms. Seagrasses accumulate tiny grains of sediment, increasing water clarity. Just like barren hills are prone to erosion compared to vegetated, rooted down hills, we find a similar situation in the ocean. Seagrasses have broad roots that extend vertically and horizontally to help stabilize the seabed. Seagrasses support a whole ecosystem, because some organisms feed off of the seagrass alone, while others feed off the inhabitants of the seagrass. The quality of sediment is a vital part of seagrass health, just like nutrient rich soils are important to land plants. But what in seagrass sediment is a good indication of health? We hypothesize that seagrass health measures such as percent cover and seagrass species diversity are related to the abundance of foraminiferans relative to other seagrass sediment components. My mentor, T. E. Angela L. Quiros, from the University of California, Santa Cruz (UCSC), collected the sediment samples from seagrass beds in the Philippines. Samples were dried and brought to UCSC for sediment sieving. We used different sized sieves to sort the sediment. These sieves ranged from coarse to very fine sieves (Phi -2.0 (coarse) through +3.0 (fine) going in 0.5 intervals on a log scale). We weighed the sediment that was caught in each tray and separated them into bags of different size classes. To analyze each sample, we subsampled four size classes (Phi's -2.0, -1.5,-1.0, 0.0), and used a dissecting scope to identify and then weigh the

  7. Accumulation of Pb and Cu heavy metals in sea water, sediment, and leaf and root tissue of Enhalus sp. in the seagrass bed of Banten Bay

    NASA Astrophysics Data System (ADS)

    Fauziah, Faiza; Choesin, Devi N.

    2014-03-01

    Banten Bay in Indonesia is a coastal area which has been highly affected by human activity. Previous studies have reported the presence of lead (Pb) and copper (Cu) heavy metals in the seawater of this area. This study was conducted to measure the accumulation of Pb and Cu in seawater, sediment, leaf tissue, and root tissue of the seagrass species Enhalus sp. Sampling was conducted at two observation stations in Banten Bay: Station 1 (St.1) was located closer to the coastline and to industrial plants as source of pollution, while Station 2 (St.2) was located farther away offshore. At each station, three sampling points were established by random sampling. Field sampling was conducted at two different dates, i.e., on 29 May 2012 and 30 June 2012. Samples were processed by wet ashing using concentrated HNO3 acid and measured using Atomic Absorption Spectrometry (AAS). Accumulation of Pb was only detected in sediment samples in St.1, while Cu was detected in all samples. Average concentrations of Cu in May were as follows: sediment St.1 = 0.731 ppm, sediment St.2 = 0.383 ppm, seawater St.1 = 0.163 ppm, seawater St.2 = 0.174 ppm, leaf St.1 = 0.102 ppm, leaf St.2 = 0.132 ppm, root St.1= 0.139 ppm, and root St.2 = 0.075 ppm. Average measurements of Cu in June were: sediment St.1 = 0.260 ppm, leaf St.1 = 0.335 ppm, leaf St.2 = 0.301 ppm, root St.1= 0.047 ppm, and root St.2 = 0.060 ppm. In June, Cu was undetected in St.2 sediment and seawater at both stations. In May, Cu concentration in seawater exceeded the maximum allowable threshold for water as determined by the Ministry of the Environment. Spatial and temporal variation in Pb and Cu accumulation were most probably affected by distance from source and physical conditions of the environment (e.g., water current and mixing).

  8. Accumulation of Pb and Cu heavy metals in sea water, sediment, and leaf and root tissue of Enhalus sp. in the seagrass bed of Banten Bay

    SciTech Connect

    Fauziah, Faiza Choesin, Devi N.

    2014-03-24

    Banten Bay in Indonesia is a coastal area which has been highly affected by human activity. Previous studies have reported the presence of lead (Pb) and copper (Cu) heavy metals in the seawater of this area. This study was conducted to measure the accumulation of Pb and Cu in seawater, sediment, leaf tissue, and root tissue of the seagrass species Enhalus sp. Sampling was conducted at two observation stations in Banten Bay: Station 1 (St.1) was located closer to the coastline and to industrial plants as source of pollution, while Station 2 (St.2) was located farther away offshore. At each station, three sampling points were established by random sampling. Field sampling was conducted at two different dates, i.e., on 29 May 2012 and 30 June 2012. Samples were processed by wet ashing using concentrated HNO{sub 3} acid and measured using Atomic Absorption Spectrometry (AAS). Accumulation of Pb was only detected in sediment samples in St.1, while Cu was detected in all samples. Average concentrations of Cu in May were as follows: sediment St.1 = 0.731 ppm, sediment St.2 = 0.383 ppm, seawater St.1 = 0.163 ppm, seawater St.2 = 0.174 ppm, leaf St.1 = 0.102 ppm, leaf St.2 = 0.132 ppm, root St.1= 0.139 ppm, and root St.2 = 0.075 ppm. Average measurements of Cu in June were: sediment St.1 = 0.260 ppm, leaf St.1 = 0.335 ppm, leaf St.2 = 0.301 ppm, root St.1= 0.047 ppm, and root St.2 = 0.060 ppm. In June, Cu was undetected in St.2 sediment and seawater at both stations. In May, Cu concentration in seawater exceeded the maximum allowable threshold for water as determined by the Ministry of the Environment. Spatial and temporal variation in Pb and Cu accumulation were most probably affected by distance from source and physical conditions of the environment (e.g., water current and mixing)

  9. Predictive Seagrass Habitat Model

    EPA Science Inventory

    Restoration of ecosystem services provided by seagrass habitats in estuaries requires a firm understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We explored the application...

  10. Predictive Seagrass Habitat Model

    EPA Science Inventory

    Restoration of ecosystem services provided by seagrass habitats in estuaries requires a firm understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We explored the application...

  11. Geoengineering with seagrasses: is credit due where credit is given?

    NASA Astrophysics Data System (ADS)

    Johannessen, Sophia C.; Macdonald, Robie W.

    2016-11-01

    Blue carbon, the carbon fixed by vegetated coastal ecosystems including seagrasses, is reported to have a large potential to sequester atmospheric carbon dioxide. Planting, expanding or protecting seagrass meadows has, accordingly, been proposed as a form of geoengineering. Seagrasses are reported to account for up to 18% of the carbon burial in the world’s oceans, which is on the same order of magnitude as other proposed geoengineering techniques, including iron fertilization. International protocols have been developed to quantify carbon sequestration in seagrass meadows, with a view to awarding carbon credits under the Verified Carbon Standard. Unfortunately, because these protocols do not adequately account for post-depositional processes in marine sediment, they significantly overestimate carbon capture by seagrass beds and give an incorrect view of its distribution. Specifically, neglecting biomixing and remineralization of carbon in surface sediments biases burial rates high, while using sediment carbon inventory (soil carbon stock) over the top 1 m as a proxy for burial rate incorrectly identifies areas of high carbon burial. Seagrass beds likely provide a limited setting for geoengineering, because they generally comprise slowly-accumulating, fine to medium sand, which captures organic carbon less efficiently than fine-grained sediments or rapidly-accumulating delta deposits. While there is no question that seagrass meadows provide valuable habitat, nor that they are disappearing rapidly, their contribution to the global burial of carbon has not yet been established. The danger of geoengineering with seagrasses before reliable assessment methods have been established is that overestimated carbon offsets could lead to a net increase in emissions of carbon dioxide to the atmosphere.

  12. The potential impact of bedform migration on seagrass communities in Torres Strait, northern Australia

    NASA Astrophysics Data System (ADS)

    Daniell, James J.; Harris, Peter T.; Hughes, Michael G.; Hemer, Mark; Heap, Andrew

    2008-09-01

    Seagrass communities in the northwest of Torres Strait are known to disappear episodically over broad areas. Sediment mobility surveys were undertaken within two study areas during the monsoon and trade wind seasons, in the vicinity of Turnagain Island, to find out if the migration of bedforms could explain this disappearance. The two study areas covered sand bank and sand dune environments to compare and contrast their migration characteristics. Repeat multibeam sonar surveys were used to measure dune-crest migration during each season. Our results show that seagrass beds occur in the troughs of sediment-starved dunes, but no seagrass occurs in association with full-bedded dunes that are superimposed on large sand bank features. The coincidence of seagrass beds with the sediment-starved dunes is in spite of the fact that they migrate faster (0.59 m day -1) than full-bedded dunes (0.13 m day -1), which indicates that some other factor (other than dune migration rate) limits seagrass growth within Torres Strait. We suggest that seagrasses are unable to colonise full-bedded dunes because of the semi-continuously transported sand that characterises this environment. In contrast, the troughs of sediment-starved dunes experience only limited bedload transport and are less hostile for seagrasses. A conceptual model is presented to explain the occurrence of seagrass beds in relation to their proximity to migrating sand dunes. Based on our analysis, we conclude that the widespread dieback of seagrasses documented for the Turnagain Island region was not caused by dune migration.

  13. Effects of surrounding land use and water depth on seagrass dynamics relative to a catastrophic algal bloom.

    PubMed

    Breininger, David R; Breininger, Robert D; Hall, Carlton R

    2017-02-01

    Seagrasses are the foundation of many coastal ecosystems and are in global decline because of anthropogenic impacts. For the Indian River Lagoon (Florida, U.S.A.), we developed competing multistate statistical models to quantify how environmental factors (surrounding land use, water depth, and time [year]) influenced the variability of seagrass state dynamics from 2003 to 2014 while accounting for time-specific detection probabilities that quantified our ability to determine seagrass state at particular locations and times. We classified seagrass states (presence or absence) at 764 points with geographic information system maps for years when seagrass maps were available and with aerial photographs when seagrass maps were not available. We used 4 categories (all conservation, mostly conservation, mostly urban, urban) to describe surrounding land use within sections of lagoonal waters, usually demarcated by land features that constricted these waters. The best models predicted that surrounding land use, depth, and year would affect transition and detection probabilities. Sections of the lagoon bordered by urban areas had the least stable seagrass beds and lowest detection probabilities, especially after a catastrophic seagrass die-off linked to an algal bloom. Sections of the lagoon bordered by conservation lands had the most stable seagrass beds, which supports watershed conservation efforts. Our results show that a multistate approach can empirically estimate state-transition probabilities as functions of environmental factors while accounting for state-dependent differences in seagrass detection probabilities as part of the overall statistical inference procedure. © 2016 Society for Conservation Biology.

  14. DISTRIBUTION AND QUALITY OF SEAGRASS MEADOWS IN THE PENSACOLA BAY SYSTEM

    EPA Science Inventory

    Abstract for oral presentation: Seagrass meadows have 22 ecological benefits and have an estimated value of $20,500 per acre in Florida. Seagrass meadows support a variety of marine life that includes macroalgae (148 species), epiphytes (1 13 species), macroinvertebrates (230 spe...

  15. A DIAGENETIC MODEL FOR SEDIMENT-SEAGRASS INTERACTIONS

    EPA Science Inventory

    The objective of this modeling effort was to better understand the dynamic relationship between seagrass beds and their sedimentary environment using a diagenetic model. The model was developed and optimized for sediments in the Laguna Madre, TX, which is one of the world's larg...

  16. Impacts of docks on seagrass and effects of management practices to ameliorate these impacts

    NASA Astrophysics Data System (ADS)

    Gladstone, William; Courtenay, Glenn

    2014-01-01

    Seagrasses have high conservation and human-use values, but around the world they are being damaged by human activities. Compared to the larger spatial scale at which some human activities affect estuaries and their seagrasses (e.g. catchment disturbance, dredging, pollution, trawling), recreational boating and infrastructure of moorings and docks act at smaller scales. However, the cumulative effects contribute to stresses acting on seagrass beds. This study assessed the effects of docks on the native seagrass Zostera muelleri subsp. capricorni in an estuary in south-east Australia and of current management practices designed to reduce dock impacts on this seagrass. A field survey found that seagrass biomass was significantly reduced below docks, and the effects were not influenced by dock orientation. Management practices requiring the use of a mesh decking to provide greater light penetration reduced, but did not eliminate, the reduction in seagrass biomass caused by docks. A modified beyond BACI experiment provided evidence for a causal link between the installation of wooden or mesh docks and reductions in biomass of seagrass. The reduction in biomass was apparent 6 mo after dock installation, and by 26 mo seagrass biomass had declined by at least 90%. Faced with increasing coastal populations, increases in recreational use, and continued pressures from other human activities, alternative management practices that further minimize the effects of docks are needed.

  17. Spatially explicit feedbacks between seagrass meadows, sediment, and light: habitat suitability for seagrass growth

    NASA Astrophysics Data System (ADS)

    Carr, J. A.; D'Odorico, P.; McGlathery, K.; Wiberg, P. L.

    2011-12-01

    In shallow costal bays in which nutrient loading and riverine inputs are low, turbidity, and the consequent light environment are controlled by resuspension of bed sediments due to wind-waves and tidal currents. When sediment resuspension is high, resultant low light environments can limit benthic primary productivity. However, both currents and waves are affected by the presence of benthic plants such as seagrass. Moreover, vegetated areas influence a larger area than they footprint, including an adjacent downstream area. This region, while barren of seagrass, exhibits reduced shear stresses until boundary layer reformation occurs. We develop a simplistic approach to explore how the patchy structure of seagrass meadows may affect sediment resuspension and the consequent light environment under tidal and wind-wave forcing due to the presence of this sheltered region. In order to investigate the effect of patch modified hydrodynamics we generated heterogeneous vegetation covers comprised of a mosaic of randomly distributed patches with exponentially distributed radii. These heterogenous landscapes were generated from two perspectives. First, circular patches were randomly placed on a bare landscape; with each circular patch assumed to be a seagrass meadow. Second, starting from a landscape assumed to be homogenous meadow with constant shoot density, circular gaps were randomly generated. Each gap was considered a disturbance that completely removed all seagrass from within the circular region. Fractional cover of vegetation on the landscape was used to facilitate comparisons across landscape realizations and perspectives. Each landscape realization was then used to partition wave and current shear stresses on the landscape. Total suspended sediment and light attenuation characteristics were then calculated and averaged over the landscape to examine how both fractional cover and mean water depth affect the bulk sediment and light environment from the meadow or gap

  18. Photosynthetic response to globally increasing CO2 of co-occurring temperate seagrass species.

    PubMed

    Borum, Jens; Pedersen, Ole; Kotula, Lukasz; Fraser, Matthew W; Statton, John; Colmer, Timothy D; Kendrick, Gary A

    2016-06-01

    Photosynthesis of most seagrass species seems to be limited by present concentrations of dissolved inorganic carbon (DIC). Therefore, the ongoing increase in atmospheric CO2 could enhance seagrass photosynthesis and internal O2 supply, and potentially change species competition through differential responses to increasing CO2 availability among species. We used short-term photosynthetic responses of nine seagrass species from the south-west of Australia to test species-specific responses to enhanced CO2 and changes in HCO3 (-) . Net photosynthesis of all species except Zostera polychlamys were limited at pre-industrial compared to saturating CO2 levels at light saturation, suggesting that enhanced CO2 availability will enhance seagrass performance. Seven out of the nine species were efficient HCO3 (-) users through acidification of diffusive boundary layers, production of extracellular carbonic anhydrase, or uptake and internal conversion of HCO3 (-) . Species responded differently to near saturating CO2 implying that increasing atmospheric CO2 may change competition among seagrass species if co-occurring in mixed beds. Increasing CO2 availability also enhanced internal aeration in the one species assessed. We expect that future increases in atmospheric CO2 will have the strongest impact on seagrass recruits and sparsely vegetated beds, because densely vegetated seagrass beds are most often limited by light and not by inorganic carbon. © 2015 John Wiley & Sons Ltd.

  19. Seagrass ecosystem services - What's next?

    PubMed

    Nordlund, Lina Mtwana; Jackson, Emma L; Nakaoka, Masahiro; Samper-Villarreal, Jimena; Beca-Carretero, Pedro; Creed, Joel C

    2017-09-20

    Seagrasses, marine flowering plants, provide a wide range of ecosystem services, defined here as natural processes and components that directly or indirectly benefit human needs. Recent research has shown that there are still many gaps in our comprehension of seagrass ecosystem service provision. Furthermore, there seems to be little public knowledge of seagrasses in general and the benefits they provide. This begs the questions: how do we move forward with the information we have? What other information do we need and what actions do we need to take in order to improve the situation and appreciation for seagrass? Based on the outcomes from an international expert knowledge eliciting workshop, three key areas to advance seagrass ecosystem service research were identified: 1) Variability of ecosystem services within seagrass meadows and among different meadows; 2) Seagrass ecosystem services in relation to, and their connection with, other coastal habitats; and 3) Improvement in the communication of seagrass ecosystem services to the public. Here we present ways forward to advance seagrass ecosystem service research in order to raise the profile of seagrass globally, as a means to establish more effective conservation and restoration of these important coastal habitats around the world. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Effects of mining wastes on a seagrass ecosystem: metal accumulation and bioavailability, seagrass dynamics and associated community structure.

    PubMed

    Marín-Guirao, Lázaro; Atucha, Arnaldo Marín; Barba, Javier Lloret; López, Emma Martínez; Fernández, Antonio J García

    2005-09-01

    Two different Cymodocea nodosa (Ucria) Ascherson beds growing in mining-contaminated sediments were compared with two reference beds in the Mar Menor coastal lagoon. The accumulation of Zn, Pb and Cd in different fractions of the plant, the sediment parameters that regulate the availability of metals, the seabed structure and dynamics of each seagrass bed and its associated macroinvertebrate community were studied. C. nodosa accumulates metals from the sediments and reflects their bioavailability for this seagrass. At each station, the metal content of the rhizomes was lower than that of leaves and roots. The concentration of acid-volatile sulfides does not seem to influence the availability of metals to the seagrass, possibly due to oxygen transport to underground tissues. The highest metal concentration in all the contaminated stations was found in the leaf-biofilm, due to the formation of complexes between metals and the extracellular polymeric substances that form the biofilm. All the seagrass beds were seen to be undergoing expansion, those growing in contaminated sediments accumulating great quantities of metals and showing highest photosynthetic leaf surface area and highest leaf biomass. However, these structural parameters were not seen to be responsible for the differences in the faunal composition observed between contaminated and reference beds. Moreover, the multivariate analysis identified the metal content of leaves, biofilm and sediments as important variables that may be responsible for these differences in faunal composition. In this study we have demonstrated that both the seagrass C. nodosa and the biofilm on the plant leaves may be used as environmental tools in the Mar Menor lagoon. The former is an useful indicator of sediment contamination, whereas the latter seems to be a good sentinel of water quality.

  1. Direct contribution of the seagrass Thalassia testudinum to lime mud production

    PubMed Central

    Enríquez, Susana; Schubert, Nadine

    2014-01-01

    Seagrass beds contribute to oceanic carbonate lime mud production by providing a habitat for a wide variety of calcifying organisms and acting as efficient sediment traps. Here we provide evidence for the direct implication of Thalassia testudinum in the precipitation of aragonite needles. The crystals are located internally in the cell walls, and as external deposits on the blade, and are similar in size and shape to the aragonite needles reported for modern tropical carbonate factories. Seagrass calcification is a biological, light-enhanced process controlled by the leaf, and estimates of seagrass annual carbonate production in a Caribbean reef lagoon are as significant as values reported for Halimeda incrassata. Thus, we conclude that seagrass calcification is another biological source for the aragonite lime mud deposits found in tropical banks, and that tropical seagrass habitats may play a more important role in the oceanic carbon cycle than previously considered. PMID:24848374

  2. Guidelines for seagrass restoration: importance of habitat selection and donor population, spreading of risks, and ecosystem engineering effects.

    PubMed

    van Katwijk, M M; Bos, A R; de Jonge, V N; Hanssen, L S A M; Hermus, D C R; de Jong, D J

    2009-02-01

    Large-scale losses of seagrass beds have been reported for decades and lead to numerous restoration programs. From worldwide scientific literature and 20 years of seagrass restoration research in the Wadden Sea, we review and evaluate the traditional guidelines and propose new guidelines for seagrass restoration. Habitat and donor selection are crucial: large differences in survival were found among habitats and among donor populations. The need to preferably transplant in historically confirmed seagrass habitats, and to collect donor material from comparable habitats, were underlined by our results. The importance of sufficient genetic variation of donor material and prevention of genetic isolation by distance was reviewed. The spreading of risks among transplantation sites, which differed in habitat characteristics (or among replicate sites), was positively evaluated. The importance of ecosystem engineering was shown in two ways: seagrass self-facilitation and facilitation by shellfish reefs. Seagrass self-facilitative properties may require a large transplantation scale or additional measures.

  3. Spatially explicit feedbacks between seagrass meadow structure, sediment and light: Habitat suitability for seagrass growth

    USGS Publications Warehouse

    Carr, Joel; D'Odorico, Paul; McGlathery, Karen; Wiberg, Patricia L.

    2016-01-01

    In shallow coastal bays where nutrient loading and riverine inputs are low, turbidity, and the consequent light environment are controlled by resuspension of bed sediments due to wind-waves and tidal currents. High sediment resuspension and low light environments can limit benthic primary productivity; however, both currents and waves are affected by the presence of benthic plants such as seagrass. This feedback between the presence of benthic primary producers such as seagrass and the consequent light environment has been predicted to induce bistable dynamics locally. However, these vegetated areas influence a larger area than they footprint, including a barren adjacent downstream area which exhibits reduced shear stresses. Here we explore through modeling how the patchy structure of seagrass meadows on a landscape may affect sediment resuspension and the consequent light environment due to the presence of this sheltered region. Heterogeneous vegetation covers comprising a mosaic of randomly distributed patches were generated to investigate the effect of patch modified hydrodynamics. Actual cover of vegetation on the landscape was used to facilitate comparisons across landscape realizations. Hourly wave and current shear stresses on the landscape along with suspended sediment concentration and light attenuation characteristics were then calculated and spatially averaged to examine how actual cover and mean water depth affect the bulk sediment and light environment. The results indicate that an effective cover, which incorporates the sheltering area, has important controls on the distributions of shear stress, suspended sediment, light environment, and consequent seagrass habitat suitability. Interestingly, an optimal habitat occurs within a depth range where, if actual cover is reduced past some threshold, the bulk light environment would no longer favor seagrass growth.

  4. Spatially explicit feedbacks between seagrass meadow structure, sediment and light: Habitat suitability for seagrass growth

    NASA Astrophysics Data System (ADS)

    Carr, Joel A.; D'Odorico, Paolo; McGlathery, Karen J.; Wiberg, Patricia L.

    2016-07-01

    In shallow coastal bays where nutrient loading and riverine inputs are low, turbidity, and the consequent light environment are controlled by resuspension of bed sediments due to wind-waves and tidal currents. High sediment resuspension and low light environments can limit benthic primary productivity; however, both currents and waves are affected by the presence of benthic plants such as seagrass. This feedback between the presence of benthic primary producers such as seagrass and the consequent light environment has been predicted to induce bistable dynamics locally. However, these vegetated areas influence a larger area than they footprint, including a barren adjacent downstream area which exhibits reduced shear stresses. Here we explore through modeling how the patchy structure of seagrass meadows on a landscape may affect sediment resuspension and the consequent light environment due to the presence of this sheltered region. Heterogeneous vegetation covers comprising a mosaic of randomly distributed patches were generated to investigate the effect of patch modified hydrodynamics. Actual cover of vegetation on the landscape was used to facilitate comparisons across landscape realizations. Hourly wave and current shear stresses on the landscape along with suspended sediment concentration and light attenuation characteristics were then calculated and spatially averaged to examine how actual cover and mean water depth affect the bulk sediment and light environment. The results indicate that an effective cover, which incorporates the sheltering area, has important controls on the distributions of shear stress, suspended sediment, light environment, and consequent seagrass habitat suitability. Interestingly, an optimal habitat occurs within a depth range where, if actual cover is reduced past some threshold, the bulk light environment would no longer favor seagrass growth.

  5. Evolution and vitality of seagrasses in a Mediterranean lagoon.

    PubMed

    Ferrat, Lila; Fernandez, C; Pasqualini, V; Pergent, G; Pergent-Martini, C

    2003-08-01

    Despite their registration on the list of the Ramsar convention sites, the Mediterranean lagoons rarely beneficiate of an effective protection, and are particularly sensitive to environmental quality. A control of these wetlands needs the creation of an inventory of knowledge for the concerned environment. In this perspective, the seagrass beds were followed up in the coastal lagoon of Urbino (Corse, France) since 1990. A cartographic study was carried out by remote sensing of aerial photography. Temporal evolution of the seagrass beds (Cymodocea nodosa principally) allows to determine the vitality of these structures. A comparison of the surface areas occupied by Cymodocea nodosa, between 1990 and 1999, did not allow seeing any significant evolution. However, some variations appear like biotopes all more fragile and coveted as the Mediterranean coastal fringe is straight and is the privileged site of appear in the localization of the beds, due to the modification of environmental conditions in the lagoon.

  6. Seagrasses as indicators for coastal trace metal pollution: a global meta-analysis serving as a benchmark, and a Caribbean case study.

    PubMed

    Govers, Laura L; Lamers, Leon P M; Bouma, Tjeerd J; Eygensteyn, Jelle; de Brouwer, Jan H F; Hendriks, A Jan; Huijbers, Chantal M; van Katwijk, Marieke M

    2014-12-01

    Seagrass beds are highly productive coastal ecosystems providing a large array of ecosystem services including fisheries and carbon sequestration. As seagrasses are known to be highly sensitive to anthropogenic forcing, we evaluated the use of trace metal concentrations in seagrasses as bioindicators for trace metal pollution of coastal regions at both global and local scale. We carried out a meta-analysis based on literature data to provide a global benchmark list for trace metal accumulation in seagrasses, which was lacking in literature. We subsequently carried out a case study at the Caribbean islands of Curaçao and Bonaire to test for local-scale differences in trace metal concentrations in seagrasses, and internal metal allocation. The benchmark and local study show that trace metal concentrations in seagrass leaves, regardless of the species, can vary over a 100-1000-fold range, and are related to the level of anthropogenic pressure, making seagrasses highly valuable indicators.

  7. Seagrass Health Modeling and Prediction with NASA Science Data

    NASA Technical Reports Server (NTRS)

    Robinson, Harold D.; Easson, Greg; Slattery, Marc; Anderson, Daniel; Blonski, Slawomir; DeCurtins, Robert; Underwood, Lauren

    2010-01-01

    Previous research has demonstrated that MODIS data products can be used as inputs into the seagrass productivity model developed by Fong and Harwell (1994). To further explore this use to predict seagrass productivity, Moderate Resolution Imaging Spectroradiometer (MODIS) custom data products, including Sea Surface Temperature, Light Attenuation, and Chlorophyll-a have been created for use as model parameter inputs. Coastal researchers can use these MODIS data products and model results in conjunction with historical and daily assessment of seagrass conditions to assess variables that affect the productivity of the seagrass beds. Current monitoring practices involve manual data collection (typically on a quarterly basis) and the data is often insufficient for evaluating the dynamic events that influence seagrass beds. As part of a NASA-funded research grant, the University of Mississippi, is working with researchers at NASA and Radiance Technologies to develop methods to deliver MODIS derived model output for the northern Gulf of Mexico (GOM) to coastal and environmental managers. The result of the project will be a data portal that provides access to MODIS data products and model results from the past 5 years, that includes an automated process to incorporate new data as it becomes available. All model parameters and final output will be available through the use National Oceanic and Atmospheric Administration?s (NOAA) Environmental Research Divisions Data Access Program (ERDDAP) tools as well as viewable using Thematic Realtime Environmental Distributed Data Services (THREDDS) and the Integrated Data Viewer (IDV). These tools provide the ability to create raster-based time sequences of model output and parameters as well as create graphs of model parameters versus time. This tool will provide researchers and coastal managers the ability to analyze the model inputs so that the factors influencing a change in seagrass productivity can be determined over time.

  8. Seagrass status and trends in the northern Gulf of Mexico: 1940-2002

    USGS Publications Warehouse

    Handley, L.; Altsman, D.; DeMay, R.

    2007-01-01

    Over the past century, seagrass habitats from the bays of Texas to the gulf shores of Florida have decreased. Seagrass beds, which are highly dependent on water quality and clarity for survival, are home to a multitude of aquatic plants and animals and a source of economic activity through commercial and recreational fishing and ecotourism. The U.S. Environmental Protection Agency’s Gulf of Mexico Program (GMP) and its partners have made a commitment to restore, enhance, and protect this important ecosystem. As seagrass habitats decrease, the need for information on the causes and effects of seagrass loss, current mapping information, and education on the importance of seagrassess becomes greater. This report is the initial effort of the GMP’s research and restoration plan for seagrasses. The purpose of this report is to provide scientists, managers, and citizens with valuable baseline information on the status and trends of seagrasses in coastal waters of the Gulf of Mexico. Within the northern Gulf of Mexico region, 14 individual estuarine systems where seagrasses occur, as well as statewide summaries for Texas, Louisiana, Mississippi, Alabama, and Florida, are examined in this study. Each estuarine system is detailed in vignettes that address current and historical extent and quality of seagrasses, seagrass mapping and monitoring, causes of status change, restoration and enhancement activities, background information for the entire study area as well as the subareas for study, and the methodology employed to analyze and document the historical trends and current status of seagrasses. The systems, moving from west to east, include the Laguna Madre, Texas Coastal Bend region, and Galveston Bay in Texas; the Chandeleur Islands in Louisiana; the Mississippi Sound; and Perdido Bay, Pensacola/Escambia Bay, Choctawhatchee Bay, St. Andrew Bay, Florida’s Big Bend region, Tampa Bay/St. Joseph Sound, Sarasota Bay, Greater Charlotte Harbor, and Florida Bay in Florida

  9. Using modelling to predict impacts of sea level rise and increased turbidity on seagrass distributions in estuarine embayments

    NASA Astrophysics Data System (ADS)

    Davis, Tom R.; Harasti, David; Smith, Stephen D. A.; Kelaher, Brendan P.

    2016-11-01

    Climate change induced sea level rise will affect shallow estuarine habitats, which are already under threat from multiple anthropogenic stressors. Here, we present the results of modelling to predict potential impacts of climate change associated processes on seagrass distributions. We use a novel application of relative environmental suitability (RES) modelling to examine relationships between variables of physiological importance to seagrasses (light availability, wave exposure, and current flow) and seagrass distributions within 5 estuarine embayments. Models were constructed separately for Posidonia australis and Zostera muelleri subsp. capricorni using seagrass data from Port Stephens estuary, New South Wales, Australia. Subsequent testing of models used independent datasets from four other estuarine embayments (Wallis Lake, Lake Illawarra, Merimbula Lake, and Pambula Lake) distributed along 570 km of the east Australian coast. Relative environmental suitability models provided adequate predictions for seagrass distributions within Port Stephens and the other estuarine embayments, indicating that they may have broad regional application. Under the predictions of RES models, both sea level rise and increased turbidity are predicted to cause substantial seagrass losses in deeper estuarine areas, resulting in a net shoreward movement of seagrass beds. Seagrass species distribution models developed in this study provide a valuable tool to predict future shifts in estuarine seagrass distributions, allowing identification of areas for protection, monitoring and rehabilitation.

  10. Brevetoxin persistence in sediments and seagrass epiphytes of east Florida coastal waters

    PubMed Central

    Hitchcock, Gary L.; Fourqurean, James W.; Drake, Jeana L.; Mead, Ralph N.; Heil, Cynthia A.

    2012-01-01

    A bloom of Karenia brevis Davis developed in September 2007 near Jacksonville, Florida and subsequently progressed south through east Florida coastal waters and the Atlantic Intracoastal Waterway (ICW). Maximum cell abundances exceeded 106 cells L−1 through October in the northern ICW between Jacksonville and the Indian River Lagoon. The bloom progressed further south during November, and terminated in December 2007 at densities of 104 cells L−1 in the ICW south of Jupiter Inlet, Florida. Brevetoxins were subsequently sampled in sediments and seagrass epiphytes in July and August 2008 in the ICW. Sediment brevetoxins occurred at concentrations of 11–15 ng PbTx-3 equivalents (g dry wt sediment)−1 in three of five basins in the northern ICW during summer 2008. Seagrass beds occur south of the Mosquito Lagoon in the ICW. Brevetoxins were detected in six of the nine seagrass beds sampled between the Mosquito Lagoon and Jupiter Inlet at concentrations of 6–18 ng (g dry wt epiphytes)−1. The highest brevetoxins concentrations were found in sediments near Patrick Air Force Base at 89 ng (g dry wt sediment)−1. In general, brevetoxins occurred in either seagrass epiphytes or sediments. Blades of the resident seagrass species have a maximum life span of less than six months, so it is postulated that brevetoxins could be transferred between epibenthic communities of individual blades in seagrass beds. The occurrence of brevetoxins in east Florida coast sediments and seagrass epiphytes up to eight months after bloom termination supports observations from the Florida west coast that brevetoxins can persist in marine ecosystems in the absence of sustained blooms. Furthermore, our observations show that brevetoxins can persist in sediments where seagrass communities are absent. PMID:23762030

  11. Brevetoxin persistence in sediments and seagrass epiphytes of east Florida coastal waters.

    PubMed

    Hitchcock, Gary L; Fourqurean, James W; Drake, Jeana L; Mead, Ralph N; Heil, Cynthia A

    2012-01-01

    A bloom of Karenia brevis Davis developed in September 2007 near Jacksonville, Florida and subsequently progressed south through east Florida coastal waters and the Atlantic Intracoastal Waterway (ICW). Maximum cell abundances exceeded 10(6) cells L(-1) through October in the northern ICW between Jacksonville and the Indian River Lagoon. The bloom progressed further south during November, and terminated in December 2007 at densities of 10(4) cells L(-1) in the ICW south of Jupiter Inlet, Florida. Brevetoxins were subsequently sampled in sediments and seagrass epiphytes in July and August 2008 in the ICW. Sediment brevetoxins occurred at concentrations of 11-15 ng PbTx-3 equivalents (g dry wt sediment)(-1) in three of five basins in the northern ICW during summer 2008. Seagrass beds occur south of the Mosquito Lagoon in the ICW. Brevetoxins were detected in six of the nine seagrass beds sampled between the Mosquito Lagoon and Jupiter Inlet at concentrations of 6-18 ng (g dry wt epiphytes)(-1). The highest brevetoxins concentrations were found in sediments near Patrick Air Force Base at 89 ng (g dry wt sediment)(-1). In general, brevetoxins occurred in either seagrass epiphytes or sediments. Blades of the resident seagrass species have a maximum life span of less than six months, so it is postulated that brevetoxins could be transferred between epibenthic communities of individual blades in seagrass beds. The occurrence of brevetoxins in east Florida coast sediments and seagrass epiphytes up to eight months after bloom termination supports observations from the Florida west coast that brevetoxins can persist in marine ecosystems in the absence of sustained blooms. Furthermore, our observations show that brevetoxins can persist in sediments where seagrass communities are absent.

  12. Are Seagrass effective Sentinels of Ecosystem Health in Port Phillip Bay, Australia?

    NASA Astrophysics Data System (ADS)

    Lee, R. S.; Cook, P. L. M.; Jenkins, G.; Nayar, S.; Hirst, A.; Keough, M. J.; Smith, T.; Ferguson, A.; Gay, J.; Longmore, A. R.; Macreadie, P.; Sherman, C.; Ross, J.; York, P.

    2016-02-01

    Seagrasses are an important part of many coastal systems, but are also under threat in many areas, as a result of a wide range of human activities, including habitat loss and changes to water quality. Due to these sensitivities seagrass are often selected as sentinels of change for coastal marine ecosystems, but could these sensitivities be too complex and varied to provide a clear or reliable measure of change? A recent three year study focused on the resilience of Zostera seagrasses in Port Phillip Bay, Southern Australia, where these ecosystem "engineers", have a dramatic influence on biodiversity and ecosystem function. This large temperate embayment experiences extreme climatic variability, significant loading from urbanized catchments and inflows from the largest sewage treatment facility in Australia, making it a challenging case study for assessing seagrass as a suitable ecosystem metric. Studies on the influence of nutrients, light and sediments using modelling, chemical analyses and field experiments assessed characteristics of Zostera habitat within the bay. Nutrients could be obtained directly in dissolved form from the water column, or sediment, or as atmospheric nitrogen fixed by bacteria associated with the root/rhizome system. Isotopic nutrients were traced to a variety of sources including river inflows, sewage discharges, groundwater, the open ocean, the atmosphere and indirectly via phytoplankton and detritus. Broad-scale seagrass coverage is often depth limited by light, however for regions of significant wave exposure deeper beds existed adjacent to less favorable shallows. Ephemeral beds in more exposed regions showed the greatest potential for responding to change. For these beds, resilience was dependent on bed architecture, connectivity to indirect nutrient sources, and genetic interactions with seagrass communities around the bay. While observed changes in seagrass cover may be a symptomatic trigger of ecosystem health, much as high blood

  13. Food-Web Structure of Seagrass Communities across Different Spatial Scales and Human Impacts

    PubMed Central

    Coll, Marta; Schmidt, Allison; Romanuk, Tamara; Lotze, Heike K.

    2011-01-01

    Seagrass beds provide important habitat for a wide range of marine species but are threatened by multiple human impacts in coastal waters. Although seagrass communities have been well-studied in the field, a quantification of their food-web structure and functioning, and how these change across space and human impacts has been lacking. Motivated by extensive field surveys and literature information, we analyzed the structural features of food webs associated with Zostera marina across 16 study sites in 3 provinces in Atlantic Canada. Our goals were to (i) quantify differences in food-web structure across local and regional scales and human impacts, (ii) assess the robustness of seagrass webs to simulated species loss, and (iii) compare food-web structure in temperate Atlantic seagrass beds with those of other aquatic ecosystems. We constructed individual food webs for each study site and cumulative webs for each province and the entire region based on presence/absence of species, and calculated 16 structural properties for each web. Our results indicate that food-web structure was similar among low impact sites across regions. With increasing human impacts associated with eutrophication, however, food-web structure show evidence of degradation as indicated by fewer trophic groups, lower maximum trophic level of the highest top predator, fewer trophic links connecting top to basal species, higher fractions of herbivores and intermediate consumers, and higher number of prey per species. These structural changes translate into functional changes with impacted sites being less robust to simulated species loss. Temperate Atlantic seagrass webs are similar to a tropical seagrass web, yet differed from other aquatic webs, suggesting consistent food-web characteristics across seagrass ecosystems in different regions. Our study illustrates that food-web structure and functioning of seagrass habitats change with human impacts and that the spatial scale of food-web analysis

  14. Food-web structure of seagrass communities across different spatial scales and human impacts.

    PubMed

    Coll, Marta; Schmidt, Allison; Romanuk, Tamara; Lotze, Heike K

    2011-01-01

    Seagrass beds provide important habitat for a wide range of marine species but are threatened by multiple human impacts in coastal waters. Although seagrass communities have been well-studied in the field, a quantification of their food-web structure and functioning, and how these change across space and human impacts has been lacking. Motivated by extensive field surveys and literature information, we analyzed the structural features of food webs associated with Zostera marina across 16 study sites in 3 provinces in Atlantic Canada. Our goals were to (i) quantify differences in food-web structure across local and regional scales and human impacts, (ii) assess the robustness of seagrass webs to simulated species loss, and (iii) compare food-web structure in temperate Atlantic seagrass beds with those of other aquatic ecosystems. We constructed individual food webs for each study site and cumulative webs for each province and the entire region based on presence/absence of species, and calculated 16 structural properties for each web. Our results indicate that food-web structure was similar among low impact sites across regions. With increasing human impacts associated with eutrophication, however, food-web structure show evidence of degradation as indicated by fewer trophic groups, lower maximum trophic level of the highest top predator, fewer trophic links connecting top to basal species, higher fractions of herbivores and intermediate consumers, and higher number of prey per species. These structural changes translate into functional changes with impacted sites being less robust to simulated species loss. Temperate Atlantic seagrass webs are similar to a tropical seagrass web, yet differed from other aquatic webs, suggesting consistent food-web characteristics across seagrass ecosystems in different regions. Our study illustrates that food-web structure and functioning of seagrass habitats change with human impacts and that the spatial scale of food-web analysis

  15. Community structure and biomass distribution of seagrasses and macrofauna in the flores sea, Indonesia

    NASA Astrophysics Data System (ADS)

    Nienhuis, P. H.; Coosen, J.; Kiswara, W.

    In several locations in the Flores Sea region the community structure and the biomass distribution of seagrasses were studied along transects perpendicular to the shoreline. The share of each species within a sample plot was estimated, divided in above- and below-ground biomass. Statistics regarding substrate coverage, shoot density and leaf-area index were sampled. A standard relation was calculated between seagrass dry weight, ash-free dry weight and organic carbon content. The biotic data were related to environmental factors: DOC and nutrients in the water, salinity, tidal amplitude, sediment composition. A relation was estimated between bottom coverage of seagrasses and standing stock. Further calculations of biomass-production ratios allow a quick and rough estimate of seagrass productivity. Maximum above-ground biomass values (500-700 g AFDW·m -2) together with qualitative data indicate resource (= space) partitioning among the component seagrasses within a community, and suggest a carrying capacity of the reefflat habitat for seagrass density and biomass. A tentative model was constructed, starting from a constant, non-distributed multispecies vegetation in the lower intertidal and subtidal zone on sand and coral rubble, and moving into several suboptimal situations. The upper shore carries an impoverished, constrained vegetation (irregular tides, desiccation, harvesting). Sediment reworking by animals and physical displacement of sand disturbs the vegetation and favours pioneer species. Muddy habitats bordering mangroves carry monospecific stands showing extremely high biomass ( e.g. below-ground Enhalus acoroides 3500 g AFDW·m -2). Thalassia hemprichii and Enhalus acoroides are the most constant species in all habitats mentioned. Macrofauna biomass within the seagrass beds fluctuated widely (maximum values 50-70 g AFDW·m -2 in mixed seagrass vegetations) and only a weak relation between benthic macrofauna biomass and seagrass community structure and

  16. The short-term impacts of a cyclone on seagrass communities in Southwest Madagascar

    NASA Astrophysics Data System (ADS)

    Côté-Laurin, Marie-Claude; Benbow, Sophie; Erzini, Karim

    2017-04-01

    Cyclones are large-scale disturbances with highly destructive potential in coastal ecosystems. On February 22, 2013, a powerful tropical cyclone made landfall on the southwest coast of Madagascar, a region which is infrequently hit by such extreme weather events coming from the Mozambique Channel. Seagrass ecosystems, which provide valuable ecosystems services to local communities, are especially vulnerable because they thrive in shallow waters. The impact of Cyclone Haruna on seagrass diversity, height and coverage and associated fish diversity, abundance and biomass was assessed in 3 sites near Andavadoaka (22°07‧S, 43°23‧E) before and after the event using fish underwater visual census, video-transects, and seagrass quadrats. The cyclone caused a significant loss in seagrass cover at all 3 sites. Thalassia hemprichii and Syringodium isoetifolium were the most affected species. Andavadoaka beach, the most exposed site, which was also subject to human use and was most fragmented, suffered the largest negative effects of the cyclone. Cyclone Haruna was not found to significantly affect fish assemblages, which are highly mobile organisms able to use a diversity of niches and adjacent habitats after seagrass fragmentation. Extensive sampling and longer time-scale studies would be needed to fully evaluate the cyclone impact on communities of seagrass and fish, and track potential recovery in seagrass coverage. The intensity and destructive potential of cyclones is expected to increase with global warming, which is of concern for developing countries that encompass most of the world's seagrass beds. This study provided a unique and key opportunity to monitor immediate impacts of an extreme disturbance in a region where cyclones rarely hit coastal ecosystems and where local populations remain highly dependent on seagrass meadows.

  17. Causes of seasonal and decadal variability in a tropical seagrass seascape (Reunion Island, south western Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Cuvillier, A.; Villeneuve, N.; Cordier, E.; Kolasinski, J.; Maurel, L.; Farnier, N.; Frouin, P.

    2017-01-01

    While seagrass meadows are considered as vulnerable or declining habitats worldwide, facing many natural and anthropogenic pressures, the opposite trend is suggested by this study in Reunion Island (Indian Ocean). Located at the benthos-pelagos interface, seagrass beds are critical coastal habitats and can be used as relevant health indicators for larger marine ecosystems or land-sea continuum. In order to determine which are the factors driving seagrass ecosystems health it is essential to quantify their seascape pattern fluctuations. The long-term (over 65 years) and seasonal scale variability was assessed in the monospecific Syringodium isoetifolium seagrass bed seascape at the Ermitage/La Saline fringing reef using aerial photographs and field measurements. Both long-term and short-term scales have been informative and both types of monitoring appear as useful tools for seagrass ecosystem management. Strong variations in seagrass coverage were observed in the 16 rasters analyzed from years 1950-2015, the magnitude order was however similar to the one observed at the recent seasonal scale (up to 2016 m2 gained or 4863 m2 lost over few months at site scale). Seascape pattern analysis revealed that physical factors (swell events, cyclones) had a major impact on the ocean-exposed site with varying impact degree depending on frequency, duration and intensity. Biotic (herbivory) or anthropogenic (grubbing, nutrient inputs) factors were also identified to influence the structural shape, fragmentation, or disappearance of seagrass beds. Further work is required to better quantify the effect of each single factor, a difficult task due to their combined expression. At the reef scale, these results showed a positive correlation between seagrass beds and inner reef flat coverage suggesting that common factors drive these highly resilient ecosystems.

  18. Modification of animal habitat by large plants: mechanisms by which seagrasses influence clam growth.

    PubMed

    Irlandi, E A; Peterson, C H

    1991-09-01

    Field experiments withMercenaria mercenaria in a relatively high-energy environment demonstrated that clams on unvegetated sand flats failed to grow during autumn while those within seagrass beds grew substantially. Clam growth rates at the seagrass margin that first receives the faster-flowing, flood-tidal currents were about 25% less than at the opposite edge. In a second experiment, pruning, which reduced average blade length by 50-75%, was shown to enhance near-bottom current velocities and to reduce shell growth ofMercenaria during summer by about 50%. As in the first experiment, clams in the unvegetated sand flats exhibited no net growth. Clam mortality, caused mostly by predatory crabs and whelks, was much higher on sand flats than in seagrass beds and intermediate in clipped seagrass. Although consistent with some previous reports, these growth results are still surprising given that they contradict the generalization that suspension feeders grow faster under more rapid current regimes.Three types of indirect interactions might explain the observed effect of seagrass on growth of buried clams: (1) altering food supply; (2) changing the intensity of biological disturbance on feeding clams; and/or (3) affecting the physical stability of the sediments. Previous research on this question has focused almost exclusively on processes that alter food supply rates. In this study, food concentrations, as indicated by suspended chla, were 30% higher inside than outside one seagrass bed, whereas chla concentrations in two other beds were not different from those on adjacent sand flats. This result is sufficient to show that more intense food depletion was not induced by the reduction in flow velocities under the seagrass canopy. Nevertheless, the possible small difference in food concentrations between vegetated and unvegetated bottom seems insufficient to explain the absence of growth of sand-flat clams, especially given the virtual lack of food limitation among

  19. Seagrass colonization: Knock-on effects on zoobenthic community, populations and individual health

    NASA Astrophysics Data System (ADS)

    Tu Do, V.; de Montaudouin, Xavier; Lavesque, Nicolas; Blanchet, Hugues; Guyard, Hervé

    2011-12-01

    This study provided evidence that Zostera noltii presence affects macrofauna community structure independently from median sediment grain-size and that the notion of ecosystem health is rather subjective: in the present case, we recorded "good health" in terms of seagrass development, "no impact" in terms of macrobenthic biotic indices and "negative effect" for a given key-population. The occurrence and development of a Z. noltii seagrass bed was surveyed at Banc d'Arguin, Arcachon Bay (France), to estimate the modification of the macrozoobenthic community and of the dynamics of a key-population for the local ecosystem, - the cockle Cerastoderma edule. Even though median grain-size of the sediment decreased only at the very end of the survey, i.e. when seagrass totally invaded the area, most of the macrofauna community characteristics (such as abundance and biomass) increased as soon as Z. noltii patches appeared. The structure of the macrofauna community also immediately diverged between sand and seagrass habitats, without however modifying the tested biotic indices (BENTIX, BOPA, AMBI). The health of the cockle population (growth, abundance, recruitment) was impacted by seagrass development. Related parasite communities slowly diverged between habitats, with more parasites in the cockles from seagrass areas. However, the number of parasites per cockle was always insufficient to alter cockle fitness.

  20. Recurrence of Seagrass Mortality in Florida Bay: The Role of Climate Change and Implications for Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Yarbro, L.; Carlson, P. R., Jr.

    2016-02-01

    Catastrophic mortality of seagrass in Florida Bay (USA) from 1987 to 1991 resulted in the complete loss of thousands of hectares of dense Thalassia testudinum beds. At that time, acutely toxic levels of dissolved sulfide in sediments were determined to be the proximal cause of seagrass mortality, but the mechanisms responsible for sulfide accumulation in sediments were not demonstrated. With the recurrence of seagrass mortality in Florida Bay in summer 2015, we show that several processes create the conditions that lead to sulfide toxicity and catastrophic mortality of Thalassia. Regional drought and elevated water temperature lead to hypersalinity, particularly in the northern Bay. In addition, evaporation of seawater on mudbanks and microtidal flow patterns create stratified brine layers in basins adjacent to mudbanks. Because of very high seagrass shoot densities and limited tidal exchange, brine layers limit oxygen diffusion and prevent oxidation of sulfide in sediments and bottom water, exposing roots, rhizomes and lateral meristems of Thalassia to acutely toxic levels of sulfide, causing extensive mortality. Dead belowground tissues provide labile carbon sources to sulfate-reducing bacteria enhancing sulfide production and creating a positive feedback loop of increasing sulfide toxicity leading to further seagrass death. The carbon sequestration capacity of these dense seagrass communities is diminished three ways: 1) export of dead seagrass shoots and leaves as floating wrack, 2) in situ decomposition of roots, rhizomes, and some leaf material, and 3) reduced areal productivity of surviving seagrasses. Climate analyses show that, in the short term ( 50 years), higher water temperatures and evaporation rates might result in recurring seagrass mortality events. However, in the long term, sea level rise will increase tidal exchange and flushing in Florida Bay reducing the likelihood of seagrass mortality.

  1. Recovery of floral and faunal communities after placement of dredged material on seagrasses in Laguna Madre, Texas

    NASA Astrophysics Data System (ADS)

    Sheridan, P.

    2004-03-01

    The objectives of this project were to determine how long alterations in habitat characteristics and use by fishery and forage organisms were detectable at dredged material placement sites in Laguna Madre, Texas. Water, sediment, seagrass, benthos, and nekton characteristics were measured and compared among newly deposited sediments and nearby and distant seagrasses each fall and spring over three years. Over this period, 75% of the estimated total surface area of the original deposits was either re-vegetated by seagrass or dispersed by winds and currents. Differences in water and sediment characteristics among habitat types were mostly detected early in the study. There were signs of steady seagrass re-colonization in the latter half of the study period, and mean seagrass coverage of deposits had reached 48% approximately three years after dredging. Clovergrass Halophila engelmannii was the initial colonist, but shoalgrass Halodule wrightii predominated after about one year. Densities of annelids and non-decapod crustaceans were generally significantly greater in close and distant seagrass habitats than in dredged material habitat, whereas densities of molluscs were not significantly related to habitat type. Nekton (fish and decapod) densities were almost always significantly greater in the two seagrass habitats than in dredged material deposits. Benthos and nekton communities in dredged material deposits were distinct from those in seagrass habitats. Recovery from dredged material placement was nearly complete for water column and sediment components after 1.5 to 3 years, but recovery of seagrasses, benthos, and nekton was predicted to take 4 to 8 years. The current 2 to 5 years dredging cycle virtually insures no time for ecosystem recovery before being disturbed again. The only way to ensure permanent protection of the high primary and secondary productivity of seagrass beds in Laguna Madre from acute and chronic effects of maintenance dredging, while ensuring

  2. Eutrophication threatens Caribbean seagrasses - An example from Curaçao and Bonaire.

    PubMed

    Govers, Laura L; Lamers, Leon P M; Bouma, Tjeerd J; de Brouwer, Jan H F; van Katwijk, Marieke M

    2014-12-15

    Seagrass beds are globally declining due to human activities in coastal areas. We here aimed to identify threats from eutrophication to the valuable seagrass beds of Curaçao and Bonaire in the Caribbean, which function as nursery habitats for commercial fish species. We documented surface- and porewater nutrient concentrations, and seagrass nutrient concentrations in 6 bays varying in nutrient loads. Water measurements only provided a momentary snapshot, due to timing, tidal stage, etc., but Thalassia testudinum nutrient concentrations indicated long-term nutrient loads. Nutrient levels in most bays did not raise any concern, but high leaf % P values of Thalassia in Piscadera Bay (∼0.31%) and Spanish Water Bay (∼0.21%) showed that seagrasses may be threatened by eutrophication, due to emergency overflow of waste water and coastal housing. We thus showed that seagrasses may be threatened and measures should be taken to prevent loss of these important nursery areas due to eutrophication. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Decreasing seagrass density negatively influences associated fauna.

    PubMed

    McCloskey, Rosemary M; Unsworth, Richard K F

    2015-01-01

    Seagrass meadows globally are disappearing at a rapid rate with physical disturbances being one of the major drivers of this habitat loss. Disturbance of seagrass can lead to fragmentation, a reduction in shoot density, canopy height and coverage, and potentially permanent loss of habitat. Despite being such a widespread issue, knowledge of how such small scale change affects the spatial distribution and abundances of motile fauna remains limited. The present study investigated fish and macro faunal community response patterns to a range of habitat variables (shoot length, cover and density), including individual species habitat preferences within a disturbed and patchy intertidal seagrass meadow. Multivariate analysis showed a measurable effect of variable seagrass cover on the abundance and distribution of the fauna, with species specific preferences to both high and low seagrass cover seagrass. The faunal community composition varied significantly with increasing/decreasing cover. The faunal species composition of low cover seagrass was more similar to sandy control plots than to higher cover seagrass. Shannon Wiener Diversity (H') and species richness was significantly higher in high cover seagrass than in low cover seagrass, indicating increasing habitat value as density increases. The results of this study underline how the impacts of small scale disturbances from factors such as anchor damage, boat moorings and intertidal vehicle use on seagrass meadows that reduce shoot density and cover can impact upon associated fauna. These impacts have negative consequences for the delivery of ecosystem services such as the provision of nursery habitat.

  4. Decreasing seagrass density negatively influences associated fauna

    PubMed Central

    McCloskey, Rosemary M.

    2015-01-01

    Seagrass meadows globally are disappearing at a rapid rate with physical disturbances being one of the major drivers of this habitat loss. Disturbance of seagrass can lead to fragmentation, a reduction in shoot density, canopy height and coverage, and potentially permanent loss of habitat. Despite being such a widespread issue, knowledge of how such small scale change affects the spatial distribution and abundances of motile fauna remains limited. The present study investigated fish and macro faunal community response patterns to a range of habitat variables (shoot length, cover and density), including individual species habitat preferences within a disturbed and patchy intertidal seagrass meadow. Multivariate analysis showed a measurable effect of variable seagrass cover on the abundance and distribution of the fauna, with species specific preferences to both high and low seagrass cover seagrass. The faunal community composition varied significantly with increasing/decreasing cover. The faunal species composition of low cover seagrass was more similar to sandy control plots than to higher cover seagrass. Shannon Wiener Diversity (H′) and species richness was significantly higher in high cover seagrass than in low cover seagrass, indicating increasing habitat value as density increases. The results of this study underline how the impacts of small scale disturbances from factors such as anchor damage, boat moorings and intertidal vehicle use on seagrass meadows that reduce shoot density and cover can impact upon associated fauna. These impacts have negative consequences for the delivery of ecosystem services such as the provision of nursery habitat. PMID:26137432

  5. Relative velocity of seagrass blades: Implications for wave attenuation in low-energy environments

    NASA Astrophysics Data System (ADS)

    Bradley, Kevin; Houser, Chris

    2009-03-01

    While the ability of subaquatic vegetation to attenuate wave energy is well recognized in general, there is a paucity of data from the field to describe the rate and mechanisms of wave decay, particularly with respect to the relative motion of the vegetation. The purpose of this study was to quantify the attenuation of incident wave height through a seagrass meadow and characterize the blade movement under oscillatory flow under the low-energy conditions characteristic of fetch-limited and sheltered environments. The horizontal motion of the seagrass blades and the velocity just above the seagrass canopy were measured using a digital video camera and an acoustic Doppler velicometer (ADV) respectively in order to refine the estimates of the drag coefficient based on the relative velocity. Significant wave heights (Hs) were observed to increase by ˜0.02 m (˜20%) through the first 5 m of the seagrass bed but subsequently decrease exponentially over the remainder of the bed. The exponential decay coefficient varied in response to the Reynolds number calculated using blade width (as the length scale) and the oscillatory velocity measured immediately above the canopy. The ability of the seagrass to attenuate wave energy decreases as incident wave heights increase and conditions become more turbulent. Estimates of the time-averaged canopy height and the calculated hydraulic roughness suggest that, as the oscillatory velocity increases, the seagrass becomes fully extended and leans in the direction of flow for a longer part of the wave cycle. The relationship between the drag coefficient and the Reynolds number further suggests that the vegetation is swaying (going with the flow) at low-energy conditions but becomes increasingly rigid as oscillatory velocities increase over the limited range of the conditions observed (200 < Re < 800). In addition to the changing behavior of the seagrass motion, the attenuation was not uniform with wave frequency, and waves at a

  6. Distribution of fish in seagrass, mangroves and coral reefs: life-stage dependent habitat use in Honduras.

    PubMed

    Jaxion-Harm, Jessica; Saunders, James; Speight, Martin R

    2012-06-01

    Many coral reef fish exhibit habitat partitioning throughout their lifetimes. Such patterns are evident in the Caribbean where research has been predominantly conducted in the Eastern region. This work addressed the paucity of data regarding Honduran reef fish distribution in three habitat types (seagrass, mangroves, and coral reefs), by surveying fish on the islands of Utila and Cayos Cochinos off the coast of Honduras (part of the Mesoamerican barrier reef). During July 2nd - Aug 27th 2007 and June 22nd - Aug 17th, 2008, visual surveys (SCUBA and snorkel) were performed in belt transects in different areas: eleven coral reef, six seagrass beds, and six mangroves sites. Juvenile densities and total habitat surface area were used to calculate nursery value of seagrass and mangroves. A total of 113 fish species from 32 families were found during underwater surveys. Multi-dimensional analyses revealed distinct clusters of fish communities in each habitat type by separating fish associated with seagrass beds, mangroves, and coral reefs. Coral reefs showed the highest mean fish species richness and were dominated by adult fish, while juvenile fish characterized seagrass beds and mangrove sites. Habitat use differed widely at the fish species level. Scarus iseri (Striped Parrotfish), the most abundant fish in this study, were found in all three habitat types, while Lutjanus apodus (Schoolmaster Snapper) juveniles were located primarily in mangroves before migrating to coral reefs. Many species used seagrass beds and mangroves as nurseries; however, the nursery value could not be generalized at the family level. Furthermore, for some fish species, nursery value varied between islands and sites. Our results suggest that connectivity of seagrass, mangrove, and coral reef sites at a species and site levels, should be taken into consideration when implementing policy and conservation practices.

  7. INTRACELLULAR COLONIZATION OF SEAGRASS ROOTS BY ACETOGENIC AND SULFIDOGENIC BACTERIA

    EPA Science Inventory

    The contribution of seagrasses to the stability and fertility of estuarine ecosystems is well established. Loss of seagrasses in recent years to disease and coastal development underscores the importance of understanding the microbial ecology of seagrasses, and the possible roles...

  8. INTRACELLULAR COLONIZATION OF SEAGRASS ROOTS BY ACETOGENIC AND SULFIDOGENIC BACTERIA

    EPA Science Inventory

    The contribution of seagrasses to the stability and fertility of estuarine ecosystems is well established. Loss of seagrasses in recent years to disease and coastal development underscores the importance of understanding the microbial ecology of seagrasses, and the possible roles...

  9. Are Estimates of Blue Carbon Sequestration by Seagrass Sediments Biased High?

    NASA Astrophysics Data System (ADS)

    Johannessen, S.

    2016-02-01

    Coastal marine sediments bury organic carbon, sequestering atmospheric carbon dioxide. Vegetated coastal ecosystems, including seagrass beds, are thought to sequester carbon disproportionately for their size, making it essential to itemize them in global carbon models, and implying that restoration or protection offers the potential to obtain carbon credits. International protocols have been developed to evaluate carbon capture by seagrass beds, based on local or global studies in semi-terrestrial systems. However, these methods generally do not account for the behaviour of marine sediments. Sedimentation rate, sediment mixing, microbial degradation, and the energy of the environment all affect the burial of organic carbon in the ocean. Neglecting these factors tends to overestimate sequestration by seagrasses, and, in addition, results in an incorrect spatial distribution of carbon burial. We will describe how marine sediments process and bury organic carbon; present a direct and reliable method to determine carbon burial, suitable for international Tier 3 reporting; and discuss the implications for global estimates of carbon sequestration by seagrass beds.

  10. NASA Satellite Data for Seagrass Health Modeling and Monitoring

    NASA Technical Reports Server (NTRS)

    Spiering, Bruce A.; Underwood, Lauren; Ross, Kenton

    2011-01-01

    Time series derived information for coastal waters will be used to provide input data for the Fong and Harwell model. The current MODIS land mask limits where the model can be applied; this project will: a) Apply MODIS data with resolution higher than the standard products (250-m vs. 1-km). b) Seek to refine the land mask. c) Explore nearby areas to use as proxies for time series directly over the beds. Novel processing approaches will be leveraged from other NASA projects and customized as inputs for seagrass productivity modeling

  11. Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

    NASA Astrophysics Data System (ADS)

    Armitage, A. R.; Fourqurean, J. W.

    2016-01-01

    The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50-100 %. Soil carbon content slightly decreased ( ˜ 10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen : phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded an approximate threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m-2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

  12. Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

    NASA Astrophysics Data System (ADS)

    Armitage, A. R.; Fourqurean, J. W.

    2015-10-01

    The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50-100 %. Soil carbon content slightly decreased (~ 10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen: phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded a threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m-2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

  13. Seagrass blue carbon spatial patterns at the meadow-scale

    PubMed Central

    Oreska, Matthew P. J.; McGlathery, Karen J.; Porter, John H.

    2017-01-01

    Most information on seagrass carbon burial derives from point measurements, which are sometimes scaled by meadow area to estimate carbon stocks; however, sediment organic carbon (Corg) concentrations may vary with distance from the meadow edge, resulting in spatial gradients that affect the accuracy of stock estimates. We mapped sediment Corg concentrations throughout a large (6 km2) restored seagrass meadow to determine whether Corg distribution patterns exist at different spatial scales. The meadow originated from ≤1-acre plots seeded between 2001 and 2004, so we expected Corg to vary spatially according to the known meadow age at sample sites and with proximity to the meadow edge. Applying spatial autoregressive models allowed us to control for spatial autocorrelation and quantify the relative effects of edge proximity and age on Corg concentrations. We found that edge proximity, not age, significantly predicted the meadow-scale Corg distribution. We also evaluated relationships between Corg and a variety of specific explanatory variables, including site relative exposure, shoot density, sediment grain size, and bathymetry. Factors known to affect carbon burial at the plot-scale, such as meadow age and shoot density, were not significant controls on the meadow-scale Corg distribution. Strong correlations between Corg, grain size, and edge proximity suggest that current attenuation increases fine-sediment deposition and, therefore, carbon burial with distance into the meadow. By mapping the sediment Corg pool, we provide the first accurate quantification of an enhanced carbon stock attributable to seagrass restoration. The top 12 cm of the bed contain 3660 t Corg, approximately 1200 t more Corg than an equal area of bare sediment. Most of that net increase is concentrated in a meadow area with low tidal current velocities. Managers should account for the effects of meadow configuration and current velocity when estimating seagrass blue carbon stocks. Our

  14. Seagrass blue carbon spatial patterns at the meadow-scale.

    PubMed

    Oreska, Matthew P J; McGlathery, Karen J; Porter, John H

    2017-01-01

    Most information on seagrass carbon burial derives from point measurements, which are sometimes scaled by meadow area to estimate carbon stocks; however, sediment organic carbon (Corg) concentrations may vary with distance from the meadow edge, resulting in spatial gradients that affect the accuracy of stock estimates. We mapped sediment Corg concentrations throughout a large (6 km2) restored seagrass meadow to determine whether Corg distribution patterns exist at different spatial scales. The meadow originated from ≤1-acre plots seeded between 2001 and 2004, so we expected Corg to vary spatially according to the known meadow age at sample sites and with proximity to the meadow edge. Applying spatial autoregressive models allowed us to control for spatial autocorrelation and quantify the relative effects of edge proximity and age on Corg concentrations. We found that edge proximity, not age, significantly predicted the meadow-scale Corg distribution. We also evaluated relationships between Corg and a variety of specific explanatory variables, including site relative exposure, shoot density, sediment grain size, and bathymetry. Factors known to affect carbon burial at the plot-scale, such as meadow age and shoot density, were not significant controls on the meadow-scale Corg distribution. Strong correlations between Corg, grain size, and edge proximity suggest that current attenuation increases fine-sediment deposition and, therefore, carbon burial with distance into the meadow. By mapping the sediment Corg pool, we provide the first accurate quantification of an enhanced carbon stock attributable to seagrass restoration. The top 12 cm of the bed contain 3660 t Corg, approximately 1200 t more Corg than an equal area of bare sediment. Most of that net increase is concentrated in a meadow area with low tidal current velocities. Managers should account for the effects of meadow configuration and current velocity when estimating seagrass blue carbon stocks. Our

  15. The protection of sandy shores - Can we afford to ignore the contribution of seagrass?

    PubMed

    Paul, Maike

    2017-08-15

    Shore nourishment is considered an effective soft coastal protection measure for sandy shorelines. However, sand demand and costs are high, especially as nourishment has to be repeated regularly due to ongoing erosion. Seagrass meadows are able to trap and stabilise sediment by reducing bed shear stress. Moreover, they reduce flow velocity and wave energy in regions beyond their boundaries. Especially small species may not provide these ecosystem services sufficiently to protect shorelines from erosion, but they may stabilise beach profiles enough to increase nourishment intervals. This review discusses the potential benefits of integrating ecosystem services provided by seagrass meadows, both existing and newly planted, in nourishment plans, and also addresses potential limitations such as unsuitable hydrodynamic conditions and seasonality. Finally, it highlights knowledge gaps that should be addressed by interdisciplinary research to improve nourishment plans and use seagrass ecosystem services to their full potential. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. [Hurricane Paloma's effects on seagrasses along Jardines de la Reina Archipelago, Cuba].

    PubMed

    Guimarais, Mayrene; Zúñiga, Adán; Pina, Fabián; Matos, Felipe

    2013-09-01

    Seagrasses are one of the most important coastal ecosystems since they promote organic matter flow, nutrient cycling, food availability and refuge. Until now, reports on damages caused by storms and hurricanes on seagrass beds are uncommon and highly variable. The seagrass meadows of the East end of Jardines de la Reina archipelago were surveyed from Nov. 29th to Dec. 5th of 2008, in order to determinate the effects from the passing of Hurricane Paloma: a category three storm on the Saffir-Simpsom scale. A rapid field assessment of the affected areas was carried out using the manta tow technique. In six sites, seagrass was quantitatively evaluated using a 15cm diameter core (four sampling units per site) and shoot density was calculated. Remote sensing techniques were used to estimate seagrass cover. To estimate the percentage of affected areas, a Region of Interest (ROI) was first created over a Landsat image. The percentage of seagrass affected within the ROI was estimated through direct georeferentiation of the contours of the damaged area and with a comparison to the total seagrass extension. To find possible explanations for damages, a false colour image was created using the near infrared band, to highlight the differences between emerged and submerged zones. The direction of winds was estimated using ArcGis 9.2 creating circular buffers, from the centre of the hurricane and generating lines tangent to the buffers. Seagrass in the region was dominated by the angiosperm Thalassia testudinum. Regional mean density was 1 321 +/- 721 shoots/m2, a value regarded as high for the Caribbean area. Seagrass meadows were partly affected by sediment accumulation on the shoots of T. testudinum and uprooting rhizomes. The 7.6 km2 disturbed area represented 1% of the total seagrass area. Other sites, closer to the centre of the hurricane, did not show any damages on the marine vegetation. The keys location with respect to the hurricane track was the most likely cause of the

  17. Seasonality in vegetation biometrics and its effects on sediment characteristics and meiofauna in Baltic seagrass meadows

    NASA Astrophysics Data System (ADS)

    Jankowska, Emilia; Włodarska-Kowalczuk, Maria; Kotwicki, Lech; Balazy, Piotr; Kuliński, Karol

    2014-02-01

    Seagrass meadows can act as ecosystem engineers, i.e., organisms that modify the availability of resources to other organisms. However, their possible positive impacts depend on the characteristics of the vegetation, and these can vary strongly seasonally. This study assesses seasonal variability in macrophyte taxonomic composition and seagrass biometrics in the temperate Baltic Sea eelgrass meadows. We hypothesize that the anticipated strong seasonality in vegetation cover induces parallel seasonal changes in seagrass engineering effects as indicated by changes in sediment characteristics and meiozoobenthic abundance, composition and diversity. Macrophytes, sediments, and fauna were sampled at two locations in the Puck Bay from vegetated bottoms and bare sands five times in one year. Zostera marina vegetation occurred throughout the year and showed strong seasonality with the highest values of shoot density, leaf length, and biomass in July (202.3 ± 30.0 95% CI shoots m-2) and the lowest in March (55.4 ± 15.0 shoots m-2). POC was significantly higher in vegetated sands, and these effects were evident throughout the study period regardless of variability in macrophyte vegetation. The density and diversity of meiofauna did not differ between the seagrass beds and bare sands even in summer months when vegetation was best developed. The lack of an effect of the seagrass meadows on the meiofauna can be explained by the relatively low shoot density and biomass of the studied seagrass meadows and/or higher macrobenthic predation on the vegetated bottom compared to bare sands. However, both the canopies of macrophytes and the effects of the vegetation on benthic systems could increase substantially over the course of the gradual, natural restoration of the seagrass meadows.

  18. Ecological structure and function differs between habitats dominated by seagrasses and green seaweeds.

    PubMed

    Tuya, Fernando; Png-Gonzalez, Lydia; Riera, Rodrigo; Haroun, Ricardo; Espino, Fernando

    2014-07-01

    Marine vegetated habitats, e.g. seagrass meadows, deliver essential functions and services to coastal ecosystems and human welfare. Impacts induced by humans, however, have facilitated the replacement of seagrasses by alternative vegetation, e.g. green rhizophytic seaweeds. The implications of habitat shifts for ecosystem attributes and processes and the services they deliver remain poorly known. In this study, we compared ecosystem structure and function between Cymodocea nodosa seagrass meadows and bottoms dominated by Caulerpa prolifera, a green, native, rhizophytic seaweed, through 5 ecological proxies: (i) primary production (via community metabolism), (ii) composition and abundance of epifauna (a proxy for provision of habitat for epifauna), composition and abundance of (iii) small-sized (juvenile) and (iv) large-sized (adult) fishes (proxies for provision of habitat for fishes), and (v) sediment retention (a proxy for sediment stabilization). Four of these proxies were greater in C. nodosa seagrass meadows than in C. prolifera beds: gross primary productivity (∼1.4 times), the total abundance, species density and biomass of small-sized fishes (∼2.1, 1.3 and 1.3 times, respectively), the total abundance and species density of large-sized fishes (∼3.6 and 1.5 times, respectively), and sediment stabilization (∼1.4 times). In contrast, the total abundance and species density of epifauna was larger (∼3.1 and 1.7 times, respectively) in C. prolifera than in C. nodosa seagrass beds. These results suggest that ecosystem structure and function may differ if seagrasses are replaced by green rhizophytic seaweeds. Importantly, ecosystem functions may not be appropriate surrogates for one another. As a result, assessments of ecosystem services associated with ecosystem functions cannot be based on exclusively one service that is expected to benefit other services. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Comparison of zooplankton abundance and community in seagrass and non-seagrass areas of Merambong shoal

    NASA Astrophysics Data System (ADS)

    Azmi, Afiq Auji; Yoshida, Teruaki; Toda, Tatsuki; Ross, Othman bin Haji; Cob, Zaidi Che

    2016-11-01

    A zooplankton comparison study of Merambong shoal's seagrass and non-seagrass area was conducted from April 2013 to October 2014. Sampling was conducted monthly at fixed stations by horizontal tows of a 140 µm plankton net. Mean temperature was significantly higher during the south-west (SW) monsoon at both stations. Salinity and Chlorophyll a concentrations were not significantly different between the monsoons for both stations. However, Chlorophyll a concentrations were significantly higher in the seagrass compared to non-seagrass station. Mean zooplankton abundance was 1.32-fold higher in the non-seagrass area (4006.5±1990.5 ind/mł) than the seagrass area (3030.1± 855.6 ind/mł), despite overall higher Chlorophyll a levels in the seagrass station. At the seagrass station, the dominant copepods Paracalanus and Parvocalanus abundances were significantly higher (p<0.01, Mann-Whitney) during the SW monsoon, while Euterpina was significantly lower (p<0.04, Mann-Whitney). The non-seagrass station also showed a similar trend where the dominant copepods Paracalanus and Parvocalanus abundances were significantly higher in the SW monsoon (p<0.02, Mann-Whitney). Higher percentage of meroplankton was recorded during the study period in seagrass area with 11.6 %, 1.5 fold of non-seagrass area.

  20. Temporal patterns in coral reef, seagrass and mangrove communities from Chengue bay CARICOMP site (Colombia): 1993-2008.

    PubMed

    Rodríguez-Ramírez, Alberto; Garzón-Ferreira, Jaime; Batista-Morales, Angélica; Gil, Diego L; Gómez-López, Diana Isabel; Gómez-Campo, Kelly; López-Londoño, Tomás; Navas-Camacho, Raúl; Reyes-Nivia, María Catalina; Vega-Sequeda, Johanna

    2010-10-01

    Few monitoring programs have simultaneously assessed the dynamics of linked marine ecosystems (coral reefs, seagrass beds and mangroves) to document their temporal and spatial variability. Based on CARICOMP protocol we evaluated permanent stations in coral reefs, seagrass beds and mangroves from 1993 to 2008 in Chengue Bay at the Tayrona Natural Park, Colombian Caribbean. Overall, the studied ecosystems showed a remarkable stability pattern over the monitoring period. While there were annual variations in coral reefs (coral cover) and mangroves (litterfall) caused by hurricane Lenny in 1999, particular trends in seagrass (leaf area index and leaf productivity) appear to reflect the natural variability in this ecosystem. We suggest that monitoring sites at the three marine ecosystems had in general a healthy development in the last 16 years. Our results are critical to locally improve the management strategies (Tayrona Natural Park) and to understand the long-term dynamics of closely associated marine ecosystems in the Caribbean.

  1. The movement ecology of seagrasses

    PubMed Central

    McMahon, Kathryn; van Dijk, Kor-jent; Ruiz-Montoya, Leonardo; Kendrick, Gary A.; Krauss, Siegfried L.; Waycott, Michelle; Verduin, Jennifer; Lowe, Ryan; Statton, John; Brown, Eloise; Duarte, Carlos

    2014-01-01

    A movement ecology framework is applied to enhance our understanding of the causes, mechanisms and consequences of movement in seagrasses: marine, clonal, flowering plants. Four life-history stages of seagrasses can move: pollen, sexual propagules, vegetative fragments and the spread of individuals through clonal growth. Movement occurs on the water surface, in the water column, on or in the sediment, via animal vectors and through spreading clones. A capacity for long-distance dispersal and demographic connectivity over multiple timeframes is the novel feature of the movement ecology of seagrasses with significant evolutionary and ecological consequences. The space–time movement footprint of different life-history stages varies. For example, the distance moved by reproductive propagules and vegetative expansion via clonal growth is similar, but the timescales range exponentially, from hours to months or centuries to millennia, respectively. Consequently, environmental factors and key traits that interact to influence movement also operate on vastly different spatial and temporal scales. Six key future research areas have been identified. PMID:25297859

  2. The movement ecology of seagrasses.

    PubMed

    McMahon, Kathryn; van Dijk, Kor-Jent; Ruiz-Montoya, Leonardo; Kendrick, Gary A; Krauss, Siegfried L; Waycott, Michelle; Verduin, Jennifer; Lowe, Ryan; Statton, John; Brown, Eloise; Duarte, Carlos

    2014-11-22

    A movement ecology framework is applied to enhance our understanding of the causes, mechanisms and consequences of movement in seagrasses: marine, clonal, flowering plants. Four life-history stages of seagrasses can move: pollen, sexual propagules, vegetative fragments and the spread of individuals through clonal growth. Movement occurs on the water surface, in the water column, on or in the sediment, via animal vectors and through spreading clones. A capacity for long-distance dispersal and demographic connectivity over multiple timeframes is the novel feature of the movement ecology of seagrasses with significant evolutionary and ecological consequences. The space-time movement footprint of different life-history stages varies. For example, the distance moved by reproductive propagules and vegetative expansion via clonal growth is similar, but the timescales range exponentially, from hours to months or centuries to millennia, respectively. Consequently, environmental factors and key traits that interact to influence movement also operate on vastly different spatial and temporal scales. Six key future research areas have been identified.

  3. LINKS BETWEEN MARSH, NONVEGETATED, AND SEAGRASS HABITATS IN A PRISTINE VIRGINIA SYSTEM

    EPA Science Inventory

    Abstract: We describe habitat linkages in a narrow, contiguous marsh-nonvegetated seagrass system as is found bordering many undeveloped shorelines. Nekton were quantitatively sampled in eight spatial/tidal subhabitats on a Spartina-nonvegetated- Ruppia gradient using 1.75 m2 dro...

  4. LINKS BETWEEN MARSH, NONVEGETATED, AND SEAGRASS HABITATS IN A PRISTINE VIRGINIA SYSTEM

    EPA Science Inventory

    Abstract: We describe habitat linkages in a narrow, contiguous marsh-nonvegetated seagrass system as is found bordering many undeveloped shorelines. Nekton were quantitatively sampled in eight spatial/tidal subhabitats on a Spartina-nonvegetated- Ruppia gradient using 1.75 m2 dro...

  5. Seagrasses and the Coastal Marine Environment

    ERIC Educational Resources Information Center

    Phillips, Ronald C.

    1978-01-01

    Coastal ecosystems are the most highly productive in the world. This article discusses seagrasses, major coastal producers, and provides information on their ecology, productivity, position in food chains, and role in sediment stabilization. Recent attempts to restore seagrasses in areas of massive kills are described. (MA)

  6. SEAGRASS AND CDOM IN THE FLORIDA KEYS

    EPA Science Inventory

    Seagrasses play a variety of important ecological roles in coastal ecosystems. Here we present evidence that seagrass detritus from the widespread species, Thalassia testudinum, is an important source of ocean color and UV-protective substances in a low latitude coastal shelf reg...

  7. Seagrasses and the Coastal Marine Environment

    ERIC Educational Resources Information Center

    Phillips, Ronald C.

    1978-01-01

    Coastal ecosystems are the most highly productive in the world. This article discusses seagrasses, major coastal producers, and provides information on their ecology, productivity, position in food chains, and role in sediment stabilization. Recent attempts to restore seagrasses in areas of massive kills are described. (MA)

  8. SEAGRASS AND CDOM IN THE FLORIDA KEYS

    EPA Science Inventory

    Seagrasses play a variety of important ecological roles in coastal ecosystems. Here we present evidence that seagrass detritus from the widespread species, Thalassia testudinum, is an important source of ocean color and UV-protective substances in a low latitude coastal shelf reg...

  9. Understanding uncertainty in seagrass injury recovery: an information-theoretic approach.

    PubMed

    Uhrin, Amy V; Kenworthy, W Judson; Fonseca, Mark S

    2011-06-01

    Vessel groundings cause severe, persistent gaps in seagrass beds. Varying degrees of natural recovery have been observed for grounding injuries, limiting recovery prediction capabilities, and therefore, management's ability to focus restoration efforts where natural recovery is unlikely. To improve our capacity for predicting seagrass injury recovery, we used an information-theoretic approach to evaluate the relative contribution of specific injury attributes to the natural recovery of 30 seagrass groundings in Florida Keys National Marine Sanctuary, Florida, USA. Injury recovery was defined by three response variables examined independently: (1) initiation of seagrass colonization, (2) areal contraction, and (3) sediment in-filling. We used a global model and all possible subsets for four predictor variables: (1) injury age, (2) original injury volume, (3) original injury perimeter-to-area ratio, and (4) wave energy. Successional processes were underway for many injuries with fast-growing, opportunistic seagrass species contributing most to colonization. The majority of groundings that exhibited natural seagrass colonization also exhibited areal contraction and sediment in-filling. Injuries demonstrating colonization, contraction, and in-filling were on average older and smaller, and they had larger initial perimeter-to-area ratios. Wave energy was highest for colonizing injuries. The information-theoretic approach was unable to select a single "best" model for any response variable. For colonization and contraction, injury age had the highest relative importance as a predictor variable; wave energy appeared to be associated with second-order effects, such as sediment in-filling, which in turn, facilitated seagrass colonization. For sediment in-filling, volume and perimeter-to-area ratio had similar relative importance as predictor variables with age playing a lesser role than seen for colonization and contraction. Our findings confirm that these injuries

  10. Variability of sedimentary organic carbon in patchy seagrass landscapes.

    PubMed

    Ricart, Aurora M; York, Paul H; Rasheed, Michael A; Pérez, Marta; Romero, Javier; Bryant, Catherine V; Macreadie, Peter I

    2015-11-15

    Seagrass ecosystems, considered among the most efficient carbon sinks worldwide, encompass a wide variety of spatial configurations in the coastal landscape. Here we evaluated the influence of the spatial configuration of seagrass meadows at small scales (metres) on carbon storage in seagrass sediments. We intensively sampled carbon stocks and other geochemical properties (δ(13)C, particle size, depositional fluxes) across seagrass-sand edges in a Zostera muelleri patchy seagrass landscape. Carbon stocks were significantly higher (ca. 20%) inside seagrass patches than at seagrass-sand edges and bare sediments. Deposition was similar among all positions and most of the carbon was from allochthonous sources. Patch level attributes (e.g. edge distance) represent important determinants of the spatial heterogeneity of carbon stocks within seagrass ecosystems. Our findings indicate that carbon stocks of seagrass areas have likely been overestimated by not considering the influence of meadow landscapes, and have important relevance for the design of seagrass carbon stock assessments.

  11. Nutrient uptake by marshes and seagrasses: Ecosystem functions and spatial variability in the provision of this ecosystem servoce

    EPA Science Inventory

    Nitrogen entering coastal wetlands undergoes several important transformations involving oxidation and reduction; some ends up in the atmosphere, while much of it remains in the sediments of healthy marshes and seagrass beds – the rest passes into receiving waters. Variability i...

  12. Nutrient uptake by marshes and seagrasses: Ecosystem functions and spatial variability in the provision of this ecosystem servoce

    EPA Science Inventory

    Nitrogen entering coastal wetlands undergoes several important transformations involving oxidation and reduction; some ends up in the atmosphere, while much of it remains in the sediments of healthy marshes and seagrass beds – the rest passes into receiving waters. Variability i...

  13. The influence of seagrass on shell layers and Florida Bay mudbanks

    USGS Publications Warehouse

    Prager, E.J.; Halley, R.B.

    1999-01-01

    Aerial photography indicates that sometime since the early 1970's, an emergent ridge of shell debris developed on a mudbank north of Calusa Key in Florida Bay. Coarse shell deposits on and within the Bay's shallow mudbanks are believed to be the product of transport during major storm events and subsequent winnowing. However, shell material from the ridge contains nuclear bomb 14C, supporting formation within the past 30 years and the last major hurricanes to influence Florida Bay were Donna and Betsy (1960 and 1965). Results from this study suggest that the Calusa ridge and other coarse shell deposits in Florida Bay can result from, 1) periodic seagrass mortality and wave-induced transport during frequent winter cold fronts and/or 2) mollusc blooms and subsequent burial. A survey of bottom types indicates that dense to intermediate beds of seagrass, mainly Thalassia testudinum (turtle grass), occur within the shallow basins of western Florida Bay and along the margins of Bay mudbanks. Wave measurements and modeling indicate that Thalassia along mudbank margins can reduce incoming wave-energy by over 80%. Seagrass beds also host particularly dense populations of molluscs from periodic 'blooms' and are believed to be the major source of coarse sediments in the Bay. Thus, if bank-edge seagrass dies, sediments, including shell debris, become exposed and subject to greatly increased wave energy. Modeling indicates that winds typical of winter cold fronts in South Florida can produce near-bottom velocities and shear stress at a grass-free bank edge which are sufficient to transport coarse carbonate grains. Shell layers found at depth in mudbank cores can also be explained by previous episodes of sediment accretion over mollusc-rich seagrass beds or grass bed mortality at the edge of a mudbank and shell transport during cold front passage. The latter implies that mortality of marginal seagrass beds has occurred throughout the history of Florida Bay and that the

  14. Particle size variations between bed load and bed material in natural gravel bed channels

    Treesearch

    Thomas E. Lisle

    1995-01-01

    Abstract - Particle sizes of bed load and bed material that represent materials transported and stored over a period of years are used to investigate selective transport in 13 previously sampled, natural gravel bed channels. The ratio (D*) of median particle size of bed material to the transport- and frequency-weighted mean of median bed load size decreases to unity...

  15. Overview on seagrasses and related research in China

    NASA Astrophysics Data System (ADS)

    Shi, Yajun; Fan, Hangqing; Cui, Xiaojian; Pan, Lianghao; Li, Sen; Song, Xiukai

    2010-03-01

    Seagrass research in China is still in its infancy. Even though there has been progress recently, there is still a great deal of research needed to gain a better understanding of seagrass. In this article we review and discuss the advances in seagrass research in China from two aspects: (1) seagrass species and their distribution; (2) seagrass research in China, including studies on their taxonomy, ecology, photosynthesis, applications in aquaculture, salt-tolerance mechanisms and other research topics. A total of 18 seagrass species belonging to 8 genera are distributed in nine provinces and regions in China (including Hong Kong and Taiwan), as well as the Xisha and Nansha Archipelagos. They can be divided into two groups: a North China Group and a South China Group. Based on the seagrass distribution, the Chinese mainland coast can be divided into three sections: North China Seagrass Coast, Middle China Seagrass Coast, and South China Seagrass Coast. Ecological studies include research on seagrass communities, nutrient cycling in seagrass ecosystems, genetic diversity, pollution ecology and research in the key regions of Shandong, Guangdong, Guangxi, and Hainan. Seagrass species and their locations, community structure, ecological evaluation, epiphytes, ecological functions and threats in the key regions are also summarized. Other studies have focused on remote sensing of seagrass, threatened seagrass species of China, and pollen morphology of Halophila ovalis.

  16. Modeling future scenarios of light attenuation and potential seagrass success in a eutrophic estuary

    USGS Publications Warehouse

    del Barrio, Pilar; Ganju, Neil K.; Aretxabaleta, Alfredo L.; Hayn, Melanie; García, Andrés; Howarth, Robert W.

    2014-01-01

    Estuarine eutrophication has led to numerous ecological changes, including loss of seagrass beds. One potential cause of these losses is a reduction in light availability due to increased attenuation by phytoplankton. Future sea level rise will also tend to reduce light penetration and modify seagrass habitat. In the present study, we integrate a spectral irradiance model into a biogeochemical model coupled to the Regional Ocean Model System (ROMS). It is linked to a bio-optical seagrass model to assess potential seagrass habitat in a eutrophic estuary under future nitrate loading and sea-level rise scenarios. The model was applied to West Falmouth Harbor, a shallow estuary located on Cape Cod (Massachusetts) where nitrate from groundwater has led to eutrophication and seagrass loss in landward portions of the estuary. Measurements of chlorophyll, turbidity, light attenuation, and seagrass coverage were used to assess the model accuracy. Mean chlorophyll based on uncalibrated in-situ fluorometry varied from 28 μg L−1 at the landward-most site to 6.5 μg L−1 at the seaward site, while light attenuation ranged from 0.86 to 0.45 m-1. The model reproduced the spatial variability in chlorophyll and light attenuation with RMS errors of 3.72 μg L−1 and 0.07 m-1 respectively. Scenarios of future nitrate reduction and sea-level rise suggest an improvement in light climate in the landward basin with a 75% reduction in nitrate loading. This coupled model may be useful to assess habitat availability changes due to eutrophication and sediment resuspension and fully considers spatial variability on the tidal timescale.

  17. Distribution and ecology of seagrass communities in the Western Indian Ocean

    NASA Astrophysics Data System (ADS)

    Aleem, A. A.

    1. Nine seagrasses were identified and their distributions on coral reef islands and the African coastline studied. 2. Transects were worked to show the vertical zonation of the seagrasses. The more important communities encountered in order from low water spring tide level to the infralittoral were a Halodule uninervis community, a halodule - Thalassi or Thalassia - Cymodocea serrulata community, a Thalassia - Syringodium community, a Thalassia hemprichii community, and finally a Cymodocea ciliata community. 3. Halodule was the main pioneer species. 4. Thalassia and Cymodocea ciliata formed beds which in thelatter seagrass grew at depths of up to 40m. 5. Cymodecea ciliata grew on exposed or semi-exposed shores and formed mats 30-40cm thick. 6. The main environmental factors influencing the zonation of these seagrasses are substrate type, water depth, exposure to waves and current, and tidal range. They grow where water temperatures ranges between 26-30°C, but in littoral pools they may have to withstand temperatures as high as 38°C for short periods. 7. The substrates in which these seagrasses grow range from fine sand and silt to coarse sand mixed with coral debris. Thalassia was the only species which tolerated anoxic sediments and its roots can ramify through black sediments smelling of hydrogen sulphide. Halodule and Syringodium tolerates some lowering of sediment oxygen content. 8. Average standing stock of the main communities expressed as g Fresh Weight per square metre were ss follows: Halodule uninervis, 2430; Halophila ovalis, 465; Thalassia-Halodule, 4250; Thalassia-Cymodecea serrulata, 2907; Thalassia hemprichii, 4125; Cymodocea ciliata, 6050. There was evidence that seagrass biomass increased from LWS down into the infralittoral. The same communities were also analysed for the standing crops of assocated algae and macrofauna.

  18. Seagrass meadows in a globally changing environment.

    PubMed

    Unsworth, Richard K F; van Keulen, Mike; Coles, Rob G

    2014-06-30

    Seagrass meadows are valuable ecosystem service providers that are now being lost globally at an unprecedented rate, with water quality and other localised stressors putting their future viability in doubt. It is therefore critical that we learn more about the interactions between seagrass meadows and future environmental change in the anthropocene. This needs to be with particular reference to the consequences of poor water quality on ecosystem resilience and the effects of change on trophic interactions within the food web. Understanding and predicting the response of seagrass meadows to future environmental change requires an understanding of the natural long-term drivers of change and how these are currently influenced by anthropogenic stress. Conservation management of coastal and marine ecosystems now and in the future requires increased knowledge of how seagrass meadows respond to environmental change, and how they can be managed to be resilient to these changes. Finding solutions to such issues also requires recognising people as part of the social-ecological system. This special issue aims to further enhance this knowledge by bringing together global expertise across this field. The special issues considers issues such as ecosystem service delivery of seagrass meadows, the drivers of long-term seagrass change and the socio-economic consequences of environmental change to seagrass.

  19. Seasonal variation in species composition and abundance of demersal fish and invertebrates in a Seagrass Natural Reserve on the eastern coast of the Shandong Peninsula, China

    NASA Astrophysics Data System (ADS)

    Xu, Qiang; Guo, Dong; Zhang, Peidong; Zhang, Xiumei; Li, Wentao; Wu, Zhongxin

    2016-03-01

    Seagrass habitats are structurally complex ecosystems, which support high productivity and biodiversity. In temperate systems the density of seagrass may change seasonally, and this may influence the associated fish and invertebrate community. Little is known about the role of seagrass beds as possible nursery areas for fish and invertebrates in China. To study the functioning of a seagrass habitat in northern China, demersal fish and invertebrates were collected monthly using traps, from February 2009 to January 2010. The density, leaf length and biomass of the dominant seagrass Zostera marina and water temperature were also measured. The study was conducted in a Seagrass Natural Reserve (SNR) on the eastern coast of the Shandong Peninsula, China. A total of 22 fish species and five invertebrate species were recorded over the year. The dominant fish species were Synechogobius ommaturus, Sebastes schlegelii, Pholis fangi, Pagrus major and Hexagrammos otakii and these species accounted for 87% of the total number of fish. The dominant invertebrate species were Charybdis japonica and Octopus variabilis and these accounted for 98% of the total abundance of invertebrates. There was high temporal variation in species composition and abundance. The peak number of fish species occurred in August-October 2009, while the number of individual fish and biomass was highest during November 2009. Invertebrate numbers and biomass was highest in March, April, July and September 2009. Temporal changes in species abundance of fishes and invertebrates corresponded with changes in the shoot density and leaf length of the seagrass, Zostera marina.

  20. Waste Treatment And Immobilization Plant U. S. Department Of Energy Office Of River Protection Submerged Bed Scrubber Condensate Disposition Project - Abstract # 13460

    SciTech Connect

    Yanochko, Ronald M; Corcoran, Connie

    2012-11-15

    The Hanford Waste Treatment and Immobilization Plant (WTP) will generate an off-gas treatment system secondary liquid waste stream [submerged bed scrubber (SBS) condensate], which is currently planned for recycle back to the WTP Low Activity Waste (LAW) melter. This SBS condensate waste stream is high in Tc-99, which is not efficiently captured in the vitrified glass matrix. A pre-conceptual engineering study was prepared in fiscal year 2012 to evaluate alternate flow paths for melter off-gas secondary liquid waste generated by the WTP LAW facility. This study evaluated alternatives for direct off-site disposal of this SBS without pre-treatment, which mitigates potential issues associated with recycling.

  1. Seagrass-epifauna relationships in a temperate South African estuary: Interplay between patch-size, within-patch location and algal fouling

    NASA Astrophysics Data System (ADS)

    Källén, J.; Muller, H.; Franken, M. L.; Crisp, A.; Stroh, C.; Pillay, D.; Lawrence, C.

    2012-11-01

    Understanding the primary and interactive effects of patch-size, within-patch location and degree of algal fouling on epifaunal assemblages is important for seagrass ecology and management, especially in fragmented habitats. In this paper we examine the influence of these factors on epifaunal assemblages in the Heuningnes Estuary, which is one of South Africa's oldest protected systems. Multivariate analyses indicated that all seagrass properties significantly affected epifaunal assemblages and that two gastropods viz. Assiminea globulus and Haminoea alfredensis contributed most to the dissimilarities between factors. Abundance of epifauna and A. globulus were significantly greater at the edges of seagrass beds, whereas species diversity was higher in the interior. Differences in assemblage structure between inner cores and outer edges of seagrass beds are most likely due to the physical properties of each of these zones as well as competitive interactions and habitat preferences of species that utilize each section. Epifaunal richness and A. globulus abundance were significantly greater in large beds compared to small ones and the degree of algal fouling on seagrass beds inversely affected epifaunal abundance, species richness and A. globulus abundance. Importantly, there was a strong interaction between within-patch location and patch-size, indicating that the effects of within-patch location can be altered by patch-size. When explored further, ordinations indicated that epifaunal assemblages in cores and edges became more dissimilar as bed size increased. Similarly, differences in epifaunal abundance, and diversity as well as abundance of A. globulus and H. alfredensis between cores and edges of seagrass beds became greater with increasing bed size. Our results indicate the importance of large beds in enhancing spatial heterogeneity, richness and diversity and the need for adequate protection to prevent their fragmentation in future. This is especially pertinent

  2. Cubesat-Derived Detection of Seagrasses Using Planet Imagery Following Unmixing-Based Denoising: is Small the Next Big?

    NASA Astrophysics Data System (ADS)

    Traganos, D.; Cerra, D.; Reinartz, P.

    2017-05-01

    Seagrasses are one of the most productive and widespread yet threatened coastal ecosystems on Earth. Despite their importance, they are declining due to various threats, which are mainly anthropogenic. Lack of data on their distribution hinders any effort to rectify this decline through effective detection, mapping and monitoring. Remote sensing can mitigate this data gap by allowing retrospective quantitative assessment of seagrass beds over large and remote areas. In this paper, we evaluate the quantitative application of Planet high resolution imagery for the detection of seagrasses in the Thermaikos Gulf, NW Aegean Sea, Greece. The low Signal-to-noise Ratio (SNR), which characterizes spectral bands at shorter wavelengths, prompts the application of the Unmixing-based denoising (UBD) as a pre-processing step for seagrass detection. A total of 15 spectral-temporal patterns is extracted from a Planet image time series to restore the corrupted blue and green band in the processed Planet image. Subsequently, we implement Lyzenga's empirical water column correction and Support Vector Machines (SVM) to evaluate quantitative benefits of denoising. Denoising aids detection of Posidonia oceanica seagrass species by increasing its producer and user accuracy by 31.7 % and 10.4 %, correspondingly, with a respective increase in its Kappa value from 0.3 to 0.48. In the near future, our objective is to improve accuracies in seagrass detection by applying more sophisticated, analytical water column correction algorithms to Planet imagery, developing time- and cost-effective monitoring of seagrass distribution that will enable in turn the effective management and conservation of these highly valuable and productive ecosystems.

  3. Automatic seagrass pattern identification on sonar images

    NASA Astrophysics Data System (ADS)

    Rahnemoonfar, Maryam; Rahman, Abdullah

    2016-05-01

    Natural and human-induced disturbances are resulting in degradation and loss of seagrass. Freshwater flooding, severe meteorological events and invasive species are among the major natural disturbances. Human-induced disturbances are mainly due to boat propeller scars in the shallow seagrass meadows and anchor scars in the deeper areas. Therefore, there is a vital need to map seagrass ecosystems in order to determine worldwide abundance and distribution. Currently there is no established method for mapping the pothole or scars in seagrass. One of the most precise sensors to map the seagrass disturbance is side scan sonar. Here we propose an automatic method which detects seagrass potholes in sonar images. Side scan sonar images are notorious for having speckle noise and uneven illumination across the image. Moreover, disturbance presents complex patterns where most segmentation techniques will fail. In this paper, by applying mathematical morphology technique and calculating the local standard deviation of the image, the images were enhanced and the pothole patterns were identified. The proposed method was applied on sonar images taken from Laguna Madre in Texas. Experimental results show the effectiveness of the proposed method.

  4. Improved seagrass mapping using linear spectral unmixing of aerial photographs

    NASA Astrophysics Data System (ADS)

    Uhrin, Amy V.; Townsend, Philip A.

    2016-03-01

    Mapping of seagrass is challenging, particularly in areas where seagrass cover ranges from extensive, continuous meadows to aggregations of patchy mounds often no more than a meter across. Manual delineation of seagrass habitat polygons through visual photointerpretation of high resolution aerial imagery remains the most widely adopted approach for mapping seagrass extent but polygons often include unvegetated gaps. Although mapped polygon data exist for many estuaries, these are likely insufficient to accurately characterize spatial pattern or estimate area actually occupied by seagrass. We evaluated whether a linear spectral unmixing (LSU) classifier applied to manually-delineated seagrass polygons clipped from digital aerial images could improve mapping of seagrass in North Carolina. Representative seagrass endmembers were chosen directly from images and used to unmix image-clipped polygons, resulting in fraction planes (maps) of the proportion of seagrass present in each image pixel. Thresholding was used to generate seagrass maps for each pixel proportion from 0 (no thresholding, all pixel proportions included) to 1 (only pixels having 100% seagrass) in 0.1 increments. The optimal pixel proportion for identifying seagrass was assessed using Euclidean distance calculated from Receiver Operating Characteristic (ROC) curves and overall thematic accuracy calculated from confusion matrices. We assessed overall classifier performance using Kappa statistics and Area Under the (ROC) Curve (AUC). We compared seagrass area calculated from each threshold map to the total area of the corresponding manually-delineated polygon. LSU effectively classified seagrass and performed better than a random classification as indicated by high values for both Kappa statistics (0.72-98) and AUC (0.80-0.99). The LSU classifier effectively distinguished between seagrass and bare substrate resulting in fine-scale seagrass maps with overall thematic accuracies that exceeded our expected

  5. Seagrass science is growing: A report on the 12th International Seagrass Biology Workshop.

    PubMed

    Hind-Ozan, Edward J; Jones, Benjamin L

    2017-08-11

    This conference report describes the programme of the 12th International Seagrass Biology Workshop, its highlights, areas of growth for the workshop, and potential future directions for the workshop series. The report is written with an eye toward where it fits within the field of seagrass research. Copyright © 2017. Published by Elsevier Ltd.

  6. Remotely Sensed Optical Water Quality for Water Quality Assessment and Seagrass Protection in Florida's Big Bend Region

    NASA Astrophysics Data System (ADS)

    Carlson, P. R.; Hu, C.; Cannizarro, J.; Yarbro, L. A.; English, D. C.; Magley, W.; Charbonneau, M.; Barnes, B.

    2012-12-01

    Florida's Big Bend coastal region contains the second largest contiguous seagrass bed in the continental US. Approximately 250,000 ha of seagrass have been mapped in the region, but the total area of offshore seagrass beds might be several times greater. The Suwannee River drains a largely agricultural watershed (26,000 km2) in Georgia and Florida, and its discharge (x= 280 m3/s) affects water clarity over most of the Big Bend seagrass beds. Seagrass density, species composition and areal extent were severely affected by discharge associated with tropical cyclones in 2004 and 2005, focusing attention on this important resource and the near- and far-field impacts of the Suwannee River discharge. The Lower Suwannee River also has been identified by the Florida Department of Environmental Protection as an impaired water body due to high nitrogen and algal biomass. This project attempts to improve water quality and to protect Big Bend seagrasses by making remotely sensed optical water quality data more accessible to managers and stakeholders involved in the process of regulating nutrient loads in the Suwannee River and to provide data to assess effectiveness of management actions. To accomplish these goals, we have developed and tested new algorithms for retrieval of Kd, chlorophyll, and CDOM from Modis imagery, created a time series of optical water quality (OWQ) for the Suwannee River Estuary (SRE), and related seagrass gains and losses to annual variations in optical water quality. During two years of bimonthly ground-truth cruises, chlorophyll concentrations, Aph, Ad, and Acdom in the SRE were 0.3-38.3 mgm-3, 0.013-1.056, 0.013-0.735, and 0.042-7.24, respectively. For most locations and most cruises, CDOM was the dominant determinant of Kd. In the Modis time series, Kd488 estimates (calculated using the Quasi-Analytic Algorithm of Lee et al. 2006) covaried with Suwannee River discharge between 2002 and 2011 with an overall r2 value of 0.64. This relationship is

  7. Use of a high-resolution profiling sonar and a towed video camera to map a Zostera marina bed, Solent, UK

    NASA Astrophysics Data System (ADS)

    Lefebvre, A.; Thompson, C. E. L.; Collins, K. J.; Amos, C. L.

    2009-04-01

    Seagrasses are flowering plants that develop into extensive underwater meadows and play a key role in the coastal ecosystem. In the last few years, several techniques have been developed to map and monitor seagrass beds in order to protect them. Here, we present the results of a survey using a profiling sonar, the Sediment Imager Sonar (SIS) and a towed video sledge to study a Zostera marina bed in the Solent, southern UK. The survey aimed to test the instruments for seagrass detection and to describe the area for the first time. On the acoustic data, the bed produced the strongest backscatter along a beam. A high backscatter above the bottom indicated the presence of seagrass. The results of an algorithm developed to detect seagrass from the sonar data were tested against video data. Four parameters were calculated from the SIS data: water depth, a Seagrass Index (average backscatter 10-15 cm above the bed), canopy height (height above the bed where the backscatter crosses a threshold limit) and patchiness (percentage of beams in a sweep where the backscatter 10-15 cm above the bed is greater than a threshold limit). From the video, Zostera density was estimated together with macroalgae abundance and bottom type. Patchiness calculated from the SIS data was strongly correlated to seagrass density evaluated from the video, indicating that this parameter could be used for seagrass detection. The survey area has been classified based upon seagrass density, macroalgae abundance and bottom type. Only a small area was occupied by a dense canopy whereas most of the survey area was characterised by patchy seagrass. Results indicated that Zostera marina developed only on sandy bottoms and was not found in regions of gravel. Furthermore, it was limited to a depth shallower than 1.5 m below the level of Lowest Astronomical Tide and present in small patches across the intertidal zone. The average canopy height was 15 cm and the highest density was 150 shoots m -2.

  8. Mapping seagrass and colonized hard bottom in Springs Coast, Florida using WorldView-2 satellite imagery

    NASA Astrophysics Data System (ADS)

    Baumstark, René; Duffey, Renee; Pu, Ruiliang

    2016-11-01

    The offshore extent of seagrass habitat along the West Florida (USA) coast represents an important corridor for inshore-offshore migration of economically important fish and shellfish. Surviving at the fringe of light requirements, offshore seagrass beds are sensitive to changes in water clarity. Beyond and intermingled with the offshore seagrass areas are large swaths of colonized hard bottom. These offshore habitats of the West Florida coast have lacked mapping efforts needed for status and trends monitoring. The objective of this study was to propose an object-based classification method for mapping offshore habitats and to compare results to traditional photo-interpreted maps. Benthic maps were created from WorldView-2 satellite imagery using an Object Based Image Analysis (OBIA) method and a visual photo-interpretation method. A logistic regression analysis identified depth and distance from shore as significant parameters for discriminating spectrally similar seagrass and colonized hard bottom features. Seagrass, colonized hard bottom and unconsolidated sediment (sand) were mapped with 78% overall accuracy using the OBIA method compared to 71% overall accuracy using the photo-interpretation method. This study suggests an alternative for mapping deeper, offshore habitats capable of producing higher thematic and spatial resolution maps compared to those created with the traditional photo-interpretation method.

  9. Assessing diversity and phytoremediation potential of seagrass in tropical region

    USDA-ARS?s Scientific Manuscript database

    Seagrass ecosystem is one of the most important resources in the coastal areas. Seagrasses support and provide habitats for many coastal organisms in tropical region. Seagrasses are specialized marine flowering plants that have adapted to the nearshore environment with heterogeneous landscape struct...

  10. SEAGRASS DISTRIBUTION IN THE PENSACOLA BAY SYSTEM, NORTHWEST FLORIDA

    EPA Science Inventory

    Seagrass coverage in the northern Gulf of Mexico has decreased 20 to 100% in many estuaries since the 1950s. As a result, determination of seagrass coverage and identification of the cause(s) of declines are priority research issues. Aerial surveys of seagrass coverage in the P...

  11. SEAGRASS DISTRIBUTION IN THE PENSACOLA BAY SYSTEM, NORTHWEST FLORIDA

    EPA Science Inventory

    Seagrass coverage in the northern Gulf of Mexico has decreased 20 to 100% in many estuaries since the 1950s. As a result, determination of seagrass coverage and identification of the cause(s) of declines are priority research issues. Aerial surveys of seagrass coverage in the P...

  12. Seagrass landscapes and their effects on associated fauna: A review

    NASA Astrophysics Data System (ADS)

    Boström, Christoffer; Jackson, Emma L.; Simenstad, Charles A.

    2006-07-01

    Seagrasses comprise some of the most heterogeneous landscape structures of shallow-water estuarine/marine ecosystems in the world. However, while knowledge at the molecular, organism, patch and community scale is pervasive, understanding of seagrass landscape ecology is more fragmentary and has not been synthesized. The growth and recruitment dynamics of seagrasses as well as man-made and/or natural disturbances create complex spatial configurations of seagrass over broad (metres to kilometres) spatial scales. Hence, it is important to identify mechanisms maintaining and/or threatening the diversity-promoting function of seagrass meadows and to understand their effects on benthic populations and communities. Although landscape ecology has recently become more integrated into seagrass research, our understanding of animal responses to variability in seagrass landscape structure is still fragmentary. By reviewing the literature to date, this paper evaluates studies on seagrass landscape ecology, testing the general null hypothesis that concepts developed in terrestrial settings can be generalized across landscapes, and (a) presenting definitions and terms used in seagrass landscape ecology, (b) reviewing geographical patterns of seagrass landscape studies to identify possible key regions and target species, (c) evaluating different methodological approaches, (d) describing the spatial and temporal scales used to describe organism responses to seagrass landscape structure, and (e) placing seagrass landscapes into an applied context.

  13. Faunal Communities Are Invariant to Fragmentation in Experimental Seagrass Landscapes

    PubMed Central

    Marion, Scott R.; Lombana, Alfonso V.; Orth, Robert J.

    2016-01-01

    Human-driven habitat fragmentation is cited as one of the most pressing threats facing many coastal ecosystems today. Many experiments have explored the consequences of fragmentation on fauna in one foundational habitat, seagrass beds, but have either surveyed along a gradient of existing patchiness, used artificial materials to mimic a natural bed, or sampled over short timescales. Here, we describe faunal responses to constructed fragmented landscapes varying from 4–400 m2 in two transplant garden experiments incorporating live eelgrass (Zostera marina L.). In experiments replicated within two subestuaries of the Chesapeake Bay, USA across multiple seasons and non-consecutive years, we comprehensively censused mesopredators and epifaunal communities using complementary quantitative methods. We found that community properties, including abundance, species richness, Simpson and functional diversity, and composition were generally unaffected by the number of patches and the size of the landscape, or the intensity of sampling. Additionally, an index of competition based on species co-occurrences revealed no trends with increasing patch size, contrary to theoretical predictions. We extend conclusions concerning the invariance of animal communities to habitat fragmentation from small-scale observational surveys and artificial experiments to experiments conducted with actual living plants and at more realistic scales. Our findings are likely a consequence of the rapid life histories and high mobility of the organisms common to eelgrass beds, and have implications for both conservation and restoration, suggesting that even small patches can rapidly promote abundant and diverse faunal communities. PMID:27244652

  14. Effectiveness and consistency of a suite of descriptors for assessing the ecological status of seagrass meadows (Posidonia oceanica L. Delile)

    NASA Astrophysics Data System (ADS)

    Rotini, Alice; Belmonte, Alessandro; Barrote, Isabel; Micheli, Carla; Peirano, Andrea; Santos, Rui O.; Silva, João; Migliore, Luciana

    2013-09-01

    The increasing rate of human-induced environmental changes on coastal marine ecosystems has created a demand for effective descriptors, in particular for those suitable for monitoring the status of seagrass meadows. Growing evidence has supported the useful application of biochemical and genetic descriptors such as secondary metabolite synthesis, photosynthetic activity and genetic diversity. In the present study, we have investigated the effectiveness of different descriptors (traditional, biochemical and genetic) in monitoring seagrass meadow conservation status. The Posidonia oceanica meadow of Monterosso al Mare (Ligurian sea, NW Mediterranean) was subjected to the measurement of bed density, leaf biometry, total phenols, soluble protein and photosynthetic pigment content as well as to RAPD marker analysis. This suite of descriptors provided evidence of their effectiveness and convenient application as markers of the conservation status of P. oceanica and/or other seagrasses. Biochemical/genetic descriptors and those obtained by traditional methods depicted a well conserved meadow with seasonal variability and, particularly in summer, indicated a healthier condition in a portion of the bed (station C), which was in agreement with the physical and sedimentological features of the station. Our results support the usefulness of introducing biochemical and genetic approaches to seagrass monitoring programs since they are effective indicators of plant physiological stress and environmental disturbance.

  15. Structural constituents of the seagrass Posidonia australis.

    PubMed

    Torbatinejad, Nour Mohammad; Annison, Geoffrey; Rutherfurd-Markwick, Kay; Sabine, John R

    2007-05-16

    Large amounts of seagrass, Posidonia australis, wash onto beaches in South Australia each year, causing substantial environmental problems. It was of interest to assess the potential for an economic use of this seagrass-such as for animal nutrition. Structural constituents of P. australis (green, freshly deposited, and both washed and unwashed samples from dried deposits on the beach) were examined and compared. Glucose, galactose, and mannose were the dominant sugars (>10 g kg-1 of dry matter) in the soluble fraction of nonstarch polysaccharides in all seagrass forms. The content of the insoluble constituents of the nonstarch polysaccharides was significantly higher than soluble nonstarch polysaccharide constituents (P < 0.01). Data showed that the major constituents of the Posidonia cell wall are cellulose and lignin (190-209 and 145-154 g kg-1, respectively). The crude protein content of Posidonia ranged from 54 to 61 g kg-1. Results showed no biologically significant compositional differences between the four different forms of seagrass tested. Dry, unwashed seagrass, which is readily available in large quantities and easily harvested, may have potential as a foodstuff for ruminant animals.

  16. Draft Genome Sequences of Pseudomonas moraviensis UCD-KL30, Vibrio ostreicida UCD-KL16, Colwellia sp. Strain UCD-KL20, Shewanella sp. Strain UCD-KL12, and Shewanella sp. Strain UCD-KL21, Isolated from Seagrass

    PubMed Central

    Lujan, Karley M.; Coil, David A.

    2017-01-01

    ABSTRACT Here, we present the draft genome sequences for five bacterial strains. These strains were all isolated from seagrass (Zostera marina) collected from Bodega Bay, CA, as a part of an undergraduate research project focused on seagrass-associated microbes. PMID:28360178

  17. Development of threshold values for a seagrass epiphyte ...

    EPA Pesticide Factsheets

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experiments, and have quantifiable impacts on light available to host plants. An extensive review of seagrass epiphyte literature was conducted to determine whether seagrass epiphyte metrics can be used as a biological indicator for nutrient impacts. While a wide variety of epiphyte metrics have been used by authors, epiphyte biomass as biomass per unit seagrass biomass may be the most effective epiphyte indicator. Regression analyses of epiphyte versus seagrass response metrics were used to estimate values representing potential thresholds for environmental concern. Median epiphyte loads associated with 25 and 50% reduction in seagrass biomass, density and productivity are proposed as potential thresholds. Location-specific modifying factors (grazing pressure, seagrass species) that cause variation in response patterns are the greatest challenge to regional scale applicability of threshold values. An extensive review of seagrass epiphyte literature was conducted to determine whether, and under what conditions, seagrass epiphyte metrics could be used as a potential indicator for nutrient impacts in estuarine ecosystems. Location-specific modifying factors (grazing pressure, seagrass speci

  18. Development of threshold values for a seagrass epiphyte ...

    EPA Pesticide Factsheets

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experiments, and have quantifiable impacts on light available to host plants. An extensive review of seagrass epiphyte literature was conducted to determine whether seagrass epiphyte metrics can be used as a biological indicator for nutrient impacts. While a wide variety of epiphyte metrics have been used by authors, epiphyte biomass as biomass per unit seagrass biomass may be the most effective epiphyte indicator. Regression analyses of epiphyte versus seagrass response metrics were used to estimate values representing potential thresholds for environmental concern. Median epiphyte loads associated with 25 and 50% reduction in seagrass biomass, density and productivity are proposed as potential thresholds. Location-specific modifying factors (grazing pressure, seagrass species) that cause variation in response patterns are the greatest challenge to regional scale applicability of threshold values. An extensive review of seagrass epiphyte literature was conducted to determine whether, and under what conditions, seagrass epiphyte metrics could be used as a potential indicator for nutrient impacts in estuarine ecosystems. Location-specific modifying factors (grazing pressure, seagrass speci

  19. [Seagrass ecosystems: contributions to and mechanisms of carbon sequestration].

    PubMed

    Qiu, Guang-Long; Lin, Hsing-Juh; Li, Zong-Shan; Fan, Hang-Qing; Zhou, Hao-Lang; Liu, Guo-Hua

    2014-06-01

    The ocean's vegetated habitats, in particular seagrasses, mangroves and salt marshes, each capture and store a comparable amount of carbon per year, forming the Earth's blue carbon sinks, the most intense carbon sinks on the planet. Seagrass meadows, characterized by high primary productivity, efficient water column filtration and sediment stability, have a pronounced capacity for carbon sequestration. This is enhanced by low decomposition rates in anaerobic seagrass sediments. The carbon captured by seagrass meadows contributes significantly to the total blue carbon. At a global scale, seagrass ecosystems are carbon sink hot spots and have profound influences on the global carbon cycle. This importance combined with the many other functions of seagrass meadows places them among the most valuable ecosystems in the world. Unfortunately, seagrasses are declining globally at an alarming rate owing to anthropogenic disturbances and climate change, making them also among the most threatened ecosystems on the Earth. The role of coastal systems in carbon sequestration has received far too little attention and thus there are still many uncertainties in evaluating carbon sequestration of global seagrass meadows accurately. To better assess the carbon sequestration of global seagrass ecosystems, a number of scientific issues should be considered with high priorities: 1) more accurate measurements of seagrass coverage at national and global levels; 2) more comprehensive research into species- and location-specific carbon sequestration efficiencies; 3) in-depth exploration of the effects of human disturbance and global climate change on carbon capture and storage by seagrass ecosystems.

  20. The emergence of molecular profiling and omics techniques in seagrass biology; furthering our understanding of seagrasses.

    PubMed

    Davey, Peter A; Pernice, Mathieu; Sablok, Gaurav; Larkum, Anthony; Lee, Huey Tyng; Golicz, Agnieszka; Edwards, David; Dolferus, Rudy; Ralph, Peter

    2016-09-01

    Seagrass meadows are disappearing at alarming rates as a result of increasing coastal development and climate change. The emergence of omics and molecular profiling techniques in seagrass research is timely, providing a new opportunity to address such global issues. Whilst these applications have transformed terrestrial plant research, they have only emerged in seagrass research within the past decade; In this time frame we have observed a significant increase in the number of publications in this nascent field, and as of this year the first genome of a seagrass species has been sequenced. In this review, we focus on the development of omics and molecular profiling and the utilization of molecular markers in the field of seagrass biology. We highlight the advances, merits and pitfalls associated with such technology, and importantly we identify and address the knowledge gaps, which to this day prevent us from understanding seagrasses in a holistic manner. By utilizing the powers of omics and molecular profiling technologies in integrated strategies, we will gain a better understanding of how these unique plants function at the molecular level and how they respond to on-going disturbance and climate change events.

  1. Biomechanical factors contributing to self-organization in seagrass landscapes

    USGS Publications Warehouse

    Fonseca, M.S.; Koehl, M.A.R.; Kopp, B.S.

    2007-01-01

    Field observations have revealed that when water flow is consistently from one direction, seagrass shoots align in rows perpendicular to the primary axis of flow direction. In this study, live Zostera marina shoots were arranged either randomly or in rows perpendicular to the flow direction and tested in a seawater flume under unidirectional flow and waves to determine if shoot arrangement: a) influenced flow-induced force on individual shoots, b) differentially altered water flow through the canopy, and c) influenced light interception by the canopy. In addition, blade breaking strength was compared with flow-induced force to determine if changes in shoot arrangement might reduce the potential for damage to shoots. Under unidirectional flow, both current velocity in the canopy and force on shoots were significantly decreased when shoots were arranged in rows as compared to randomly. However, force on shoots was nearly constant with downstream distance, arising from the trade-off of shoot bending and in-canopy flow reduction. The coefficient of drag was higher for randomly-arranged shoots at low velocities (< 30 cm s- 1) but converged rapidly among the two shoot arrangements at higher velocities. Shoots arranged in rows tended to intercept slightly more light than those arranged randomly. Effects of shoot arrangement under waves were less clear, potentially because we did not achieve the proper plant size?row spacing ratio. At this point, we may only suggest that water motion, as opposed to light capture, is the dominant physical mechanism responsible for these shoot arrangements. Following a computation of the Environmental Stress Factor, we concluded that even photosynthetically active blades may be damaged or broken under frequently encountered storm conditions, irrespective of shoot arrangement. We hypothesize that when flow is generally from one direction, seagrass bed patterns over multiple scales of consideration may arise as a cumulative effect of

  2. ACETOGENIC BACTERIA ASSOCIATED WITH SEAGRASS ROOTS

    EPA Science Inventory

    Seagrasses are adapted to being rooted in reduced, anoxic sediments with high rates of sulfate reduction. During the day, an oxygen gradient is generated around the roots, becoming anoxic at night. Thus, obligate anaerobic bacteria in the rhizosphere have to tolerate elevated oxy...

  3. ACETOGENIC BACTERIA ASSOCIATED WITH SEAGRASS ROOTS

    EPA Science Inventory

    Seagrasses are adapted to being rooted in reduced, anoxic sediments with high rates of sulfate reduction. During the day, an oxygen gradient is generated around the roots, becoming anoxic at night. Thus, obligate anaerobic bacteria in the rhizosphere have to tolerate elevated oxy...

  4. Manatees mapping seagrass (USA & Puerto Rico)

    USGS Publications Warehouse

    Slone, Daniel H.; Reid, James P.; Kenworthy, W. Judson; Di Carlo, Giuseppe; Butler, Susan M.

    2012-01-01

    West Indian manatees (Trichechus manatus) are secretive creatures. While some of their behaviours at winter aggregation sites in Florida are readily visible to the casual observer, many of their habits and movements are difficult to observe. They rely on submerged vegetation for nutrition, and seagrasses are one of their most important food sources.

  5. Mapping Mediterranean seagrasses with Sentinel-2 imagery.

    PubMed

    Traganos, Dimosthenis; Reinartz, Peter

    2017-07-01

    Mediterranean seagrasses have been hailed for their numerous ecosystem services, yet they are undergoing a decline in their coverage. The major complication with resolving this tendency is the sparsity of data on their overall distribution. This study addresses the suitability of the recently launched Sentinel-2 satellite for mapping the distribution of Mediterranean seagrass meadows. A comprehensive methodology is presented which applies atmospheric and analytical water column corrections and compares the performance of three different supervised classifiers. Remote sensing of the Thermaikos Gulf, northwestern Aegean Sea (Greece, eastern Mediterranean Sea) reveals that the utilization of Support Vector Machines on water column corrected reflectances yields best accuracies. Two Mediterranean seagrasses, Posidonia oceanica and Cymodocea nodosa, cover a total submerged area of 1.48km(2) between depths of 1.4-16.5m. With its 10-m spatial resolution and 5-day revisit frequency, Sentinel-2 imagery can mitigate the Mediterranean seagrass distribution data gap and allow better management and conservation in the future in a retrospective, time- and cost-effective fashion. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. MEASURING INVERTEBRATE GRAZING ON SEAGRASSES AND EPIPHYTES

    EPA Science Inventory

    The chapter describes methods to assess grazing rates, grazer preferences, and grazer impacts, by mobile organisms living in the canopy or in the rhizome layer in any seagrass system. One set of methods quantifies grazing activity in small to medium sized, mobile organisms livin...

  7. MEASURING INVERTEBRATE GRAZING ON SEAGRASSES AND EPIPHYTES

    EPA Science Inventory

    The chapter describes methods to assess grazing rates, grazer preferences, and grazer impacts, by mobile organisms living in the canopy or in the rhizome layer in any seagrass system. One set of methods quantifies grazing activity in small to medium sized, mobile organisms livin...

  8. Fine bed material in pools of natural gravel bed channels

    Treesearch

    Thomas E. Lisle; Sue Hilton

    1999-01-01

    Abstract - Natural gravel bed channels commonly contain a fine mode of sand and fine gravel that fills voids of the bed framework of coarser gravel. If the supply of fine bed material exceeds the storage capacity of framework voids, excess fine material forms surficial patches, which can be voluminous in pools during low flow. Data collected in 34 natural channels in...

  9. Managing nitrogen inputs into seagrass meadows near a coastal city: flow-on from research to environmental improvement plans.

    PubMed

    Nayar, S; Collings, G; Pfennig, P; Royal, M

    2012-05-01

    Increased human habitation has led to a 30 to 50-fold increase in nutrient loads to the coastal waters of Adelaide, resulting in the loss of over 5000 ha of seagrass meadows. The rate of loss since the 1940s has been irregular, averaging 85 ha yr(-1), marked by a substantial peak between 1971 and 1977. A modelling approach allowed comparison of the annual input with the annual uptake rates for the different biotic components in the seagrass bed. In 2005, the estimated uptake of ammonium (465 t yr(-1)) and nitrate (3.04 t yr(-1)) by the seagrass and associated epiphytes in the Adelaide region accounted for 31% of the ammonium and <1% of the nitrate that is currently discharged into the coastal waters. Environment Improvement Programs, such as the one implemented in 1996, may reduce the total nitrogen loads to 700 t yr(-1), possibly stemming further losses and facilitating recolonisation of new seagrass. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Modeling the Hydrodynamic Effects of Seagrass Meadows in a Shallow, Back-barrier Estuary

    NASA Astrophysics Data System (ADS)

    Ganju, N. K.; Beudin, A.; Aretxabaleta, A.

    2016-02-01

    Seagrasses are often referred to as eco-engineers because they stabilize sediment beds and create favorable habitat for other organisms. Simulating the influence of seagrasses on estuarine habitat requires integration of their physical characteristics into hydrodynamic and sediment transport models. A flexible vegetation module has been implemented in the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system and tested first in idealized conditions. Under typical shallow water hydrodynamic conditions, the three-dimensional vegetation drag significantly dampens the current velocity (by about 80 % locally) and balances an enhanced pressure gradient. In addition, vegetation increases water column mixing (up to a factor of 2 at mid-depth) mostly due to the strong shear at the top of the submerged canopy. Flow accelerates on the sides of the patch and vortex circulation forms in the wake of the patch. Vegetation has a direct effect on wave damping and an indirect effect on wave propagation through its effects on surface current. We then applied the modeling system to Chincoteague Bay, MD/VA, to assess the physical role of seagrass meadows in a typical mid-Atlantic shallow back-barrier lagoon under a shifting influence of wave, wind, tidal and freshwater forcing. Different scenarios of vegetation distribution based on detailed historical maps provide a series of testable hypotheses to evaluate the buffering capabilities of submerged vegetation against storms and the sediment transport regime. Preliminary simulations accounting for the presence of seagrass show that storm surge is reduced by approximately 5 % and wind waves by around 40 % at the coast. Meanwhile, fine sediment deposition after storms is enhanced on the eastern part of the bay initially covered by sand over-wash from the barrier island. These results can be used to inform ecosystem-based management of coastal change hazards.

  11. Seagrass biomass and productivity in the Florida Keys, USA: ground-level and airborne measurements

    NASA Astrophysics Data System (ADS)

    Yarbro, L.; Carlson, P. R., Jr.; McHan, C.; Carlson, D. F.; Hu, C.; Danielson, T.; Durnan, B.; English, D. C.; Muller-Karger, F. E.; Yates, K. K.; Herwitz, S.; Merrill, J.; Mewes, T.

    2013-12-01

    Seagrass communities serve as essential habitat for fish and shellfish, and recent research indicates that they can play a significant role in reducing ocean acidification. As part of a collaborative project funded by the NASA ROSES program and administered by the NASA UAV Collaborative, we collected hyperspectral imagery of seagrass beds and measured productivity of Thalassia testudinum at Sugarloaf Key, Florida, in May 2012, October 2012, and May 2013. Our primary goal was to evaluate the utility of hyperspectral sensors, in general, and UAV platforms, in specific, to measure seagrass health and productivity. Airborne measurements using the AISA Eagle hyperspectral imaging system were carried out simultaneously with ground measurements of Thalassia fluorescence, oxygen metabolism, growth, and biomass, as well as remote sensing reflectance and several in situ optical properties. Water depths at the study site ranged from less than 1 m to 5 m. Phytoplankton chlorophyll-a concentrations (0.09-0.72 ug l-1), ag(440) (0-0.02 m-1), and turbidity (0.12-4.1 ntu) were relatively low for all three deployments, facilitating the collection of excellent imagery and application of water-column radiative-transfer corrections. Aboveground Thalassia and macroalgal biomass, at 18 sites in the study area, ranged from 210 to 690 and 11 to 590 gDW m-2, respectively. One-sided green leaf area index of Thalassia ranged from 0.7 to 3.0. Preliminary findings show that the sensitivity of relationships between seagrass productivity and biomass parameters and remotely-sensed habitat spectra is reduced with increasing water depth and, even in shallow water, is complicated by epiphytic algae and sediment coverage of leaf surfaces.

  12. Dugong grazing and turtle cropping: grazing optimization in tropical seagrass systems?

    PubMed

    Aragones, Lemnuel V; Lawler, Ivan R; Foley, William J; Marsh, Helene

    2006-10-01

    Grazing by dugongs and cropping by green turtles have the capacity to alter the subsequent nutritional quality of seagrass regrowth. We examined the effects of simulated light and intensive grazing by dugongs and cropping by turtles on eight nutritionally relevant measures of seagrass chemical composition over two regrowth periods (short-term, 1-4 months; long-term, 11-13 months) at two seagrass communities (a mixed species community with Zostera capricorni, Halophila ovalis, Halodule uninervis, Cymodocea rotundata and C. serrulate; and a monospecific bed of Halodule uninervis) in tropical Queensland, Australia. The concentrations of organic matter, total nitrogen, total water-soluble carbohydrates, total starch, neutral detergent fiber, acid detergent fiber, acid lignin, as well as the in vitro dry matter digestibility (IVDMD) were measured in the leaves and below-ground parts of each species using near-infrared reflectance spectroscopy (NIRS). Regrowth of preferred species such as H. ovalis and H. uninervis from simulated intensive dugong grazing after a year exhibited increased (by 35 and 25%, respectively, relative to controls) whole-plant N concentrations. Similarly, regrowth of H. ovalis from simulated turtle cropping showed an increase in the leaf N concentration of 30% after a year. However, these gains are tempered by reductions in starch concentrations and increases in fiber. In the short-term, the N concentrations increased while the fiber concentrations decreased. These data provide experimental support for a grazing optimization view of herbivory in the tropical seagrass system, but with feedback in a different manner. Furthermore, we suggest that in areas where grazing is the only major source of natural disturbance, it is likely that there are potential ecosystem level effects if and when numbers of dugongs and turtles are reduced.

  13. Characterization of available light for seagrass and patch reef productivity in Sugarloaf Key, Lower Florida Keys

    USGS Publications Warehouse

    Toro-Farmer, Gerardo; Muller-Karger, Frank E.; Vega-Rodriguez, Maria; Melo, Nelson; Yates, Kimberly K.; Johns, Elizabeth; Cerdeira-Estrada, Sergio; Herwitz, Stan R.

    2016-01-01

    Light availability is an important factor driving primary productivity in benthic ecosystems, but in situ and remote sensing measurements of light quality are limited for coral reefs and seagrass beds. We evaluated the productivity responses of a patch reef and a seagrass site in the Lower Florida Keys to ambient light availability and spectral quality. In situ optical properties were characterized utilizing moored and water column bio-optical and hydrographic measurements. Net ecosystem productivity (NEP) was also estimated for these study sites using benthic productivity chambers. Our results show higher spectral light attenuation and absorption, and lower irradiance during low tide in the patch reef, tracking the influx of materials from shallower coastal areas. In contrast, the intrusion of clearer surface Atlantic Ocean water caused lower values of spectral attenuation and absorption, and higher irradiance in the patch reef during high tide. Storms during the studied period, with winds >10 m·s−1, caused higher spectral attenuation values. A spatial gradient of NEP was observed, from high productivity in the shallow seagrass area, to lower productivity in deeper patch reefs. The highest daytime NEP was observed in the seagrass, with values of almost 0.4 g·O2·m−2·h−1. Productivity at the patch reef area was lower in May than during October 2012 (mean = 0.137 and 0.177 g·O2·m−2·h−1, respectively). Higher photosynthetic active radiation (PAR) levels measured above water and lower light attenuation in the red region of the visible spectrum (~666 to ~699 nm) had a positive correlation with NEP. Our results indicate that changes in light availability and quality by suspended or resuspended particles limit benthic productivity in the Florida Keys.

  14. Accelerating Tropicalization and the Transformation of Temperate Seagrass Meadows.

    PubMed

    Hyndes, Glenn A; Heck, Kenneth L; Vergés, Adriana; Harvey, Euan S; Kendrick, Gary A; Lavery, Paul S; McMahon, Kathryn; Orth, Robert J; Pearce, Alan; Vanderklift, Mathew; Wernberg, Thomas; Whiting, Scott; Wilson, Shaun

    2016-11-01

    Climate-driven changes are altering production and functioning of biotic assemblages in terrestrial and aquatic environments. In temperate coastal waters, rising sea temperatures, warm water anomalies and poleward shifts in the distribution of tropical herbivores have had a detrimental effect on algal forests. We develop generalized scenarios of this form of tropicalization and its potential effects on the structure and functioning of globally significant and threatened seagrass ecosystems, through poleward shifts in tropical seagrasses and herbivores. Initially, we expect tropical herbivorous fishes to establish in temperate seagrass meadows, followed later by megafauna. Tropical seagrasses are likely to establish later, delayed by more limited dispersal abilities. Ultimately, food webs are likely to shift from primarily seagrass-detritus to more direct-consumption-based systems, thereby affecting a range of important ecosystem services that seagrasses provide, including their nursery habitat role for fishery species, carbon sequestration, and the provision of organic matter to other ecosystems in temperate regions.

  15. A framework for the resilience of seagrass ecosystems.

    PubMed

    Unsworth, Richard K F; Collier, Catherine J; Waycott, Michelle; Mckenzie, Len J; Cullen-Unsworth, Leanne C

    2015-11-15

    Seagrass ecosystems represent a global marine resource that is declining across its range. To halt degradation and promote recovery over large scales, management requires a radical change in emphasis and application that seeks to enhance seagrass ecosystem resilience. In this review we examine how the resilience of seagrass ecosystems is becoming compromised by a range of local to global stressors, resulting in ecological regime shifts that undermine the long-term viability of these productive ecosystems. To examine regime shifts and the management actions that can influence this phenomenon we present a conceptual model of resilience in seagrass ecosystems. The model is founded on a series of features and modifiers that act as interacting influences upon seagrass ecosystem resilience. Improved understanding and appreciation of the factors and modifiers that govern resilience in seagrass ecosystems can be utilised to support much needed evidence based management of a vital natural resource.

  16. Comparison of Fish Assemblages Associated with Seagrass and Adjacent Unvegetated Habitats of Port Phillip Bay and Corner Inlet, Victoria, Australia, with Emphasis on Commercial Species

    NASA Astrophysics Data System (ADS)

    Jenkins, G. P.; May, H. M. A.; Wheatley, M. J.; Holloway, M. G.

    1997-05-01

    Species richness, abundance and biomass of fishes from seagrass and unvegetated habitats were analysed for sites in the Swan Bay region of Port Phillip Bay, and Corner Inlet, Victoria, Australia. Fish assemblages from intertidal Zostera muellerisites showed greater similarity with a number of shallower unvegetated sites than to subtidal Heterozostera tasmanica. Similarly, subtidal, unvegetated sites in Swan Bay were more similar to subtidal Heterozosterasites than to other, generally shallower, unvegetated sites. Species richness was significantly higher in seagrass beds and showed an increase over the warmer months of the year. Differences in abundance and biomass of fishes between vegetated and unvegetated habitats depended on the location of sampling. In general, abundance and biomass of fish in the deeper subtidal seagrass were significantly higher than in unvegetated habitats of the same depth. In contrast, abundance and biomass were not significantly different between seagrass and unvegetated habitats of the intertidal and shallow subtidal zones when significant abundances of the long-finned goby, Favonigobius lateralis, occurred on unvegetated habitats. As a consequence, species richness would be expected to decrease with any seagrass loss; however, decreases in abundance and biomass of fishes would be greatest with loss of deeper subtidal Heterozosterahabitats. Although juveniles of a number of commercially important species were associated with subtidal Heterozosterahabitats, juveniles of other species of commercial significance were found on shallow, unvegetated habitats. Newly settled juveniles of the King George whiting, Sillaginodes punctata, were associated with unvegetated patches amongst subtidal seagrass in Swan Bay, in contrast with a direct association with seagrass reported from other areas.

  17. Seagrasses in northern Gulf of Mexico: An ecosystem in trouble

    USGS Publications Warehouse

    ,

    2000-01-01

    The USGS National Wetlands Research Center has documented that Seagrasses in the northern Gulf of Mexico constitute an ecosystem in trouble. From studies in St. Andrews Bay, Period Bay, the Chandeleur Islands, and the Gulf Islands National Seashore, scientists have discovered that declining seagrass acreage ranges from 12% to 66% in bays and estuaries of the Gulf of Mexico. Not only are seagrasses disappearing, but they are also changing in species composition, densities, and patchiness.

  18. Rapidly spreading seagrass invades the Caribbean with unknown ecological consequences

    USGS Publications Warehouse

    Rogers, Caroline S.; Willette, Demian A; Miller, Jeff

    2014-01-01

    The non-native seagrass Halophila stipulacea has spread rapidly throughout the Caribbean Sea (Willette et al. 2014); without additional research, the ecological ramifications of this invasion are difficult to predict. Biodiversity, connectivity of marine ecosystems, and recovery of degraded coral reefs could all be affected. The invasive seagrass, native to the Red Sea and Indian Ocean, has taken over sand bottoms and intermixed with or replaced native seagrasses, including Thalassia testudinum, Syringodium filiforme, and Halodule wrightii.

  19. Effects of nutrient load on microbial activities within a seagrass-dominated ecosystem: Implications of changes in seagrass blue carbon.

    PubMed

    Liu, Songlin; Jiang, Zhijian; Wu, Yunchao; Zhang, Jingping; Arbi, Iman; Ye, Feng; Huang, Xiaoping; Macreadie, Peter Ian

    2017-04-15

    Nutrient loading is a leading cause of global seagrass decline, triggering shifts from seagrass- to macroalgal-dominance. Within seagrass meadows of Xincun Bay (South China Sea), we found that nutrient loading (due to fish farming) increased sediment microbial biomass and extracellular enzyme activity associated with carbon cycling (polyphenol oxidase, invertase and cellulase), with a corresponding decrease in percent sediment organic carbon (SOC), suggesting that nutrients primed microorganism and stimulated SOC remineralization. Surpisingly, however, the relative contribution of seagrass-derived carbon to bacteria (δ(13)Cbacteria) increased with nutrient loading, despite popular theory being that microbes switch to consuming macroalgae which are assumed to provide a more labile carbon source. Organic carbon sources of fungi were unaffected by nutrient loading. Overall, this study suggests that nutrient loading changes the relative contribution of seagrass and algal sources to SOC pools, boosting sediment microbial biomass and extracellular enzyme activity, thereby possibly changing seagrass blue carbon. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Effects of common seagrass restoration methods on ecosystem structure in subtropical seagrass meadows.

    PubMed

    Bourque, Amanda S; Fourqurean, James W

    2014-06-01

    Seagrass meadows near population centers are subject to frequent disturbance from vessel groundings. Common seagrass restoration methods include filling excavations and applying fertilizer to encourage seagrass recruitment. We sampled macrophytes, soil structure, and macroinvertebrate infauna at unrestored and recently restored vessel grounding disturbances to evaluate the effects of these restoration methods on seagrass ecosystem structure. After a year of observations comparing filled sites to both undisturbed reference and unrestored disturbed sites, filled sites had low organic matter content, nutrient pools, and primary producer abundance. Adding a nutrient source increased porewater nutrient pools at disturbed sites and in undisturbed meadows, but not at filled sites. Environmental predictors of infaunal community structure across treatments included soil texture and nutrient pools. At the one year time scale, the restoration methods studied did not result in convergence between restored and unrestored sites. Particularly in filled sites, soil conditions may combine to constrain rapid development of the seagrass community and associated infauna. Our study is important for understanding early recovery trajectories following restoration using these methods.

  1. Seagrass restoration enhances "blue carbon" sequestration in coastal waters.

    PubMed

    Greiner, Jill T; McGlathery, Karen J; Gunnell, John; McKee, Brent A

    2013-01-01

    Seagrass meadows are highly productive habitats that provide important ecosystem services in the coastal zone, including carbon and nutrient sequestration. Organic carbon in seagrass sediment, known as "blue carbon," accumulates from both in situ production and sedimentation of particulate carbon from the water column. Using a large-scale restoration (>1700 ha) in the Virginia coastal bays as a model system, we evaluated the role of seagrass, Zosteramarina, restoration in carbon storage in sediments of shallow coastal ecosystems. Sediments of replicate seagrass meadows representing different age treatments (as time since seeding: 0, 4, and 10 years), were analyzed for % carbon, % nitrogen, bulk density, organic matter content, and ²¹⁰Pb for dating at 1-cm increments to a depth of 10 cm. Sediment nutrient and organic content, and carbon accumulation rates were higher in 10-year seagrass meadows relative to 4-year and bare sediment. These differences were consistent with higher shoot density in the older meadow. Carbon accumulation rates determined for the 10-year restored seagrass meadows were 36.68 g C m⁻² yr⁻¹. Within 12 years of seeding, the restored seagrass meadows are expected to accumulate carbon at a rate that is comparable to measured ranges in natural seagrass meadows. This the first study to provide evidence of the potential of seagrass habitat restoration to enhance carbon sequestration in the coastal zone.

  2. [Benthic fauna associated to a Thalassia testudinum (Hydrocharitaceae) bed in Parque Nacional Morrocoy, Venezuela].

    PubMed

    Rodríguez, C; Villamizar, E

    2000-12-01

    The benthic fauna and diel variation in a shallow seagrass bed (Thalassia testudinum) were studied in Playa Mero, Venezuela. Samples of organisms and sediments were taken using PVC cylinders, 5cm in diameter, along a transect perpendicular to the coast. Seagrass cover, shoot density and biomass were estimated. The seagrass cover was homogeneous along the transect. The intermediate zone had the highest number of shoots and of above-ground and rhizome biomass. Composition and abundance of benthic organisms were related with seagrass and sediment characteristics. Sediment organic matter content and organism abundance were highest near the shore Molluscs, polychaetes, oligochaetes and nematodes were the most abundant groups. Species richness was higher in daytime (40 versus 28 at night). Gastropods were the most abundant organisms both at day and night while polychaetes and crustaceans increased during the day, and holoturids were more numerous at night.

  3. Tropical seaweed beds are important habitats for mobile invertebrate epifauna

    NASA Astrophysics Data System (ADS)

    Tano, Stina; Eggertsen, M.; Wikström, S. A.; Berkström, C.; Buriyo, A. S.; Halling, C.

    2016-12-01

    Marine macrophyte habitats in temperate regions provide productive habitats for numerous organisms, with their abundant and diverse invertebrate epifaunal assemblages constituting important linkages between benthic primary production and higher trophic levels. While it is commonly also recognized that certain vegetated habitats in the tropics, such as seagrass meadows, can harbour diverse epifaunal assemblages and may constitute important feeding grounds to fish, little is known about the epifaunal assemblages associated with tropical seaweed beds. We investigated the abundance, biomass and taxon richness of the mobile epifaunal community (≥1 mm) of tropical East African seaweed beds, as well as the abundance of invertivorous fishes, and compared it with that of closely situated seagrass meadows, to establish the ecological role of seaweed beds as habitat for epifauna as well as potential feeding grounds for fish. The results showed that seaweed beds had a higher abundance of mobile epifauna (mean ± SD: 10,600 ± 6000 vs 3700 ± 2800 per m2) than seagrass meadows, as well as a higher invertebrate biomass (35.9 ± 46.8 vs 1.9 ± 2.1 g per m2) and taxon richness (32.7 ± 11.8 vs 19.1 ± 6.3 taxa per sample), despite having a lower macrophyte biomass. Additionally, the high abundance of invertivorous fishes found in seaweed beds indicates that they act as important feeding grounds to several fish species in the region.

  4. Epiphyte presence and seagrass species identity influence rates of herbivory in Mediterranean seagrass meadows

    NASA Astrophysics Data System (ADS)

    Marco-Méndez, Candela; Ferrero-Vicente, Luis Miguel; Prado, Patricia; Heck, Kenneth L.; Cebrián, Just; Sánchez-Lizaso, Jose Luis

    2015-03-01

    Herbivory on Mediterranean seagrass species is generally low compared to consumption of some other temperate and tropical species of seagrasses. In this study we: (1) investigate the feeding preference of the two dominant Mediterranean seagrass herbivores, the sea urchin Paracentrotus lividus and the fish Sarpa salpa, on Posidonia oceanica and Cymodocea nodosa and (2) elucidate the role of epiphytes in herbivore choices. We assessed consumption rates by tethering seagrass shoots, and preferences by food choice experiments with the following paired combinations: 1) Epiphytized leaves of both C. nodosa vs. P. oceanica (CE vs PE); 2) Non-epiphytized leaves of C. nodosa vs. P. oceanica (CNE vs. PNE); 3) Epiphytized vs non-epiphytized leaves of C. nodosa (CE vs. CNE) and 4) Epiphytized vs non-epiphytized leaves of P. oceanica (PE vs PNE). We found that preference for C. nodosa was weak for S. salpa, but strong for P. lividus, the species responsible for most consumption at our study. Overall both herbivores showed preference for epiphytized leaves. The higher nutritional quality of C. nodosa leaves and epiphytes together with the high coverage and diversity of the epiphyte community found on its leaves help explain the higher levels of herbivory recorded on epiphyted leaves of C. nodosa. Other factors such as seagrass accessibility, herbivore mobility and size, and behavioral responses to predation risks, may also affect the intensity of seagrass herbivory, and studies addressing the interactions with these factors are needed to improve our understanding of the nature, extent and implications of herbivory in coastal ecosystems.

  5. Bed Bugs

    EPA Pesticide Factsheets

    Prevent, identify, and treat bed bug infestations using EPA’s step-by-step guides, based on IPM principles. Find pesticides approved for bed bug control, check out the information clearinghouse, and dispel bed bug myths.

  6. Draft Genome Sequence of Marinobacter hydrocarbonoclasticus Strain STW2, a Polycyclic Aromatic Hydrocarbon-Degrading and Denitrifying Bacterium from the Rhizosphere of Seagrass Enhalus acodoides

    PubMed Central

    Ling, Juan; Lin, Liyun; Zhang, Yanying; Lin, Xiancheng; Ahamad, Manzoor; Zhou, Weiguo

    2017-01-01

    ABSTRACT Here, we report the draft genome sequence of Marinobacter hydrocarbonoclasticus strain STW2, which was isolated from the rhizosphere of seagrass Enhalus acodoides. This study will facilitate future studies on the genetic pathways of marine microbes capable of both polycyclic aromatic hydrocarbon degradation and nitrate reduction. PMID:28232431

  7. Effects of bioturbation on seagrasses: Implications for management and restoration

    EPA Science Inventory

    Marine and estuarine fauna can diminish or enhance seagrass condition simply as a result of their burrowing, excavating, re-working, and feeding activities (e.g., bioturbation). We present the first comprehensive review of the effects of bioturbators on seagrasses and associated ...

  8. Seagrass epiphytes: useful indicator, potential biological criterion, or forlorn hope?

    EPA Science Inventory

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experim...

  9. Effects of bioturbation on seagrasses: Implications for management and restoration

    EPA Science Inventory

    Marine and estuarine fauna can diminish or enhance seagrass condition simply as a result of their burrowing, excavating, re-working, and feeding activities (e.g., bioturbation). We present the first comprehensive review of the effects of bioturbators on seagrasses and associated ...

  10. Abstract Constructions.

    ERIC Educational Resources Information Center

    Pietropola, Anne

    1998-01-01

    Describes a lesson designed to culminate a year of eighth-grade art classes in which students explore elements of design and space by creating 3-D abstract constructions. Outlines the process of using foam board and markers to create various shapes and optical effects. (DSK)

  11. Abstract Planters.

    ERIC Educational Resources Information Center

    Burnham, Barrie

    2001-01-01

    Describes an art project where students create slab planters that are functional clay objects. Discusses how the students prepare their drawings for the planter and how to create the planter. Explains that the subject matter is depicted in a progression from reality to abstraction. (CMK)

  12. Research Abstracts.

    ERIC Educational Resources Information Center

    Plotnik, Eric

    2001-01-01

    Presents six research abstracts from the ERIC (Educational Resources Information Center) database. Topics include: effectiveness of distance versus traditional on-campus education; improved attribution recall from diversification of environmental context during computer-based instruction; qualitative analysis of situated Web-based learning;…

  13. Research Abstracts.

    ERIC Educational Resources Information Center

    Plotnick, Eric

    2001-01-01

    Presents research abstracts from the ERIC Clearinghouse on Information and Technology. Topics include: classroom communication apprehension and distance education; outcomes of a distance-delivered science course; the NASA/Kennedy Space Center Virtual Science Mentor program; survey of traditional and distance learning higher education members;…

  14. Research Abstracts.

    ERIC Educational Resources Information Center

    Plotnik, Eric

    2001-01-01

    Presents six research abstracts from the ERIC (Educational Resources Information Center) database. Topics include: effectiveness of distance versus traditional on-campus education; improved attribution recall from diversification of environmental context during computer-based instruction; qualitative analysis of situated Web-based learning;…

  15. Photosynthethic carbon reduction by seagrasses exposed to ultraviolet B radiation

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The species of seagrasses were selected on the basis of their dominance in the marine system, contribution to total productivity, and importance to the life histories of organisms in the Indian River lagoon system along the central Florida east coast. The three seagrasses were Halophilia engelmannii, Halodule wrightii, and Syringodium filiforme. These seagrasses form an excellent experimental system as their areas of dominance fall more or less along a natural gradient of UV-B and photosynthetically active radiation (PAR) penetration. The sensitivity of photosynthesis in the seagrasses was determined and their photosynthetic response to levels of UV-B simulating atmospheric ozone depletion was monitored. Further experiments explore the possible attenuation or repair of UV-B induced photosynthetic inhibition by PAR, the role of epiphytic growth upon seagrasses as a protective UV-B shield, and the inhibition of photosynthesis in response to UV-A is studied.

  16. CARBON AND NITROGEN ALLOCATION MODEL FOR THE SUB-TROPICAL SEAGRASS THALASSIA TESTUDINUM AND THE TEMPERATE SEAGRASS ZOSTER MARINA

    EPA Science Inventory

    Our understanding of seagrass physiology is based on crude estimates of production and biomass. To better understand the complex physiological relationships between the plants and the environment we developed a model of carbon and nitrogen allocation in the sub-tropical seagrass ...

  17. CARBON AND NITROGEN ALLOCATION MODEL FOR THE SUB-TROPICAL SEAGRASS THALASSIA TESTUDINUM AND THE TEMPERATE SEAGRASS ZOSTER MARINA

    EPA Science Inventory

    Our understanding of seagrass physiology is based on crude estimates of production and biomass. To better understand the complex physiological relationships between the plants and the environment we developed a model of carbon and nitrogen allocation in the sub-tropical seagrass ...

  18. Bed bugs.

    PubMed

    Foulke, Galen T; Anderson, Bryan E

    2014-09-01

    The term bed bug is applied to 2 species of genus Cimex: lectularius describes the common or temperate bed bug, and hemipterus its tropical cousin. Cimex lectularius is aptly named; its genus and species derive from the Latin words for bug and bed, respectively. Though the tiny pest is receiving increased public attention and scrutiny, the bed bug is hardly a new problem.

  19. Global Abstracts.

    PubMed

    Weber, Ellen J

    2017-10-01

    Editor's note: EMJ has partnered with the journals of multiple international emergency medicine societies to share from each a highlighted research study, as selected by their editors. This edition will feature an abstract from each publication. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  20. CARBON BUDGET FOR A SUB-TROPICAL SEAGRASS DOMINATED COASTAL LAGOON: HOW IMPORTANT ARE SEAGRASSES TO TOTAL ECOSYSTEM NET PRIMARY PRODUCTION?

    EPA Science Inventory

    Seagrasses dominate macrophyte biomass in many estuaries. Historically, it has been assumed that because of the large standing stock seagrasses also dominate primary production. We tested this assumption by developing 3 carbon budgets to examine the contribution of autotrophic ...

  1. CARBON BUDGET FOR A SUB-TROPICAL SEAGRASS DOMINATED COASTAL LAGOON: HOW IMPORTANT ARE SEAGRASSES TO TOTAL ECOSYSTEM NET PRIMARY PRODUCTION?

    EPA Science Inventory

    Seagrasses dominate macrophyte biomass in many estuaries. Historically, it has been assumed that because of the large standing stock seagrasses also dominate primary production. We tested this assumption by developing 3 carbon budgets to examine the contribution of autotrophic ...

  2. Accelerating loss of seagrasses across the globe threatens coastal ecosystems

    PubMed Central

    Waycott, Michelle; Duarte, Carlos M.; Carruthers, Tim J. B.; Orth, Robert J.; Dennison, William C.; Olyarnik, Suzanne; Calladine, Ainsley; Fourqurean, James W.; Heck, Kenneth L.; Hughes, A. Randall; Kendrick, Gary A.; Kenworthy, W. Judson; Short, Frederick T.; Williams, Susan L.

    2009-01-01

    Coastal ecosystems and the services they provide are adversely affected by a wide variety of human activities. In particular, seagrass meadows are negatively affected by impacts accruing from the billion or more people who live within 50 km of them. Seagrass meadows provide important ecosystem services, including an estimated $1.9 trillion per year in the form of nutrient cycling; an order of magnitude enhancement of coral reef fish productivity; a habitat for thousands of fish, bird, and invertebrate species; and a major food source for endangered dugong, manatee, and green turtle. Although individual impacts from coastal development, degraded water quality, and climate change have been documented, there has been no quantitative global assessment of seagrass loss until now. Our comprehensive global assessment of 215 studies found that seagrasses have been disappearing at a rate of 110 km2 yr−1 since 1980 and that 29% of the known areal extent has disappeared since seagrass areas were initially recorded in 1879. Furthermore, rates of decline have accelerated from a median of 0.9% yr−1 before 1940 to 7% yr−1 since 1990. Seagrass loss rates are comparable to those reported for mangroves, coral reefs, and tropical rainforests and place seagrass meadows among the most threatened ecosystems on earth. PMID:19587236

  3. Seagrass ecosystems as a globally significant carbon stock

    NASA Astrophysics Data System (ADS)

    Fourqurean, James W.; Duarte, Carlos M.; Kennedy, Hilary; Marbà, Núria; Holmer, Marianne; Mateo, Miguel Angel; Apostolaki, Eugenia T.; Kendrick, Gary A.; Krause-Jensen, Dorte; McGlathery, Karen J.; Serrano, Oscar

    2012-07-01

    The protection of organic carbon stored in forests is considered as an important method for mitigating climate change. Like terrestrial ecosystems, coastal ecosystems store large amounts of carbon, and there are initiatives to protect these `blue carbon' stores. Organic carbon stocks in tidal salt marshes and mangroves have been estimated, but uncertainties in the stores of seagrass meadows--some of the most productive ecosystems on Earth--hinder the application of marine carbon conservation schemes. Here, we compile published and unpublished measurements of the organic carbon content of living seagrass biomass and underlying soils in 946 distinct seagrass meadows across the globe. Using only data from sites for which full inventories exist, we estimate that, globally, seagrass ecosystems could store as much as 19.9Pg organic carbon; according to a more conservative approach, in which we incorporate more data from surface soils and depth-dependent declines in soil carbon stocks, we estimate that the seagrass carbon pool lies between 4.2 and 8.4Pg carbon. We estimate that present rates of seagrass loss could result in the release of up to 299Tg carbon per year, assuming that all of the organic carbon in seagrass biomass and the top metre of soils is remineralized.

  4. Measuring the role of seagrasses in regulating sediment surface elevation

    USGS Publications Warehouse

    Potouroglou, Maria; Bull, James C.; Krauss, Ken W.; Kennedy, Hilary A.; Fusi, Marco; Daffonchio, Daniele; Mangora, Mwita M.; Githaiga, Michael N.; Diele, Karen; Huxham, Mark

    2017-01-01

    Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other ‘blue carbon’ habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.

  5. Phytotoxicity of four photosystem II herbicides to tropical seagrasses.

    PubMed

    Flores, Florita; Collier, Catherine J; Mercurio, Philip; Negri, Andrew P

    2013-01-01

    Coastal waters of the Great Barrier Reef (GBR) are contaminated with agricultural pesticides, including the photosystem II (PSII) herbicides which are the most frequently detected at the highest concentrations. Designed to control weeds, these herbicides are equally potent towards non-target marine species, and the close proximity of seagrass meadows to flood plumes has raised concerns that seagrasses may be the species most threatened by herbicides from runoff. While previous work has identified effects of PSII herbicides on the photophysiology, growth and mortality in seagrass, there is little comparative quantitative toxicity data for seagrass. Here we applied standard ecotoxicology protocols to quantify the concentrations of four priority PSII herbicides that inhibit photochemistry by 10, 20 and 50% (IC10, IC20 and IC50) over 72 h in two common seagrass species from the GBR lagoon. The photosystems of seagrasses Zosteramuelleri and Haloduleuninervis were shown to be generally more sensitive to the PSII herbicides Diuron, Atrazine, Hexazinone and Tebuthiuron than corals and tropical microalgae. The herbicides caused rapid inhibition of effective quantum yield (∆F/F m '), indicating reduced photosynthesis and maximum effective yields (Fv/Fm ) corresponding to chronic damage to PSII. The PSII herbicide concentrations which affected photosynthesis have been exceeded in the GBR lagoon and all of the herbicides inhibited photosynthesis at concentrations lower than current marine park guidelines. There is a strong likelihood that the impacts of light limitation from flood plumes and reduced photosynthesis from PSII herbicides exported in the same waters would combine to affect seagrass productivity. Given that PSII herbicides have been demonstrated to affect seagrass at environmental concentrations, we suggest that revision of environmental guidelines and further efforts to reduce PSII herbicide concentrations in floodwaters may both help protect seagrass meadows of

  6. Phytotoxicity of Four Photosystem II Herbicides to Tropical Seagrasses

    PubMed Central

    Flores, Florita; Collier, Catherine J.; Mercurio, Philip; Negri, Andrew P.

    2013-01-01

    Coastal waters of the Great Barrier Reef (GBR) are contaminated with agricultural pesticides, including the photosystem II (PSII) herbicides which are the most frequently detected at the highest concentrations. Designed to control weeds, these herbicides are equally potent towards non-target marine species, and the close proximity of seagrass meadows to flood plumes has raised concerns that seagrasses may be the species most threatened by herbicides from runoff. While previous work has identified effects of PSII herbicides on the photophysiology, growth and mortality in seagrass, there is little comparative quantitative toxicity data for seagrass. Here we applied standard ecotoxicology protocols to quantify the concentrations of four priority PSII herbicides that inhibit photochemistry by 10, 20 and 50% (IC10, IC20 and IC50) over 72 h in two common seagrass species from the GBR lagoon. The photosystems of seagrasses Zosteramuelleri and Haloduleuninervis were shown to be generally more sensitive to the PSII herbicides Diuron, Atrazine, Hexazinone and Tebuthiuron than corals and tropical microalgae. The herbicides caused rapid inhibition of effective quantum yield (∆F/Fm′), indicating reduced photosynthesis and maximum effective yields (Fv/Fm) corresponding to chronic damage to PSII. The PSII herbicide concentrations which affected photosynthesis have been exceeded in the GBR lagoon and all of the herbicides inhibited photosynthesis at concentrations lower than current marine park guidelines. There is a strong likelihood that the impacts of light limitation from flood plumes and reduced photosynthesis from PSII herbicides exported in the same waters would combine to affect seagrass productivity. Given that PSII herbicides have been demonstrated to affect seagrass at environmental concentrations, we suggest that revision of environmental guidelines and further efforts to reduce PSII herbicide concentrations in floodwaters may both help protect seagrass meadows of

  7. Fish responses to experimental fragmentation of seagrass habitat.

    PubMed

    Macreadie, Peter I; Hindell, Jeremy S; Jenkins, Gregory P; Connolly, Rod M; Keough, Michael J

    2009-06-01

    Understanding the consequences of habitat fragmentation has come mostly from comparisons of patchy and continuous habitats. Because fragmentation is a process, it is most accurately studied by actively fragmenting large patches into multiple smaller patches. We fragmented artificial seagrass habitats and evaluated the impacts of fragmentation on fish abundance and species richness over time (1 day, 1 week, 1 month). Fish assemblages were compared among 4 treatments: control (single, continuous 9-m(2) patches); fragmented (single, continuous 9-m(2) patches fragmented to 4 discrete 1-m(2) patches); prefragmented/patchy (4 discrete 1-m(2) patches with the same arrangement as fragmented); and disturbance control (fragmented then immediately restored to continuous 9-m(2) patches). Patchy seagrass had lower species richness than actively fragmented seagrass (up to 39% fewer species after 1 week), but species richness in fragmented treatments was similar to controls. Total fish abundance did not vary among treatments and therefore was unaffected by fragmentation, patchiness, or disturbance caused during fragmentation. Patterns in species richness and abundance were consistent 1 day, 1 week, and 1 month after fragmentation. The expected decrease in fish abundance from reduced total seagrass area in fragmented and patchy seagrass appeared to be offset by greater fish density per unit area of seagrass. If fish prefer to live at edges, then the effects of seagrass habitat loss on fish abundance may have been offset by the increase (25%) in seagrass perimeter in fragmented and patchy treatments. Possibly there is some threshold of seagrass patch connectivity below which fish abundances cannot be maintained. The immediate responses of fish to experimental habitat fragmentation provided insights beyond those possible from comparisons of continuous and historically patchy habitat. ©2009 Society for Conservation Biology.

  8. Recovery of a top predator mediates negative eutrophic effects on seagrass

    PubMed Central

    Hughes, Brent B.; Eby, Ron; Van Dyke, Eric; Tinker, M. Tim; Marks, Corina I.; Johnson, Kenneth S.; Wasson, Kerstin

    2013-01-01

    A fundamental goal of the study of ecology is to determine the drivers of habitat-forming vegetation, with much emphasis given to the relative importance to vegetation of “bottom-up” forces such as the role of nutrients and “top-down” forces such as the influence of herbivores and their predators. For coastal vegetation (e.g., kelp, seagrass, marsh, and mangroves) it has been well demonstrated that alterations to bottom-up forcing can cause major disturbances leading to loss of dominant vegetation. One such process is anthropogenic nutrient loading, which can lead to major changes in the abundance and species composition of primary producers, ultimately affecting important ecosystem services. In contrast, much less is known about the relative importance of apex predators on coastal vegetated ecosystems because most top predator populations have been depleted or lost completely. Here we provide evidence that an unusual four-level trophic cascade applies in one such system, whereby a top predator mitigates the bottom-up influences of nutrient loading. In a study of seagrass beds in an estuarine ecosystem exposed to extreme nutrient loading, we use a combination of a 50-y time series analysis, spatial comparisons, and mesocosm and field experiments to demonstrate that sea otters (Enhydra lutris) promote the growth and expansion of eelgrass (Zostera marina) through a trophic cascade, counteracting the negative effects of agriculturally induced nutrient loading. Our results add to a small but growing body of literature illustrating that significant interactions between bottom-up and top-down forces occur, in this case with consequences for the conservation of valued ecosystem services provided by seagrass. PMID:23983266

  9. Recovery of a top predator mediates negative eutrophic effects on seagrass

    USGS Publications Warehouse

    Hughes, Brent B.; Eby, Ron; Van Dyke, Eric; Tinker, M. Tim; Marks, Corina I.; Johnson, Kenneth S.; Wasson, Kerstin

    2013-01-01

    A fundamental goal of the study of ecology is to determine the drivers of habitat-forming vegetation, with much emphasis given to the relative importance to vegetation of “bottom-up” forces such as the role of nutrients and “top-down” forces such as the influence of herbivores and their predators. For coastal vegetation (e.g., kelp, seagrass, marsh, and mangroves) it has been well demonstrated that alterations to bottom-up forcing can cause major disturbances leading to loss of dominant vegetation. One such process is anthropogenic nutrient loading, which can lead to major changes in the abundance and species composition of primary producers, ultimately affecting important ecosystem services. In contrast, much less is known about the relative importance of apex predators on coastal vegetated ecosystems because most top predator populations have been depleted or lost completely. Here we provide evidence that an unusual four-level trophic cascade applies in one such system, whereby a top predator mitigates the bottom-up influences of nutrient loading. In a study of seagrass beds in an estuarine ecosystem exposed to extreme nutrient loading, we use a combination of a 50-y time series analysis, spatial comparisons, and mesocosm and field experiments to demonstrate that sea otters (Enhydra lutris) promote the growth and expansion of eelgrass (Zostera marina) through a trophic cascade, counteracting the negative effects of agriculturally induced nutrient loading. Our results add to a small but growing body of literature illustrating that significant interactions between bottom-up and top-down forces occur, in this case with consequences for the conservation of valued ecosystem services provided by seagrass.

  10. Review: Host-pathogen dynamics of seagrass diseases under future global change.

    PubMed

    Sullivan, Brooke K; Trevathan-Tackett, Stacey M; Neuhauser, Sigrid; Govers, Laura L

    2017-09-28

    Human-induced global change is expected to amplify the disease risk for marine biota. However, the role of disease in the rapid global decline of seagrass is largely unknown. Global change may enhance seagrass susceptibility to disease through enhanced physiological stress, while simultaneously promoting pathogen development. This review outlines the characteristics of disease-forming organisms and potential impacts of global change on three groups of known seagrass pathogens: labyrinthulids, oomycetes and Phytomyxea. We propose that hypersalinity, climate warming and eutrophication pose the greatest risk for increasing frequency of disease outbreaks in seagrasses by increasing seagrass stress and lowering seagrass resilience. In some instances, global change may also promote pathogen development. However, there is currently a paucity of information on these seagrass pathosystems. We emphasise the need to expand current research to better understand the seagrass-pathogen relationships, serving to inform predicative modelling and management of seagrass disease under future global change scenarios. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Temporal variation of intertidal seagrass in Southern China (2008-2014)

    NASA Astrophysics Data System (ADS)

    Qiu, Guanglong; Short, Frederick T.; Fan, Hangqing; Liu, Guohua

    2017-07-01

    Understanding the temporal dynamics of seagrasses and the major influences on seagrass growth is critical for seagrass habitat conservation and administration. However, little work has been done regarding these issues in southern China. To examine inter-annual and seasonal variations of the intertidal Halophila ovalis community in southern China, we conducted quarterly sampling using the SeagrassNet methodology and assessed environmental conditions as well as direct anthropogenic impacts on the seagrass meadow from July 2008 to October 2014. Our study demonstrated strong inter-annual and seasonal dynamics of the intertidal seagrass meadow in the study area. Generally, the community performed best (highest seagrass cover, leaf area, shoot density, total biomass) in summer and worst in spring among the 4 seasons. The temporal variations in the seagrass community attributes (e.g. above-ground biomass) were significantly affected by precipitation, atmospheric visibility, and salinity, while leaf width was significantly negatively correlated with temperature, atmospheric visibility and salinity. Temperature was a major factor influencing the seagrass community (both macroalgae and seagrass), with temperature data showing an inverse relationship between seagrass and macroalgae. The above-ground: below-ground biomass ratio and leaf width of H. ovalis were the most sensitive plant parameters monitored when assessing environmental interactions. Human physical disturbances did not have a significant effect on seagrass dynamics in the study area. We concluded that long-term monitoring (like SeagrassNet) is valuable in understanding the relationship between environmental variables and seagrasses.

  12. Algerian Abstract

    NASA Image and Video Library

    2017-09-27

    Algerian Abstract - April 8th, 1985 Description: What look like pale yellow paint streaks slashing through a mosaic of mottled colors are ridges of wind-blown sand that make up Erg Iguidi, an area of ever-shifting sand dunes extending from Algeria into Mauritania in northwestern Africa. Erg Iguidi is one of several Saharan ergs, or sand seas, where individual dunes often surpass 500 meters-nearly a third of a mile-in both width and height. Credit: USGS/NASA/Landsat 5 To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/ NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

  13. Contribution of different functional groups to the diet of major predatory fishes at a seagrass meadow in northeastern Japan

    NASA Astrophysics Data System (ADS)

    Yamada, Katsumasa; Hori, Masakazu; Tanaka, Yoshiyuki; Hasegawa, Natsuki; Nakaoka, Masahiro

    2010-01-01

    We examined the variation in habitat use and diet of three dominant fish species ( Myoxocephalus brandti, Pholidapus dybowskii, and Pholis crassispina) in a seagrass meadow in the Akkeshi-ko estuary in northeastern Japan, where broad and dense Zostera marina beds exist, using a semi-quantitative census of the fishes and analyses of their stomach contents. Differences among the three fish species in the temporal variation in abundance of each age class (mainly 1- and 2-year age classes) indicated that the temporal pattern of utilization of the seagrass meadow were different among them. In the semi-quantitative dietary analysis, two prey categories, i.e., taxonomic group (order and suborder) and functional group, were used to explain the variation in prey composition with size-dependent changes. The six prey functional groups were classified based on the ecological traits of the prey, i.e., trophic level, size, and life type (habitat and behavior). Ontogenetic shifts in prey of the three fish species could be fully explained by a combination of the two prey categories, and not by the use of only one category (taxonomic or functional group). The pattern of ontogenetic shifts in prey differed among the fish species and size (age) classes. These results indicate that segregation of habitat (seagrass meadow) and prey group (taxonomic and functional group) is performed among the three species, which may contribute to their coexistence in this estuary.

  14. Geospatial interface and model for predicting potential seagrass habitat

    EPA Science Inventory

    Restoration of ecosystem services provided by seagrass habitats in estuaries requires a clear understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We have developed a geos...

  15. Nonnutrient Anthropogenic Chemicals in Seagrass Ecosystems: Fate and Effects

    EPA Science Inventory

    Literature reviews have been published for seagrass taxonomy, geographical distribution, species diversity, grazer-epiphyte interactions, morphology, physiology, salinity requirements, and nutrient impacts (Schaffer 1995; Jernakoff et al. 1996; Touchette and Burholder 2000; Borto...

  16. MAPPING BURROWING SHRIMP AND SEAGRASS IN YAQUINA ESTUARY

    EPA Science Inventory

    Burrowing shrimp and seagrasses create extensive intertidal and shallow subtidal habitats within Pacific NW estuaries. Maps of their populations are useful to inform estuarine managers of locations that deserve special consideration for conservation, and to inform oyster farmers...

  17. Geospatial interface and model for predicting potential seagrass habitat

    EPA Science Inventory

    Restoration of ecosystem services provided by seagrass habitats in estuaries requires a clear understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We have developed a geos...

  18. MAPPING BURROWING SHRIMP AND SEAGRASS IN YAQUINA ESTUARY

    EPA Science Inventory

    Burrowing shrimp and seagrasses create extensive intertidal and shallow subtidal habitats within Pacific NW estuaries. Maps of their populations are useful to inform estuarine managers of locations that deserve special consideration for conservation, and to inform oyster farmers...

  19. Nonnutrient Anthropogenic Chemicals in Seagrass Ecosystems: Fate and Effects

    EPA Science Inventory

    Literature reviews have been published for seagrass taxonomy, geographical distribution, species diversity, grazer-epiphyte interactions, morphology, physiology, salinity requirements, and nutrient impacts (Schaffer 1995; Jernakoff et al. 1996; Touchette and Burholder 2000; Borto...

  20. Contribution of seagrass plants to CO2 capture in a tropical seagrass meadow under experimental disturbance.

    PubMed

    Deyanova, Diana; Gullström, Martin; Lyimo, Liberatus D; Dahl, Martin; Hamisi, Mariam I; Mtolera, Matern S P; Björk, Mats

    2017-01-01

    Coastal vegetative habitats are known to be highly productive environments with a high ability to capture and store carbon. During disturbance this important function could be compromised as plant photosynthetic capacity, biomass, and/or growth are reduced. To evaluate effects of disturbance on CO2 capture in plants we performed a five-month manipulative experiment in a tropical seagrass (Thalassia hemprichii) meadow exposed to two intensity levels of shading and simulated grazing. We assessed CO2 capture potential (as net CO2 fixation) using areal productivity calculated from continuous measurements of diel photosynthetic rates, and estimates of plant morphology, biomass and productivity/respiration (P/R) ratios (from the literature). To better understand the plant capacity to coping with level of disturbance we also measured plant growth and resource allocation. We observed substantial reductions in seagrass areal productivity, biomass, and leaf area that together resulted in a negative daily carbon balance in the two shading treatments as well as in the high-intensity simulated grazing treatment. Additionally, based on the concentrations of soluble carbohydrates and starch in the rhizomes, we found that the main reserve sources for plant growth were reduced in all treatments except for the low-intensity simulated grazing treatment. If permanent, these combined adverse effects will reduce the plants' resilience and capacity to recover after disturbance. This might in turn have long-lasting and devastating effects on important ecosystem functions, including the carbon sequestration capacity of the seagrass system.

  1. Rapid discrimination between four seagrass species using hybrid analysis.

    PubMed

    Osathanunkul, M; Madesis, P; Ounjai, S; Suwannapoom, C; Jampeetong, A

    2015-04-27

    Biological species are traditionally identified based on their morphological features and the correct identification of species is critical in biological studies. However, some plant types, such as seagrass, are taxonomically problematic and difficult to identify. Furthermore, closely related seagrass species, such as Halophila spp, form a taxonomically unresolved complex. Although some seagrass taxa are easy to recognize, most species are difficult to identify without skilled taxonomic or molecular techniques. Barcoding coupled with High Resolution Melting analysis (BAR-HRM) offers a potentially reliable, rapid, and cost-effective method to confirm species. Here, DNA information of two chloroplast loci was used in combination with HRM analysis to discriminate four species of seagrass collected off the southern coast of Thailand. A distinct melting curve presenting one inflection point was generated for each species using rbcL primers. While the melting profiles of Cymodocea rotundata and Cymodocea serrulata were not statistically different, analysis of the normalized HRM curves produced with the rpoC primers allowed for their discrimination. The Bar-HRM technique showed promise in discriminating seagrass species and with further adaptations and improvements, could make for an effective and power tool for confirming seagrass species.

  2. The effects of water parameters on monthly seagrass percentage cover in Lawas, East Malaysia.

    PubMed

    Ahmad-Kamil, E I; Ramli, R; Jaaman, S A; Bali, J; Al-Obaidi, J R

    2013-01-01

    Seagrass is a valuable marine ecosystem engineer. However, seagrass population is declining worldwide. The lack of seagrass research in Malaysia raises questions about the status of seagrasses in the country. The seagrasses in Lawas, which is part of the coral-mangrove-seagrass complex, have never been studied in detail. In this study, we examine whether monthly changes of seagrass population in Lawas occurred. Data on estimates of seagrass percentage cover and water physicochemical parameters (pH, turbidity, salinity, temperature, and dissolved oxygen) were measured at 84 sampling stations established within the study area from June 2009 to May 2010. Meteorological data such as total rainfall, air temperature, and Southern Oscillation Index were also investigated. Our results showed that (i) the monthly changes of seagrass percentage cover are significant, (ii) the changes correlated significantly with turbidity measurements, and (iii) weather changes affected the seagrass populations. Our study indicates seagrass percentage increased during the El-Nino period. These results suggest that natural disturbances such as weather changes affect seagrass populations. Evaluation of land usage and measurements of other water physicochemical parameters (such as heavy metal, pesticides, and nutrients) should be considered to assess the health of seagrass ecosystem at the study area.

  3. The Effects of Water Parameters on Monthly Seagrass Percentage Cover in Lawas, East Malaysia

    PubMed Central

    Ahmad-Kamil, E. I.; Ramli, R.; Jaaman, S. A.; Bali, J.; Al-Obaidi, J. R.

    2013-01-01

    Seagrass is a valuable marine ecosystem engineer. However, seagrass population is declining worldwide. The lack of seagrass research in Malaysia raises questions about the status of seagrasses in the country. The seagrasses in Lawas, which is part of the coral-mangrove-seagrass complex, have never been studied in detail. In this study, we examine whether monthly changes of seagrass population in Lawas occurred. Data on estimates of seagrass percentage cover and water physicochemical parameters (pH, turbidity, salinity, temperature, and dissolved oxygen) were measured at 84 sampling stations established within the study area from June 2009 to May 2010. Meteorological data such as total rainfall, air temperature, and Southern Oscillation Index were also investigated. Our results showed that (i) the monthly changes of seagrass percentage cover are significant, (ii) the changes correlated significantly with turbidity measurements, and (iii) weather changes affected the seagrass populations. Our study indicates seagrass percentage increased during the El-Nino period. These results suggest that natural disturbances such as weather changes affect seagrass populations. Evaluation of land usage and measurements of other water physicochemical parameters (such as heavy metal, pesticides, and nutrients) should be considered to assess the health of seagrass ecosystem at the study area. PMID:24163635

  4. Seagrasses in tropical Australia, productive and abundant for decades decimated overnight.

    PubMed

    Pollard, Peter C; Greenway, Margaret

    2013-03-01

    Seagrass ecosystems provide unique coastal habitats critical to the life cycle of many species. Seagrasses are a major store of organic carbon. While seagrasses are globally threatened and in decline, in Cairns Harbour, Queensland, on the tropical east coast of Australia, they have flourished. We assessed seagrass distribution in Cairns Harbour between 1953 and 2012 from historical aerial photographs, Google map satellite images, existing reports and our own surveys of their distribution. Seasonal seagrass physiology was assessed through gross primary production, respiration and photosynthetic characteristics of three seagrass species, Cymodocea serrulata, Thalassia hemprichii and Zostera muelleri. At the higher water temperatures of summer, respiration rates increased in all three species, as did their maximum rates of photosynthesis. All three seagrasses achieved maximum rates of photosynthesis at low tide and when they were exposed. For nearly six decades there was little change in seagrass distribution in Cairns Harbour. This was most likely because the seagrasses were able to achieve sufficient light for growth during intertidal and low tide periods. With historical data of seagrass distribution and measures of species production and respiration, could seagrass survival in a changing climate be predicted? Based on physiology, our results predicted the continued maintenance of the Cairns Harbour seagrasses, although one species was more susceptible to thermal disturbance. However, in 2011 an unforeseen episodic disturbance - Tropical Cyclone Yasi - and associated floods lead to the complete and catastrophic loss of all the seagrasses in Cairns Harbour.

  5. PRODUCTION OF PLANT GROWTH PROMOTING SUBSTANCES IN BACTERIAL ISOLATES FROM THE SEAGRASS RHIZOSPHERE

    EPA Science Inventory

    Plants and rhizosphere bacteria have evolved chemical signals that enable their mutual growth. These relationships have been well investigated with agriculturally important plants, but not in seagrasses, which are important to the stability of estuaries. Seagrasses are rooted in ...

  6. PRODUCTION OF PLANT GROWTH PROMOTING SUBSTANCES IN BACTERIAL ISOLATES FROM THE SEAGRASS RHIZOSPHERE

    EPA Science Inventory

    Plants and rhizosphere bacteria have evolved chemical signals that enable their mutual growth. These relationships have been well investigated with agriculturally important plants, but not in seagrasses, which are important to the stability of estuaries. Seagrasses are rooted in ...

  7. Suitability of seagrasses and submerged aquatic vegetation as indicators of eutrophication

    EPA Science Inventory

    Rooted submerged aquatic vegetation (SAV) encompasses a large diversity of species that range from obligate halophytes such as, seagrasses, to euryhaline species and freshwater obligates. All seagrass and SAV provide key biological functions within the enclosed bays, estuaries, a...

  8. Patterns of shading tolerance determined from experimental light reduction studies of seagrasses

    EPA Science Inventory

    An extensive review of the experimental literature on seagrass shading evaluated the relationship between experimental light reductions, duration of experiment and seagrass response metrics to determine whether there were consistent statistical patterns. There were highly signif...

  9. UTILIZATION OF DOC FROM SEAGRASS RHIZOMES BY SEDIMENT BACTERIA: 13C TRACER EXPERIMENTS AND MODELLING

    EPA Science Inventory

    Seagrasses are widely recognized as contributing to net ecosystem primary production and to supporting heterotrophy in estuarine systems. We investigated the linkage between seagrass (Thalassia testudinum) rhizosphere carbon exudation and sediment bacteria. In microcosms, we si...

  10. Suitability of seagrasses and submerged aquatic vegetation as indicators of eutrophication

    EPA Science Inventory

    Rooted submerged aquatic vegetation (SAV) encompasses a large diversity of species that range from obligate halophytes such as, seagrasses, to euryhaline species and freshwater obligates. All seagrass and SAV provide key biological functions within the enclosed bays, estuaries, a...

  11. UTILIZATION OF DOC FROM SEAGRASS RHIZOMES BY SEDIMENT BACTERIA: 13C TRACER EXPERIMENTS AND MODELLING

    EPA Science Inventory

    Seagrasses are widely recognized as contributing to net ecosystem primary production and to supporting heterotrophy in estuarine systems. We investigated the linkage between seagrass (Thalassia testudinum) rhizosphere carbon exudation and sediment bacteria. In microcosms, we si...

  12. Turbulent mixing and fluid transport within Florida Bay seagrass meadows

    NASA Astrophysics Data System (ADS)

    Hansen, Jennifer C. R.; Reidenbach, Matthew A.

    2017-10-01

    Seagrasses serve an important function in the ecology of Florida Bay, providing critical nursery habitat and a food source for a variety of organisms. They also create significant benthic structure that induces drag, altering local hydrodynamics that can influence mixing and nutrient dynamics. Thalassia testudinum seagrass meadows were investigated to determine how shoot density and morphometrics alter local wave conditions, the generation of turbulence, and fluid exchange above and within the canopy. Sparsely vegetated and densely vegetated meadows were monitored, with shoot densities of 259 ± 26 and 484 ± 78 shoots m-2, respectively. The temporal and spatial structure of velocity and turbulence were measured using acoustic Doppler velocimeters and an in situ particle image velocimetry (PIV) system positioned both above and within the seagrass canopy. The retention of fluid within the canopy was determined by examining e-folding times calculated from the concentration curves of dye plumes released within the seagrass canopy. Results show that a shear layer with an inflection point develops at the top of the seagrass canopy, which generates instabilities that impart turbulence into the seagrass meadow. Compared to the overlying water column, turbulence was enhanced within the sparse canopy due to flow interaction with the seagrass blades, but reduced within the dense canopy. Wave generated oscillatory motion penetrated deeper into the canopy than unidirectional currents, enhancing fluid exchange. Both shoot density and the relative magnitude of wave- versus current-driven flow conditions were found to be important controls on turbulent exchange of water masses across the canopy-water interface.

  13. Seagrass meadows as a globally significant carbonate reservoir

    NASA Astrophysics Data System (ADS)

    Mazarrasa, I.; Marbà, N.; Lovelock, C. E.; Serrano, O.; Lavery, P. S.; Fourqurean, J. W.; Kennedy, H.; Mateo, M. A.; Krause-Jensen, D.; Steven, A. D. L.; Duarte, C. M.

    2015-03-01

    There has been a growing interest in quantifying the capacity of seagrass ecosystems to act as carbon sinks as a natural way of offsetting anthropogenic carbon emissions to the atmosphere. However, most of the efforts have focused on the organic carbon (POC) stocks and accumulation rates and ignored the inorganic carbon (PIC) fraction, despite important carbonate pools associated with calcifying organisms inhabiting the meadows, such as epiphytes and benthic invertebrates, and despite the relevance that carbonate precipitation and dissolution processes have in the global carbon cycle. This study offers the first assessment of the global PIC stocks in seagrass sediments using a synthesis of published and unpublished data on sediment carbonate concentration from 402 vegetated and 34 adjacent un-vegetated sites. PIC stocks in the top 1 m sediments ranged between 3 and 1660 Mg PIC ha-1, with an average of 654 ± 24 Mg PIC ha-1, exceeding about 5 fold those of POC reported in previous studies. Sedimentary carbonate stocks varied across seagrass communities, with meadows dominated by Halodule, Thalassia or Cymodocea supporting the highest PIC stocks, and tended to decrease polewards at a rate of -8 ± 2 Mg PIC ha-1 degree-1 of latitude (GLM, p < 0.0003). Using PIC concentration and estimates of sediment accretion in seagrass meadows, mean PIC accumulation rates in seagrass sediments is 126.3 ± 0.7 g PIC m-2 y-1. Based on the global extent of seagrass meadows (177 000 to 600 000 km2), these ecosystems globally store between 11 and 39 Pg of PIC in the top meter of sediment and accumulate between 22 and 76 Tg PIC y-1, representing a significant contribution to the carbonate dynamics of coastal areas. Despite that these high rates of carbonate accumulation imply CO2 emissions from precipitation, seagrass meadows are still strong CO2 sinks as demonstrates the comparison of carbon (POC and POC) stocks between vegetated and adjacent un-vegetated sediments.

  14. Specificity in Mesograzer-Induced Defences in Seagrasses

    PubMed Central

    Martínez-Crego, Begoña; Arteaga, Pedro; Ueber, Alexandra; Engelen, Aschwin H.; Santos, Rui; Molis, Markus

    2015-01-01

    Grazing-induced plant defences that reduce palatability to herbivores are widespread in terrestrial plants and seaweeds, but they have not yet been reported in seagrasses. We investigated the ability of two seagrass species to induce defences in response to direct grazing by three associated mesograzers. Specifically, we conducted feeding-assayed induction experiments to examine how mesograzer-specific grazing impact affects seagrass induction of defences within the context of the optimal defence theory. We found that the amphipod Gammarus insensibilis and the isopod Idotea chelipes exerted a low-intensity grazing on older blades of the seagrass Cymodocea nodosa, which reflects a weak grazing impact that may explain the lack of inducible defences. The isopod Synischia hectica exerted the strongest grazing impact on C. nodosa via high-intensity feeding on young blades with a higher fitness value. This isopod grazing induced defences in C. nodosa as indicated by a consistently lower consumption of blades previously grazed for 5, 12 and 16 days. The lower consumption was maintained when offered tissues with no plant structure (agar-reconstituted food), but showing a reduced size of the previous grazing effect. This indicates that structural traits act in combination with chemical traits to reduce seagrass palatability to the isopod. Increase in total phenolics but not in C:N ratio and total nitrogen of grazed C. nodosa suggests chemical defences rather than a modified nutritional quality as primarily induced chemical traits. We detected no induction of defences in Zostera noltei, which showed the ability to replace moderate losses of young biomass to mesograzers via compensatory growth. Our study provides the first experimental evidence of induction of defences against meso-herbivory that reduce further consumption in seagrasses. It also emphasizes the relevance of grazer identity in determining the level of grazing impact triggering resistance and compensatory

  15. Seagrass species distribution, density and coverage at Panggang Island, Jakarta

    NASA Astrophysics Data System (ADS)

    Wahab, Iswandi; Madduppa, Hawis; Kawaroe, Mujizat

    2017-01-01

    This study aimed to assess species distribution, density and coverage of seagrass in Panggang Island, within Kepulauan Seribu Marine National Park, northern Jakarta. Seagrass sampling was conducted between March to April 2016 at three observation stations in the West, East, and South of Panggang Island. A total of 6 seagrass species was recorded during sampling period, including Cymodocea rotundata, C. serulata, Halodule uninervis, Syiringodium isoetifolium, Enhalus acoroides, and Thalassia hempricii. All species were observed in the South station, while in the West and East station found only three species (C. rotundata, E. acoroides, and T. hemprichii). While, C. rotundata and T. hemprichii were observed at all station. The highest density was observed for C. rotundata (520 ind/m2) and for T. hempricii (619 ind/m2) in the West station and South Station, respectively. The lowest density was observed in South Station for C. serulata (18 ind/m2), Halodule uninervis (20 ind/m2), and Syiringodium isoetifolium (15 ind/m2). Seagrass coverage of Thalassia hempricii was the highest (43.60%) and the lowest observed at Syiringodium isoetifolium (0.40%). This could be basic information for the management of seagrass ecosystem in the Kepulauan Seribu Marine National Park.

  16. Impact of mooring activities on carbon stocks in seagrass meadows

    NASA Astrophysics Data System (ADS)

    Serrano, O.; Ruhon, R.; Lavery, P. S.; Kendrick, G. A.; Hickey, S.; Masqué, P.; Arias-Ortiz, A.; Steven, A.; Duarte, C. M.

    2016-03-01

    Boating activities are one of the causes that threaten seagrass meadows and the ecosystem services they provide. Mechanical destruction of seagrass habitats may also trigger the erosion of sedimentary organic carbon (Corg) stocks, which may contribute to increasing atmospheric CO2. This study presents the first estimates of loss of Corg stocks in seagrass meadows due to mooring activities in Rottnest Island, Western Australia. Sediment cores were sampled from seagrass meadows and from bare but previously vegetated sediments underneath moorings. The Corg stores have been compromised by the mooring deployment from 1930s onwards, which involved both the erosion of existing sedimentary Corg stores and the lack of further accumulation of Corg. On average, undisturbed meadows had accumulated ~6.4 Kg Corg m-2 in the upper 50 cm-thick deposits at a rate of 34 g Corg m-2 yr-1. The comparison of Corg stores between meadows and mooring scars allows us to estimate a loss of 4.8 kg Corg m-2 in the 50 cm-thick deposits accumulated over ca. 200 yr as a result of mooring deployments. These results provide key data for the implementation of Corg storage credit offset policies to avoid the conversion of seagrass ecosystems and contribute to their preservation.

  17. Impact of mooring activities on carbon stocks in seagrass meadows

    PubMed Central

    Serrano, O.; Ruhon, R.; Lavery, P. S.; Kendrick, G. A.; Hickey, S.; Masqué, P.; Arias-Ortiz, A.; Steven, A.; Duarte, C. M.

    2016-01-01

    Boating activities are one of the causes that threaten seagrass meadows and the ecosystem services they provide. Mechanical destruction of seagrass habitats may also trigger the erosion of sedimentary organic carbon (Corg) stocks, which may contribute to increasing atmospheric CO2. This study presents the first estimates of loss of Corg stocks in seagrass meadows due to mooring activities in Rottnest Island, Western Australia. Sediment cores were sampled from seagrass meadows and from bare but previously vegetated sediments underneath moorings. The Corg stores have been compromised by the mooring deployment from 1930s onwards, which involved both the erosion of existing sedimentary Corg stores and the lack of further accumulation of Corg. On average, undisturbed meadows had accumulated ~6.4 Kg Corg m−2 in the upper 50 cm-thick deposits at a rate of 34 g Corg m−2 yr−1. The comparison of Corg stores between meadows and mooring scars allows us to estimate a loss of 4.8 kg Corg m−2 in the 50 cm-thick deposits accumulated over ca. 200 yr as a result of mooring deployments. These results provide key data for the implementation of Corg storage credit offset policies to avoid the conversion of seagrass ecosystems and contribute to their preservation. PMID:26979407

  18. Seagrass as the main food source of Neaxius acanthus (Thalassinidea: Strahlaxiidae), its burrow associates, and of Corallianassa coutierei (Thalassinidea: Callianassidae)

    NASA Astrophysics Data System (ADS)

    Kneer, Dominik; Asmus, Harald; Vonk, Jan Arie

    2008-09-01

    Burrows of the thalassinidean shrimps Neaxius acanthus and Corallianassa coutierei are striking aspects in tropical seagrass beds of the Spermonde Archipelago, Indonesia. Burrow construction, behaviour, burrow type and associated commensal community were investigated to clarify the ecological role and food requirements of these shrimps and their commensals. Gut content analysis and stable-isotope data were used to unravel the food sources and the trophic interactions among the commensal community. Individuals of Neaxius acanthus were caught on Bone Batang Island. In narrow aquaria filled with sediment they constructed burrows resembling those found in the field. During burrow construction and maintenance only little sediment was brought to the surface, most was sorted and compacted to create a distinct lining. Maintenance work by single shrimps typically took about 5 min, after which the shrimp walked up to the entrance and rested for a similar period of time. There were no differences in behaviour between day and night. Intrasexual encounters inside the burrow were characterised by a high level of aggression and all resulted in one participant being driven out of the burrow. Intersexual encounters led to coexistence with both animals taking turns in burrow maintenance and guarding the entrance. Offered seagrass leaves were pulled underground, cut into pieces and eventually integrated into the lining. Burrows of Corallianassa coutierei resembled a deep U-shape. Chambers branching off halfway down and at the deepest point contained seagrass fragments. All steep parts of the burrow were lined similar to burrows of N. acanthus. No commensals were found associated with Corallianassa coutierei. However, burrows of Neaxius acanthus in the field typically contained a pair of shrimps, up to 8 individuals of the commensal bivalve Barrimysia cumingii and large numbers of gammarid amphipods. Other animals found associated with the burrow were the goby Austrolethops wardi, a

  19. Relationships between multibeam backscatter, sediment grain size and Posidonia oceanica seagrass distribution

    NASA Astrophysics Data System (ADS)

    De Falco, Giovanni; Tonielli, Renato; Di Martino, Gabriella; Innangi, Sara; Simeone, Simone; Michael Parnum, Iain

    2010-10-01

    The use of data, including bathymetry, backscatter intensity and the angular response of backscatter intensity, collected using multibeam sonar (MBS) systems to recognise seabed types was evaluated in the inner shelf of central western Sardinia (western Mediterranean sea), a site characterised by a complex seabed including sandy and gravelly sediments, Posidonia oceanica seagrass beds growing on hardgrounds (i.e. biogenic carbonates) and sedimentary substrates. A MBS survey was carried out in order to collect bathymetric and acoustic backscatter data. Ground-truth data in the form of grab samples and diver observations were collected at 57 stations, 41 of which were in non-vegetated sedimentary substrate and 16 of which were in P. oceanica beds. Sediment samples were analysed for grain size. Statistical comparison between MBS backscatter and grain size data showed that backscatter intensity is strongly affected by sediment grain size, being directly correlated to the weight percent of the coarse fraction (1-16 mm) and inversely correlated to weight percent of the finer sediments (0.016-0.5 mm). Factor analysis of grain size and acoustic data identified three sedimentary facies: sandy gravels (SG), gravelly sands (GS) and slightly gravelly muddy sands (SGMS). Each facies showed different acoustic responses in terms of backscatter intensity and shape of the angular response curves. Differences in backscatter intensity among five seabed types, including the three sediment types identified by factor analysis and P. oceanica beds, growing on hardgrounds and sedimentary substrates, were tested by analysis of variance. P. oceanica on hardgrounds, P. oceanica on sedimentary substrates and GS exhibited values of relative backscatter intensity within the same range and, consequently, it was not possible to distinguish Posidonia beds and gravelly sands only on the basis of backscatter data. The similarity of backscatter intensity from P. oceanica growing on different

  20. The dominance of dispersion in the evolution of bed material waves in gravel-bed rivers

    Treesearch

    Thomas E. Lisle; Yantao Cui; Gary Parker; James E. Pizzuto; Annjanette M. Dodd

    2001-01-01

    Abstract - Bed material waves are temporary zones of sediment accumulation created by large sediment inputs. Recent theoretical, experimental and field studies examine factors in fluencing dispersion and translation of bed material waves in quasi-uniform, gravel-bed channels. Exchanges of sediment between a channel and its floodplain are...

  1. Photorespiration and carbon limitation determine productivity in temperate seagrasses.

    PubMed

    Buapet, Pimchanok; Rasmusson, Lina M; Gullström, Martin; Björk, Mats

    2013-01-01

    The gross primary productivity of two seagrasses, Zostera marina and Ruppia maritima, and one green macroalga, Ulva intestinalis, was assessed in laboratory and field experiments to determine whether the photorespiratory pathway operates at a substantial level in these macrophytes and to what extent it is enhanced by naturally occurring shifts in dissolved inorganic carbon (DIC) and O2 in dense vegetation. To achieve these conditions in laboratory experiments, seawater was incubated with U. intestinalis in light to obtain a range of higher pH and O2 levels and lower DIC levels. Gross photosynthetic O2 evolution was then measured in this pretreated seawater (pH, 7.8-9.8; high to low DIC:O2 ratio) at both natural and low O2 concentrations (adjusted by N2 bubbling). The presence of photorespiration was indicated by a lower gross O2 evolution rate under natural O2 conditions than when O2 was reduced. In all three macrophytes, gross photosynthetic rates were negatively affected by higher pH and lower DIC. However, while both seagrasses exhibited significant photorespiratory activity at increasing pH values, the macroalga U. intestinalis exhibited no such activity. Rates of seagrass photosynthesis were then assessed in seawater collected from the natural habitats (i.e., shallow bays characterized by high macrophyte cover and by low DIC and high pH during daytime) and compared with open baymouth water conditions (where seawater DIC is in equilibrium with air, normal DIC, and pH). The gross photosynthetic rates of both seagrasses were significantly higher when incubated in the baymouth water, indicating that these grasses can be significantly carbon limited in shallow bays. Photorespiration was also detected in both seagrasses under shallow bay water conditions. Our findings indicate that natural carbon limitations caused by high community photosynthesis can enhance photorespiration and cause a significant decline in seagrass primary production in shallow waters.

  2. Resource distribution influences positive edge effects in a seagrass fish.

    PubMed

    Macreadie, Peter I; Hindell, Jeremy S; Keough, Michael J; Jenkins, Gregory P; Connolly, Rod M

    2010-07-01

    According to conceptual models, the distribution of resources plays a critical role in determining how organisms distribute themselves near habitat edges. These models are frequently used to achieve a mechanistic understanding of edge effects, but because they are based predominantly on correlative studies, there is need for a demonstration of causality, which is best done through experimentation. Using artificial seagrass habitat as an experimental system, we determined a likely mechanism underpinning edge effects in a seagrass fish. To test for edge effects, we measured fish abundance at edges (0-0.5 m) and interiors (0.5-1 m) of two patch configurations: continuous (single, continuous 9-m2 patches) and patchy (four discrete 1-m2 patches within a 9-m2 area). In continuous configurations, pipefish (Stigmatopora argus) were three times more abundant at edges than interiors (positive edge effect), but in patchy configurations there was no difference. The lack of edge effect in patchy configurations might be because patchy seagrass consisted entirely of edge habitat. We then used two approaches to test whether observed edge effects in continuous configurations were caused by increased availability of food at edges. First, we estimated the abundance of the major prey of pipefish, small crustaceans, across continuous seagrass configurations. Crustacean abundances were highest at seagrass edges, where they were 16% greater than in patch interiors. Second, we supplemented interiors of continuous treatment patches with live crustaceans, while control patches were supplemented with seawater. After five hours of supplementation, numbers of pipefish were similar between edges and interiors of treatment patches, while the strong edge effects were maintained in controls. This indicated that fish were moving from patch edges to interiors in response to food supplementation. These approaches strongly suggest that a numerically dominant fish species is more abundant at seagrass

  3. Landscape configuration modulates carbon storage in seagrass sediments

    NASA Astrophysics Data System (ADS)

    Ricart, Aurora M.; Pérez, Marta; Romero, Javier

    2017-02-01

    Climate change has increased interest in seagrass systems as natural carbon sinks and recent studies have estimated the carbon stocks associated with seagrass meadows. However, the factors that affect their variability remain poorly understood. This paper assesses how landscape-level attributes (patch size and matrix composition) influence carbon storage in seagrass sediments. We quantified the organic carbon (Corg) content and other geochemical properties (δ13C and particle size) in surface sediments of continuous Posidonia oceanica meadows, patchy meadows interspersed with rocky-algal reefs and patchy meadows on sedimentary bottoms. We also took samples of potential carbon sources for isotopic composition determination. Our results indicate that the continuous meadows accumulated larger amounts of Corg than patchy meadows, whether embedded in a rock or sand matrix. The Corg from continuous meadows was also more 13C enriched, which suggests that a high proportion of the carbon was derived from plant material (autochthonous sources); in contrast in patchy meadows (especially in a sand matrix), lower δ13C values indicated a higher contribution from allochthonous sources (mainly suspended particulate organic matter, SPOM). These findings suggest that the sediment of continuous meadows stores more Corg in than that of patchy meadows. This is probably due to the increased contribution from seagrass leaves, which are much more refractory than SPOM. In general, certain landscape configurations, and especially patchiness, appear to reduce the carbon storage capacity of seagrasses. Since the current decline of seagrass is leading to habitat fragmentation, our results increase the argument for the promotion of effective measures to preserve the integrity of these natural carbon sinks.

  4. Quantifying and modelling the carbon sequestration capacity of seagrass meadows--a critical assessment.

    PubMed

    Macreadie, P I; Baird, M E; Trevathan-Tackett, S M; Larkum, A W D; Ralph, P J

    2014-06-30

    Seagrasses are among the planet's most effective natural ecosystems for sequestering (capturing and storing) carbon (C); but if degraded, they could leak stored C into the atmosphere and accelerate global warming. Quantifying and modelling the C sequestration capacity is therefore critical for successfully managing seagrass ecosystems to maintain their substantial abatement potential. At present, there is no mechanism to support carbon financing linked to seagrass. For seagrasses to be recognised by the IPCC and the voluntary C market, standard stock assessment methodologies and inventories of seagrass C stocks are required. Developing accurate C budgets for seagrass meadows is indeed complex; we discuss these complexities, and, in addition, we review techniques and methodologies that will aid development of C budgets. We also consider a simple process-based data assimilation model for predicting how seagrasses will respond to future change, accompanied by a practical list of research priorities. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. The influence of wave energy and sediment transport on seagrass distribution

    USGS Publications Warehouse

    Stevens, Andrew W.; Lacy, Jessica R.

    2012-01-01

    A coupled hydrodynamic and sediment transport model (Delft3D) was used to simulate the water levels, waves, and currents associated with a seagrass (Zostera marina) landscape along a 4-km stretch of coast in Puget Sound, WA, USA. A hydroacoustic survey of seagrass percent cover and nearshore bathymetry was conducted, and sediment grain size was sampled at 53 locations. Wave energy is a primary factor controlling seagrass distribution at the site, accounting for 73% of the variability in seagrass minimum depth and 86% of the variability in percent cover along the shallow, sandy portions of the coast. A combination of numerical simulations and a conceptual model of the effect of sea-level rise on the cross-shore distribution of seagrass indicates that the area of seagrass habitat may initially increase and that wave dynamics are an important factor to consider in predicting the effect of sea-level rise on seagrass distributions in wave-exposed areas.

  6. Dugong dugon feeding in tropical Australian seagrass meadows: implications for conservation planning

    PubMed Central

    Coles, Rob G.; Congdon, Bradley C.

    2016-01-01

    Dugongs (Dugong dugon) are listed as vulnerable to extinction due to rapid population reductions caused in part by loss of seagrass feeding meadows. Understanding dugong feeding behaviour in tropical Australia, where the majority of dugongs live, will assist conservation strategies. We examined whether feeding patterns in intertidal seagrass meadows in tropical north-eastern Australia were related to seagrass biomass, species composition and/or nitrogen content. The total biomass of each seagrass species removed by feeding dugongs was measured and compared to its relative availability. Nitrogen concentrations were also determined for each seagrass species present at the sites. Dugongs consumed seagrass species in proportion to their availability, with biomass being the primary determining factor. Species composition and/or nitrogen content influenced consumption to a lesser degree. Conservation plans focused on protecting high biomass intertidal seagrass meadows are likely to be most effective at ensuring the survival of dugong in tropical north-eastern Australia. PMID:27441123

  7. Dugong dugon feeding in tropical Australian seagrass meadows: implications for conservation planning.

    PubMed

    Tol, Samantha J; Coles, Rob G; Congdon, Bradley C

    2016-01-01

    Dugongs (Dugong dugon) are listed as vulnerable to extinction due to rapid population reductions caused in part by loss of seagrass feeding meadows. Understanding dugong feeding behaviour in tropical Australia, where the majority of dugongs live, will assist conservation strategies. We examined whether feeding patterns in intertidal seagrass meadows in tropical north-eastern Australia were related to seagrass biomass, species composition and/or nitrogen content. The total biomass of each seagrass species removed by feeding dugongs was measured and compared to its relative availability. Nitrogen concentrations were also determined for each seagrass species present at the sites. Dugongs consumed seagrass species in proportion to their availability, with biomass being the primary determining factor. Species composition and/or nitrogen content influenced consumption to a lesser degree. Conservation plans focused on protecting high biomass intertidal seagrass meadows are likely to be most effective at ensuring the survival of dugong in tropical north-eastern Australia.

  8. Ontogenetic habitat use by mangrove/seagrass-associated coral reef fishes shows flexibility in time and space

    NASA Astrophysics Data System (ADS)

    Kimirei, Ismael A.; Nagelkerken, Ivan; Griffioen, Ben; Wagner, Coen; Mgaya, Yunus D.

    2011-03-01

    Tropical shallow-water habitats such as mangroves and seagrass beds are widely acknowledged as important juvenile habitats for various coral reef fish species, most of which are commercially important to fisheries. Spatio-temporal variability in ontogenetic habitat use by fish among these tropical coastal ecosystems has rarely been investigated, yet there are sufficient reasons to believe that this plays an important role. In the present study, we test the spatio-temporal variability in patterns of ontogenetic habitat use by some mangrove/seagrass-associated coral reef fishes ( Lethrinus harak, Lethrinus lentjan, Lutjanus fulviflamma and Siganus sutor). Abundances of these four species were investigated during two years in Tanzanian coastal waters, using underwater visual census in mangrove, seagrass, shallow and deep mudflat, and shallow and deep coral reef habitats. The study covered four distinct seasons of the year and was done at two spatially separated (>40 km) locations. Averaged across locations, seasons and years, juveniles (≤10 cm length) of the four study species had significantly higher relative densities in shallow-water (mangroves and seagrass beds) than in deep-water habitats (deep mudflats or coral reefs), whereas the opposite pattern was found for the adults (>15 cm). These findings suggest a strong and general pattern of ontogenetic habitat shifts from shallow- to deep-water habitats. However, specific habitat-use patterns of juveniles as well as adults differed significantly in time and space. Various species showed subtle to considerable flexibility in juvenile as well as adult habitat use across seasons, years, or at different locations. Furthermore, for some species the data suggest presence of ontogenetic habitat shifts at one location but lack thereof at the other location. In summary, ontogenetic habitat use needs to be considered at various spatial and temporal scales for the interpretation of habitat utilization by fish during different

  9. Low frequency acoustic properties of Posidonia oceanica seagrass leaf blades

    PubMed Central

    Johnson, Jay R.; Venegas, Gabriel R.; Wilson, Preston S.; Hermand, Jean-Pierre

    2017-01-01

    The acoustics of seagrass meadows impacts naval and oceanographic sonar applications. To study this environment, a one-dimensional resonator was used to assess the low-frequency (1–5 kHz) acoustic response of the leaf blades of the Mediterranean seagrass Posidonia oceanica in water. Three separate collections of plants from Crete, Greece, and Sicily, Italy were investigated. A high consistency in effective sound speed was observed within each collection while a strong variability was observed between different collections. Average size, mass, and epiphytic coverage within each collection were quantified, and discoloration and stiffness are discussed qualitatively with respect to the observed acoustic variability. PMID:28618796

  10. Dynamic Compaction of Porous Beds

    DTIC Science & Technology

    1985-12-26

    NSWVC TR 83-246 00 00 SDYNAMIC COMPACTION OF POROUS B3EDS BY H. W. SANDUSKY T. P. LIDDIARD RESEARCH AND TECHNOLOGY DEPARTMENT D I 26 DECEMBER 1985...RIOBA4313 11. TITLE (Include Security Classfication3 Dynamic Compaction of Porous Beds 12. PERSONAL AUTHOR(S) Sandusky, H. W., and Liddiard, T. P. 13a... Porous Bed Compaction Wave Velocity Oeflaaration-to-Detonation Transition Particle Velocity ABSTRACT (Continue on reverse if necessary and identify

  11. Local Knowledge and Conservation of Seagrasses in the Tamil Nadu State of India

    PubMed Central

    2011-01-01

    Local knowledge systems are not considered in the conservation of fragile seagrass marine ecosystems. In fact, little is known about the utility of seagrasses in local coastal communities. This is intriguing given that some local communities rely on seagrasses to sustain their livelihoods and have relocated their villages to areas with a rich diversity and abundance of seagrasses. The purpose of this study is to assist in conservation efforts regarding seagrasses through identifying Traditional Ecological Knowledge (TEK) from local knowledge systems of seagrasses from 40 coastal communities along the eastern coast of India. We explore the assemblage of scientific and local traditional knowledge concerning the 1. classification of seagrasses (comparing scientific and traditional classification systems), 2. utility of seagrasses, 3. Traditional Ecological Knowledge (TEK) of seagrasses, and 4. current conservation efforts for seagrass ecosystems. Our results indicate that local knowledge systems consist of a complex classification of seagrass diversity that considers the role of seagrasses in the marine ecosystem. This fine-scaled ethno-classification gives rise to five times the number of taxa (10 species = 50 local ethnotaxa), each with a unique role in the ecosystem and utility within coastal communities, including the use of seagrasses for medicine (e.g., treatment of heart conditions, seasickness, etc.), food (nutritious seeds), fertilizer (nutrient rich biomass) and livestock feed (goats and sheep). Local communities are concerned about the loss of seagrass diversity and have considerable local knowledge that is valuable for conservation and restoration plans. This study serves as a case study example of the depth and breadth of local knowledge systems for a particular ecosystem that is in peril. Key words: local health and nutrition, traditional ecological knowledge (TEK), conservation and natural resources management, consensus, ethnomedicine, ethnotaxa

  12. Local knowledge and conservation of seagrasses in the Tamil Nadu state of India.

    PubMed

    Newmaster, A F; Berg, K J; Ragupathy, S; Palanisamy, M; Sambandan, K; Newmaster, S G

    2011-11-23

    Local knowledge systems are not considered in the conservation of fragile seagrass marine ecosystems. In fact, little is known about the utility of seagrasses in local coastal communities. This is intriguing given that some local communities rely on seagrasses to sustain their livelihoods and have relocated their villages to areas with a rich diversity and abundance of seagrasses. The purpose of this study is to assist in conservation efforts regarding seagrasses through identifying Traditional Ecological Knowledge (TEK) from local knowledge systems of seagrasses from 40 coastal communities along the eastern coast of India. We explore the assemblage of scientific and local traditional knowledge concerning the 1. classification of seagrasses (comparing scientific and traditional classification systems), 2. utility of seagrasses, 3. Traditional Ecological Knowledge (TEK) of seagrasses, and 4. current conservation efforts for seagrass ecosystems. Our results indicate that local knowledge systems consist of a complex classification of seagrass diversity that considers the role of seagrasses in the marine ecosystem. This fine-scaled ethno-classification gives rise to five times the number of taxa (10 species = 50 local ethnotaxa), each with a unique role in the ecosystem and utility within coastal communities, including the use of seagrasses for medicine (e.g., treatment of heart conditions, seasickness, etc.), food (nutritious seeds), fertilizer (nutrient rich biomass) and livestock feed (goats and sheep). Local communities are concerned about the loss of seagrass diversity and have considerable local knowledge that is valuable for conservation and restoration plans. This study serves as a case study example of the depth and breadth of local knowledge systems for a particular ecosystem that is in peril.

  13. Introduction to Bed Bugs

    MedlinePlus

    ... preventing infestations, increased resistance of bed bugs to pesticides, and ineffective pest control practices. The good news ... Bed Bugs — Do-it-yourself Bed Bug Control — Pesticides to Control Bed Bugs Bed Bug Information Clearinghouse ...

  14. Assessing gear modifications needed to optimize yields in a heavily exploited, multi-species, seagrass and coral reef fishery.

    PubMed

    Hicks, Christina C; McClanahan, Timothy R

    2012-01-01

    Effective management is necessary if small-scale fisheries, such as those found in mixed habitats including seagrass and coral reefs, are to continue providing food for many of the poorest communities of the world. Gear-based management, although under represented and under studied, has the potential to be adaptive, address multiple objectives, and be crafted to the socio-economic setting. Management effectiveness in seagrass and coral reef fisheries has generally been evaluated at the scale of the fish community. However, community level indicators can mask species-specific declines that provide significant portions of the fisheries yields and income. Using a unique dataset, containing ten years of species level length frequency catch data from a multi-gear, multi-species seagrass and coral reef fishery in Kenya, we evaluate species specific fishery statuses, compare gear use to gear regulations and estimate the potential needs for further gear restrictions. Despite the high diversity of the fishery, fifteen species represented over 90% of the catch, and only three species represented 60% of the catch. The three most abundant species in the catch, Lethrinus lentjan (Lacepède), Siganus sutor (Valenciennes) and Leptoscarus vaigiensis (Quoy & Gaimard) all showed evidence of growth overfishing. Lethrinus lentjan, with an exploitation rate of 0.82, also shows evidence of recruitment overfishing. Current legal but weakly enforced gear restrictions are capable of protecting a significant portion of the catch up to maturity but optimization of yield will require that the current mesh size be increased from 6.3 to 8.8 and 9.2 cm to increase yields of L. lentjan and S. sutor, respectively. Given the difficulties of enforcing mesh size, we recommend that the economic benefits of these larger mesh sizes be communicated and enforced through co-management. This abstract is also available in Kiswahili (Abstract S1).

  15. Assessing Gear Modifications Needed to Optimize Yields in a Heavily Exploited, Multi-Species, Seagrass and Coral Reef Fishery

    PubMed Central

    Hicks, Christina C.; McClanahan, Timothy R.

    2012-01-01

    Effective management is necessary if small-scale fisheries, such as those found in mixed habitats including seagrass and coral reefs, are to continue providing food for many of the poorest communities of the world. Gear-based management, although under represented and under studied, has the potential to be adaptive, address multiple objectives, and be crafted to the socio-economic setting. Management effectiveness in seagrass and coral reef fisheries has generally been evaluated at the scale of the fish community. However, community level indicators can mask species-specific declines that provide significant portions of the fisheries yields and income. Using a unique dataset, containing ten years of species level length frequency catch data from a multi-gear, multi-species seagrass and coral reef fishery in Kenya, we evaluate species specific fishery statuses, compare gear use to gear regulations and estimate the potential needs for further gear restrictions. Despite the high diversity of the fishery, fifteen species represented over 90% of the catch, and only three species represented 60% of the catch. The three most abundant species in the catch, Lethrinus lentjan (Lacepède), Siganus sutor (Valenciennes) and Leptoscarus vaigiensis (Quoy & Gaimard) all showed evidence of growth overfishing. Lethrinus lentjan, with an exploitation rate of 0.82, also shows evidence of recruitment overfishing. Current legal but weakly enforced gear restrictions are capable of protecting a significant portion of the catch up to maturity but optimization of yield will require that the current mesh size be increased from 6.3 to 8.8 and 9.2 cm to increase yields of L. lentjan and S. sutor, respectively. Given the difficulties of enforcing mesh size, we recommend that the economic benefits of these larger mesh sizes be communicated and enforced through co-management. This abstract is also available in Kiswahili (Abstract S1). PMID:22574133

  16. Seagrass biofilm communities at a naturally CO2 -rich vent.

    PubMed

    Hassenrück, Christiane; Hofmann, Laurie C; Bischof, Kai; Ramette, Alban

    2015-06-01

    Seagrass meadows are a crucial component of tropical marine reef ecosystems. Seagrass plants are colonized by a multitude of epiphytic organisms that contribute to broadening the ecological role of seagrasses. To better understand how environmental changes like ocean acidification might affect epiphytic assemblages, the microbial community composition of the epiphytic biofilm of Enhalus acroides was investigated at a natural CO2 vent in Papua New Guinea using molecular fingerprinting and next-generation sequencing of 16S and 18S rRNA genes. Both bacterial and eukaryotic epiphytes formed distinct communities at the CO2 -impacted site compared with the control site. This site-related CO2 effect was also visible in the succession pattern of microbial epiphytes. We further found an increased relative sequence abundance of bacterial types associated with coral diseases at the CO2 -impacted site (Fusobacteria, Thalassomonas), whereas eukaryotes such as certain crustose coralline algae commonly related to healthy reefs were less diverse. These trends in the epiphytic community of E. acroides suggest a potential role of seagrasses as vectors of coral pathogens and may support previous predictions of a decrease in reef health and prevalence of diseases under future ocean acidification scenarios. © 2015 The Authors. Environmental Microbiology Reports published by Society for Applied Microbiology and John Wiley & Sons Ltd.

  17. CONTROLS OF SEAGRASS EPIPHYTE ABUNDANCE: DOES LIGHT TRUMP NUTRIENTS?

    EPA Science Inventory

    Epiphytes on seagrass growing in the lower intertidal were examined along an estuarine gradient within Yaquina Bay, Oregon over a period of 4 years. The Yaquina Estuary receives high levels of nutrients from the watershed during the wet season and from the ocean during the dry s...

  18. CONTROLS OF SEAGRASS EPIPHYTE ABUNDANCE: DOES LIGHT TRUMP NUTRIENTS?

    EPA Science Inventory

    Epiphytes on seagrass growing in the lower intertidal were examined along an estuarine gradient within Yaquina Bay, Oregon over a period of 4 years. The Yaquina Estuary receives high levels of nutrients from the watershed during the wet season and from the ocean during the dry s...

  19. Seagrass Ecosystem Services and Their Variability across Genera and Geographical Regions

    PubMed Central

    Mtwana Nordlund, Lina; Barbier, Edward B.; Creed, Joel C.

    2016-01-01

    Threats to and loss of seagrass ecosystems globally, impact not only natural resources but also the lives of people who directly or indirectly depend on these systems. Seagrass ecosystems play a multi-functional role in human well-being, e.g. food through fisheries, control of erosion and protection against floods. Quantifying these services reveals their contributions to human well-being and helps justify seagrass conservation. There has been no comprehensive assessment as to whether seagrass ecosystem services are perceived to vary over the globe or amongst genera. Our study compiles the most complete list of ecosystem services provided by seagrasses so far, including bioregional- and genus-specific information from expert opinion and published studies. Several seagrass ecosystem services vary considerably in their (known) provision across genera and over the globe. Seagrasses genera are clearly not all equal with regard to the ecosystem services they provide. As seagrass genera are not evenly distributed over all bioregions, the presence of an ecosystem service sometimes depends on the genera present. Larger sized seagrass genera (e.g. Posidonia, Enhalus) are perceived to provide more substantial and a wider variety of ecosystem services than smaller species (e.g. Halophila, Lepilaena). Nevertheless, smaller species provide important services. Our findings point out data gaps, provide new insight for more efficient management and recommend caution in economic valuation of seagrass services worldwide. PMID:27732600

  20. Long distance biotic dispersal of tropical seagrass seeds by marine mega-herbivores.

    PubMed

    Tol, Samantha J; Jarvis, Jessie C; York, Paul H; Grech, Alana; Congdon, Bradley C; Coles, Robert G

    2017-06-30

    Terrestrial plants use an array of animals as vectors for dispersal, however little is known of biotic dispersal of marine angiosperms such as seagrasses. Our study in the Great Barrier Reef confirms for the first time that dugongs (Dugong dugon) and green sea turtles (Chelonia mydas) assist seagrass dispersal. We demonstrate that these marine mega-herbivores consume and pass in faecal matter viable seeds for at least three seagrass species (Zostera muelleri, Halodule uninervis and Halophila decipiens). One to two seagrass seeds per g DW of faecal matter were found during the peak of the seagrass reproductive season (September to December), with viability on excretion of 9.13% ± 4.61% (SE). Using population estimates for these mega-herbivores, and data on digestion time (hrs), average daily movement (km h) and numbers of viable seagrass seeds excreted (per g DW), we calculated potential seagrass seed dispersal distances. Dugongs and green sea turtle populations within this region can disperse >500,000 viable seagrass seeds daily, with a maximum dispersal distance of approximately 650 km. Biotic dispersal of tropical seagrass seeds by dugongs and green sea turtles provides a large-scale mechanism that enhances connectivity among seagrass meadows, and aids in resilience and recovery of these coastal habitats.

  1. Heavy metal enrichment in the seagrasses of Lakshadweep group of islands--a multivariate statistical analysis.

    PubMed

    Thangaradjou, T; Raja, S; Subhashini, Pon; Nobi, E P; Dilipan, E

    2013-01-01

    An assessment on heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) accumulation by seven seagrass species of Lakshadweep group of islands was carried out using multivariate statistical tools like principal component analysis (PCA) and cluster analysis (CA). Among all the metals, Mg and Al were determined in higher concentration in all the seagrasses, and their values varied with respect to different seagrass species. The concentration of the four toxic heavy metals (Cd, Pb, Zn and Cu) was found higher in all the seagrasses when compared with the background values of seagrasses from Flores Sea, Indonesia. The contamination factor of these four heavy metals ranged as Cd (1.97-12.5), Cu (0.73-4.40), Pb (2.3-8.89) and Zn (1.27-2.787). In general, the Pollution Load Index (PLI) calculated was found to be maximum for Halophila decipiens (58.2). Results revealed that Halophila decipiens is a strong accumulator of heavy metals, followed by Halodule uninervis and Halodule pinifolia, among all the tested seagrasses. Interestingly, the small-leaved seagrasses were found to be efficient in heavy metal accumulation than the large-leaved seagrass species. Thus, seagrasses can better be used for biomonitoring, and seagrasses can be used as the heavy metal sink as the biomass take usually long term to get remineralize in nature.

  2. A comparison of the impact of 'seagrass-friendly' boat mooring systems on Posidonia australis.

    PubMed

    Demers, Marie-Claire A; Davis, Andrew R; Knott, Nathan A

    2013-02-01

    Permanent boat moorings have contributed to the decline of seagrasses worldwide, prompting the development of 'seagrass-friendly' moorings. We contrasted seagrass cover and density (predominantly Posidonia australis) in the vicinity of three mooring types and nearby reference areas lacking moorings in Jervis Bay, Australia. We examined two types of 'seagrass-friendly' mooring and a conventional 'swing' mooring. 'Swing' moorings produced significant seagrass scour, denuding patches of ~9 m radius. Seagrass-friendly 'cyclone' moorings produced extensive denuded patches (average radius of ~18 m). Seagrass-friendly 'screw' moorings, conversely, had similar seagrass cover to nearby reference areas. Our findings reinforce previous work highlighting the negative effects of 'swing' and 'cyclone' moorings. In contrast, the previously unstudied 'screw' moorings were highly effective. We conclude that regular maintenance of moorings and the monitoring of surrounding seagrass are required to ensure that 'seagrass-friendly' moorings are operating effectively. This is important, as following damage Posidonia will take many decades to recover. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Meadow fragmentation and reproductive output of the SE Asian seagrass Enhalus acoroides [rapid communication

    NASA Astrophysics Data System (ADS)

    Vermaat, Jan E.; Rollon, Rene N.; Lacap, Cristina Day A.; Billot, Claire; Alberto, Filipe; Nacorda, Hildie M. E.; Wiegman, Frank; Terrados, Jorge

    2004-11-01

    Flower and fruit production of the abundant, tall, long-lived, dioecious, surface-pollinating seagrass species Enhalus acoroides (L.) Royle were estimated at seven sites in the reef flats off Bolinao (NW Luzon, The Philippines) featuring different fragmentation of the seagrass meadows. Fragmentation of the seagrass meadow was quantified as cover of E. acoroides and all seagrass species present in 20×20 m plots. E. acoroides and overall seagrass cover were correlated positively. The proportion of female flowers of E. acoroides that developed a fruit increased sharply as overall seagrass cover was around 50%. Apparent sex ratio bore no relationship with overall seagrass cover. This threshold-type of relationship suggests that fragmentation of seagrass meadows can have a major effect on the reproductive output of this species. A possible mechanism underlying these results would be a non-linear increase of the efficiency of trapping the surface-dispersed pollen with increasing seagrass canopy density. This provides the first evidence based on real data that fragmentation can affect the population dynamics of seagrass species.

  4. Seagrass Ecosystem Services and Their Variability across Genera and Geographical Regions.

    PubMed

    Mtwana Nordlund, Lina; Koch, Evamaria W; Barbier, Edward B; Creed, Joel C

    2016-01-01

    Threats to and loss of seagrass ecosystems globally, impact not only natural resources but also the lives of people who directly or indirectly depend on these systems. Seagrass ecosystems play a multi-functional role in human well-being, e.g. food through fisheries, control of erosion and protection against floods. Quantifying these services reveals their contributions to human well-being and helps justify seagrass conservation. There has been no comprehensive assessment as to whether seagrass ecosystem services are perceived to vary over the globe or amongst genera. Our study compiles the most complete list of ecosystem services provided by seagrasses so far, including bioregional- and genus-specific information from expert opinion and published studies. Several seagrass ecosystem services vary considerably in their (known) provision across genera and over the globe. Seagrasses genera are clearly not all equal with regard to the ecosystem services they provide. As seagrass genera are not evenly distributed over all bioregions, the presence of an ecosystem service sometimes depends on the genera present. Larger sized seagrass genera (e.g. Posidonia, Enhalus) are perceived to provide more substantial and a wider variety of ecosystem services than smaller species (e.g. Halophila, Lepilaena). Nevertheless, smaller species provide important services. Our findings point out data gaps, provide new insight for more efficient management and recommend caution in economic valuation of seagrass services worldwide.

  5. Major Seagrass Carbon Sinks Worldwide, Shark Bay, Western Australia

    NASA Astrophysics Data System (ADS)

    Arias-Ortiz, A.; Serrano, O.; Masque, P.; Lavery, P.; Duarte, C. M.; Kendrick, G. A.

    2016-02-01

    Seagrasses are marine foundation species that provide valuable ecosystem services including the stabilization of sediment, carbon dioxide sequestration, and habitat for diverse fauna and flora. Shark Bay, Western Australia, registered as a World Heritage Property, has the largest reported assemblage of seagrass meadows worldwide, thus has an important role in producing, sequestering and storing organic carbon (Corg). We surveyed 30 seagrass meadows in Shark Bay accounting for species composition, seagrass contribution to the sedimentary Corg pool, and habitat variability. The sediment accumulation rates (SAR) and Corg accumulation over short and long terms were determined by means of 210Pb and 14C dating. Sediment grain size was used to characterize sedimentary environments and δ13C analyses to determine the sources of sedimentary Corg stocks in each meadow. Corg stocks accumulated in the last century varied from 0.4 to 4.5 kg Corg m-2, with an average burial rate of 24 ± 11 g Corg m-2 y-1 (10 - 20 cm-thick deposits). Stocks in the top meter ranged from 4 to 30 kg Corg m-2, which is equivalent to a long-term carbon burial rate averaging 8 ± 5 g Corg m-2 y-1 (over the last millennia). With an area of 4,000 km2, seagrass meadows in Shark Bay store the vast amount of 45 ± 23 Tg Corg in the top meter, which would represent about 1% of the Corg stored in seagrass meadows worldwide. Spatial and temporal variability in Corg storage results from various factors, including biological (e.g. net primary production), chemical (e.g. recalcitrance of Corg stocks) and geological (e.g. hydrodynamic energy and sediment accumulation rates). Higher SAR and smaller sediment size appeared to contribute to a higher accumulation and preservation of Corg. Moreover, sediments with highest Corg stocks were characterized by high δ13C, suggesting that the plant itself plays a key role in Corg storage. These findings combined with sediment chronologies help us to understand the formation

  6. Seagrass meadows as a globally significant carbonate reservoir

    NASA Astrophysics Data System (ADS)

    Mazarrasa, I.; Marbà, N.; Lovelock, C. E.; Serrano, O.; Lavery, P. S.; Fourqurean, J. W.; Kennedy, H.; Mateo, M. A.; Krause-Jensen, D.; Steven, A. D. L.; Duarte, C. M.

    2015-08-01

    There has been growing interest in quantifying the capacity of seagrass ecosystems to act as carbon sinks as a natural way of offsetting anthropogenic carbon emissions to the atmosphere. However, most of the efforts have focused on the particulate organic carbon (POC) stocks and accumulation rates and ignored the particulate inorganic carbon (PIC) fraction, despite important carbonate pools associated with calcifying organisms inhabiting the meadows, such as epiphytes and benthic invertebrates, and despite the relevance that carbonate precipitation and dissolution processes have in the global carbon cycle. This study offers the first assessment of the global PIC stocks in seagrass sediments using a synthesis of published and unpublished data on sediment carbonate concentration from 403 vegetated and 34 adjacent un-vegetated sites. PIC stocks in the top 1 m of sediment ranged between 3 and 1660 Mg PIC ha-1, with an average of 654 ± 24 Mg PIC ha-1, exceeding those of POC reported in previous studies by about a factor of 5. Sedimentary carbonate stocks varied across seagrass communities, with meadows dominated by Halodule, Thalassia or Cymodocea supporting the highest PIC stocks, and tended to decrease polewards at a rate of -8 ± 2 Mg PIC ha-1 per degree of latitude (general linear model, GLM; p < 0.0003). Using PIC concentrations and estimates of sediment accretion in seagrass meadows, the mean PIC accumulation rate in seagrass sediments is found to be 126.3 ± 31.05 g PIC m-2 yr-1. Based on the global extent of seagrass meadows (177 000 to 600 000 km2), these ecosystems globally store between 11 and 39 Pg of PIC in the top metre of sediment and accumulate between 22 and 75 Tg PIC yr-1, representing a significant contribution to the carbonate dynamics of coastal areas. Despite the fact that these high rates of carbonate accumulation imply CO2 emissions from precipitation, seagrass meadows are still strong CO2 sinks as demonstrated by the comparison of carbon (PIC

  7. Sustainable Management of Seagrass Meadows: the GEOSS AIP-6 Pilot

    NASA Astrophysics Data System (ADS)

    Santoro, Mattia; Pastres, Roberto; Zucchetta, Matteo; Venier, Chiara; Roncella, Roberto; Bigagli, Lorenzo; Mangin, Antoine; Amine Taji, Mohamed; Gonzalo Malvarez, Gonzalo; Nativi, Stefano

    2014-05-01

    Seagrass meadows (marine angiosperm plants) occupy less than 0.2% of the global ocean surface, annually store about 10-18% of the so-called "Blue Carbon", i.e. the Carbon stored in coastal vegetated areas. Recent literature estimates that the flux to the long-term carbon sink in seagrasses represents 10-20% of seagrasses global average production. Such figures can be translated into economic benefits, taking into account that a ton of carbon dioxide in Europe is paid at around 15 € in the carbon market. This means that the organic carbon retained in seagrass sediments in the Mediterranean is worth 138 - 1128 billion €, which represents 6-23 € per square meter. This is 9-35 times more than one square meter of tropical forest soil (0.66 € per square meter), or 5-17 times when considering both the above and the belowground compartments in tropical forests. According the most conservative estimations, about 10% of the Mediterranean meadows have been lost during the last century. To estimate seagrass meadows distribution, a Species Distribution Model (SDM) can be used. SDM is a tool that is used to evaluate the potential distribution of a given species (e.g. Posidonia oceanica for seagrass) on the basis of the features (bio-chemical-physical parameters) of the studied environment. In the framework of the GEOSS (Global Earth Observation System of Systems) initiative, the FP7 project MEDINA developed a showcase as part of the GEOSS Architecture Interoperability Pilot - phase 6 (AIP-6). The showcase aims at providing a tool for the sustainable management of seagrass meadows along the Mediterranean coastline by integrating the SDM with available GEOSS resources. This way, the required input data can be searched, accessed and ingested into the model leveraging the brokering framework of the GEOSS Common Infrastructure (GCI). This framework is comprised of a set of middle-ware components (Brokers) that are in charge of implementing the needed interoperability

  8. Global and local disturbances interact to modify seagrass palatability

    PubMed Central

    Egea, Luis G.; Ortega, María J.; Hernández, Ignacio; Vergara, Juan J.; Brun, Fernando G.

    2017-01-01

    Global change, such as warming and ocean acidification, and local anthropogenic disturbances, such as eutrophication, can have profound impacts on marine organisms. However, we are far from being able to predict the outcome of multiple interacting disturbances on seagrass communities. Herbivores are key in determining plant community structure and the transfer of energy up the food web. Global and local disturbances may alter the ecological role of herbivory by modifying leaf palatability (i.e. leaf traits) and consequently, the feeding patterns of herbivores. This study evaluates the main and interactive effects of factors related to global change (i.e. elevated temperature, lower pH levels and associated ocean acidification) and local disturbance (i.e. eutrophication through ammonium enrichment) on a broad spectrum of leaf traits using the temperate seagrass Cymodocea nodosa, including structural, nutritional, biomechanical and chemical traits. The effect of these traits on the consumption rates of the generalist herbivore Paracentrotus lividus (purple sea urchin) is evaluated. The three disturbances of warming, low pH level and eutrophication, alone and in combination, increased the consumption rate of seagrass by modifying all leaf traits. Leaf nutritional quality, measured as nitrogen content, was positively correlated to consumption rate. In contrast, a negative correlation was found between feeding decisions by sea urchins and structural, biomechanical and chemical leaf traits. In addition, a notable accomplishment of this work is the identification of phenolic compounds not previously reported for C. nodosa. Our results suggest that global and local disturbances may trigger a major shift in the herbivory of seagrass communities, with important implications for the resilience of seagrass ecosystems. PMID:28813506

  9. Photosynthetic activity buffers ocean acidification in seagrass meadows

    NASA Astrophysics Data System (ADS)

    Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

    2014-01-01

    Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5-12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

  10. Coastal nitrogen plumes and their relationship with seagrass distribution

    NASA Astrophysics Data System (ADS)

    Fernandes, Milena B.; Benger, Simon; Stuart-Williams, Hilary; Gaylard, Sam; Bryars, Simon

    2015-12-01

    Urbanised coastlines are affected by cumulative impacts from a variety of anthropogenic stressors, but spatial information on the distribution of these stressors at the local scale is scarce, hindering the ability of managers to prioritise mitigation options. This work investigated the spatial footprint of land-based nitrogen discharges to a metropolitan coastline and assessed the potential role of this stressor alone on seagrass dynamics at the scale of the ecosystem. The macroalga Caulocystis cephalornithos was used as a time-integrative sampler of nitrogen in the water column over 202 sites monitored across an area of ˜800 km2. The stable isotopic signature of nitrogen in tissues (δ15N) was used to map plumes of anthropogenic origin. The surface area of these plumes was found to be proportional to nitrogen loads from land. The largest plume was associated with discharges from an industrialised estuary and a wastewater treatment plant, where a monthly nitrogen load in excess of 110 tonnes affected an area >80 km2. The location and size of the plumes changed with seasons as a result of wind forcing and rainfall/wastewater reuse. The location of the plumes was compared to published seagrass distribution obtained from video transects. Dense seagrass meadows only occurred in areas unimpacted by plumes throughout the year, mostly in shallow (<5 m) regions for Amphibolis antarctica, and deeper (5-10 m) for Posidonia sp., possibly as a result of this species higher tolerance of low light conditions. This higher tolerance might also explain why Posidonia sp. is observed to preferentially recolonise areas of previous loss in the region. While a decrease in the spatial footprint of nutrient plumes has created conditions for natural seagrass recolonisation in some areas, it did not halt seagrass loss in others, suggesting the influence of additional stressors such as wave dynamics and light attenuation due to turbid/coloured stormwater.

  11. Testing for thresholds of ecosystem collapse in seagrass meadows.

    PubMed

    Connell, Sean D; Fernandes, Milena; Burnell, Owen W; Doubleday, Zoë A; Griffin, Kingsley J; Irving, Andrew D; Leung, Jonathan Y S; Owen, Samuel; Russell, Bayden D; Falkenberg, Laura J

    2017-10-01

    Although the public desire for healthy environments is clear-cut, the science and management of ecosystem health has not been as simple. Ecological systems can be dynamic and can shift abruptly from one ecosystem state to another. Such unpredictable shifts result when ecological thresholds are crossed; that is, small cumulative increases in an environmental stressor drive a much greater change than could be predicted from linear effects, suggesting an unforeseen tipping point is crossed. In coastal waters, broad-scale seagrass loss often occurs as a sudden event associated with human-driven nutrient enrichment (eutrophication). We tested whether the response of seagrass ecosystems to coastal nutrient enrichment is subject to a threshold effect. We exposed seagrass plots to different levels of nutrient enrichment (dissolved inorganic nitrogen) for 10 months and measured net production. Seagrass response exhibited a threshold pattern when nutrient enrichment exceeded moderate levels: there was an abrupt and large shift from positive to negative net leaf production (from approximately 0.04 leaf production to 0.02 leaf loss per day). Epiphyte load also increased as nutrient enrichment increased, which may have driven the shift in leaf production. Inadvertently crossing such thresholds, as can occur through ineffective management of land-derived inputs such as wastewater and stormwater runoff along urbanized coasts, may account for the widely observed sudden loss of seagrass meadows. Identification of tipping points may improve not only adaptive-management monitoring that seeks to avoid threshold effects, but also restoration approaches in systems that have crossed them. © 2017 Society for Conservation Biology.

  12. Towards understanding temporal and spatial dynamics of seagrass landscapes using time-series remote sensing

    NASA Astrophysics Data System (ADS)

    Lyons, Mitchell B.; Roelfsema, Chris M.; Phinn, Stuart R.

    2013-03-01

    The spatial and temporal dynamics of seagrasses have been well studied at the leaf to patch scales, however, the link to large spatial extent landscape and population dynamics is still unresolved in seagrass ecology. Traditional remote sensing approaches have lacked the temporal resolution and consistency to appropriately address this issue. This study uses two high temporal resolution time-series of thematic seagrass cover maps to examine the spatial and temporal dynamics of seagrass at both an inter- and intra-annual time scales, one of the first globally to do so at this scale. Previous work by the authors developed an object-based approach to map seagrass cover level distribution from a long term archive of Landsat TM and ETM+ images on the Eastern Banks (≈200 km2), Moreton Bay, Australia. In this work a range of trend and time-series analysis methods are demonstrated for a time-series of 23 annual maps from 1988 to 2010 and a time-series of 16 monthly maps during 2008-2010. Significant new insight was presented regarding the inter- and intra-annual dynamics of seagrass persistence over time, seagrass cover level variability, seagrass cover level trajectory, and change in area of seagrass and cover levels over time. Overall we found that there was no significant decline in total seagrass area on the Eastern Banks, but there was a significant decline in seagrass cover level condition. A case study of two smaller communities within the Eastern Banks that experienced a decline in both overall seagrass area and condition are examined in detail, highlighting possible differences in environmental and process drivers. We demonstrate how trend and time-series analysis enabled seagrass distribution to be appropriately assessed in context of its spatial and temporal history and provides the ability to not only quantify change, but also describe the type of change. We also demonstrate the potential use of time-series analysis products to investigate seagrass growth and

  13. The Art of Abstracting.

    ERIC Educational Resources Information Center

    Cremmins, Edward T.

    A three-stage analytical reading method for the composition of informative and indicative abstracts by authors and abstractors is presented in this monograph, along with background information on the abstracting process and a discussion of professional considerations in abstracting. An introduction to abstracts and abstracting precedes general…

  14. Effects of CO(2) enrichment on photosynthesis, growth, and biochemical composition of seagrass Thalassia hemprichii (Ehrenb.) Aschers.

    PubMed

    Jiang, Zhi Jian; Huang, Xiao-Pin; Zhang, Jing-Ping

    2010-10-01

    The effects of CO₂ enrichment on various ecophysiological parameters of tropical seagrass Thalassia hemprichii (Ehrenb.) Aschers were tested. T. hemprichii, collected from a seagrass bed in Xincun Bay, Hainan island of Southern China, was cultured at 4 CO₂ (aq) concentrations in flow-through seawater aquaria bubbled with CO₂ . CO₂ enrichment considerably enhanced the relative maximum electron transport rate (RETR(max) ) and minimum saturating irradiance (E(k) ) of T. hemprichii. Leaf growth rate of CO₂ -enriched plants was significantly higher than that in unenriched treatment. Nonstructural carbohydrates (NSC) of T. hemprichii, especially in belowground tissues, increased strongly with elevated CO₂ (aq), suggesting a translocation of photosynthate from aboveground to belowground tissues. Carbon content in belowground tissues showed a similar response with NSC, while in aboveground tissues, carbon content was not affected by CO₂ treatments. In contrast, with increasing CO₂ (aq), nitrogen content in aboveground tissues markedly decreased, but nitrogen content in belowground was nearly constant. Carbon: nitrogen ratio in both tissues were obviously enhanced by increasing CO₂ (aq). Thus, these results indicate that T. hemprichii may respond positively to CO₂ -induced acidification of the coastal ocean. Moreover, the CO₂ -stimulated improvement of photosynthesis and NSC content may partially offset negative effects of severe environmental disturbance such as underwater light reduction.

  15. Non-native seagrass Halophila stipulacea forms dense mats under eutrophic conditions in the Caribbean

    NASA Astrophysics Data System (ADS)

    van Tussenbroek, B. I.; van Katwijk, M. M.; Bouma, T. J.; van der Heide, T.; Govers, L. L.; Leuven, R. S. E. W.

    2016-09-01

    Seagrasses comprise 78 species and are rarely invasive. But the seagrass Halophila stipulacea, firstly recorded in the Caribbean in the year 2002, has spread quickly throughout the region. Previous works have described this species as invasive in the Caribbean, forming dense mats that exclude native seagrass species. During a reconnaissance field survey of Caribbean seagrass meadows at the islands of Bonaire and Sint Maarten in 2013, we observed that this species was only extremely dense at 5 out of 10 studied meadows. Compared to areas with sparse growth of H. stipulacea, these dense meadows showed consistently higher nutrient concentrations, as indicated by higher leaf tissue N contents of the seagrass Thalassia testudinum (dense when C:N < 22.5) and sediments (dense when %N > 11.3). Thus, the potential invasiveness of this non-native seagrass most likely depends on the environmental conditions, especially the nutrient concentrations.

  16. Seagrass ecosystem trajectory depends on the relative timescales of resistance, recovery and disturbance.

    PubMed

    O'Brien, Katherine R; Waycott, Michelle; Maxwell, Paul; Kendrick, Gary A; Udy, James W; Ferguson, Angus J P; Kilminster, Kieryn; Scanes, Peter; McKenzie, Len J; McMahon, Kathryn; Adams, Matthew P; Samper-Villarreal, Jimena; Collier, Catherine; Lyons, Mitchell; Mumby, Peter J; Radke, Lynda; Christianen, Marjolijn J A; Dennison, William C

    2017-09-18

    Seagrass ecosystems are inherently dynamic, responding to environmental change across a range of scales. Habitat requirements of seagrass are well defined, but less is known about their ability to resist disturbance. Specific means of recovery after loss are particularly difficult to quantify. Here we assess the resistance and recovery capacity of 12 seagrass genera. We document four classic trajectories of degradation and recovery for seagrass ecosystems, illustrated with examples from around the world. Recovery can be rapid once conditions improve, but seagrass absence at landscape scales may persist for many decades, perpetuated by feedbacks and/or lack of seed or plant propagules to initiate recovery. It can be difficult to distinguish between slow recovery, recalcitrant degradation, and the need for a window of opportunity to trigger recovery. We propose a framework synthesizing how the spatial and temporal scales of both disturbance and seagrass response affect ecosystem trajectory and hence resilience. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Seagrass meadows globally as a coupled social-ecological system: implications for human wellbeing.

    PubMed

    Cullen-Unsworth, Leanne C; Nordlund, Lina Mtwana; Paddock, Jessica; Baker, Susan; McKenzie, Len J; Unsworth, Richard K F

    2014-06-30

    Seagrass ecosystems are diminishing worldwide and repeated studies confirm a lack of appreciation for the value of these systems. In order to highlight their value we provide the first discussion of seagrass meadows as a coupled social-ecological system on a global scale. We consider the impact of a declining resource on people, including those for whom seagrass meadows are utilised for income generation and a source of food security through fisheries support. Case studies from across the globe are used to demonstrate the intricate relationship between seagrass meadows and people that highlight the multi-functional role of seagrasses in human wellbeing. While each case underscores unique issues, these examples simultaneously reveal social-ecological coupling that transcends cultural and geographical boundaries. We conclude that understanding seagrass meadows as a coupled social-ecological system is crucial in carving pathways for social and ecological resilience in light of current patterns of local to global environmental change.

  18. Resilience of Zostera muelleri seagrass to small-scale disturbances: the relative importance of asexual versus sexual recovery

    PubMed Central

    Macreadie, Peter I; York, Paul H; Sherman, Craig DH

    2014-01-01

    beds (as opposed to bare areas arising from disturbance) must be the mechanism responsible for maintaining the observed mixed genetic composition of Z. muelleri seagrass meadows. PMID:24634729

  19. Coastal retreat and improved water quality mitigate losses of seagrass from sea level rise.

    PubMed

    Saunders, Megan I; Leon, Javier; Phinn, Stuart R; Callaghan, David P; O'Brien, Katherine R; Roelfsema, Chris M; Lovelock, Catherine E; Lyons, Mitchell B; Mumby, Peter J

    2013-08-01

    The distribution and abundance of seagrass ecosystems could change significantly over the coming century due to sea level rise (SLR). Coastal managers require mechanistic understanding of the processes affecting seagrass response to SLR to maximize their conservation and associated provision of ecosystem services. In Moreton Bay, Queensland, Australia, vast seagrass meadows supporting populations of sea turtles and dugongs are juxtaposed with the multiple stressors associated with a large and rapidly expanding human population. Here, the interactive effects of predicted SLR, changes in water clarity, and land use on future distributions of seagrass in Moreton Bay were quantified. A habitat distribution model of present day seagrass in relation to benthic irradiance and wave height was developed which correctly classified habitats in 83% of cases. Spatial predictions of seagrass and presence derived from the model and bathymetric data were used to initiate a SLR inundation model. Bathymetry was iteratively modified based on SLR and sedimentary accretion in seagrass to simulate potential seagrass habitat at 10 year time steps until 2100. The area of seagrass habitat was predicted to decline by 17% by 2100 under a scenario of SLR of 1.1 m. A scenario including the removal of impervious surfaces, such as roads and houses, from newly inundated regions, demonstrated that managed retreat of the shoreline could potentially reduce the overall decline in seagrass habitat to just 5%. The predicted reduction in area of seagrass habitat could be offset by an improvement in water clarity of 30%. Greater improvements in water clarity would be necessary for larger magnitudes of SLR. Management to improve water quality will provide present and future benefits to seagrasses under climate change and should be a priority for managers seeking to compensate for the effects of global change on these valuable habitats. © 2013 John Wiley & Sons Ltd.

  20. Dietary preferences of two seagrass inhabiting gastropods: Allochthonous vs autochthonous resources

    NASA Astrophysics Data System (ADS)

    Doropoulos, C.; Hyndes, G. A.; Lavery, P. S.; Tuya, F.

    2009-06-01

    The movement of allochthonous resources between habitats can provide important trophic linkages in marine landscapes. In coastal south-western Australia, the kelp Ecklonia radiata is removed from reefs and accumulates in large quantities in neighbouring seagrass meadows. This study investigated the feeding preferences and grazing rates of two locally abundant gastropods, Pyrene bidentata and Cantharidus lepidus, which exhibit inverse distribution patterns with proximity to reefs in seagrass meadows, to determine whether allochthonous kelp has the potential to contribute to the seagrass food web. Using laboratory choice and no-choice feeding experiments, we tested whether detached kelp is consumed preferentially, and at greater rates, by these two species than autochthonous resources (i.e. seagrass, epiphytic red macroalgae and seagrass periphyton). Both species displayed a preference for macroalgae and seagrass periphyton over seagrass leaves. In choice experiments, neither species displayed any clear preference between kelp (fresh or aged), red macroalgae or periphyton (consumption rates ranged between 0.39 and 3.64 mg ind -1 day -1), but consumption rates were always higher relative to seagrass. In no-choice experiments, P. bidentata displayed minimal consumption of seagrass, but consumed fresh and aged kelp, red macroalgae and seagrass periphyton at similar rates (2.00-7.22 mg ind -1 day -1). In comparison, C. lepidus consumed periphyton at far greater rates than any other food source (3.61 vs 0.33-1.10 mg ind -1 day -1). The results indicate that both P. bidentata and C. lepidus showed a clear preference for macroalgae and periphyton over seagrass, but no consistent preference towards any autochthonous or allochthonous algal resource. Reef-derived kelp therefore has the potential to contribute to the food web of seagrass meadows, and subsidise secondary production.

  1. Challenges of remote sensing for quantifying changes in large complex seagrass environments

    NASA Astrophysics Data System (ADS)

    Roelfsema, Chris; Kovacs, Eva M.; Saunders, Megan I.; Phinn, Stuart; Lyons, Mitchell; Maxwell, Paul

    2013-11-01

    Managing seagrass environments and understanding and responding to coastal impacts such as floods or cyclones, requires assessment of seagrass distribution and its biophysical properties in time and space. Comparable assessments of seagrass distribution over time are often lacking as the information is present for separate dates, or created following different mapping approaches, and this makes it difficult to conduct quantitative comparisons. We provide an assessment of available data sets and approaches, and their suitability for monitoring and quantifying change in seagrass percentage cover and extent for a large coastal embayment (Moreton Bay, Australia, 1582 km2). Seagrass percentage cover maps were created for 2011 and 2004 and compared to map and measure the extent of seagrass percentage cover change, and changes in the extent of seagrass environments. Total extent of seagrass was shown to be higher in 2011 compared to 2004. Potential sources of these differences may be: mapping inaccuracy; actual change in extent and cover; and, monthly to seasonal variations in seagrass cover. A qualitative comparison of the 2004 and 2011 maps was performed against maps of seagrass extent maps from 1975, 1986 and 1999, which were created using a range of different methods and data. The output maps show changes in seagrass extent, but a lack of detail arising from variable mapping methods and differing mapping extents prevented a reliable comparison. We conclude that robust mapping of seasonal and inter-annual variation in seagrass percentage cover distribution or extent, as well as impacts of episodic and stochastic disturbance events, requires a thorough understanding of the mapping approaches used so that data sets can be compared. Additional complimentary information is required to help understand the drivers of changes.

  2. Seagrass as pasture for seacows: Landscape-level dugong habitat evaluation

    NASA Astrophysics Data System (ADS)

    Sheppard, James K.; Lawler, Ivan R.; Marsh, Helene

    2007-01-01

    A 24 km 2 seagrass meadow in Hervey Bay, Queensland, Australia, was confirmed as important dugong habitat by a satellite tracking study. Marine videography, near-infrared spectroscopy (NIRS) and geographic information systems (GIS) were used to survey, analyse and map seagrass species composition, nutrient profile and patch structure at high resolution (200 m). Five species of seagrass covered 91% of the total habitat area. The total above and below-ground seagrass biomass was estimated to be 222.7 ± 19.6 t dry-weight. Halodule uninervis dominated the pasture (81.8%, 162.2 t), followed by Halophila ovalis (35.3%, 16.5 t), Zostera capricorni (15.9%, 22.2 t), Halophila spinulosa (14.5%, 21.9 t), and traces of Halodule pinifolia. Because seagrass distributions overlapped, their combined percentage totalled >100% of the survey area. The seagrass formed a continuous meadow of varying density. Abiotic variables explained relatively little of the spatial patterns in the seagrass. For all seagrass species, the above-ground component (shoots and leaves) possessed greater total nitrogen than the below-ground component (roots and rhizomes), which possessed greater total starch. Because of the relatively low intraspecific variation in nutrient composition, nutrients were concentrated according to seagrass biomass density. Halodule uninervis was the most nutritious seagrass species because of its superior whole-plant nitrogen (1.28 ± 0.05% DW) and starch (6.42 ± 0.50 DW %) content. Halodule uninervis formed large, clustered patches of dense biomass across the pasture and thus nitrogen and starch were concentrated where H. uninervis was prevalent. This seagrass meadow appears to be utilised well below its potential dugong carrying capacity. The survey and analytical techniques used enabled rapid, economical and accurate quantification and characterisation of seagrass habitat at scales relevant to a large forager.

  3. Interoperability challenges for the Sustainable Management of seagrass meadows (Invited)

    NASA Astrophysics Data System (ADS)

    Nativi, S.; Pastres, R.; Bigagli, L.; Venier, C.; Zucchetta, M.; Santoro, M.

    2013-12-01

    Seagrass meadows (marine angiosperm plants) occupy less than 0.2% of the global ocean surface, annually store about 10-18% of the so-called 'Blue Carbon', i.e. the Carbon stored in coastal vegetated areas. Recent literature estimates that the flux to the long-term carbon sink in seagrasses represents 10-20% of seagrasses global average production. Such figures can be translated into economic benefits, taking into account that a ton of carbon dioxide in Europe is paid at around 15 € in the carbon market. This means that the organic carbon retained in seagrass sediments in the Mediterranean is worth 138 - 1128 billion €, which represents 6-23 € per square meter. This is 9-35 times more than one square meter of tropical forest soil (0.66 € per square meter), or 5-17 times when considering both the above and the belowground compartments in tropical forests. According the most conservative estimations, about 10% of the Mediterranean meadows have been lost during the last century. In the framework of the GEOSS (Global Earth Observation System of Systems) initiative, the MEDINA project (funded by the European Commission and coordinated by the University of Ca'Foscari in Venice) prepared a showcase as part of the GEOSS Architecture Interoperability Pilot -phase 6 (AIP-6). This showcase aims at providing a tool for the sustainable management of seagrass meadows along the Mediterranean coastline. The application is based on an interoperability framework providing a set of brokerage services to easily ingest and run a Habitat Suitability model (a model predicting the probability a given site to provide a suitable habitat for the development of seagrass meadow and the average coverage expected). The presentation discusses such a framework explaining how the input data is discovered, accessed and processed to ingest the model (developed in the MEDINA project). Furthermore, the brokerage framework provides the necessary services to run the model and visualize results

  4. Rhizosphere Microbiomes of European + Seagrasses Are Selected by the Plant, But Are Not Species Specific.

    PubMed

    Cúcio, Catarina; Engelen, Aschwin H; Costa, Rodrigo; Muyzer, Gerard

    2016-01-01

    Seagrasses are marine flowering plants growing in soft-body sediments of intertidal and shallow sub-tidal zones. They play an important role in coastal ecosystems by stabilizing sediments, providing food and shelter for animals, and recycling nutrients. Like other plants, seagrasses live intimately with both beneficial and unfavorable microorganisms. Although much is known about the microbiomes of terrestrial plants, little is known about the microbiomes of seagrasses. Here we present the results of a detailed study on the rhizosphere microbiome of seagrass species across the North-eastern Atlantic Ocean: Zostera marina, Zostera noltii, and Cymodocea nodosa. High-resolution amplicon sequencing of 16S rRNA genes showed that the rhizobiomes were significantly different from the bacterial communities of surrounding bulk sediment and seawater. Although we found no significant differences between the rhizobiomes of different seagrass species within the same region, those of seagrasses in different geographical locations differed strongly. These results strongly suggest that the seagrass rhizobiomes are shaped by plant metabolism, but not coevolved with their host. The core rhizobiome of seagrasses includes mostly bacteria involved in the sulfur cycle, thereby highlighting the importance of sulfur-related processes in seagrass ecosystems.

  5. Rhizosphere Microbiomes of European Seagrasses Are Selected by the Plant, But Are Not Species Specific

    PubMed Central

    Cúcio, Catarina; Engelen, Aschwin H.; Costa, Rodrigo; Muyzer, Gerard

    2016-01-01

    Seagrasses are marine flowering plants growing in soft-body sediments of intertidal and shallow sub-tidal zones. They play an important role in coastal ecosystems by stabilizing sediments, providing food and shelter for animals, and recycling nutrients. Like other plants, seagrasses live intimately with both beneficial and unfavorable microorganisms. Although much is known about the microbiomes of terrestrial plants, little is known about the microbiomes of seagrasses. Here we present the results of a detailed study on the rhizosphere microbiome of seagrass species across the North-eastern Atlantic Ocean: Zostera marina, Zostera noltii, and Cymodocea nodosa. High-resolution amplicon sequencing of 16S rRNA genes showed that the rhizobiomes were significantly different from the bacterial communities of surrounding bulk sediment and seawater. Although we found no significant differences between the rhizobiomes of different seagrass species within the same region, those of seagrasses in different geographical locations differed strongly. These results strongly suggest that the seagrass rhizobiomes are shaped by plant metabolism, but not coevolved with their host. The core rhizobiome of seagrasses includes mostly bacteria involved in the sulfur cycle, thereby highlighting the importance of sulfur-related processes in seagrass ecosystems. PMID:27065991

  6. Seagrass Restoration Enhances “Blue Carbon” Sequestration in Coastal Waters

    PubMed Central

    Greiner, Jill T.; McGlathery, Karen J.; Gunnell, John; McKee, Brent A.

    2013-01-01

    Seagrass meadows are highly productive habitats that provide important ecosystem services in the coastal zone, including carbon and nutrient sequestration. Organic carbon in seagrass sediment, known as “blue carbon,” accumulates from both in situ production and sedimentation of particulate carbon from the water column. Using a large-scale restoration (>1700 ha) in the Virginia coastal bays as a model system, we evaluated the role of seagrass, Zosteramarina, restoration in carbon storage in sediments of shallow coastal ecosystems. Sediments of replicate seagrass meadows representing different age treatments (as time since seeding: 0, 4, and 10 years), were analyzed for % carbon, % nitrogen, bulk density, organic matter content, and 210Pb for dating at 1-cm increments to a depth of 10 cm. Sediment nutrient and organic content, and carbon accumulation rates were higher in 10-year seagrass meadows relative to 4-year and bare sediment. These differences were consistent with higher shoot density in the older meadow. Carbon accumulation rates determined for the 10-year restored seagrass meadows were 36.68 g C m-2 yr-1. Within 12 years of seeding, the restored seagrass meadows are expected to accumulate carbon at a rate that is comparable to measured ranges in natural seagrass meadows. This the first study to provide evidence of the potential of seagrass habitat restoration to enhance carbon sequestration in the coastal zone. PMID:23967303

  7. SMALL-SCALE HETEROGENEITY IN THE GEOCHEMISTRY OF SEAGRASS VEGETATED AND NON-VEGETATIVE SEDIMENTS: CAUSES AND CONSEQUENCES

    EPA Science Inventory

    In addition to nutrient and light availability, sedimentary biogeochemical processes can play an essential role in seagrass productivity. Previous investigations of the interactions between seagrasses and their underlying sediments have failed to clearly identify the spatio-tempo...

  8. SMALL-SCALE HETEROGENEITY IN THE GEOCHEMISTRY OF SEAGRASS VEGETATED AND NON-VEGETATIVE SEDIMENTS: CAUSES AND CONSEQUENCES

    EPA Science Inventory

    In addition to nutrient and light availability, sedimentary biogeochemical processes can play an essential role in seagrass productivity. Previous investigations of the interactions between seagrasses and their underlying sediments have failed to clearly identify the spatio-tempo...

  9. Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to Zostera noltii beds

    NASA Astrophysics Data System (ADS)

    Vafeiadou, A.-M.; Materatski, P.; Adão, H.; De Troch, M.; Moens, T.

    2014-01-01

    This study examines the resource use and trophic position of nematodes and harpacticoid copepods at the genus/species level in an estuarine food web in Zostera noltii beds and in adjacent bare sediments, using the natural abundance of stable carbon and nitrogen isotopes. Microphytobenthos is among the main resources of most taxa, but seagrass-associated resources (i.e. seagrass detritus and epiphytes) also contribute to meiobenthos nutrition, with seagrass detritus being available also in deeper sediments and in unvegetated patches close to seagrass beds. A predominant dependence on chemoautotrophic bacteria was demonstrated for the nematode genus Terschellingia and the copepod family Cletodidae. A predatory feeding mode is illustrated for Paracomesoma and other Comesomatidae, which were previously considered first-level consumers (deposit feeders) according to their buccal morphology. The considerable variation found in both resource use and trophic level among nematode genera from the same feeding type, and even among congeneric nematode species, shows that interpretation of nematode feeding ecology based purely on mouth morphology should be avoided.

  10. Photosynthetic carbon reduction by seagrasses exposed to ultraviolet A radiation

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The seagrasses Halophila engelmannii, Halodule wrightii, and Syringodium filiforme were examined for their intrinsic sensitivity to ultraviolet-A-UV-A and ultraviolet-B-UV-B radiation. The effect of UV-A on photosynthetically active radiation (PAR) was also determined. Ultraviolet-A and ultraviolet-B were studied with emphasis on the greater respective environmental consequence in terms of seagrass distribution and abundance. Results indicate that an intrinsic sensitivity to UV-A alone is apparent only in Halophila, while net photosynthesis in Halodule and Syringodium seems unaffected by the level of UV-A provided. The sensitivity of Halophila to UV-A in the absense of (PAR) indicates that the photosynthetic reaction does not need to be in operation for damage to occur. Other significant results are reported.

  11. The perilous state of seagrass in the British Isles

    PubMed Central

    Jones, Benjamin L.; Unsworth, Richard K. F.

    2016-01-01

    Seagrass ecosystems face widespread threat from reduced water quality, coastal development and poor land use. In recent decades, their distribution has declined rapidly, and in the British Isles, this loss is thought to have been extensive. Given increasing knowledge of how these ecosystems support fisheries production, the understanding of their potential rapid loss, and the difficulty in restoring them, it is vital we develop an understanding of the risks they are under, so that management actions can be developed accordingly. Developing an understanding of their environmental status and condition is therefore critical to their long-term management. This study provided, to our knowledge, the first examination of the environmental health of seagrass meadows around the British Isles. This study used a bioindicator approach and involved collecting data on seagrass density and morphology alongside analysis of leaf biochemistry. Our study provides, to the best of our knowledge, the first strong quantitative evidence that seagrass meadows of the British Isles are mostly in poor condition in comparison with global averages, with tissue nitrogen levels 75% higher than global values. Such poor status places their long-term resilience in doubt. Elemental nutrient concentrations and morphological change suggest conditions of excess nitrogen and probable low light, placing many of the meadows sampled in a perilous state, although others, situated away from human populations were perceived to be healthy. Although some sites were of a high environmental health, all sites were considered at risk from anthropogenic impacts, particularly poor water quality and boating-based disturbances. The findings of this study provide a warning of the need to take action, with respect to water quality and disturbance, to prevent the further loss and degradation of these systems across the British Isles. PMID:26909188

  12. Waves in Seagrass Systems: Review and Technical Recommendations

    DTIC Science & Technology

    2006-11-01

    maritima), when repro- ductive, form long vertical stems that can occupy most of or the entire wa- ter column. When most of the plant biomass...response to changes in turbidity stemming from bivalve filtration and seagrass sediment stabilization. Estuaries 27:793-806. Nikora, V. I., D. G...Teeter, A. M., B. H. Johnson, C. Berger, G. Stelling , N. W. Scheffner, M. H. Garcia, and T. M. Parchure. 2001. Hydrodynamic and sediment transport

  13. Seagrass feeding choices and digestive strategies of the herbivorous fish Sarpa salpa.

    PubMed

    Goldenberg, S U; Erzini, K

    2014-05-01

    This is the first study investigating the plant-herbivore interaction between Sarpa salpa, which has overgrazed seagrass transplants in Portugal, and the seagrasses Cymodocea nodosa, Zostera marina and Zostera noltii, which have been considered for restoration. When offered the choice between the three seagrasses in outdoor tanks, adult S. salpa clearly preferred Z. noltii. Testing the seagrasses separately, mean ± s.d. feeding rates ranged from 21 ± 11 g seagrass fresh mass kg⁻¹ fish mass day⁻¹ for Z. marina to 32 ± 9 g seagrass fresh mass kg⁻¹ fish mass day⁻¹ for C. nodosa and 40 ± 11 g seagrass fresh mass kg⁻¹ fish mass day⁻¹ for Z. noltii (temperature = 16° C). Food-processing rate in S. salpa did not differ between seagrasses, and there was no evidence of a regulation of processing rate according to food intake. Seagrasses differed substantially in nitrogen content and C:N, with C. nodosa containing the highest nitrogen content and lowest C:N (2·5 ± 0·1% and 14·0 ± 1·0), followed by Z. noltii (2·1 ± 0·1% and 17·0 ± 1·0) and Z. marina (1·4 ± 0·1% and 26·0 ± 2·0). Food-processing rate in S. salpa and the nutritional value of the seagrasses were not correlated with the observed feeding preference and rate. The study suggests that C. nodosa and Z. marina are less at risk of overgrazing by S. salpa and might thus be preferable to Z. noltii for seagrass restoration in areas with noticeable abundances of this fish.

  14. Unravelling complexity in seagrass systems for management: Australia as a microcosm.

    PubMed

    Kilminster, Kieryn; McMahon, Kathryn; Waycott, Michelle; Kendrick, Gary A; Scanes, Peter; McKenzie, Len; O'Brien, Katherine R; Lyons, Mitchell; Ferguson, Angus; Maxwell, Paul; Glasby, Tim; Udy, James

    2015-11-15

    Environmental decision-making applies transdisciplinary knowledge to deliver optimal outcomes. Here we synthesise various aspects of seagrass ecology to aid environmental decision-making, management and policy. Managers often mediate conflicting values and opinions held by different stakeholders. Critical to this role is understanding the drivers for change, effects of management actions and societal benefits. We use the diversity of seagrass habitats in Australia to demonstrate that knowledge from numerous fields is required to understand seagrass condition and resilience. Managers are often time poor and need access to synthesised assessments, commonly referred to as narratives. However, there is no single narrative for management of seagrass habitats in Australia, due to the diversity of seagrass meadows and dominant pressures. To assist the manager, we developed a classification structure based on attributes of seagrass life history, habitat and meadow form. Seagrass communities are formed from species whose life history strategies can be described as colonising, opportunistic or persistent. They occupy habitats defined by the range and variability of their abiotic environment. This results in seagrass meadows that are either transitory or enduring. Transitory meadows may come and go and able to re-establish from complete loss through sexual reproduction. Enduring meadows may fluctuate in biomass but maintain a presence by resisting pressures across multiple scales. This contrast reflects the interaction between the spatial and temporal aspects of species life history and habitat variability. Most management and monitoring strategies in place today favour enduring seagrasses. We adopt a functional classification of seagrass habitats based on modes of resilience to inform management for all seagrass communities. These concepts have world-wide relevance as the Australian case-studies have many analogues throughout the world. Additionally, the approach used to

  15. Temperature extremes reduce seagrass growth and induce mortality.

    PubMed

    Collier, C J; Waycott, M

    2014-06-30

    Extreme heating (up to 43 °C measured from five-year temperature records) occurs in shallow coastal seagrass meadows of the Great Barrier Reef at low tide. We measured effective quantum yield (ϕPSII), growth, senescence and mortality in four tropical seagrasses to experimental short-duration (2.5h) spikes in water temperature to 35 °C, 40 °C and 43 °C, for 6 days followed by one day at ambient temperature. Increasing temperature to 35 °C had positive effects on ϕPSII (the magnitude varied between days and was highly correlated with PPFD), with no effects on growth or mortality. 40 °C represented a critical threshold as there were strong species differences and there was a large impact on growth and mortality. At 43 °C there was complete mortality after 2-3 days. These findings indicate that increasing duration (more days in a row) of thermal events above 40 °C is likely to affect the ecological function of tropical seagrass meadows. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Sulfide Intrusion and Detoxification in the Seagrass Zostera marina.

    PubMed

    Hasler-Sheetal, Harald; Holmer, Marianne

    2015-01-01

    Gaseous sulfide intrusion into seagrasses growing in sulfidic sediments causes little or no harm to the plant, indicating the presence of an unknown sulfide tolerance or detoxification mechanism. We assessed such mechanism in the seagrass Zostera marina in the laboratory and in the field with scanning electron microscopy coupled to energy dispersive X-ray spectroscopy, chromatographic and spectrophotometric methods, and stable isotope tracing coupled with a mass balance of sulfur compounds. We found that Z. marina detoxified gaseous sediment-derived sulfide through incorporation and that most of the detoxification occurred in underground tissues, where sulfide intrusion was greatest. Elemental sulfur was a major detoxification compound, precipitating on the inner wall of the aerenchyma of underground tissues. Sulfide was metabolized into thiols and entered the plant sulfur metabolism as well as being stored as sulfate throughout the plant. We conclude that avoidance of sulfide exposure by reoxidation of sulfide in the rhizosphere or aerenchyma and tolerance of sulfide intrusion by incorporation of sulfur in the plant are likely major survival strategies of seagrasses in sulfidic sediments.

  17. Sulfide Intrusion and Detoxification in the Seagrass Zostera marina

    PubMed Central

    Hasler-Sheetal, Harald; Holmer, Marianne

    2015-01-01

    Gaseous sulfide intrusion into seagrasses growing in sulfidic sediments causes little or no harm to the plant, indicating the presence of an unknown sulfide tolerance or detoxification mechanism. We assessed such mechanism in the seagrass Zostera marina in the laboratory and in the field with scanning electron microscopy coupled to energy dispersive X-ray spectroscopy, chromatographic and spectrophotometric methods, and stable isotope tracing coupled with a mass balance of sulfur compounds. We found that Z. marina detoxified gaseous sediment-derived sulfide through incorporation and that most of the detoxification occurred in underground tissues, where sulfide intrusion was greatest. Elemental sulfur was a major detoxification compound, precipitating on the inner wall of the aerenchyma of underground tissues. Sulfide was metabolized into thiols and entered the plant sulfur metabolism as well as being stored as sulfate throughout the plant. We conclude that avoidance of sulfide exposure by reoxidation of sulfide in the rhizosphere or aerenchyma and tolerance of sulfide intrusion by incorporation of sulfur in the plant are likely major survival strategies of seagrasses in sulfidic sediments. PMID:26030258

  18. Genetic diversity of seagrass seeds influences seedling morphology and biomass.

    PubMed

    Randall Hughes, A; Hanley, Torrance C; Schenck, Forest R; Hays, Cynthia G

    2016-12-01

    Genetic diversity can influence ecological processes throughout ontogeny, yet whether diversity at early life history stages is important in long-lived taxa with overlapping generations is unclear. Seagrass systems provide some of the best evidence for the ecological effects of genetic diversity among adult shoots, but we do not know if the genetic diversity of seeds and seedlings also influences seagrass ecology. We tested the effects of seagrass (Zostera marina) seed diversity and relatedness on germination success, seedling morphology, and seedling production by comparing experimental assemblages of seeds collected from single reproductive shoots ("monocultures") to assemblages of seeds collected from multiple reproductive shoots ("polycultures"). There was no difference in seedling emergence, yet seedlings from polycultures had larger shoots above and below ground than seedlings from monocultures at the end of the 1-yr experiment. Genetic relatedness of the seedlings predicted some aspects of shoot morphology, with more leaves and longer roots and shoots at intermediate levels of relatedness, regardless of seed diversity. Our results suggest that studies of only adult stages may underestimate the importance of genetic diversity if the benefits at early life history stages continue to accrue throughout the life cycle.

  19. Middle Eocene seagrass facies from Apennine carbonate platforms (Italy)

    NASA Astrophysics Data System (ADS)

    Tomassetti, Laura; Benedetti, Andrea; Brandano, Marco

    2016-04-01

    Two stratigraphic sections located in the Latium-Abruzzi (Monte Porchio, Central Apennines, Central Italy) and in the Apulian carbonate platform (S. Cesarea-Torre Tiggiano, Salento, Southern Italy) were measured and sampled to document the sedimentological characteristic and the faunistic assemblages of Middle Eocene seagrass deposits. The faunistic assemblages are dominated by porcellaneous foraminifera Orbitolites, Alveolina, Idalina, Spiroloculina, Quinqueloculina, Triloculina and abundant hooked-shaped gypsinids, associated with hooked red algae and green algae Halimeda. Fabiania, rotaliids and textulariids as well as nummulitids are subordinated. The samples were assigned to Lutetian (SBZ13-16) according to the occurrence of Nummulites cf. lehneri, Alveolina ex. gr. elliptica, Idalina berthelini, Orbitolites complanatus, Slovenites decastroi and Medocia blayensis. At Santa Cesarea reticulate nummulites occur in association with Alveolina spp. and Halkyardia minima marking the lower Bartonian (SBZ17). Three main facies associations have been recognised: I) larger porcellaneous foraminiferal grainstones with orbitolitids and alveolinids deposited into high-energy shallow-water settings influenced by wave processes that reworked the sediments associated with a seagrass; II) grainstone to packstone with small porcellaneous foraminifera and abundant permanently-attached gypsinids deposited in a more protected (e.g., small embayment) in situ vegetated environment; III) bioclastic packstone with parautochthonous material reworked from the seagrass by rip currents and accumulated into rip channels in a slightly deeper environment. The biotic assemblages suggest that the depositional environment is consistent with tropical to subtropical vegetated environments within oligotrophic conditions.

  20. A Bayesian spatial approach for predicting seagrass occurrence

    NASA Astrophysics Data System (ADS)

    March, D.; Alós, J.; Cabanellas-Reboredo, M.; Infantes, E.; Jordi, A.; Palmer, M.

    2013-10-01

    We implement a Bayesian spatial approach to predict and map the probability of occurrence of seagrass Posidonia oceanica at high spatial resolution based environmental variables. We found that depth, near-bottom orbital velocities and a spectral pattern of Landsat imagery were relevant environmental variables, although there was no effect of slope or water residence time. We generated a data inventory of P. oceanica samples at Palma Bay, NW Mediterranean, from three main sources: side scan sonar, aerial imagery and a customized drop-camera system. A hierarchical Bayesian spatial model for non-Gaussian data was used to relate presence-absence data of P. oceanica with environmental variables in the presence of spatial autocorrelation (SA). A spatial dimension reduction method, the predictive process approach, was implemented to overcome computational constraints for moderately large datasets. Our results suggest that incorporating spatial random effects removes SA from the residuals and improves model fit compared to non-spatial regression models. The main products of this work were probability and uncertainty model maps, which could benefit seagrass management and the assessment of the ecological status of seagrass meadows.

  1. Evaluation of a Single-Beam Sonar System to Map Seagrass at Two Sites in Northern Puget Sound, Washington

    USGS Publications Warehouse

    Stevens, Andrew W.; Lacy, Jessica R.; Finlayson, David P.; Gelfenbaum, Guy

    2008-01-01

    Seagrass at two sites in northern Puget Sound, Possession Point and nearby Browns Bay, was mapped using both a single-beam sonar and underwater video camera. The acoustic and underwater video data were compared to evaluate the accuracy of acoustic estimates of seagrass cover. The accuracy of the acoustic method was calculated for three classifications of seagrass observed in underwater video: bare (no seagrass), patchy seagrass, and continuous seagrass. Acoustic and underwater video methods agreed in 92 percent and 74 percent of observations made in bare and continuous areas, respectively. However, in patchy seagrass, the agreement between acoustic and underwater video was poor (43 percent). The poor agreement between the two methods in areas with patchy seagrass is likely because the two instruments were not precisely colocated. The distribution of seagrass at the two sites differed both in overall percent vegetated and in the distribution of percent cover versus depth. On the basis of acoustic data, seagrass inhabited 0.29 km2 (19 percent of total area) at Possession Point and 0.043 km2 (5 percent of total area) at the Browns Bay study site. The depth distribution at the two sites was markedly different. Whereas the majority of seagrass at Possession Point occurred between -0.5 and -1.5 m MLLW, most seagrass at Browns Bay occurred at a greater depth, between -2.25 and -3.5 m MLLW. Further investigation of the anthropogenic and natural factors causing these differences in distribution is needed.

  2. Modelling benthic macrofauna and seagrass distribution patterns in a North Sea tidal basin in response to 2050 climatic and environmental scenarios

    NASA Astrophysics Data System (ADS)

    Singer, Anja; Millat, Gerald; Staneva, Joanna; Kröncke, Ingrid

    2017-03-01

    Small-scale spatial distribution patterns of seven macrofauna species, seagrass beds and mixed mussel/oyster reefs were modelled for the Jade Bay (North Sea, Germany) in response to climatic and environmental scenarios (representing 2050). For the species distribution models four presence-absence modelling methods were merged within the ensemble forecasting platform 'biomod2'. The present spatial distribution (representing 2009) was modelled by statistically related species presences, true species absences and six high-resolution environmental grids. The future spatial distribution was then predicted in response to expected climate change-induced ongoing (1) sea-level rise and (2) water temperature increase. Between 2009 and 2050, the present and future prediction maps revealed a significant range gain for two macrofauna species (Macoma balthica, Tubificoides benedii), whereas the species' range sizes of five macrofauna species remained relatively stable across space and time. The predicted probability of occurrence (PO) of two macrofauna species (Cerastoderma edule, Scoloplos armiger) decreased significantly under the potential future habitat conditions. In addition, a clear seagrass bed extension (Zostera noltii) on the lower intertidal flats (mixed sediments) and a decrease in the PO of mixed Mytilus edulis/Crassostrea gigas reefs was predicted for 2050. Until the mid-21st century, our future climatic and environmental scenario revealed significant changes in the range sizes (gains-losses) and/or the PO (increases-decreases) for seven of the 10 modelled species at the study site.

  3. Photosynthetic activity buffers ocean acidification in seagrass meadows

    NASA Astrophysics Data System (ADS)

    Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

    2013-07-01

    Macrophytes growing in shallow coastal zones characterized by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH ranges is in shallow (5-12 m) seagrass (Posidonia oceanica) meadows from 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean and max pHNBS and max ΩAr. Oxygen production positively influenced the range and maximum pHNBS and the range of ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. ΩAr was positively correlated with the calcium carbonate load of the leaves, demonstrating a direct link between structural parameters, ΩAr and carbonate deposition. There was a direct relationship between ΩAr, influenced directly by meadow LAI, and CaCO3 content of the leaves. Therefore, calcifying organisms, e.g. epiphytes with carbonate skeletons, might benefit from the modification of the carbonate system by the meadow. The meadow might be capable of providing refugia for calcifiers by increasing pH and ΩAr through metabolic activity. There is, however, concern for the ability of seagrasses to provide this refugia function in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, both strongly linked to LAI. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

  4. Effects of Lyngbya majuscula blooms on the seagrass Halodule wrightii and resident invertebrates.

    PubMed

    Tiling, Kathryn; Proffitt, C Edward

    2017-02-01

    Cyanobacterial blooms have been increasing worldwide due to increased nutrients associated with urban, industrial, and agricultural development. Blooms that occur in the Indian River Lagoon (IRL), Florida may be increased by nutrient-laden runoff from storm water and non-point sewage pollution due to alterations to the watershed. In the IRL, during the summer of 2006, extensive blooms of the marine cyanobacterium, Lyngbya majuscula, were observed forming mats throughout beds of the seagrass Halodule wrightii in Fort Pierce, Florida. The effects of cyanobacterial blooms were compared to artificial shading of H. wrightii to assess the shading potential of L. majuscula. The combined effects of L. majuscula removal and artificial shading showed increases in the below ground biomass of H. wrightii. However, leaf length increased in the presence of L. majuscula. In response to artificial shading, H. wrightii decreased in density, but showed similar leaf elongation. A common bivalve in our study area, Macoma constricta, increased in density when L. majuscula was removed. Therefore, when L. majuscula blooms occur, light limitation is one of the mechanisms altering H. wrightii density and leaf lengths in the IRL. Loss of H. wrightii biomass due to shading from cyanobacterial mats may further damage the diversity and habitat value of the IRL. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Variability of bed mobility in natural, gravel-bed channels and adjustments to sediment load at local and reach scales

    Treesearch

    Thomas E. Lisle; Jonathan M. Nelson; John Pitlick; Mary Ann Madej; Brent L. Barkett

    2000-01-01

    Abstract - Local variations in boundary shear stress acting on bed-surface particles control patterns of bed load transport and channel evolution during varying stream discharges. At the reach scale a channel adjusts to imposed water and sediment supply through mutual interactions among channel form, local grain size, and local flow dynamics that govern bed mobility...

  6. SEAGRASS EPIPHYTES AS A NUTRIENT STRESSOR INDICATOR: APPROACHES TOWARDS DEVELOPMENT OF THRESHOLD VALUES.

    EPA Science Inventory

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experim...

  7. Losses and recovery of organic carbon from a seagrass ecosystem following disturbance.

    PubMed

    Macreadie, Peter I; Trevathan-Tackett, Stacey M; Skilbeck, Charles G; Sanderman, Jonathan; Curlevski, Nathalie; Jacobsen, Geraldine; Seymour, Justin R

    2015-10-22

    Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences. © 2015 The Author(s).

  8. Habitat restoration: Early signs and extent of faunal recovery relative to seagrass recovery

    NASA Astrophysics Data System (ADS)

    McSkimming, Chloe; Connell, Sean D.; Russell, Bayden D.; Tanner, Jason E.

    2016-03-01

    The overall intent of restoration is often not only to restore the habitat per se, but to restore the ecosystem services it supplies, and particularly to encourage the return of fauna. Seagrass meadows act as habitat for some of the most diverse and abundant animal life, and as the global loss of seagrass continues, managers have sought to restore lost meadows. We tested how quickly the epifaunal richness, abundances and community composition of experimental restoration plots recovered to that in an adjacent natural seagrass meadow relative to the recovery of seagrass per se. Seagrass structure in the restoration plots took three years to become similar to a nearby natural meadow. The recovery of epifaunal richness and total abundance, however, occurred within one year. These results suggest that although recovering habitats may not be structurally similar to undisturbed habitats, they can support similar richness and abundances of epifauna, and thus have greater economic and social value than otherwise might have been expected. Nevertheless, whilst epifaunal richness and total abundance recovered prior to the recovery of seagrass structure, full recovery of seagrass was required before the composition and relative abundances of the epifaunal community matched that of the natural seagrass meadow.

  9. Learning about Coastal Trends: What Is the Story with Seagrass... and How Does It Affect Me?

    ERIC Educational Resources Information Center

    Ksiazek, Kelly; McGlathery, Karen; Reynolds, Laura; Schwarzschild, Arthur; Wilkerson, Carissa; Carruthers, Tim; Gurbisz, Cassie; Woerner, Joanna L.; Murray, Laura

    2009-01-01

    Flowering plants that live underwater in marine and estuarine habitats (seagrasses) are important because they support human food sources, such as crabs and fish, as well as endangered animals, such as turtles and manatees. Seagrasses are now known to be declining globally, largely as a result of increasing pressure from human populations living…

  10. DYNAMICS OF A SUBTIDAL SEAGRASS LANDSCAPE: SEASONAL AND ANNUAL CHANGE IN RELATION TO WATER DEPTH

    EPA Science Inventory

    The spatial heterogeneity of a subtidal marine landscape and the areal extent of both monospecific and mixed patches of seagrass species were studied in Tampa Bay, FL. Specifically, we examined the temporal dynamics of seagrass distribution and its relationship to water depth an...

  11. USE OF WAVE EXPOSURE TECHNIQUE FOR PREDICTING DISTRIBUTION AND ECOLOGICAL CHARACTERISTICS OF SEAGRASS ECOSYSTEMS

    EPA Science Inventory

    The development of seagrass patches and subsequently, the landscape that they define, is typically thought to be dependent on the phenotypic response of seagrass to environmental factors such as light/nutrients (Dennison et al. 1993), sedimentation (Harlin and Thorne-Miller 1981)...

  12. ENUMERATION, ISOLATION, AND CHARACTERIZATION OF ACETOGENIC BACTERIA ASSOCIATED WITH SEAGRASS ROOTS (POSTER SESSION)

    EPA Science Inventory

    Seagrasses are rooted in anoxic, sulfate-reducing sediments. However, the seagrass root is oxygenated during the daytime, becoming anoxic at night. Root thin sections hydridized with 33P-labeled probes revealed the presence of acetogenic and sulfate-reducing bacteria in the rhizo...

  13. ENUMERATION, ISOLATION, AND CHARACTERIZATION OF ACETOGENIC BACTERIA ASSOCIATED WITH SEAGRASS ROOTS

    EPA Science Inventory

    Seagrasses are rooted in anoxic, sulfate-reducing sediments. However, the seagrass root is oxygenated during the daytime, becoming anoxic at night. Root thin sections hydridized with 33P-labeled probes revealed the presence of acetogenic and sulfate-reducing bacteria in the rhizo...

  14. RELATIONSHIPS BETWEEN SEAGRASSES, BENTHIC MACROALGAE AND NUTRIENTS IN A PACIFIC NORTHWEST ESTUARY

    EPA Science Inventory

    Pacific Northwest estuaries are characterized by large tidal ranges (2-3 m) that routinely expose submerged aquatic vegetation (SAV) such as seagrass and benthic macroalgae. The dominant native seagrass in PNW estuaries is the eelgrass Zostera marina. However, in recent decades...

  15. Development of threshold values for a seagrass epiphyte indicator of nutrient enrichment in coastal systems.

    EPA Science Inventory

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experim...

  16. Seagrass Epiphytes as a Nutrient Stressor Indicator: Towards Development of Threshold Values

    EPA Science Inventory

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experim...

  17. Development of threshold values for a seagrass epiphyte indicator of nutrient enrichment in coastal systems.

    EPA Science Inventory

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experim...

  18. A Monte Carlo study of the seagrass-induced depth bias in bathymetric lidar.

    PubMed

    Wang, Chi-Kuei; Philpot, William; Kim, Minsu; Lei, Hou-Meng

    2011-04-11

    A bathymetric lidar survey is the most cost efficient method of producing bathymetric maps in near shore areas where the ocean bottom is both highly variable and of greatest importance for shipping and recreation. So far, not much attention has been paid to the influence of bottom materials on the lidar signals. This study addresses this issue using a Monte Carlo modeling technique. The Monte Carlo simulation includes a plane parallel water body and a flat bottom with or without seagrass. The seagrass canopy structure is adopted from Zimmerman (2003). Both the surface of the seagrass leaves and the bottom are assumed to be Lambertian. Convolution with the lidar pulse function followed by the median operator is used to reduce the variance of the resultant lidar waveform. Two seagrass orientation arrangements are modeled: seagrass in still water with random leaf orientation and seagrass with a uniform orientation as would be expected when under the influence of a water current. For each case, two maximum canopy heights, 0.5 m and 1 m, three shoot densities, 100, 500, and 1000, and three bending angles, 5, 25, and 45 degrees, are considered. The seagrass is found to induce a depth bias that is proportional to an effective leaf area index (eLAI) and the contrast in reflectance between the seagrass and the bottom material.

  19. Faunal communities and habitat characteristics of the Big Bend seagrass meadows, 2009-2010.

    EPA Science Inventory

    Seagrass meadows are important habitats that serve as nursery, feeding, and sheltering grounds for many marine species. In addition to the ecosystem functions and services they provide, seagrass habitats and associated fauna are commonly observed to have naturally high levels of...

  20. USE OF WAVE EXPOSURE TECHNIQUE FOR PREDICTING DISTRIBUTION AND ECOLOGICAL CHARACTERISTICS OF SEAGRASS ECOSYSTEMS

    EPA Science Inventory

    The development of seagrass patches and subsequently, the landscape that they define, is typically thought to be dependent on the phenotypic response of seagrass to environmental factors such as light/nutrients (Dennison et al. 1993), sedimentation (Harlin and Thorne-Miller 1981)...

  1. Learning about Coastal Trends: What Is the Story with Seagrass... and How Does It Affect Me?

    ERIC Educational Resources Information Center

    Ksiazek, Kelly; McGlathery, Karen; Reynolds, Laura; Schwarzschild, Arthur; Wilkerson, Carissa; Carruthers, Tim; Gurbisz, Cassie; Woerner, Joanna L.; Murray, Laura

    2009-01-01

    Flowering plants that live underwater in marine and estuarine habitats (seagrasses) are important because they support human food sources, such as crabs and fish, as well as endangered animals, such as turtles and manatees. Seagrasses are now known to be declining globally, largely as a result of increasing pressure from human populations living…

  2. Faunal communities and habitat characteristics of the Big Bend seagrass meadows, 2009-2010.

    EPA Science Inventory

    Seagrass meadows are important habitats that serve as nursery, feeding, and sheltering grounds for many marine species. In addition to the ecosystem functions and services they provide, seagrass habitats and associated fauna are commonly observed to have naturally high levels of...

  3. RELATIONSHIPS BETWEEN SEAGRASSES, BENTHIC MACROALGAE AND NUTRIENTS IN A PACIFIC NORTHWEST ESTUARY

    EPA Science Inventory

    Pacific Northwest estuaries are characterized by large tidal ranges (2-3 m) that routinely expose submerged aquatic vegetation (SAV) such as seagrass and benthic macroalgae. The dominant native seagrass in PNW estuaries is the eelgrass Zostera marina. However, in recent decades...

  4. Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

    PubMed Central

    Macreadie, Peter I.; Trevathan-Tackett, Stacey M.; Skilbeck, Charles G.; Sanderman, Jonathan; Curlevski, Nathalie; Jacobsen, Geraldine; Seymour, Justin R.

    2015-01-01

    Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences. PMID:26490788

  5. SEAGRASS EPIPHYTES AS A NUTRIENT STRESSOR INDICATOR: APPROACHES TOWARDS DEVELOPMENT OF THRESHOLD VALUES.

    EPA Science Inventory

    Epiphytes on seagrasses have been studied for more than 50 years, and proposed as an indicator of anthropogenic nutrient enrichment for over 30 years. Epiphytes have been correlated with seagrass declines, causally related to nutrient additions in both field and mesocosm experim...

  6. The use of Sentinel-2 imagery for seagrass mapping: Kalloni Gulf (Lesvos Island, Greece) case study

    NASA Astrophysics Data System (ADS)

    Topouzelis, Konstantinos; Charalampis Spondylidis, Spyridon; Papakonstantinou, Apostolos; Soulakellis, Nikolaos

    2016-08-01

    Seagrass meadows play a significant role in ecosystems by stabilizing sediment and improving water clarity, which enhances seagrass growing conditions. It is high on the priority of EU legislation to map and protect them. The traditional use of medium spatial resolution satellite imagery e.g. Landsat-8 (30m) is very useful for mapping seagrass meadows on a regional scale. However, the availability of Sentinel-2 data, the recent ESA's satellite with its payload Multi-Spectral Instrument (MSI) is expected to improve the mapping accuracy. MSI designed to improve coastline studies due to its enhanced spatial and spectral capabilities e.g. optical bands with 10m spatial resolution. The present work examines the quality of Sentinel-2 images for seagrass mapping, the ability of each band in detection and discrimination of different habitats and estimates the accuracy of seagrass mapping. After pre-processing steps, e.g. radiometric calibration and atmospheric correction, image classified into four classes. Classification classes included sub-bottom composition e.g. seagrass, soft bottom, and hard bottom. Concrete vectors describing the areas covered by seagrass extracted from the high-resolution satellite image and used as in situ measurements. The developed methodology applied in the Gulf of Kalloni, (Lesvos Island - Greece). Results showed that Sentinel-2 images can be robustly used for seagrass mapping due to their spatial resolution, band availability and radiometric accuracy.

  7. ENUMERATION, ISOLATION, AND CHARACTERIZATION OF ACETOGENIC BACTERIA ASSOCIATED WITH SEAGRASS ROOTS (POSTER SESSION)

    EPA Science Inventory

    Seagrasses are rooted in anoxic, sulfate-reducing sediments. However, the seagrass root is oxygenated during the daytime, becoming anoxic at night. Root thin sections hydridized with 33P-labeled probes revealed the presence of acetogenic and sulfate-reducing bacteria in the rhizo...

  8. ENUMERATION, ISOLATION, AND CHARACTERIZATION OF ACETOGENIC BACTERIA ASSOCIATED WITH SEAGRASS ROOTS

    EPA Science Inventory

    Seagrasses are rooted in anoxic, sulfate-reducing sediments. However, the seagrass root is oxygenated during the daytime, becoming anoxic at night. Root thin sections hydridized with 33P-labeled probes revealed the presence of acetogenic and sulfate-reducing bacteria in the rhizo...

  9. Predicting habitat distribution to conserve seagrass threatened by sea level rise

    NASA Astrophysics Data System (ADS)

    Saunders, M. I.; Baldock, T.; Brown, C. J.; Callaghan, D. P.; Golshani, A.; Hamylton, S.; Hoegh-guldberg, O.; Leon, J. X.; Lovelock, C. E.; Lyons, M. B.; O'Brien, K.; Mumby, P.; Phinn, S. R.; Roelfsema, C. M.

    2013-12-01

    Sea level rise (SLR) over the 21st century will cause significant redistribution of valuable coastal habitats. Seagrasses form extensive and highly productive meadows in shallow coastal seas support high biodiversity, including economically valuable and threatened species. Predictive habitat models can inform local management actions that will be required to conserve seagrass faced with multiple stressors. We developed novel modelling approaches, based on extensive field data sets, to examine the effects of sea level rise and other stressors on two representative seagrass habitats in Australia. First, we modelled interactive effects of SLR, water clarity and adjacent land use on estuarine seagrass meadows in Moreton Bay, Southeast Queensland. The extent of suitable seagrass habitat was predicted to decline by 17% by 2100 due to SLR alone, but losses were predicted to be significantly reduced through improvements in water quality (Fig 1a) and by allowing space for seagrass migration with inundation. The rate of sedimentation in seagrass strongly affected the area of suitable habitat for seagrass in sea level rise scenarios (Fig 1b). Further research to understand spatial, temporal and environmental variability of sediment accretion in seagrass is required. Second, we modelled changes in wave energy distribution due to predicted SLR in a linked coral reef and seagrass ecosystem at Lizard Island, Great Barrier Reef. Scenarios where the water depth over the coral reef deepened due to SLR and minimal reef accretion, resulted in larger waves propagating shoreward, changing the existing hydrodynamic conditions sufficiently to reduce area of suitable habitat for seagrass. In a scenario where accretion of the coral reef was severely compromised (e.g. warming, acidification, overfishing), the probability of the presence of seagrass declined significantly. Management to maintain coral health will therefore also benefit seagrasses subject to SLR in reef environments. Further

  10. Seagrass ecosystems reduce exposure to bacterial pathogens of humans, fishes, and invertebrates.

    PubMed

    Lamb, Joleah B; van de Water, Jeroen A J M; Bourne, David G; Altier, Craig; Hein, Margaux Y; Fiorenza, Evan A; Abu, Nur; Jompa, Jamaluddin; Harvell, C Drew

    2017-02-17

    Plants are important in urban environments for removing pathogens and improving water quality. Seagrass meadows are the most widespread coastal ecosystem on the planet. Although these plants are known to be associated with natural biocide production, they have not been evaluated for their ability to remove microbiological contamination. Using amplicon sequencing of the 16S ribosomal RNA gene, we found that when seagrass meadows are present, there was a 50% reduction in the relative abundance of potential bacterial pathogens capable of causing disease in humans and marine organisms. Moreover, field surveys of more than 8000 reef-building corals located adjacent to seagrass meadows showed twofold reductions in disease levels compared to corals at paired sites without adjacent seagrass meadows. These results highlight the importance of seagrass ecosystems to the health of humans and other organisms.

  11. Seagrass importance for a small-scale fishery in the tropics: the need for seascape management.

    PubMed

    de la Torre-Castro, Maricela; Di Carlo, Giuseppe; Jiddawi, Narriman S

    2014-06-30

    Small-scale fisheries (SSF) in tropical seascapes (mosaics of interconnected mangroves, seagrasses and corals) are crucial for food and income. However, management is directed mostly to corals and mangroves. This research analyzes the importance of seagrasses compared to adjacent ecosystems in Chwaka Bay, Zanzibar, Tanzania. Using fish landings; the study investigated: location of fishing effort, fish production (biomass and species), and monetary benefits (aggregated value and per capita income). Seagrasses were the most visited grounds providing highest community benefits. Per capita benefits were equivalent to those from corals and mangroves. All three habitats provided income just above extreme poverty levels; however catches from seagrass appeared more stable. Seagrass are key ecosystems supporting SSF and protection and management are urgently needed. Adoption of a seascape approach considering all ecosystems underpinning SSF and the social aspects of fishing and a shift in emphasis from pure conservation to sustainable resource management would be desirable.

  12. Abstraction and Consolidation

    ERIC Educational Resources Information Center

    Monaghan, John; Ozmantar, Mehmet Fatih

    2004-01-01

    What is involved in consolidating a new mathematical abstraction? This paper examines the work of one student who was working on a task designed to consolidate two recently constructed absolute function abstractions. The study adopts an activity theoretic model of abstraction in context. Selected protocol data are presented. The initial state of…

  13. Abstraction and Consolidation

    ERIC Educational Resources Information Center

    Monaghan, John; Ozmantar, Mehmet Fatih

    2006-01-01

    The framework for this paper is a recently developed theory of abstraction in context. The paper reports on data collected from one student working on tasks concerned with absolute value functions. It examines the relationship between mathematical constructions and abstractions. It argues that an abstraction is a consolidated construction that can…

  14. Quality of Abstracts.

    ERIC Educational Resources Information Center

    Tenopir, Carol; Jacso, Peter

    1993-01-01

    Reviews the factors to be considered in evaluating abstracts. Types of abstracts, content, length, writing style, comprehensive criteria for abstracts, readability, readability testing, compatibility with ANSI (American National Standards Institute) standards, and informativeness are among the topics covered. (12 references) (KRN)

  15. Abstraction and Consolidation

    ERIC Educational Resources Information Center

    Monaghan, John; Ozmantar, Mehmet Fatih

    2006-01-01

    The framework for this paper is a recently developed theory of abstraction in context. The paper reports on data collected from one student working on tasks concerned with absolute value functions. It examines the relationship between mathematical constructions and abstractions. It argues that an abstraction is a consolidated construction that can…

  16. Seagrass-Watch: Engaging Torres Strait Islanders in marine habitat monitoring

    NASA Astrophysics Data System (ADS)

    Mellors, Jane E.; McKenzie, Len J.; Coles, Robert G.

    2008-09-01

    Involvement in scientifically structured habitat monitoring is a relatively new concept to the peoples of Torres Strait. The approach we used was to focus on awareness, and to build the capacity of groups to participate using Seagrass-Watch as the vehicle to provide education and training in monitoring marine ecosystems. The project successfully delivered quality scientifically rigorous baseline information on the seasonality of seagrasses in the Torres Strait—a first for this region. Eight seagrass species were identified across the monitoring sites. Seagrass cover varied within and between years. Preliminary evidence indicated that drivers for seagrass variability were climate related. Generally, seagrass abundance increased during the north-west monsoon ( Kuki), possibly a consequence of elevated nutrients, lower tidal exposure times, less wind, and higher air temperatures. Low seagrass abundance coincided with the presence of greater winds and longer periods of exposure at low tides during the south-east trade wind season ( Sager). No seasonal patterns were apparent when frequency of disturbance from high sedimentation and human impacts was high. Seagrass-Watch has been incorporated in to the Thursday Island High School's Marine Studies Unit ensuring continuity of monitoring. The students, teachers, and other interested individuals involved in Seagrass-Watch have mastered the necessary scientific procedures to monitor seagrass meadows, and developed skills in coordinating a monitoring program and skills in mentoring younger students. This has increased the participants' self-esteem and confidence, and given them an insight into how they may participate in the future management of their sea country.

  17. Quantitative estimate of commercial fish enhancement by seagrass habitat in southern Australia

    NASA Astrophysics Data System (ADS)

    Blandon, Abigayil; zu Ermgassen, Philine S. E.

    2014-03-01

    Seagrass provides many ecosystem services that are of considerable value to humans, including the provision of nursery habitat for commercial fish stock. Yet few studies have sought to quantify these benefits. As seagrass habitat continues to suffer a high rate of loss globally and with the growing emphasis on compensatory restoration, valuation of the ecosystem services associated with seagrass habitat is increasingly important. We undertook a meta-analysis of juvenile fish abundance at seagrass and control sites to derive a quantitative estimate of the enhancement of juvenile fish by seagrass habitats in southern Australia. Thirteen fish of commercial importance were identified as being recruitment enhanced in seagrass habitat, twelve of which were associated with sufficient life history data to allow for estimation of total biomass enhancement. We applied von Bertalanffy growth models and species-specific mortality rates to the determined values of juvenile enhancement to estimate the contribution of seagrass to commercial fish biomass. The identified species were enhanced in seagrass by 0.98 kg m-2 y-1, equivalent to ˜$A230,000 ha-1 y-1. These values represent the stock enhancement where all fish species are present, as opposed to realized catches. Having accounted for the time lag between fish recruiting to a seagrass site and entering the fishery and for a 3% annual discount rate, we find that seagrass restoration efforts costing $A10,000 ha-1 have a potential payback time of less than five years, and that restoration costing $A629,000 ha-1 can be justified on the basis of enhanced commercial fish recruitment where these twelve fish species are present.

  18. Seasonal composition and activity of sulfate-reducing prokaryotic communities in seagrass bed sediments

    EPA Science Inventory

    Sulfate-reducing prokaryotes (SRP) play a key role in the carbon and nutrient cycles of coastal marine, vegetated ecosystems, but the interactions of SRP communities with aquatic plants remain little studied. The abundance, activity, and community composition of SRP was studied i...

  19. Seasonal composition and activity of sulfate-reducing prokaryotic communities in seagrass bed sediments

    EPA Science Inventory

    Sulfate-reducing prokaryotes (SRP) play a key role in the carbon and nutrient cycles of coastal marine, vegetated ecosystems, but the interactions of SRP communities with aquatic plants remain little studied. The abundance, activity, and community composition of SRP was studied i...

  20. Abstraction and Problem Reformulation

    NASA Technical Reports Server (NTRS)

    Giunchiglia, Fausto

    1992-01-01

    In work done jointly with Toby Walsh, the author has provided a sound theoretical foundation to the process of reasoning with abstraction (GW90c, GWS9, GW9Ob, GW90a). The notion of abstraction formalized in this work can be informally described as: (property 1), the process of mapping a representation of a problem, called (following historical convention (Sac74)) the 'ground' representation, onto a new representation, called the 'abstract' representation, which, (property 2) helps deal with the problem in the original search space by preserving certain desirable properties and (property 3) is simpler to handle as it is constructed from the ground representation by "throwing away details". One desirable property preserved by an abstraction is provability; often there is a relationship between provability in the ground representation and provability in the abstract representation. Another can be deduction or, possibly inconsistency. By 'throwing away details' we usually mean that the problem is described in a language with a smaller search space (for instance a propositional language or a language without variables) in which formulae of the abstract representation are obtained from the formulae of the ground representation by the use of some terminating rewriting technique. Often we require that the use of abstraction results in more efficient .reasoning. However, it might simply increase the number of facts asserted (eg. by allowing, in practice, the exploration of deeper search spaces or by implementing some form of learning). Among all abstractions, three very important classes have been identified. They relate the set of facts provable in the ground space to those provable in the abstract space. We call: TI abstractions all those abstractions where the abstractions of all the provable facts of the ground space are provable in the abstract space; TD abstractions all those abstractions wllere the 'unabstractions' of all the provable facts of the abstract space are

  1. Abstraction in mathematics.

    PubMed Central

    Ferrari, Pier Luigi

    2003-01-01

    Some current interpretations of abstraction in mathematical settings are examined from different perspectives, including history and learning. It is argued that abstraction is a complex concept and that it cannot be reduced to generalization or decontextualization only. In particular, the links between abstraction processes and the emergence of new objects are shown. The role that representations have in abstraction is discussed, taking into account both the historical and the educational perspectives. As languages play a major role in mathematics, some ideas from functional linguistics are applied to explain to what extent mathematical notations are to be considered abstract. Finally, abstraction is examined from the perspective of mathematics education, to show that the teaching ideas resulting from one-dimensional interpretations of abstraction have proved utterly unsuccessful. PMID:12903658

  2. A comparative analysis of benthic nematode assemblages from Zostera noltii beds before and after a major vegetation collapse

    NASA Astrophysics Data System (ADS)

    Materatski, Patrick; Vafeiadou, Anna-Maria; Ribeiro, Rui; Moens, Tom; Adão, Helena

    2015-12-01

    Benthic nematodes are widely regarded as very suitable organisms to monitor potential ecological effects of natural and anthropogenic disturbances in aquatic ecosystems. During 2008, the seagrass beds of Zostera noltii located in the Mira estuary (SW Portugal) disappeared completely. However, during 2009, slight symptoms of natural recovery were observed, a process which has since evolved intermittently. This study aims to investigate changes in patterns of nematode density, diversity, and trophic composition between two distinct habitat conditions: "before" the collapse of seagrass beds, and during the early recovery "after" the seagrass habitat loss, through the analysis of: i) temporal and spatial distribution patterns of nematode communities, and ii) the most important environmental variables influencing the nematode assemblages. The following hypotheses were tested: i) there would be differences in nematode assemblage density, biodiversity and trophic composition during both ecological conditions, "before" and "after"; and ii) there would be differences in nematode assemblage density, biodiversity and trophic composition at different sampling occasions during both ecological conditions. Nematode density and diversity were significantly different between the two ecological situations. A higher density was recorded before, but a higher diversity was evident after the collapse of Z. noltii. In spite of the disturbance caused by the seagrass habitat loss in the Mira estuary, the nematode trophic composition did not significantly differ between the before and after seagrass collapse situations. Despite the significant differences found among sampling occasions, a consistent temporal pattern was not evident. The response of nematode communities following this extreme event exhibited considerable resistance and resilience to the new environmental conditions.

  3. Monitoring coral reefs, seagrasses and mangroves in Costa Rica (CARICOMP).

    PubMed

    Cortés, Jorge; Fonseca, Ana C; Nivia-Ruiz, Jaime; Nielsen-Muñoz, Vanessa; Samper-Villarreal, Jimena; Salas, Eva; Martínez, Solciré; Zamora-Trejos, Priscilla

    2010-10-01

    The coral reefs, seagrasses and mangroves from the Costa Rican Caribbean coast have been monitored since 1999 using the CARICOMP protocol. Live coral cover at Meager Shoal reef bank (7 to 10 m depth) at the Parque Nacional Cahuita (National Park), increased from 13.3% in 1999, to 28.2% in 2003, but decreased during the next 5 years to around 17.5%. Algal cover increased significantly since 2003 from 36.6% to 61.3% in 2008. The density of Diadema antillarum oscillated between 2 and 7ind/m2, while Echinometra viridis decreased significantly from 20 to 0.6ind/m2. Compared to other CARICOMP sites, live coral cover, fish diversity and density, and sea urchin density were low, and algal cover was intermediate. The seagrass site, also in the Parque Nacional Cahuita, is dominated by Thalassia testudinum and showed an intermediate productivity (2.7 +/- 1.15 g/m2/d) and biomass (822.8 +/- 391.84 g/m2) compared to other CARICOMP sites. Coral reefs and seagrasses at the Parque Nacional Cahuita continue to be impacted by high sediment loads from terrestrial origin. The mangrove forest at Gandoca, within the Refugio Nacional de Vida Silvestre Gandoca-Manzanillo (National Wildlife Refuge), surrounds a lagoon and it is dominated by the red mangrove, Rhizophora mangle. Productivity and flower production peak was in July. Biomass (14 kg/m2) and density (9.0 +/- 0.58 trees/100 m2) in Gandoca were relatively low compared to other CARICOMP sites, while productivity in July in Costa Rica (4 g/m2/d) was intermediate, similar to most CARICOMP sites. This mangrove is expanding and has low human impact thus far. Management actions should be taken to protect and preserve these important coastal ecosystems.

  4. Food supply depends on seagrass meadows in the coral triangle

    NASA Astrophysics Data System (ADS)

    Unsworth, Richard K. F.; Hinder, Stephanie L.; Bodger, Owen G.; Cullen-Unsworth, Leanne C.

    2014-09-01

    The tropical seascape provides food and livelihoods to hundreds of millions of people, but the support of key habitats to this supply remains ill appreciated. For fisheries and conservation management actions to help promote resilient ecosystems, sustainable livelihoods, and food supply, knowledge is required about the habitats that help support fisheries productivity and the consequences of this for food security. This paper provides an interdisciplinary case study from the coral triangle of how seagrass meadows provide support for fisheries and local food security. We apply a triangulated approach that utilizes ecological, fisheries and market data combined with over 250 household interviews. Our research demonstrates that seagrass associated fauna in a coral triangle marine protected area support local food supply contributing at least 50% of the fish based food. This formed between 54% and 99% of daily protein intake in the area. Fishery catch was found to significantly vary with respect to village (p < 0.01) with habitat configuration a probable driver. Juvenile fish comprised 26% of the fishery catch and gear type significantly influenced this proportion (<0.05). Limited sustainability of fishery practices (high juvenile catch and a 51% decline in CPUE for the biggest fishery) and poor habitat management mean the security of this food supply has the potential to be undermined in the long-term. Findings of this study have implications for the management and assessment of fisheries throughout the tropical seascape. Our study provides an exemplar for why natural resource management should move beyond biodiversity and consider how conservation and local food security are interlinked processes that are not mutually exclusive. Seagrass meadows are under sustained threat worldwide, this study provides evidence of the need to conserve these not just to protect biodiversity but to protect food security.

  5. Packed Bed Reactor Experiment

    NASA Image and Video Library

    The purpose of the Packed Bed Reactor Experiment in low gravity is to determine how a mixture of gas and liquid flows through a packed bed in reduced gravity. A packed bed consists of a metal pipe ...

  6. Retrieval of abstract semantics.

    PubMed

    Noppeney, Uta; Price, Cathy J

    2004-05-01

    Behavioural and neuropsychological evidence suggests that abstract and concrete concepts might be represented, retrieved and processed differently in the human brain. Using fMRI, we demonstrate that retrieval of abstract relative to sensory-based semantics during synonym judgements increased activation in a left frontotemporal system that has been associated with semantic processing particularly at the sentence level. Since activation increases were observed irrespective of the degree of difficulty, we suggest that these differential activations might reflect a particular retrieval mechanism or strategy for abstract concepts. In contrast to sensory-based semantics, the meaning of abstract concepts is largely specified by their usage in language rather than by their relations to the physical world. Subjects might therefore generate an appropriate semantic sentential context to fully explore and specify the meaning of abstract concepts. Our results also explain why abstract semantics is vulnerable to left frontotemporal lesions.

  7. Abstract and keywords.

    PubMed

    Peh, W C G; Ng, K H

    2008-09-01

    The abstract of a scientific paper represents a concise, accurate and factual mini-version of the paper contents. Abstract format may vary according to the individual journal. For original articles, a structured abstract usually consists of the following headings: aims (or objectives), materials and methods, results and conclusion. A few keywords that capture the main topics of the paper help indexing in the medical literature.

  8. Partitioning loss rates of early juvenile blue crabs from seagrass habitats into mortality and emigration

    USGS Publications Warehouse

    Etherington, L.L.; Eggleston, D.B.; Stockhausen, W.T.

    2003-01-01

    in which crab loss from seagrass due to mortality was greater than losses due to emigration was not significantly different from 50%. Thus, mortality and emigration appear to contribute equally to juvenile loss in seagrass habitats. The difference in magnitude (absolute amount of loss) between mean emigration and mean mortality varied between size classes, such that differences between emigration and mortality were relatively small for J1-J2 crabs, but much larger for J3-J5 crabs. Further, mortality rates were density-dependent for J3-J5 juvenile stages but not for J1-J2 crabs, whereas emigration was inversely density-dependent among J3-J5 stages but not for J1-J2 instars. The co-dependency of mortality and emigration suggests that the loss term (emigration or mortality) which has the relatively stronger contribution to total loss may dictate the patterns of loss under different conditions. For older juveniles (J3-J5), emigration may only have a large impact on juvenile loss where densities are low, since the contribution of mortality appears to be much greater than emigration at high densities. The size-specific pattern of density-dependent mortality supports the notion of an ontogenetic habitat shift by early juvenile blue crabs from seagrass to unvegetated habitats, since larger individuals may experience increased mortality at high densities within seagrass beds. Qualitative comparisons between this study and a concurrent study of planktonic emigration of J1-J5 blue crabs (Blackmon and Eggleston, 2001) suggests that benthic emigration among J1-J2 blue crabs was greater than planktonic emigration; for J3-J5 stages benthic and planktonic emigration were nearly equal. This study demonstrates the potentially large role of emigration in recruitment processes and patterns of early juvenile blue crabs, and illustrates how juvenile size, juvenile density, and time of day can affect mortality and emigration rates as well as total loss and colonization. The components of

  9. Abstracts--Citations

    ERIC Educational Resources Information Center

    Occupational Mental Health, 1972

    1972-01-01

    Provides abstracts and citations of journal articles and reports dealing with aspects of mental health. Topics include absenteeism, alcoholism, drug abuse, leisure, disadvantaged, job satisfaction, and others. (SB)

  10. Acute and additive toxicity of ten photosystem-II herbicides to seagrass

    NASA Astrophysics Data System (ADS)

    Wilkinson, Adam D.; Collier, Catherine J.; Flores, Florita; Negri, Andrew P.

    2015-11-01

    Photosystem II herbicides are transported to inshore marine waters, including those of the Great Barrier Reef, and are usually detected in complex mixtures. These herbicides inhibit photosynthesis, which can deplete energy reserves and reduce growth in seagrass, but the toxicity of some of these herbicides to seagrass is unknown and combined effects of multiple herbicides on seagrass has not been tested. Here we assessed the acute phytotoxicity of 10 PSII herbicides to the seagrass Halophila ovalis over 24 and/or 48 h. Individual herbicides exhibited a broad range of toxicities with inhibition of photosynthetic activity (∆F/Fm‧) by 50% at concentrations ranging from 3.5 μg l-1 (ametryn) to 132 μg l-1 (fluometuron). We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides. The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses. This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/Fm‧.

  11. Community structure of caprellids (Crustacea: Amphipoda: Caprellidae) on seagrasses from southern Spain

    NASA Astrophysics Data System (ADS)

    González, A. R.; Guerra-García, J. M.; Maestre, M. J.; Ruiz-Tabares, A.; Espinosa, F.; Gordillo, I.; Sánchez-Moyano, J. E.; García-Gómez, J. C.

    2008-09-01

    The community structure of caprellids inhabiting two species of seagrass ( Cymodocea nodosa and Zostera marina) was investigated on the Andalusian coast, southern Spain, using uni and multivariate analyses. Three meadows were selected (Almería, AL; Málaga, MA; Cádiz, CA), and changes in seagrass cover and biomass were measured from 2004 to 2005. Four caprellid species were found; the density of Caprella acanthifera, Phtisica marina and Pseudoprotella phasma was correlated to seagrass biomass. No such correlation was found for Pariambus typicus, probably because this species inhabits sediments and does not cling to the seagrass leaves. We recorded a significant decrease in seagrass cover and biomass in MA due to illegal bottom trawling fisheries. Phtisica marina and P. typicus were favoured by this perturbation and increased their densities after the trawling activities. A survey of reports on caprellids in seagrass meadows around the world showed no clear latitudinal patterns in caprellid densities (ranging from 6 to 1,000 ind/m2 per meadow) and species diversity. While caprellid abundances in seagrass meadows are often very high, the number of species per meadow is low (range 1-5).

  12. Acute and additive toxicity of ten photosystem-II herbicides to seagrass.

    PubMed

    Wilkinson, Adam D; Collier, Catherine J; Flores, Florita; Negri, Andrew P

    2015-11-30

    Photosystem II herbicides are transported to inshore marine waters, including those of the Great Barrier Reef, and are usually detected in complex mixtures. These herbicides inhibit photosynthesis, which can deplete energy reserves and reduce growth in seagrass, but the toxicity of some of these herbicides to seagrass is unknown and combined effects of multiple herbicides on seagrass has not been tested. Here we assessed the acute phytotoxicity of 10 PSII herbicides to the seagrass Halophila ovalis over 24 and/or 48 h. Individual herbicides exhibited a broad range of toxicities with inhibition of photosynthetic activity (∆F/F(m)') by 50% at concentrations ranging from 3.5 μg l(-1) (ametryn) to 132 μg l(-1) (fluometuron). We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides. The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses. This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/F(m)'.

  13. Stability and resilience of seagrass meadows to seasonal and interannual dynamics and environmental stress

    NASA Astrophysics Data System (ADS)

    Carr, Joel A.; D'Odorico, Paolo; McGlathery, Karen J.; Wiberg, Patricia L.

    2012-03-01

    Shallow coastal bays provide habitat for diverse fish and invertebrate populations and are an important source of sediment for surrounding marshes. The sediment dynamics of these bays are strongly affected by seagrass meadows, which limit sediment resuspension, thereby providing a more favorable light environment for their own survival and growth. Due to this positive feedback between seagrass and light conditions, it has been suggested that bare sediment and seagrass meadows are potential alternate stable states of the benthos in shallow coastal bays. To investigate the stability and resilience of seagrass meadows subjected to variation in environmental conditions (e.g., light, temperature), a coupled model of vegetation-sediment-water flow interactions and vegetation growth was developed. The model was used to examine the effect of dynamically varying seasonal and interannual seagrass density on sediment resuspension, water column turbidity, and the subsequent light environment on hourly time steps and then run over decadal time scales. A daily growth model was designed to capture both belowground biomass and the growth and senescence of aboveground biomass structural components (e.g., leaves and stems). This allowed us to investigate how the annual and seasonal variability in shoot and leaf density within a meadow affects the strength of positive feedbacks between seagrass and their light environment. The model demonstrates both the emergence of bistable behavior from 1.6 to 1.8 m mean sea level due to the strength of the positive feedback, as well as the limited resilience of seagrass meadows within this bistable range.

  14. Impact of pond aquaculture effluents on seagrass performance in NE Hainan, tropical China.

    PubMed

    Herbeck, Lucia S; Sollich, Miriam; Unger, Daniela; Holmer, Marianne; Jennerjahn, Tim C

    2014-08-15

    The impact of pond aquaculture effluents on the distribution and performance of seagrasses was examined in NE Hainan, tropical China. Samples were taken along transects in three back-reef areas with different extent of aquaculture production in their hinterland. High δ(15)N in seagrass leaves and epiphytes (6-9‰) similar to values in pond effluents documented aquaculture as dominant nitrogen source in the back-reefs with decreasing impact with distance from shore. Seagrass species abundance, shoot density and biomass were lower and concentrations of nutrients, chlorophyll and suspended matter were higher at nearshore sites with high and moderate pond abundance than at the control site. High epiphyte loads and low δ(34)S in seagrass leaves suggest temporal shading and sulphide poisoning of the nearshore seagrasses. Observed gradients in environmental parameters and seagrass performance indicate that the distance from the pond outlets and size of the adjacent pond agglomeration are major determinants of seagrass degradation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Acute and additive toxicity of ten photosystem-II herbicides to seagrass

    PubMed Central

    Wilkinson, Adam D.; Collier, Catherine J.; Flores, Florita; Negri, Andrew P.

    2015-01-01

    Photosystem II herbicides are transported to inshore marine waters, including those of the Great Barrier Reef, and are usually detected in complex mixtures. These herbicides inhibit photosynthesis, which can deplete energy reserves and reduce growth in seagrass, but the toxicity of some of these herbicides to seagrass is unknown and combined effects of multiple herbicides on seagrass has not been tested. Here we assessed the acute phytotoxicity of 10 PSII herbicides to the seagrass Halophila ovalis over 24 and/or 48 h. Individual herbicides exhibited a broad range of toxicities with inhibition of photosynthetic activity (∆F/Fm′) by 50% at concentrations ranging from 3.5 μg l−1 (ametryn) to 132 μg l−1 (fluometuron). We assessed potential additivity using the Concentration Addition model of joint action for binary mixtures of diuron and atrazine as well as complex mixtures of all 10 herbicides. The effects of both mixture types were largely additive, validating the application of additive effects models for calculating the risk posed by multiple PSII herbicides to seagrasses. This study extends seagrass ecotoxicological data to ametryn, metribuzin, bromacil, prometryn and fluometuron and demonstrates that low concentrations of PSII herbicide mixtures have the potential to impact ecologically relevant endpoints in seagrass, including ∆F/Fm′. PMID:26616444

  16. Solar radiation and tidal exposure as environmental drivers of Enhalus acoroides dominated seagrass meadows.

    PubMed

    Unsworth, Richard K F; Rasheed, Michael A; Chartrand, Kathryn M; Roelofs, Anthony J

    2012-01-01

    There is strong evidence of a global long-term decline in seagrass meadows that is widely attributed to anthropogenic activity. Yet in many regions, attributing these changes to actual activities is difficult, as there exists limited understanding of the natural processes that can influence these valuable ecosystem service providers. Being able to separate natural from anthropogenic causes of seagrass change is important for developing strategies that effectively mitigate and manage anthropogenic impacts on seagrass, and promote coastal ecosystems resilient to future environmental change. The present study investigated the influence of environmental and climate related factors on seagrass biomass in a large ≈250 ha meadow in tropical north east Australia. Annual monitoring of the intertidal Enhalus acoroides (L.f.) Royle seagrass meadow over eleven years revealed a declining trend in above-ground biomass (54% significant overall reduction from 2000 to 2010). Partial Least Squares Regression found this reduction to be significantly and negatively correlated with tidal exposure, and significantly and negatively correlated with the amount of solar radiation. This study documents how natural long-term tidal variability can influence long-term seagrass dynamics. Exposure to desiccation, high UV, and daytime temperature regimes are discussed as the likely mechanisms for the action of these factors in causing this decline. The results emphasise the importance of understanding and assessing natural environmentally-driven change when interpreting the results of seagrass monitoring programs.

  17. Unexpectedly high degree of anammox and DNRA in seagrass sediments: Description and application of a revised isotope pairing technique

    NASA Astrophysics Data System (ADS)

    Salk, Kateri R.; Erler, Dirk V.; Eyre, Bradley D.; Carlson-Perret, Natasha; Ostrom, Nathaniel E.

    2017-08-01

    Understanding the magnitude of nitrogen (N) loss and recycling pathways is crucial for coastal N management efforts. However, quantification of denitrification and anammox by a widely-used method, the isotope pairing technique, is challenged when dissimilatory NO3- reduction to NH4+ (DNRA) occurs. In this study, we describe a revised isotope pairing technique that accounts for the influence of DNRA on NO3- reduction (R-IPT-DNRA). The new calculation procedure improves on previous techniques by (1) accounting for N2O production, (2) distinguishing canonical anammox from coupled DNRA-anammox, and (3) including the production of 30N2 by anammox in the quantification of DNRA. This approach avoids the potential for substantial underestimates of anammox rates and overestimates of denitrification rates in systems where DNRA is a significant NO3- reduction pathway. We apply this technique to simultaneously quantify rates of anammox, denitrification, and DNRA in intact sediments adjacent to a seagrass bed in subtropical Australia. The effect of organic carbon lability on NO3- reduction was also addressed by adding detrital sources with differing C:N (phytoplankton- or seagrass-derived). DNRA was the predominant pathway, contributing 49-74% of total NO3- reduction (mean 0.42 μmol N m-2 h-1). In this high C:N system, DNRA outcompetes denitrification for NO3-, functioning to recycle rather than remove N. Anammox exceeded denitrification (mean 0.18 and 0.04 μmol N m-2 h-1, respectively) and accounted for 64-86% of N loss, a rare high percentage in shallow coastal environments. Owing to low denitrification activity, N2O production was ∼100-fold lower than in other coastal sediments (mean 7.7 nmol N m-2 h-1). All NO3- reduction pathways were stimulated by seagrass detritus but not by phytoplankton detritus, suggesting this microbial community is adapted to process organic matter that is typically encountered. The R-IPT-DNRA is widely applicable in other environments where the

  18. Development of a DNA Barcoding System for Seagrasses: Successful but Not Simple

    PubMed Central

    Lucas, Christina; Thangaradjou, Thirunavakkarasu; Papenbrock, Jutta

    2012-01-01

    Seagrasses, a unique group of submerged flowering plants, profoundly influence the physical, chemical and biological environments of coastal waters through their high primary productivity and nutrient recycling ability. They provide habitat for aquatic life, alter water flow, stabilize the ground and mitigate the impact of nutrient pollution. at the coast region. Although on a global scale seagrasses represent less than 0.1% of the angiosperm taxa, the taxonomical ambiguity in delineating seagrass species is high. Thus, the taxonomy of several genera is unsolved. While seagrasses are capable of performing both, sexual and asexual reproduction, vegetative reproduction is common and sexual progenies are always short lived and epimeral in nature. This makes species differentiation often difficult, especially for non-taxonomists since the flower as a distinct morphological trait is missing. Our goal is to develop a DNA barcoding system assisting also non-taxonomists to identify regional seagrass species. The results will be corroborated by publicly available sequence data. The main focus is on the 14 described seagrass species of India, supplemented with seagrasses from temperate regions. According to the recommendations of the Consortium for the Barcoding of Life (CBOL) rbcL and matK were used in this study. After optimization of the DNA extraction method from preserved seagrass material, the respective sequences were amplified from all species analyzed. Tree- and character-based approaches demonstrate that the rbcL sequence fragment is capable of resolving up to family and genus level. Only matK sequences were reliable in resolving species and partially the ecotype level. Additionally, a plastidic gene spacer was included in the analysis to confirm the identification level. Although the analysis of these three loci solved several nodes, a few complexes remained unsolved, even when constructing a combined tree for all three loci. Our approaches contribute to the

  19. Seagrass response to CO₂ contingent on epiphytic algae: indirect effects can overwhelm direct effects.

    PubMed

    Burnell, Owen W; Russell, Bayden D; Irving, Andrew D; Connell, Sean D

    2014-11-01

    Increased availability of dissolved CO2 in the ocean can enhance the productivity and growth of marine plants such as seagrasses and algae, but realised benefits may be contingent on additional conditions (e.g. light) that modify biotic interactions between these plant groups. The combined effects of future CO2 and differing light on the growth of seagrass and their algal epiphytes were tested by maintaining juvenile seagrasses Amphibolis antarctica under three different CO2 concentrations representing ambient, moderate future and high future forecasts (i.e. 390, 650 vs. 900 µl l(-1)) and two light levels representing low and high PAR (i.e. 43 vs. 167 µmol m(-2) s(-1)). Aboveground and belowground biomass, leaf growth, epiphyte cover, tissue chemistry and photosynthetic parameters of seagrasses were measured. At low light, there was a neutral to positive effect of elevated CO2 on seagrass biomass and growth; at high light, this effect of CO2 switched toward negative, as growth and biomass decreased at the highest CO2 level. These opposing responses to CO2 appeared to be closely linked to the overgrowth of seagrass by filamentous algal epiphytes when high light and CO2 were combined. Importantly, all seagrass plants maintained positive leaf growth throughout the experiment, indicating that growth was inhibited by some experimental conditions but not arrested entirely. Therefore, while greater light or elevated CO2 provided direct physiological benefits for seagrasses, such benefits were likely negated by overgrowth of epiphytic algae when greater light and CO2 were combined. This result demonstrates how indirect ecological effects from epiphytes can modify independent physiological predictions for seagrass associated with global change.

  20. A Meta-Analysis of Seaweed Impacts on Seagrasses: Generalities and Knowledge Gaps

    PubMed Central

    Thomsen, Mads S.; Wernberg, Thomas; Engelen, Aschwin H.; Tuya, Fernando; Vanderklift, Mat A.; Holmer, Marianne; McGlathery, Karen J.; Arenas, Francisco; Kotta, Jonne; Silliman, Brian R.

    2012-01-01

    Seagrasses are important habitat-formers and ecosystem engineers that are under threat from bloom-forming seaweeds. These seaweeds have been suggested to outcompete the seagrasses, particularly when facilitated by eutrophication, causing regime shifts where green meadows and clear waters are replaced with unstable sediments, turbid waters, hypoxia, and poor habitat conditions for fishes and invertebrates. Understanding the situations under which seaweeds impact seagrasses on local patch scales can help proactive management and prevent losses at greater scales. Here, we provide a quantitative review of available published manipulative experiments (all conducted at the patch-scale), to test which attributes of seaweeds and seagrasses (e.g., their abundances, sizes, morphology, taxonomy, attachment type, or origin) influence impacts. Weighted and unweighted meta-analyses (Hedges d metric) of 59 experiments showed generally high variability in attribute-impact relationships. Our main significant findings were that (a) abundant seaweeds had stronger negative impacts on seagrasses than sparse seaweeds, (b) unattached and epiphytic seaweeds had stronger impacts than ‘rooted’ seaweeds, and (c) small seagrass species were more susceptible than larger species. Findings (a) and (c) were rather intuitive. It was more surprising that ‘rooted’ seaweeds had comparatively small impacts, particularly given that this category included the infamous invasive Caulerpa species. This result may reflect that seaweed biomass and/or shading and metabolic by-products like anoxia and sulphides could be lower for rooted seaweeds. In conclusion, our results represent simple and robust first-order generalities about seaweed impacts on seagrasses. This review also documented a limited number of primary studies. We therefore identified major knowledge gaps that need to be addressed before general predictive models on seaweed-seagrass interactions can be build, in order to effectively

  1. Species composition and biomasses of fishes in tropical seagrasses at Groote Eylandt, northern Australia

    NASA Astrophysics Data System (ADS)

    Blaber, S. J. M.; Brewer, D. T.; Salini, J. P.; Kerr, J. D.; Conacher, C.

    1992-12-01

    The species composition and biomasses of fishes in the tropical seagrasses of Groote Eylandt, northern Australia, were studied in 1989 and 1990. A total of 156 species was recorded. Tall dense seagrass, short seagrass and control (no seagrass) sites in different depths were compared. Shallow (<1 m) sites were dominated by small resident species and juveniles of non-resident species, while deeper waters (to 7 m) were dominated by larger species. Species composition was not significantly different between sites, but species diversity ( H) and evenness ( E) were higher in non-vegetated areas. In slightly deeper water (<2 m) species composition was different between habitats and species diversity was highest in tall seagrass and least in open areas. Most species were more abundant in tall seagrass and least abundant in open areas. Most of the larger fishes, including 11 species of sharks, are piscivores, and most move into shallow sea-grass areas at night, irrespective of tide height. Only five species showed abundance patterns related to tide height and there were no significant seasonal patterns of abundance in any of the communities. The biomasses for all sites and sampling methods were mostly from 1 to 2 g m -2, which is low relative to other inshore tropical areas. The possible causes—the characteristics of adjacent habitats (coral reefs and mangroves) and the role of seagrasses in the life cycle of fishes are discussed. It is suggested that habitat structure is a major determinant of the species composition of fish in tropical seagrass areas, primarily because it affects food availability, both for small residents and juveniles, and for visiting predators.

  2. Comparative analysis of expressed sequence tag (EST) libraries in the seagrass Zostera marina subjected to temperature stress.

    PubMed

    Reusch, Thorsten B H; Veron, Amelie S; Preuss, Christoph; Weiner, January; Wissler, Lothar; Beck, Alfred; Klages, Sven; Kube, Michael; Reinhardt, Richard; Bornberg-Bauer, Erich

    2008-01-01

    Global warming is associated with increasing stress and mortality on temperate seagrass beds, in particular during periods of high sea surface temperatures during summer months, adding to existing anthropogenic impacts, such as eutrophication and habitat destruction. We compare several expressed sequence tag (EST) in the ecologically important seagrass Zostera marina (eelgrass) to elucidate the molecular genetic basis of adaptation to environmental extremes. We compared the tentative unigene (TUG) frequencies of libraries derived from leaf and meristematic tissue from a control situation with two experimentally imposed temperature stress conditions and found that TUG composition is markedly different among these conditions (all P < 0.0001). Under heat stress, we find that 63 TUGs are differentially expressed (d.e.) at 25 degrees C compared with lower, no-stress condition temperatures (4 degrees C and 17 degrees C). Approximately one-third of d.e. eelgrass genes were characteristic for the stress response of the terrestrial plant model Arabidopsis thaliana. The changes in gene expression suggest complex photosynthetic adjustments among light-harvesting complexes, reaction center subunits of photosystem I and II, and components of the dark reaction. Heat shock encoding proteins and reactive oxygen scavengers also were identified, but their overall frequency was too low to perform statistical tests. In all conditions, the most abundant transcript (3-15%) was a putative metallothionein gene with unknown function. We also find evidence that heat stress may translate to enhanced infection by protists. A total of 210 TUGs contain one or more microsatellites as potential candidates for gene-linked genetic markers. Data are publicly available in a user-friendly database at http://www.uni-muenster.de/Evolution/ebb/Services/zostera .

  3. Technical Abstracts, 1988

    SciTech Connect

    Kotowski, M.

    1989-05-01

    This document is a compilation of the abstracts from unclassified documents published by Mechanical Engineering at Lawrence Livermore National Laboratory (LLNL) during the calendar year 1988. Many abstracts summarize work completed and published in report form. These are UCRL-90,000 and 100,000 series documents, which include the full text of articles to be published in journals and of papers to be presented at meetings, and UCID reports, which are informal documents. Not all UCIDs contain abstracts: short summaries were generated when abstracts were not included. Technical Abstracts also provides brief descriptions of those documents assigned to the MISC (miscellaneous) category. These are generally viewgraphs or photographs presented at meetings. The abstracts cover the broad range of technologies within Mechanical Engineering and are grouped by the principal author's division. An eighth category is devoted to abstracts presented at the CUBE symposium sponsored jointly by LLNL, Los Alamos National Laboratory, and Sandia Laboratories. Within these areas, abstracts are listed numerically. An author index and title index are provided at the back of the book for cross referencing. The publications listed may be obtained by contacting LLNL's TID library or the National Technical Information Service, US Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161. Further information may be obtained by contacting the author directly or the persons listed in the introduction of each subject area.

  4. Leadership Abstracts, Volume 10.

    ERIC Educational Resources Information Center

    Milliron, Mark D., Ed.

    1997-01-01

    The abstracts in this series provide brief discussions of issues related to leadership, administration, professional development, technology, and education in community colleges. Volume 10 for 1997 contains the following 12 abstracts: (1) "On Community College Renewal" (Nathan L. Hodges and Mark D. Milliron); (2) "The Community College Niche in a…

  5. Leadership Abstracts, 1995.

    ERIC Educational Resources Information Center

    Johnson, Larry, Ed.

    1995-01-01

    The abstracts in this series provide two-page discussions of issues related to leadership, administration, and teaching in community colleges. The 12 abstracts for Volume 8, 1995, are: (1) "Redesigning the System To Meet the Workforce Training Needs of the Nation," by Larry Warford; (2) "The College President, the Board, and the Board Chair: A…

  6. Leadership Abstracts, 1996.

    ERIC Educational Resources Information Center

    Johnson, Larry, Ed.

    1996-01-01

    The abstracts in this series provide two-page discussions of issues related to leadership, administration, professional development, technology, and education in community colleges. Volume 9 for 1996 includes the following 12 abstracts: (1) "Tech-Prep + School-To-Work: Working Together To Foster Educational Reform," (Roderick F. Beaumont); (2)…

  7. Data Abstraction in GLISP.

    ERIC Educational Resources Information Center

    Novak, Gordon S., Jr.

    GLISP is a high-level computer language (based on Lisp and including Lisp as a sublanguage) which is compiled into Lisp. GLISP programs are compiled relative to a knowledge base of object descriptions, a form of abstract datatypes. A primary goal of the use of abstract datatypes in GLISP is to allow program code to be written in terms of objects,…

  8. Is It Really Abstract?

    ERIC Educational Resources Information Center

    Kernan, Christine

    2011-01-01

    For this author, one of the most enjoyable aspects of teaching elementary art is the willingness of students to embrace the different styles of art introduced to them. In this article, she describes a project that allows upper-elementary students to learn about abstract art and the lives of some of the master abstract artists, implement the idea…

  9. Paper Abstract Animals

    ERIC Educational Resources Information Center

    Sutley, Jane

    2010-01-01

    Abstraction is, in effect, a simplification and reduction of shapes with an absence of detail designed to comprise the essence of the more naturalistic images being depicted. Without even intending to, young children consistently create interesting, and sometimes beautiful, abstract compositions. A child's creations, moreover, will always seem to…

  10. Paper Abstract Animals

    ERIC Educational Resources Information Center

    Sutley, Jane

    2010-01-01

    Abstraction is, in effect, a simplification and reduction of shapes with an absence of detail designed to comprise the essence of the more naturalistic images being depicted. Without even intending to, young children consistently create interesting, and sometimes beautiful, abstract compositions. A child's creations, moreover, will always seem to…

  11. Is It Really Abstract?

    ERIC Educational Resources Information Center

    Kernan, Christine

    2011-01-01

    For this author, one of the most enjoyable aspects of teaching elementary art is the willingness of students to embrace the different styles of art introduced to them. In this article, she describes a project that allows upper-elementary students to learn about abstract art and the lives of some of the master abstract artists, implement the idea…

  12. Designing for Mathematical Abstraction

    ERIC Educational Resources Information Center

    Pratt, Dave; Noss, Richard

    2010-01-01

    Our focus is on the design of systems (pedagogical, technical, social) that encourage mathematical abstraction, a process we refer to as "designing for abstraction." In this paper, we draw on detailed design experiments from our research on children's understanding about chance and distribution to re-present this work as a case study in designing…

  13. Knowledge-Based Abstracting.

    ERIC Educational Resources Information Center

    Black, William J.

    1990-01-01

    Discussion of automatic abstracting of technical papers focuses on a knowledge-based method that uses two sets of rules. Topics discussed include anaphora; text structure and discourse; abstracting techniques, including the keyword method and the indicator phrase method; and tools for text skimming. (27 references) (LRW)

  14. Organizational Communication Abstracts--1975.

    ERIC Educational Resources Information Center

    Falcione, Raymond L.; And Others

    This document includes nearly 700 brief abstracts of works published in 1975 that are relevant to the field of organizational communication. The introduction presents a rationale for the project, a review of research methods developed by the authors for the preparation of abstracts, a statement of limitations as to the completeness of the coverage…

  15. Flood related loss and recovery of intertidal seagrass meadows in southern Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Campbell, Stuart J.; McKenzie, Len J.

    2004-07-01

    The loss and recovery of intertidal seagrass meadows were assessed following the flood related catastrophic loss of seagrass meadows in February 1999 in the Sandy Strait, Queensland. Region wide recovery rates of intertidal meadows following the catastrophic disturbance were assessed by mapping seagrass abundance in the northern Great Sandy Strait region prior to and on 3 occasions after widespread loss of seagrass. Meadow-scale assessments of seagrass loss and recovery focussed on two existing Zostera capricorni monitoring meadows in the region. Mapping surveys showed that approximately 90% of intertidal seagrasses in the northern Great Sandy Strait disappeared after the February 1999 flooding of the Mary River. Full recovery of all seagrass meadows took 3 years. At the two study sites (Urangan and Wanggoolba Creek) the onset of Z. capricorni germination following the loss of seagrass occurred 14 months post-flood at Wanggoolba Creek, and at Urangan it took 20 months for germination to occur. By February 2001 (24 months post-flood) seagrass abundance at Wanggoolba Creek sites was comparable to pre-flood abundance levels and full recovery at Urangan sites was complete in August 2001 (31 months post-flood). Reduced water quality characterised by 2-3 fold increases in turbidity and nutrient concentrations during the 6 months following the flood was followed by a 95% loss of seagrass meadows in the region. Reductions in available light due to increased flood associated turbidity in February 1999 were the likely cause of seagrass loss in the Great Sandy Strait region, southern Queensland. Although seasonal cues influence the germination of Z. capricorni, the temporal variation in the onset of seed germination between sites suggests that germination following seagrass loss may be dependent on other factors (eg. physical and chemical characteristics of sediments and water). Elevated dissolved nitrogen concentrations during 1999 at Wanggoolba Creek suggest that this site

  16. Redefining the trophic importance of seagrasses for fauna in tropical Indo-Pacific meadows

    NASA Astrophysics Data System (ADS)

    Vonk, Jan Arie; Christianen, Marjolijn J. A.; Stapel, Johan

    2008-09-01

    Fauna species living in seagrass meadows depend on different food sources, with seagrasses often being marginally important for higher trophic levels. To determine the food web of a mixed-species tropical seagrass meadow in Sulawesi, Indonesia, we analyzed the stable isotope ( δ13C and δ15N) signatures of primary producers, particulate organic matter (POM) and fauna species. In addition invertebrates, both infauna and macrobenthic, and fish densities were examined to identify the important species in the meadow. The aims of this study were to identify the main food sources of fauna species by comparing isotopic signatures of different primary producers and fauna, and to estimate qualitatively the importance of seagrass material in the food web. Phytoplankton and water column POM were the most depleted primary food sources for δ13C (range -23.1 to -19.6‰), but no fauna species depended only on these sources for carbon. Epiphytes and Sargassum sp. had intermediate δ13C values (-14.2 to -11.9‰). Sea urchins, gastropods and certain fish species were the main species assimilating this material. Seagrasses and sedimentary POM had the least depleted values (-11.5 to -5.7‰). Between the five seagrass species significant differences in δ13C were measured. The small species Halophila ovalis and Halodule uninervis were most depleted, the largest species Enhalus acoroides was least depleted, while Thalassia hemprichii and Cymodocea rotundata had intermediate values. Fourteen fauna species, accounting for ˜10% of the total fauna density, were shown to assimilate predominantly (>50%) seagrass material, either directly or indirectly by feeding on seagrass consumers. These species ranged from amphipods up to the benthic top predator Taeniura lymma. Besides these species, about half of the 55 fauna species analyzed had δ13C values higher than the least depleted non-seagrass source, indicating they depended at least partly for their food on seagrass material. This study

  17. AxIOM: Amphipod crustaceans from insular Posidonia oceanica seagrass meadows

    PubMed Central

    Heughebaert, André; Lepoint, Gilles

    2016-01-01

    Abstract Background The Neptune grass, Posidonia oceanica (L.) Delile, 1813, is the most widespread seagrass of the Mediterranean Sea. This foundation species forms large meadows that, through habitat and trophic services, act as biodiversity hotspots. In Neptune grass meadows, amphipod crustaceans are one of the dominant groups of vagile invertebrates, forming an abundant and diverse taxocenosis. They are key ecological components of the complex, pivotal, yet critically endangered Neptune grass ecosystems. Nevertheless, comprehensive qualitative and quantitative data about amphipod fauna found in Mediterranean Neptune grass meadows remain scarce, especially in insular locations. New information Here, we provide in-depth metadata about AxIOM, a sample-based dataset published on the GBIF portal. AxIOM is based on an extensive and spatially hierarchized sampling design with multiple years, seasons, day periods, and methods. Samples were taken along the coasts of Calvi Bay (Corsica, France) and of the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, Italy). In total, AxIOM contains 187 samples documenting occurrence (1775 records) and abundance (10720 specimens) of amphipod crustaceans belonging to 72 species spanning 29 families. The dataset is available at http://ipt.biodiversity.be/resource?r=axiom. PMID:27660521

  18. Abstract Datatypes in PVS

    NASA Technical Reports Server (NTRS)

    Owre, Sam; Shankar, Natarajan

    1997-01-01

    PVS (Prototype Verification System) is a general-purpose environment for developing specifications and proofs. This document deals primarily with the abstract datatype mechanism in PVS which generates theories containing axioms and definitions for a class of recursive datatypes. The concepts underlying the abstract datatype mechanism are illustrated using ordered binary trees as an example. Binary trees are described by a PVS abstract datatype that is parametric in its value type. The type of ordered binary trees is then presented as a subtype of binary trees where the ordering relation is also taken as a parameter. We define the operations of inserting an element into, and searching for an element in an ordered binary tree; the bulk of the report is devoted to PVS proofs of some useful properties of these operations. These proofs illustrate various approaches to proving properties of abstract datatype operations. They also describe the built-in capabilities of the PVS proof checker for simplifying abstract datatype expressions.

  19. Detection of seagrass distribution changes from 1991 to 2006 in xincun bay, hainan, with satellite remote sensing.

    PubMed

    Yang, Dingtian; Yang, Chaoyu

    2009-01-01

    Seagrass distribution is a very important index for costal management and protection. Seagrass distribution changes can be used as indexes to analyze the reasons for the changes. In this paper, in situ hyperspectral observation and satellite images of QuickBird, CBERS (China Brazil Earth Resources Satellite data) and Landsat data were used to retrieve bio-optical models and seagrass (Enhalus acoroides, Thalassia hemperichii) distribution in Xincun Bay, Hainan province, and seagrass distribution changes from 1991 to 2006 were analyzed. Hyperspectral results showed that the spectral bands at 555, 635, 650 and 675 nm are sensitive to leaf area index (LAI). Seagrass detection with QuickBird was more accurate than that with Landsat TM and CBERS; five classes could be classified clearly and used as correction for seagrass remote sensing data from Landsat TM and CBERS. In order to better describe seagrass distribution changes, the seagrass distribution area was divided as three regions: region A connected with region B in 1991, however it separated in 1999 and was wholly separated in 2001; seagrass in region C shrank gradually and could not be detected in 2006. Analysis of the reasons for seagrass reduction indicated it was mainly affected by aquaculture and typhoons and in recent years, by land use changes.

  20. Seagrass ecophysiological performance under ocean warming and acidification

    NASA Astrophysics Data System (ADS)

    Repolho, Tiago; Duarte, Bernardo; Dionísio, Gisela; Paula, José Ricardo; Lopes, Ana R.; Rosa, Inês C.; Grilo, Tiago F.; Caçador, Isabel; Calado, Ricardo; Rosa, Rui

    2017-02-01

    Seagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, Fv/Fm) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and Fv/Fm (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, β-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming.

  1. Seagrass ecophysiological performance under ocean warming and acidification.

    PubMed

    Repolho, Tiago; Duarte, Bernardo; Dionísio, Gisela; Paula, José Ricardo; Lopes, Ana R; Rosa, Inês C; Grilo, Tiago F; Caçador, Isabel; Calado, Ricardo; Rosa, Rui

    2017-02-01

    Seagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, Fv/Fm) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and Fv/Fm (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, β-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming.

  2. Seagrass ecophysiological performance under ocean warming and acidification

    PubMed Central

    Repolho, Tiago; Duarte, Bernardo; Dionísio, Gisela; Paula, José Ricardo; Lopes, Ana R.; Rosa, Inês C.; Grilo, Tiago F.; Caçador, Isabel; Calado, Ricardo; Rosa, Rui

    2017-01-01

    Seagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, Fv/Fm) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and Fv/Fm (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, β-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming. PMID:28145531

  3. Science and Management of the Introduced Seagrass Zostera ...

    EPA Pesticide Factsheets

    Healthy seagrass is considered a prime indicator of estuarine ecosystem function. On the Pacific coast of North America, at least two congeners of Zostera occur: native Zostera marina, and introduced, Z. japonica. Z. japonica is considered “invasive” and therefore, ecologically and economically harmful by some, while others consider it benign or perhaps beneficial. Z. japonica does not appear on the Federal or the Oregon invasive species or noxious weed lists. However, the State of California lists it as both an invasive and noxious weed; Washington State recently listed it as a noxious weed. We describe the management dynamics in North America with respect to these congener species and highlight the science and policies behind these decisions. In recent years, management strategies at the state level have ranged from historical protection of Z. japonica as a priority habitat in Washington to eradication in California. In 2011, Washington State reversed its long standing policy to protect Z. japonica and is developing permits for chemical control of this plant. This fractured management approach contradicts efforts to conserve and protect seagrass in other regions of the US and around the world. Science must play a critical role in the assessment of Z. japonica ecology and the immediate and long-term effects of management actions. The information and recommendations provided here can serve as a basis for providing scientific data in order to develo

  4. Simulating the interaction of seagrasses with their ambient flow

    NASA Astrophysics Data System (ADS)

    Backhaus, Jan O.; Verduin, Jennifer J.

    2008-12-01

    The interaction of seagrasses with the dynamics of an oscillatory wave induced flow is assessed with a new Lagrangian plant model. The plant model simulates moving plants in canopies and their dissipative effect on the ambient flow. Concomitantly the plant model is interactively coupled to a 3D hydrodynamic numerical model allowing for a bilateral feedback between moving plants and flow. Model results demonstrate that this interaction causes a modification of current profiles within and above a canopy as compared to an undisturbed flow. While the overall effect of submerged plant canopies is a dampening of dynamics, the flow may locally be intensified. The model predicted an intensification of the flow near the top of a canopy in concurrence with field and laboratory observations. Dissipation in the coupled model, due to the applied non-linear friction law, grows exponentially with increasing flow. As a result the permeability of a canopy to the ambient flow decreases with increasing dissipation. Consequently, at high flow velocities, while becoming increasingly impermeable, a canopy acts like an obstacle that deflects the flow above it, which causes the observed intensification. Results for canopies consisting of seagrasses with different leaf structure and plant geometry show remarkable differences in predicted plant motions, current profiles, drag forces, and velocity shear. Predictions for moving plants are compared with those for rigid, less flexible, structures and undisturbed flow.

  5. Distribution and community structure of ichthyoplankton in Laguna Madre seagrass meadows: Potential impact of seagrass species change

    USGS Publications Warehouse

    Tolan, J.M.; Holt, S.A.; Onuf, C.P.

    1997-01-01

    Seasonal ichthyoplankton surveys were made in the lower Laguna Madre, Texas, to compare the relative utilization of various nursery habitats (shoal grass, Halodule wrightii; manatee grass, Syringodium filiforme;, and unvegetated sand bottom) for both estuarine and offshore-spawned larvae. The species composition and abundance of fish larvae were determined for each habitat type at six locations in the bay. Pushnet ichthyoplankton sampling resulted in 296 total collections, yielding 107,463 fishes representing 55 species in 24 families. A broad spectrum of both the biotic and physical habitat parameters were examined to link the dispersion and distribution of both pre-settlement and post-settlement larvae to the utilization of shallow seagrass habitats. Sample sites were grouped by cluster analysis (Ward's minimum variance method) according to the similarity of their fish assemblages and subsequently examined with a multiple discriminant function analysis to identify important environmental variables. Abiotic environmental factors were most influential in defining groups for samples dominated by early larvae, whereas measures of seagrass complexity defined groups dominated by older larvae and juveniles. Juvenile-stage individuals showed clear habitat preference, with the more shallow Halodule wrightii being the habitat of choice, whereas early larvae of most species were widely distributed over all habitats. As a result of the recent shift of dominance from Halodule wrightii to Syringodium filiforme, overall reductions in the quality of nursery habitat for fishes in the lower Laguna Madre are projected.

  6. The functional value of Caribbean coral reef, seagrass and mangrove habitats to ecosystem processes.

    PubMed

    Harborne, Alastair R; Mumby, Peter J; Micheli, Fiorenza; Perry, Christopher T; Dahlgren, Craig P; Holmes, Katherine E; Brumbaugh, Daniel R

    2006-01-01

    Caribbean coral reef habitats, seagrass beds and mangroves provide important goods and services both individually and through functional linkages. A range of anthropogenic factors are threatening the ecological and economic importance of these habitats and it is vital to understand how ecosystem processes vary across seascapes. A greater understanding of processes will facilitate further insight into the effects of disturbances and assist with assessing management options. Despite the need to study processes across whole seascapes, few spatially explicit ecosystem-scale assessments exist. We review the empirical literature to examine the role of different habitat types for a range of processes. The importance of each of 10 generic habitats to each process is defined as its "functional value" (none, low, medium or high), quantitatively derived from published data wherever possible and summarised in a single figure. This summary represents the first time the importance of habitats across an entire Caribbean seascape has been assessed for a range of processes. Furthermore, we review the susceptibility of each habitat to disturbances to investigate spatial patterns that might affect functional values. Habitat types are considered at the scale discriminated by remotely-sensed imagery and we envisage that functional values can be combined with habitat maps to provide spatially explicit information on processes across ecosystems. We provide examples of mapping the functional values of habitats for populations of three commercially important species. The resulting data layers were then used to generate seascape-scale assessments of "hot spots" of functional value that might be considered priorities for conservation. We also provide an example of how the literature reviewed here can be used to parameterise a habitat-specific model investigating reef resilience under different scenarios of herbivory. Finally, we use multidimensional scaling to provide a basic analysis of the

  7. Abstracts of SIG Sessions.

    ERIC Educational Resources Information Center

    Proceedings of the ASIS Annual Meeting, 1997

    1997-01-01

    Presents abstracts of SIG Sessions. Highlights include digital collections; information retrieval methods; public interest/fair use; classification and indexing; electronic publication; funding; globalization; information technology projects; interface design; networking in developing countries; metadata; multilingual databases; networked…

  8. Searching Sociological Abstracts.

    ERIC Educational Resources Information Center

    Kerbel, Sandra Sandor

    1981-01-01

    Describes the scope, content, and retrieval characteristics of Sociological Abstracts, an online database of literature in the social sciences. Sample searches are displayed, and the strengths and weaknesses of the database are summarized. (FM)

  9. Abstracts--Citations

    ERIC Educational Resources Information Center

    Occupational Mental Health, 1971

    1971-01-01

    Provides abstracts and citations of journal articles and reports dealing with aspects of mental health. Topics include alcoholism, drug abuse, disadvantaged, mental health programs, rehabilitation, student mental health, and others. (SB)

  10. Automatic Abstraction in Planning

    NASA Technical Reports Server (NTRS)

    Christensen, J.

    1991-01-01

    Traditionally, abstraction in planning has been accomplished by either state abstraction or operator abstraction, neither of which has been fully automatic. We present a new method, predicate relaxation, for automatically performing state abstraction. PABLO, a nonlinear hierarchical planner, implements predicate relaxation. Theoretical, as well as empirical results are presented which demonstrate the potential advantages of using predicate relaxation in planning. We also present a new definition of hierarchical operators that allows us to guarantee a limited form of completeness. This new definition is shown to be, in some ways, more flexible than previous definitions of hierarchical operators. Finally, a Classical Truth Criterion is presented that is proven to be sound and complete for a planning formalism that is general enough to include most classical planning formalisms that are based on the STRIPS assumption.

  11. An Abstract Algebra Story.

    ERIC Educational Resources Information Center

    Leron, Uri; Dubinsky, Ed

    1995-01-01

    Describes a constructivist, interactive approach for teaching undergraduate mathematics, abstract algebra in particular, using computer constructions programmed in ISETL to induce students' mental constructions and collaborative learning to help students reflect on these constructions. (18 references) (MKR)

  12. Conference Abstracts: AEDS '82.

    ERIC Educational Resources Information Center

    Journal of Computers in Mathematics and Science Teaching, 1982

    1982-01-01

    Abstracts from nine selected papers presented at the 1982 Association for Educational Data Systems (AEDS) conference are provided. Copies of conference proceedings may be obtained for fifteen dollars from the Association. (MP)

  13. Evidence for seagrass meadows and their response to paleoenvironmental changes in the early Eocene (Jafnayn Formation, Wadi Bani Khalid, N Oman)

    NASA Astrophysics Data System (ADS)

    Tomás, Sara; Frijia, Gianluca; Bömelburg, Esther; Zamagni, Jessica; Perrin, Christine; Mutti, Maria

    2016-07-01

    The recognition and understanding of vegetated habitats in the fossil record are of crucial importance in order to investigate paleoecological responses and indirectly infer climate and sea-level changes. However, the low preservation potential of plants and macroalgae hampers a direct identification of these environments in the geological past. Here we present sedimentological and paleontological evidences as tool to identify the presence of different seagrass-vegetated environments in the shallow marine settings of the lower Eocene Jafnayn platform of Oman and their responses to paleoenvironmental changes. The studied lower Eocene deposits consist of well bedded, nodular packstones dominated by encrusting acervulinid and alveolinid foraminifera passing upward to an alternance of packstones with echinoids and quartz grains and grainstones rich in Orbitolites, smaller miliolid foraminifera and quartz grains. The presence of seagrass is inferred by the occurrence of encrusting acervulinids and soritid Orbitolites, as well as by their test morphologies together with further sedimentological criteria. The clear shift observed in the faunal assemblages and sedimentary features may be related to a major reorganization of the carbonate system passing from a carbonate platform to a ramp-like platform with increased terrigenous sedimentation. Heterotroph tubular acervulinids and oligotroph alveolinids of the carbonate platform were replaced upward by more heterotroph organisms such as large, discoidal Orbitolites and smaller miliolids, most likely due to enhanced nutrient levels which would have led to a change of phytal substrate, from cylindrical-leaf dominated grasses into flat-leafed ones.

  14. A geospatial modelling approach to predict seagrass habitat recovery under multiple stressor regimes

    EPA Science Inventory

    Restoration of estuarine seagrass habitats requires a clear understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We have developed and demonstrated a geospatial modeling a...

  15. Development of an epiphyte indicator of nutrient enrichment: Threshold values for seagrass epiphyte load

    EPA Science Inventory

    Metrics of epiphyte load on macrophytes were evaluated for use as quantitative biological indicators for nutrient impacts in estuarine waters, based on review and analysis of the literature on epiphytes and macrophytes, primarily seagrasses, but including some brackish and freshw...

  16. Anthropogenic chemicals as drivers of change for coastal ecosystems: wetlands, mangroves and seagrass habitats.

    EPA Science Inventory

    Coastal wetlands, mangrove and seagrass habitats are rapidly declining worldwide which reduces their many ecological services. This presentation summarizes the results of a literature survey conducted to determine scientific understanding of contaminant uptake and toxicity of non...

  17. Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems.

    PubMed

    Lepoint, Gilles; Dauby, Patrick; Gobert, Sylvie

    2004-12-01

    Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem.

  18. A geospatial modelling approach to predict seagrass habitat recovery under multiple stressor regimes

    EPA Science Inventory

    Restoration of estuarine seagrass habitats requires a clear understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We have developed and demonstrated a geospatial modeling a...

  19. Anthropogenic chemicals as drivers of change for coastal ecosystems: wetlands, mangroves and seagrass habitats.

    EPA Science Inventory

    Coastal wetlands, mangrove and seagrass habitats are rapidly declining worldwide which reduces their many ecological services. This presentation summarizes the results of a literature survey conducted to determine scientific understanding of contaminant uptake and toxicity of non...

  20. Development of an epiphyte indicator of nutrient enrichment: Threshold values for seagrass epiphyte load

    EPA Science Inventory

    Metrics of epiphyte load on macrophytes were evaluated for use as quantitative biological indicators for nutrient impacts in estuarine waters, based on review and analysis of the literature on epiphytes and macrophytes, primarily seagrasses, but including some brackish and freshw...

  1. Abstracts of contributed papers

    SciTech Connect

    Not Available

    1994-08-01

    This volume contains 571 abstracts of contributed papers to be presented during the Twelfth US National Congress of Applied Mechanics. Abstracts are arranged in the order in which they fall in the program -- the main sessions are listed chronologically in the Table of Contents. The Author Index is in alphabetical order and lists each paper number (matching the schedule in the Final Program) with its corresponding page number in the book.

  2. Mapping seagrass coverage and spatial patterns with high spatial resolution IKONOS imagery

    NASA Astrophysics Data System (ADS)

    Pu, Ruiliang; Bell, Susan

    2017-02-01

    Seagrass habitats in subtidal coastal waters provide a variety of ecosystem functions and services and there is an increasing need to acquire information on spatial and temporal dynamics of this resource. Here, we explored the capability of IKONOS (IKO) data of high resolution (4 m) for mapping seagrass cover [submerged aquatic vegetation (%SAV) cover] along the mid-western coast of Florida, USA. We also compared seagrass maps produced with IKO data with that obtained using the Landsat TM sensor with lower resolution (30 m). Both IKO and TM data, collected in October 2009, were preprocessed to calculate water depth invariant bands to normalize the effect of varying depth on bottom spectra recorded by the two satellite sensors and further the textural information was extracted from IKO data. Our results demonstrate that the high resolution IKO sensor produced a higher accuracy than the TM sensor in a three-class % SAV cover classification. Of note is that the OA of %SAV cover mapping at our study area created with IKO data was 5-20% higher than that from other studies published. We also examined the spatial distribution of seagrass over a spatial range of 4-240 m using the Ripley's K function [L(d)] and IKO data that represented four different grain sizes [4 m (one IKO pixel), 8 m (2 × 2 IKO pixels), 12 m (3 × 3 IKO pixels), and 16 m (4 × 4 IKO pixels)] from moderate-dense seagrass cover along a set of six transects. The Ripley's K metric repeatedly indicated that seagrass cover representing 4 m × 4 m pixels displayed a dispersed (or slightly dispersed) pattern over distances of <4-8 m, and a random or slightly clustered pattern of cover over 9-240 m. The spatial pattern of seagrass cover created with the three additional grain sizes (i.e., 2 × 24 m IKO pixels, 3 × 34 m IKO pixels, and 4 × 4 m IKO pixels) show a dispersed (or slightly dispersed) pattern across 4-32 m and a random or slightly clustered pattern across 33-240 m. Given the first report on using

  3. A spatial model to improve site selection for seagrass restoration in shallow boating environments.

    PubMed

    Hotaling-Hagan, Althea; Swett, Robert; Ellis, L Rex; Frazer, Thomas K

    2017-01-15

    Due to widespread and continuing seagrass loss, restoration attempts occur worldwide. This article presents a geospatial modeling technique that ranks the suitability of sites for restoration based on light availability and boating activity, two factors cited in global studies of seagrass loss and restoration failures. The model presented here was created for Estero Bay, Florida and is a predictive model of light availability and boating pressure to aid seagrass restoration efforts. The model is adaptive and can be parameterized for different locations and updated as additional data is collected and knowledge of how factors impact seagrass improves. Light data used for model development were collected over one year from 50 sites throughout the bay. Coupled with high resolution bathymetric data, bottom mean light availability was predicted throughout the bay. Data collection throughout the year also allowed for prediction of light variability at sites, a possible indicator of seagrass growth and survival. Additionally, survey data on boating activities were used to identify areas, outside of marked navigation channels, that receive substantial boating pressure and are likely poor candidate sites for seagrass restoration. The final map product identifies areas where the light environment was suitable for seagrasses and boating pressure was low. A composite map showing the persistence of seagrass coverage in the study area over four years, between 1999 and 2006, was used to validate the model. Eighty-nine percent of the area where seagrass persisted (had been mapped all four years) was ranked as suitable for restoration: 42% with the highest rank (7), 28% with a rank of 6, and 19% with a rank of 5. The results show that the model is a viable tool for selection of seagrass restoration sites in Florida and elsewhere. With knowledge of the light environment and boating patterns, managers will be better equipped to set seagrass restoration and water quality improvement

  4. Limited effects of source population identity and number on seagrass transplant performance.

    PubMed

    Novak, Alyssa B; Plaisted, Holly K; Hays, Cynthia G; Hughes, Randall A

    2017-01-01

    Global declines in coastal foundation species highlight the importance of effective restoration. In this study, we examined the effects of source population identity and diversity (one vs. three sources per plot) on seagrass (Zostera marina) transplant success. The field experiment was replicated at two locations in Massachusetts with adjacent natural Zostera marina beds to test for local adaptation and source diversity effects on shoot density. We also collected morphological and genetic data to characterize variation within and among source populations, and evaluate whether they were related to performance. Transplants grew and expanded until six months post-transplantation, but then steadily declined at both sites. Prior to declines, we observed variation in performance among source populations at one site that was related to morphological traits: the populations with the longest leaves had the highest shoot densities, whereas the population with the shortest leaves performed the worst at six months post-transplantation. In addition, multiple source plots at this same transplant site consistently had similar or higher shoot densities than single source plots, and shoots from weak-performing populations showed improved performance in multiple source plots. We found no evidence for home site advantage or benefits of population-level genetic variation in early transplant performance at either site. Our results show limited effects of source population on early transplant performance and suggest that factors (e.g., morphology) other than home site advantage and population genetic variation serve a role. Based on our overall findings that transplant success varied among source populations and that population diversity at the plot level had positive but limited effects on individual and plot performance, we support planting shoots from multiple source sites in combination to enhance transplant success, particularly in the absence of detailed information on individual

  5. Assessment of genetic diversity of seagrass populations using DNA fingerprinting: implications for population stability and management.

    PubMed Central

    Alberte, R S; Suba, G K; Procaccini, G; Zimmerman, R C; Fain, S R

    1994-01-01

    Populations of the temperate seagrass, Zostera marina L. (eelgrass), often exist as discontinuous beds in estuaries, harbors, and bays where they can reproduce sexually or vegetatively through clonal propagation. We examined the genetic structure of three geographically and morphologically distinct populations from central California (Elkhorn Slough, Tomales Bay, and Del Monte Beach), using multilocus restriction fragment length polymorphisms (DNA fingerprints). Within-population genetic similarity (Sw) values for the three eelgrass populations ranged from 0.44 to 0.68. The Tomales Bay population located in an undisturbed, littoral site possessed a within-population genetic similarity (Sw = 0.44) that was significantly lower than those of the other two populations. Cluster analysis identified genetic substructure in only the undisturbed subtidal population (Del Monte Beach). Between-population similarity values (Sb) for all pairwise comparisons ranged from 0.47 to 0.51. The three eelgrass populations show significantly less between locale genetic similarity than found within populations, indicating that gene flow is restricted between locales even though two of the populations are separated by only 30 km. The study demonstrates that (i) natural populations of Z. marina from both disturbed and undisturbed habitats possess high genetic diversity and are not primarily clonal, (ii) gene flow is restricted even between populations in close proximity, (iii) an intertidal population from a highly disturbed habital shows much lower genetic diversity than an intertidal population from an undisturbed site, and (iv) DNA fingerprinting techniques can be exploited to understand gene flow and population genetic structure in Z. marina, a widespread and ecologically important species, and as such are relevant to the management of this coastal resource. Images PMID:11607458

  6. Limited effects of source population identity and number on seagrass transplant performance

    PubMed Central

    Plaisted, Holly K.; Hays, Cynthia G.; Hughes, Randall A.

    2017-01-01

    Global declines in coastal foundation species highlight the importance of effective restoration. In this study, we examined the effects of source population identity and diversity (one vs. three sources per plot) on seagrass (Zostera marina) transplant success. The field experiment was replicated at two locations in Massachusetts with adjacent natural Zostera marina beds to test for local adaptation and source diversity effects on shoot density. We also collected morphological and genetic data to characterize variation within and among source populations, and evaluate whether they were related to performance. Transplants grew and expanded until six months post-transplantation, but then steadily declined at both sites. Prior to declines, we observed variation in performance among source populations at one site that was related to morphological traits: the populations with the longest leaves had the highest shoot densities, whereas the population with the shortest leaves performed the worst at six months post-transplantation. In addition, multiple source plots at this same transplant site consistently had similar or higher shoot densities than single source plots, and shoots from weak-performing populations showed improved performance in multiple source plots. We found no evidence for home site advantage or benefits of population-level genetic variation in early transplant performance at either site. Our results show limited effects of source population on early transplant performance and suggest that factors (e.g., morphology) other than home site advantage and population genetic variation serve a role. Based on our overall findings that transplant success varied among source populations and that population diversity at the plot level had positive but limited effects on individual and plot performance, we support planting shoots from multiple source sites in combination to enhance transplant success, particularly in the absence of detailed information on individual

  7. Developing a methodology of bioindication of human-induced effects using seagrass morphological variation in Spermonde Archipelago, South Sulawesi, Indonesia.

    PubMed

    Ambo-Rappe, Rohani

    2014-09-15

    Seagrass is particularly susceptible to environmental degradation. The objective of the study is to develop an effective bioindicator to assess human-induced effects using morphological variation and fluctuating asymmetry (FA) of seagrass. Samples were collected from eight islands situated at different distance from mainland with different human population density and therefore expected to experience different level of anthropogenic pressure. Cd, Pb, Cu, Zn, nitrate, and phosphate were measured. Metals were also measured in tissues of seagrass. Metal concentrations in sediment, water, and seagrass did not exceed the quality standards required for marine life. Heterogeneity of FA was found among sites suggesting that there are some factors changing developmental instability of seagrass which is not associated to particular toxicants. This baseline study indicates that the water condition is still natural and shows no signs of metal contamination, therefore it does not cause a detectable stress on morphological variation and FA of seagrass.

  8. Edge Effects along a Seagrass Margin Result in an Increased Grazing Risk on Posidonia australis Transplants

    PubMed Central

    Statton, John; Gustin-Craig, Samuel; Dixon, Kingsley W.; Kendrick, Gary A.

    2015-01-01

    A key issue in habitat restoration are the changes in ecological processes that occur when fragments of habitat are lost, resulting in the persistence of habitat-degraded margins. Margins often create or enhance opportunities for negative plant-herbivore interactions, preventing natural or assisted re-establishment of native vegetation into the degraded area. However, at some distance from the habitat margin these negative interactions may relax. Here, we posit that the intensity of species interactions in a fragmented Posidonia australis seagrass meadow may be spatially dependent on proximity to the seagrass habitat edge, whereby the risk of grazing is high and the probability of survival of seagrass transplants is low. To test this, transplants were planted 2 m within the meadow, on the meadow edge at 0m, and at 2m, 10m, 30m, 50m and 100m distance from the edge of the seagrass meadow into the unvegetated sand sheet. There was an enhanced grazing risk 0-10m from the edge, but decreased sharply with increasing distances (>30m). Yet, the risk of grazing was minimal inside the seagrass meadow, indicating that grazers may use the seagrass meadow for refuge but are not actively grazing within it. The relationship between short-term herbivory risk and long-term survival was not straightforward, suggesting that other environmental filters are also affecting survival of P. australis transplants within the study area. We found that daily probability of herbivory was predictable and operating over a small spatial scale at the edge of a large, intact seagrass meadow. These findings highlight the risk from herbivory can be high, and a potential contributing factor to seagrass establishment in restoration programs. PMID:26465926

  9. Tropical seagrass meadows modify seawater carbon chemistry: implications for coral reefs impacted by ocean acidification

    NASA Astrophysics Data System (ADS)

    Unsworth, Richard K. F.; Collier, Catherine J.; Henderson, Gideon M.; McKenzie, Len J.

    2012-06-01

    Highly productive tropical seagrasses often live adjacent to or among coral reefs and utilize large amounts of inorganic carbon. In this study, the effect of seagrass productivity on seawater carbonate chemistry and coral calcification was modelled on the basis of an analysis of published data. Published data (11 studies, 64 records) reveal that seagrass meadows in the Indo-Pacific have an 83% chance of being net autotrophic, resulting in an average net sink of 155 gC m-2 yr-1. The capacities for seagrass productivity were analysed using an empirical model to examine the effect on seawater carbonate chemistry. Our analyses indicate that increases in pH of up to 0.38 units, and Ωarag increases of 2.9 are possible in the presence of seagrass meadows (compared to their absence) with the precise values of these increases dependent on water residence time (tidal flushing) and water depth. In shallow water reef environments, Scleractinian coral calcification downstream of seagrass has the potential to be ≈18% greater than in an environment without seagrass. If this potential benefit to reef calcifiers is supported by further study it offers a potential tool in marine park management at a local scale. The applicability of this will depend upon local physical conditions as well as the spatial configuration of habitats, and the factors that influence their productivity. This novel study suggests that, in addition to their importance to fisheries, sediment stabilization and primary production, seagrass meadows may enhance coral reef resilience to future ocean acidification.

  10. Transplantation as a method for restoring the seagrass Posidonia australis

    NASA Astrophysics Data System (ADS)

    Bastyan, G. R.; Cambridge, M. L.

    2008-08-01

    Transplant trials of the seagrass Posidonia australis were carried out after loss of seagrasses following eutrophication and increased turbidity in two marine inlets on the south coast of Western Australia. A pilot study in Oyster Harbour measured survival and growth in situ for 4 years. Long-term survival rates were high (96-98%), providing plants were anchored into the sediment. All unanchored plants were lost in the first winter. Following the success of the pilot study, a more comprehensive program began 3 years later with over 500 transplant units collected from either actively growing edges of nearby patches (plagiotropic growth form) or within established meadows (orthotropic growth form). Transplant units from edges expanded at a faster rate compared to units from mid-meadow but increases in shoot numbers were similar. Growth rates in the first 2.5 years averaged 10-20 cm yr -1 horizontal rhizome extension, depending on the source of the transplant units, and 4-12 shoots per initial shoot yr -1, depending on the initial shoot number of the transplant unit. After 5 years, shoot numbers of individual transplants were similar to shoot densities recorded for natural meadows, >500 shoots m -2. Approximately, 10% of transplants from mid-meadow flowered in the first year, whereas transplants from edges flowered only after 5 years. Transplant trials were also established in nearby Princess Royal Harbour at a site selected to test the effect of disturbance by bioturbation from large sand-burrowing worms or by sediment erosion. Survival was lower than in Oyster Harbour, 75-89% in areas with bioturbation but only 14% in areas where sediments were eroded. Growth was poor, <1-2 shoots per shoot yr -1 with high shoot mortality, and low rates of increase in rhizome length, <5 cm yr -1. In areas affected by worm bioturbation, there was almost no horizontal expansion of plants because rhizomes grew vertically to keep pace with sediment deposition. This study showed that

  11. Effects of elevated turbidity and nutrients on the net production of a tropical seagrass community

    SciTech Connect

    Caldwell, J.W.

    1985-01-01

    Dredging effects on seagrass communities in the Florida Keys were examined by (1) comparing impacts on net production resulting from dredging and natural weather events, (2) determining changes in community photosynthetic efficiency, (3) evaluating shading and nutrient effects on net production, and (4) developing a systems dynamics model. Net community production was estimated during numerous meteorological and dredging events using the Odum-Hoskins oxygen technique in flow-through field microcosms. In other experiments, shading and nutrients (phosphorus, nitrate, and ammonia) were manipulated to simulate dredge plume conditions. The greatest depression in net community production resulted from severe thunderstorms and dredging events, respectively. In field microcosm experiments, significant interaction occurred between shading and nutrient concentration. The model of seagrass production was most sensitive to changes in nutrient-seagrass relationships, seagrass production estimates, and seagrass-light interactions. Recovery of seagrass biomass following numerous dredging events (3.5 years) was longer than that from the estimated total annual thunderstorms encountered (1 year) but shorter than recovery from hurricane events (4.1 years).

  12. Mangroves as a major source of soil carbon storage in adjacent seagrass meadows

    PubMed Central

    Chen, Guangcheng; Azkab, Muhammad Husni; Chmura, Gail L.; Chen, Shunyang; Sastrosuwondo, Pramudji; Ma, Zhiyuan; Dharmawan, I. Wayan Eka; Yin, Xijie; Chen, Bin

    2017-01-01

    Mangrove forests have the potential to export carbon to adjacent ecosystems but whether mangrove-derived organic carbon (OC) would enhance the soil OC storage in seagrass meadows adjacent to mangroves is unclear. In this study we examine the potential for the contribution of mangrove OC to seagrass soils on the coast of North Sulawesi, Indonesia. We found that seagrass meadows adjacent to mangroves had significantly higher soil OC concentrations, soil OC with lower δ 13C, and lower bulk density than those at the non-mangrove adjacent meadows. Soil OC storage to 30 cm depth ranged from 3.21 to 6.82 kg C m−2, and was also significantly higher at the mangrove adjacent meadows than those non-adjacent meadows. δ13C analyses revealed that mangrove OC contributed 34 to 83% to soil OC at the mangrove adjacent meadows. The δ13C value of seagrass plants was also different between the seagrasses adjacent to mangroves and those which were not, with lower values measured at the seagrasses adjacent to mangroves. Moreover, we found significant spatial variation in both soil OC concentration and storage, with values decreasing toward sea, and the contribution of mangrove-derived carbon also reduced with distance from the forest. PMID:28186151

  13. The Power of Three: Coral Reefs, Seagrasses and Mangroves Protect Coastal Regions and Increase Their Resilience.

    PubMed

    Guannel, Greg; Arkema, Katie; Ruggiero, Peter; Verutes, Gregory

    2016-01-01

    Natural habitats have the ability to protect coastal communities against the impacts of waves and storms, yet it is unclear how different habitats complement each other to reduce those impacts. Here, we investigate the individual and combined coastal protection services supplied by live corals on reefs, seagrass meadows, and mangrove forests during both non-storm and storm conditions, and under present and future sea-level conditions. Using idealized profiles of fringing and barrier reefs, we quantify the services supplied by these habitats using various metrics of inundation and erosion. We find that, together, live corals, seagrasses, and mangroves supply more protection services than any individual habitat or any combination of two habitats. Specifically, we find that, while mangroves are the most effective at protecting the coast under non-storm and storm conditions, live corals and seagrasses also moderate the impact of waves and storms, thereby further reducing the vulnerability of coastal regions. Also, in addition to structural differences, the amount of service supplied by habitats in our analysis is highly dependent on the geomorphic setting, habitat location and forcing conditions: live corals in the fringing reef profile supply more protection services than seagrasses; seagrasses in the barrier reef profile supply more protection services than live corals; and seagrasses, in our simulations, can even compensate for the long-term degradation of the barrier reef. Results of this study demonstrate the importance of taking integrated and place-based approaches when quantifying and managing for the coastal protection services supplied by ecosystems.

  14. Community metabolism in shallow coral reef and seagrass ecosystems, lower Florida Keys

    USGS Publications Warehouse

    Turk, Daniela; Yates, Kimberly K.; Vega-Rodriguez, Maria; Toro-Farmer, Gerardo; L'Esperance, Chris; Melo, Nelson; Ramsewak, Deanesch; Estrada, S. Cerdeira; Muller-Karger, Frank E.; Herwitz, Stan R.; McGillis, Wade

    2016-01-01

    Diurnal variation of net community production (NEP) and net community calcification (NEC) were measured in coral reef and seagrass biomes during October 2012 in the lower Florida Keys using a mesocosm enclosure and the oxygen gradient flux technique. Seagrass and coral reef sites showed diurnal variations of NEP and NEC, with positive values at near-seafloor light levels >100–300 µEinstein m-2 s-1. During daylight hours, we detected an average NEP of 12.3 and 8.6 mmol O2 m-2 h-1 at the seagrass and coral reef site, respectively. At night, NEP at the seagrass site was relatively constant, while on the coral reef, net respiration was highest immediately after dusk and decreased during the rest of the night. At the seagrass site, NEC values ranged from 0.20 g CaCO3 m-2 h-1 during daylight to -0.15 g CaCO3 m-2 h-1 at night, and from 0.17 to -0.10 g CaCO3 m-2 h-1 at the coral reef site. There were no significant differences in pH and aragonite saturation states (Ωar) between the seagrass and coral reef sites. Decrease in light levels during thunderstorms significantly decreased NEP, transforming the system from net autotrophic to net heterotrophic.

  15. Salt marsh and seagrass communities of Bakkhali Estuary, Cox's Bazar, Bangladesh

    NASA Astrophysics Data System (ADS)

    Hena, M. K. Abu; Short, F. T.; Sharifuzzaman, S. M.; Hasan, M.; Rezowan, M.; Ali, M.

    2007-10-01

    The species identification, distribution pattern, density and biomass of salt marsh and seagrass plants with some of the ecological parameters were studied in the Bakkhali river estuary, Cox's Bazar, Bangladesh during the first half of 2006. Two salt marsh species ( Spartina sp. and Imperata cylindrica) and one seagrass species ( Halophila beccarii) were identified during this investigation, providing the first reports of Spartina sp. and H. beccarii in coastal Bangladesh. Seagrass H. beccarii was found in an accreted area and co-existing with salt marsh, and scattered sparsely in the salt marsh habitat and macroalgae Ulva intestinalis. Flowering and fruiting were recorded from the seagrass H. beccarri during January and February. No flowers and fruits were observed for the salt marsh Spartina sp. during the study period. Results showed that the shoot density of Spartina ranged from 400 to 2875 shoots m -2 with the highest total biomass (165.80 g dry weight (DW) m -2) in March. Shoot density of H. beccarii ranged from 2716 to 14320 shoots m -2 in this estuarine coastal environment. The total biomass of seagrass was higher (17.56 g DW m -2) in March compared to the other months. The highest H. beccarii above ground (AG) biomass and below ground (BG) biomass were 9.59 g DW m -2 and 9.42 g DW m -2, respectively. These parameters are comparable with those generally observed for the salt marsh and seagrass species in the other places of the world.

  16. The Power of Three: Coral Reefs, Seagrasses and Mangroves Protect Coastal Regions and Increase Their Resilience

    PubMed Central

    Guannel, Greg; Arkema, Katie; Ruggiero, Peter; Verutes, Gregory

    2016-01-01

    Natural habitats have the ability to protect coastal communities against the impacts of waves and storms, yet it is unclear how different habitats complement each other to reduce those impacts. Here, we investigate the individual and combined coastal protection services supplied by live corals on reefs, seagrass meadows, and mangrove forests during both non-storm and storm conditions, and under present and future sea-level conditions. Using idealized profiles of fringing and barrier reefs, we quantify the services supplied by these habitats using various metrics of inundation and erosion. We find that, together, live corals, seagrasses, and mangroves supply more protection services than any individual habitat or any combination of two habitats. Specifically, we find that, while mangroves are the most effective at protecting the coast under non-storm and storm conditions, live corals and seagrasses also moderate the impact of waves and storms, thereby further reducing the vulnerability of coastal regions. Also, in addition to structural differences, the amount of service supplied by habitats in our analysis is highly dependent on the geomorphic setting, habitat location and forcing conditions: live corals in the fringing reef profile supply more protection services than seagrasses; seagrasses in the barrier reef profile supply more protection services than live corals; and seagrasses, in our simulations, can even compensate for the long-term degradation of the barrier reef. Results of this study demonstrate the importance of taking integrated and place-based approaches when quantifying and managing for the coastal protection services supplied by ecosystems. PMID:27409584

  17. Mangroves as a major source of soil carbon storage in adjacent seagrass meadows

    NASA Astrophysics Data System (ADS)

    Chen, Guangcheng; Azkab, Muhammad Husni; Chmura, Gail L.; Chen, Shunyang; Sastrosuwondo, Pramudji; Ma, Zhiyuan; Dharmawan, I. Wayan Eka; Yin, Xijie; Chen, Bin

    2017-02-01

    Mangrove forests have the potential to export carbon to adjacent ecosystems but whether mangrove-derived organic carbon (OC) would enhance the soil OC storage in seagrass meadows adjacent to mangroves is unclear. In this study we examine the potential for the contribution of mangrove OC to seagrass soils on the coast of North Sulawesi, Indonesia. We found that seagrass meadows adjacent to mangroves had significantly higher soil OC concentrations, soil OC with lower δ 13C, and lower bulk density than those at the non-mangrove adjacent meadows. Soil OC storage to 30 cm depth ranged from 3.21 to 6.82 kg C m-2, and was also significantly higher at the mangrove adjacent meadows than those non-adjacent meadows. δ13C analyses revealed that mangrove OC contributed 34 to 83% to soil OC at the mangrove adjacent meadows. The δ13C value of seagrass plants was also different between the seagrasses adjacent to mangroves and those which were not, with lower values measured at the seagrasses adjacent to mangroves. Moreover, we found significant spatial variation in both soil OC concentration and storage, with values decreasing toward sea, and the contribution of mangrove-derived carbon also reduced with distance from the forest.

  18. Modelling seagrass growth and development to evaluate transplanting strategies for restoration.

    PubMed

    Renton, Michael; Airey, Michael; Cambridge, Marion L; Kendrick, Gary A

    2011-10-01

    Seagrasses are important marine plants that are under threat globally. Restoration by transplanting vegetative fragments or seedlings into areas where seagrasses have been lost is possible, but long-term trial data are limited. The goal of this study is to use available short-term data to predict long-term outcomes of transplanting seagrass. A functional-structural plant model of seagrass growth that integrates data collected from short-term trials and experiments is presented. The model was parameterized for the species Posidonia australis, a limited validation of the model against independent data and a sensitivity analysis were conducted and the model was used to conduct a preliminary evaluation of different transplanting strategies. The limited validation was successful, and reasonable long-term outcomes could be predicted, based only on short-term data. This approach for modelling seagrass growth and development enables long-term predictions of the outcomes to be made from different strategies for transplanting seagrass, even when empirical long-term data are difficult or impossible to collect. More validation is required to improve confidence in the model's predictions, and inclusion of more mechanism will extend the model's usefulness. Marine restoration represents a novel application of functional-structural plant modelling.

  19. Modelling seagrass growth and development to evaluate transplanting strategies for restoration

    PubMed Central

    Renton, Michael; Airey, Michael; Cambridge, Marion L.; Kendrick, Gary A.

    2011-01-01

    Background and Aims Seagrasses are important marine plants that are under threat globally. Restoration by transplanting vegetative fragments or seedlings into areas where seagrasses have been lost is possible, but long-term trial data are limited. The goal of this study is to use available short-term data to predict long-term outcomes of transplanting seagrass. Methods A functional–structural plant model of seagrass growth that integrates data collected from short-term trials and experiments is presented. The model was parameterized for the species Posidonia australis, a limited validation of the model against independent data and a sensitivity analysis were conducted and the model was used to conduct a preliminary evaluation of different transplanting strategies. Key Results The limited validation was successful, and reasonable long-term outcomes could be predicted, based only on short-term data. Conclusions This approach for modelling seagrass growth and development enables long-term predictions of the outcomes to be made from different strategies for transplanting seagrass, even when empirical long-term data are difficult or impossible to collect. More validation is required to improve confidence in the model's predictions, and inclusion of more mechanism will extend the model's usefulness. Marine restoration represents a novel application of functional–structural plant modelling. PMID:21821624

  20. Epiphyte dynamics and carbon metabolism in a nutrient enriched Mediterranean seagrass ( Posidonia oceanica ) ecosystem

    NASA Astrophysics Data System (ADS)

    Apostolaki, Eugenia T.; Holmer, Marianne; Marbà, Núria; Karakassis, Ioannis

    2011-08-01

    The study aimed at examining the relationship between epiphyte dynamics and carbon metabolism in seagrass ecosystems under nutrient enrichment. Temporal variability of epiphytes and factors controlling their dynamics (i.e. environmental conditions, substratum availability, substratum stability and herbivore pressure) were assessed in a fish farm impacted and an unaffected Mediterranean seagrass ( Posidonia oceanica) meadow in the Aegean Sea (Greece). The factors controlling epiphyte dynamics responded differently to nutrient enrichment and partly interacted, rendering their cumulative effect on epiphyte load difficult to elucidate. Yet epiphytes accumulated on seagrass leaves near to the fish farm throughout the year, contributing 2 times more in above-ground biomass at cages than the control station. Reduction in substratum availability (i.e. decrease in leaf biomass) and increase in herbivore pressure affected epiphyte load, albeit their effects were not strong enough to counterbalance the effect of nutrient input from fish farm effluents. Moderate yet continuous nutrient input possibly stimulated epiphyte growth in excess of herbivory, shifting the control of epiphytes from top-down to bottom-up. Epiphyte accumulation affected carbon metabolism in the seagrass ecosystem by contributing to enhanced dissolved organic carbon (DOC) release, but seagrass loss was so acute that increased epiphyte cover could not counterbalance the decrease in community carbon production which was mainly driven by seagrass decline.

  1. Ecosystem Engineering by Seagrasses Interacts with Grazing to Shape an Intertidal Landscape

    PubMed Central

    van der Heide, Tjisse; Eklöf, Johan S.; van Nes, Egbert H.; van der Zee, Els M.; Donadi, Serena; Weerman, Ellen J.; Olff, Han; Eriksson, Britas Klemens

    2012-01-01

    Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model indicated that the mosaic resulted from localized sediment accretion by seagrass followed by selective waterfowl grazing. Hollows were bare in winter, but were rapidly colonized by seagrass during the growth season. Colonized hollows were heavily grazed by brent geese and widgeon in autumn, converting these patches to a bare state again and disrupting sediment accretion by seagrass. In contrast, hummocks were covered by seagrass throughout the year and were rarely grazed, most likely because the waterfowl were not able to employ their preferred but water requiring feeding strategy (‘dabbling’) here. Our study exemplifies that interactions between ecosystem engineering by a foundation species (seagrass) and consumption (waterfowl grazing) can increase spatial complexity at the landscape level. PMID:22905115

  2. Species specific effects of three morphologically different belowground seagrasses on sediment properties

    NASA Astrophysics Data System (ADS)

    Rattanachot, Ekkalak; Prathep, Anchana

    2015-12-01

    Roots and rhizomes of seagrass play an important role in coastline zone by anchoring the substrate firmly which prevent resuspension and also controlling sediment biogeochemistry. The aim of this study was to compare the physical and chemical differences of sediments for 3 seagrass species, which have different root morphology between summer (February 2013) and the monsoon month (September 2013). Seven seagrass communities were studied and are: the mono stand of Halophila ovalis, Thalassia hemprichii, and Cymodocea rotundata, the mixed patches of H. ovalis with T. hemprichii, H. ovalis with C. rotundata, and T. hemprichii with C. rotundata and the mixed patches of 3 seagrass species. The roots of seagrasses were the main driver of differences in sediment properties; the branched, long root species, C. rotundata, showed an increasing redox potential by means of oxygen releasing from their roots. The unbranched, long root with dense root hair species, T. hemprichii, tended to cause more poorly sorted sediments. The carbon storage was also estimated and results showed a trend of higher organic carbon density was in the multispecific patches, the mono specific patches and bare sand, respectively. Season also influenced the sediment properties; high wave action in the monsoon stirred up the sediments, this led to lower organic carbon density and high redox potential. Our results suggest that the roots of seagrass species both increase and decrease sediment properties.

  3. 7 CFR 2902.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 15 2011-01-01 2011-01-01 false Bedding, bed linens, and towels. 2902.15 Section 2902... PROCUREMENT Designated Items § 2902.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  4. 7 CFR 3201.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 15 2013-01-01 2013-01-01 false Bedding, bed linens, and towels. 3201.15 Section 3201... PROCUREMENT Designated Items § 3201.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  5. 7 CFR 3201.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Bedding, bed linens, and towels. 3201.15 Section 3201... PROCUREMENT Designated Items § 3201.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  6. 7 CFR 2902.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Bedding, bed linens, and towels. 2902.15 Section 2902... PROCUREMENT Designated Items § 2902.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  7. 7 CFR 3201.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Bedding, bed linens, and towels. 3201.15 Section 3201... PROCUREMENT Designated Items § 3201.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  8. Metacognition and abstract reasoning.

    PubMed

    Markovits, Henry; Thompson, Valerie A; Brisson, Janie

    2015-05-01

    The nature of people's meta-representations of deductive reasoning is critical to understanding how people control their own reasoning processes. We conducted two studies to examine whether people have a metacognitive representation of abstract validity and whether familiarity alone acts as a separate metacognitive cue. In Study 1, participants were asked to make a series of (1) abstract conditional inferences, (2) concrete conditional inferences with premises having many potential alternative antecedents and thus specifically conducive to the production of responses consistent with conditional logic, or (3) concrete problems with premises having relatively few potential alternative antecedents. Participants gave confidence ratings after each inference. Results show that confidence ratings were positively correlated with logical performance on abstract problems and concrete problems with many potential alternatives, but not with concrete problems with content less conducive to normative responses. Confidence ratings were higher with few alternatives than for abstract content. Study 2 used a generation of contrary-to-fact alternatives task to improve levels of abstract logical performance. The resulting increase in logical performance was mirrored by increases in mean confidence ratings. Results provide evidence for a metacognitive representation based on logical validity, and show that familiarity acts as a separate metacognitive cue.

  9. Declines of seagrasses in a tropical harbour, North Queensland, Australia, are not the result of a single event.

    PubMed

    McKENNA, Skye; Jarvis, Jessie; Sankey, Tonia; Reason, Carissa; Coles, Robert; Rasheed, Michael

    2015-06-01

    A recent paper inferred that all seagrass in Cairns Harbour, tropical north-eastern Australia, had undergone 'complete and catastrophic loss' as a result of tropical cyclone Yasi in 2011. While we agree with the concern expressed, we would like to correct the suggestion that the declines were the result of a single climatic event and that all seagrass in Cairns Harbour were lost. Recent survey data and trend analysis from an on-ground monitoring program show that seagrasses in Cairns Harbour do remain, albeit at low levels, and the decline in seagrasses occurred over several years with cyclone Yasi having little additional impact. We have conducted annual on-ground surveys of seagrass distribution and the above-ground meadow biomass in Cairns Harbour and Trinity Inlet since 2001. This has shown a declining trend in biomass since a peak in 2004 and in area since it peaked in 2007. In 2012, seagrass area and above-ground biomass were significantly below the long-term (12 year) average but seagrass was still present. Declines were associated with regional impacts on coastal seagrasses from multiple years of above-average rainfall and severe storm and cyclone activity, similar to other nearby seagrass areas, and not as a result of a single event.

  10. Influence of New Zealand cockles (Austrovenus stutchburyi) on primary productivity in sandflat-seagrass (Zostera muelleri) ecotones

    NASA Astrophysics Data System (ADS)

    Lohrer, Andrew M.; Townsend, Michael; Hailes, Sa