Dissolution Dominating Calcification Process in Polar Pteropods Close to the Point of Aragonite Undersaturation

PubMed Central

Bednaršek, Nina; Tarling, Geraint A.; Bakker, Dorothee C. E.; Fielding, Sophie; Feely, Richard A.

2014-01-01

Thecosome pteropods are abundant upper-ocean zooplankton that build aragonite shells. Ocean acidification results in the lowering of aragonite saturation levels in the surface layers, and several incubation studies have shown that rates of calcification in these organisms decrease as a result. This study provides a weight-specific net calcification rate function for thecosome pteropods that includes both rates of dissolution and calcification over a range of plausible future aragonite saturation states (Ωar). We measured gross dissolution in the pteropod Limacina helicina antarctica in the Scotia Sea (Southern Ocean) by incubating living specimens across a range of aragonite saturation states for a maximum of 14 days. Specimens started dissolving almost immediately upon exposure to undersaturated conditions (Ωar∼0.8), losing 1.4% of shell mass per day. The observed rate of gross dissolution was different from that predicted by rate law kinetics of aragonite dissolution, in being higher at Ωar levels slightly above 1 and lower at Ωar levels of between 1 and 0.8. This indicates that shell mass is affected by even transitional levels of saturation, but there is, nevertheless, some partial means of protection for shells when in undersaturated conditions. A function for gross dissolution against Ωar derived from the present observations was compared to a function for gross calcification derived by a different study, and showed that dissolution became the dominating process even at Ωar levels close to 1, with net shell growth ceasing at an Ωar of 1.03. Gross dissolution increasingly dominated net change in shell mass as saturation levels decreased below 1. As well as influencing their viability, such dissolution of pteropod shells in the surface layers will result in slower sinking velocities and decreased carbon and carbonate fluxes to the deep ocean. PMID:25285916

Vulnerability of the paper Nautilus (Argonauta nodosa) shell to a climate-change ocean: potential for extinction by dissolution.

PubMed

Wolfe, Kennedy; Smith, Abigail M; Trimby, Patrick; Byrne, Maria

2012-10-01

Shell calcification in argonauts is unique. Only females of these cephalopods construct the paper nautilus shell, which is used as a brood chamber for developing embryos in the pelagic realm. As one of the thinnest (225 μm) known adult mollusc shells, and lacking an outer protective periostracum-like cover, this shell may be susceptible to dissolution as the ocean warms and decreases in pH. Vulnerability of the A. nodosa shell was investigated through immersion of shell fragments in multifactorial experiments of control (19 °C/pH 8.1; pCO(2) 419; Ω(Ca) = 4.23) and near-future conditions (24 °C/pH 7.8-7.6; pCO(2) 932-1525; Ω(Ca) = 2.72-1.55) for 14 days. More extreme pH treatments (pH 7.4-7.2; pCO(2) 2454-3882; Ω(Ca) = 1.20-0.67) were used to assess tipping points in shell dissolution. X-ray diffractometry revealed no change in mineralogy between untreated and treated shells. Reduced shell weight due to dissolution was evident in shells incubated at pH 7.8 (projected for 2070) after 14 days at control temperature, with increased dissolution in warmer and lower pH treatments. The greatest dissolution was recorded at 24 °C (projected for local waters by 2100) compared to control temperature across all low-pH treatments. Scanning electron microscopy revealed dissolution and etching of shell mineral in experimental treatments. In the absence of compensatory mineralization, the uncovered female brood chamber will be susceptible to dissolution as ocean pH decreases. Since the shell was a crucial adaptation for the evolution of the argonauts' holopelagic existence, persistence of A. nodosa may be compromised by shell dissolution in an ocean-change world.

Dissolution dominating calcification process in polar pteropods close to the point of aragonite undersaturation.

PubMed

Bednaršek, Nina; Tarling, Geraint A; Bakker, Dorothee C E; Fielding, Sophie; Feely, Richard A

2014-01-01

Thecosome pteropods are abundant upper-ocean zooplankton that build aragonite shells. Ocean acidification results in the lowering of aragonite saturation levels in the surface layers, and several incubation studies have shown that rates of calcification in these organisms decrease as a result. This study provides a weight-specific net calcification rate function for thecosome pteropods that includes both rates of dissolution and calcification over a range of plausible future aragonite saturation states (Ω(ar)). We measured gross dissolution in the pteropod Limacina helicina antarctica in the Scotia Sea (Southern Ocean) by incubating living specimens across a range of aragonite saturation states for a maximum of 14 days. Specimens started dissolving almost immediately upon exposure to undersaturated conditions (Ω(ar) ∼ 0.8), losing 1.4% of shell mass per day. The observed rate of gross dissolution was different from that predicted by rate law kinetics of aragonite dissolution, in being higher at Ω(ar) levels slightly above 1 and lower at Ω(ar) levels of between 1 and 0.8. This indicates that shell mass is affected by even transitional levels of saturation, but there is, nevertheless, some partial means of protection for shells when in undersaturated conditions. A function for gross dissolution against Ω(ar) derived from the present observations was compared to a function for gross calcification derived by a different study, and showed that dissolution became the dominating process even at Ω(ar) levels close to 1, with net shell growth ceasing at an Ω(ar) of 1.03. Gross dissolution increasingly dominated net change in shell mass as saturation levels decreased below 1. As well as influencing their viability, such dissolution of pteropod shells in the surface layers will result in slower sinking velocities and decreased carbon and carbonate fluxes to the deep ocean.

INTERACTIONS BETWEEN OCEAN ACIDIFICATION AND WARMING ON THE MORTALITY AND DISSOLUTION OF CORALLINE ALGAE(1).

PubMed

Diaz-Pulido, Guillermo; Anthony, Kenneth R N; Kline, David I; Dove, Sophie; Hoegh-Guldberg, Ove

2012-02-01

Coralline algae are among the most sensitive calcifying organisms to ocean acidification as a result of increased atmospheric carbon dioxide (pCO2 ). Little is known, however, about the combined impacts of increased pCO2 , ocean acidification, and sea surface temperature on tissue mortality and skeletal dissolution of coralline algae. To address this issue, we conducted factorial manipulative experiments of elevated CO2 and temperature and examined the consequences on tissue survival and skeletal dissolution of the crustose coralline alga (CCA) Porolithon (=Hydrolithon) onkodes (Heydr.) Foslie (Corallinaceae, Rhodophyta) on the southern Great Barrier Reef (GBR), Australia. We observed that warming amplified the negative effects of high pCO2 on the health of the algae: rates of advanced partial mortality of CCA increased from <1% to 9% under high CO2 (from 400 to 1,100 ppm) and exacerbated to 15% under warming conditions (from 26°C to 29°C). Furthermore, the effect of pCO2 on skeletal dissolution strongly depended on temperature. Dissolution of P. onkodes only occurred in the high-pCO2 treatment and was greater in the warm treatment. Enhanced skeletal dissolution was also associated with a significant increase in the abundance of endolithic algae. Our results demonstrate that P. onkodes is particularly sensitive to ocean acidification under warm conditions, suggesting that previous experiments focused on ocean acidification alone have underestimated the impact of future conditions on coralline algae. Given the central role that coralline algae play within coral reefs, these conclusions have serious ramifications for the integrity of coral-reef ecosystems. © 2011 Phycological Society of America.

Ocean acidification: Towards a better understanding of calcite dissolution

NASA Astrophysics Data System (ADS)

Wilhelmus, Monica M.; Adkins, Jess; Menemenlis, Dimitris

2016-11-01

The drastic increase of anthropogenic CO2 emissions over the past two centuries has altered the chemical structure of the ocean, acidifying upper ocean waters. The net impact of this pH decrease on marine ecosystems is still unclear, given the unprecedented rate at which CO2 is being released into the atmosphere. As part of the carbon cycle, calcium carbonate dissolution in sediments neutralizes CO2: phytoplankton at the surface produce carbonate minerals, which sink and reach the seafloor after the organisms die. On time scales of thousands of years, the calcium carbonate in these shells ultimately reacts with CO2 in seawater. Research in this field has been extensive; nevertheless, the dissolution rate law, the impact of boundary layer transport, and the feedback with the global ocean carbon cycle remain controversial. Here, we (i) develop a comprehensive numerical framework via 1D modeling of carbonate dissolution in sediments, (ii) approximate its impact on water column properties by implementing a polynomial approximation to the system's response into a global ocean biogeochemistry general circulation model (OBGCM), and (iii) examine the OBGCM sensitivity response to different formulations of sediment boundary layer properties. We find that, even though the burial equilibration time scales of calcium carbonate are in the order of thousands of years, the formulation of a bottom sediment model along with an improved description of the dissolution rate law can have consequences on multi-year to decadal time scales.

Community production modulates coral reef pH and the sensitivity of ecosystem calcification to ocean acidification

NASA Astrophysics Data System (ADS)

DeCarlo, Thomas M.; Cohen, Anne L.; Wong, George T. F.; Shiah, Fuh-Kwo; Lentz, Steven J.; Davis, Kristen A.; Shamberger, Kathryn E. F.; Lohmann, Pat

2017-01-01

Coral reefs are built of calcium carbonate (CaCO3) produced biogenically by a diversity of calcifying plants, animals, and microbes. As the ocean warms and acidifies, there is mounting concern that declining calcification rates could shift coral reef CaCO3 budgets from net accretion to net dissolution. We quantified net ecosystem calcification (NEC) and production (NEP) on Dongsha Atoll, northern South China Sea, over a 2 week period that included a transient bleaching event. Peak daytime pH on the wide, shallow reef flat during the nonbleaching period was ˜8.5, significantly elevated above that of the surrounding open ocean (˜8.0-8.1) as a consequence of daytime NEP (up to 112 mmol C m-2 h-1). Diurnal-averaged NEC was 390 ± 90 mmol CaCO3 m-2 d-1, higher than any other coral reef studied to date despite comparable calcifier cover (25%) and relatively high fleshy algal cover (19%). Coral bleaching linked to elevated temperatures significantly reduced daytime NEP by 29 mmol C m-2 h-1. pH on the reef flat declined by 0.2 units, causing a 40% reduction in NEC in the absence of pH changes in the surrounding open ocean. Our findings highlight the interactive relationship between carbonate chemistry of coral reef ecosystems and ecosystem production and calcification rates, which are in turn impacted by ocean warming. As open-ocean waters bathing coral reefs warm and acidify over the 21st century, the health and composition of reef benthic communities will play a major role in determining on-reef conditions that will in turn dictate the ecosystem response to climate change.

Effects of growth and dissolution on the fractionation of silicon isotopes by estuarine diatoms

NASA Astrophysics Data System (ADS)

Sun, Xiaole; Olofsson, Martin; Andersson, Per S.; Fry, Brian; Legrand, Catherine; Humborg, Christoph; Mörth, Carl-Magnus

2014-04-01

Studies of silicon (Si) isotope fractionation during diatom growth in open ocean systems have documented lower Si isotopic values (δ30Si) in the biogenic silica of diatom frustules compared to dissolved silicon. Recent findings also indicate that Si isotope fractionation occurs during dissolution of diatom frustules, producing higher δ30Si values in the remaining biogenic silica. This study focuses on diatoms from high production areas in estuarine and coastal areas that represent approximately 30-50% of the global marine primary production. Two species of diatoms, Thalassiosira baltica and Skeletonema marinoi, were isolated from the brackish Baltic Sea, one of the largest estuarine systems in the world. These species were used for laboratory investigations of Si isotope fractionation during diatom growth and the subsequent dissolution of the diatom frustules. Both species of diatoms give an identical Si isotope fractionation factor during growth of -1.50 ± 0.36‰ (2σ) for 30Si, which falls in the range of -2.09‰ to -0.55‰ of published data. Our results also suggest a dissolution-induced Si isotope fractionation factor of -0.86‰ at early stage of dissolution, but this effect was observed only in DSi and no significant Si isotope change was observed for BSi. The growth and dissolution results are applied to a Baltic Sea sediment core to reconstruct DSi utilization by diatoms, and found to be in agreement with the observed DSi uptake rates in the overlying water column during diatom growth.

Carbonate dissolution in mixed waters due to ocean acidification

NASA Astrophysics Data System (ADS)

Koski, K.; Wilson, J. L.

2009-12-01

Much of the anthropogenically released carbon dioxide has been stored as a dissolved gas in the ocean, causing a 0.1 decrease in ocean surface pH, with models predicting that by 2100 the surface ocean pH will be 0.5 below pre-industrial levels. In mixed ocean water - fresh water environments (e.g. estuaries, coastal aquifers, and edges of ice sheets), the decreased ocean pH couples with the mixed water geochemistry to make water more undersaturated with respect to calcium carbonate than ocean acidification alone. Mixed-water calcite dissolution may be one of the first directly observable effects of ocean acidification, as the ocean water and the fresh water can both be saturated with respect to calcium carbonate while their mixture will be undersaturated. We present a basic quantitative model describing mixed water dissolution in coastal or island freshwater aquifers, using temporally changing ocean pH, sea level, precipitation, and groundwater pumping. The model describes the potential for an increased rate of speleogenesis and porosity/permeability development along the lower edge of a fresh water lens aquifer. The model accounts the indirect effects of rising sea level and a growing coastal population on these processes. Applications are to freshwater carbonate aquifers on islands (e.g. the Bahamas) and in coastal areas (e.g. the unconfined Floridan aquifer of the United States, the Yucatan Peninsula of Mexico).

50 CFR 270.23 - Dissolution of Councils.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 11 2014-10-01 2014-10-01 false Dissolution of Councils. 270.23 Section 270.23 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC... § 270.23 Dissolution of Councils. (a) Petition for termination. (1) A petition to terminate a Council...

50 CFR 270.23 - Dissolution of Councils.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 9 2011-10-01 2011-10-01 false Dissolution of Councils. 270.23 Section 270.23 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC... § 270.23 Dissolution of Councils. (a) Petition for termination. (1) A petition to terminate a Council...

50 CFR 270.23 - Dissolution of Councils.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 11 2013-10-01 2013-10-01 false Dissolution of Councils. 270.23 Section 270.23 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC... § 270.23 Dissolution of Councils. (a) Petition for termination. (1) A petition to terminate a Council...

50 CFR 270.23 - Dissolution of Councils.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 11 2012-10-01 2012-10-01 false Dissolution of Councils. 270.23 Section 270.23 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC... § 270.23 Dissolution of Councils. (a) Petition for termination. (1) A petition to terminate a Council...

Ocean acidification and warming scenarios increase microbioerosion of coral skeletons.

PubMed

Reyes-Nivia, Catalina; Diaz-Pulido, Guillermo; Kline, David; Guldberg, Ove-Hoegh; Dove, Sophie

2013-06-01

Biological mediation of carbonate dissolution represents a fundamental component of the destructive forces acting on coral reef ecosystems. Whereas ocean acidification can increase dissolution of carbonate substrates, the combined impact of ocean acidification and warming on the microbioerosion of coral skeletons remains unknown. Here, we exposed skeletons of the reef-building corals, Porites cylindrica and Isopora cuneata, to present-day (Control: 400 μatm - 24 °C) and future pCO2 -temperature scenarios projected for the end of the century (Medium: +230 μatm - +2 °C; High: +610 μatm - +4 °C). Skeletons were also subjected to permanent darkness with initial sodium hypochlorite incubation, and natural light without sodium hypochlorite incubation to isolate the environmental effect of acidic seawater (i.e., Ωaragonite <1) from the biological effect of photosynthetic microborers. Our results indicated that skeletal dissolution is predominantly driven by photosynthetic microborers, as samples held in the dark did not decalcify. In contrast, dissolution of skeletons exposed to light increased under elevated pCO2 -temperature scenarios, with P. cylindrica experiencing higher dissolution rates per month (89%) than I. cuneata (46%) in the high treatment relative to control. The effects of future pCO2 -temperature scenarios on the structure of endolithic communities were only identified in P. cylindrica and were mostly associated with a higher abundance of the green algae Ostreobium spp. Enhanced skeletal dissolution was also associated with increased endolithic biomass and respiration under elevated pCO2 -temperature scenarios. Our results suggest that future projections of ocean acidification and warming will lead to increased rates of microbioerosion. However, the magnitude of bioerosion responses may depend on the structural properties of coral skeletons, with a range of implications for reef carbonate losses under warmer and more acidic oceans. © 2013 Blackwell Publishing Ltd.

Rate of production, dissolution and accumulation of biogenic solids in the ocean

NASA Technical Reports Server (NTRS)

Arrhenius, G.

1988-01-01

The equatorial current system, by its response to global circulation changes, provides a unique recording mechanism for long range climatic oscillations. A permanent record of the changes in rate of upwelling and organic production is generated in the equatorial deep sea sediments, particularly by such biogenic components which are unaffected by secondary dissolution. In order to determine the rates of accumulation of various sedimentary components, a reliable differential measurement of age of the strata must be obtained. Various approaches to this problem are reviewed, and sources of error discussed. Secondary dissolution of calcium carbonate introduces a substantial and variable difference between the dissolution-modified, and hence a priori unknown, rate of deposition on one hand and the rate of accumulation, derivable from the observed concentration, on the other. The cause and magnitude of these variations are of importance, particularly since some current dating schemes are based on assumed constancy in the rate of accumulation of this and, in some cases, also all other sedimentary components. The concepts used in rate evaluation are discussed with emphasis on the difference between the state of dissolution, an observable property of the sediment, and the rate of dissolution, a parameter that requires deduction of the carbonate fraction dissolved, and of the time differential. As a most likely cause of the enhanced state of dissolution of the interglacial carbonate sediments is proposed the lowered rates of biogenic production and deposition, which cause longer exposure of the carbonate microfossils to corrosion in the bioturbated surface layer of the sediment. Historical perspective is included in the discussion in view of the dedication of the Symposium to Hans Pettersson, the leader of the Swedish Deep Sea Expedition 1947-1948, an undertaking that opened a new era in deep sea research and planetary dynamics.

Nighttime dissolution in a temperate coastal ocean ecosystem increases under acidification

PubMed Central

Kwiatkowski, Lester; Gaylord, Brian; Hill, Tessa; Hosfelt, Jessica; Kroeker, Kristy J.; Nebuchina, Yana; Ninokawa, Aaron; Russell, Ann D.; Rivest, Emily B.; Sesboüé, Marine; Caldeira, Ken

2016-01-01

Anthropogenic emissions of carbon dioxide (CO2) are causing ocean acidification, lowering seawater aragonite (CaCO3) saturation state (Ωarag), with potentially substantial impacts on marine ecosystems over the 21st Century. Calcifying organisms have exhibited reduced calcification under lower saturation state conditions in aquaria. However, the in situ sensitivity of calcifying ecosystems to future ocean acidification remains unknown. Here we assess the community level sensitivity of calcification to local CO2-induced acidification caused by natural respiration in an unperturbed, biodiverse, temperate intertidal ecosystem. We find that on hourly timescales nighttime community calcification is strongly influenced by Ωarag, with greater net calcium carbonate dissolution under more acidic conditions. Daytime calcification however, is not detectably affected by Ωarag. If the short-term sensitivity of community calcification to Ωarag is representative of the long-term sensitivity to ocean acidification, nighttime dissolution in these intertidal ecosystems could more than double by 2050, with significant ecological and economic consequences. PMID:26987406

Distinct iron isotopic signatures and supply from marine sediment dissolution.

PubMed

Homoky, William B; John, Seth G; Conway, Tim M; Mills, Rachel A

2013-01-01

Oceanic iron inputs must be traced and quantified to learn how they affect primary productivity and climate. Chemical reduction of iron in continental margin sediments provides a substantial dissolved flux to the oceans, which is isotopically lighter than the crust, and so may be distinguished in seawater from other sources, such as wind-blown dust. However, heavy iron isotopes measured in seawater have recently led to the proposition of another source of dissolved iron from 'non-reductive' dissolution of continental margins. Here we present the first pore water iron isotope data from a passive-tectonic and semi-arid ocean margin (South Africa), which reveals a smaller and isotopically heavier flux of dissolved iron to seawater than active-tectonic and dysoxic continental margins. These data provide in situ evidence of non-reductive iron dissolution from a continental margin, and further show that geological and hydro-climatic factors may affect the amount and isotopic composition of iron entering the ocean.

Distinct iron isotopic signatures and supply from marine sediment dissolution

PubMed Central

Homoky, William B.; John, Seth G.; Conway, Tim M.; Mills, Rachel A.

2013-01-01

Oceanic iron inputs must be traced and quantified to learn how they affect primary productivity and climate. Chemical reduction of iron in continental margin sediments provides a substantial dissolved flux to the oceans, which is isotopically lighter than the crust, and so may be distinguished in seawater from other sources, such as wind-blown dust. However, heavy iron isotopes measured in seawater have recently led to the proposition of another source of dissolved iron from ‘non-reductive’ dissolution of continental margins. Here we present the first pore water iron isotope data from a passive-tectonic and semi-arid ocean margin (South Africa), which reveals a smaller and isotopically heavier flux of dissolved iron to seawater than active-tectonic and dysoxic continental margins. These data provide in situ evidence of non-reductive iron dissolution from a continental margin, and further show that geological and hydro-climatic factors may affect the amount and isotopic composition of iron entering the ocean. PMID:23868399

Nighttime dissolution in a temperate coastal ocean ecosystem increases under acidification.

PubMed

Kwiatkowski, Lester; Gaylord, Brian; Hill, Tessa; Hosfelt, Jessica; Kroeker, Kristy J; Nebuchina, Yana; Ninokawa, Aaron; Russell, Ann D; Rivest, Emily B; Sesboüé, Marine; Caldeira, Ken

2016-03-18

Anthropogenic emissions of carbon dioxide (CO2) are causing ocean acidification, lowering seawater aragonite (CaCO3) saturation state (Ω arag), with potentially substantial impacts on marine ecosystems over the 21(st) Century. Calcifying organisms have exhibited reduced calcification under lower saturation state conditions in aquaria. However, the in situ sensitivity of calcifying ecosystems to future ocean acidification remains unknown. Here we assess the community level sensitivity of calcification to local CO2-induced acidification caused by natural respiration in an unperturbed, biodiverse, temperate intertidal ecosystem. We find that on hourly timescales nighttime community calcification is strongly influenced by Ω arag, with greater net calcium carbonate dissolution under more acidic conditions. Daytime calcification however, is not detectably affected by Ω arag. If the short-term sensitivity of community calcification to Ω arag is representative of the long-term sensitivity to ocean acidification, nighttime dissolution in these intertidal ecosystems could more than double by 2050, with significant ecological and economic consequences.

Significance of a Shelf-wide Dissolution Event during the Paleocene-Eocene Thermal Maximum, Maryland and New Jersey, USA

NASA Astrophysics Data System (ADS)

Bralower, T. J.; Kump, L. R.; Robinson, M. M.; Self-Trail, J. M.; Zachos, J. C.

2016-12-01

Continental-shelf sediments of the US Atlantic margin experienced a brief episode of carbonate dissolution during the onset of the Paleocene-Eocene Thermal Maximum (PETM). Dissolution is represented by reduced percentages of carbonate, and calcareous microfossil distribution and preservation trends, in cores from Maryland and New Jersey. The base and the top of the dissolution zone are abrupt compared to the gradual nature of the onset of the carbon isotope excursion (CIE). The thickness of the dissolution zone varies from 9 cm in the Bass River core (outer paleoshelf) to 1.6 m in the CamDor core (middle paleoshelf). The decrease in %CaCO3 suggests dissolution locally removed 83 to 100% of the initial biogenic carbonate. Shelf-wide dissolution during the onset of the PETM may be a regional event, associated, for example, with eutrophication. Samples from across the paleoshelf contain abundant fine-grained framboidal pyrite, which suggests photic-zone euxinia occurred before, during, and after the dissolution event. Dissolution may also be associated with oxidation of this pyrite during later exposure to oxidizing groundwaters, although the restricted duration of the dissolution interval argues against this. Alternatively, the dissolution event may have global significance related to surface ocean-water acidification or shoaling of the calcite compensation depth (CCD) to shelf depths. The event began near the onset of the CIE on the shelf, whereas dissolution in deep-sea sections began later. Earlier shelf dissolution is consistent with surface ocean acidification while later deep-sea dissolution is thought to be associated with shoaling of the CCD. In our presentation, we weigh evidence for each of these possibilities and test them using the global dataset.

Impacts of seawater saturation state (ΩA = 0.4-4.6) and temperature (10, 25 °C) on the dissolution kinetics of whole-shell biogenic carbonates

NASA Astrophysics Data System (ADS)

Ries, Justin B.; Ghazaleh, Maite N.; Connolly, Brian; Westfield, Isaac; Castillo, Karl D.

2016-11-01

Anthropogenic increase of atmospheric pCO2 since the Industrial Revolution has caused seawater pH to decrease and seawater temperatures to increase-trends that are expected to continue into the foreseeable future. Myriad experimental studies have investigated the impacts of ocean acidification and warming on marine calcifiers' ability to build protective shells and skeletons. No studies, however, have investigated the combined impacts of ocean acidification and warming on the whole-shell dissolution kinetics of biogenic carbonates. Here, we present the results of experiments designed to investigate the effects of seawater saturation state (ΩA = 0.4-4.6) and temperature (10, 25 °C) on gross rates of whole-shell dissolution for ten species of benthic marine calcifiers: the oyster Crassostrea virginica, the ivory barnacle Balanus eburneus, the blue mussel Mytilus edulis, the conch Strombus alatus, the tropical coral Siderastrea siderea, the temperate coral Oculina arbuscula, the hard clam Mercenaria mercenaria, the soft clam Mya arenaria, the branching bryozoan Schizoporella errata, and the coralline red alga Neogoniolithon sp. These experiments confirm that dissolution rates of whole-shell biogenic carbonates decrease with calcium carbonate (CaCO3) saturation state, increase with temperature, and vary predictably with respect to the relative solubility of the calcifiers' polymorph mineralogy [high-Mg calcite (mol% Mg > 4) ≥ aragonite > low-Mg calcite (mol% Mg < 4)], consistent with prior studies on sedimentary and inorganic carbonates. Furthermore, the severity of the temperature effects on gross dissolution rates also varied with respect to carbonate polymorph solubility, with warming (10-25 °C) exerting the greatest effect on biogenic high-Mg calcite, an intermediate effect on biogenic aragonite, and the least effect on biogenic low-Mg calcite. These results indicate that both ocean acidification and warming will lead to increased dissolution of biogenic carbonates in future oceans, with shells/skeletons composed of the more soluble polymorphs of CaCO3 being the most vulnerable to these stressors. The effects of saturation state and temperature on gross shell dissolution rate were modeled with an exponential asymptotic function (y =B0 -B2 ·e B1 Ω) that appeals to the general Arrhenius-derived rate equation for mineral dissolution [ r = (C ·e -Ea / RT) (1 - Ω)n]. Although the dissolution curves for the investigated biogenic CaCO3 exhibited exponential asymptotic trends similar to those of inorganic CaCO3, the observation that gross dissolution of whole-shell biogenic CaCO3 occurred (albeit at lower rates) even in treatments that were oversaturated (Ω > 1) with respect to both aragonite and calcite reveals fundamental differences between the dissolution kinetics of whole-shell biogenic CaCO3 and inorganic CaCO3. Thus, applying stoichiometric solubility products derived for inorganic CaCO3 to model gross dissolution of biogenic carbonates may substantially underestimate the impacts of ocean acidification on net calcification (gross calcification minus gross dissolution) of systems ranging in scale from individual organisms to entire ecosystems (e.g., net ecosystem calcification). Finally, these experiments permit rough estimation of the impact of CO2-induced ocean acidification on the gross calcification rates of various marine calcifiers, calculated as the difference between net calcification rates derived empirically in prior studies and gross dissolution rates derived from the present study. Organisms' gross calcification responses to acidification were generally less severe than their net calcification response patterns, with aragonite mollusks (bivalves, gastropods) exhibiting the most negative gross calcification response to acidification, and photosynthesizing organisms, including corals and coralline red algae, exhibiting relative resilience.

Atmospheric Dissolved Iron Depostiion to the Global Oceans: Effects of Oxalate-Promoted Fe Dissolution, Photochemical Redox Cycling, and Dust Mineralogy

NASA Technical Reports Server (NTRS)

Johnson, M. S.; Meskhidze, N.

2013-01-01

Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of windblown dust from the major desert regions. Our calculations suggest that during the yearlong simulation is approximately 0.26 Tg (1 Tg = 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by approximately 75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model simulations also show that atmospheric fluxes of Fed can be strongly influenced by the mineralogy of Fe-containing compounds. This study shows that Fed deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the explicit model representation of individual processes leading to Fed production within mineral dust are needed to improve the understanding of the atmospheric Fe cycle, and quantify the effect of dust-Fe on ocean biological productivity, carbon cycle, and climate.

Comment on Peck et al: Vulnerability of pteropod (Limacina helicina) to ocean acidification: shell dissolution occurs despite an intact organic layer

NASA Astrophysics Data System (ADS)

Bednaršek, N.; Johnson, J.; Feely, R. A.

2016-05-01

Pteropods have been recognized as one of the most sensitive marine organisms to ocean acidification (OA). Their susceptibility is mostly related to rapid shell dissolution, which is correlated with exposure to waters undersaturated with respect to aragonite (Ωar≤ 1) (e.g., Lischka et al., 2011; Bednaršek et al., 2012a,b, 2014a,b; Busch et al., 2014). Increased dissolution weakens the shell, increases vulnerability to predation and infection, and imposes an energetic cost. The rapidity of shell dissolution is attributed to the combination of metastable aragonitic crystal structure of shells that are among the thinnest known for calcifying organisms, and an extremely thin outer organic layer (i.e. periostracum <1 μm thick), suggesting insufficient protection against shell dissolution at Ωar≤1 (Bednaršek et al., 2014b). The periostracum generally consists of polysaccharide and proteinaceous components (Gaffey and Bronnimann, 1993) but varies significantly in its structure and composition amongst taxa.

Equatorial Pacific Productivity Events and Intervals in the Middle and late Miocene through XRF-Scanned Bulk Sediment Composition Data

NASA Astrophysics Data System (ADS)

Lyle, M. W.; Stepanova, A.; Wilson, J. K.; Marcantonio, F.

2014-12-01

The equatorial Pacific is the largest open ocean productivity center, responsible for nearly half of global marine new production and about 40% of CaCO3 burial. Understanding how the equatorial Pacific upwelling system has evolved over the Neogene is critical to understand the evolution of the global carbon cycle. We know from reconnaissance studies that productivity in equatorial Pacific surface waters as well as dissolution driven by deep waters have strongly affected the sediment record. We have used calibrated XRF scanning to capture anomalies in equatorial Pacific upwelling and productivity at Milankovitch-resolving resolution since the early Miocene. The 8 elements calibrated in the XRF scans can be used to distinguish intervals of high carbonate dissolution from those of high productivity. Carbonate dissolution intervals are recorded by a drop of CaCO3 relative to Aeolian clays, with little change in the ratio between estimated opal and clay (estimated by TiO2). In contrast, high production intervals have high opal/TiO2 and low CaCO3. Low CaCO3 contents are caused partly by dilution, since high production skews tropical particulate rain to be more opal-rich relative to carbonate, and additional C-org rain can help to increase CaCO3 dissolution within near-surface sediments. We observe long-lived high production anomalies modulated by orbitally-driven climate variability. Prominent intervals are found at the end of the Miocene climate optimum (~ 14 Ma), interspersed with dissolution intervals in the Carbonate Crash interval (~9-11 Ma), and in the Biogenic Bloom interval (8-4.5 Ma). Using relationships among biogenic fluxes in modern equatorial sediment trap studies, especially the positive correlations between biogenic Ba , C-org, and CaCO3 fluxes, we find that the highest production intervals have much higher opal/C-org in the particulate rain, implying an inefficient carbon pump to the deep ocean. If confirmed, productivity was not as strong a feedback to atmospheric CO2 in the Miocene as it is in the Holocene.

Secondary calcification and dissolution respond differently to future ocean conditions

NASA Astrophysics Data System (ADS)

Silbiger, N. J.; Donahue, M. J.

2015-01-01

Climate change threatens both the accretion and erosion processes that sustain coral reefs. Secondary calcification, bioerosion, and reef dissolution are integral to the structural complexity and long-term persistence of coral reefs, yet these processes have received less research attention than reef accretion by corals. In this study, we use climate scenarios from RCP 8.5 to examine the combined effects of rising ocean acidity and sea surface temperature (SST) on both secondary calcification and dissolution rates of a natural coral rubble community using a flow-through aquarium system. We found that secondary reef calcification and dissolution responded differently to the combined effect of pCO2 and temperature. Calcification had a non-linear response to the combined effect of pCO2 and temperature: the highest calcification rate occurred slightly above ambient conditions and the lowest calcification rate was in the highest temperature-pCO2 condition. In contrast, dissolution increased linearly with temperature-pCO2 . The rubble community switched from net calcification to net dissolution at +271 μatm pCO2 and 0.75 °C above ambient conditions, suggesting that rubble reefs may shift from net calcification to net dissolution before the end of the century. Our results indicate that (i) dissolution may be more sensitive to climate change than calcification and (ii) that calcification and dissolution have different functional responses to climate stressors; this highlights the need to study the effects of climate stressors on both calcification and dissolution to predict future changes in coral reefs.

Secondary calcification and dissolution respond differently to future ocean conditions

NASA Astrophysics Data System (ADS)

Silbiger, N. J.; Donahue, M. J.

2014-09-01

Climate change threatens both the accretion and erosion processes that sustain coral reefs. Secondary calcification, bioerosion, and reef dissolution are integral to the structural complexity and long-term persistence of coral reefs, yet these processes have received less research attention than reef accretion by corals. In this study, we use climate scenarios from RCP8.5 to examine the combined effects of rising ocean acidity and SST on both secondary calcification and dissolution rates of a natural coral rubble community using a flow-through aquarium system. We found that secondary reef calcification and dissolution responded differently to the combined effect of pCO2 and temperature. Calcification had a non-linear response to the combined effect of pCO2-temperature: the highest calcification rate occurred slightly above ambient conditions and the lowest calcification rate was in the highest pCO2-temperature condition. In contrast, dissolution increased linearly with pCO2-temperature. The rubble community switched from net calcification to net dissolution at +272 μatm pCO2 and 0.84 °C above ambient conditions, suggesting that rubble reefs may shift from net calcification to net dissolution before the end of the century. Our results indicate that dissolution may be more sensitive to climate change than calcification, and that calcification and dissolution have different functional responses to climate stressors, highlighting the need to study the effects of climate stressors on both calcification and dissolution to predict future changes in coral reefs.

Global Modeling Study of the Bioavailable Atmospheric Iron Supply to the Global Ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, S.; Krol, M. C.; van Noije, T.; Le Sager, P.

2017-12-01

Atmospheric deposition of trace constituents acts as a nutrient source to the open ocean and affect marine ecosystem. Dust is known as a major source of nutrients to the global ocean, but only a fraction of these nutrients is released in a bioavailable form that can be assimilated by the marine biota. Iron (Fe) is a key micronutrient that significantly modulates gross primary production in the High-Nutrient-Low-Chlorophyll (HNLC) oceans, where macronutrients like nitrate are abundant, but primary production is limited by Fe scarcity. The global atmospheric Fe cycle is here parameterized in the state-of-the-art global Earth System Model EC-Earth. The model takes into account the primary emissions of both insoluble and soluble Fe forms, associated with mineral dust and combustion aerosols. The impact of atmospheric acidity and organic ligands on mineral dissolution processes, is parameterized based on updated experimental and theoretical findings. Model results are also evaluated against available observations. Overall, the link between the labile Fe atmospheric deposition and atmospheric composition changes is here demonstrated and quantified. This work has been financed by the Marie-Curie H2020-MSCA-IF-2015 grant (ID 705652) ODEON (Online DEposition over OceaNs; modeling the effect of air pollution on ocean bio-geochemistry in an Earth System Model).

Foraminifer Shell Weight and Fragmentation: A Quantitative Study of the Influence of Temperature, [CO32-] and Dissolution on Proxies of the Marine Carbonate System

NASA Astrophysics Data System (ADS)

Mekik, F.; Pourmand, A.; Ward, B. M.

2015-12-01

Quantifying the various components of the marine carbonate system is important for understanding anthropogenic ocean acidification, and the rates and magnitudes of ocean acidification/ alkalization events in Earth's past. We performed multiple statistical analyses (factor analysis, partial correlations, multiple regression analysis and independent samples t -tests) on core top data using the Globorotalia menardii fragmentation index (MFI) in 89 core tops from across the tropical Pacific, Atlantic and Indian Oceans, the fragmentation trend of four species of foraminifers (Globorotalia truncatulinoides, G. menardii, Neogloboquadrina dutertrei and Pulleniatina obliquiloculata) in the EEP, tropical Atlantic and tropical Indian Ocean core tops, and Globorotalia menardii shell weight in a suite of 25 core tops the EEP in order to isolate the effects of surface ocean parameters such as temperature and [CO32-] from dissolution in sediments. Surface ocean parameters showed no significant effect on the G. menardii fragmentation index. We found no statistically significant influence of habitat water temperature or [CO32-] on foraminifer fragmentation in any of four species. While we found a strong influence of habitat water [CO32-] on the size normalized shell weight proxy in N. dutertrei and Pulleniatina obliquiloculata in our previous work, we found a much reduced influence of [CO32-] on the shell weight of G. menardii, which is most influenced by shell dissolution.

Taking the metabolic pulse of the world's coral reefs.

PubMed

Cyronak, Tyler; Andersson, Andreas J; Langdon, Chris; Albright, Rebecca; Bates, Nicholas R; Caldeira, Ken; Carlton, Renee; Corredor, Jorge E; Dunbar, Rob B; Enochs, Ian; Erez, Jonathan; Eyre, Bradley D; Gattuso, Jean-Pierre; Gledhill, Dwight; Kayanne, Hajime; Kline, David I; Koweek, David A; Lantz, Coulson; Lazar, Boaz; Manzello, Derek; McMahon, Ashly; Meléndez, Melissa; Page, Heather N; Santos, Isaac R; Schulz, Kai G; Shaw, Emily; Silverman, Jacob; Suzuki, Atsushi; Teneva, Lida; Watanabe, Atsushi; Yamamoto, Shoji

2018-01-01

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems.

Taking the metabolic pulse of the world’s coral reefs

PubMed Central

Andersson, Andreas J.; Langdon, Chris; Albright, Rebecca; Bates, Nicholas R.; Caldeira, Ken; Carlton, Renee; Corredor, Jorge E.; Dunbar, Rob B.; Enochs, Ian; Erez, Jonathan; Eyre, Bradley D.; Gattuso, Jean-Pierre; Gledhill, Dwight; Kayanne, Hajime; Kline, David I.; Koweek, David A.; Lantz, Coulson; Lazar, Boaz; Manzello, Derek; McMahon, Ashly; Meléndez, Melissa; Page, Heather N.; Santos, Isaac R.; Schulz, Kai G.; Shaw, Emily; Silverman, Jacob; Suzuki, Atsushi; Teneva, Lida; Watanabe, Atsushi; Yamamoto, Shoji

2018-01-01

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems. PMID:29315312

Planktic foraminifera form their shells by attachment of metastable carbonate particles

NASA Astrophysics Data System (ADS)

Wirth, R.; Jacob, D. E.; Eggins, S.

2016-12-01

Planktic foraminifera shells contribute up to half the inorganic carbon exported from the surface ocean to the seafloor. Their tiny calcium carbonate shells are preserved in sediments as calcite, and provide our most valuable geochemical archive of changes surface ocean conditions and climate spanning the last 100 million years. Here we show the shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei consist of nano-particulate vaterite and amorphous calcium carbonate. This indicates formation via a non-classical crystallization pathway involving metastable carbonate intermediate phases before transforming to calcite, and requires a new perspective on how geochemical proxies are incorporated into planktic foraminifer shells. Our findings indicate planktic foraminifer shells could be far more susceptible to dissolution and ocean acidification than previously thought, and account for unexpected shell dissolution above the calcite saturation horizon in the ocean, which is a major uncertainty in modelling oceanic carbon fluxes.

Solar Radiation Management and Olivine Dissolution Methods in Climate Engineering

NASA Astrophysics Data System (ADS)

Kone, S.

2014-12-01

An overview of solar radiation management and olivine dissolution methods allows to discuss, comparatively, the benefits and consequences of these two geoengineering techniques. The combination of those two techniques allows to concomitantly act on the two main agents intervening in global warming: solar radiation and carbon dioxide. The earth surface temperature increases due mainly to carbon dioxide (a greenhouse gas) that keeps the solar radiation and causes the global warming. Two complementary methods to mitigate climate change are overviewed: SRM method, which uses injected aerosols, aims to reduce the amount of the inbound solar radiation in atmosphere; and olivine dissolution in water, a key chemical reaction envisaged in climate engineering , aiming to reduce the amount of the carbon dioxide in extracting it from atmosphere. The SRM method works on scenarios of solar radiation decrease and the olivine dissolution method works as a carbon dioxide sequestration method. Olivine dissolution in water impacts negatively on the pH of rivers but positively in counteracting ocean acidification and in transporting the silica in ocean, which has benefits for diatom shell formation.

Influence of variable rates of neritic carbonate deposition on atmospheric carbon dioxide and pelagic sediments

NASA Technical Reports Server (NTRS)

Walker, J. C.; Opdyke, B. C.

1995-01-01

Short-term imbalances in the global cycle of shallow water calcium carbonate deposition and dissolution may be responsible for much of the observed Pleistocene change in atmospheric carbon dioxide content. However, any proposed changes in the alkalinity balance of the ocean must be reconciled with the sedimentary record of deep-sea carbonates. The possible magnitude of the effect of shallow water carbonate deposition on the dissolution of pelagic carbonate can be tested using numerical simulations of the global carbon cycle. Boundary conditions can be defined by using extant shallow water carbonate accumulation data and pelagic carbonate deposition/dissolution data. On timescales of thousands of years carbonate deposition versus dissolution is rarely out of equilibrium by more than 1.5 x 10(13) mole yr-1. Results indicate that the carbonate chemistry of the ocean is rarely at equilibrium on timescales less than 10 ka. This disequilibrium is probably due to sea level-induced changes in shallow water calcium carbonate deposition/dissolution, an interpretation that does not conflict with pelagic sedimentary data from the central Pacific.

Interannual sedimentary effluxes of alkalinity in the southern North Sea: model results compared with summer observations

NASA Astrophysics Data System (ADS)

Pätsch, Johannes; Kühn, Wilfried; Dorothea Six, Katharina

2018-06-01

For the sediments of the central and southern North Sea different sources of alkalinity generation are quantified by a regional modelling system for the period 2000-2014. For this purpose a formerly global ocean sediment model coupled with a pelagic ecosystem model is adapted to shelf sea dynamics, where much larger turnover rates than in the open and deep ocean occur. To track alkalinity changes due to different nitrogen-related processes, the open ocean sediment model was extended by the state variables particulate organic nitrogen (PON) and ammonium. Directly measured alkalinity fluxes and those derived from Ra isotope flux observation from the sediment into the pelagic are reproduced by the model system, but calcite building and calcite dissolution are underestimated. Both fluxes cancel out in terms of alkalinity generation and consumption. Other simulated processes altering alkalinity in the sediment, like net sulfate reduction, denitrification, nitrification, and aerobic degradation, are quantified and compare well with corresponding fluxes derived from observations. Most of these fluxes exhibit a strong positive gradient from the open North Sea to the coast, where large rivers drain nutrients and organic matter. Atmospheric nitrogen deposition also shows a positive gradient from the open sea towards land and supports alkalinity generation in the sediments. An additional source of spatial variability is introduced by the use of a 3-D heterogenous porosity field. Due to realistic porosity variations (0.3-0.5) the alkalinity fluxes vary by about 4 %. The strongest impact on interannual variations of alkalinity fluxes is exhibited by the temporal varying nitrogen inputs from large rivers directly governing the nitrate concentrations in the coastal bottom water, thus providing nitrate necessary for benthic denitrification. Over the time investigated the alkalinity effluxes decrease due to the decrease in the nitrogen supply by the rivers.

Global charcoal mobilization from soils via dissolution and riverine transport to the oceans

Treesearch

Rudolf Jaffe; Yan Ding; Jutta Niggemann; Anssi V. Vahatalo; Aron Stubbins; Robert G. M. Spencer; John Campbell; Thorsten Dittmar

2013-01-01

Global biomass burning generates 40 million to 250 million tons of charcoal every year, part of which is preserved for millennia in soils and sediments. We have quantified dissolution products of charcoal in a wide range of rivers worldwide and show that globally, a major portion of the annual charcoal production is lost from soils via dissolution and subsequent...

50 CFR 270.23 - Dissolution of Councils.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Dissolution of Councils. 270.23 Section 270.23 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE FISH AND SEAFOOD PROMOTION SPECIES-SPECIFIC SEAFOOD MARKETING COUNCILS...

Global charcoal mobilization from soils via dissolution and riverine transport to the oceans.

PubMed

Jaffé, Rudolf; Ding, Yan; Niggemann, Jutta; Vähätalo, Anssi V; Stubbins, Aron; Spencer, Robert G M; Campbell, John; Dittmar, Thorsten

2013-04-19

Global biomass burning generates 40 million to 250 million tons of charcoal every year, part of which is preserved for millennia in soils and sediments. We have quantified dissolution products of charcoal in a wide range of rivers worldwide and show that globally, a major portion of the annual charcoal production is lost from soils via dissolution and subsequent transport to the ocean. The global flux of soluble charcoal accounts to 26.5 ± 1.8 million tons per year, which is ~10% of the global riverine flux of dissolved organic carbon (DOC). We suggest that the mobilization of charcoal and DOC out of soils is mechanistically coupled. This study closes a major gap in the global charcoal budget and provides critical information in the context of geoengineering.

Rethinking CCD's Significance in Estimating Late Neogene Whole Ocean Carbonate Budget

NASA Astrophysics Data System (ADS)

Si, W.; Rosenthal, Y.

2017-12-01

The global averaged calcite compensation depth (CCD) record is conventionally used to reconstruct two correlatable parameters of the carbonate system - the alkalinity budget of the ocean and/or the saturation state of the ocean. Accordingly, the available CCD reconstructions have been interpreted to suggest either relative stable (Pearson and Palmer, 2000) or increased alkalinity of the ocean over the past 15 Ma (Tyrrell and Zeebe, 2004; Pälike et al., 2012). However, CCD alone is insufficient to constrain the carbonate system because the weathering flux of alkalinity into the ocean is not only balanced by CaCO3 dissolution on the seafloor but also by the biologic production in the euphotic zone and, the CCD records cannot be readily interpreted as changes in either process. Here, we present evidence of the co-evolution of surface CaCO3 production and deepsea dissolution through the late Neogene. By examining separately the mass accumulation rates (MAR) of coccoliths, planktonic foraminifera, and quantifying dissolution (using a proxy revised from Broecker et al., 1999) in seventeen deepsea cores from multiple depth-transects, we find that 1) MAR of dissolution-resistant coccoliths was substantially higher in the mid Miocene and declining on a global scale towards the present; 2) unlike coccoliths, MAR of planktonic foraminifera, shows no apparent secular trend through that time; 3) the revised dissolution index, shows significantly improved preservation of planktonic foraminiferal shells over that time, particularly at intermediate water depth and exhibits close association between changes in preservation with key climatic events. Our new records have two immediate implications. First, the substantially weakened pelagic biogenic carbonate production from mid Miocene to present alone could account for the improved preservation of deepsea carbonates without calling for a scenario of increased weathering input. Second, with the constrain of global averaged CCD records, the net accumulation of pelagic carbonate has declined over the course of late Neogene. Hence, the weathering alkalinity input should have decreased since 15 Ma, as oppose to the weathering hypothesis (Raymo et al., 1988).

Limited Carbonate Dissolution by Boring Microflora at Two Volcanically Acidified Temperate Sites: Ischia (Italy, Mediterranean Sea) and Faial (Azores, NE Atlantic Ocean)

NASA Astrophysics Data System (ADS)

Tribollet, A.; Grange, J. S.; Parra, H.; Rodolfo-Metalpa, R.; Carreiro-Silva, M.

2018-01-01

In situ effects of ocean acidification on carbonate dissolution by microboring flora, also called biogenic dissolution, have only been studied once in tropical environments. Naturally acidified seawaters due to CO2 vents offer a perfect setting to study these effects in temperate systems. Three sites were selected at Ischia (Italy, Mediterranean Sea) with one experiencing ambient pH and the two others a mean pHT of 7.2 and 7.5. At Faial (Azores, NE Atlantic), one site with ambient pH and one acidified site with a mean pHT of 7.4 were selected. Experiments were carried out during 1.5 months and 6 months in Azores and Ischia, respectively, to determine the effects of OA on microboring communities in various carbonate substrates. Low pH influenced negatively boring microflora development by limiting their depth of penetration and abundance in substrates. Biogenic dissolution was thus reduced by a factor 3 to 7 depending on sites and substrate types. At sites with ambient pH in Faial, biogenic dissolution contributed up to 23% to the total weight loss, while it contributed less than 1% to the total weight loss of substrates at the acidified sites. Most of the dissolution at these sites was due to chemical dissolution (often Ω ≤ 1). Such conditions maintained microboring communities at a pioneer stage with a limited depth of penetration in substrates. Our results, together with previous findings that showed an increase of biogenic dissolution at pH > 7.7, suggest that there is a pH tipping point below which microborer development and thus carbonate biogenic dissolution is strongly limited.

Dissolution of methane bubbles with hydrate armoring in deep ocean conditions

NASA Astrophysics Data System (ADS)

Kovalchuk, Margarita; Socolofsky, Scott

2017-11-01

The deep ocean is a storehouse of natural gas. Methane bubble moving upwards from marine sediments may become trapped in gas hydrates. It is uncertain precisely how hydrate armoring affects dissolution, or mass transfer from the bubble to the surrounding water column. The Texas A&M Oilspill Calculator was used to simulate a series of gas bubble dissolution experiments conducted in the United States Department of Energy National Energy Technology Laboratory High Pressure Water Tunnel. Several variations of the mass transfer coefficient were calculated based on gas or hydrate phase solubility and clean or dirty bubble correlations. Results suggest the mass transfer coefficient may be most closely modeled with gas phase solubility and dirty bubble correlation equations. Further investigation of hydrate bubble dissolution behavior will refine current numeric models which aid in understanding gas flux to the atmosphere and plumes such as oil spills. Research funded in part by the Texas A&M University 2017 Undergraduate Summer Research Grant and a Grant from the Methane Gas Hydrates Program of the US DOE National Energy Technology Laboratory.

Dissolution Rates of Biogenic Carbonate Sediments from the Bermuda Platform

NASA Astrophysics Data System (ADS)

Finlay, A. J.; Andersson, A. J.

2016-02-01

The contribution of biogenic carbonate sediment dissolution rates to overall net reef accretion/erosion (under both present and future oceanic pCO2 levels) has been strikingly neglected, despite experimental results indicating that sediment dissolution might be more sensitive to ocean acidification (OA) than calcification. Dissolution of carbonate sediments could impact net reef accretion rates as well as the formation and preservation of valuable marine and terrestrial ecosystems. Bulk sediment dissolution rates of samples from the Bermuda carbonate platform were measured in natural seawater at pCO2 values ranging from approximately 3500 μatm to 9000 μatm. This range of pCO2 levels incorporates values currently observed in porewaters on the Bermuda carbonate platform as well as a potential future increase in porewater pCO2 levels due to OA. Sediment samples from two different stations on the reef platform were analyzed for grain size and mineralogy. Dissolution rates of sediments in the dominant grain size fraction of the platform (500-1000 μm) from both stations ranged between 16.25 and 47.19 (± 0.27 to 0.79) μmoles g-1 hr-1 and are comparable to rates previously obtained from laboratory experiments on other natural carbonate sediments. At a pCO2 of 3500 μatm, rates from both samples were similar, despite their differing mineralogy. However, at pCO2 levels above 3500 μatm, the sediment sample with a greater weight percent of Mg-calcite had slightly higher dissolution rates. Despite many laboratory studies on biogenic carbonate dissolution, a significant disparity still exists between laboratory measurements and field observations. Performing additional controlled, laboratory experiments on natural sediment may help to elucidate the reasons for this disparity.

Effect of Mineralogy on Dissolution and Speciation of Iron Containing Mineral Oxides in Atmospheric Aerosol Dust

NASA Astrophysics Data System (ADS)

Hettiarachchi, E.; Rubasinghege, G. R. S.; Reynolds, R. L.; Goldstein, H. L.; Moskowitz, B. M.

2017-12-01

Iron is one of the important trace elements for the life. Though it is the fourth most abundant element in the terrestrial crust, given higher pH ( 8.5) in the ocean, the direct dissolution of iron from the Earth crust is limited. Despite this limitation, ocean contains about 2 nM of dissolved iron that is 20-fold greater. Therefore, it is hypothesized most iron comes to the ocean via atmosphere, and dissolution occurs in the acidic atmospheric environments. The current work focuses on the effect of minerology on atmospheric processing of Fe-containing mineral dust using four authentic dust samples, collected from different parts of the world, along with three model systems, hematite (α-Fe2O3), magnetite (Fe3O4) and ilmenite (FeTiO3). Here, spectroscopic methods are combined with batch reactor studies to investigate total iron dissolution and speciation, with a specific focus on source material i.e. particle size, mineralogy, and environmental conditions, i.e. pH, temperature and solar flux. Our data suggests that the presence of Ti metal enhances the dissolution of iron regardless the total %Fe in the mineral. The surface area normalized total iron dissolution in ilmenite, under the dark conditions, in the presence of nitric acid (HNO3) is 3-fold higher than that of hematite. In authentic samples, similar effects were observed for samples containing %Ti. Further, 74% of the dissolved iron in ilmenite remained as Fe(II), bioavailable iron, whereas it was only 60% for magnetite and 8% for hematite. In this study, these results were used to interpret similar trends observed for authentic dust samples with high magnetite content. Thus, the findings of the current study highlight important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol.

Investigation of the late summer Si-budget in the Sub-Antarctic and Polar Front Zones south of Tasmania (SAZ-SENSE)

NASA Astrophysics Data System (ADS)

Fripiat, F.; Leblanc, K.; Elskens, M.; Quéguiner, B.; Armand, L.; Cornet-Barthaux, V.; André, L.; Cardinal, D.

2009-04-01

In the surface ocean, the Si-biogeochemical budget can be estimated by the ratio between the integrated biogenic silica dissolution and production rates. However such data are scarce in the ocean mostly because of methodology limitation. This is especially true in the Sub-Antarctic Zone (SAZ) where only two profiles were measured so far, exhibiting large variation (dissolution: production ratio of 0.3 and 3.1 for spring and summer, respectively). Though, the SAZ plays a crucial role in the efficiency of the silicate pump and the fertility of the Sub-Antarctic Mode Waters which then replenish in nutrients the majority of the surface waters of the world ocean. Therefore, better constraining the dissolution: production ratios in this region will certainly improve our understanding of these processes. During the SAZ-SENSE cruise (Jan.-Feb. 2007), the Si-budget of three stations (two in the SAZ and one in the Polar Frontal Zone, PFZ, for a total of nine profiles) covering different biogeochemical properties (e.g., Fe enriched vs. depleted conditions, dominance of diatoms vs. other phytoplankton,…) was investigated. This was implemented in the framework of an exhaustive characterization of the Si-biogeochemical cycle using different parameters: PDMPO labelling, 32Si and 30Si spiked incubations, and, taxonomy. We have developed a new method for the determination of the production and dissolution rates from the 30Si isotopic dilution technique. We now measure the changes of the 30Si-abundances in particulate and liquid phases by High Resolution Sector Field Inductively Coupled Plasma Mass Spectrometer (HR-SF-ICP-MS). This method, which is faster, more sensitive and more precise than the traditional ones using an Isotope Ratio Mass Spectrometer (IRMS) or Thermal Ionization Mass Spectrometer (TIMS), will significantly aid in expanding the biogenic silica production-dissolution dataset in the ocean. The results obtained on Si budget indicate that the Si-regeneration (dissolution) dominates over Si-uptake (production) in the PFZ (1.9 ± 1.5), in contrast to SAZ where production is much larger than dissolution rate (0.08 ± 0.12). The efficiency of the Si-regeneration in late summer seems to be highly variable with significant variations at the same station on short timescale (days). These results will be compared with the other ones obtained from the unique toolbox implemented during SAZ-SENSE to study the Si cycle. They will be discussed to better assess the role of SAZ and PFZ in the global marine Si cycle.

Effects of sea-ice and biogeochemical processes and storms on under-ice water fCO2 during the winter-spring transition in the high Arctic Ocean: Implications for sea-air CO2 fluxes

NASA Astrophysics Data System (ADS)

Fransson, Agneta; Chierici, Melissa; Skjelvan, Ingunn; Olsen, Are; Assmy, Philipp; Peterson, Algot K.; Spreen, Gunnar; Ward, Brian

2017-07-01

We performed measurements of carbon dioxide fugacity (fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N-ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard, and the Yermak Plateau. This unique winter-to-spring data set includes the first winter-time under-ice water fCO2 observations in this region. The observed under-ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea-air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m-2 d-1, depending strongly on the open-water fractions (OW) and storm events. The maximum sea-air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under-ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea-air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m-2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea-air CO2 fluxes 16%, and temperature and salinity insignificant.

Ocean acidification accelerates dissolution of experimental coral reef communities

NASA Astrophysics Data System (ADS)

Comeau, S.; Carpenter, R. C.; Lantz, C. A.; Edmunds, P. J.

2015-01-01

Ocean acidification (OA) poses a severe threat to tropical coral reefs, yet much of what is know about these effects comes from individual corals and algae incubated in isolation under high pCO2. Studies of similar effects on coral reef communities are scarce. To investigate the response of coral reef communities to OA, we used large outdoor flumes in which communities composed of calcified algae, corals, and sediment were combined to match the percentage cover of benthic communities in the shallow back reef of Moorea, French Polynesia. Reef communities in the flumes were exposed to ambient (~ 400 μatm) and high pCO2 (~ 1300 μatm) for 8 weeks, and calcification rates measured for the constructed communities including the sediments. Community calcification was reduced by 59% under high pCO2, with sediment dissolution explaining ~ 50% of this decrease; net calcification of corals and calcified algae remained positive but was reduced by 29% under elevated pCO2. These results show that, despite the capacity of coral reef calcifiers to maintain positive net accretion of calcium carbonate under OA conditions, reef communities might transition to net dissolution as pCO2 increases, particularly at night, due to enhanced sediment dissolution.

Ocean acidification accelerates dissolution of experimental coral reef communities

NASA Astrophysics Data System (ADS)

Comeau, S.; Carpenter, R. C.; Lantz, C. A.; Edmunds, P. J.

2014-08-01

Ocean acidification (OA) poses a severe threat to tropical coral reefs, yet much of what is know about these effects comes from individual corals and algae incubated in isolation under high pCO2. Studies of similar effects on coral reef communities are scarce. To investigate the response of coral reef communities to OA, we used large outdoor flumes in which communities composed of calcified algae, corals, and sediment were combined to match the percentage cover of benthic communities in the shallow back reef of Moorea, French Polynesia. Reef communities in the flumes were exposed to ambient (~400 μatm) and high pCO2 (~1300 μatm) for 8 weeks, and calcification rates measured for the constructed communities including the sediments. Community calcification was depressed 59% under high pCO2, with sediment dissolution explaining ~50% of this decrease; net calcification of corals and calcified algae remained positive, but was reduced 29% under elevated pCO2. These results show that despite the capacity of coral reef calcifiers to maintain positive net accretion of calcium carbonate under OA conditions, reef communities might switch to net dissolution as pCO2 increases, particularly at night, due to enhanced sediment dissolution.

The impact of changing surface ocean conditions on the dissolution of aerosol iron

NASA Astrophysics Data System (ADS)

Fishwick, Matthew P.; Sedwick, Peter N.; Lohan, Maeve C.; Worsfold, Paul J.; Buck, Kristen N.; Church, Thomas M.; Ussher, Simon J.

2014-11-01

The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 µm) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 µm). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans.

PubMed

Stockdale, Anthony; Krom, Michael D; Mortimer, Robert J G; Benning, Liane G; Carslaw, Kenneth S; Herbert, Ross J; Shi, Zongbo; Myriokefalitakis, Stelios; Kanakidou, Maria; Nenes, Athanasios

2016-12-20

Acidification of airborne dust particles can dramatically increase the amount of bioavailable phosphorus (P) deposited on the surface ocean. Experiments were conducted to simulate atmospheric processes and determine the dissolution behavior of P compounds in dust and dust precursor soils. Acid dissolution occurs rapidly (seconds to minutes) and is controlled by the amount of H + ions present. For H + < 10 -4 mol/g of dust, 1-10% of the total P is dissolved, largely as a result of dissolution of surface-bound forms. At H + > 10 -4 mol/g of dust, the amount of P (and calcium) released has a direct proportionality to the amount of H + consumed until all inorganic P minerals are exhausted and the final pH remains acidic. Once dissolved, P will stay in solution due to slow precipitation kinetics. Dissolution of apatite-P (Ap-P), the major mineral phase in dust (79-96%), occurs whether calcium carbonate (calcite) is present or not, although the increase in dissolved P is greater if calcite is absent or if the particles are externally mixed. The system was modeled adequately as a simple mixture of Ap-P and calcite. P dissolves readily by acid processes in the atmosphere in contrast to iron, which dissolves more slowly and is subject to reprecipitation at cloud water pH. We show that acidification can increase bioavailable P deposition over large areas of the globe, and may explain much of the previously observed patterns of variability in leachable P in oceanic areas where primary productivity is limited by this nutrient (e.g., Mediterranean).

Psychedelics, Personality and Political Perspectives.

PubMed

Nour, Matthew M; Evans, Lisa; Carhart-Harris, Robin L

2017-01-01

The psychedelic experience (including psychedelic-induced ego dissolution) can effect lasting change in a person's attitudes and beliefs. Here, we aimed to investigate the association between naturalistic psychedelic use and personality, political perspectives, and nature relatedness using an anonymous internet survey. Participants (N = 893) provided information about their naturalistic psychedelic, cocaine, and alcohol use, and answered questions relating to personality traits of openness and conscientiousness (Ten-Item Personality Inventory), nature relatedness (Nature-Relatedness Scale), and political attitudes (one-item liberalism-conservatism measure and five-item libertarian-authoritarian measure). Participants also rated the degree of ego dissolution experienced during their "most intense" recalled psychedelic experience (Ego-Dissolution Inventory). Multivariate linear regression analysis indicated that lifetime psychedelic use (but not lifetime cocaine use or weekly alcohol consumption) positively predicted liberal political views, openness and nature relatedness, and negatively predicted authoritarian political views, after accounting for potential confounding variables. Ego dissolution experienced during a participant's "most intense" psychedelic experience positively predicted liberal political views, openness and nature relatedness, and negatively predicted authoritarian political views. Further work is needed to investigate the nature of the relationship between the peak psychedelic experience and openness to new experiences, egalitarian political views, and concern for the environment.

The Behavior and Dissolution of Gas Bubble Clouds in an Ocean Environment

DTIC Science & Technology

1992-05-08

William T. Shaffer, Class of 1992 U. S. Naval Academy Annapolis, Maryland Dr. Mare~ti Crza Naval Architechture , Ocean, & Marine Engineering Acccepted for... ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER U.S. Naval Academy, Annapolis, Md. U.S.N.A. - TSPR; 198 (1992) 9. SPONSORING

Limacina retroversa's response to combined effects of ocean acidification and sea water freshening

NASA Astrophysics Data System (ADS)

Manno, C.; Morata, N.; Primicerio, R.

2012-11-01

Anthropogenic carbon dioxide emissions induce ocean acidification, thereby reducing carbonate ion concentration, which may affect the ability of calcifying organisms to build shells. Pteropods, the main planktonic producers of aragonite in the worlds' oceans, may be particularly vulnerable to changes in sea water chemistry. The negative effects are expected to be most severe at high-latitudes, where natural carbonate ion concentrations are low. In this study we investigated the combined effects of ocean acidification and freshening on Limacina retroversa, the dominant pteropod in sub polar areas. Living L. retroversa, collected in Northern Norwegian Sea, were exposed to four different pH values ranging from the pre-industrial level to the forecasted end of century ocean acidification scenario. Since over the past half-century the Norwegian Sea has experienced a progressive freshening with time, each pH level was combined with a salinity gradient in two factorial, randomized experiments investigating shell degradation, swimming behavior and survival. In addition, to investigate shell degradation without any physiologic influence, one perturbation experiments using only shells of dead pteropods was performed. Lower pH reduced shell mass whereas shell dissolution increased with pCO2. Interestingly, shells of dead organisms had a higher degree of dissolution than shells of living individuals. Mortality of Limacina retroversa was strongly affected only when both pH and salinity reduced simultaneously. The combined effects of lower salinity and lower pH also affected negatively the ability of pteropods to swim upwards. Results suggest that the energy cost of maintaining ion balance and avoiding sinking (in low salinity scenario) combined with the extra energy cost necessary to counteract shell dissolution (in high pCO2 scenario), exceed the available energy budget of this organism causing the pteropods to change swimming behavior and begin to collapse. Since L. retroversa play an important role in the transport of carbonates to the deep oceans these findings have significant implications for the mechanisms influencing the inorganic carbon cycle in the sub-polar area.

Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem

PubMed Central

Bednaršek, N.; Feely, R. A.; Reum, J. C. P.; Peterson, B.; Menkel, J.; Alin, S. R.; Hales, B.

2014-01-01

Few studies to date have demonstrated widespread biological impacts of ocean acidification (OA) under conditions currently found in the natural environment. From a combined survey of physical and chemical water properties and biological sampling along the Washington–Oregon–California coast in August 2011, we show that large portions of the shelf waters are corrosive to pteropods in the natural environment. We show a strong positive correlation between the proportion of pteropod individuals with severe shell dissolution damage and the percentage of undersaturated water in the top 100 m with respect to aragonite. We found 53% of onshore individuals and 24% of offshore individuals on average to have severe dissolution damage. Relative to pre-industrial CO2 concentrations, the extent of undersaturated waters in the top 100 m of the water column has increased over sixfold along the California Current Ecosystem (CCE). We estimate that the incidence of severe pteropod shell dissolution owing to anthropogenic OA has doubled in near shore habitats since pre-industrial conditions across this region and is on track to triple by 2050. These results demonstrate that habitat suitability for pteropods in the coastal CCE is declining. The observed impacts represent a baseline for future observations towards understanding broader scale OA effects. PMID:24789895

Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem.

PubMed

Bednaršek, N; Feely, R A; Reum, J C P; Peterson, B; Menkel, J; Alin, S R; Hales, B

2014-06-22

Few studies to date have demonstrated widespread biological impacts of ocean acidification (OA) under conditions currently found in the natural environment. From a combined survey of physical and chemical water properties and biological sampling along the Washington-Oregon-California coast in August 2011, we show that large portions of the shelf waters are corrosive to pteropods in the natural environment. We show a strong positive correlation between the proportion of pteropod individuals with severe shell dissolution damage and the percentage of undersaturated water in the top 100 m with respect to aragonite. We found 53% of onshore individuals and 24% of offshore individuals on average to have severe dissolution damage. Relative to pre-industrial CO2 concentrations, the extent of undersaturated waters in the top 100 m of the water column has increased over sixfold along the California Current Ecosystem (CCE). We estimate that the incidence of severe pteropod shell dissolution owing to anthropogenic OA has doubled in near shore habitats since pre-industrial conditions across this region and is on track to triple by 2050. These results demonstrate that habitat suitability for pteropods in the coastal CCE is declining. The observed impacts represent a baseline for future observations towards understanding broader scale OA effects.

Is the Core Top Really Modern? A Story of Chemical Erosion, Bioturbation, and Lateral Sediment Redistribution from the Eastern Equatorial Pacific

NASA Astrophysics Data System (ADS)

Mekik, F.

2016-12-01

Paleoceanographic work is based on calibrating paleo-environmental proxies using well-preserved core top sediments which represent the last one thousand years or less. However, core top sediments may be in places as old as 9000 years due to various sedimentary and diagenetic processes, such as chemical erosion, bioturbation and lateral sediment redistribution. We hypothesize that in regions with high surface ocean productivity, high organic carbon to calcite ratios reaching the seabed promote calcite dissolution in sediments, even in regions above the lysocline. This process may lead to chemical erosion of core tops which in turn may result in core top aging. The eastern equatorial Pacific (EEP), a popular site for calibration of paleoceanographic proxies, is such a place. Better understanding the relationship between core top age and dissolution will help correct biases inherent in proxy calibration because dissolution of foraminifers alters shell chemistry, and wholesale dissolution of sediments leads to core top aging and loss. We present both new and literature-based core top data of radiocarbon ages from the EEP. We created regional maps of both core top radiocarbon age and calcite preservation measured with the Globorotalia menardii Fragmentation Index (MFI; over 100 core tops). Our maps show a clear pattern of deep sea sedimentary calcite dissolution mimicking the pattern of surface ocean productivity observed from satellites and sediment traps in the EEP. Core top radiocarbon ages generally parallel the dissolution patterns observed in the region. Where this relationship does not hold true, bioturbation and/or lateral sediment redistribution may play a role. Down core radiocarbon and 230Th-normalized sediment accumulation rate data from several cores in the EEP support this hypothesis. Better understanding the role of diagenesis promotes the development of more reliable paleo-environmental proxies.

Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans

PubMed Central

Krom, Michael D.; Mortimer, Robert J. G.; Benning, Liane G.; Herbert, Ross J.; Shi, Zongbo; Kanakidou, Maria; Nenes, Athanasios

2016-01-01

Acidification of airborne dust particles can dramatically increase the amount of bioavailable phosphorus (P) deposited on the surface ocean. Experiments were conducted to simulate atmospheric processes and determine the dissolution behavior of P compounds in dust and dust precursor soils. Acid dissolution occurs rapidly (seconds to minutes) and is controlled by the amount of H+ ions present. For H+ < 10−4 mol/g of dust, 1–10% of the total P is dissolved, largely as a result of dissolution of surface-bound forms. At H+ > 10−4 mol/g of dust, the amount of P (and calcium) released has a direct proportionality to the amount of H+ consumed until all inorganic P minerals are exhausted and the final pH remains acidic. Once dissolved, P will stay in solution due to slow precipitation kinetics. Dissolution of apatite-P (Ap-P), the major mineral phase in dust (79–96%), occurs whether calcium carbonate (calcite) is present or not, although the increase in dissolved P is greater if calcite is absent or if the particles are externally mixed. The system was modeled adequately as a simple mixture of Ap-P and calcite. P dissolves readily by acid processes in the atmosphere in contrast to iron, which dissolves more slowly and is subject to reprecipitation at cloud water pH. We show that acidification can increase bioavailable P deposition over large areas of the globe, and may explain much of the previously observed patterns of variability in leachable P in oceanic areas where primary productivity is limited by this nutrient (e.g., Mediterranean). PMID:27930294

Impact of dissolution on the sedimentary record of the Paleocene-Eocene thermal maximum

NASA Astrophysics Data System (ADS)

Bralower, Timothy J.; Kelly, D. Clay; Gibbs, Samantha; Farley, Kenneth; Eccles, Laurie; Lindemann, T. Logan; Smith, Gregory J.

2014-09-01

The input of massive amounts of carbon to the atmosphere and ocean at the Paleocene-Eocene Thermal Maximum (PETM; ˜55.53 Ma) resulted in pervasive carbonate dissolution at the seafloor. At many sites this dissolution also penetrated into the underlying sediment column. The magnitude of dissolution at and below the seafloor, a process known as chemical erosion, and its effect on the stratigraphy of the PETM, are notoriously difficult to constrain. Here, we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the PETM at three deep-sea sites characterized by a range of bottom water dissolution intensity. We show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution. We compare these data with dissolution and other proxy records, electron micrograph observations of samples and lithology. The complete data set indicates that the two sites with slower carbonate accumulation, and less active bioturbation, are characterized by significant chemical erosion. At the third site, higher carbonate accumulation rates, more active bioturbation, and possibly winnowing have limited the impacts of dissolution. However, grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records.

An Ecological Tipping Point Defined by Shallow Marine Foraminifera in the latest Paleocene

NASA Astrophysics Data System (ADS)

Robinson, M. M.; Spivey, W.

2016-12-01

The Paleocene-Eocene Thermal Maximum (PETM) is recognized in marine sediments by a carbonate dissolution zone, the extinction or turnover of benthic taxa, and a radiation of planktic excursion taxa, all accompanied by a rapid-onset, negative carbon isotope excursion (CIE). We present foraminiferal evidence from shallow marine sediments in southeastern Maryland, USA, where accumulation rates are high, for a minor ocean acidification event in the latest Paleocene that coincides with a relatively small (-2‰) CIE. This pre-onset excursion (POE) precedes the larger (-4‰) PETM CIE onset and dissolution event. During the POE, the benthic assemblage is reconfigured toward agglutinated species in order to adapt to increased acidity, and the planktic assemblage begins to speciate due to perturbed mixed layer conditions. The benthic assemblage returns to normal, without interruption, as the POE recovers, but planktic excursion taxa continue to appear in very low numbers. This is contrasted to the major ocean acidification event associated with the PETM CIE onset that results in a zone of complete dissolution followed by distinctive benthic and planktic foraminiferal assemblages. Our microfossil evidence documents a biotic response to bottom water and mixed layer perturbations that illustrates how coastal ecosystems react to both moderate and severe ocean acidification events, bracketing the ecological tipping point of shallow marine ecosystems. The POE, roughly half the magnitude of the CIE onset, provides insight into the nature of the initial effects of climate perturbation as well as an example of one that is fully recoverable. It is here that research aimed to better understand the long-term effects and reversibility of modern deteriorating oceanic conditions should focus. This study provides an initial metric by which to measure modern ecosystem disturbances and will help to define the tipping point for the shallow marine environment.

Corrosion of Cu-xZn alloys in slightly alkaline chloride solutions studied by stripping voltammetry and microanalysis.

PubMed

Milosev, I; Minović, A

2001-01-01

The mechanism of corrosion of Cu-xZn alloys (x = 10-40 wt %) in slightly alkaline chloride solutions was investigated by analysing solid reaction products by energy dispersive X-ray analysis (EDS) and dissolved reaction products by differential anodic pulse stripping (DAPS) voltammetry. The corrosion process was studied under open circuit and under potentiostatic conditions at selected potentials. Pure metals were studied comparatively so that an interacting effect of particular metal components in the alloy could be determined. All four Cu-xZn alloys show an improved behaviour compared to pure metals. Under open-circuit condition both components dissolve simultaneously in the solution. With increasing immersion time the preferential, dissolution of zinc in the solution becomes pronounced. It is the highest for Cu-10Zn and the lowest for Cu-30Zn alloy. Under potentiostatic control the dissolution mechanism depends on the electrode potential and changes from exclusive dissolution of zinc to simultaneous dissolution of both components with preferential dissolution of zinc. The latter decreases, as the electrode potential becomes more positive.

Testing the Deglacial Global Ocean Alkalization Hypothesis Using Foraminifer-based Mg/Ca, Shell Weight, and MFI

NASA Astrophysics Data System (ADS)

Ward, B. M.; Mekik, F.; Pourmand, A.

2015-12-01

In light of evidence for extensive modern ocean acidification, it has become imperative to better understand the global carbon cycle by reconstructing past ocean acidification/alkalization events. Our goal is to test the deglacial global alkalization hypothesis using a multi-proxy approach by reconstructing the pH, temperature, and [CO32-] of thermocline waters and the dissolution in deep sea sediments over the last 25,000 years in core ME-27 from the eastern equatorial Pacific. Our specific research questions are: Is there unequivocal evidence for a deglacial ocean alkalization event? If yes, what was the magnitude of the alkalization event? If no, how can we explain why evidence of this event is missing from our core? We inferred temperature from Mg/Ca, and habitat water [CO32-] from sized-normalized shell weight in Neogloboquadrina dutertrei. Dissolution in sediments was estimated using the Globorotalia menardii Fragmentation Index (MFI). We see no clear indication of a deglacial ocean alkalization event with our proxies. Neither our shell weight, nor MFI data show a more alkaline deglacial ocean compared to the Last Glacial Maximum and the modern Interglacial. Instead, we observe a steady decrease in thermocline [CO32-], and increase in deep sea calcite preservation since the LGM. Our results may indicate that the global alkalization event was obscured in ME-27 due to higher organic carbon fluxes during the deglacial, and/or due to yet undetermined effects of temperature on the foraminifer shell weight proxy.

Experimental determination of methane dissolution from simulated subsurface oil leakages

NASA Astrophysics Data System (ADS)

Sauthoff, W.; Peltzer, E. T.; Walz, P. M.; Brewer, P. G.

2013-12-01

Subsurface oil leakages and increased offshore drilling efforts have raised concern over the fate of hydrocarbon mixtures of oil and gas in ocean environments. Recent wellhead and pipeline failures in the Gulf of Mexico are extreme examples of this problem. Understanding the mechanism and rate of vertical transport of hydrocarbon chemical species is necessary to predict the environmental impact of subsurface leakages. In a series of controlled experiments, we carried out a deep-sea field experiment in Monterey Canyon to investigate the behavior of a gas-saturated liquid hydrocarbon mass rising from the seafloor. Aboard the R/V Rachel Carson, we used the ROV Ventana to transport a laboratory prepared volume of decane (C10H22) saturated with methane gas (CH4) to mimic a subsurface seafloor discharge. We released the oil and gas mixture into a vertically oriented open bottom glass tube followed by methane loss rate measurements both at discrete depths, and during rapid, continuous vehicle ascent from 800 to 100 m water depth to monitor changes in dissolution and bubble nucleation. Using laser Raman techniques and HD video we quantified the chemical state of the hydrocarbon fluid, including rate of methane gas dissolution. The primary methane Raman peak was readily observable within the decane C-H stretching complex. Variation in the amount of gas dissolved in the oil greatly influences oil plume density and in turn oil plume vertical rise rate. Our results show that the rise rate of the hydrocarbon mass significantly exceeds the rate at which the excess methane was lost by dissolution. This result implies that vertical transport of methane in the saturated hydrocarbon liquid phase can greatly exceed a gas bubble plume ascending the water column from a seafloor source. These results and observations may be applicable to improved understanding of the composition, distribution, and environmental fate of leaked hydrocarbon mixtures and inform remediation efforts.

Global Biogeochemical Cycle of Si: Its Coupling to the Perturbed C-N-P cycles in Industrial Time

NASA Astrophysics Data System (ADS)

Lerman, A.; Li, D. D.; MacKenzie, F. T.

2010-12-01

The importance of silicon (Si) in global biogeochemical cycles is demonstrated by its abundance in the land and aquatic biomass, where Si/C is 0.02 in land plants and 0.15 in marine organisms. Estimates show that Si-bioproduction accounts for ~1.5% of terrestrial primary production, and ~4.5% in the coastal ocean. Human land-use activities have substantially changed regional patterns of vegetation distribution, soil conditions, and nutrient fluxes via runoff to the coastal ocean. Anthropogenic chemical fertilization of the land has caused a significant increase in fluvial nitrogen (N) and phosphorus (P) transport, whereas land-use and vegetation mass changes have caused variations in the riverine Si input, all eventually affecting the cycling of nutrients in the marine environment. We developed a global biogeochemical model of the Si cycle as coupled to the global C-N-P cycle model, TOTEM II (Terrestrial-Ocean-aTmosphere-Ecosystem-Model). In the model analysis from year 1700, taken as the start of the Anthropocene, to 2050, the bioproduction of Si on land and in the ocean is coupled to the bioproduction of C, perturbed by the atmospheric CO2 rise, land-use changes, and chemical fertilization. Also, temperature rise affects the Si cycling on land through bioproduction rates, terrestrial organic matter remineralization, and weathering, thereby affecting its delivery to the coastal zone. The results show that biouptake and subsequent release of Si on land strongly affect the Si river flux to the coastal ocean. During the 350-year period, Si river discharge has increased by ~10% until ~1940, decreasing since then to below its 1700 value and continuing to drop, under the current IPCC IS92 projections of CO2, temperature and other forcings. From 1700 to ~1950, land-use changes, associated with slash and burn of large areas of high-productivity land, caused a decrease of global land vegetation. Dissolution of Si in soil humus and weathering of silicate minerals are the main dissolved Si sources for rivers and groundwater. The decrease in Si uptake by land biomass made more Si available for river discharge, causing an increase in the Si river input until an increase in the land primary production reversed the process. Around 1950, the use of fertilizer on land, especially N and P, increased, driving the growth of coastal marine primary producers, including such Si organisms as diatoms, silicoflagellates, and sponge spicules, and thus causing a decrease of dissolved Si in the surface ocean. The percent decrease of coastal dissolved Si due to increased primary production is greater than that of surface open ocean due to the shorter residence time of Si in coastal water (~2.7 years) compared to that of surface open ocean (~10 years. The combination of the relatively small size and location of the coastal ocean at the junction of the land, atmosphere, and open ocean make it important to changes in water chemistry, in situ biological production, and sedimentary storage. Its buffer effect and fast response to perturbations are also shown in the results of this coupling study of the C-N-P-Si cycles.

Shell Condition and Survival of Puget Sound Pteropods Are Impaired by Ocean Acidification Conditions

PubMed Central

Busch, D. Shallin; Maher, Michael; Thibodeau, Patricia; McElhany, Paul

2014-01-01

We tested whether the thecosome pteropod Limacina helicina from Puget Sound, an urbanized estuary in the northwest continental US, experiences shell dissolution and altered mortality rates when exposed to the high CO2, low aragonite saturation state (Ωa) conditions that occur in Puget Sound and the northeast Pacific Ocean. Five, week-long experiments were conducted in which we incubated pteropods collected from Puget Sound in four carbon chemistry conditions: current summer surface (∼460–500 µatm CO2, Ωa≈1.59), current deep water or surface conditions during upwelling (∼760 and ∼1600–1700 µatm CO2, Ωa≈1.17 and 0.56), and future deep water or surface conditions during upwelling (∼2800–3400 µatm CO2, Ωa≈0.28). We measured shell condition using a scoring regime of five shell characteristics that capture different aspects of shell dissolution. We characterized carbon chemistry conditions in statistical analyses with Ωa, and conducted analyses considering Ωa both as a continuous dataset and as discrete treatments. Shell dissolution increased linearly as aragonite saturation state decreased. Discrete treatment comparisons indicate that shell dissolution was greater in undersaturated treatments compared to oversaturated treatments. Survival increased linearly with aragonite saturation state, though discrete treatment comparisons indicated that survival was similar in all but the lowest saturation state treatment. These results indicate that, under starvation conditions, pteropod survival may not be greatly affected by current and expected near-future aragonite saturation state in the NE Pacific, but shell dissolution may. Given that subsurface waters in Puget Sound’s main basin are undersaturated with respect to aragonite in the winter and can be undersaturated in the summer, the condition and persistence of the species in this estuary warrants further study. PMID:25162395

Shell condition and survival of Puget Sound pteropods are impaired by ocean acidification conditions.

PubMed

Busch, D Shallin; Maher, Michael; Thibodeau, Patricia; McElhany, Paul

2014-01-01

We tested whether the thecosome pteropod Limacina helicina from Puget Sound, an urbanized estuary in the northwest continental US, experiences shell dissolution and altered mortality rates when exposed to the high CO2, low aragonite saturation state (Ωa) conditions that occur in Puget Sound and the northeast Pacific Ocean. Five, week-long experiments were conducted in which we incubated pteropods collected from Puget Sound in four carbon chemistry conditions: current summer surface (∼460-500 µatm CO2, Ωa≈1.59), current deep water or surface conditions during upwelling (∼760 and ∼1600-1700 µatm CO2, Ωa≈1.17 and 0.56), and future deep water or surface conditions during upwelling (∼2800-3400 µatm CO2, Ωa≈0.28). We measured shell condition using a scoring regime of five shell characteristics that capture different aspects of shell dissolution. We characterized carbon chemistry conditions in statistical analyses with Ωa, and conducted analyses considering Ωa both as a continuous dataset and as discrete treatments. Shell dissolution increased linearly as aragonite saturation state decreased. Discrete treatment comparisons indicate that shell dissolution was greater in undersaturated treatments compared to oversaturated treatments. Survival increased linearly with aragonite saturation state, though discrete treatment comparisons indicated that survival was similar in all but the lowest saturation state treatment. These results indicate that, under starvation conditions, pteropod survival may not be greatly affected by current and expected near-future aragonite saturation state in the NE Pacific, but shell dissolution may. Given that subsurface waters in Puget Sound's main basin are undersaturated with respect to aragonite in the winter and can be undersaturated in the summer, the condition and persistence of the species in this estuary warrants further study.

Coal fly ash as a source of iron in atmospheric dust.

PubMed

Chen, Haihan; Laskin, Alexander; Baltrusaitis, Jonas; Gorski, Christopher A; Scherer, Michelle M; Grassian, Vicki H

2012-02-21

Anthropogenic coal fly ash (FA) aerosol may represent a significant source of bioavailable iron in the open ocean. Few measurements have been made that compare the solubility of atmospheric iron from anthropogenic aerosols and other sources. We report here an investigation of iron dissolution for three FA samples in acidic aqueous solutions and compare the solubilities with that of Arizona test dust (AZTD), a reference material for mineral dust. The effects of pH, simulated cloud processing, and solar radiation on iron solubility have been explored. Similar to previously reported results on mineral dust, iron in aluminosilicate phases provides the predominant component of dissolved iron. Iron solubility of FA is substantially higher than of the crystalline minerals comprising AZTD. Simulated atmospheric processing elevates iron solubility due to significant changes in the morphology of aluminosilicate glass, a dominant material in FA particles. Iron is continuously released into the aqueous solution as FA particles break up into smaller fragments. These results suggest that the assessment of dissolved atmospheric iron deposition fluxes and their effect on the biogeochemistry at the ocean surface should be constrained by the source, environmental pH, iron speciation, and solar radiation.

Decalcification and survival of benthic foraminifera under the combined impacts of varying pH and salinity.

PubMed

Charrieau, Laurie M; Filipsson, Helena L; Nagai, Yukiko; Kawada, Sachiko; Ljung, Karl; Kritzberg, Emma; Toyofuku, Takashi

2018-07-01

Coastal areas display natural large environmental variability such as frequent changes in salinity, pH, and carbonate chemistry. Anthropogenic impacts - especially ocean acidification - increase this variability, which may affect the living conditions of coastal species, particularly, calcifiers. We performed culture experiments on living benthic foraminifera to study the combined effects of lowered pH and salinity on the calcification abilities and survival of the coastal, calcitic species Ammonia sp. and Elphidium crispum. We found that in open ocean conditions (salinity ∼35) and lower pH than usual values for these species, the specimens displayed resistance to shell (test) dissolution for a longer time than in brackish conditions (salinity ∼5 to 20). However, the response was species specific as Ammonia sp. specimens survived longer than E. crispum specimens when placed in the same conditions of salinity and pH. Living, decalcified juveniles of Ammonia sp. were observed and we show that desalination is one cause for the decalcification. Finally, we highlight the ability of foraminifera to survive under Ω calc  < 1, and that high salinity and [Ca 2+ ] as building blocks are crucial for the foraminiferal calcification process. Copyright © 2018 Elsevier Ltd. All rights reserved.

Organic-rich sediments in ventilated deep-sea environments: Relationship to climate, sea level, and trophic changes

NASA Astrophysics Data System (ADS)

Bertrand, P.; Pedersen, T. F.; Schneider, R.; Shimmield, G.; Lallier-Verges, E.; Disnar, J. R.; Massias, D.; Villanueva, J.; Tribovillard, N.; Huc, A. Y.; Giraud, X.; Pierre, C.; VéNec-Peyré, M.-T.

2003-02-01

Sediments on the Namibian Margin in the SE Atlantic between water depths of ˜1000 and ˜3600 m are highly enriched in hydrocarbon-prone organic matter. Such sedimentation has occurred for more than 2 million years and is geographically distributed over hundreds of kilometers along the margin, so that the sediments of this region contain a huge concentrated stock of organic carbon. It is shown here that most of the variability in organic content is due to relative dilution by buried carbonates. This reflects both export productivity and diagenetic dissolution, not differences in either water column or bottom water anoxia and related enhanced preservation of organic matter. These observations offer a new mechanism for the formation of potential source rocks in a well-ventilated open ocean, in this case the South Atlantic. The organic richness is discussed in terms of a suite of probable controls including local wind-driven productivity (upwelling), trophic conditions, transfer efficiency, diagenetic processes, and climate-related sea level and deep circulation. The probability of past occurrences of such organic-rich facies in equivalent oceanographic settings at the edge of large oceanic basins should be carefully considered in deep offshore exploration.

Quantifying the impact of riverine particulate dissolution in seawater on ocean chemistry

NASA Astrophysics Data System (ADS)

Jones, Morgan T.; Gislason, Sigurður R.; Burton, Kevin W.; Pearce, Christopher R.; Mavromatis, Vasileios; Pogge von Strandmann, Philip A. E.; Oelkers, Eric H.

2014-06-01

The quantification of the sources and sinks of elements to the oceans forms the basis of our understanding of global geochemical cycles and the chemical evolution of the Earth's surface. There is, however, a large imbalance in the current best estimates of the global fluxes to the oceans for many elements. In the case of strontium (Sr), balancing the input from rivers would require a much greater mantle-derived component than is possible from hydrothermal water flux estimates at mid-ocean ridges. Current estimates of riverine fluxes are based entirely on measurements of dissolved metal concentrations, and neglect the impact of riverine particulate dissolution in seawater. Here we present 87Sr/86Sr isotope data from an Icelandic estuary, which demonstrate rapid Sr release from the riverine particulates. We calculate that this Sr release is 1.1-7.5 times greater than the corresponding dissolved riverine flux. If such behaviour is typical of volcanic particulates worldwide, this release could account for 6-45% of the perceived marine Sr budget imbalance, with continued element release over longer timescales further reducing the deficit. Similar release from particulate material will greatly affect the marine budgets of many other elements, changing our understanding of coastal productivity, and anthropogenic effects such as soil erosion and the damming of rivers.

Dissolution of coccolithophorid calcite by microzooplankton and copepod grazing

NASA Astrophysics Data System (ADS)

Antia, A. N.; Suffrian, K.; Holste, L.; Müller, M. N.; Nejstgaard, J. C.; Simonelli, P.; Carotenuto, Y.; Putzeys, S.

2008-01-01

Independent of the ongoing acidification of surface seawater, the majority of the calcium carbonate produced in the pelagial is dissolved by natural processes above the lysocline. We investigate to what extent grazing and passage of coccolithophorids through the guts of copepods and the food vacuoles of microzooplankton contribute to calcite dissolution. In laboratory experiments where the coccolithophorid Emiliania huxleyi was fed to the rotifer Brachionus plicatilis, the heterotrophic flagellate Oxyrrhis marina and the copepod Acartia tonsa, calcite dissolution rates of 45-55%, 37-53% and 5-22% of ingested calcite were found. We ascribe higher loss rates in microzooplankton food vacuoles as compared to copepod guts to the strongly acidic digestion and the individual packaging of algal cells. In further experiments, specific rates of calcification and calcite dissolution were also measured in natural populations during the PeECE III mesocosm study under differing ambient pCO2 concentrations. Microzooplankton grazing accounted for between 27 and 70% of the dynamic calcite stock being lost per day, with no measurable effect of CO2 treatment. These measured calcite dissolution rates indicate that dissolution of calcite in the guts of microzooplankton and copepods can account for the calcite losses calculated for the global ocean using budget and model estimates.

Iron dissolution of dust source materials during simulated acidic processing: the effect of sulfuric, acetic, and oxalic acids.

PubMed

Chen, Haihan; Grassian, Vicki H

2013-09-17

Atmospheric organic acids potentially display different capacities in iron (Fe) mobilization from atmospheric dust compared with inorganic acids, but few measurements have been made on this comparison. We report here a laboratory investigation of Fe mobilization of coal fly ash, a representative Fe-containing anthropogenic aerosol, and Arizona test dust, a reference source material for mineral dust, in pH 2 sulfuric acid, acetic acid, and oxalic acid, respectively. The effects of pH and solar radiation on Fe dissolution have also been explored. The relative capacities of these three acids in Fe dissolution are in the order of oxalic acid > sulfuric acid > acetic acid. Oxalate forms mononuclear bidentate ligand with surface Fe and promotes Fe dissolution to the greatest extent. Photolysis of Fe-oxalate complexes further enhances Fe dissolution with the concomitant degradation of oxalate. These results suggest that ligand-promoted dissolution of Fe may play a more significant role in mobilizing Fe from atmospheric dust compared with proton-assisted processing. The role of atmospheric organic acids should be taken into account in global-biogeochemical modeling to better access dissolved atmospheric Fe deposition flux at the ocean surface.

Elevated CO2 affects shell dissolution rate but not calcification rate in a marine snail.

PubMed

Nienhuis, Sarah; Palmer, A Richard; Harley, Christopher D G

2010-08-22

As CO(2) levels increase in the atmosphere, so too do they in the sea. Although direct effects of moderately elevated CO(2) in sea water may be of little consequence, indirect effects may be profound. For example, lowered pH and calcium carbonate saturation states may influence both deposition and dissolution rates of mineralized skeletons in many marine organisms. The relative impact of elevated CO(2) on deposition and dissolution rates are not known for many large-bodied organisms. We therefore tested the effects of increased CO(2) levels--those forecast to occur in roughly 100 and 200 years--on both shell deposition rate and shell dissolution rate in a rocky intertidal snail, Nucella lamellosa. Shell weight gain per day in live snails decreased linearly with increasing CO(2) levels. However, this trend was paralleled by shell weight loss per day in empty shells, suggesting that these declines in shell weight gain observed in live snails were due to increased dissolution of existing shell material, rather than reduced production of new shell material. Ocean acidification may therefore have a greater effect on shell dissolution than on shell deposition, at least in temperate marine molluscs.

Shell preservation of Limacina inflata (Pteropoda) in surface sediments from the Central and South Atlantic Ocean: a new proxy to determine the aragonite saturation state of water masses

NASA Astrophysics Data System (ADS)

Gerhardt, Sabine; Henrich, Rüdiger

2001-08-01

Over 300 surface sediment samples from the Central and South Atlantic Ocean and the Caribbean Sea were investigated for the preservation state of the aragonitic test of Limacina inflata. Results are displayed in spatial distribution maps and are plotted against cross-sections of vertical water mass configurations, illustrating the relationship between preservation state, saturation state of the overlying waters, and overall water mass distribution. The microscopic investigation of L. inflata (adults) yielded the Limacina dissolution index (LDX), and revealed three regional dissolution patterns. In the western Atlantic Ocean, sedimentary preservation states correspond to saturation states in the overlying waters. Poor preservation is found within intermediate water masses of southern origin (i.e. Antarctic intermediate water (AAIW), upper circumpolar water (UCDW)), which are distinctly aragonite-corrosive, whereas good preservation is observed within the surface waters above and within the upper North Atlantic deep water (UNADW) beneath the AAIW. In the eastern Atlantic Ocean, in particular along the African continental margin, the LDX fails in most cases (i.e. less than 10 tests of L. inflata per sample were found). This is most probably due to extensive "metabolic" aragonite dissolution at the sediment-water interface combined with a reduced abundance of L. inflata in the surface waters. In the Caribbean Sea, a more complex preservation pattern is observed because of the interaction between different water masses, which invade the Caribbean basins through several channels, and varying input of bank-derived fine aragonite and magnesian calcite material. The solubility of aragonite increases with increasing pressure, but aragonite dissolution in the sediments does not simply increase with water depth. Worse preservation is found in intermediate water depths following an S-shaped curve. As a result, two aragonite lysoclines are observed, one above the other. In four depth transects, we show that the western Atlantic and Caribbean LDX records resemble surficial calcium carbonate data and δ13C and carbonate ion concentration profiles in the water column. Moreover, preservation of L. inflata within AAIW and UCDW improves significantly to the north, whereas carbonate corrosiveness diminishes due to increased mixing of AAIW and UNADW. The close relationship between LDX values and aragonite contents in the sediments shows much promise for the quantification of the aragonite loss under the influence of different water masses. LDX failure and uncertainties may be attributed to (1) aragonite dissolution due to bottom water corrosiveness, (2) aragonite dissolution due to additional CO 2 release into the bottom water by the degradation of organic matter based on an enhanced supply of organic matter into the sediment, (3) variations in the distribution of L. inflata and hence a lack of supply into the sediment, (4) dilution of the sediments and hence a lack of tests of L. inflata, or (5) redeposition of sediment particles.

Imminent onset and abrupt increase in duration of low aragonite and calcite saturation state events in the Southern Ocean

NASA Astrophysics Data System (ADS)

Friedrich, T.; Hauri, C.; Timmermann, A.

2015-12-01

Rapid progression of ocean acidification is a threat to key organisms of the Southern Ocean ecosystem. While the severity of ocean acidification impacts is mainly determined by the duration, intensity, and spatial extent of low aragonite or calcite saturation state events, little is known about the nature of these events, their evolving attributes, and the timing of their onset. Using output of historical and RCP 8.5 simulations from ten Earth System Models from CMIP5, we found that aragonite undersaturation, which decreases the calcification rate of pteropods and causes dissolution of their aragonitic shell, will spread rapidly after 2035, covering 70 % of the Southern Ocean surface waters by 2095. Surface aragonite undersaturation events will last for about 5 months in areas south of 60°S by 2055, and for more than 8 months by the end of the century. Overall, the duration of these events increases from 1 month to more than 6 months within fewer than 20 years in >75 % of the affected area. This abrupt change in exposure duration to unfavorable conditions may be too fast for pteropods to adapt, as these chemical changes will occur within just a few generations. As a result of two month-long calcite undersaturation events projected for the end of this century, even organisms built of the more stable calcium carbonate mineral calcite will face prolonged chemical dissolution. The threat of ocean acidification to the Southern Ocean ecosystem may be more imminent than previously thought, and may spread quickly to the southern tips of New Zealand, South America, and South Africa, with potentially far-reaching consequences to fisheries, local economies, and livelihoods.

Ocean Acidification Causes Increased Calcium Carbonate Turnover during Larval Shell Formation

NASA Astrophysics Data System (ADS)

Frieder, C.; Pan, F.; Applebaum, S.; Manahan, D. T.

2016-02-01

Mollusca is a major taxon for studies of the evolution and mechanisms of calcification. Under current and future ocean change scenarios, decreases in shell size have been observed in many molluscan species during early development. The mechanistic basis for these decreases are of significant interest. In this study, Pacific oyster larvae (Crassostrea gigas) reared at aragonite undersaturation (Ω < 1) accreted just a third of shell mass relative to control (Ω >> 1). Coupling radioisotope tracer assays with mineral mass measurements allowed calculation of calcification budgets for first shell formation in veliger stage larvae. Three primary mechanisms (in order of increasing effect) contributed to the change in shell mass at undersaturation: delayed onset of calcification, increased dissolution rates, and decreased net calcification rates. The observation of dissolution indicates turnover of the newly formed shell, and physicochemical constraints of undersaturation provide a mechanistic basis for decreased calcification.

Dissolution of Calcite in the Twilight Zone: Bacterial Control of Dissolution of Sinking Planktonic Carbonates Is Unlikely

PubMed Central

Bissett, Andrew; Neu, Thomas R.; de Beer, Dirk

2011-01-01

We investigated the ability of bacterial communities to colonize and dissolve two biogenic carbonates (Foraminifera and oyster shells). Bacterial carbonate dissolution in the upper water column is postulated to be driven by metabolic activity of bacteria directly colonising carbonate surfaces and the subsequent development of acidic microenvironments. We employed a combination of microsensor measurements, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and image analysis and molecular documentation of colonising bacteria to monitor microbial processes and document changes in shell surface topography. Bacterial communities rapidly colonised shell surfaces, forming dense biofilms with extracellular polymeric substance (EPS) deposits. Despite this, we found no evidence of bacterially mediated carbonate dissolution. Dissolution was not indicated by Ca2+ microprofiles, nor was changes in shell surface structure related to the presence of colonizing bacteria. Given the short time (days) settling carbonate material is actually in the twilight zone (500–1000 m), it is highly unlikely that microbial metabolic activity on directly colonised shells plays a significant role in dissolving settling carbonates in the shallow ocean. PMID:22102861

Dissolution of calcite in the twilight zone: bacterial control of dissolution of sinking planktonic carbonates is unlikely.

PubMed

Bissett, Andrew; Neu, Thomas R; Beer, Dirk de

2011-01-01

We investigated the ability of bacterial communities to colonize and dissolve two biogenic carbonates (Foraminifera and oyster shells). Bacterial carbonate dissolution in the upper water column is postulated to be driven by metabolic activity of bacteria directly colonising carbonate surfaces and the subsequent development of acidic microenvironments. We employed a combination of microsensor measurements, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and image analysis and molecular documentation of colonising bacteria to monitor microbial processes and document changes in shell surface topography. Bacterial communities rapidly colonised shell surfaces, forming dense biofilms with extracellular polymeric substance (EPS) deposits. Despite this, we found no evidence of bacterially mediated carbonate dissolution. Dissolution was not indicated by Ca²⁺ microprofiles, nor was changes in shell surface structure related to the presence of colonizing bacteria. Given the short time (days) settling carbonate material is actually in the twilight zone (500-1000 m), it is highly unlikely that microbial metabolic activity on directly colonised shells plays a significant role in dissolving settling carbonates in the shallow ocean.

On Subsurface Fracture Opening and Closure

NASA Astrophysics Data System (ADS)

Wang, Y.

2016-12-01

Mechanistic understanding of fracture opening and closure in geologic media is of significant importance to nature resource extraction and waste management, such as geothermal energy extraction, oil/gas production, radioactive waste disposal, and carbon sequestration and storage). A dynamic model for subsurface fracture opening and closure has been formulated. The model explicitly accounts for the stress concentration around individual aperture channels and the stress-activated mineral dissolution and precipitation. A preliminary model analysis has demonstrated the importance of the stress-activated dissolution mechanism in the evolution of fracture aperture in a stressed geologic medium. The model provides a reasonable explanation for some key features of fracture opening and closure observed in laboratory experiments, including a spontaneous switch from a net permeability reduction to a net permeability increase with no changes in a limestone fracture experiment.

Groundwater circulation and geochemistry of a karstified bank marginal fracture system, South Andros Island, Bahamas

NASA Astrophysics Data System (ADS)

Whitaker, Fiona F.; Smart, Peter L.

1997-10-01

On the east coast of South Andros Island, Bahamas, a major bank-marginal fracture system characterised by vertically extensive cavern systems (blue holes) is developed sub-parallel to the steep-sided deep-water re-entrant of the Tongue of the Ocean. In addition to providing a discharge route for meteoric, mixed and geochemically evolved saline groundwaters, a strong local circulation occurs along the fracture system. This generates enhanced vertical mixing within voids of the fracture system, evidenced by the increasing mixing zone thickness, and the thinning and increasing salinity of brackish lens waters from north to south along the fracture system. Furthermore, tidally driven pumping of groundwaters occurs between the fracture and adjacent carbonate aquifer affecting a zone up to 200 m either side of the fracture. The resultant mixing of groundwaters of contrasting salinity and PCO 2 within and along the fracture system and with the surrounding aquifer waters, together with bacterial oxidation of organic matter, generates significant potential for locally enhanced diagenesis. Undersaturation with respect to calcite within the fresh (or brackish)-salt water mixing zone is observed in the fracture system and predicted in the adjacent aquifer, while mixing between the brackish fracture lens and surrounding high PCO 2 fresh waters causes dissolution of aragonite but not calcite. The latter gives rise to considerable secondary porosity development, because active tidal pumping ensures continued renewal of dissolutional potential. This is evidenced by calcium and strontium enrichment in the brackish lens which indicates porosity generation by aragonite dissolution at a maximum rate of 0.35% ka -1, up to twice the average estimated for the fresh water lens. In contrast saline groundwaters are depleted in calcium relative to open ocean waters suggesting the formation of calcite cements. The development of a major laterally continuous cavernous fracture zone along the margin of the carbonate platform permits enhanced groundwater flow and mixing which may result in generation of a diagenetic `halo' at a scale larger than that generally recognised around syn-sedimentary fractures in fossil carbonates. This may be characterised by increased secondary porosity where a relative fall in sea-level results in exposure and formation of a meteoric groundwater system, or cementation by `marine' calcite both below this meteoric system, and where the bank surface is flooded by seawater.

Clinopyroxene dissolution in basaltic melt

NASA Astrophysics Data System (ADS)

Chen, Yang; Zhang, Youxue

2009-10-01

The history of magmatic systems may be inferred from reactions between mantle xenoliths and host basalt if the thermodynamics and kinetics of the reactions are quantified. To study diffusive and convective clinopyroxene dissolution in silicate melts, diffusive clinopyroxene dissolution experiments were conducted at 0.47-1.90 GPa and 1509-1790 K in a piston-cylinder apparatus. Clinopyroxene saturation is found to be roughly determined by MgO and CaO content. The effective binary diffusivities, DMgO and DCaO, and the interface melt saturation condition, C0MgO×C0CaO, are extracted from the experiments. DMgO and DCaO show Arrhenian dependence on temperature. The pressure dependence is small and not resolved within 0.47-1.90 GPa. C0MgO×C0CaO in the interface melt increases with increasing temperature, but decreases with increasing pressure. Convective clinopyroxene dissolution, where the convection is driven by the density difference between the crystal and melt, is modeled using the diffusivities and interface melt saturation condition. Previous studies showed that the convective dissolution rate depends on the thermodynamics, kinetics and fluid dynamics of the system. Comparing our results for clinopyroxene dissolution to results from a previous study on convective olivine dissolution shows that the kinetic and fluid dynamic aspects of the two minerals are quite similar. However, the thermodynamics of clinopyroxene dissolution depends more strongly on the degree of superheating and composition of the host melt than that of olivine dissolution. The models for clinopyroxene and olivine dissolution are tested against literature experiments on mineral-melt interaction. They are then applied to previously proposed reactions between Hawaii basalts and mantle minerals, mid-ocean ridge basalts and mantle minerals, and xenoliths digestion in a basalt at Kuandian, Northeast China.

Linking Crystal Populations to Dynamic States: Crystal Dissolution and Growth During an Open-System Event

NASA Astrophysics Data System (ADS)

Bergantz, G. W.; Schleicher, J.; Burgisser, A.

2016-12-01

The identification of shared characteristics in zoned crystals has motivated the definition of crystal populations. These populations reflect the simultaneous transport of crystals, heat and composition during open-system events. An obstacle to interpreting the emergence of a population is the absence of a way to correlate specific dynamic conditions with the characteristic attributes of a population. By combining a boundary-layer diffusion controlled model for crystal growth/dissolution with discrete-element magma dynamics simulations of crystal-bearing magmas, the creation of populations can be simulated. We have implemented a method that decomposes the chemical potential into the thermal and compositional contributions to crystal dissolution/growth. This allows for the explicit treatment of thermal inertia and thermal-compositional decoupling as fluid circulation stirs the system during an open-system event. We have identified three distinct dynamic states producing crystal populations. They are based on the volume fraction of crystals. In a mushy system, thermal and compositional states are tightly linked as the volume involved in the mixing is constrained by the so-called mixing bowl (Bergantz et al., 2015). The mixing bowl volume is a function of the visco-plastic response of the mush and the intrusion width, not by the progressive entrainment of the new intrusion as commonly assumed. Crystal dissolution is the dominate response to input of more primitive magma. At the other endmember, under very dilute conditions, thermal and compositional conditions can become decoupled, and the in-coming magma forms a double-diffusive low-Re jet. This can allow for both dissolution and growth as crystals circulate widely into an increasingly stratified system. A middle range of crystal concentration produces a very complex feedback, as sedimenting crystals form fingers and chains that interact with the incoming magma, break-up the entrainment with chaotic stirring and add a second length scale to the mixing. It simultaneously forms a small mixing bowl in the pile of crystals sedimenting at the base. This can produce very complex populations even in a simple open-system event. Bergantz et al., 2015, Open-system dynamics and mixing in magma mushes, Nature Geosci., DOI: 10.1038/NGEO2534

Net loss of CaCO3 from coral reef communities due to human induced seawater acidification

USGS Publications Warehouse

Andersson, A.J.; Kuffner, I.B.; MacKenzie, F.T.; Jokiel, P.L.; Rodgers, K.S.; Tan, A.

2009-01-01

Acidification of seawater owing to oceanic uptake of atmospheric CO2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns regarding its adverse effects on corals and calcifying communities. Here we demonstrate a net loss of calcium carbonate (CaCO3) material as a result of decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3) incubated in continuous-flow mesocosms subject to future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC=CaCO3 production – dissolution) was positive at 3.3 mmol CaCO3 m−2 h−1 under ambient seawater pCO2 conditions as opposed to negative at −0.04 mmol CaCO3 m−2h−1 under seawater conditions of double the ambient pCO2. These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. Nevertheless, individual corals remained healthy, actively calcified (albeit slower than at present rates), and deposited significant amounts of CaCO3 under the prevailing experimental seawater conditions of elevated pCO2.

Net Loss of CaCO3 from a subtropical calcifying community due to seawater acidification: Mesocosm-scale experimental evidence

USGS Publications Warehouse

Andersson, A.J.; Kuffner, I.B.; MacKenzie, F.T.; Jokiel, P.L.; Rodgers, K.S.; Tan, A.

2009-01-01

Acidification of seawater owing to oceanic uptake of atmospheric CO 2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns regarding its adverse effects on corals and calcifying communities. Here we demonstrate a net loss of calcium carbonate (CaCO3) material as a result of decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (N=3) incubated in continuous-flow mesocosms subject to future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NECC=CaCO3 production - dissolution) was positive at 3.3 mmol CaCO3 m-2 h-1 under ambient seawater pCO2 conditions as opposed to negative at -0.04 mmol CaCO3 m-2 h-1 under seawater conditions of double the ambient pCO2. These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. Nevertheless, individual corals remained healthy, actively calcified (albeit slower than at present rates), and deposited significant amounts of CaCO3 under the prevailing experimental seawater conditions of elevated pCO2.

Coral and mollusc resistance to ocean acidification adversely affected by warming

NASA Astrophysics Data System (ADS)

Rodolfo-Metalpa, R.; Houlbrèque, F.; Tambutté, É.; Boisson, F.; Baggini, C.; Patti, F. P.; Jeffree, R.; Fine, M.; Foggo, A.; Gattuso, J.-P.; Hall-Spencer, J. M.

2011-09-01

Increasing atmospheric carbon dioxide (CO2) concentrations are expectedto decrease surface ocean pH by 0.3-0.5 units by 2100 (refs , ), lowering the carbonate ion concentration of surfacewaters. This rapid acidification is predicted to dramatically decrease calcification in many marine organisms. Reduced skeletal growth under increased CO2 levels has already been shown for corals, molluscs and many other marine organisms. The impact of acidification on the ability of individual species to calcify has remained elusive, however, as measuring net calcification fails to disentangle the relative contributions of gross calcification and dissolution rates on growth. Here, we show that corals and molluscs transplanted along gradients of carbonate saturation state at Mediterranean CO2 vents are able to calcify and grow at even faster than normal rates when exposed to the high CO2 levels projected for the next 300 years. Calcifiers remain at risk, however, owing to the dissolution of exposed shells and skeletons that occurs as pH levels fall. Our results show that tissues and external organic layers play a major role in protecting shells and skeletons from corrosive sea water, limiting dissolution and allowing organisms to calcify. Our combined field and laboratory results demonstrate that the adverse effects of global warming are exacerbated when high temperatures coincide with acidification.

Dissolution of biogenic ooze over basement edifices in the equatorial Pacific with implications for hydrothermal ventilation of the oceanic crust

USGS Publications Warehouse

Bekins, B.A.; Spivack, A.J.; Davis, E.E.; Mayer, L.A.

2007-01-01

Recent observations indicate that curious closed depressions in carbonate sediments overlying basement edifices are widespread in the equatorial Pacific. A possible mechanism for their creation is dissolution by fluids exiting basement vents from off-axis hydrothermal flow. Quantitative analysis based on the retrograde solubility of calcium carbonate and cooling of basement fluids during ascent provides an estimate for the dissolution capacity of the venting fluids. Comparison of the dissolution capacity and fluid flux with typical equatorial Pacific carbonate mass accumulation rates shows that this mechanism is feasible. By maintaining sediment-free basement outcrops, the process may promote widespread circulation of relatively unaltered seawater in the basement in an area where average sediment thicknesses are 300-500 m. The enhanced ventilation can explain several previously puzzling observations in this region, including anomalously low heat flux, relatively unaltered seawater in the basement, and aerobic and nitrate-reducing microbial activity at the base of the sediments. ?? 2007 The Geological Society of America.

Effects of ocean acidification on the ballast of surface aggregates sinking through the twilight zone.

PubMed

de Jesus Mendes, Pedro A; Thomsen, Laurenz

2012-01-01

The dissolution of CaCO(3) is one of the ways ocean acidification can, potentially, greatly affect the ballast of aggregates. A diminution of the ballast could reduce the settling speed of aggregates, resulting in a change in the carbon flux to the deep sea. This would mean lower amounts of more refractory organic matter reaching the ocean floor. This work aimed to determine the effect of ocean acidification on the ballast of sinking surface aggregates. Our hypothesis was that the decrease of pH will increase the dissolution of particulate inorganic carbon ballasting the aggregates, consequently reducing their settling velocity and increasing their residence time in the upper twilight zone. Using a new methodology for simulation of aggregate settling, our results suggest that future pCO(2) conditions can significantly change the ballast composition of sinking aggregates. The change in aggregate composition had an effect on the size distribution of the aggregates, with a shift to smaller aggregates. A change also occurred in the settling velocity of the particles, which would lead to a higher residence time in the water column, where they could be continuously degraded. In the environment, such an effect would result in a reduction of the carbon flux to the deep-sea. This reduction would impact those benthic communities, which rely on the vertical flow of carbon as primary source of energy.

What controls silicon isotope fractionation during dissolution of diatom opal?

NASA Astrophysics Data System (ADS)

Wetzel, F.; de Souza, G. F.; Reynolds, B. C.

2014-04-01

The silicon isotope composition of opal frustules from photosynthesising diatoms is a promising tool for studying past changes in the marine silicon cycle, and indirectly that of carbon. Dissolution of this opal may be accompanied by silicon isotope fractionation that could disturb the pristine silicon isotope composition of diatom opal acquired in the surface ocean. It has previously been shown that dissolution of fresh and sediment trap diatom opal in seawater does fractionate silicon isotopes. However, as the mechanism of silicon isotope fractionation remained elusive, it is uncertain whether opal dissolution in general is associated with silicon isotope fractionation considering that opal chemistry and surface properties are spatially and temporally (i.e. opal of different age) diverse. In this study we dissolved sediment core diatom opal in 5 mM NaOH and found that this process is not associated with significant silicon isotope fractionation. Since no variability of the isotope effect was observed over a wide range of dissolution rates, we can rule out the suggestion that back-reactions had a significant influence on the net isotope effect. Similarly, we did not observe an impact of temperature, specific surface area, or degree of undersaturation on silicon isotope partitioning during dissolution, such that these can most likely also be ruled out as controlling factors. We discuss the potential impacts of the chemical composition of the dissolution medium and age of diatom opal on silicon isotope fractionation during dissolution. It appears most likely that the controlling mechanism of silicon isotope fractionation during dissolution is related to the reactivity, or potentially, aluminium content of the opal. Such a dependency would imply that silicon isotope fractionation during dissolution of diatom opal is spatially and temporally variable. However, since the isotope effects during dissolution are small, the silicon isotope composition of diatom opal appears to be robust against dissolution in the deep sea sedimentary environment.

The effect of a new formaldehyde-free binder on the dissolution rate of glass wool fibre in physiological saline solution.

PubMed

Potter, Russell M; Olang, Nassreen

2013-04-12

The in-vitro dissolution rate of fibres is a good predictor of the in-vivo behavior and potential health effects of inhaled fibres. This study examines the effect of a new formaldehyde-free carbohydrate-polycarboxylic acid binder on the in-vitro dissolution rate of biosoluble glass fibres. Dissolution rate measurements in pH 7.4 physiological saline solution show that the presence of the binder on wool insulation glass fibres has no effect on their dissolution. There is no measurable difference between the dissolution rates of continuous draw fibres before and after binder was applied by dipping. Nor is there a measurable difference between the dissolution rates of a production glass wool sample with binder and that same sample after removal of the binder by low-temperature ashing. Morphological examination shows that swelling of the binder in the solution is at least partially responsible for the development of open channels around the glass-binder interface early in the dissolution. These channels allow fluid to reach the entire glass surface under the binder coating. There is no evidence of any delay in the dissolution rate as a result of the binder coating.

The effect of a new formaldehyde-free binder on the dissolution rate of glass wool fibre in physiological saline solution

PubMed Central

2013-01-01

The in-vitro dissolution rate of fibres is a good predictor of the in-vivo behavior and potential health effects of inhaled fibres. This study examines the effect of a new formaldehyde-free carbohydrate-polycarboxylic acid binder on the in-vitro dissolution rate of biosoluble glass fibres. Dissolution rate measurements in pH 7.4 physiological saline solution show that the presence of the binder on wool insulation glass fibres has no effect on their dissolution. There is no measurable difference between the dissolution rates of continuous draw fibres before and after binder was applied by dipping. Nor is there a measurable difference between the dissolution rates of a production glass wool sample with binder and that same sample after removal of the binder by low-temperature ashing. Morphological examination shows that swelling of the binder in the solution is at least partially responsible for the development of open channels around the glass-binder interface early in the dissolution. These channels allow fluid to reach the entire glass surface under the binder coating. There is no evidence of any delay in the dissolution rate as a result of the binder coating. PMID:23587247

Open-Ocean and Coastal Properties of Recent Major Tsunamis

NASA Astrophysics Data System (ADS)

Rabinovich, A.; Thomson, R.; Zaytsev, O.

2017-12-01

The properties of six major tsunamis during the period 2009-2015 (2009 Samoa; 2010 Chile; 2011 Tohoku; 2012 Haida Gwaii; 2014 and 2015 Chile) were thoroughly examined using coastal data from British Columbia, the U.S. West Coast and Mexico, and offshore open-ocean DART and NEPTUNE stations. Based on joint spectral analyses of the tsunamis and background noise, we have developed a method to suppress the influence of local topography and to use coastal observations to determine the underlying spectra of tsunami waves in the deep ocean. The "reconstructed" open-ocean tsunami spectra were found to be in close agreement with the actual tsunami spectra evaluated from the analysis of directly measured open-ocean tsunami records. We have further used the spectral estimates to parameterize tsunamis based on their integral open-ocean spectral characteristics. Three key parameters are introduced to describe individual tsunami events: (1) Integral open-ocean energy; (2) Amplification factor (increase of the mean coastal tsunami variance relative to the open-ocean variance); and (3) Tsunami colour, the frequency composition of the open-ocean tsunami waves. In particular, we found that the strongest tsunamis, associated with large source areas (the 2010 Chile and 2011 Tohoku) are "reddish" (indicating the dominance of low-frequency motions), while small-source events (the 2009 Samoa and 2012 Haida Gwaii) are "bluish" (indicating strong prevalence of high-frequency motions).

50 CFR 648.15 - Facilitation of enforcement.

Code of Federal Regulations, 2011 CFR

2011-10-01

... surfclam and ocean quahog vessel owners and operators. (1) Surfclam and ocean quahog open access permitted vessels. Vessel owners or operators issued an open access surfclam or ocean quahog open access permit for.../or an Open Access Herring Permit that fished with midwater trawl gear pursuant to § 648.80(d). Such...

Impacts of ocean acidification on the carbonate system at the sediment-water interface: a case-study in the NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Rassmann, Jens; Lansard, Bruno; Gazeau, Frédéric; Grenz, Christian; Alliouane, Samir; Petit, Franck; Pozzato, Lara; Bombled, Bruno; Rabouille, Christophe

2016-04-01

According to common predictions, carbon dioxide (CO2) uptake from the atmosphere into the oceans will decrease the average pH of seawater by 0.06-0.32 pH units by 2100. Ocean acidification alters chemical equilibria in seawater and thus potentially impacts marine ecosystem structure and functioning. Shelf regions play a key role for an important fraction of marine life and represent an important part of the global carbon cycle. Due to shallow water depth, chemistry in the water column is strongly coupled with biogeochemistry in the sediments. The aim of the present work is to investigate the impact of ocean acidification on carbonate chemistry. It focuses especially on exchange fluxes of dissolved inorganic carbon (DIC), total alkalinity (TA) and calcium through the sediment-water interface, and its impact on calcium carbonate precipitation or dissolution. For this purpose, sediment cores were incubated ex situ with an open flow of CO2 enriched seawater for 22 days (pHT=7,4, pH reported on the total proton scale). In parallel, sediment cores were incubated as a control with untreated seawater. Incubations took place in a water bath in a dark room with controlled temperature (14°C). Oxygen and pH microprofiles were recorded in the top first mm of the sediment during the whole experiment every 3 days. On 7 occasions, cores were isolated and incubated for 12 hours to estimate fluxes of DIC, TA, oxygen and nutrients. Porewater profiles of DIC, TA, calcium and nutrients were analyzed before and after incubation. On the solid phase, the content of particulate organic carbon, the C:N ratio and its isotopic δ15N and δ13C signature have been determined. In addition, total carbon contents have been measured and X-Ray diffraction was used to look for phase shifts between calcite and aragonite. A net decrease of pH was observed in the upper sediment layers, as well as an increase of DIC and TA pore water concentrations. The acidified cores showed higher DIC and TA exchange fluxes during the incubations in isolation, whereas oxygen exchange fluxes were independent of pH. Significant changes in the solid phase of the sediments could not be identified and the calcium pore water concentrations seemed not to be affected by acidification of the overlying waters during the given time scale. These results are put in the framework of coastal ocean acidification and are used to understand how the acidification changes the carbonate chemistry in the pore waters and constrain dissolution/precipitation of calcium carbonate.

Intra-slab COH fluid fluxes evidenced by fluid-mediated decarbonation of lawsonite eclogite-facies altered oceanic metabasalts

NASA Astrophysics Data System (ADS)

Vitale Brovarone, Alberto; Chu, Xu; Martin, Laure; Ague, Jay J.; Monié, Patrick; Groppo, Chiara; Martinez, Isabelle; Chaduteau, Carine

2018-04-01

The interplay between the processes controlling the mobility of H2O and C-bearing species during subduction zone metamorphism exerts a critical control on plate tectonics and global volatile recycling. Here we present the first study on fresh, carbonate-bearing, lawsonite eclogite-facies metabasalts from Alpine Corsica, France, which reached the critical depths at which important devolatilization reactions occur in subducting slabs. The studied samples indicate that the evolution of oceanic crustal sequences subducted under present-day thermal regimes is dominated by localized fluid-rock interactions that are strongly controlled by the nature and extent of inherited (sub)seafloor hydrothermal processes, and by the possibility of deep fluids to be channelized along inherited or newly-formed discontinuities. Fluid channelization along inherited discontinuities controlled local rehydration and dehydration/decarbonation reactions and the stability of carbonate and silicate minerals at the blueschist-eclogite transition. Fluid-mediated decarbonation was driven by upward, up-temperature fluid flow in the inverted geothermal gradient of a subducting oceanic slab, a process that has not been documented in natural samples to date. We estimate that the observed fluid-rock reactions released 20-60 kg CO2 per m3 of rock (i.e. 0.7-2.1 wt% CO2), which is in line with the values predicted from decarbonation of metabasalts in open systems at these depths. Conversely, the estimated time-integrated fluid fluxes (20-50 t/m2) indicate that the amount of carbon transported by channelized fluid flow within the volcanic part of subducting oceanic plates is potentially much higher than previous numerical estimates, testifying to the percolation of C-bearing fluids resulting from devolatilization/dissolution processes operative in large reservoirs.

Early to middle Miocene climate evolution: New insights from IODP Sites U1335, U1337 and U1338 (eastern equatorial Pacific Ocean)

NASA Astrophysics Data System (ADS)

Kochhann, Karlos G. D.; Holbourn, Ann; Kuhnt, Wolfgang; Lyle, Mitch; Raffi, Isabella; Channell, James E.; Andersen, Nils

2015-04-01

The lower to middle Miocene (~20 to 13 Ma) carbonate-rich sedimentary successions recovered at Integrated Ocean Drilling Program (IODP) Sites U1335, U1337 and U1338 allow unsurpassed resolution over the Climatic Optimum (16.9-14.7 Ma) and the transition into a colder climate mode after 13.9 Ma with re-establishment of permanent Antarctic ice sheets. High-resolution (1-10 kyr) stable carbon (δ13C) and oxygen (δ18O) isotopes of well-preserved epibenthic foraminifera (Cibicidoides mundulus and Planulina wuellerstorfi) from these three sites show that the Climatic Optimum was characterized by high-amplitude climate variations and intense perturbations of the carbon cycle. Episodes of peak warmth coincided with transient shoaling of the carbonate compensation depth and enhanced carbonate dissolution in the deep ocean. The U1335 and U1337 records additionally reveal that the rapid global warming and/or polar ice melting event, marking the onset of the Climatic Optimum at ~16.9 Ma, was coupled to a massive increase in carbonate dissolution, indicated by sharp drops in carbonate percentages and accumulation rates and by the fragmentation or complete dissolution of planktonic foraminifers. After ~14.7 Ma, stepwise global cooling, culminating with extensive ice growth over Antarctica at ~13.8 Ma, coincide with enhanced opal and benthic foraminiferal accumulation rates, suggesting that increased siliceous productivity and organic carbon burial may have contributed to CO2 drawdown. Integration of age models derived from orbitally-tuned, high-resolution isotopes, biostratigraphic data and magnetic reversals allows further constraints on the temporal sequence of events and helps unravel the drivers of early to middle Miocene climate variations.

Numerical modelling of physiological and ecological impacts of ocean acidification on coccolithophores

NASA Astrophysics Data System (ADS)

Furukawa, Makoto; Sato, Toru; Suzuki, Yoshimi; Casareto, Beatriz E.; Hirabayashi, Shinichiro

2018-06-01

Ocean surface acidification due to increasing atmospheric CO2 concentration is currently attracting much attention. Coccolithophores distribute widely across the world's oceans and represent a carbon sink containing about 100 million tonnes of carbon. For this reason, there is concern about dissolution of their shells, which are made of calcium carbonate, due to decreasing pH. In this study, intracellular calcification, photosynthesis, and mass transport through biomembranes of Emiliania huxleyi were modelled numerically for understanding biological response in calcifying organisms. Unknown parameters were optimised by a generic algorithm to match existing experimental results. The model showed that the production of calcium carbonate rather than its dissolution is promoted under an acidified environment. Calcite remains at saturation levels in a coccolith even when it is below saturation levels in the external seawater. Furthermore, a coccolith can dissolve even in water where calcite saturation exceeds 1, because the saturation may be below the threshold level locally around the cell membrane. The present model also showed that the different calcification rates of E. huxleyi with respect to rising CO2 concentrations reported in the literature are due to differences in experimental conditions; in particular, how the CO2 concentration is matched. Lastly, the model was able to reproduce differences in calcification rates among coccolithophore species. The above biochemical-kinetic model was then incorporated into an ecosystem model, and the behaviour of coccolithophores in the ecosystem and the influence of increases in CO2 concentration on water quality were simulated and validated by comparison with existing experimental results. The model also suggests that increased CO2 concentration could lead to an increase in the biomass ratio of coccolithophores to diatoms at high CO2 concentrations, particularly in oligotrophic environments, and to a consequent decrease in pH due to calcium dissolution.

Deepwater carbonate ion concentrations in the western tropical Pacific since 250 ka: Evidence for oceanic carbon storage and global climate influence

NASA Astrophysics Data System (ADS)

Qin, Bingbin; Li, Tiegang; Xiong, Zhifang; Algeo, Thomas J.; Chang, Fengming

2017-04-01

We present new "size-normalized weight" (SNW)-Δ[CO32-] core-top calibrations for three planktonic foraminiferal species and assess their reliability as a paleo-alkalinity proxy. SNWs of Globigerina sacculifer and Neogloboquadrina dutertrei can be used to reconstruct past deep Pacific [CO32-], whereas SNWs of Pulleniatina obliquiloculata are controlled by additional environmental factors. Based on this methodological advance, we reconstruct SNW-based deepwater [CO32-] for core WP7 from the western tropical Pacific since 250 ka. Secular variation in the SNW proxy documents little change in deep Pacific [CO32-] between the Last Glacial Maximum and the Holocene. Further back in time, deepwater [CO32-] shows long-term increases from marine isotope stage (MIS) 5e to MIS 3 and from early MIS 7 to late MIS 6, consistent with the "coral reef hypothesis" that the deep Pacific Ocean carbonate system responded to declining shelf carbonate production during these two intervals. During deglaciations, we have evidence of [CO32-] peaks coincident with Terminations 2 and 3, which suggests that a breakdown of oceanic vertical stratification drove a net transfer of CO2 from the ocean to the atmosphere, causing spikes in carbonate preservation (i.e., the "deglacial ventilation hypothesis"). During MIS 4, a transient decline in SNW-based [CO32-], along with other reported [CO32-] and/or dissolution records, implies that increased deep-ocean carbon storage resulted in a global carbonate dissolution event. These findings provide new insights into the role of the deep Pacific in the global carbon cycle during the late Quaternary.

Plankton dynamics and biogeochemical fluxes in the Costa Rica Dome: introduction to the CRD Flux and Zinc Experiments.

PubMed

Landry, Michael R; De Verneil, Alain; Goes, Joaquim I; Moffett, James W

2016-03-01

The Costa Rica Dome (CRD) is an open-ocean upwelling system in the Eastern Tropical Pacific that overlies the ocean's largest oxygen minimum zone (OMZ). The region has unique characteristics, biomass dominance by picophytoplankton, suppressed diatoms, high biomass of higher consumers and presumptive trace metal limitation, but is poorly understood in terms of pelagic stock and process relationships, including productivity and production controls. Here, we describe the goals, project design, physical context and major findings of the Flux and Zinc Experiments cruise conducted in June-July 2010 to assess trophic flux relationships and elemental controls on phytoplankton in the CRD. Despite sampling during a year of suppressed summertime surface chlorophyll, cruise results show high productivity (∼1 g C m -2 day -1 ), high new production relative to export, balanced production and grazing, disproportionate biomass-specific productivity of large phytoplankton and high zooplankton stocks. Zinc concentrations are low in surface waters relative to phosphorous and silicate in other regions, providing conditions conducive to picophytoplankton, like Synechococcus , with low Zn requirements. Experiments nonetheless highlight phytoplankton limitation or co-limitation by silicic acid, driven by a strong silica pump that is linked to low dissolution of biogenic silica in the cold shallow thermocline of the lower euphotic zone.

Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay.

PubMed

Cai, Wei-Jun; Huang, Wei-Jen; Luther, George W; Pierrot, Denis; Li, Ming; Testa, Jeremy; Xue, Ming; Joesoef, Andrew; Mann, Roger; Brodeur, Jean; Xu, Yuan-Yuan; Chen, Baoshan; Hussain, Najid; Waldbusser, George G; Cornwell, Jeffrey; Kemp, W Michael

2017-08-28

The combined effects of anthropogenic and biological CO 2 inputs may lead to more rapid acidification in coastal waters compared to the open ocean. It is less clear, however, how redox reactions would contribute to acidification. Here we report estuarine acidification dynamics based on oxygen, hydrogen sulfide (H 2 S), pH, dissolved inorganic carbon and total alkalinity data from the Chesapeake Bay, where anthropogenic nutrient inputs have led to eutrophication, hypoxia and anoxia, and low pH. We show that a pH minimum occurs in mid-depths where acids are generated as a result of H 2 S oxidation in waters mixed upward from the anoxic depths. Our analyses also suggest a large synergistic effect from river-ocean mixing, global and local atmospheric CO 2 uptake, and CO 2 and acid production from respiration and other redox reactions. Together they lead to a poor acid buffering capacity, severe acidification and increased carbonate mineral dissolution in the USA's largest estuary.The potential contribution of redox reactions to acidification in coastal waters is unclear. Here, using measurements from the Chesapeake Bay, the authors show that pH minimum occurs at mid-depths where acids are produced via hydrogen sulfide oxidation in waters mixed upward from anoxic depths.

Developing dissolution testing methodologies for extended-release oral dosage forms with supersaturating properties. Case example: Solid dispersion matrix of indomethacin.

PubMed

Tajiri, Tomokazu; Morita, Shigeaki; Sakamoto, Ryosaku; Mimura, Hisahi; Ozaki, Yukihiro; Reppas, Christos; Kitamura, Satoshi

2015-07-25

The objective of this study was to develop an in vitro dissolution test method with discrimination ability for an extended-release solid dispersion matrix of a lipophilic drug using the United States Pharmacopeia (USP) Apparatus 4, flow-through cell apparatus. In the open-loop configuration, the sink condition was maintained by manipulating the flow rate of the dissolution medium. To evaluate the testing conditions, the drug release mechanism from an extended-release solid dispersion matrix containing hydrophobic and hydrophilic polymers was investigated. As the hydroxypropyl methylcellulose (HPMC) maintained concentrations of indomethacin higher than the solubility in a dissolution medium, the release of HPMC into the dissolution medium was also quantified using size-exclusion chromatography. We concluded that the USP Apparatus 4 is suitable for application to an in vitro dissolution method for orally administered extended-release solid dispersion matrix formulations containing poorly water-soluble drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

Coral reef sediment dissolution: Insights from chamber incubations around the globe

NASA Astrophysics Data System (ADS)

Cyronak, T.; Andersson, A. J.; Eyre, B.

2016-02-01

Ocean acidification (OA) is expected to negatively affect the calcium carbonate (CaCO3) budget of coral reefs by decreasing calcification and increasing CaCO3 dissolution rates. Sediments represent the largest reservoir of CaCO3 in coral reefs and form important habitats above and below the hide tide mark. Results from in situ benthic incubations at different coral reef locations around the world (Australia, Tahiti, Bermuda, Cook Islands, and Hawaii) reveal that there is a general trend between bulk seawater aragonite saturation state (Ωar) and net CaCO3 sediment dissolution rates. Experimental incubations also indicate that the ratio of production to respiration (P/R) in the sediments plays a significant role in CaCO3 dissolution, with high P/R ratios potentially offsetting the effects of human induced OA. This is most likely due to benthic microalgae photosynthesizing and consuming CO2, which produces conditions more favourable for CaCO3 precipitation in sediment pore waters. Despite any interactions with benthic organic metabolism, sediment dissolution could be an order of magnitude more sensitive to OA compared to the process of biogenic calcification. Increases in CaCO3 sediment dissolution under predicted CO2 emissions could shift the net ecosystem calcification (NEC) of coral reefs from net CaCO3 precipitating to net dissolving by the end of this century.

Fractionation of iron isotopes during leaching of natural particles by acidic and circumneutral leaches and development of an optimal leach for marine particulate iron isotopes

NASA Astrophysics Data System (ADS)

Revels, Brandi N.; Zhang, Ruifeng; Adkins, Jess F.; John, Seth G.

2015-10-01

Iron (Fe) is an essential nutrient for life on land and in the oceans. Iron stable isotope ratios (δ56Fe) can be used to study the biogeochemical cycling of Fe between particulate and dissolved phases in terrestrial and marine environments. We have investigated the dissolution of Fe from natural particles both to understand the mechanisms of Fe dissolution, and to choose a leach appropriate for extracting labile Fe phases of marine particles. With a goal of finding leaches which would be appropriate for studying dissolved-particle interactions in an oxic water column, three particle types were chosen including oxic seafloor sediments (MESS-3), terrestrial dust (Arizona Test Dust - A2 Fine), and ocean sediment trap material from the Cariaco basin. Four leaches were tested, including three acidic leaches similar to leaches previously applied to marine particles and sediments (25% acetic acid, 0.01 N HCl, and 0.5 N HCl) and a pH 8 oxalate-EDTA leach meant to mimic the dissolution of particles by organic complexation, as occurs in natural seawater. Each leach was applied for three different times (10 min, 2 h, 24 h) at three different temperatures (25 °C, 60 °C, 90 °C). MESS-3 was also leached under various redox conditions (0.02 M hydroxylamine hydrochloride or 0.02 M hydrogen peroxide). For all three sample types tested, we find a consistent relationship between the amount of Fe leached and leachate δ56Fe for all of the acidic leaches, and a different relationship between the amount of Fe leached and leachate δ56Fe for the oxalate-EDTA leach, suggesting that Fe was released through proton-promoted dissolution for all acidic leaches and by ligand-promoted dissolution for the oxalate-EDTA leach. Fe isotope fractionations of up to 2‰ were observed during acidic leaching of MESS-3 and Cariaco sediment trap material, but not for Arizona Test Dust, suggesting that sample composition influences fractionation, perhaps because Fe isotopes are greatly fractionated during leaching of silicates and clays but only minimally fractionated during dissolution of Fe oxyhydroxides. Two different analytical models were developed to explain the relationship between amount of Fe leached and δ56Fe, one of which assumes mixing between two Fe phases with different δ56Fe and different dissolution rates, and the other of which assumes dissolution of a single phase with a kinetic isotope effect. We apply both models to fit results from the acidic leaches of MESS-3 and find that the fit for both models is very similar, suggesting that isotope data will never be sufficient to distinguish between these two processes for natural materials. Next, we utilize our data to choose an optimal leach for application to marine particles. The oxalate-EDTA leach is well-suited to this purpose because it does not greatly fractionate Fe isotopes for a diversity of particle types over a wide variety of leaching conditions, and because it approximates the conditions by which particulate Fe dissolves in the oceans. We recommend a 2 h leach at 90 °C with 0.1 M oxalate and 0.05 M EDTA at pH 8 to measure labile ;ligand-leachable; particulate δ56Fe on natural marine materials with a range of compositions.

Molybdenum isotope behaviour in groundwaters and terrestrial hydrothermal systems, Iceland

NASA Astrophysics Data System (ADS)

Neely, Rebecca A.; Gislason, Sigurdur R.; Ólafsson, Magnus; McCoy-West, Alex J.; Pearce, Christopher R.; Burton, Kevin W.

2018-03-01

Molybdenum (Mo) isotopes have proved useful in the reconstruction of paleoredox conditions. Their application generally relies upon a simplified model of ocean inputs in which rivers dominate Mo fluxes to the oceans and hydrothermal fluids are considered to be a minor contribution. To date, however, little attention has been paid to the extent of Mo isotope variation of hydrothermal waters, or to the potential effect of direct groundwater discharge to the oceans. Here we present Mo isotope data for two Icelandic groundwater systems (Mývatn and Þeistareykir) that are both influenced by hydrothermal processes. Relative to NIST 3134 = +0.25‰, the cold (<10 °C) groundwaters (δ98/95MoGROUNDWATER = -0.15‰ to +0.47‰; n = 13) show little, if any, fractionation from the host basalt (δ 98 / 95MoBASALT = +0.16‰ to -0.12‰) and are, on average, lighter than both global and Icelandic rivers. In contrast, waters that are hydrothermally influenced (>10 °C) possess isotopically heavy δ98/95MoHYDROTHERMAL values of +0.25‰ to +2.06‰ (n = 18) with the possibility that the high temperature endmembers are even heavier. Although the mechanisms driving this fractionation remain unresolved, the incongruent dissolution of the host basalt and both the dissolution and precipitation of sulfides are considered. Regardless of the processes driving these variations, the δ98Mo data presented in this study indicate that groundwater and hydrothermal waters have the potential to modify ocean budget calculations.

Sedimentary particulate iron: the missing micronutrients ?

NASA Astrophysics Data System (ADS)

Beghoura, Houda; Gorgues, Thomas; Aumont, Olivier; Planquette, Hélène

2017-04-01

Iron is known to regulate the marine primary production and to impact the structure of ecosystems. Indeed, iron is the limiting nutrient for the phytoplankton growth over about 30% of the global ocean. However, the nature of the external sources of iron to the ocean and their quantification remain uncertain. Among these external sources, the sediment sources have been recently shown to be underestimated. Besides, since the operationally defined dissolved iron (which is the sum of truly dissolved and colloidal iron) was traditionally assumed to be the only form available to phytoplankton and bacteria, most studies have focused on the supply of dissolved iron to the ocean, the role of the particulate fraction of iron being largely ignored. This traditional view has been recently challenged, noticeably, by observational evidences. Indeed, in situ observations have shown that large amounts of particulate iron are being resuspended from continental margins to the open ocean thanks to fine grained particles' transport over long distances. A fraction of this particulate iron may dissolve and thereby fuel the phytoplankton growth. The magnitude of the sedimentary sources of particulate iron and the releasing processes affecting this iron phase are not yet well constrained or quantified. As a consequence, the role of sedimentary particulate iron in the biogeochemical cycles is still unclear despite its potentially major widespread importance. Here, we propose a modeling exercise to assess the first order impacts of this newly considered particulate sedimentary iron on global ocean biogeochemistry. We designed global experiments with a coupled dynamical-biogeochemical model (NEMO-PISCES). First, a control simulation that includes only a sediment source of iron in the dissolved phase has been run. Then, this control simulation is being compared with simulations, in which we include a sediment source of iron in both phases (dissolved as well as particulate). Those latter simulations have been performed using a range of particulate iron dissolution rates (from published studies and laboratory experiment results) that will permit to test the sensitivity of the biogeochemical response.

Contrasts in the Sensitivity of Community Calcification to Temporal Saturation State Variability Within Temperate and Tropical Marine Environments

NASA Astrophysics Data System (ADS)

Kwiatkowski, L.

2016-02-01

Ongoing emissions of carbon dioxide (CO2) and invasion of part of this CO2 into the oceans are projected to lower the calcium carbonate saturation state. As a result, the ability of many marine organisms to calcify may be compromised, with significant impacts on ocean ecosystems throughout the 21st Century. In laboratory manipulations, calcifying organisms have exhibited reduced calcification under elevated pCO2 conditions. Consequently, in situ observations of the sensitivity of calcifying communities to natural saturation state variability are increasingly valued as they incorporate complex species interactions, and capture the carbonate chemistry conditions to which communities are acclimatized. Using intensive seawater sampling techniques we assess the community level sensitivity of calcification rates to natural temporal variability in the aragonite saturation state (Ωarag) at both a tropical coral reef and temperate intertidal study site. Both sites experiences large daily variation in Ωarag during low tide due to photosynthesis, respiration, and the time at which the sites are isolated from the open ocean. On hourly timescales, we find that community level rates of calcification have only a weak dependence on variability in Ωarag at the tropical study site. At the temperate study site, although limited Ωarag sensitivity is observed during the day, nighttime community calcification rates are found to be strongly influenced by variability in Ωarag, with greater dissolution rates at lower Ωarag levels. If the short-term sensitivity of community calcification to Ωarag described here is representative of the long-term sensitivity of marine ecosystems to ocean acidification, then one would expect temperate intertidal calcifying communities to be more vulnerable than tropical coral reef calcifying communities. In particular, reductions in net community calcification, in the temperate intertidal zone may be predominately due to the nocturnal impact of ocean acidification.

Biogeography of Radiolaria Polycystina (Protista) in the World Ocean

NASA Astrophysics Data System (ADS)

Boltovskoy, Demetrio; Correa, Nancy

2016-12-01

Analysis of 307 species of Radiolaria Polycystina in a worldwide dataset of 4774 plankton, sediment trap, and surface sediment samples allows recognizing six major biogeographic Domains. Five of them are circumglobal (Polar North, Polar South, Bi-Subpolar, Transitional and Tropical-Subtropical), and one is restricted to the Eastern Equatorial Pacific. Each Domain is characterized by a particular suite of species, all of which, however, occur widely, albeit sparsely, in one or more other Domains. Of the eight environmental variables evaluated, temperature correlates best with the partitions established. Species distributions in the water column and in the sediments are generally in agreement, but in the sediments cold water forms extend farther towards the equator than do warm water radiolarians towards the poles. In the Recent sedimentary record of planktonic Foraminifera the same phenomenon is magnified by the higher dissolution rates of warm water species, as compared with the cold water ones. Of the three major oceans, the Pacific was the most speciose, but estimates based on data corrected for sample-size show much smaller inter-oceanic differences, with ∼10 radiolarians probably being absent from either basin. The radiolarian biogeographic pattern is generally similar to those based on other planktonic and nektonic open-ocean organisms, but the degree of uniqueness of the Domains, as well as the position of the intervening boundaries, are variable, which reflects methodological differences, as well as taxon-specific traits. Partitions of the World Ocean defined on the basis of species ranges resemble the major divisions (presumably functionally homogeneous units) established on the basis of physical traits and chlorophyll fields, but secondary divisions nested within the latter are not reflected by any of the biogeographic schemes based on species distribution ranges. This conflict raises questions about the importance of several physical mechanisms for structuring pelagic communities, and/or on the coupling of structure and function in the pelagic realm.

The Relationship Between the Evolution of an Internal Structure and Drug Dissolution from Controlled-Release Matrix Tablets.

PubMed

Kulinowski, Piotr; Hudy, Wiktor; Mendyk, Aleksander; Juszczyk, Ewelina; Węglarz, Władysław P; Jachowicz, Renata; Dorożyński, Przemysław

2016-06-01

In the last decade, imaging has been introduced as a supplementary method to the dissolution tests, but a direct relationship of dissolution and imaging data has been almost completely overlooked. The purpose of this study was to assess the feasibility of relating magnetic resonance imaging (MRI) and dissolution data to elucidate dissolution profile features (i.e., kinetics, kinetics changes, and variability). Commercial, hydroxypropylmethyl cellulose-based quetiapine fumarate controlled-release matrix tablets were studied using the following two methods: (i) MRI inside the USP4 apparatus with subsequent machine learning-based image segmentation and (ii) dissolution testing with piecewise dissolution modeling. Obtained data were analyzed together using statistical data processing methods, including multiple linear regression. As a result, in this case, zeroth order release was found to be a consequence of internal structure evolution (interplay between region's areas-e.g., linear relationship between interface and core), which eventually resulted in core disappearance. Dry core disappearance had an impact on (i) changes in dissolution kinetics (from zeroth order to nonlinear) and (ii) an increase in variability of drug dissolution results. It can be concluded that it is feasible to parameterize changes in micro/meso morphology of hydrated, controlled release, swellable matrices using MRI to establish a causal relationship between the changes in morphology and drug dissolution. Presented results open new perspectives in practical application of combined MRI/dissolution to controlled-release drug products.

Mineral dissolution and precipitation in carbonate dominated terranes assessed using Mg isotopes

NASA Astrophysics Data System (ADS)

Tipper, E.; Calmels, D.; Gaillardet, J.; Galy, A.

2013-12-01

Carbonate weathering by carbonic acid consumes atmospheric CO2 during mineral dissolution, fixing it as aqueous bicarbonate over millennial time-scales. Ocean acidification has increased the solubility of CO2 in seawater by changing the balance of pH to alkalinity (the oceanic reservoir of carbon). This has lengthened the time-scale for CO2 sequestration by carbonate weathering to tens of thousands of years. At a global scale, the net consumption of CO2 is at least equal to that from silicate weathering, but there is far less work on carbonate weathering compared to silicate weathering because it has generally been assumed to be CO2 neutral on geological time-scales. Carbonate rocks are more readily dissolved than silicate rocks, meaning that their dissolution will likely respond much more rapidly to global environmental change when compared with the dissolution of silicate minerals. Although far less concentrated than Ca in many carbonates, Mg substitutes for Ca and is more concentrated than any other metal ion. Tracing the behavior of Mg in river waters, using Mg stable isotopes (26Mg/24Mg ratio expressed as delta26Mg in per mil units) is therefore a novel way to understand the complex series of dissolution/precipitation reactions that govern solute concentrations of Ca and Mg, and hence CO2 transfer by carbonate weathering. We present new Mg isotope data on a series of river and spring waters from the Jura mountains in North-East France. The stratigraphic column is relatively uniform throughout the Jura mountains and is dominated by limestones. As the limestone of the Jura Mountains were deposited in high-energy shallow water environments (shore line, lagoon and coral reefs), they are usually clay and organic poor. The delta26Mg of the local rocks is very constant at circa -4permil. The delta26Mg of the river waters is also fairly constant, but offset from the rock at -2.5permil. This is an intriguing observation because the dissolution of limestones is expected to be congruent, meaning that the Mg released to solutes during mineral dissolution should have the same composition as the host rock. Some of this difference is likely accounted for by atmospheric deposition or cyclic inputs, but this cannot account for all of the 1.5permil shift between rock and water. It is plausible that some of the difference is explained by trace levels of Mg-silicate dissolution (with a delta26Mg of circa 0permil), but equally carbonate precipitation and attendant Mg isotope fractionation could theoretically account for the difference between rock and water. The various plausible explications will be discussed, as well as the implications of the data for better understanding carbonate weathering.

On the influence of etch pits in the overall dissolution rate of apatite basal sections

NASA Astrophysics Data System (ADS)

Alencar, Igor; Guedes, Sandro; Palissari, Rosane; Hadler, Julio C.

2015-09-01

Determination of efficiencies for particle detection plays a central role for proper estimation of reaction rates. If chemical etching is employed in the revelation of latent particle tracks in solid-state detectors, dissolution rates and etchable lengths are important factors governing the revelation and observation. In this work, the mask method, where a reference part of the sample is protected during dissolution, was employed to measure step heights in basal sections of apatite etched with a nitric acid, HNO, solution at a concentration of 1.1 M and a temperature of 20 °C. We show a drastic increase in the etching velocity as the number of etch pits in the surface augments, in accordance with the dissolution stepwave model, where the outcrop of each etch pit generates a continuous sequence of stepwaves. The number of etch pits was varied by irradiation with neutrons and perpendicularly incident heavy ions. The size dependence of the etch-pit opening with etching duration for ion (200-300 MeV 152Sm and 238U) tracks was also investigated. There is no distinction for the etch pits between the different ions, and the dissolution seems to be governed by the opening velocity when a high number of etch pits are present in the surface. Measurements of the etchable lengths of these ion tracks show an increase in these lengths when samples are not pre-annealed before irradiation. We discuss the implications of these findings for fission-track modelling.

Quality-by-design case study: investigation of the role of poloxamer in immediate-release tablets by experimental design and multivariate data analysis.

PubMed

Kaul, Goldi; Huang, Jun; Chatlapalli, Ramarao; Ghosh, Krishnendu; Nagi, Arwinder

2011-12-01

The role of poloxamer 188, water and binder addition rate, on retarding dissolution in immediate-release tablets of a model drug from BCS class II was investigated by means of multivariate data analysis (MVDA) combined with design of experiments (DOE). While the DOE analysis yielded important clues into the cause-and-effect relationship between the responses and design factors, multivariate data analysis of the 40+ variables provided additional information on slowdown in tablet dissolution. A steep dependence of both tablet dissolution and disintegration on the poloxamer and less so on other design variables was observed. Poloxamer was found to increase dissolution rates in granules as expected of surfactants in general but retard dissolution in tablets. The unexpected effect of poloxamer in tablets was accompanied by an increase in tablet-disintegration-time-mediated slowdown of tablet dissolution and by a surrogate binding effect of poloxamer at higher concentrations. It was additionally realized through MVDA that poloxamer in tablets either acts as a binder by itself or promotes binder action of the binder povidone resulting in increased intragranular cohesion. Additionally, poloxamer was found to mediate tablet dissolution on stability as well. In contrast to tablet dissolution at release (time zero), poloxamer appeared to increase tablet dissolution in a concentration-dependent manner on accelerated open-dish stability. Substituting polysorbate 80 as an alternate surfactant in place of poloxamer in the formulation was found to stabilize tablet dissolution.

Zebra textures in carbonate rocks: Fractures produced by the force of crystallization during mineral replacement

NASA Astrophysics Data System (ADS)

Wallace, Malcolm W.; Hood, Ashleigh v. S.

2018-06-01

Zebra textures are enigmatic banded fabrics that occur in many carbonate-hosted ore deposits, dolomite hydrocarbon reservoirs and carbonate successions globally. They consist of a variety of minerals and are characterised by parallel light and dark bands that occur at a millimetre- to centimetre-scale. Based on petrological evidence, there is general consensus that the dark bands formed by replacement of the carbonate host rock. Historically, more contention surrounds the origin of the light bands, but the dominant view is that these are mineral-filled cavities, which is supported by overwhelming textural evidence. Overall, the feature common to all versions of zebra textures is mineral replacement of the original carbonate host. We suggest that mineral replacement (and the force of crystallization) in association with open space generation is a viable mechanism for the development of zebra cavity systems. Dissolution and open space generation in either evaporites or carbonates adjacent to the site of replacement reactions is necessary to remove the confining pressure from the rock and to allow the development of fractures. The pressure of the growing replacement crystals within the carbonate pervasively splits the carbonate apart, producing thin strips of carbonate surrounded by open space. The fractures may then be subject to dissolution and are later filled by cements. Very regular stratabound zebra textures (as found in ore deposits like Cadjebut, Australia and San Vicente, Peru) may be related to stratabound dissolution (of evaporites or carbonates), whereas irregularly distributed zebra textures are more likely to be associated with irregular carbonate dissolution.

Partial melting of lower oceanic crust gabbro: Constraints from poikilitic clinopyroxene primocrysts

NASA Astrophysics Data System (ADS)

Leuthold, Julien; Lissenberg, C. Johan; O'Driscoll, Brian; Karakas, Ozge; Falloon, Trevor; Klimentyeva, Dina N.; Ulmer, Peter

2018-03-01

Successive magma batches underplate, ascend, stall and erupt along spreading ridges, building the oceanic crust. It is therefore important to understand the processes and conditions under which magma differentiates at mid ocean ridges. Although fractional crystallization is considered to be the dominant mechanism for magma differentiation, open-system igneous complexes also experience Melting-Assimilation-Storage-Hybridization (MASH, Hildreth and Moorbath, 1988) processes. Here, we examine crystal-scale records of partial melting in lower crustal gabbroic cumulates from the slow-spreading Atlantic oceanic ridge (Kane Megamullion; collected with Jason ROV) and the fast-spreading East Pacific Rise (Hess Deep; IODP expedition 345). Clinopyroxene oikocrysts in these gabbros preserve marked intra-crystal geochemical variations that point to crystallization-dissolution episodes of the gabbro eutectic assemblage. Kane Megamullion and Hess Deep clinopyroxene core1 primocrysts and their plagioclase inclusions indicate crystallization from high temperature basalt (>1160 and >1200°C, respectively), close to clinopyroxene saturation temperature (<50% and <25% crystallization). Step-like compatible Cr (and co-varying Al) and incompatible Ti, Zr, Y and rare earth elements (REE) decrease from anhedral core1 to overgrown core2, while Mg# and Sr/Sr* ratios increase. We show that partial resorption textures and geochemical zoning result from partial melting of REE-poor lower oceanic crust gabbroic cumulate (protolith) following intrusion by hot primitive mantle-derived melt, and subsequent overgrowth crystallization (refertilization) from a hybrid melt. In addition, towards the outer rims of crystals, Ti, Zr, Y and the REE strongly increase and Al, Cr, Mg#, Eu/Eu* and Sr/Sr* decrease, suggesting crystallization either from late-stage percolating relatively differentiated melt or from in situ trapped melt. Intrusion of primitive hot reactive melt and percolation of interstitial differentiated melt are two distinct MASH processes in the lower oceanic crust. They are potentially fundamental mechanisms for generating the wide compositional variation observed in mid-ocean ridge basalts. We furthermore propose that such processes operate at both slow- and fast-spreading ocean ridges. Thermal numerical modelling shows that the degree of lower crustal partial melting at slow-spreading ridges can locally increase up to 50%, but the overall crustal melt volume is low (less than ca. 5% of total mantle-derived and crustal melts; ca. 20% in fast-spreading ridges).

Models and Experiments of Melt-Rock Interaction in the Lower Oceanic Crust

NASA Astrophysics Data System (ADS)

Orton, W. H., II; Liang, Y.; Sanfilippo, A.

2017-12-01

Understanding the processes of melt-rock interaction in the lower oceanic crust isimportant to the interpretation of mid-ocean ridge basalt (MORB) and the petrogenesis of lowercrustal cumulates. Petrologic and geochemical studies of cumulates from the lower crustalregions of oceanic lithosphere have identified a number of textural and chemical features that arepertinent to melt-rock reaction (e.g., high-Mg# clinopyroxene oikocrysts within local gabbroicregions in troctolite bodies). The purpose of the present study is to provide some referenceexamples of MORB melt and cumulate mush interaction under controlled conditions. Suchsimple experiments are useful in sorting out crystallization, dissolution, re-precipitation, anddiffusion processes in the cumulate mush and in developing better models for melt transport andmelt-rock interaction in the lower oceanic crust.We performed piston cylinder experiments at 0.5-0.7 GPa and 1000-1250°C reacting anolivine or olivine + plagioclase cumulate mush and an intruding MORB melt in a graphite-linedmolybdenum capsule. Our experiments consist of two steps: (1) reaction at 1250°C for 10 to 24hours; and (2) reactive crystallization to a lower temperature through controlled cooling overseveral days. Cooling promotes in situ crystallization of interstitial melts, allowing us to bettercharacterize the mineral compositional trends produced and observed by melt-rock reaction andcrystallization. Reaction at 1250°C produced an olivine + melt mush with small rounded crystalscharacteristic of dissolution. Significant crystal settling was also observed at large melt-to- rockratio. Cooling with continued reaction resulted in the formation of a plagioclase matrix withpoikilitic clinopyroxene oikocrysts containing plagioclase and relict olivine as chadacrysts.Clinopyroxenes were in a reaction relationship with both plagioclase and olivine. In somesamples, multiple phases of clinopyroxene and plagioclase were present, each with differentcompositions, similar to those observed in the field-based studies. With these insights, a modelfor melt transport and melt-rock interaction in the lower oceanic crust has been developed andwill be used to study major and trace element fractionation during reactive melt migration in thecumulate mush.

Megafauna recovered from a cold hydrocarbon seep in the deep Alaskan Beaufort Sea, including a new species of Axinus (Thracidae: Bivalvia: Mollusca)

NASA Astrophysics Data System (ADS)

Powell, C. L.; Valentich-Scott, P.; Lorenson, T. D.; Edwards, B. D.

2011-12-01

Several specimens of a new species of Axinus and a single well-worn gastropod columella provisionally assigned to the genus Neptunea (Buccinidae: Gastropoda: Mollusca) were recently recovered from at least two cores, the longest of which is 5.72 m long, from a large seafloor mound, informally named the Canning Seafloor Mound (CSM). The CSM is located at 2,530 m water depth on the Alaskan Beaufort Sea slope north of Camden Bay and is a fluid explosion feature containing methane hydrate and methane-saturated sediments overlying a folded and faulted deep basin. Only two modern species of Axinus are currently known. Axinus grandis (Verrill & Smith, 1885) is a northern Atlantic species and the recently described species, A. cascadiensis Oliver and Holmes (2007), is only known from Baby Bare Seamount, Cascadia Basin, northeastern Pacific Ocean. Common fragments, single valves, and a single articulated specimen represent this new Axinus species. These shells were distributed over nearly the entire length of the primary core. All specimens show wear and (or) dissolution. The age of these specimens is unknown and no living representatives were encountered. The genus Axinus has a fossil record back to the early Eocene in England and the Paleocene and Eocene in Egypt. Biogeographically the genus appears to have originated in the Tethys Sea and became established in the Atlantic Ocean during the Eocene, spreading across the Arctic Ocean in the late Tertiary. With the opening of the Bering Strait in the latest Miocene or early Pliocene the genus Axinus migrated southwest into the northeast Pacific. Interestingly, hydrocarbon seep deposits are also present on the adjacent North Slope of Alaska in the Marsh Anticline at Carter Creek, Camden Bay. These rocks, the Nuwok beds, contain abundant Thracidae bivalve of the genus Thracia, but not Axinus, however the rocks also represent cold seep deposits. These rocks have been variously dated from Oligocene to Pliocene and the exact age remains uncertain. Neptunea are a predatory snails well represented in the earliest Miocene to Holocene of the northern Pacific Ocean and in the late Pliocene to Holocene of the northern Atlantic. The presence of Neptunea at CSM, if identified properly, gives a maximum age for these deposits of latest Miocene or early Pliocene, after the opening of the Bering Strait, although they could be as young as Holocene.

Dynamic morphology of gas hydrate on a methane bubble in water: Observations and new insights for hydrate film models

NASA Astrophysics Data System (ADS)

Warzinski, Robert P.; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J.; Levine, Jonathan S.

2014-10-01

Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of hydrate on rising bubbles that can enhance their survival in the water column, allowing gas to reach shallower depths and the atmosphere. The precise nature and influence of hydrate coatings on bubble hydrodynamics and dissolution is largely unknown. Here we present high-definition, experimental observations of complex surficial mechanisms governing methane bubble hydrate formation and dissociation during transit of a simulated oceanic water column that reveal a temporal progression of deep-sea controlling mechanisms. Synergistic feedbacks between bubble hydrodynamics, hydrate morphology, and coverage characteristics were discovered. Morphological changes on the bubble surface appear analogous to macroscale, sea ice processes, presenting new mechanistic insights. An inverse linear relationship between hydrate coverage and bubble dissolution rate is indicated. Understanding and incorporating these phenomena into bubble and bubble plume models will be necessary to accurately predict global greenhouse gas budgets for warming ocean scenarios and hydrocarbon transport from anthropogenic or natural deep-sea eruptions.

Open-ocean fish reveal an omnidirectional solution to camouflage in polarized environments.

PubMed

Brady, Parrish C; Gilerson, Alexander A; Kattawar, George W; Sullivan, James M; Twardowski, Michael S; Dierssen, Heidi M; Gao, Meng; Travis, Kort; Etheredge, Robert Ian; Tonizzo, Alberto; Ibrahim, Amir; Carrizo, Carlos; Gu, Yalong; Russell, Brandon J; Mislinski, Kathryn; Zhao, Shulei; Cummings, Molly E

2015-11-20

Despite appearing featureless to our eyes, the open ocean is a highly variable environment for polarization-sensitive viewers. Dynamic visual backgrounds coupled with predator encounters from all possible directions make this habitat one of the most challenging for camouflage. We tested open-ocean crypsis in nature by collecting more than 1500 videopolarimetry measurements from live fish from distinct habitats under a variety of viewing conditions. Open-ocean fish species exhibited camouflage that was superior to that of both nearshore fish and mirrorlike surfaces, with significantly higher crypsis at angles associated with predator detection and pursuit. Histological measurements revealed that specific arrangements of reflective guanine platelets in the fish's skin produce angle-dependent polarization modifications for polarocrypsis in the open ocean, suggesting a mechanism for natural selection to shape reflectance properties in this complex environment. Copyright © 2015, American Association for the Advancement of Science.

Framework of barrier reefs threatened by ocean acidification.

PubMed

Comeau, Steeve; Lantz, Coulson A; Edmunds, Peter J; Carpenter, Robert C

2016-03-01

To date, studies of ocean acidification (OA) on coral reefs have focused on organisms rather than communities, and the few community effects that have been addressed have focused on shallow back reef habitats. The effects of OA on outer barrier reefs, which are the most striking of coral reef habitats and are functionally and physically different from back reefs, are unknown. Using 5-m long outdoor flumes to create treatment conditions, we constructed coral reef communities comprised of calcified algae, corals, and reef pavement that were assembled to match the community structure at 17 m depth on the outer barrier reef of Moorea, French Polynesia. Communities were maintained under ambient and 1200 μatm pCO2 for 7 weeks, and net calcification rates were measured at different flow speeds. Community net calcification was significantly affected by OA, especially at night when net calcification was depressed ~78% compared to ambient pCO2 . Flow speed (2-14 cm s(-1) ) enhanced net calcification only at night under elevated pCO2 . Reef pavement also was affected by OA, with dissolution ~86% higher under elevated pCO2 compared to ambient pCO2 . These results suggest that net accretion of outer barrier reef communities will decline under OA conditions predicted within the next 100 years, largely because of increased dissolution of reef pavement. Such extensive dissolution poses a threat to the carbonate foundation of barrier reef communities. © 2015 John Wiley & Sons Ltd.

Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms.

PubMed

Orr, James C; Fabry, Victoria J; Aumont, Olivier; Bopp, Laurent; Doney, Scott C; Feely, Richard A; Gnanadesikan, Anand; Gruber, Nicolas; Ishida, Akio; Joos, Fortunat; Key, Robert M; Lindsay, Keith; Maier-Reimer, Ernst; Matear, Richard; Monfray, Patrick; Mouchet, Anne; Najjar, Raymond G; Plattner, Gian-Kasper; Rodgers, Keith B; Sabine, Christopher L; Sarmiento, Jorge L; Schlitzer, Reiner; Slater, Richard D; Totterdell, Ian J; Weirig, Marie-France; Yamanaka, Yasuhiro; Yool, Andrew

2005-09-29

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms--such as corals and some plankton--will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean-carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.

Interactions Between Biogenic Silica (BSiO2) and Organic Carbon (POC) During the Recycling of Sinking Particles

NASA Astrophysics Data System (ADS)

Moriceau, B.; Goutx, M.; Guigue, C.; Tamburini, C.; Lee, C.; Armstrong, R. A.; Duflos, M.; Charriere, B.; Ragueneau, O.

2006-12-01

Despite recent progress in understanding the ocean's role in the global carbon cycle, we are not yet able to predict the response of ecosystems to climate change and feedbacks of the ocean onto atmospheric CO2. In particular, particle flux dynamics must be represented more faithfully in ocean models. We know that particulate organic carbon (POC) flux is associated with ballast minerals (BSiO2, CaCO3), but the processes controlling the interactions between carbon and ballast minerals during decomposition must be explored further. The present study aims to provide a better understanding of interactions between carbon and BSiO2 during mineralization of sinking particles. Previous studies have provided evidence that the degradation of the external membrane by bacteria increase the BSiO2 dissolution rate. Alternatively, it has been hypothesized that biogenic silica could protect carbon from degradation. To test this hypothesis, an in-vitro batch experiment using the diatom Skeletonema costatum was conducted. In this experiment, carbon degradation, bacterial growth, and BSiO2 dissolution were followed simultaneously. To identify the processes involved and the types of carbon that eventually interact with BSiO2 during mineralization, the concentrations of different lipids and amino acids were also measured. A strong increase of the degradation rate constant of the POC and PON was observed after dissolution of 40 % of initial BSiO2. This increase is associated to a peak of glycine in total amino acids and a switch between free and attached bacteria. These results suggest that carbon degradation is increased when enough of the frustule is dissolved to uncover the glycine contain inside the frustule, this amino acid may trigger an increase in the concentration of attached bacteria, which may in turn increase the degradation rate constant of organic carbon.

Constraining metasomatism in the oceanic lithosphere

NASA Astrophysics Data System (ADS)

Plümper, Oliver; Beinlich, Andreas; Austrheim, Hâkon

2010-05-01

Serpentinization is the most prominent fluid-mediated alteration process in the oceanic lithosphere, but the physical and chemical conditions of this process are difficult to constrain. It is crucial to establish a framework of mineralogical markers that constrain (a) whether the reaction proceeded without substantial addition of elements from the fluid (isochemical), (b) the reaction is isovolumetric generating no internal stresses and (c) if the overall system was closed with respect to certain elements. We have examined ophiolitic metaperidotites from Norway, combining microtextural and microchemical observations to gain further insight into the complex fluid-mediated phase transformations occurring during the alteration of the oceanic lithosphere. Serpentinization can be isovolumetric, resulting in pseudomorphic mineral replacement reactions (e.g. Viti et al., 2005), or produce an observable volume increase (e.g. Shervais et al., 2005). In the case of olivine, the ideal reaction is commonly written as forsteritic olivine reacting to lizardite and brucite, i.e. 2 Mg2SiO4 + 3 H2O - Mg3[Si2O5](OH)4 + Mg(OH)2, implying a total volume increase of approximately 20%. However, if Mg was lost from the system, the reaction can also be written as 2 Mg2SiO4 + 2 H+ + H2O - Mg3[Si2O5](OH)4 + Mg2+. This suggests that the solid volume is preserved and no internal stresses are generated. Therefore, the presence of brucite could be used to constrain volumetric changes during serpentinization. However, the small size and sparse distribution of brucite makes it difficult to find in serpentinized metaperidotites. Here we show that micro-Raman spectroscopy is a reliable tool to identify even nanometer-sized brucite in serpentine. In addition, we also used the electron backscatter diffraction (EBSD) technique to identify volume increase illustrated by the progressive change of olivine orientation at the tip of a crack induced by serpentinization. Furthermore, it is important to constrain the degree of system openness and the transport of elements through the fluid phase. Observations from fractures in metapyroxenite layers from the Røragen-Feragen ultramafic complex provide closer insight into the late stage alteration of the oceanic lithosphere. Detailed electron microscopy reveals that these fractures are filled with polyhedral serpentine, indicating late stage open system conditions (Andreani et al., 2007). However, microtextures and reactive transport modeling suggest that Ca from clinopyroxene dissolution in the metapyroxenite layers was instantaneously precipitated as andradite within the fracture, without major Ca transport. Hence, although the overall system can be regarded as open for water, Ca exhibits closed system behavior on the decimeter scale within the metapyroxenite layers. Our observations show that mineralogical and microtextural markers, such as characteristic phases, their spatial relationship and stress generation associated with replacement, provide an insight into the metasomatic conditions of oceanic lithosphere alteration. References: Andreani et al. (2007), Geochem. Geophys. Geosyst., 8 (2). Shervais et al. (2005), Int. Geol. Rev., 47, 1-23. Viti et al. (2005) Min. Mag., 69 (2), 491-507.

Plastic debris in the open ocean

PubMed Central

Cózar, Andrés; Echevarría, Fidel; González-Gordillo, J. Ignacio; Irigoien, Xabier; Úbeda, Bárbara; Hernández-León, Santiago; Palma, Álvaro T.; Navarro, Sandra; García-de-Lomas, Juan; Ruiz, Andrea; Fernández-de-Puelles, María L.; Duarte, Carlos M.

2014-01-01

There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean. PMID:24982135

Plastic debris in the open ocean.

PubMed

Cózar, Andrés; Echevarría, Fidel; González-Gordillo, J Ignacio; Irigoien, Xabier; Ubeda, Bárbara; Hernández-León, Santiago; Palma, Alvaro T; Navarro, Sandra; García-de-Lomas, Juan; Ruiz, Andrea; Fernández-de-Puelles, María L; Duarte, Carlos M

2014-07-15

There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean.

Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

USGS Publications Warehouse

Safak, Ilgar; Warner, John C.; List, Jeffrey

2016-01-01

Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

Effects of open-air temperature on air temperature inside biological safety cabinet.

PubMed

Umemura, Masayuki; Shigeno, Katsuro; Yamamura, Keiko; Osada, Takashi; Soda, Midori; Yamada, Kiyofumi; Ando, Yuichi; Wakiya, Yoshifumi

2011-02-14

In Japan, biological safety cabinets (BSCs) are normally used by medical staff while handling antineoplastic agents. We have also set up a class II B2 BSC at the Division of Chemotherapy for Outpatients. The air temperature inside this BSC, however, decreases in winter. We assumed that this decrease is caused by the intake of open-air. Therefore, we investigated the effects of low open-air temperature on the BSC temperature and the time of admixtures of antineoplastic agents. The studies were conducted from January 1 to March 31, 2008. The outdoor air temperature was measured in the shade near the intake nozzle of the BSC and was compared with the BSC temperature. The correlation between the outdoor air temperature and the BSC temperature, the dissolution time of cyclophosphamide (CPA) and gemcitabine (GEM), and accurate weight measurement of epirubicin (EPI) solution were investigated for low and normal BSC temperatures. The BSC temperature was correlated with the open-air temperature for open-air temperatures of 5-20°C (p < 0.0001). The dissolution of CPA and GEM at these temperatures was significantly delayed as compared to that at 25°C (p < 0.01 and p < 0.0001, respectively). The weight measurement of EPI solution using a syringe method lacks accuracy because of its high coefficient of viscosity at low temperatures (p < 0.01). These results suggest that the BSC temperature decreases below room temperature in winter when air is drawn from outdoors. We showed that the BSC temperature affects the dissolution rate of antineoplastic agents. Further, we suggested that the BSC temperature drop might delay the affair of the admixtures of antineoplastic agents and increase the waiting time of outpatients for chemotherapy.

Cidaroids spines facing ocean acidification.

PubMed

Dery, Aurélie; Tran, Phuong Dat; Compère, Philippe; Dubois, Philippe

2018-07-01

When facing seawater undersaturated towards calcium carbonates, spines of classical sea urchins (euechinoids) show traces of corrosion although they are covered by an epidermis. Cidaroids (a sister clade of euechinoids) are provided with mature spines devoid of epidermis, which makes them, at first sight, more sensitive to dissolution when facing undersaturated seawater. A recent study showed that spines of a tropical cidaroid are resistant to dissolution due to the high density and the low magnesium concentration of the peculiar external spine layer, the cortex. The biofilm and epibionts covering the spines was also suggested to take part in the spine protection. Here, we investigate the protective role of these factors in different cidaroid species from a broad range of latitude, temperature and depth. The high density of the cortical layer and the cover of biofilm and epibionts were confirmed as key protection against dissolution. The low magnesium concentration of cidaroid spines compared to that of euechinoid ones makes them less soluble in general. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dissolution of solid lipid extrudates in biorelevant media.

PubMed

Witzleb, R; Müllertz, A; Kanikanti, V-R; Hamann, H-J; Kleinebudde, P

2012-01-17

Solid lipid extrudates with the model drug praziquantel were produced with chemically diverse lipids and investigated regarding their dissolution behaviour in different media. The lipids used in this study were glyceryl tripalmitate, glyceryl dibehenate, glyceryl monostearate, cetyl palmitate and solid paraffin. Thermoanalytical and dissolution behaviour was investigated directly after extrusion and after 3 and 6 months open storage at 40°C/75% RH. Dissolution studies were conducted in hydrochloric acid (HCl) pH 1.2 with different levels of polysorbate 20 and with a biorelevant medium containing pancreatic lipase, bile salts and phospholipids. Furthermore, the impact of lipid digestion on drug release was studied using in vitro lipolysis. The release of praziquantel from cetyl palmitate and glyceryl monostearate in the biorelevant medium was much faster than in HCl, whereas there was hardly any difference for the other lipids. It was shown that drug release from glyceryl monostearate matrices is driven by both solubilisation and enzymatic degradation of the lipid, whereas dissolution from cetyl palmitate extrudates is dependent only on solubilisation by surfactants in the medium. Moreover, storage influenced the appearance of the extrudate surface and the dissolution rate for all lipids except solid paraffin. Copyright © 2011 Elsevier B.V. All rights reserved.

Development of a Suitable Dissolution Method for the Combined Tablet Formulation of Atorvastatin and Ezetimibe by RP-LC Method.

PubMed

Ozkan Cansel, Kose; Ozgur, Esim; Sevinc, Kurbanoglu; Ayhan, Savaser; Ozkan, Sibel A; Yalcin, Ozkan

2016-01-01

Pharmaceutical preparations of ezetimibe and atorvastatin are generally used to regulate the lipid level in blood. It decreases the secondary events for patients with high cholesterol and clinical cardiovascular disease such as non-fatal or fatal heart attack. There is no any pharmacopoeia method available for the dissolution testing recommended by the FDA. Development of dissolution tests method is very critical parameter especially for the pharmaceutical preparations that contain Class II drugs (slightly soluble, good permeable). In the proposed method, the effects of pH and surfactant on the dissolution of poorly water soluble combined drug therapy with a different pKa values in an in vitro environment is investigated. The content of our study was designed to answer these open-ended questions. The optimized test conditions achieved under sink conditions with USP apparatus 2 at a paddle rotation speed of 75 rpm and 900 ml in 0.01 M Acetate buffer (pH= 6.8) containing 0.45% SDS as a dissolution medium. Quantification of dissolution samples were analyzed with a new fully validated RP-LC method with UV detection at 242 nm.

Climate change and ocean acidification effects on seagrasses and marine macroalgae.

PubMed

Koch, Marguerite; Bowes, George; Ross, Cliff; Zhang, Xing-Hai

2013-01-01

Although seagrasses and marine macroalgae (macro-autotrophs) play critical ecological roles in reef, lagoon, coastal and open-water ecosystems, their response to ocean acidification (OA) and climate change is not well understood. In this review, we examine marine macro-autotroph biochemistry and physiology relevant to their response to elevated dissolved inorganic carbon [DIC], carbon dioxide [CO2 ], and lower carbonate [CO3 (2-) ] and pH. We also explore the effects of increasing temperature under climate change and the interactions of elevated temperature and [CO2 ]. Finally, recommendations are made for future research based on this synthesis. A literature review of >100 species revealed that marine macro-autotroph photosynthesis is overwhelmingly C3 (≥ 85%) with most species capable of utilizing HCO3 (-) ; however, most are not saturated at current ocean [DIC]. These results, and the presence of CO2 -only users, lead us to conclude that photosynthetic and growth rates of marine macro-autotrophs are likely to increase under elevated [CO2 ] similar to terrestrial C3 species. In the tropics, many species live close to their thermal limits and will have to up-regulate stress-response systems to tolerate sublethal temperature exposures with climate change, whereas elevated [CO2 ] effects on thermal acclimation are unknown. Fundamental linkages between elevated [CO2 ] and temperature on photorespiration, enzyme systems, carbohydrate production, and calcification dictate the need to consider these two parameters simultaneously. Relevant to calcifiers, elevated [CO2 ] lowers net calcification and this effect is amplified by high temperature. Although the mechanisms are not clear, OA likely disrupts diffusion and transport systems of H(+) and DIC. These fluxes control micro-environments that promote calcification over dissolution and may be more important than CaCO3 mineralogy in predicting macroalgal responses to OA. Calcareous macroalgae are highly vulnerable to OA, and it is likely that fleshy macroalgae will dominate in a higher CO2 ocean; therefore, it is critical to elucidate the research gaps identified in this review. © 2012 Blackwell Publishing Ltd.

The Great Chilean Tsunamis of 2010, 2014 and 2015 on the Coast and Offshore of Mexico: Comparative Features Based on Open-Ocean Energy Parameterization

NASA Astrophysics Data System (ADS)

Rabinovich, A.; Zaytsev, O.; Thomson, R.

2016-12-01

The three recent great earthquakes offshore of Chile on 27 February 2010 (Maule, Mw 8.8), 1 April 2014 (Iquique, Mw 8.2) and 16 September 2015 (Illapel, Mw 8.3) generated major trans-oceanic tsunamis that spread throughout the entire Pacific Ocean and were measured by numerous coastal tide gauges and open-ocean DART stations. Statistical and spectral analyses of the tsunami waves from the three events recorded on the Pacific coast of Mexico enabled us to compare the events and to identify coastal "hot spots", regions with maximum tsunami risk. Based on joint spectral analyses of tsunamis and background noise, we have developed a method for reconstructing the "true" tsunami spectra in the deep ocean. The "reconstructed" open-ocean tsunami spectra are in excellent agreement with the actual tsunami spectra evaluated from direct analysis of the DART records offshore of Mexico. We have further used the spectral estimates to parameterize the energy of the three Chilean tsunamis based on the total open-ocean tsunami energy and frequency content of the individual events.

Variations of the Organic Matter Composition in the Sea Surface Microlayer: A Comparison between Open Ocean, Coastal, and Upwelling Sites Off the Peruvian Coast

PubMed Central

Zäncker, Birthe; Bracher, Astrid; Röttgers, Rüdiger; Engel, Anja

2017-01-01

The sea surface microlayer (SML) is the thin boundary layer between the ocean and the atmosphere, making it important for air-sea exchange processes. However, little is known about what controls organic matter composition in the SML. In particular, there are only few studies available on the differences of the SML of various oceanic systems. Here, we compared the organic matter and neuston species composition in the SML and the underlying water (ULW) at 11 stations with varying distance from the coast in the Peruvian upwelling regime, a system with high emissions of climate relevant trace gases, such as N2O and CO2. In the open ocean, organic carbon, and amino acids were highly enriched in the SML compared to the ULW. The enrichment decreased at the coastal stations and vanished in the upwelling regime. At the same time, the degradation of organic matter increased from the open ocean to the upwelling stations. This suggests that in the open ocean, upward transport processes or new production of organic matter within the SML are faster than degradation processes. Phytoplankton was generally not enriched in the SML, one group though, the Trichodesmium-like TrL (possibly containing Trichodesmium), were enriched in the open ocean but not in the upwelling region indicating that they find a favorable habitat in the open ocean SML. Our data show that the SML is a distinct habitat; its composition is more similar among different systems than between SML and ULW of a single station. Generally the enrichment of organic matter is assumed to be reduced when encountering low primary production and high wind speeds. However, our study shows the highest enrichments of organic matter in the open ocean which had the lowest primary production and the highest wind speeds. PMID:29375483

Variations of the Organic Matter Composition in the Sea Surface Microlayer: A Comparison between Open Ocean, Coastal, and Upwelling Sites Off the Peruvian Coast.

PubMed

Zäncker, Birthe; Bracher, Astrid; Röttgers, Rüdiger; Engel, Anja

2017-01-01

The sea surface microlayer (SML) is the thin boundary layer between the ocean and the atmosphere, making it important for air-sea exchange processes. However, little is known about what controls organic matter composition in the SML. In particular, there are only few studies available on the differences of the SML of various oceanic systems. Here, we compared the organic matter and neuston species composition in the SML and the underlying water (ULW) at 11 stations with varying distance from the coast in the Peruvian upwelling regime, a system with high emissions of climate relevant trace gases, such as N 2 O and CO 2 . In the open ocean, organic carbon, and amino acids were highly enriched in the SML compared to the ULW. The enrichment decreased at the coastal stations and vanished in the upwelling regime. At the same time, the degradation of organic matter increased from the open ocean to the upwelling stations. This suggests that in the open ocean, upward transport processes or new production of organic matter within the SML are faster than degradation processes. Phytoplankton was generally not enriched in the SML, one group though, the Trichodesmium -like TrL (possibly containing Trichodesmium ), were enriched in the open ocean but not in the upwelling region indicating that they find a favorable habitat in the open ocean SML. Our data show that the SML is a distinct habitat; its composition is more similar among different systems than between SML and ULW of a single station. Generally the enrichment of organic matter is assumed to be reduced when encountering low primary production and high wind speeds. However, our study shows the highest enrichments of organic matter in the open ocean which had the lowest primary production and the highest wind speeds.

The Impact of Ocean Acidification on the Functional Morphology of Foraminifera

PubMed Central

Khanna, Nikki; Godbold, Jasmin A.; Austin, William E. N.; Paterson, David M.

2013-01-01

Culturing experiments were performed on sediment samples from the Ythan Estuary, N. E. Scotland, to assess the impacts of ocean acidification on test surface ornamentation in the benthic foraminifer Haynesina germanica. Specimens were cultured for 36 weeks at either 380, 750 or 1000 ppm atmospheric CO2. Analysis of the test surface using SEM imaging reveals sensitivity of functionally important ornamentation associated with feeding to changing seawater CO2 levels. Specimens incubated at high CO2 levels displayed evidence of shell dissolution, a significant reduction and deformation of ornamentation. It is clear that these calcifying organisms are likely to be vulnerable to ocean acidification. A reduction in functionally important ornamentation could lead to a reduction in feeding efficiency with consequent impacts on this organism's survival and fitness. PMID:24358253

Environmental Assessment for Potential Impacts of Ocean CO2 Storage on Marine Biogeochemical Cycles

NASA Astrophysics Data System (ADS)

Yamada, N.; Tsurushima, N.; Suzumura, M.; Shibamoto, Y.; Harada, K.

2008-12-01

Ocean CO2 storage that actively utilizes the ocean potential to dissolve extremely large amounts of CO2 is a useful option with the intent of diminishing atmospheric CO2 concentration. CO2 storage into sub-seabed geological formations is also considered as the option which has been already put to practical reconnaissance in some projects. Direct release of CO2 in the ocean storage and potential CO2 leakage from geological formations into the bottom water can alter carbonate system as well as pH of seawater. It is essential to examine to what direction and extent chemistry change of seawater induced by CO2 can affect the marine environments. Previous studies have shown direct and acute effects by increasing CO2 concentrations on physiology of marine organisms. It is also a serious concern that chemistry change can affect the rates of chemical, biochemical and microbial processes in seawater resulting in significant influences on marine biogeochemical cycles of the bioelements including carbon, nutrients and trace metals. We, AIST, have conducted a series of basic researches to assess the potential impacts of ocean CO2 storage on marine biogeochemical processes including CaCO3 dissolution, and bacterial and enzymatic decomposition of organic matter. By laboratory experiments using a special high pressure apparatus, the improved empirical equation was obtained for CaCO3 dissolution rate in the high CO2 concentrations. Based on the experimentally obtained kinetics with a numerical simulation for a practical scenario of oceanic CO2 sequestration where 50 Mton CO2 per year is continuously injected to 1,000-2,500 m depth within 100 x 333 km area for 30 years, we could illustrate precise 3-D maps for the predicted distributions of the saturation depth of CaCO3, in situ Ω value and CaCO3 dissolution rate in the western North Pacific. The result showed no significant change in the bathypelagic CaCO3 flux due to chemistry change induced by ocean CO2 sequestration. Both bacteria and hydrolytic enzymes are known as the essential promoters for organic matter decomposition in marine ecosystems. Bacterial activity and metabolisms under various CO2 concentrations and pH were examined on total cell abundance, 3H-leucine incorporation rate, and viable cell abundance. Our in vitro experiments demonstrated that acute effect by high CO2 conditions was negligible on the activities of bathypelagic bacteria at pH 7 or higher. However, our results suggested that bacterial assemblage in some organic-rich "microbial hot-spots" in seawater such as organic aggregates sinking particles, exhibited high sensitivity to acidification. Furthermore, it was indicated that CO2 injection seems to be the trigger to alter the microbial community structure between Eubacteria and Archaea. The activities of five types of hydrolytic enzymes showed no significant change with acidification as those observed in the bacterial activity. As to acute effects on microbial and biochemical processes examined by our laboratory studies, no significant influence was exhibited in the simulated ocean CO2 storage on marine biogeochemical cycling. Uncertainties in chronic and large-scale impacts, however, remain and should be addressed for more understanding the potential benefits and risks of the ocean storage.

Towards the impact of eddies on the response of the global ocean circulation to Southern Ocean gateway opening

NASA Astrophysics Data System (ADS)

Viebahn, Jan; von der Heydt, Anna S.; Dijkstra, Henk A.

2014-05-01

During the past 65 Million (Ma) years, Earth's climate has undergone a major change from warm 'greenhouse' to colder 'icehouse' conditions with extensive ice sheets in the polar regions of both hemispheres. The Eocene-Oligocene (~34 Ma) and Oligocene-Miocene (~23 Ma) boundaries reflect major transitions in Cenozoic global climate change. Proposed mechanisms of these transitions include reorganization of ocean circulation due to critical gateway opening/deepening, changes in atmospheric CO2-concentration, and feedback mechanisms related to land-ice formation. A long-standing hypothesis is that the formation of the Antarctic Circumpolar Current due to opening/deepening of Southern Ocean gateways led to glaciation of the Antarctic continent. However, while this hypothesis remains controversial, its assessment via coupled climate model simulations depends crucially on the spatial resolution in the ocean component. More precisely, only high-resolution modeling of the turbulent ocean circulation is capable of adequately describing reorganizations in the ocean flow field and related changes in turbulent heat transport. In this study, for the first time results of a high-resolution (0.1° horizontally) realistic global ocean model simulation with a closed Drake Passage are presented. Changes in global ocean temperatures, heat transport, and ocean circulation (e.g., Meridional Overturning Circulation and Antarctic Coastal Current) are established by comparison with an open Drake Passage high-resolution reference simulation. Finally, corresponding low-resolution simulations are also analyzed. The results highlight the essential impact of the ocean eddy field in palaeoclimatic change.

A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

NASA Astrophysics Data System (ADS)

Han, Mei; Zhao, Yanyang; Zhao, Hui; Han, Zuozhen; Yan, Huaxiao; Sun, Bin; Meng, Ruirui; Zhuang, Dingxiang; Li, Dan; Liu, Binwei

2018-04-01

Based on the terminology of "aragonite seas" and "calcite seas", whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

Fracture Dissolution of Carbonate Rock: An Innovative Process for Gas Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

James W. Castle; Ronald W. Falta; David Bruce

2006-10-31

The goal of the project is to develop and assess the feasibility and economic viability of an innovative concept that may lead to commercialization of new gas-storage capacity near major markets. The investigation involves a new approach to developing underground gas storage in carbonate rock, which is present near major markets in many areas of the United States. Because of the lack of conventional gas storage and the projected growth in demand for storage capacity, many of these areas are likely to experience shortfalls in gas deliverability. Since depleted gas reservoirs and salt formations are nearly non-existent in many areas,more » alternatives to conventional methods of gas storage are required. The need for improved methods of gas storage, particularly for ways to meet peak demand, is increasing. Gas-market conditions are driving the need for higher deliverability and more flexibility in injection/withdrawal cycling. In order to meet these needs, the project involves an innovative approach to developing underground storage capacity by creating caverns in carbonate rock formations by acid dissolution. The basic concept of the acid-dissolution method is to drill to depth, fracture the carbonate rock layer as needed, and then create a cavern using an aqueous acid to dissolve the carbonate rock. Assessing feasibility of the acid-dissolution method included a regional geologic investigation. Data were compiled and analyzed from carbonate formations in six states: Indiana, Ohio, Kentucky, West Virginia, Pennsylvania, and New York. To analyze the requirements for creating storage volume, the following aspects of the dissolution process were examined: weight and volume of rock to be dissolved; gas storage pressure, temperature, and volume at depth; rock solubility; and acid costs. Hydrochloric acid was determined to be the best acid to use because of low cost, high acid solubility, fast reaction rates with carbonate rock, and highly soluble products (calcium chloride) that allow for the easy removal of calcium waste from the well. Physical and chemical analysis of core samples taken from prospective geologic formations for the acid dissolution process confirmed that many of the limestone samples readily dissolved in concentrated hydrochloric acid. Further, some samples contained oily residues that may help to seal the walls of the final cavern structure. These results suggest that there exist carbonate rock formations well suited for the dissolution technology and that the presence of inert impurities had no noticeable effect on the dissolution rate for the carbonate rock. A sensitivity analysis was performed for characteristics of hydraulic fractures induced in carbonate formations to enhance the dissolution process. Multiple fracture simulations were conducted using modeling software that has a fully 3-D fracture geometry package. The simulations, which predict the distribution of fracture geometry and fracture conductivity, show that the stress difference between adjacent beds is the physical property of the formations that has the greatest influence on fracture characteristics by restricting vertical growth. The results indicate that by modifying the fracturing fluid, proppant type, or pumping rate, a fracture can be created with characteristics within a predictable range, which contributes to predicting the geometry of storage caverns created by acid dissolution of carbonate formations. A series of three-dimensional simulations of cavern formation were used to investigate three different configurations of the acid-dissolution process: (a) injection into an open borehole with production from that same borehole and no fracture; (b) injection into an open borehole with production from that same borehole, with an open fracture; and (c) injection into an open borehole connected by a fracture to an adjacent borehole from which the fluids are produced. The two-well configuration maximizes the overall mass transfer from the rock to the fluid, but it results in a complex cavern shape. Numerical simulations were performed to evaluate the ability of storage caverns produced by the acid-dissolution method to store natural gas. In addition, analyses were conducted to evaluate cavern stability during gas injection and withdrawal from storage caverns created in carbonate formations by the acid-dissolution method. The stability analyses were conducted using FLAC2D, a commercially available geotechnical analysis and design software. The analyses indicate that a tall cylindrical cavern with a domed roof and floor will be stable under the expected range of in situ and operational conditions. This result suggests that it should be feasible to avoid mechanical instabilities that could potentially diminish the effectiveness of the storage facility. The feasibility of using pressure transients measured at the ground surface was investigated as a means to evaluate (Abstract truncated)« less

Eighty-five million years of Pacific Ocean gyre ecosystem structure: long-term stability marked by punctuated change.

PubMed

Sibert, Elizabeth; Norris, Richard; Cuevas, Jose; Graves, Lana

2016-05-25

While the history of taxonomic diversification in open ocean lineages of ray-finned fish and elasmobranchs is increasingly known, the evolution of their roles within the open ocean ecosystem remains poorly understood. To assess the relative importance of these groups through time, we measured the accumulation rate of microfossil fish teeth and elasmobranch dermal denticles (ichthyoliths) in deep-sea sediment cores from the North and South Pacific gyres over the past 85 million years (Myr). We find three distinct and stable open ocean ecosystem structures, each defined by the relative and absolute abundance of elasmobranch and ray-finned fish remains. The Cretaceous Ocean (pre-66 Ma) was characterized by abundant elasmobranch denticles, but low abundances of fish teeth. The Palaeogene Ocean (66-20 Ma), initiated by the Cretaceous/Palaeogene mass extinction, had nearly four times the abundance of fish teeth compared with elasmobranch denticles. This Palaeogene Ocean structure remained stable during the Eocene greenhouse (50 Ma) and the Eocene-Oligocene glaciation (34 Ma), despite large changes in the overall accumulation of both groups during those intervals, suggesting that climate change is not a primary driver of ecosystem structure. Dermal denticles virtually disappeared from open ocean ichthyolith assemblages approximately 20 Ma, while fish tooth accumulation increased dramatically in variability, marking the beginning of the Modern Ocean. Together, these results suggest that open ocean fish community structure is stable on long timescales, independent of total production and climate change. The timing of the abrupt transitions between these states suggests that the transitions may be due to interactions with other, non-preserved pelagic consumer groups. © 2016 The Author(s).

Eighty-five million years of Pacific Ocean gyre ecosystem structure: long-term stability marked by punctuated change

PubMed Central

Norris, Richard; Cuevas, Jose; Graves, Lana

2016-01-01

While the history of taxonomic diversification in open ocean lineages of ray-finned fish and elasmobranchs is increasingly known, the evolution of their roles within the open ocean ecosystem remains poorly understood. To assess the relative importance of these groups through time, we measured the accumulation rate of microfossil fish teeth and elasmobranch dermal denticles (ichthyoliths) in deep-sea sediment cores from the North and South Pacific gyres over the past 85 million years (Myr). We find three distinct and stable open ocean ecosystem structures, each defined by the relative and absolute abundance of elasmobranch and ray-finned fish remains. The Cretaceous Ocean (pre-66 Ma) was characterized by abundant elasmobranch denticles, but low abundances of fish teeth. The Palaeogene Ocean (66–20 Ma), initiated by the Cretaceous/Palaeogene mass extinction, had nearly four times the abundance of fish teeth compared with elasmobranch denticles. This Palaeogene Ocean structure remained stable during the Eocene greenhouse (50 Ma) and the Eocene–Oligocene glaciation (34 Ma), despite large changes in the overall accumulation of both groups during those intervals, suggesting that climate change is not a primary driver of ecosystem structure. Dermal denticles virtually disappeared from open ocean ichthyolith assemblages approximately 20 Ma, while fish tooth accumulation increased dramatically in variability, marking the beginning of the Modern Ocean. Together, these results suggest that open ocean fish community structure is stable on long timescales, independent of total production and climate change. The timing of the abrupt transitions between these states suggests that the transitions may be due to interactions with other, non-preserved pelagic consumer groups. PMID:27194702

Investigating the effect of moisture protection on solid-state stability and dissolution of fenofibrate and ketoconazole solid dispersions using PXRD, HSDSC and Raman microscopy.

PubMed

Kanaujia, Parijat; Lau, Grace; Ng, Wai Kiong; Widjaja, Effendi; Schreyer, Martin; Hanefeld, Andrea; Fischbach, Matthias; Saal, Christoph; Maio, Mario; Tan, Reginald B H

2011-09-01

Enhanced dissolution of poorly soluble active pharmaceutical ingredients (APIs) in amorphous solid dispersions often diminishes during storage due to moisture-induced re-crystallization. This study aims to investigate the influence of moisture protection on solid-state stability and dissolution profiles of melt-extruded fenofibrate (FF) and ketoconazole (KC) solid dispersions. Samples were kept in open, closed and Activ-vials(®) to control the moisture uptake under accelerated conditions. During 13-week storage, changes in API crystallinity were quantified using powder X-ray diffraction (PXRD) (Rietveld analysis) and high sensitivity differential scanning calorimetry (HSDSC) and compared with any change in dissolution profiles. Trace crystallinity was observed by Raman microscopy, which otherwise was undetected by PXRD and HSDSC. Results showed that while moisture protection was ineffective in preventing the re-crystallization of amorphous FF, KC remained X-ray amorphous despite 5% moisture uptake. Regardless of the degree of crystallinity increase in FF, the enhanced dissolution properties were similarly diminished. Moisture uptake above 10% in KC samples also led to re-crystallization and significant decrease in dissolution rates. In conclusion, eliminating moisture sorption may not be sufficient in ensuring the stability of solid dispersions. Analytical quantification of API crystallinity is crucial in detecting subtle increase in crystallinity that can diminish the enhanced dissolution properties of solid dispersions.

Method and apparatus for efficient injection of CO2 in oceans

DOEpatents

West, Olivia R.; Tsouris, Constantinos; Liang, Liyuan

2003-07-29

A liquid CO.sub.2 injection system produces a negatively buoyant consolidated stream of liquid CO.sub.2, CO.sub.2 hydrate, and water that sinks upon release at ocean depths in the range of 700-1500 m. In this approach, seawater at a predetermined ocean depth is mixed with the liquid CO.sub.2 stream before release into the ocean. Because mixing is conducted at depths where pressures and temperatures are suitable for CO.sub.2 hydrate formation, the consolidated stream issuing from the injector is negatively buoyant, and comprises mixed CO.sub.2 -hydrate/CO.sub.2 -liquid/water phases. The "sinking" characteristic of the produced stream will prolong the metastability of CO.sub.2 ocean sequestration by reducing the CO.sub.2 dissolution rate into water. Furthermore, the deeper the CO.sub.2 hydrate stream sinks after injection, the more stable it becomes internally, the deeper it is dissolved, and the more dispersed is the resulting CO.sub.2 plume. These factors increase efficiency, increase the residence time of CO2 in the ocean, and decrease the cost of CO.sub.2 sequestration while reducing deleterious impacts of free CO.sub.2 gas in ocean water.

Software framework for prognostic health monitoring of ocean-based power generation

NASA Astrophysics Data System (ADS)

Bowren, Mark

On August 5, 2010 the U.S. Department of Energy (DOE) has designated the Center for Ocean Energy Technology (COET) at Florida Atlantic University (FAU) as a national center for ocean energy research and development of prototypes for open-ocean power generation. Maintenance on ocean-based machinery can be very costly. To avoid unnecessary maintenance it is necessary to monitor the condition of each machine in order to predict problems. This kind of prognostic health monitoring (PHM) requires a condition-based maintenance (CBM) system that supports diagnostic and prognostic analysis of large amounts of data. Research in this field led to the creation of ISO13374 and the development of a standard open-architecture for machine condition monitoring. This thesis explores an implementation of such a system for ocean-based machinery using this framework and current open-standard technologies.

Estimating the Cross-Shelf Export of Riverine Materials: Part 2. Estimates of Global Freshwater and Nutrient Export

NASA Astrophysics Data System (ADS)

Izett, Jonathan G.; Fennel, Katja

2018-02-01

Rivers deliver large amounts of fresh water, nutrients, and other terrestrially derived materials to the coastal ocean. Where inputs accumulate on the shelf, harmful effects such as hypoxia and eutrophication can result. In contrast, where export to the open ocean is efficient riverine inputs contribute to global biogeochemical budgets. Assessing the fate of riverine inputs is difficult on a global scale. Global ocean models are generally too coarse to resolve the relatively small scale features of river plumes. High-resolution regional models have been developed for individual river plume systems, but it is impractical to apply this approach globally to all rivers. Recently, generalized parameterizations have been proposed to estimate the export of riverine fresh water to the open ocean (Izett & Fennel, 2018, https://doi.org/10.1002/2017GB005667; Sharples et al., 2017, https://doi.org/10.1002/2016GB005483). Here the relationships of Izett and Fennel, https://doi.org/10.1002/2017GB005667 are used to derive global estimates of open-ocean export of fresh water and dissolved inorganic silicate, dissolved organic carbon, and dissolved organic and inorganic phosphorus and nitrogen. We estimate that only 15-53% of riverine fresh water reaches the open ocean directly in river plumes; nutrient export is even less efficient because of processing on continental shelves. Due to geographic differences in riverine nutrient delivery, dissolved silicate is the most efficiently exported to the open ocean (7-56.7%), while dissolved inorganic nitrogen is the least efficiently exported (2.8-44.3%). These results are consistent with previous estimates and provide a simple way to parameterize export to the open ocean in global models.

High evolutionary potential of marine zooplankton

PubMed Central

Peijnenburg, Katja T C A; Goetze, Erica

2013-01-01

Abstract Open ocean zooplankton often have been viewed as slowly evolving species that have limited capacity to respond adaptively to changing ocean conditions. Hence, attention has focused on the ecological responses of zooplankton to current global change, including range shifts and changing phenology. Here, we argue that zooplankton also are well poised for evolutionary responses to global change. We present theoretical arguments that suggest plankton species may respond rapidly to selection on mildly beneficial mutations due to exceptionally large population size, and consider the circumstantial evidence that supports our inference that selection may be particularly important for these species. We also review all primary population genetic studies of open ocean zooplankton and show that genetic isolation can be achieved at the scale of gyre systems in open ocean habitats (100s to 1000s of km). Furthermore, population genetic structure often varies across planktonic taxa, and appears to be linked to the particular ecological requirements of the organism. In combination, these characteristics should facilitate adaptive evolution to distinct oceanographic habitats in the plankton. We conclude that marine zooplankton may be capable of rapid evolutionary as well as ecological responses to changing ocean conditions, and discuss the implications of this view. We further suggest two priority areas for future research to test our hypothesis of high evolutionary potential in open ocean zooplankton, which will require (1) assessing how pervasive selection is in driving population divergence and (2) rigorously quantifying the spatial and temporal scales of population differentiation in the open ocean. Recent attention has focused on the ecological responses of open ocean zooplankton to current global change, including range shifts and changing phenology. Here, we argue that marine zooplankton also are well poised for evolutionary responses to global change. PMID:24567838

Turbulence Scaling Comparisons in the Ocean Surface Boundary Layer

NASA Astrophysics Data System (ADS)

Esters, L.; Breivik, Ø.; Landwehr, S.; ten Doeschate, A.; Sutherland, G.; Christensen, K. H.; Bidlot, J.-R.; Ward, B.

2018-03-01

Direct observations of the dissipation rate of turbulent kinetic energy, ɛ, under open ocean conditions are limited. Consequently, our understanding of what chiefly controls dissipation in the open ocean, and its functional form with depth, is poorly constrained. In this study, we report direct open ocean measurements of ɛ from the Air-Sea Interaction Profiler (ASIP) collected during five different cruises in the Atlantic Ocean. We then combine these data with ocean-atmosphere flux measurements and wave information in order to evaluate existing turbulence scaling theories under a diverse set of open ocean conditions. Our results do not support the presence of a "breaking" or a "transition layer," which has been previously suggested. Instead, ɛ decays as |z|-1.29 over the depth interval, which was previously defined as "transition layer," and as |z|-1.15 over the mixing layer. This depth dependency does not significantly vary between nonbreaking or breaking wave conditions. A scaling relationship based on the friction velocity, the wave age, and the significant wave height describes the observations best for daytime conditions. For conditions during which convection is important, it is necessary to take buoyancy forcing into account.

Tertiary carbonate-dissolution cycles on the Sierra Leone Rise, eastern equatorial Atlantic Ocean

USGS Publications Warehouse

Dean, W.E.; Gardner, J.V.; Cepek, P.

1981-01-01

Most of the Tertiary section on Sierra Leone Rise off northwest Africa consists of chalk, marl, and limestone that show cyclic alterations of clay-rich and clay-poor beds about 20-60 cm thick. On the basis of biostratigraphic accumulation rates, the cycles in Oligocene and Miocene chalk have periods which average about 44,000 years, and those in Eocene siliceous limestone have periods of 4000-27,000 years. Several sections were sampled in detail to further define the cycles in terms of content of CaCO3, clay minerals, and relative abundances of calcareous nannofossils. Extending information gained by analyses of Pleistocene cores from the continental margin of northwest Africa to the Tertiary cycles on Sierra Leone Rise, both dilution by noncarbonate material and dissolution of CaCO3 could have contributed to the observed relative variations in clay and CaCO3. However, dissolution of CaCO3 as the main cause of the carbonate-clay cycles on the Sierra Leone Rise, rather than dilution by clay, is suggested by the large amount of change (several thousand percent) in terrigenous influx required to produce the observed variations in amount of clay and by the marked increase in abundance of dissolution-resistant discoasters relative to more easily dissolved coccoliths in low-carbonate parts of cycles. The main cause of dissolution of CaCO3 was shoaling of the carbonate compensation depth (CCD) during the early Neogene and climatically induced fluctuations in the thickness of Antarctic Bottom Water. ?? 1981.

Shelf and open-ocean calcareous phytoplankton assemblages across the Paleocene-Eocene thermal maximum: Implications for global productivity gradients

USGS Publications Warehouse

Gibbs, S.J.; Bralower, T.J.; Bown, Paul R.; Zachos, J.C.; Bybell, L.M.

2006-01-01

Abrupt global warming and profound perturbation of the carbon cycle during the Paleocene-Eocene Thermal Maximum (PETM, ca. 55 Ma) have been linked to a massive release of carbon into the ocean-atmosphere system. Increased phytoplankton productivity has been invoked to cause subsequent CO2 drawdown, cooling, and environmental recovery. However, interpretations of geochemical and biotic data differ on when and where this increased productivity occurred. Here we present high-resolution nannofossil assemblage data from a shelf section (the U.S. Geological Survey [USGS] drill hole at Wilson Lake, New Jersey) and an open-ocean location (Ocean Drilling Program [ODP] Site 1209, paleoequatorial Pacific). These data combined with published biotic records indicate a transient steepening of shelf-offshelf trophic gradients across the PETM onset and peak, with a decrease in open-ocean productivity coeval with increased nutrient availability in shelf areas. Productivity levels recovered in the open ocean during the later stages of the event, which, coupled with intensified continental weathering rates, may have played an important role in carbon sequestration and CO2 drawdown. ?? 2006 Geological Society of America.

Oceanic dispersion of Fukushima-derived Cs-137 in the coastal, offshore, and open oceans simulated by multiple oceanic general circulation models

NASA Astrophysics Data System (ADS)

Kawamura, H.; Furuno, A.; Kobayashi, T.; In, T.; Nakayama, T.; Ishikawa, Y.; Miyazawa, Y.; Usui, N.

2017-12-01

To understand the concentration and amount of Fukushima-derived Cs-137 in the ocean, this study simulates the oceanic dispersion of Cs-137 by an oceanic dispersion model SEA-GEARN-FDM developed at Japan Atomic Energy Agency (JAEA) and multiple oceanic general circulation models. The Cs-137 deposition amounts at the sea surface were used as the source term in oceanic dispersion simulations, which were estimated by atmospheric dispersion simulations with a Worldwide version of System for Prediction of Environmental Emergency Dose Information version II (WSPEEDI-II) developed at JAEA. The direct release from the Fukushima Daiichi Nuclear Power Plant into the ocean based on in situ Cs-137 measurements was used as the other source term in oceanic dispersion simulations. The simulated air Cs-137 concentrations qualitatively replicated those measured around the North Pacific. The accumulated Cs-137 ground deposition amount in the eastern Japanese Islands was consistent with that estimated by aircraft measurements. The oceanic dispersion simulations relatively well reproduced the measured Cs-137 concentrations in the coastal and offshore oceans during the first few months after the Fukushima disaster, and in the open ocean during the first year post-disaster. It was suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Mesoscale eddies accompanied by the Kuroshio Current and Kuroshio Extension played an important role in dilution of Cs-137. The Cs-137 amounts were quantified in the coastal, offshore, and open oceans during the first year post-disaster. It was demonstrated that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layer in the North Pacific.

Dissolution rates of pure methane hydrate and carbon-dioxide hydrate in undersaturated seawater at 1000-m depth

USGS Publications Warehouse

Rehder, G.; Kirby, S.H.; Durham, W.B.; Stern, L.A.; Peltzer, E.T.; Pinkston, J.; Brewer, P.G.

2004-01-01

To help constrain models involving the chemical stability and lifetime of gas clathrate hydrates exposed at the seafloor, dissolution rates of pure methane and carbon-dioxide hydrates were measured directly on the seafloor within the nominal pressure-temperature (P/T) range of the gas hydrate stability zone. Other natural boundary conditions included variable flow velocity and undersaturation of seawater with respect to the hydrate-forming species. Four cylindrical test specimens of pure, polycrystalline CH4 and CO2 hydrate were grown and fully compacted in the laboratory, then transferred by pressure vessel to the seafloor (1028 m depth), exposed to the deep ocean environment, and monitored for 27 hours using time-lapse and HDTV cameras. Video analysis showed diameter reductions at rates between 0.94 and 1.20 ??m/s and between 9.0 and 10.6 ?? 10-2 ??m/s for the CO2 and CH4 hydrates, respectively, corresponding to dissolution rates of 4.15 ?? 0.5 mmol CO2/m2s and 0.37 ?? 0.03 mmol CH4/m2s. The ratio of the dissolution rates fits a diffusive boundary layer model that incorporates relative gas solubilities appropriate to the field site, which implies that the kinetics of the dissolution of both hydrates is diffusion-controlled. The observed dissolution of several mm (CH4) or tens of mm (CO2) of hydrate from the sample surfaces per day has major implications for estimating the longevity of natural gas hydrate outcrops as well as for the possible roles of CO2 hydrates in marine carbon sequestration strategies. ?? 2003 Elsevier Ltd.

Antisolvent crystallization of a cardiotonic drug in ionic liquids: Effect of mixing on the crystal properties

NASA Astrophysics Data System (ADS)

de Azevedo Jacqueline, Resende; Fabienne, Espitalier; Jean-Jacques, Letourneau; Inês, Ré Maria

2017-08-01

LASSBio-294 (3,4-methylenedioxybenzoyl-2-thienylhydrazon) is a poorly soluble drug which has been proposed to have major advantages over other cardiotonic drugs. Poorly water soluble drugs present limited bioavailability due to their low solubility and dissolution rate. An antisolvent crystallization processing can improve the dissolution rate by decreasing the crystals particle size. However, LASSBio-294 is also poorly soluble in organic solvents and this operation is limited. In order to open new perspectives to improve dissolution rate, this work has investigated LASSBio-294 in terms of its antisolvent crystallization in 1-ethyl-3-methylimidazolium methyl phosphonate [emim][CH3O(H)PO2] as solvent and water as antisolvent. Two modes of mixing are tested in stirred vessel with different pre-mixers (Roughton or T-mixers) in order to investigate the mixing effect on the crystal properties (crystalline structure, particle size distribution, residual solvent and in vitro dissolution rate). Smaller drug particles with unchanged crystalline structure were obtained. Despite the decrease of the elementary particles size, the recrystallized particles did not achieve a better dissolution profile. However, this study was able to highlight a certain number of findings such as the impact of the hydrodynamic conditions on the crystals formation and the presence of a gel phase limiting the dissolution rate.

Lubricant-Induced Crystallization of Itraconazole From Tablets Made of Electrospun Amorphous Solid Dispersion.

PubMed

Démuth, Balázs; Farkas, Attila; Balogh, Attila; Bartosiewicz, Karolina; Kállai-Szabó, Barnabás; Bertels, Johny; Vigh, Tamás; Mensch, Jurgen; Verreck, Geert; Van Assche, Ivo; Marosi, György; Nagy, Zsombor K

2016-09-01

Investigation of downstream processing of nanofibrous amorphous solid dispersions to generate tablet formulation is in a quite early phase. Development of high speed electrospinning opened up the possibility to study tableting of electrospun solid dispersions (containing polyvinylpyrrolidone-vinyl acetate and itraconazole [ITR] in this case). This work was conducted to investigate the influence of excipients on dissolution properties and the feasibility of scaled-up rotary press tableting. The dissolution rates from tablets proved to be mainly composition dependent. Magnesium stearate acted as a nucleation promoting agent (providing an active hydrophobic environment for crystallization of ITR) hindering the total dissolution of ITR. This crystallization process proved to be temperature dependent as well. However, the extent of dissolution of more than 95% was realizable when a less hydrophobic lubricant, sodium stearyl fumarate (soluble in the medium), was applied. Magnesium stearate induced crystallization even if it was put in the dissolution medium next to proper tablets. After optimization of the composition, scaled-up tableting on a rotary press was carried out. Appropriate dissolution of ITR from tablets was maintained for 3 months at 25°C/60% relative humidity. HPLC measurements confirmed that ITR was chemically stable both in the course of downstream processing and storage. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

The Neogene equatorial Pacific: A view from 2009 IODP drilling on Expedition 320/321. (Invited)

NASA Astrophysics Data System (ADS)

Lyle, M. W.; Shackford, J.; Holbourn, A. E.; Tian, J.; Raffi, I.; Pälike, H.; Nishi, H.

2013-12-01

The equatorial Pacific responds strongly to global climate and is a source of ENSO, the largest global decadal climate oscillation. Equatorial Pacific circulation and upwelling result from global atmospheric circulation patterns so it is unsurprising that oceanographic changes in the equatorial Pacific reverberate globally. IODP expedition 320/321 (Pacific Equatorial Age Transect) drilled 8 sites to reconstruct a 50-million-year record of ocean change for the equatorial Pacific. The resulting record, when spliced together, will resolve orbital variations through most of the Cenozoic. All sedimentary sequences have now been scanned by XRF, so that biogeochemical changes through the Cenozoic can be studied. Here we report data from IODP Sites U1335, U1336, U1337, and U1338, the Neogene part of the PEAT megasplice. Sediments of the Neogene equatorial Pacific are primarily biogenic carbonates, with about 15% biogenic silica tests and 5% assorted other components, including clays. Typically, highest sediment deposition occurs when plate tectonic movement carries a drill site underneath the equatorial zone, indicating that equatorial upwelling and high productivity have been consistent features of the Neogene equatorial Pacific. Sedimentation rates become significantly slower and dissolution of both biogenic carbonates and silica are more pronounced when sites are beyond 3° in latitude away from the equator, as biogenic sediment production drops but dissolution does not. The differences between equatorial and off-equator sites allow assessment of productivity vs dissolution as drivers of the sediment record. Carbonate dissolution can also be assessed by a ratio of XRF-estimated carbonate to dissolution resistant biogenic residue, like barite. There is a common stratigraphy of carbonate variation in the Neogene equatorial Pacific, as proposed by earlier work from DSDP Leg 85 and ODP Leg 138. The new Exp 320/321 drilling extends the high-resolution record from ~0-5 Ma covered by Leg 138 studies to the full Neogene. Productivity events, like those in the late Miocene biogenic bloom interval (~5-7 Ma), are marked by carbonate percent lows at sites near the equator where diatom production outstrips increased production by carbonate producers. Away from the equator, there is little sign of the events in the percentage data because carbonate production increases in step with biogenic silica production at lower productivity increases. The middle-late Miocene carbonate crash interval (12-8 Ma) is marked by enhanced deposition of mat-forming diatioms, but highest deposition of bio-SiO2 is at the convergence of equatorial currents at 2°N, not at the equator. It is still unclear to what extent productivity shapes the events versus dissolution. Other productivity events can now be associated with middle Miocene Mi3-Mi4 glaciations. Dissolution events are also found, like the early Miocene ';lavender' event at 17 Ma. Surprisingly, peak dissolution is not associated with the peak warmth of the Miocene climatic optimum, but with an abrupt early warming that predates the warm interval. The dissolution event also predates possible volatile release from Columbia River flood basalts, indicating that complex changes in circulation and ocean carbon content must have occurred then. Understanding the timing will ultimately help to decipher the role of the carbon cycle in climate change.

Sensitivity of Calibration Gains to Ocean Color Processing in Coastal and Open Waters Using Ensembles Members for NPP-VIIRS

DTIC Science & Technology

2014-07-01

a different impact on spectral normalized water leaving radiances and the derived ocean color products (inherent optical properties, chlorophyll ). We...leaving radiances and the derived ocean color products (inherent optical properties, chlorophyll ). We evaluated the influence of gains from open and...34gain" on ocean color products. These products include the spectral Remote Sensing Reflectance (RRS), chlorophyll concentration, and Inherent Optical

50 CFR 648.15 - Facilitation of enforcement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... ocean quahog open access permitted vessels. Vessel owners or operators issued an open access surfclam or ocean quahog open access permit for fishing in the ITQ Program, as specified at § 648.70, are required... limited access permitted vessels. Beginning January 1, 2009, vessel owners or operators issued a limited...

Role of the Indonesian Throughflow in controlling regional mean climate and rainfall variability

NASA Astrophysics Data System (ADS)

England, Matthew H.; Santoso, Agus; Phipps, Steven; Ummenhofer, Caroline

2017-04-01

The role of the Indonesian Throughflow (ITF) in controlling regional mean climate and rainfall is examined using a coupled ocean-atmosphere general circulation model. Experiments employing both a closed and open ITF are equilibrated to steady state and then 200 years of natural climatic variability is assessed within each model run, with a particular focus on the Indian Ocean region. Opening of the ITF results in a mean Pacific-to-Indian throughflow of 21 Sv (1 Sv = 106 m3 sec-1), which advects warm west Pacific waters into the east Indian Ocean. This warm signature is propagated westward by the mean ocean flow, however it never reaches the west Indian Ocean, as an ocean-atmosphere feedback in the tropics generates a weakened trade wind field that is reminiscent of the negative phase of the Indian Ocean Dipole (IOD). This is in marked contrast to the Indian Ocean response to an open ITF when examined in ocean-only model experiments; which sees a strengthening of both the Indian Ocean South Equatorial Current and the Agulhas Current. The coupled feedback in contrast leads to cooler conditions over the west Indian Ocean, and an anomalous zonal atmospheric pressure gradient that enhances the advection of warm moist air toward south Asia and Australia. This leaves the African continent significantly drier, and much of Australia and southern Asia significantly wetter, in response to the opening of the ITF. Given the substantial interannual variability that the ITF exhibits in the present-day climate system, and the restriction of the ITF gateway in past climate eras, this could have important implications for understanding past and present regional rainfall patterns around the Indian Ocean and over neighbouring land-masses.

How much riverine nutrients do shelf seas allow into the open ocean?

NASA Astrophysics Data System (ADS)

Sharples, J.; Fennel, K.; Jickells, T. D.

2016-02-01

Globally rivers deliver 35 Tg of dissolved N and 2 Tg of dissolved P into the coastal zone each year. Investigating the effects of this nutrient supply on the open ocean generally takes one of two approaches: either all or none of the nutrients are assumed to enter the open ocean. Here we use some general assumptions on the behaviour of river plumes on the shelf to arrive at an estimate of the proportions of dissolved N and P that are processed on the shelf, and thus the amount of riverine nutrient that enters the open ocean. Using the Global NEWS database of 6000 rivers we assume that discharges to the shelf are initially constrained within coastal buoyancy currents of width 2 internal Rossby radii. This width is compared to the local shelf width for each river. For plume widths greater than the shelf width riverine nutrients are assumed to be transported over the shelf edge within the plume. For plume widths less than the shelf width we assume that exchange with the open ocean is controlled by physical processes at the shelf break. For each river an estimate of the residence time of riverine water is made, based on the transport or exchange rate and the shelf volume. Empirical relationships between residence time and the proportion of supplied N and P that is retained on the shelf are then used to estimate the amount of dissolved N and P that escapes to the open ocean. The results suggest that 25% of dissolved N and 20% of dissolved P are processed in shelf seas, with the rest exported to the open ocean. There is a latitudinal pattern, with tropical rivers delivering more nutrients to the open ocean. This is partially a result of the high discharges of some tropical rivers, but a key issue is our assumption of the internal Rossby radius governing plume width. A range of values for transport rates within plumes and exchange rates across the shelf break are used to assess the sensitivity of these results, which appear to be robust.

Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a

NASA Astrophysics Data System (ADS)

Erba, Elisabetta; Bottini, Cinzia; Weissert, Helmut J.; Keller, Christina E.

2010-07-01

Ocean acidification induced by atmospheric CO2 may be a major threat to marine ecosystems, particularly to calcareous nannoplankton. We show that, during the Aptian (~120 million years ago) Oceanic Anoxic Event 1a, which resulted from a massive addition of volcanic CO2, the morphological features of calcareous nannofossils traced the biological response to acidified surface waters. We observe the demise of heavily calcified nannoconids and reduced calcite paleofluxes at the beginning of a pre-anoxia calcification crisis. Ephemeral coccolith dwarfism and malformation represent species-specific adjustments to survive lower pH, whereas later, abundance peaks indicate intermittent alkalinity recovery. Deepwater acidification occurred with a delay of 25,000 to 30,000 years. After the dissolution climax, nannoplankton and carbonate recovery developed over ~160,000 years under persisting global dysoxia-anoxia.

Pelagic Biocarbonates: Assessing the "Forgotten" Fine Fraction

NASA Astrophysics Data System (ADS)

Brummer, G. J. A.

2016-02-01

Biocarbonates play an important role in the global carbon cycle and cover over half of the ocean floor. Biocarbonates in the open ocean are best known from planktonic foraminifera, which are relatively large (>150µm), heavy and few and coccoliths, which are very small (<32µm), light and abundant. Both of these components are relatively well studied. The size fraction in between adult foraminifera and coccoliths (32-150µm: the so-called fine fraction) consists of a large but poorly known mixture of particles, which is genarlly assumed to consist primarily of "juvenile" planktonic foraminifera, with minor amounts of calcareous dinoflagellates and various others less well-known microfossils. Abundance, diversity, mass and composition within the fine fraction are poorly constrained, as is the response to acidification/dissolution. This lack of knowledge primarily reflects the gap in size fraction studied by the different disciplinary approaches and techniques, which are not suited for identifying and quantifying these intermediate groups. Comparative ontogeny of planktonic foraminifera now shows that this fine fraction in sediments does not consist of "juveniles" as in the living plankton, but is dominated by mature specimens of small-sized species. First estimates indicate that these small species not only account for about one third of the number of species of planktonic foraminifera but also form about one third of their shell flux and global carbonate production in weight. Still, we hardly know anything on seasonality, depth habitat, shell composition (isotopes, trace metal incorporation), potential autotrophic symbionts, molecular genetics and geological range of these clearly very important species. Estimates from well-preserved sediments, show that the important role of these minute foraminiferal planktonic species may hold for much of the 180Ma long fossil record, opening a new research field pertaining to both modern and past pelagic ecosystems and the role of these species in global carbon cycles.

Biogeochemistry of silica in Devils Lake: Implications for diatom preservation

USGS Publications Warehouse

Lent, R.M.; Lyons, B.

2001-01-01

Diatom-salinity records from sediment cores have been used to construct climate records of saline-lake basins. In many cases, this has been done without thorough understanding of the preservation potential of the diatoms in the sediments through time. The purpose of this study was to determine the biogeochemistry of silica in Devils Lake and evaluate the potential effects of silica cycling on diatom preservation. During the period of record, 1867-1999, lake levels have fluctuated from 427 m above sea level in 1940 to 441.1 m above sea level in 1999. The biogeochemistry of silica in Devils Lake is dominated by internal cycling. During the early 1990s when lake levels were relatively high, about 94% of the biogenic silica (BSi) produced in Devils Lake was recycled in the water column before burial. About 42% of the BSi that was incorporated in bottom sediments was dissolved and diffused back into the lake, and the remaining 58% was buried. Therefore, the BSi accumulation rate was about 3% of the BSi assimilation rate. Generally, the results obtained from this study are similar to those obtained from studies of the biogeochemistry of silica in large oligotrophic lakes and the open ocean where most of the BSi produced is recycled in surface water. During the mid 1960s when lake levels were relatively low, BSi assimilation and water-column dissolution rates were much higher than when lake levels were high. The BSi assimilation rate was as much as three times higher during low lake levels. Even with the much higher BSi assimilation rate, the BSi accumulation rate was about three times lower because the BSi water-column dissolution rate was more than 99% of the BSi assimilation rate compared to 94% during high lake levels. Variations in the biogeochemistry of silica with lake level have important implications for paleolimnologic studies. Increased BSi water-column dissolution during decreasing lake levels may alter the diatom-salinity record by selectively removing the less resistant diatoms. Also, BSi accumulation may be proportional to the amount of silica input from tributary sources. Therefore, BSi accumulation chronologies from sediment cores may be effective records of tributary inflow.

Drake passage and central american seaway controls on the distribution of the oceanic carbon reservoir

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fyke, Jeremy G.; D'Orgeville, Marc; Weaver, Andrew J.

2015-05-01

A coupled carbon/climate model is used to explore the impact of Drake Passage opening and Central American Seaway closure on the distribution of carbon in the global oceans. We find that gateway evolution likely played an important role in setting the modern day distribution of oceanic dissolved inorganic carbon (DIC), which is currently characterized by relatively low concentrations in the Atlantic ocean, and high concentrations in the Southern, Indian, and Pacific oceans. In agreement with previous studies, we find a closed Drake Passage in the presence of an open Central American Seaway results in suppressed Atlantic meridional overturning and enhancedmore » southern hemispheric deep convection. Opening of the Drake Passage triggers Antarctic Circumpolar Current flow and a weak Atlantic meridional overturning circulation (AMOC). Subsequent Central American Seaway closure reinforces the AMOC while also stagnating equatorial Pacific subsurface waters. These gateway-derived oceanographic changes are reflected in large shifts to the global distribution of DIC. An initially closed Drake Passage results in high DIC concentrations in the Atlantic and Arctic oceans, and lower DIC concentrations in the Pacific/Indian/Southern oceans. Opening Drake Passage reverses this gradient by lowering mid-depth Atlantic and Arctic DIC concentrations and raising deep Pacific/Indian/Southern Ocean DIC concentrations. Central American Seaway closure further reinforces this trend through additional Atlantic mid-depth DIC decreases, as well as Pacific mid-depth DIC concentration increases, with the net effect being a transition to a modern distribution of oceanic DIC.« less

Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition

NASA Astrophysics Data System (ADS)

Goldner, A.; Herold, N.; Huber, M.

2014-07-01

Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

PubMed

Goldner, A; Herold, N; Huber, M

2014-07-31

Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

A hybrid model of the CO2 geochemical cycle and its application to large impact events

NASA Technical Reports Server (NTRS)

Kasting, J. F.; Pollack, J. B.; Toon, O. B.; Richardson, S. M.

1986-01-01

The effects of a large asteriod or comet impact on modern and ancient marine biospheres are analyzed. A hybrid model of the carbonate-silicate geochemical cycle, which is capable of calculating the concentrations of carbon dioxide in the atmosphere, ocean, and sedimentary rocks, is described. The differences between the Keir and Berger (1983) model and the hybrid model are discussed. Equilibrium solutions are derived for the preindustrial atmosphere/ocean system and for a system similar to that of the late Cretaceous Period. The model data reveal that globl darkening caused by a stratospheric dust veil could destroy the existing phytoplankton within a period of several weeks or months, nd the dissolution of atmospheric NO(x) compounds would lower the pH of ocean surface waters and release CO2 into the atmosphere. It is noted that the surface temperatures could be increased by several degrees and surface oceans would be uninhabitable for calcaerous organisms for approximately 20 years.

78 FR 69395 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-19

...: Department of the Navy, DoD. ACTION: Notice of Open Meeting. SUMMARY: The Ocean Research Advisory Panel will hold a regularly scheduled meeting. The meeting will be open to the public. Members of the public who..., Arlington, VA 22203- 1995, telephone 703-696-4532. SUPPLEMENTARY INFORMATION: This notice of open meeting is...

78 FR 57371 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-18

...: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research Advisory Panel will hold a regularly scheduled meeting. The meeting will be open to the public. DATES: The meeting will be..., VA 22203- 1995, telephone 703-696-4532. SUPPLEMENTARY INFORMATION: This notice of open meeting is...

Distribution of ferromanganese nodules in the Pacific Ocean.

USGS Publications Warehouse

Piper, D.Z.; Swint-Iki, T.R.; McCoy, F.W.

1987-01-01

The occurrence and distribution of deep-ocean ferromanganese nodules are related to the lithology of pelagic surface-sediment, sediment accumulation rates, sea-floor bathymetry, and benthic circulation. Nodules often occur in association with both biosiliceous and pelagic clay, and less often with calcareous sediment. Factors which influence the rather complex patterns of sediment lithology and accumulation rates include the supply of material to the sea-floor and secondary processes in the deep ocean which alter or redistribute that supply. The supply is largely controlled by: 1) proximity to a source of alumino-silicate material and 2) primary biological productivity in the photic zone of the ocean. Primary productivity controls the 'rain' to the sea-floor of biogenic detritus, which consists mostly of siliceous and calcareous tests of planktonic organisms but also contains smaller proportions of phosphatic material and organic matter. The high accumulation rate (5 mm/1000 yr) of sediment along the equator is a direct result of high productivity in this region of the Pacific. Secondary processes include the dissolution of particulate organic matter at depth in the ocean, notably CaCO3, and the redistribution of sedimentary particles by deep-ocean currents. -J.M.H.

Difference in the Dissolution Behaviors of Tablets Containing Polyvinylpolypyrrolidone (PVPP) Depending on Pharmaceutical Formulation After Storage Under High Temperature and Humid Conditions.

PubMed

Takekuma, Yoh; Ishizaka, Haruka; Sumi, Masato; Sato, Yuki; Sugawara, Mitsuru

Storage under high temperature and humid conditions has been reported to decrease the dissolution rate for some kinds of tablets containing polyvinylpolypyrrolidone (PVPP) as a disintegrant. The aim of this study was to elucidate the properties of pharmaceutical formulations with PVPP that cause a decrease in the dissolution rate after storage under high temperature and humid conditions by using model tablets with a simple composition. Model tablets, which consisted of rosuvastatin calcium or 5 simple structure compounds, salicylic acid, 2-aminodiphenylmethane, 2-aminobiphenyl, 2-(p-tolyl)benzoic acid or 4.4'-biphenol as principal agents, cellulose, lactose hydrate, PVPP and magnesium stearate as additives, were made by direct compression. The model tables were wrapped in paraffin papers and stored for 2 weeks at 40°C/75% relative humidity (RH). Dissolution tests were carried out by the paddle method in the Japanese Pharmacopoeia 16th edition. Model tablets with a simple composition were able to reproduce a decreased dissolution rate after storage at 40°C/75% RH. These tablets showed significantly decreased water absorption activities after storage. In the case of tablets without lactose hydrate by replacing with cellulose, a decreased dissolution rate was not observed. Carboxyl and amino groups in the structure of the principal agent were not directly involved in the decreased dissolution. 2-Benzylaniline tablets showed a remarkably decreased dissolution rate and 2-aminobiphenyl and 2-(p-tolyl)benzoic acid tablets showed slightly decreased dissolution rates, though 4,4'-biphenol tablets did not show a decrease dissolution rate. We demonstrated that additives and structure of the principal agent were involved in the decreased in dissolution rate for tablets with PVPP. The results suggested that one of the reasons for a decreased dissolution rate was the inclusion of lactose hydrate in tablets. The results also indicated that compounds as principal agents with low affinity for PVPP may be easily affected by airborne water under high temperature and humid conditions. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Outer organic layer and internal repair mechanism protects pteropod Limacina helicina from ocean acidification

NASA Astrophysics Data System (ADS)

Peck, Victoria L.; Tarling, Geraint A.; Manno, Clara; Harper, Elizabeth M.; Tynan, Eithne

2016-05-01

Scarred shells of polar pteropod Limacina helicina collected from the Greenland Sea in June 2012 reveal a history of damage, most likely failed predation, in earlier life stages. Evidence of shell fracture and subsequent re-growth is commonly observed in specimens recovered from the sub-Arctic and further afield. However, at one site within sea-ice on the Greenland shelf, shells that had been subject to mechanical damage were also found to exhibit considerable dissolution. It was evident that shell dissolution was localised to areas where the organic, periostracal sheet that covers the outer shell had been damaged at some earlier stage during the animal's life. Where the periostracum remained intact, the shell appeared pristine with no sign of dissolution. Specimens which appeared to be pristine following collection were incubated for four days. Scarring of shells that received periostracal damage during collection only became evident in specimens that were incubated in waters undersaturated with respect to aragonite, ΩAr≤1. While the waters from which the damaged specimens were collected at the Greenland Sea sea-ice margin were not ΩAr≤1, the water column did exhibit the lowest ΩAr values observed in the Greenland and Barents Seas, and was likely to have approached ΩAr≤1 during the winter months. We demonstrate that L. helicina shells are only susceptible to dissolution where both the periostracum has been breached and the aragonite beneath the breach is exposed to waters of ΩAr≤1. Exposure of multiple layers of aragonite in areas of deep dissolution indicate that, as with many molluscs, L. helicina is able to patch up dissolution damage to the shell by secreting additional aragonite internally and maintain their shell. We conclude that, unless breached, the periostracum provides an effective shield for pteropod shells against dissolution in waters ΩAr≤1, and when dissolution does occur the animal has an effective means of self-repair. We suggest that future studies of pteropod shell condition are undertaken on specimens from which the periostracum has not been removed in preparation.

Horizontal variability of the marine boundary layer structure upwind of San Nicolas Island during FIRE, 1987

NASA Technical Reports Server (NTRS)

Jensen, Douglas R.

1990-01-01

During the months of June and July 1987, the Marine Stratocumulus Intensive Field Observation Experiment of First ISCCP Regional Experiment (FIRE) was conducted in the Southern California offshore area in the vicinity of San Nicolas Island (SNI). The Naval Ocean Systems Center (NOSC) airborne platform was utilized during FIRE to investigate the upwind low level horizontal variability of the marine boundary layer structure to determine the representativeness of SNI-based measurements to upwind open ocean conditions. The NOSC airborne meteorological platform made three flights during FIRE, two during clear sky conditions (19 and 23 July), and one during two stratus conditions (15 July). The boundary layer structure variations associated with the stratus clouds of 15 July 1987 are discussed. Profiles of air temperature (AT) and relative humidity (RH) taken 'at' and 'upwind' of SNI do show differences between the so-called open ocean conditions and those taken near the island. However, the observed difference cannot be uniquely identified to island effects, especially since the upwind fluctuations of AT and RH bound the SNI measurements. Total optical depths measures at SNI do not appear to be greatly affected by any surface based aerosol effects created by the island and could therefore realistically represent open ocean conditions. However, if one were to use the SNI aerosol measurements to predict ship to ship EO propagation conditions, significant errors could be introduced due to the increased number of surface aerosols observed near SNI which may not be, and were not, characteristic of open ocean conditions. Sea surface temperature measurements taken at the island will not, in general, represent those upwind open ocean conditions. Also, since CTT's varied appreciably along the upwind radials, measurements of CTT over the island may not be representative of actual open ocean CTT's.

Elevated Colonization of Microborers at a Volcanically Acidified Coral Reef

PubMed Central

Enochs, Ian C.; Manzello, Derek P.; Tribollet, Aline; Valentino, Lauren; Kolodziej, Graham; Donham, Emily M.; Fitchett, Mark D.; Carlton, Renee; Price, Nichole N.

2016-01-01

Experiments have demonstrated that ocean acidification (OA) conditions projected to occur by the end of the century will slow the calcification of numerous coral species and accelerate the biological erosion of reef habitats (bioerosion). Microborers, which bore holes less than 100 μm diameter, are one of the most pervasive agents of bioerosion and are present throughout all calcium carbonate substrates within the reef environment. The response of diverse reef functional groups to OA is known from real-world ecosystems, but to date our understanding of the relationship between ocean pH and carbonate dissolution by microborers is limited to controlled laboratory experiments. Here we examine the settlement of microborers to pure mineral calcium carbonate substrates (calcite) along a natural pH gradient at a volcanically acidified reef at Maug, Commonwealth of the Northern Mariana Islands (CNMI). Colonization of pioneer microborers was higher in the lower pH waters near the vent field. Depth of microborer penetration was highly variable both among and within sites (4.2–195.5 μm) over the short duration of the study (3 mo.) and no clear relationship to increasing CO2 was observed. Calculated rates of biogenic dissolution, however, were highest at the two sites closer to the vent and were not significantly different from each other. These data represent the first evidence of OA-enhancement of microboring flora colonization in newly available substrates and provide further evidence that microborers, especially bioeroding chlorophytes, respond positively to low pH. The accelerated breakdown and dissolution of reef framework structures with OA will likely lead to declines in structural complexity and integrity, as well as possible loss of essential habitat. PMID:27467570

Elevated Colonization of Microborers at a Volcanically Acidified Coral Reef.

PubMed

Enochs, Ian C; Manzello, Derek P; Tribollet, Aline; Valentino, Lauren; Kolodziej, Graham; Donham, Emily M; Fitchett, Mark D; Carlton, Renee; Price, Nichole N

2016-01-01

Experiments have demonstrated that ocean acidification (OA) conditions projected to occur by the end of the century will slow the calcification of numerous coral species and accelerate the biological erosion of reef habitats (bioerosion). Microborers, which bore holes less than 100 μm diameter, are one of the most pervasive agents of bioerosion and are present throughout all calcium carbonate substrates within the reef environment. The response of diverse reef functional groups to OA is known from real-world ecosystems, but to date our understanding of the relationship between ocean pH and carbonate dissolution by microborers is limited to controlled laboratory experiments. Here we examine the settlement of microborers to pure mineral calcium carbonate substrates (calcite) along a natural pH gradient at a volcanically acidified reef at Maug, Commonwealth of the Northern Mariana Islands (CNMI). Colonization of pioneer microborers was higher in the lower pH waters near the vent field. Depth of microborer penetration was highly variable both among and within sites (4.2-195.5 μm) over the short duration of the study (3 mo.) and no clear relationship to increasing CO2 was observed. Calculated rates of biogenic dissolution, however, were highest at the two sites closer to the vent and were not significantly different from each other. These data represent the first evidence of OA-enhancement of microboring flora colonization in newly available substrates and provide further evidence that microborers, especially bioeroding chlorophytes, respond positively to low pH. The accelerated breakdown and dissolution of reef framework structures with OA will likely lead to declines in structural complexity and integrity, as well as possible loss of essential habitat.

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind-Wave Coupling

DTIC Science & Technology

2015-09-30

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind- Wave Coupling Peter S. Guest (NPS Technical Contact) Naval...surface fluxes and ocean waves in coupled models in the Beaufort and Chukchi Seas. 2. Understand the physics of heat and mass transfer from the ocean...to the atmosphere. 3. Improve forecasting of waves on the open ocean and in the marginal ice zone. 2 OBJECTIVES 1. Quantifying the open-ocean

Enhanced open ocean storage of CO2 from shelf sea pumping.

PubMed

Thomas, Helmuth; Bozec, Yann; Elkalay, Khalid; de Baar, Hein J W

2004-05-14

Seasonal field observations show that the North Sea, a Northern European shelf sea, is highly efficient in pumping carbon dioxide from the atmosphere to the North Atlantic Ocean. The bottom topography-controlled stratification separates production and respiration processes in the North Sea, causing a carbon dioxide increase in the subsurface layer that is ultimately exported to the North Atlantic Ocean. Globally extrapolated, the net uptake of carbon dioxide by coastal and marginal seas is about 20% of the world ocean's uptake of anthropogenic carbon dioxide, thus enhancing substantially the open ocean carbon dioxide storage.

Sensitivity of open-water ice growth and ice concentration evolution in a coupled atmosphere-ocean-sea ice model

NASA Astrophysics Data System (ADS)

Shi, Xiaoxu; Lohmann, Gerrit

2017-09-01

A coupled atmosphere-ocean-sea ice model is applied to investigate to what degree the area-thickness distribution of new ice formed in open water affects the ice and ocean properties. Two sensitivity experiments are performed which modify the horizontal-to-vertical aspect ratio of open-water ice growth. The resulting changes in the Arctic sea-ice concentration strongly affect the surface albedo, the ocean heat release to the atmosphere, and the sea-ice production. The changes are further amplified through a positive feedback mechanism among the Arctic sea ice, the Atlantic Meridional Overturning Circulation (AMOC), and the surface air temperature in the Arctic, as the Fram Strait sea ice import influences the freshwater budget in the North Atlantic Ocean. Anomalies in sea-ice transport lead to changes in sea surface properties of the North Atlantic and the strength of AMOC. For the Southern Ocean, the most pronounced change is a warming along the Antarctic Circumpolar Current (ACC), owing to the interhemispheric bipolar seasaw linked to AMOC weakening. Another insight of this study lies on the improvement of our climate model. The ocean component FESOM is a newly developed ocean-sea ice model with an unstructured mesh and multi-resolution. We find that the subpolar sea-ice boundary in the Northern Hemisphere can be improved by tuning the process of open-water ice growth, which strongly influences the sea ice concentration in the marginal ice zone, the North Atlantic circulation, salinity and Arctic sea ice volume. Since the distribution of new ice on open water relies on many uncertain parameters and the knowledge of the detailed processes is currently too crude, it is a challenge to implement the processes realistically into models. Based on our sensitivity experiments, we conclude a pronounced uncertainty related to open-water sea ice growth which could significantly affect the climate system sensitivity.

First order sea-level cycles and supercontinent break up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heller, P.L.; Angevine, C.L.

1985-01-01

The authors have developed a model that successfully predicts the approximate magnitude and timing of long term sea-level change without relying on short term increases in global spreading rates. The model involves the following key assumptions. (1) Ocean basins have two types of area/age distributions; Pacific ocean basins are rimmed by subduction zones and have triangular distributions; and Atlantic ocean basins which open at constant rates, have no subduction, and so have rectangular distributions. (2) The total area of the global ocean is constant so that the Pacific basin must close as the Atlantic opens. These assumptions approximate modern globalmore » ocean basin conditions. The model begins with supercontinent break up. As the Atlantic begins to open, the mean age of the global ocean decreases, the mean depth of the sea floor shallows, and sea level, therefore, rises. Once the Atlantic occupies more than 8 to 10% of the global ocean area, the mean age and depth of the ocean floor increases resulting in a sea-level fall. The model can be applied to the mid-Cretaceous sea-level high stand which followed break up of Pangea by 80 to 100 Ma. Based on average Atlantic opening rates, sea level rises to a peak of 44 m at 80 Ma after opening began and then falls by 84 m to the present. Thus the model is capable of explaining approximately half of the total magnitude of the post-mid-Cretaceous eustatic fall without invoking short-term changes in global spreading rates. In addition, the model predicts the observed time lag between supercontinent break up and sea-level high stand for both Mesozoic as well as early Paleozoic time.« less

Calcification is not the Achilles' heel of cold-water corals in an acidifying ocean.

PubMed

Rodolfo-Metalpa, Riccardo; Montagna, Paolo; Aliani, Stefano; Borghini, Mireno; Canese, Simonepietro; Hall-Spencer, Jason M; Foggo, Andy; Milazzo, Marco; Taviani, Marco; Houlbrèque, Fanny

2015-06-01

Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Ωara ) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2  1058 μatm, Ωara 1.29), and nor are the rates of skeletal dissolution in D. dianthus. We transplanted D. dianthus to 350 m depth (pHT 8.02; pCO2  448 μatm, Ωara 2.58) and to a 3 m depth CO2 seep in oligotrophic waters (pHT 7.35; pCO2  2879 μatm, Ωara 0.76) and found that the transplants calcified at the same rates regardless of the pCO2 confirming their resilience to acidification, but at significantly lower rates than corals that were fed in aquaria. Our combination of field and laboratory evidence suggests that ocean acidification will not disrupt cold-water coral calcification although falling aragonite levels may affect other organismal physiological and/or reef community processes. © 2015 John Wiley & Sons Ltd.

Evidence from Ocean Drilling Program Leg 149 mafic igneous rocks for oceanic crust in the Iberia Abyssal Plain ocean-continent transition zone

NASA Astrophysics Data System (ADS)

Seifert, Karl E.; Chang, Cheng-Wen; Brunotte, Dale A.

1997-04-01

Leg 149 of the Ocean Drilling Program explored the ocean-continent transition (OCT) on the Iberia Abyssal Plain and its role in the opening of the Atlantic Ocean approximately 130 Ma. Mafic igneous rocks recovered from Holes 899B and 900A have Mid-Ocean Ridge Basalt (MORB) trace element and isotopic characteristics indicating that a spreading center was active during the opening of the Iberia Abyssal Plain OCT. The Hole 899B weathered basalt and diabase clasts have transitional to enriched MORB rare earth element characteristics, and the Hole 900A metamorphosed gabbros have MORB initial epsilon Nd values between +6 and +11. During the opening event the Iberia Abyssal Plain OCT is envisioned to have resembled the central and northern parts of the present Red Sea with localized spreading centers and magma chambers producing localized patches of MORB mafic rocks. The lack of a normal ocean floor magnetic anomaly pattern in the Iberia Abyssal Plain means that a continuous spreading center similar to that observed in the present southern Red Sea was not formed before spreading ceased in the Iberia Abyssal Plain OCT and jumped to the present Mid-Atlantic Ridge.

Coccolithophore export production during the last deglaciation at ODP Site 1089 (Southern Ocean)

NASA Astrophysics Data System (ADS)

Balestrieri, Chiara; Ziveri, Patrizia; Mortyn, Peter Graham; Fornaciari, Eliana; Agnini, Claudia

2017-04-01

In order to assess the Southern Ocean carbonate budget change during the last deglaciation we evaluated the significance of calcification changes observed in calcareous nannofossil assemblages. In particular, we analysed coccolithophore assemblages from TNO57-21, a site survey core drilled as part of ODP Site 1089 (40°57'S; 9°53'E, 4620 m water depth), over the last 25 ky in the Subantarctic South Atlantic. This region is characterized by strong hydrographic gradients and ODP Site 1089 is optimally located in order to monitor the evolution of the Subtropical Front and Subpolar Front and the Agulhas Current (Flores et al., 2003) through time. The mean sedimentation rate is in the range of 15-20 cm/kyr, and the recovery of coccolith-bearing sediments provides a powerful tool to study deep-sea carbonate export production at high-resolution. Much of the CO2 drawdown from the atmosphere has been proposed to be stored into the deep ocean but evidence for increased carbon storage are still elusive (Martínez- Botí et al., 2015). Here, we present data on the Florisphaera profunda index and CaCO3 concentrations per gram of dry sediment, which were used to intepret the productivity trend during the last 25 kyr. These data clearly show a decrease in carbonate production throughout the last deglaciation. Moreover, we have calculated the Calcidiscus leptoporus-Emiliania huxleyi dissolution index (CEX'), which suggests a strong link between increasing coccolith dissolution and the evolution of the bottom water mass dynamics during Termination 1 (TI). Finally, mass estimations of the coccolith carbonate allow us to assess the role of each species as carbonate producers across this time span. These results reveal that during the last 25 ky the productivity was influenced by the mid-latitude westerlies, the study site was bathed by different bottom water masses, and was affected by a shoaling of the lysocline during T1 and the Holocene. References Flores J-A., Marino M., Sierro F.J., Hodell D.A., Charles C.D., 2003. Calcareous plankton dissolution pattern and coccolithophore assemblages during the last 600 kyr at ODP Site 1089 (Cape Basin, South Atlantic): paleoceanographic implications. Palaeogeography Palaeoclimatology Palaeoecology. 196:409-426. Martínez-Botí M.A., Marino G., Foster G.L., Ziveri P., Henehan M.J., Rae J.W., Mortyn P.G., Vance D., 2015. Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation. Nature. 518(7538):219-22.

Drivers of Water Column Calcium Carbonate Fluxes and Dissolution in the Gulf of Maine: Impacts on the Carbon Cycle

NASA Astrophysics Data System (ADS)

Pilskaln, C. H.; Wang, A. Z.; Lawson, G. L.; Hayashi, K.; Salisbury, J.

2016-02-01

Recent studies indicate that the U.S. Northeast coastal region, particularly the Gulf of Maine (GoME), may be more susceptible to ocean acidification (OA) than previously thought due to the low buffer capacity, low pH, and low calcium carbonate saturation measured in the region. In particular, sub-surface waters of the GoME already experience under-saturation with respect to aragonite in spring and summer and recent data suggest that water-column aragonite dissolution may occur throughout the year, even when aragonite is slightly over-saturated. This dissolution process appears associated with organic carbon remineralization in the extensive benthic nepheloid layers and may thus represent a major control over the calcium carbonate (CaCO3) budget of deep, near-bottom waters of the GoME. These findings are surprising for shallow, non-upwelling shelf systems and have important implications for the CaCO3 cycle, shell-building organisms, and the GoME planktonic ecosystem. Additionally, freshening of the GoME over the past several decades due to an increase in low-salinity water input originating in the Labrador Sea may further decrease seawater pH and aragonite saturation in the gulf. We present a variety of biogeochemical data that suggest linkages between potential water column CaCO3 dissolution and their impacts on the GoME carbon cycle.

Open science resources for the discovery and analysis of Tara Oceans data

PubMed Central

Pesant, Stéphane; Not, Fabrice; Picheral, Marc; Kandels-Lewis, Stefanie; Le Bescot, Noan; Gorsky, Gabriel; Iudicone, Daniele; Karsenti, Eric; Speich, Sabrina; Troublé, Romain; Dimier, Céline; Searson, Sarah; Acinas, Silvia G.; Bork, Peer; Boss, Emmanuel; Bowler, Chris; Vargas, Colomban De; Follows, Michael; Gorsky, Gabriel; Grimsley, Nigel; Hingamp, Pascal; Iudicone, Daniele; Jaillon, Olivier; Kandels-Lewis, Stefanie; Karp-Boss, Lee; Karsenti, Eric; Krzic, Uros; Not, Fabrice; Ogata, Hiroyuki; Pesant, Stéphane; Raes, Jeroen; Reynaud, Emmanuel G.; Sardet, Christian; Sieracki, Mike; Speich, Sabrina; Stemmann, Lars; Sullivan, Matthew B.; Sunagawa, Shinichi; Velayoudon, Didier; Weissenbach, Jean; Wincker, Patrick

2015-01-01

The Tara Oceans expedition (2009–2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events. PMID:26029378

Open science resources for the discovery and analysis of Tara Oceans data

NASA Astrophysics Data System (ADS)

2015-05-01

The Tara Oceans expedition (2009-2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events.

Large mesopelagic fishes biomass and trophic efficiency in the open ocean.

PubMed

Irigoien, Xabier; Klevjer, T A; Røstad, A; Martinez, U; Boyra, G; Acuña, J L; Bode, A; Echevarria, F; Gonzalez-Gordillo, J I; Hernandez-Leon, S; Agusti, S; Aksnes, D L; Duarte, C M; Kaartvedt, S

2014-01-01

With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger than the current estimate. Here we combine modelling and a sensitivity analysis of the acoustic observations from the Malaspina 2010 Circumnavigation Expedition to show that the previous estimate needs to be revised to at least one order of magnitude higher. We show that there is a close relationship between the open ocean fishes biomass and primary production, and that the energy transfer efficiency from phytoplankton to mesopelagic fishes in the open ocean is higher than what is typically assumed. Our results indicate that the role of mesopelagic fishes in oceanic ecosystems and global ocean biogeochemical cycles needs to be revised as they may be respiring ~10% of the primary production in deep waters.

Large mesopelagic fishes biomass and trophic efficiency in the open ocean

PubMed Central

Irigoien, Xabier; Klevjer, T. A.; Røstad, A.; Martinez, U.; Boyra, G.; Acuña, J. L.; Bode, A.; Echevarria, F.; Gonzalez-Gordillo, J. I.; Hernandez-Leon, S.; Agusti, S.; Aksnes, D. L.; Duarte, C. M.; Kaartvedt, S.

2014-01-01

With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger than the current estimate. Here we combine modelling and a sensitivity analysis of the acoustic observations from the Malaspina 2010 Circumnavigation Expedition to show that the previous estimate needs to be revised to at least one order of magnitude higher. We show that there is a close relationship between the open ocean fishes biomass and primary production, and that the energy transfer efficiency from phytoplankton to mesopelagic fishes in the open ocean is higher than what is typically assumed. Our results indicate that the role of mesopelagic fishes in oceanic ecosystems and global ocean biogeochemical cycles needs to be revised as they may be respiring ~10% of the primary production in deep waters. PMID:24509953

Open science resources for the discovery and analysis of Tara Oceans data.

PubMed

Pesant, Stéphane; Not, Fabrice; Picheral, Marc; Kandels-Lewis, Stefanie; Le Bescot, Noan; Gorsky, Gabriel; Iudicone, Daniele; Karsenti, Eric; Speich, Sabrina; Troublé, Romain; Dimier, Céline; Searson, Sarah

2015-01-01

The Tara Oceans expedition (2009-2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events.

Global declines in oceanic nitrification rates as a consequence of ocean acidification.

PubMed

Beman, J Michael; Chow, Cheryl-Emiliane; King, Andrew L; Feng, Yuanyuan; Fuhrman, Jed A; Andersson, Andreas; Bates, Nicholas R; Popp, Brian N; Hutchins, David A

2011-01-04

Ocean acidification produced by dissolution of anthropogenic carbon dioxide (CO(2)) emissions in seawater has profound consequences for marine ecology and biogeochemistry. The oceans have absorbed one-third of CO(2) emissions over the past two centuries, altering ocean chemistry, reducing seawater pH, and affecting marine animals and phytoplankton in multiple ways. Microbially mediated ocean biogeochemical processes will be pivotal in determining how the earth system responds to global environmental change; however, how they may be altered by ocean acidification is largely unknown. We show here that microbial nitrification rates decreased in every instance when pH was experimentally reduced (by 0.05-0.14) at multiple locations in the Atlantic and Pacific Oceans. Nitrification is a central process in the nitrogen cycle that produces both the greenhouse gas nitrous oxide and oxidized forms of nitrogen used by phytoplankton and other microorganisms in the sea; at the Bermuda Atlantic Time Series and Hawaii Ocean Time-series sites, experimental acidification decreased ammonia oxidation rates by 38% and 36%. Ammonia oxidation rates were also strongly and inversely correlated with pH along a gradient produced in the oligotrophic Sargasso Sea (r(2) = 0.87, P < 0.05). Across all experiments, rates declined by 8-38% in low pH treatments, and the greatest absolute decrease occurred where rates were highest off the California coast. Collectively our results suggest that ocean acidification could reduce nitrification rates by 3-44% within the next few decades, affecting oceanic nitrous oxide production, reducing supplies of oxidized nitrogen in the upper layers of the ocean, and fundamentally altering nitrogen cycling in the sea.

In-Situ Electrokinetic Remediation for Metal Contaminated Soils

DTIC Science & Technology

2001-03-01

Press. Riddle, M. J. 1988. Patterns in the distribution of macrofauna! communities in coral reef sediments on the central Great Barrier Reef . Mar...acidified. This acidification results in solubilization of contaminants due to desorption and dissolution of species from soil. Once contaminants are...the north and east, the Pacific Ocean on the south and west, and a Ventura County Game Reserve on the west and northwest (Figure 6). The Navy has

An electrochemical quartz crystal microbalance study of magnesium dissolution

NASA Astrophysics Data System (ADS)

Ralston, K. D.; Thomas, S.; Williams, G.; Birbilis, N.

2016-01-01

A quartz crystal microbalance (QCM) was used in conjunction with electrochemical measurements to study dissolution of pure magnesium (Mg) sensors in dilute NaCl electrolytes. Open circuit potential and potentiodynamic polarisation experiments were conducted in 0.01 M NaCl, having pH values 3 (buffered) and 6 (unbuffered). In the pH 3 solution, the Mg sensor showed a net mass-loss during the electrochemical tests, whereas, in the unbuffered pH 6 solution Mg showed a net mass-gain, corresponding to the growth of an Mg(OH)2 film on its surface. The loss in the electrochemical efficiency of Mg dissolution due to such direct parasitic Mg(OH)2 growth has been estimated to be around 17-34%. This loss relates to the low capacities and voltage fluctuations reported during discharge of primary Mg batteries.

Impact of dissolution and carbonate precipitation on carbon storage in basalt

NASA Astrophysics Data System (ADS)

Wells, R. K.; Xiong, W.; Tadeoye, J.; Menefee, A.; Ellis, B. R.; Skemer, P. A.; Giammar, D.

2016-12-01

The spatial evolution of silicate mineral dissolution, carbonate precipitation, and the transport of fluids influence the viability of carbon storage in basalt reservoirs. Dissolution of natural basalt and subsequent carbonate precipitation in systems with different transport processes operating were characterized using static and flow-through (5 mL/hr) experiments at 50, 100, and 150 °C, and 100 bar CO2. Intact samples and cores with milled pathways that simulate fractures were tested. Spatial and mineralogical patterns in dissolution and precipitation were analyzed using optical and electron microscopy, microCT scanning, and surface roughness data. Precipitates and fluid chemistry were analyzed using Raman spectroscopy, SEM-EDS, and ICP-MS. Analysis of the bulk solution and surface topography suggests dissolution of olivine and pyroxene grains begins within hours of the start of the experiments. In flow-through experiments, total effluent cation concentrations reach a peak concentration within a few hours then drop towards a steady state within a few days. In static experiments, the initial rate of cation release is faster than it is after several weeks. In both cases Ca2+, Mg2+, and Fe2+ are the dominant cations in solution in the initial stages of reaction. Lower concentrations of Na2+, K+, and Al3+, and the preservation of feldspar and matrix grains after several weeks of reaction indicate the slow reactivity of these minerals. As the reaction progresses, the surface roughness increases steadily with cavities developing at the sites of olivine and pyroxene grains. Post-reaction analysis of basalt samples reacted at static conditions with milled pathways reveals that both siderite and amorphous silica precipitated within diffusion-limited zones as early as 4-6 weeks. Siderite abundance varies with distance along the pathway with the highest concentration of carbonates 1-2 cm below the fracture opening. Siderite precipitates are large enough to fill fracture opening 100 μm wide within 4-6 weeks.

The ocean quasi-homogeneous layer model and global cycle of carbon dioxide in system of atmosphere-ocean

NASA Astrophysics Data System (ADS)

Glushkov, Alexander; Glushkov, Alexander; Loboda, Nataliya; Khokhlov, Valery; Serbov, Nikoly; Svinarenko, Andrey

The purpose of this paper is carrying out the detailed model of the CO2 global turnover in system of "atmosphere-ocean" with using the ocean quasi-homogeneous layer model. Practically all carried out models are functioning in the average annual regime and accounting for the carbon distribution in bio-sphere in most general form (Glushkov et al, 2003). We construct a modified model for cycle of the carbon dioxide, which allows to reproduce a season dynamics of carbon turnover in ocean with account of zone ocean structure (up quasi-homogeneous layer, thermocline and deepest layer). It is taken into account dependence of the CO2 transfer through the bounder between atmosphere and ocean upon temperature of water and air, wind velocity, buffer mechanism of the CO2 dissolution. The same program is realized for atmosphere part of whole system. It is obtained a tempo-ral and space distribution for concentration of non-organic carbon in ocean, partial press of dissolute CO2 and value of exchange on the border between atmosphere and ocean. It is estimated a role of the wind intermixing of the up ocean layer. The increasing of this effect leads to increasing the plankton mass and further particles, which are transferred by wind, contribute to more quick immersion of microscopic shells and organic material. It is fulfilled investigation of sen-sibility of the master differential equations system solutions from the model parameters. The master differential equa-tions system, describing a dynamics of the CO2 cycle, is numerically integrated by the four order Runge-Cutt method under given initial values of valuables till output of solution on periodic regime. At first it is indicated on possible real-zation of the chaos scenario in system. On our data, the difference of the average annual values for the non-organic car-bon concentration in the up quasi-homogeneous layer between equator and extreme southern zone is 0.15 mol/m3, be-tween the equator and extreme northern zone is 0.12 mol/m3. the maximum amplitude of season oscillations (40° -50° n.l.) is 0.07 mol/m3. A link between global cycle of carbon dioxide and global climate change is investigated. Refrences: Glushkov A.V., Khokhlov V.N., Prepelitsa G.P., Tsenenko I.A., Optics of atmosphere and ocean.-2004.-Vol.14,N7.-p.219-223; Glushkov A.V., Loboda N.S., Khokhlov V.N., Atmospheric Research (Elseiver).-2005.-Vol.77.-P.100-113;Glushkov A.V., Loboda N.S., Khokhlov V.N., Lovett L. Journal of Hydrology (Elseiver).-2006.-Vol. 322. N1-4.-P.14-24; Glushkov A.V., Khokhlov V.N., Loboda N.S., Quart.J.Royal Meteorol. Soc.-2006.-Vol.132.- pp.447-465; Glushkov A.V., Khokhlov V.N., Loboda N.S., Ponomarenko E.L., Environm. Inf. Arch.-2003.-Vol.1.-P.125-130.

Experimental study of carbonate formation in oceanic peridotite

NASA Astrophysics Data System (ADS)

Grozeva, Niya G.; Klein, Frieder; Seewald, Jeffrey S.; Sylva, Sean P.

2017-02-01

Interactions of CO2-rich aqueous fluids with mantle peridotite have major implications for geochemical budgets and microbial life in the shallow oceanic lithosphere through the formation of carbonate minerals and reduced carbon species. However, the underlying mechanisms controlling the transformation of CO2 to carbonates in ultramafic-hosted hydrothermal systems remain incompletely understood. A long-term laboratory experiment was conducted at 300 °C and 35 MPa to investigate serpentinization and carbonate formation pathways during hydrothermal alteration of peridotite. Powdered harzburgite was initially reacted with a Ca-rich aqueous fluid for 14,592 h (608 days) and changes in fluid composition were monitored with time. Once the system reached a steady state, a CO2(aq)-rich fluid was injected and allowed to react with the system for 5907 h (246 days). Fluid speciation and mineral analyses suggest that serpentinization of harzburgite in the CO2-poor system led to the precipitation of serpentine, brucite, magnetite, and minor calcite, in addition to other minor phases including chlorite and sulfur-poor Ni sulfides. The addition of the CO2(aq)-rich fluid caused dolomite, Ca-rich dolomite, and high-Mg calcite to form at the expense of olivine, calcite, and brucite, while serpentine remained unreactive. Replacement textures and mineral assemblages mimic those documented in carbonate-altered seafloor serpentinites, particularly those from the Mid-Atlantic Ridge and the Iberia Margin. In contrast to thermodynamic predictions, magnesite did not form in the experiment because the dissolution of clinopyroxene, in combination with the lack of serpentine reactivity, maintained low Mg/Ca ratios in solution. Clinopyroxene dissolution and unreactive serpentine may similarly maintain low Mg/Ca ratios in submarine serpentinization systems and limit magnesite formation in subseafloor environments. Results of this study suggest that the formation of Ca-Mg carbonates by mineral carbonation is favorable in subseafloor serpentinization systems and likely represents a significant, but poorly quantified, carbon sink in hydrothermally altered oceanic lithosphere at slow-spreading mid-ocean ridges.

A review of ocean color remote sensing methods and statistical techniques for the detection, mapping and analysis of phytoplankton blooms in coastal and open oceans

NASA Astrophysics Data System (ADS)

Blondeau-Patissier, David; Gower, James F. R.; Dekker, Arnold G.; Phinn, Stuart R.; Brando, Vittorio E.

2014-04-01

The need for more effective environmental monitoring of the open and coastal ocean has recently led to notable advances in satellite ocean color technology and algorithm research. Satellite ocean color sensors' data are widely used for the detection, mapping and monitoring of phytoplankton blooms because earth observation provides a synoptic view of the ocean, both spatially and temporally. Algal blooms are indicators of marine ecosystem health; thus, their monitoring is a key component of effective management of coastal and oceanic resources. Since the late 1970s, a wide variety of operational ocean color satellite sensors and algorithms have been developed. The comprehensive review presented in this article captures the details of the progress and discusses the advantages and limitations of the algorithms used with the multi-spectral ocean color sensors CZCS, SeaWiFS, MODIS and MERIS. Present challenges include overcoming the severe limitation of these algorithms in coastal waters and refining detection limits in various oceanic and coastal environments. To understand the spatio-temporal patterns of algal blooms and their triggering factors, it is essential to consider the possible effects of environmental parameters, such as water temperature, turbidity, solar radiation and bathymetry. Hence, this review will also discuss the use of statistical techniques and additional datasets derived from ecosystem models or other satellite sensors to characterize further the factors triggering or limiting the development of algal blooms in coastal and open ocean waters.

Paradise Lost: Uncertainties in melting and melt extraction processes beneath oceanic spreading ridges

NASA Astrophysics Data System (ADS)

Kelemen, P. B.

2014-12-01

In many ways, decompression melting and focused melt transport beneath oceanic spreading ridges is the best understood igneous process on Earth. However, there are remaining - increasing - uncertainties in interpreting residual mantle peridotites. Indicators of degree of melting in residual peridotite are questionable. Yb concentration and spinel Cr# are affected by (a) small scale variations in reactive melt transport, (b) variable extents of melt extraction, and (c) "impregnation", i.e. partial crystallization of cooling melt in pore space. Roughly 75% of abyssal peridotites have undergone major element refertilization. Many may have undergone several melting events. The following three statements are inconsistent: (1) Peridotite melt productivity beyond cpx exhaustion is > 0.1%/GPa. (2) Crustal thickness is independent of spreading rate at rates > 2 cm/yr full rate (excluding ultra-slow spreading ridges). (3) Thermal models predict, and observations confirm, thick thermal boundary layers beneath slow spreading ridges. If (a) melt productivity is << 0.1%/GPa beyond cpx-out, and (b) cpx-out occurs > 15 km below the seafloor beneath most ridges, then the independence of crustal thickness with spreading rate can be understood. Most sampled peridotites from ridges melted beyond cpx-out. Cpx in these rocks formed via impregnation and/or exsolution during cooling. Most peridotites beneath ridges may undergo cpx exhaustion during decompression melting. This would entail an upward modification of potential temperature estimates. Alternatively, perhaps oceanic crustal thickness does vary with spreading rate but this is masked by complicated tectonics and serpentinization at slow-spreading ridges. Dissolution channels (dunites) are predicted to coalesce downstream, but numerical models of these have not shown why > 95% of oceanic crust forms in a zone < 5 km wide. There may be permeability barriers guiding deeper melt toward the ridge, but field studies have not identified them. Permeable "shear bands" may guide melt to the ridge, but their nature in open systems at natural grain size and strain rates is uncertain. 2D and 3D focused solid upwelling due to melt buoyancy deep in the melting region, where pyroxenes are abundant and permeability is low, may warrant renewed attention.

Elemental and isotopic compositions of noble gases in the mantle: Pete's path

NASA Astrophysics Data System (ADS)

Moreira, Manuel; Péron, Sandrine; Colin, Aurélia

2016-04-01

Noble gases are tracers of the origin of the volatiles on Earth and other terrestrial planets. The determination of their isotopic compositions in oceanic basalts allows discriminating between different possible scenarios for the origin of volatiles (chondritic, solar, cometary). However, oceanic basalts show a ubiquitous component having atmospheric noble gas compositions, which reflects a shallow air contamination. This component masks the mantle composition and only step crushing is able to (partially) remove it. Nevertheless, the exact mantle composition is always unconstrained due to the uncertainty on its complete removal. Developed by Pete Burnard (Burnard et al., 1997; Burnard, 1999), single vesicle analysis using laser ablation is a challenging technique to determine the mantle composition, free of atmospheric contamination. We have used this technique to measure He, Ne, Ar isotopes and CO2 in single vesicles from both MORB and OIB (Galapagos, Iceland). Vesicles are located using microtomography and the noble gases are measured using the Noblesse mass spectrometer from IPGP using an Excimer laser to open the vesicles. Both Galapagos and Iceland samples show that the 20Ne/22Ne ratio is limited to ~12.8 in the primitive mantle, suggesting that the origin of the light noble gases can be attributed to irradiated material instead of a simple dissolution of solar gases into a magma ocean (Moreira and Charnoz, 2016). Such a scenario of incorporation of light noble gases by irradiation also explains the terrestrial argon isotopic composition. However, the Kr and Xe contribution of implanted solar wind is small and these two noble gases were carried on Earth by chondrites and/or cometary material. Burnard, P., D. Graham and G. Turner (1997). "Vesicle-specific noble gas analyses of « popping rock »: implications for primordial noble gases in the Earth." Science 276: 568-571. Burnard, P. (1999). "The bubble-by-bubble volatile evolution of two mid-ocean ridge basalts." Earth and Planetary Science Letters 174: 199-211. Moreira, M. and S. Charnoz (2016). "The origin of the neon isotopes in chondrites and Earth." Earth and Planetary Science Letters 433: 249-256.

CaCO3 dissolution by holothurians (sea cucumber): a case study from One Tree Reef, Great Barrier Reef

NASA Astrophysics Data System (ADS)

Schneider, K.; Silverman, J.; Kravitz, B.; Woolsey, E.; Eriksson, H.; Schneider-Mor, A.; Barbosa, S.; Rivlin, T.; Byrne, M.; Caldeira, K.

2012-12-01

Holothurians (sea cucumbers) are among the largest and most important deposit feeder in coral reefs. They play a role in nutrient and CaCO3 cycling within the reef structure. As a result of their digestive process they secrete alkalinity due to CaCO3 dissolution and organic matter degradation forming CO2 and ammonium. In a survey at station DK13 on One Three Reef we found that the population density of holothurians was > 1 individual m-2. The dominant sea cucumber species Holothuria leucospilota was collected from DK13. The increase in alkalinity due to CaCO3 dissolution in aquaria incubations was measured to be 47±7 μmol kg-1 in average per individual. Combining this dissolution rate with the sea cucumbers concentrations at DK13 suggest that they may account for a dissolution rate of 34.9±17.8 mmol m-2 day-1, which is equivalent to about half of night time community dissolution measured in DK13. This indicates that in reefs where the sea cucumber population is healthy and protected from fishing they can be locally important in the CaCO3 cycle. Preliminary result suggests that the CaCO3 dissolution rates are not affected by the chemistry of the sea water they are incubated in. Measurements of the empty digestive track volume of two sea cucumbers H. atra and Stichopus herrmanni were 36 ± 4 ml and 151 ± 14 ml, respectively. Based on these measurements it is estimated that these species process 19 ± 2kg and 80 ± 7kg CaCO3 sand yr-1 per individual, respectively. The annual dissolution rates of H. atra and S. herrmanni are 6.5±1.9g and 9.6±1.4g, respectively, suggest that 0.05±0.02% and 0.1±0.02% of the CaCO3 processed through their gut annually is dissolved. During the incubations the CaCO3 dissolution was 0.07±0.01%, 0.04±0.01% and 0.21±0.05% of the fecal casts for H. atra, H. leucospilota and S. herrmanni, respectively. Our result that the primary parameter determining the CaCO3 dissolution by sea cucumber is the amount of carbonate send in their gut. This suggests that sea cucumber dissolution in the future is not expected to change due to ocean acidification, but as calcification diminishes the proportion of CaCO3 dissolved by Holothurians (in protected reefs) in the coral reefs may increase.

Biomolecular imaging of 13C-butyrate with dissolution-DNP: Polarization enhancement and formulation for in vivo studies

NASA Astrophysics Data System (ADS)

Flori, Alessandra; Giovannetti, Giulio; Santarelli, Maria Filomena; Aquaro, Giovanni Donato; De Marchi, Daniele; Burchielli, Silvia; Frijia, Francesca; Positano, Vincenzo; Landini, Luigi; Menichetti, Luca

2018-06-01

Magnetic Resonance Spectroscopy of hyperpolarized isotopically enriched molecules facilitates the non-invasive real-time investigation of in vivo tissue metabolism in the time-frame of a few minutes; this opens up a new avenue in the development of biomolecular probes. Dissolution Dynamic Nuclear Polarization is a hyperpolarization technique yielding a more than four orders of magnitude increase in the 13C polarization for in vivo Magnetic Resonance Spectroscopy studies. As reported in several studies, the dissolution Dynamic Nuclear Polarization polarization performance relies on the chemico-physical properties of the sample. In this study, we describe and quantify the effects of the different sample components on the dissolution Dynamic Nuclear Polarization performance of [1-13C]butyrate. In particular, we focus on the polarization enhancement provided by the incremental addition of the glassy agent dimethyl sulfoxide and gadolinium chelate to the formulation. Finally, preliminary results obtained after injection in healthy rats are also reported, showing the feasibility of an in vivo Magnetic Resonance Spectroscopy study with hyperpolarized [1-13C]butyrate using a 3T clinical set-up.

Karst landforms revealed at various scales using LiDAR and UAV in semi-arid Brazil: Consideration on karstification processes and methodological constraints

NASA Astrophysics Data System (ADS)

Silva, Orildo L.; Bezerra, Francisco H. R.; Maia, Rubson P.; Cazarin, Caroline L.

2017-10-01

This paper analyzes different types of karst landforms and their relationships with fracture systems, sedimentary bedding, and fluvial processes. We mapped karst features in the Cretaceous carbonates of the Jandaíra Formation in the Potiguar Basin, Brazil. We used high-resolution digital elevation models acquired using LiDAR and aerial orthophotographs acquired using an unmanned aerial vehicle (UAV). We grouped and described karst evolution according to scale and degree of karstification. These degrees of karst evolution are coeval. Fractures are opened by dissolution, forming vertical fluid conduits, whereas coeval dissolution occurs along horizontal layers. This conduit system acts as pathways for water flow. The enlargement of conduits contributes to the collapse of blocks in sinkholes and expansion of caves during an intermediate degree of karstification. Propagation of dissolution can cause the coalescence of sinkholes and the capture of small streams. Fluvial processes dominate karst dissolution at an advanced degree of karstification. Comparisons with previously published ground-penetrating radar (GPR), borehole and seismic surveys in sedimentary basins indicate that these structures can be partially preserved during burial.

Patterns of Genetic Diversity and Co-Existence in Open Ocean Diatoms: the Effects of Water Mass Structure, Selection and Sex

NASA Astrophysics Data System (ADS)

Rynearson, T. A.; Chen, G.

2016-02-01

The open ocean North Atlantic spring bloom influences regional ecology and global biogeochemistry. Diatoms dominate the peak of the bloom and significantly impact productivity and export of organic carbon from the bloom. Despite their key role in a yearly event with global impacts, the genetic diversity and population structure of diatoms that comprise this open ocean bloom are unknown. Here we investigated the population genetics of the diatom Thalassiosira gravida sampled during the 2008 North Atlantic Bloom Experiment using newly-developed microsatellite markers. Here, we show that the genetic diversity of open ocean diatoms is high and that their population structure differs dramatically from coastal diatoms. High levels of genetic diversity were observed across all water samples and did not change during the bloom. Four genetically distinct populations were identified but were not associated with different water masses, depths or time points during the bloom. Instead, all four populations co-existed within samples, spanning different water masses, stages of the bloom and depths of over >300 m. The pattern of genetically distinct, co-existing populations in the open ocean contrasts dramatically with coastal habitats, where distinct populations have not been observed to co-exist at the same time and place. It is likely that populations originate via transport from disparate locations combined with overwintering capacity in the water column or sediments. The pattern of co-existence suggests that the open ocean may serve as a gene pool that harbors different populations that are then available for selection to act upon, which may contribute to the ecological and biogeochemical success of diatoms and influence their long-term evolutionary survival.

Temporal variability of dissolved iron species in the mesopelagic zone at Ocean Station PAPA

NASA Astrophysics Data System (ADS)

Schallenberg, Christina; Ross, Andrew R. S.; Davidson, Ashley B.; Stewart, Gillian M.; Cullen, Jay T.

2017-08-01

Deposition of atmospheric aerosols to the surface ocean is considered an important mechanism for the supply of iron (Fe) to remote ocean regions, but direct observations of the oceanic response to aerosol deposition are sparse. In the high nutrient, low chlorophyll (HNLC) subarctic Pacific Ocean we observed a dissolved Fe and Fe(II) anomaly at depth that is best explained as the result of aerosol deposition from Siberian forest fires in May 2012. Interestingly, there was no evidence of enhanced dFe concentrations in surface waters, nor was there a detectable phytoplankton bloom in response to the suspected aerosol deposition. Dissolved Fe (dFe) and Fe(II) showed the strongest enhancement in the subsurface oxygen deficient zone (ODZ), where oxygen concentrations <50 μmol kg-1 are prevalent. In the upper 200 m, dFe concentrations were at or below historic background levels, consistent with a short residence time of aerosol particles in surface waters and possible scavenging loss of dFe. Aerosol toxicity and/or dominance of particle scavenging over dissolution of Fe in the upper water column may have contributed to the lack of a strong phytoplankton response.

Wind energy input into the upper ocean over a lengthening open water season

NASA Astrophysics Data System (ADS)

Mahoney, A. R.; Rolph, R.; Walsh, J. E.

2017-12-01

Wind energy input into the ocean has important consequences for upper ocean mixing, heat and gas exchange, and air-sea momentum transfer. In the Arctic, the open water season is increasing and extending further into the fall storm season, allowing for more wind energy input into the water column. The rate at which the delayed freeze-up timing extends into fall storm season is an important metric to evaluate because the expanding overlap between the open water period and storm season could contribute a significant amount of wind energy into the water column in a relatively short period of time. We have shown that time-integrated wind speeds over open water in the Chukchi Sea and southern Beaufort region have increased since 1979 through 2014. An integrated wind energy input value is calculated for each year in this domain over the open water season, as well as for periods over partial concentrations of ice cover. Spatial variation of this integrated wind energy is shown along the Alaskan coastline, which can have implications for different rates of coastal erosion. Spatial correlation between average wind speed over open water and open water season length from 1979-2014 show positive values in the southern Beaufort, but negative values in the northern Chukchi. This suggests possible differences in the role of the ocean on open water season length depending on region. We speculate that the warm Pacific water outflow plays a more dominant role in extending the open water season length in the northern Chukchi when compared to the southern Beaufort, and might help explain why we can show there is a relatively longer open water season length there. The negative and positive correlations in wind speeds over open water and open water season length might also be explained by oceanic changes tending to operate on longer timescales than the atmosphere. Seasonal timescales of wind events such as regional differences in overlap of the extended open water season due to regional differences in delayed freeze-up into the fall storm season are also investigated. In addition, we have shown that the increased integrated wind energy input over open water values are more a result of the increased open water season length, rather than the increase in wind speeds over open water.

Potential influence of sea cucumbers on coral reef CaCO3 budget: A case study at One Tree Reef

NASA Astrophysics Data System (ADS)

Schneider, Kenneth; Silverman, Jacob; Woolsey, Erika; Eriksson, Hampus; Byrne, Maria; Caldeira, Ken

2011-12-01

To endure, coral reefs must accumulate CaCO3 at a rate greater or equal than the sum of mechanically, biologically, and chemically mediated erosion rates. We investigated the potential role of holothurians on the CaCO3 balance of a coral reef. These deposit feeders process carbonate sand and rubble through their digestive tract and dissolve CaCO3 as part of their digestive process. In aquarium incubations with Stichopus herrmanni and Holothuria leucospilota total alkalinity increased by 97 ± 13 and 47 ± 7 μmol kg-1, respectively. This increase was due to CaCO3 dissolution, 81 ± 13 and 34 ± 6 μmol kg-1 and ammonia secretion, 16 ± 2 and 14 ± 2μmol kg-1, respectively, for these species. Surveys conducted at a long-term monitoring site of community calcification (DK13) on One Tree Reef indicated that the density of sea cucumbers was approximately 1 individual m-2. We used these data and data from surveys at Shark Alley to estimate the dissolution of CaCO3 by the sea cucumbers at both sites. At DK13 the sea cucumber population was estimated to be responsible for nearly 50% of the nighttime CaCO3 dissolution, while in Shark Alley for most of the nighttime dissolution. Thus, in a healthy reef, bioeroders dissolution of CaCO3 sediment appears to be an important component of the natural CaCO3 turnover and a substantial source of alkalinity as well. This additional alkalinity could partially buffer changes in seawater pH associated with increasing atmospheric CO2 locally, thus reducing the impact of ocean acidification on coral growth.

Lagrangian analysis of multi-satellite data in support of open ocean Marine Protected Area design

NASA Astrophysics Data System (ADS)

Della Penna, Alice; Koubbi, Philippe; Cotté, Cedric; Bon, Cécile; Bost, Charles-André; d'Ovidio, Francesco

2017-06-01

Compared to ecosystem conservation in territorial seas, protecting the open ocean has peculiar geopolitical, economic and scientific challenges. One of the major obstacle is defining the boundary of an open ocean Marine Protected Area (MPA). In contrast to coastal ecosystems, which are mostly constrained by topographic structures fixed in time, the life of marine organisms in the open ocean is entrained by fluid dynamical structures like eddies and fronts, whose lifetime occurs on ecologically-relevant timescales. The position of these highly dynamical structures can vary interannually by hundreds of km, and so too will regions identified as ecologically relevant such as the foraging areas of marine predators. Thus, the expected foraging locations suggested from tracking data cannot be directly extrapolated beyond the year in which the data were collected. Here we explore the potential of Lagrangian methods applied to multisatellite data as a support tool for a MPA proposal by focusing on the Crozet archipelago oceanic area (Indian Sector of the Southern Ocean). By combining remote sensing with biologging information from a key marine top predator (Eudyptes chrysolophus, or Macaroni penguin) of the Southern Ocean foodweb, we identify a highly dynamic branch of the Subantarctic front as a foraging hotspot. By tracking this feature in historical satellite data (1993-2012) we are able to extrapolate the position of this foraging ground beyond the years in which tracking data are available and study its spatial variability.

Spatially Explicit Models of Carbon and Alkalinity Cycling in the Coastal Oceans

NASA Astrophysics Data System (ADS)

O'Mara, N. A.; Dunne, J. P.

2016-12-01

Calcium carbonate (CaCO3) production, dissolution, and preservation are strongly influenced by seawater temperature and carbon chemistry and thus play a key role in the global carbon cycle and are highly susceptible to influence by climate change. Coastal and continental shelf (neritic) environments have been estimated to account for more than half of all CaCO3 accumulation in ocean sediment globally. Unfortunately, current neritic CaCO3 budgets are muddled with assumptions of the spatial extent of various communities, rely on long term averages rather than deterministic relationships for production rates, and therefore have little predictive power for quantifying the impact of climate change on this system. Current biogeochemical components of globally coupled earth system models include open ocean pelagic CaCO3 production and deep sea preservation (0.130 PgC yr-1), but do not resolve nearshore pelagic or benthic production. Here, a 1° spatially explicit model for determining CaCO3 accumulation in neritic sediments is developed. Globally gridded observational, satellite, and benthic community area data are used to calculate rates of benthic and pelagic community CaCO3 production and preservation using a set of equations sensitive to temperature, carbonate saturation state, light availability, and nutrients. Accumulation rates (PgC yr-1) of four neritic zone environments are calculated: coral reefs and banks (0.075), seagrass dominated embayments (0.043), carbonate rich shelves (0.042), and carbonate poor shelves (0.0007). This analysis corroborates previous budget predictions of total neritic CaCO3 accumulation (0.160) and additionally supports the hypothesis that benthic CaCO3 production (0.151) in coastal water greatly exceeds pelagic production (0.009). However, results additionally suggest that erroneous assumptions about spatial extent of neritic communities have led to overestimations of coral reef and under estimations of embayment accumulation rates in the past.

Effect of atmospheric organic complexation on iron-bearing dust solubility

NASA Astrophysics Data System (ADS)

Paris, R.; Desboeufs, K. V.

2013-02-01

Recent studies reported that the effect of organic complexation may be a potentially important process to be considered in models to estimate atmospheric iron flux to the ocean. In this study, we investigated this effect by a series of dissolution experiments on iron-bearing dust in presence or absence of various organic compounds typically found in the atmospheric waters (acetate, formate, oxalate, malonate, succinate, glutarate, glycolate, lactate, tartrate and humic acid as an analogue of humic like substances (HULIS)). Only 4 of tested organic ligands (oxalate, malonate, tartrate and humic acid) caused an enhancement of iron solubility which was associated with an increase of dissolved Fe(II) concentrations. For all of these organic ligands, a positive linear dependence of iron solubility to organic concentrations was observed and showed that the extent of organic complexation on iron solubility decreased in order oxalate > malonate = tartrate > humic acid. This was attributed to the ability of electron donors of organic ligands and implied a reductive ligand-promoted dissolution. This study confirmed that oxalate is the most effective ligand playing on dust iron solubility and showed, for the first time, the potential effect of HULIS on iron dissolution in atmospheric conditions.

The effect of CO2-fluid-rock interactions on the porosity and permeability of calcite-bearing sandstone

NASA Astrophysics Data System (ADS)

Lamy-Chappuis, B.; Yardley, B.; Grattoni, C.

2013-12-01

Brine acidification following CO2 dissolution will initiate fluid-rock interactions that could significantly modify porosity, permeability and therefore the capacity and injectivity of a reservoir. We have investigated experimentally the dissolution of calcite in sandstone cores injected with CO2-saturated brine, and the effect this has on permeability. A series of CT (Computerized Tomography) - monitored experiments were conducted on a Jurassic sandstone (porosity = 30%, permeability = 10mD, calcite content = 5% in the form of dispersed shell fragments). Brine saturated with CO2 at pressures up to 1 MPa was injected into 5cm long, 3.75cm diameter cores at a flow rate of 1 ml/min and room temperature. The data showed quasi-instantaneous dissolution of the calcite even at low CO2 concentrations (0.15 Molar) and high fluid interstitial velocities (1mm/s), with the migration of a calcite dissolution front through the core recorded by successive CT scans. The resulting permeability increase was 60 - 80% whereas the predicted permeability change for the observed increase in porosity is only 10 - 20% using the Kozeny-Carman relationship. This result is particularly significant because the effect of porosity increase on permeability is usually modelled with this relationship, irrespective of the mechanism of porosity increase. Micro-CT scans (pixel resolution: 2.5 microns) of unreacted cores were used to generate 3D porosity models with calcite either treated as solid (pre-reaction model) or converted to pores (post-reaction model). FLUENT simulations performed using these models predicted the observed large relative changes in permeability with calcite dissolution but overestimated absolute permeability by an order of magnitude. This was probably due to the scan resolution being too coarse to correctly model pore throats. The observed large change in permeability for a small change in porosity may have resulted from increase in connectivity, focused dissolution at the pore throats or reduction in tortuosity. SEM (Scanning Electron Microscope) imaging demonstrates dissolution of relatively large isolated shell fragments but this had little effect on the overall connectivity. No calcite cement was observed at the pore throats in the unreacted specimens. The micro-CT scans indicate a modest tortuosity decrease from 2.00 to 1.85 when calcite is dissolved, but this change in tortuosity results from the opening of new flow paths as the dissolution of discrete grains opened new flow paths and created shortcuts, not from changes to the sinuosity of existing pathways. We suggest that the marked discrepancy in the effect of calcite dissolution on permeability between our experimental data and standard models arises because of the very different way in which the porosity is increased (new pathways rather than inflation). While our results cast doubt on the general applicability of standard models for porosity-permeability relationships for situations in which porosity changes by grain-specific reactions, it is encouraging that pore scale modelling is able to reproduce the experimental relationships.

Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts.

PubMed

Bengtson, S; Ivarsson, M; Astolfo, A; Belivanova, V; Broman, C; Marone, F; Stampanoni, M

2014-11-01

The deep biosphere of the subseafloor crust is believed to contain a significant part of Earth's biomass, but because of the difficulties of directly observing the living organisms, its composition and ecology are poorly known. We report here a consortium of fossilized prokaryotic and eukaryotic micro-organisms, occupying cavities in deep-drilled vesicular basalt from the Emperor Seamounts, Pacific Ocean, 67.5 m below seafloor (mbsf). Fungal hyphae provide the framework on which prokaryote-like organisms are suspended like cobwebs and iron-oxidizing bacteria form microstromatolites (Frutexites). The spatial inter-relationships show that the organisms were living at the same time in an integrated fashion, suggesting symbiotic interdependence. The community is contemporaneous with secondary mineralizations of calcite partly filling the cavities. The fungal hyphae frequently extend into the calcite, indicating that they were able to bore into the substrate through mineral dissolution. A symbiotic relationship with chemoautotrophs, as inferred for the observed consortium, may be a pre-requisite for the eukaryotic colonization of crustal rocks. Fossils thus open a window to the extant as well as the ancient deep biosphere. © 2014 The Authors. Geobiology Published by John Wiley & Sons Ltd.

Physiological advantages of dwarfing in surviving extinctions in high-CO2 oceans

NASA Astrophysics Data System (ADS)

Garilli, Vittorio; Rodolfo-Metalpa, Riccardo; Scuderi, Danilo; Brusca, Lorenzo; Parrinello, Daniela; Rastrick, Samuel P. S.; Foggo, Andy; Twitchett, Richard J.; Hall-Spencer, Jason M.; Milazzo, Marco

2015-07-01

Excessive CO2 in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future, mirroring effects in many past mass extinctions. Fossil records demonstrate that organisms surviving such events were often smaller than those before, a phenomenon called the Lilliput effect. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partially repair shell dissolution. These observations of the long-term chronic effects of increased CO2 levels forewarn of changes we can expect in marine ecosystems as CO2 emissions continue to rise unchecked, and support the hypothesis that ocean acidification contributed to past extinction events. The ability to adapt through dwarfing can confer physiological advantages as the rate of CO2 emissions continues to increase.

Deep water dissolution in Marine Isotope Stage 3 from the northern South China Sea

NASA Astrophysics Data System (ADS)

Huang, B.

2015-12-01

The production, transport, deposition, and dissolution of carbonate profoundly implicate the global carbon cycle affect the inventory and distribution of dissolved organic carbon (DIC) and alkalinity (ALK), which drive atmospheric CO2 change on glacial-interglacial timescale. the process may provide significant clues for improved understanding of the mechanisms that control the global climate system. In this study, we calculate and analyze the foraminiferal dissolution index (FDX) and the fragmentation ratios of planktonic foraminifera over 60-25 ka based on samples from 17924 and ODP 1144 in the northeastern South China Sea (SCS) to reconstruct the deep water carbonate dissolution during Marine Isotope Stage 3 (MIS 3). Result shows that the dissolution of carbonate increases gradually at 17924 but keeps stable at ODP 1144. The changes of FDX coincidence with that of fragmentation ratios at 17924 and ODP 1144 suggest both indexes can be used as reliable dissolving proxies of planktonic foraminifera. Comparing FDX and fragmentation ratios at both sites, we find the FDX and fragmentation ratios at 17924 are higher than those at 1144, indicating that carbonate dissolution is intenser in 17924 core during MIS 3. The increasing total percentage of both N. dutertrei and G. bulloides during MIS 3 reveals the rising primary productivity that may lead to deep water [CO32-] decrease. The slow down of thermohaline circulation may increase deep water residence time and accelerate carbonate dissolution. In addition, the covering of ice caps, iron supply and increased surface-water stratification also contribute to atmosphere CO2 depletion and [CO32-] decrease in deep water. In the meanwhile, regression result from colder temperature increases the input of ALK and DIC to the deep ocean and deepens the carbonate saturation depth, which makes the deep water [CO32-] rise. In ODP Site 1144, the decrease in [CO32-] caused by more CO2 restored in deep water is equal to the increase in [CO32-] because of regression, so dissolution keeps steady. However, [CO32-] is probably more strongly controlled by regression, the decrease in [CO32-] result from more CO2 restored in deep water overwhelms the increase in [CO32-] due to regression at 17924, so more carbonate dissolved from MIS 3 to the Last Glacial Maximum (LGM).

Global declines in oceanic nitrification rates as a consequence of ocean acidification

PubMed Central

Beman, J. Michael; Chow, Cheryl-Emiliane; King, Andrew L.; Feng, Yuanyuan; Fuhrman, Jed A.; Andersson, Andreas; Bates, Nicholas R.; Popp, Brian N.; Hutchins, David A.

2011-01-01

Ocean acidification produced by dissolution of anthropogenic carbon dioxide (CO2) emissions in seawater has profound consequences for marine ecology and biogeochemistry. The oceans have absorbed one-third of CO2 emissions over the past two centuries, altering ocean chemistry, reducing seawater pH, and affecting marine animals and phytoplankton in multiple ways. Microbially mediated ocean biogeochemical processes will be pivotal in determining how the earth system responds to global environmental change; however, how they may be altered by ocean acidification is largely unknown. We show here that microbial nitrification rates decreased in every instance when pH was experimentally reduced (by 0.05–0.14) at multiple locations in the Atlantic and Pacific Oceans. Nitrification is a central process in the nitrogen cycle that produces both the greenhouse gas nitrous oxide and oxidized forms of nitrogen used by phytoplankton and other microorganisms in the sea; at the Bermuda Atlantic Time Series and Hawaii Ocean Time-series sites, experimental acidification decreased ammonia oxidation rates by 38% and 36%. Ammonia oxidation rates were also strongly and inversely correlated with pH along a gradient produced in the oligotrophic Sargasso Sea (r2 = 0.87, P < 0.05). Across all experiments, rates declined by 8–38% in low pH treatments, and the greatest absolute decrease occurred where rates were highest off the California coast. Collectively our results suggest that ocean acidification could reduce nitrification rates by 3–44% within the next few decades, affecting oceanic nitrous oxide production, reducing supplies of oxidized nitrogen in the upper layers of the ocean, and fundamentally altering nitrogen cycling in the sea. PMID:21173255

Fixed point Open Ocean Observatory network (FixO3): Multidisciplinary observations from the air-sea interface to the deep seafloor

NASA Astrophysics Data System (ADS)

Lampitt, Richard; Cristini, Luisa

2014-05-01

The Fixed point Open Ocean Observatory network (FixO3) seeks to integrate the 23 European open ocean fixed point observatories and to improve access to these key installations for the broader community. These will provide multidisciplinary observations in all parts of the oceans from the air-sea interface to the deep seafloor. Coordinated by the National Oceanography Centre, UK, FixO3 builds on the significant advances achieved through the previous Europe-funded FP7 programmes EuroSITES, ESONET and CARBOOCEAN. Started in September 2013 with a budget of 7 Million Euros over 4 years the project has 29 partners drawn from academia, research institutions and SME's. In addition 12 international experts from a wide range of disciplines comprise an Advisory Board. On behalf of the FixO3 Consortium, we present the programme that will be achieved through the activities of 12 Work Packages: 1. Coordination activities to integrate and harmonise the current procedures and processes. Strong links will be fostered with the wider community across academia, industry, policy and the general public through outreach, knowledge exchange and training. 2. Support actions to offer a) free access to observatory infrastructures to those who do not have such access, and b) free and open data services and products. 3. Joint research activities to innovate and enhance the current capability for multidisciplinary in situ ocean observation. Support actions include Transnational Access (TNA) to FixO3 infrastructure, meaning that European organizations can apply to free-of-charge access to the observatories for research and testing in two international calls during the project lifetime. The first call for TNA opens in summer 2014. More information can be found on FixO3 website (www.fixo3.eu/). Open ocean observation is currently a high priority for European marine and maritime activities. FixO3 will provide important data on environmental products and services to address the Marine Strategy Framework Directive and in support of the European Integrated Maritime Policy. The FixO3 network will provide free and open access to in situ fixed point data of the highest quality. It will provide a strong integrated framework of open ocean facilities in the Atlantic from the Arctic to the Antarctic and throughout the Mediterranean, enabling an integrated, regional and multidisciplinary approach to understand natural and anthropogenic change in the ocean.

Effects of pretreatment processes for Zr electrorefining of oxidized Zircaloy-4 cladding tubes

NASA Astrophysics Data System (ADS)

Hwa Lee, Chang; Lee, Yoo Lee; Jeon, Min Ku; Choi, Yong Taek; Kang, Kweon Ho; Park, Geun Il

2014-06-01

The effect of pretreatment processes for the Zr electrorefining of oxidized Zircaloy-4 cladding tubes is examined in LiCl-KCl-ZrCl4 molten salts at 500 °C. The cyclic voltammetries reveal that the Zr dissolution kinetics is highly dependent on the thickness of a Zr oxide layer formed at 500 °C under air atmosphere. For the Zircaloy-4 tube covered with a 1 μm thick oxide layer, the Zr dissolution process is initiated from a non-stoichiometric Zr oxide surface through salt treatment at an open circuit potential in the molten salt electrolyte. The Zr dissolution of the samples in the middle range of oxide layer thickness appears to be more effectively derived by the salt treatment coupled with an anodic potential application at an oxidation potential of Zr. A modification of the process scheme offers an applicability of Zr electrorefining for the treatment of oxidized cladding hull wastes.

Understanding cellulose dissolution: energetics of interactions of ionic liquids and cellobiose revealed by solution microcalorimetry.

PubMed

de Oliveira, Heitor Fernando Nunes; Rinaldi, Roberto

2015-05-11

In this report, the interactions between fifteen selected ionic liquids (ILs) and cellobiose (CB) are examined by high-precision solution microcalorimetry. The heat of mixing (Δmix H) of CB and ILs, or CB and IL/molecular solvent (MS) solutions, provides the first ever-published measure of the affinity of CB with ILs. Most importantly, we found that there is a very good correlation between the nature of the results found for Δmix H(CB) and the solubility behavior of cellulose. This correlation suggests that Δmix H(CB) offers a good estimate of the enthalpy of dissolution of cellulose even in solvents in which cellulose is insoluble. Therefore, the current findings open up new horizons for unravelling the intricacies of the thermodynamic factors accounting for the spontaneity of cellulose dissolution in ILs or IL/MS solutions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quaternary paleoceanography of the central Arctic based on Integrated Ocean Drilling Program Arctic Coring Expedition 302 foraminiferal assemblages

USGS Publications Warehouse

Cronin, T. M.; Smith, S.A.; Eynaud, F.; O'Regan, M.; King, J.

2008-01-01

The Integrated Ocean Drilling Program (IODP) Arctic Coring Expedition (ACEX) Hole 4C from the Lomonosov Ridge in the central Arctic Ocean recovered a continuous 18 in record of Quaternary foraminifera yielding evidence for seasonally ice-free interglacials during the Matuyama, progressive development of large glacials during the mid-Pleistocene transition (MPT) ???1.2-0.9 Ma, and the onset of high-amplitude 100-ka orbital cycles ???500 ka. Foraminiferal preservation in sediments from the Arctic is influenced by primary (sea ice, organic input, and other environmental conditions) and secondary factors (syndepositional, long-term pore water dissolution). Taking these into account, the ACEX 4C record shows distinct maxima in agglutinated foraminiferal abundance corresponding to several interglacials and deglacials between marine isotope stages (MIS) 13-37, and although less precise dating is available for older sediments, these trends appear to continue through the Matuyama. The MPT is characterized by nearly barren intervals during major glacials (MIS 12, 16, and 22-24) and faunal turnover (MIS 12-24). Abundant calcareous planktonic (mainly Neogloboquadrina pachyderma sin.) and benthic foraminifers occur mainly in interglacial intervals during the Brunhes and very rarely in the Matuyama. A distinct faunal transition from calcareous to agglutinated foraminifers 200-300 ka in ACEX 4C is comparable to that found in Arctic sediments from the Lomonosov, Alpha, and Northwind ridges and the Morris Jesup Rise. Down-core disappearance of calcareous taxa is probably related to either reduced sea ice cover prior to the last few 100-ka cycles, pore water dissolution, or both. Copyright 2008 by the American Geophysical Union.

Ocean acidification does not affect magnesium composition or dolomite formation in living crustose coralline algae, Porolithon onkodes in an experimental system

NASA Astrophysics Data System (ADS)

Nash, M. C.; Uthicke, S.; Negri, A. P.; Cantin, N. E.

2015-09-01

There are concerns that Mg-calcite crustose coralline algae (CCA), which are key reef builders on coral reefs, will be most susceptible to increased rates of dissolution under higher pCO2 and ocean acidification. Due to the higher solubility of Mg-calcite, it has been hypothesised that magnesium concentrations in CCA Mg-calcite will decrease as the ocean acidifies, and that this decrease will make their skeletons more chemically stable. In addition to Mg-calcite, CCA Porolithon onkodes, the predominant encrusting species on tropical reefs, can have dolomite (Ca0.5Mg0.5CO3) infilling cell spaces which increases their stability. However, nothing is known about how bio-mineralised dolomite formation responds to higher pCO2. Using P. onkodes grown for 3 and 6 months in tank experiments, we aimed to determine (1) if mol % MgCO3 in new crust and new settlement was affected by increasing CO2 levels (365, 444, 676 and 904 μatm), (2) whether bio-mineralised dolomite formed within these time frames, and (3) if so, whether this was effected by CO2. Our results show that there was no significant effect of CO2 on mol % MgCO3 in any sample set, indicating an absence of a plastic response under a wide range of experimental conditions. Dolomite within the CCA cells formed within 3 months and dolomite abundance did not vary significantly with CO2 treatment. While evidence mounts that climate change will impact many sensitive coral and CCA species, the results from this study indicate that reef-building P. onkodes will continue to form stabilising dolomite infill under near-future acidification conditions, thereby retaining its higher resistance to dissolution.

Ocean acidification does not affect magnesium composition or dolomite formation in living crustose coralline algae, Porolithon onkodes in an experimental system

NASA Astrophysics Data System (ADS)

Nash, M. C.; Uthicke, S.; Negri, A. P.; Cantin, N. E.

2015-01-01

There are concerns that Mg-calcite crustose coralline algae (CCA), which are key reef builders on coral reefs, will be most susceptible to increased rates of dissolution under higher pCO2 and ocean acidification. Due to the higher solubility of Mg-calcite, it has been hypothesized that magnesium concentrations in CCA Mg-calcite will decrease as the ocean acidifies, and that this decrease will make their skeletons more chemically stable. In addition to Mg-calcite, CCA Porolithon onkodes the predominant encrusting species on tropical reefs, can have dolomite (Ca0.5Mg0.5CO3) infilling cell spaces which increases their stability. However, nothing is known about how bio-mineralised dolomite formation responds to higher pCO2. Using P. onkodes grown for 3 and 6 months in tank experiments, we aimed to determine (1) if mol % MgCO3 in new crust and new settlement affected by increasing pCO2 levels (365, 444, 676 and 904 ppm), (2) whether bio-mineralised dolomite formed within these time frames, and (3) if so, whether this was effected by pCO2. Our results show there was no significant effect of pCO2 on mol % MgCO3 in any sample set, indicating an absence of a plastic response under a wide range of experimental conditions. Dolomite within the CCA cells formed within 3 months and dolomite abundance did not vary significantly with pCO2 treatment. While evidence mounts that climate change will impact many sensitive coral and CCA species, the results from this study indicate that reef-building P. onkodes will continue to form stabilising dolomite infill under near-future acidification conditions, thereby retaining its higher resistance to dissolution.

Measuring coral calcification under ocean acidification: methodological considerations for the 45Ca-uptake and total alkalinity anomaly technique

PubMed Central

Krueger, Thomas; Fine, Maoz

2017-01-01

As the oceans become less alkaline due to rising CO2 levels, deleterious consequences are expected for calcifying corals. Predicting how coral calcification will be affected by on-going ocean acidification (OA) requires an accurate assessment of CaCO3 deposition and an understanding of the relative importance that decreasing calcification and/or increasing dissolution play for the overall calcification budget of individual corals. Here, we assessed the compatibility of the 45Ca-uptake and total alkalinity (TA) anomaly techniques as measures of gross and net calcification (GC, NC), respectively, to determine coral calcification at pHT 8.1 and 7.5. Considering the differing buffering capacity of seawater at both pH values, we were also interested in how strongly coral calcification alters the seawater carbonate chemistry under prolonged incubation in sealed chambers, potentially interfering with physiological functioning. Our data indicate that NC estimates by TA are erroneously ∼5% and ∼21% higher than GC estimates from 45Ca for ambient and reduced pH, respectively. Considering also previous data, we show that the consistent discrepancy between both techniques across studies is not constant, but largely depends on the absolute value of CaCO3 deposition. Deriving rates of coral dissolution from the difference between NC and GC was not possible and we advocate a more direct approach for the future by simultaneously measuring skeletal calcium influx and efflux. Substantial changes in carbonate system parameters for incubation times beyond two hours in our experiment demonstrate the necessity to test and optimize experimental incubation setups when measuring coral calcification in closed systems, especially under OA conditions. PMID:28879064

Development of near zero-order release dosage forms using three-dimensional printing (3-DP) technology.

PubMed

Wang, Chen-Chao; Tejwani Motwani, Monica R; Roach, Willie J; Kay, Jennifer L; Yoo, Jaedeok; Surprenant, Henry L; Monkhouse, Donald C; Pryor, Timothy J

2006-03-01

Three near zero-order controlled-release pseudoephedrine hydrochloride (PEH) formulations demonstrating proportional release rates were developed using 3-Dimensional Printing (3-DP) technology. Mixtures of Kollidon SR and hydroxypropylmethyl cellulose (HPMC) were used as drug carriers. The release rates were adjusted by varying the Kollidon SR-HPMC ratio while keeping fabrication parameters constant. The dosage forms were composed of an immediate release core and a release rate regulating shell, fabricated with an aqueous PEH and an ethanolic triethyl citrate (TEC) binder, respectively. The dosage form design called for the drug to be released via diffusional pathways formed by HPMC in the shell matrix. The release rate was shown to increase correspondingly with the fraction of HPMC contained in the polymer blend. The designed formulations resulted in dosage forms that were insensitive to changes in pH of the dissolution medium, paddle stirring rate, and the presence/absence of a sinker. The near zero-order release properties were unchanged regardless of the dissolution test being performed on either single cubes or on a group of eight cubes encased within a gelatin capsule shell. The chemical and dissolution properties of the three formulations remained unchanged following 1 month's exposure to 25 degrees C/60% RH or 40 degrees C/75% RH environment under open container condition. The in vivo performance of the three formulations was evaluated using a single-dose, randomized, open-label, four-way crossover clinical study composed of 10 fasted healthy volunteers. The pharmacokinetic parameters were analyzed using a noncompartmental model. Qualitative rank order linear correlations between in vivo absorption profiles and in vitro dissolution parameters (with slope and intercept close to unity and origin, respectively) were obtained for all three formulations, indicating good support for a Level A in vivo/in vitro correlation.

On the exfoliating polymeric cellular dosage forms for immediate drug release.

PubMed

Blaesi, Aron H; Saka, Nannaji

2016-06-01

The most prevalent pharmaceutical dosage forms at present-the oral immediate-release tablets and capsules-are granular solids. Though effective in releasing drug rapidly, development and manufacture of such dosage forms are fraught with difficulties inherent to particulate processing. Predictable dosage form manufacture could be achieved by liquid-based processing, but cast solid dosage forms are not suitable for immediate drug release due to their resistance to fluid percolation. To overcome this limitation, we have recently introduced cellular dosage forms that can be readily prepared from polymeric melts. It has been shown that open-cell structures comprising polyethylene glycol 8000 (PEG 8k) excipient and a drug exfoliate upon immersion in a dissolution medium. The drug is then released rapidly due to the large specific surface area of the exfoliations. In this work, we vary the molecular weight of the PEG excipient and investigate its effect on the drug release kinetics of structures with predominantly open-cell topology. We demonstrate that the exfoliation rate decreases substantially if the excipient molecular weight is increased from 12 to 100kg/mol, which causes the drug dissolution time to increase by more than a factor of ten. A model is then developed to elucidate the exfoliation behavior of cellular structures. Diverse transport processes are considered: percolation due to capillarity, diffusion of dissolution medium through the cell walls, and viscous flow of the saturated excipient. It is found that the lower exfoliation rate and the longer dissolution time of the dosage forms with higher excipient molecular weight are primarily due to the greater viscosity of the cell walls after fluid penetration. Copyright © 2016 Elsevier B.V. All rights reserved.

76 FR 65183 - National Oceanic and Atmospheric Administration

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-20

... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Climate Assessment... Oceanic and Atmospheric Administration (NOAA), Department of Commerce (DOC). ACTION: Notice of open..., National Oceanic and Atmospheric Administration. [FR Doc. 2011-27113 Filed 10-19-11; 8:45 am] BILLING CODE...

Response of acid mobilization of iron-containing mineral dust to improvement of air quality projected in the future

NASA Astrophysics Data System (ADS)

Ito, A.; Xu, L.

2014-04-01

Acidification of dust aerosols may increase aerosol iron (Fe) solubility, which is linked to mineral properties. Combustion aerosols can also elevate aerosol iron solubility when aerosol loading is low. Here, we use an atmospheric chemical transport model to investigate the deposition of filterable iron and its response to changes in anthropogenic emissions of both combustion aerosols and precursor gases. By introducing three classes of iron-containing minerals into the detailed aerosol chemistry model, we provide a theoretical examination of the effects of different dissolution behaviors on the acid mobilization of iron. Comparisons of modeled Fe dissolution curves with the measured dissolution rates for African, east Asian, and Australian dust samples show overall good agreement under acidic conditions. The improved treatment of Fe in mineral dust and its dissolution scheme results in reasonable predictive capability for iron solubility over the oceans in the Northern Hemisphere. Our model results suggest that the improvement of air quality projected in the future will lead to a decrease of the filterable iron deposition from iron-containing mineral dust to the eastern North Pacific due to less acidification in Asian dust, which is mainly associated with the reduction of nitrogen oxides (NOx) emissions. These results could have important implications for iron fertilization of phytoplankton growth, and highlight the necessity of improving the process-based quantitative understanding of the response of the chemical modification in iron-containing minerals to environmental changes.

Rapid releases of metal salts and nutrients following the deposition of volcanic ash into aqueous environments

NASA Astrophysics Data System (ADS)

Jones, Morgan T.; Gislason, Sigurður R.

2008-08-01

Deposition of volcanic ash into aqueous environments leads to dissolution of adsorbed metal salts and aerosols, increasing the bioavailability of key nutrients. Volcanogenic fertilization events could increase marine primary productivity, leading to a drawdown of atmospheric CO 2. Here we conduct flow-through experiments on unhydrated volcanic ash samples from a variety of locations and sources, measuring the concentrations and fluxes of elements into de-ionized water and two contrasting ocean surface waters. Comparisons of element fluxes show that dissolution of adsorbed surface salts and aerosols dominates over glass dissolution, even in sustained low pH conditions. These surface ash-leachates appear unstable, decaying in situ even if kept unhydrated. Volcanic ash from recent eruptions is shown to have a large fertilization potential in both fresh and saline water. Fluorine concentrations are integral to bulk dissolution rates and samples with high F concentrations display elevated fluxes of some nutrients, particularly Fe, Si, and P. Bio-limiting micronutrients are released in large quantities, suggesting that subsequent biological growth will be limited by macronutrient availability. Importantly, acidification of surface waters and high fluxes of toxic elements highlights the potential of volcanic ash-leachates to poison aqueous environments. In particular, large pH changes can cause undersaturation of CaCO 3 polymorphs, damaging populations of calcifying organisms. Deposition of volcanic ash can both fertilize and/or poison aqueous environments, causing significant changes to surface water chemistry and biogeochemical cycles.

Dissolution-Assisted Pattern Formation During Olivine Carbonation

NASA Astrophysics Data System (ADS)

Lisabeth, Harrison; Zhu, Wenlu; Xing, Tiange; De Andrade, Vincent

2017-10-01

Olivine and pyroxene-bearing rocks in the oceanic crust react with hydrothermal fluids producing changes in the physical characteristics and behaviors of the altered rocks. Notably, these reactions tend to increase solid volume, reducing pore volume, permeability, and available reactive surface area, yet entirely hydrated and/or carbonated rocks are commonly observed in the field. We investigate the evolution of porosity and permeability of fractured dunites reacted with CO2-rich solutions in laboratory experiments. The alteration of crack surfaces changes the mechanical and transport properties of the bulk samples. Analysis of three-dimensional microstructural data shows that although precipitation of secondary minerals causes the total porosity of the sample to decrease, an interconnected network of porosity is maintained through channelized dissolution and coupled carbonate precipitation. The observed microstructure appears to be the result of chemo-mechanical coupling, which may provide a mechanism of porosity maintenance without the need to invoke reaction-driven cracking.

Development of Atmospheric Chemistry-Aerosol Transport Model for Bioavailable Iron From Dust and Combustion Source

NASA Astrophysics Data System (ADS)

Ito, A.; Feng, Y.

2009-12-01

An accurate prediction of bioavailable iron fraction for ocean biota is hampered by uncertainties in modeling soluble iron fractions in atmospheric aerosols. It has been proposed that atmospheric processing of mineral aerosols by anthropogenic pollutants may be a key pathway to transform insoluble iron into soluble forms. The dissolution of dust minerals strongly depends on solution pH, which is sensitive to the heterogeneous uptake of soluble gases by the dust particle. Due to the complexity, previous model assessments generally use a common assumption in thermodynamical equilibrium between gas and aerosol phases. Here, we compiled an emission inventory of iron from combustion and dust source, and incorporated a dust iron dissolution scheme in a global chemistry-aerosol transport model (IMPACT). We will examine and discuss the uncertainties in estimation of dissolved iron as well as comparisons of the model results with available observations.

Dissolution-Assisted Pattern Formation During Olivine Carbonation

DOE PAGES

Lisabeth, Harrison; Zhu, Wenlu; Xing, Tiange; ...

2017-08-31

Olivine and pyroxene bearing rocks in the oceanic crust react with hydrothermal fluids producing changes in the physical characteristics and behaviors of the altered rocks. Notably, these reactions tend to increase solid volume, reducing pore volume, permeability and available reactive surface area; yet, entirely hydrated and/or carbonated rocks are commonly observed in the field. We investigate the evolution of porosity and permeability of fractured dunites reacted with CO 2-rich solutions in laboratory experiments. The alteration of crack surfaces changes the mechanical and transport properties of the bulk samples. Analysis of three-dimensional microstructural data shows that although precipitation of secondary mineralsmore » causes the total porosity of the sample to decrease, an interconnected network of porosity is maintained through channelized dissolution and coupled carbonate precipitation. Lastly, the observed microstructure appears to be the result of chemo-mechanical coupling, which may provide a mechanism of porosity maintenance without the need to invoke reaction-driven cracking.« less

Dissolution actuated sample container

DOEpatents

Nance, Thomas A.; McCoy, Frank T.

2013-03-26

A sample collection vial and process of using a vial is provided. The sample collection vial has an opening secured by a dissolvable plug. When dissolved, liquids may enter into the interior of the collection vial passing along one or more edges of a dissolvable blocking member. As the blocking member is dissolved, a spring actuated closure is directed towards the opening of the vial which, when engaged, secures the vial contents against loss or contamination.

Meridional contrasts in productivity changes driven by the Cenozoic opening of Drake Passage

NASA Astrophysics Data System (ADS)

Donnadieu, Y.; Ladant, J. B.; Bopp, L.; Wilson, P. A.; Lear, C. H.

2017-12-01

The progressive opening of Drake Passage across the Eocene and the Oligocene occurs contemporaneously to the long-term global cooling of the late Eocene, which culminated with the Eocene-Oligocene glaciation of Antarctica. Atmospheric pCO2 decline during the late Eocene is thought to have played a major role in the climatic shifts of the Eocene-Oligocene boundary, yet reasons behind CO2 variations remain obscure. Changes in marine productivity affecting the biological oceanic carbon pump represent a possible cause. Here, we explore whether and how the opening of Drake Passage may have affected the marine biogeochemistry, and in particular paleoproductivity changes, with the use of a fully coupled atmosphere-ocean-biogeochemical model (IPSL-CM5A). We find that the simulated changes to Drake Passage opening exhibit a uniform decrease in the low latitudes while the high latitude response is more spatially heterogeneous. Mechanistically, the low latitude productivity decrease is a consequence of the dramatic reorganization of the ocean circulation when Drake Passage opens, as the shift from a well ventilated to a swampier ocean drives nutrient depletion in the low latitudes. In the high latitudes, the onset of the Antarctic Circumpolar Current in the model exerts a strong control both on nutrient availability but also on regions of deep water formation, which results in non-uniform patterns of productivity change in the Southern Ocean. The qualitative agreement between geographically diverse long-term paleoproductivity records and the simulated variations suggests that the opening of Drake Passage may contribute to part of the long-term paleoproductivity signal recorded in the data.

The inverse problem: Ocean tides derived from earth tide observations

NASA Technical Reports Server (NTRS)

Kuo, J. T.

1978-01-01

Indirect mapping ocean tides by means of land and island-based tidal gravity measurements is presented. The inverse scheme of linear programming is used for indirect mapping of ocean tides. Open ocean tides were measured by the numerical integration of Laplace's tidal equations.

Enhanced macroboring and depressed calcification drive net dissolution at high-CO2 coral reefs.

PubMed

Enochs, Ian C; Manzello, Derek P; Kolodziej, Graham; Noonan, Sam H C; Valentino, Lauren; Fabricius, Katharina E

2016-11-16

Ocean acidification (OA) impacts the physiology of diverse marine taxa; among them corals that create complex reef framework structures. Biological processes operating on coral reef frameworks remain largely unknown from naturally high-carbon-dioxide (CO 2 ) ecosystems. For the first time, we independently quantified the response of multiple functional groups instrumental in the construction and erosion of these frameworks (accretion, macroboring, microboring, and grazing) along natural OA gradients. We deployed blocks of dead coral skeleton for roughly 2 years at two reefs in Papua New Guinea, each experiencing volcanically enriched CO 2 , and employed high-resolution micro-computed tomography (micro-CT) to create three-dimensional models of changing skeletal structure. OA conditions were correlated with decreased calcification and increased macroboring, primarily by annelids, representing a group of bioeroders not previously known to respond to OA. Incubation of these blocks, using the alkalinity anomaly methodology, revealed a switch from net calcification to net dissolution at a pH of roughly 7.8, within Intergovernmental Panel on Climate Change's (IPCC) predictions for global ocean waters by the end of the century. Together these data represent the first comprehensive experimental study of bioerosion and calcification from a naturally high-CO 2 reef ecosystem, where the processes of accelerated erosion and depressed calcification have combined to alter the permanence of this essential framework habitat. © 2016 The Authors.

Enhanced macroboring and depressed calcification drive net dissolution at high-CO2 coral reefs

PubMed Central

Manzello, Derek P.; Kolodziej, Graham; Noonan, Sam H. C.; Valentino, Lauren; Fabricius, Katharina E.

2016-01-01

Ocean acidification (OA) impacts the physiology of diverse marine taxa; among them corals that create complex reef framework structures. Biological processes operating on coral reef frameworks remain largely unknown from naturally high-carbon-dioxide (CO2) ecosystems. For the first time, we independently quantified the response of multiple functional groups instrumental in the construction and erosion of these frameworks (accretion, macroboring, microboring, and grazing) along natural OA gradients. We deployed blocks of dead coral skeleton for roughly 2 years at two reefs in Papua New Guinea, each experiencing volcanically enriched CO2, and employed high-resolution micro-computed tomography (micro-CT) to create three-dimensional models of changing skeletal structure. OA conditions were correlated with decreased calcification and increased macroboring, primarily by annelids, representing a group of bioeroders not previously known to respond to OA. Incubation of these blocks, using the alkalinity anomaly methodology, revealed a switch from net calcification to net dissolution at a pH of roughly 7.8, within Intergovernmental Panel on Climate Change's (IPCC) predictions for global ocean waters by the end of the century. Together these data represent the first comprehensive experimental study of bioerosion and calcification from a naturally high-CO2 reef ecosystem, where the processes of accelerated erosion and depressed calcification have combined to alter the permanence of this essential framework habitat. PMID:27852802

Possible atmospheric lifetimes and chemical reaction mechanisms for selected HCFCs, HFCs, CH3CCl3, and their degradation products against dissolution and/or degradation in seawater and cloudwater

NASA Technical Reports Server (NTRS)

Wine, P. H.; Chameides, W. L.

1990-01-01

For a wide variety of atmospheric species including CO2, HNO3, and SO2, dissolution in seawater or cloudwater followed by hydrolysis or chemical reaction represents a primary pathway for removal from the atmosphere. In order to determine if this mechanism can also remove significant amounts of atmospheric chlorofluorocarbons (HCFC's), fluorocarbons (HFC's), and their degradation products, an investigation was undertaken as part of the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS). In this investigation, the rates at which CHCl2CF3 (HCFC-123), CCl2FCH3 (HCFC-141b), CClF2CH3 (HCFC-142b), CHClF2 (HCFC-22), CHClFCF3 (HCFC-124) CH2FCF3 (HFC-134a) CHF2CH3 (HFC-152a), CHF2CF3 (HFC-125), and CH3CCl3 can be dissolved in the oceans and in cloudwater were estimated from the species' thermodynamic and chemical properties using simple mathematical formulations to simulate the transfer of gases from the atmosphere to the ocean or cloudwater. The ability of cloudwater and rainwater to remove gas phase degradation products of these compounds was also considered as was the aqueous phase chemistry of the degradation products. The results of this investigation are described.

Impacts of Near-Future Ocean Acidification and Warming on the Shell Mechanical and Geochemical Properties of Gastropods from Intertidal to Subtidal Zones.

PubMed

Leung, Jonathan Y S; Connell, Sean D; Nagelkerken, Ivan; Russell, Bayden D

2017-11-07

Many marine organisms produce calcareous shells as the key structure for defense, but the functionality of shells may be compromised by ocean acidification and warming. Nevertheless, calcifying organisms may adaptively modify their shell properties in response to these impacts. Here, we examined how reduced pH and elevated temperature affect shell mechanical and geochemical properties of common grazing gastropods from intertidal to subtidal zones. Given the greater environmental fluctuations in the intertidal zone, we hypothesized that intertidal gastropods would exhibit more plastic responses in shell properties than subtidal gastropods. Overall, three out of five subtidal gastropods produced softer shells at elevated temperature, while intertidal gastropods maintained their shell hardness at both elevated pCO 2 (i.e., reduced pH) and temperature. Regardless of pH and temperature, degree of crystallization was maintained (except one subtidal gastropod) and carbonate polymorph remained unchanged in all tested species. One intertidal gastropod produced less soluble shells (e.g., higher calcite/aragonite) in response to reduced pH. In contrast, subtidal gastropods produced only aragonite which has higher solubility than calcite. Overall, subtidal gastropods are expected to be more susceptible than intertidal gastropods to shell dissolution and physical damage under future seawater conditions. The increased vulnerability to shell dissolution and predation could have serious repercussions for their survival and ecological contributions in the future subtidal environment.

Ocean acidification and temperature increase impact mussel shell shape and thickness: problematic for protection?

PubMed

Fitzer, Susan C; Vittert, Liberty; Bowman, Adrian; Kamenos, Nicholas A; Phoenix, Vernon R; Cusack, Maggie

2015-11-01

Ocean acidification threatens organisms that produce calcium carbonate shells by potentially generating an under-saturated carbonate environment. Resultant reduced calcification and growth, and subsequent dissolution of exoskeletons, would raise concerns over the ability of the shell to provide protection for the marine organism under ocean acidification and increased temperatures. We examined the impact of combined ocean acidification and temperature increase on shell formation of the economically important edible mussel Mytilus edulis. Shell growth and thickness along with a shell thickness index and shape analysis were determined. The ability of M. edulis to produce a functional protective shell after 9 months of experimental culture under ocean acidification and increasing temperatures (380, 550, 750, 1000 μatm pCO 2, and 750, 1000 μatm pCO 2 + 2°C) was assessed. Mussel shells grown under ocean acidification conditions displayed significant reductions in shell aragonite thickness, shell thickness index, and changes to shell shape (750, 1000 μatm pCO 2) compared to those shells grown under ambient conditions (380 μatm pCO 2). Ocean acidification resulted in rounder, flatter mussel shells with thinner aragonite layers likely to be more vulnerable to fracture under changing environments and predation. The changes in shape presented here could present a compensatory mechanism to enhance protection against predators and changing environments under ocean acidification when mussels are unable to grow thicker shells. Here, we present the first assessment of mussel shell shape to determine implications for functional protection under ocean acidification.

Dissolution Processes at Step Edges of Calcite in Water Investigated by High-Speed Frequency Modulation Atomic Force Microscopy and Simulation.

PubMed

Miyata, Kazuki; Tracey, John; Miyazawa, Keisuke; Haapasilta, Ville; Spijker, Peter; Kawagoe, Yuta; Foster, Adam S; Tsukamoto, Katsuo; Fukuma, Takeshi

2017-07-12

The microscopic understanding of the crystal growth and dissolution processes have been greatly advanced by the direct imaging of nanoscale step flows by atomic force microscopy (AFM), optical interferometry, and X-ray microscopy. However, one of the most fundamental events that govern their kinetics, namely, atomistic events at the step edges, have not been well understood. In this study, we have developed high-speed frequency modulation AFM (FM-AFM) and enabled true atomic-resolution imaging in liquid at ∼1 s/frame, which is ∼50 times faster than the conventional FM-AFM. With the developed AFM, we have directly imaged subnanometer-scale surface structures around the moving step edges of calcite during its dissolution in water. The obtained images reveal that the transition region with typical width of a few nanometers is formed along the step edges. Building upon insight in previous studies, our simulations suggest that the transition region is most likely to be a Ca(OH) 2 monolayer formed as an intermediate state in the dissolution process. On the basis of this finding, we improve our understanding of the atomistic dissolution model of calcite in water. These results open up a wide range of future applications of the high-speed FM-AFM to the studies on various dynamic processes at solid-liquid interfaces with true atomic resolution.

Structures and microfabrics of the Franciscan Complex (California): Inferences on the rheology and kinematics of a subduction channel

NASA Astrophysics Data System (ADS)

Krohe, A.; Wassmann, S.; Trepmann, C.; Stoeckhert, B.

2009-12-01

The characteristic feature of the Franciscan Subduction Complex (FSC) is a chaotic mélange structure with centimeter- to about one kilometer-sized tectonic blocks composed of metabasalts, floating in a matrix of oceanic meta-sediments or, locally, serpentinites. Investigating map scale structures, microfabrics, and P-T-histories of the FSC, we try to gain information on the mechanical properties of rocks and their influence on the kinematics of material transport in a subduction channel. Structures and microfabrics indicate that metabasalts from the oceanic crust as well as mantle-derived ultramafic rocks (i) underwent fragmentation and sealing under high pore fluid pressure, (ii) remaining internally undeformed, or (iii) deform by dissolution precipitation creep. Importantly, microfabrics which would indicate crystal plastic deformation or dislocation creep are systematically absent. This means that, during the entire P-T history, differential stresses generally remained too low to activate crystal plastic deformation or dislocation creep. Hence the material in the subduction channel is characterized by a low strength, being either limited by brittle failure at high pore fluid pressure, or a Newton viscosity, which is expected for dissolution precipitation creep. We interpret the characteristic mélange structure as to reflect this mechanical state of the system: Brittle failure at quasi-lithostatic fluid pressures down to great depths is recorded in the tectonic blocks by the widespread occurrence of aragonite-bearing veins. This leads to fragmentation into the blocks of variable size and moderate aspect ratios, which behave as rigid inclusions in a flowing matrix with distributed deformation by dissolution precipitation creep. In contrast, a power law rheology characteristic for dislocation creep, would favor strain localization into shear zones at sites of stress concentration. However, such shear zones formed at high-P metamorphic conditions are not identified. Mechanical contrasts within the mélange are presumably governed by variations in grain sizes and the nature of interphase boundaries, which both control viscous deformation by dissolution precipitation creep. As such, huge viscosity contrasts between matrix and rigid blocks can persist during burial to HP metamorphic conditions and decompression, while the mélange is deformed to very high bulk strain. These findings pose constraints on the large scale properties of a subduction channel presently active at depth, to be identified by geophysical methods.

Natural variability of pCO2 and pH in the Atlantic and Pacific coastal margins of the U.S

NASA Astrophysics Data System (ADS)

Sutton, A. J.; Sabine, C. L.; Feely, R. A.; Newton, J.; Salisbury, J.; Vandemark, D. C.; Musielewicz, S. B.; Maenner-Jones, S.; Bott, R.; Lawrence-Slavas, N.

2011-12-01

The discovery that seawater chemistry is changing as a result of carbon dioxide (CO2) emissions, referred to as "ocean acidification", has prompted a large effort to understand how this changing chemistry will impact marine life. Changes in carbon chemistry have been documented in the open ocean; however, in dynamic coastal systems where many marine species live, ocean acidification and the natural biogeochemical variability that organisms are currently exposed to are poorly quantified. In 2010 we began equipping coastal moorings currently measuring pCO2 with pH and other biogeochemical sensors to measure ocean acidification parameters at 3 hour intervals in the surface water. Here we present the magnitude and diurnal to seasonal variability of pCO2 and pH during the first year of observations at 2 sites in the Atlantic and Pacific coastal margins of the U.S.: the Gulf of Maine and outer coast of Washington state. Both the magnitude and range of pCO2 and pH values were much greater at the coastal moorings compared to the open ocean mooring at Ocean Station Papa in the North Pacific and also varied between the two coastal mooring sites. We observed maximum pCO2 values in coastal waters exceeding predicted values for the open ocean at 2x pre-industrial CO2 levels. The range of pCO2 and pH values during this time series was approximately 4 times the range observed at open ocean mooring Papa (2007-2011 time series). In many cases, large variance was observed at short time scales, with values fluctuating more than 200 μatm pCO2 and 0.2 pH between 3-hour cycles. These types of observations are critical for understanding how ocean acidification will manifest in naturally dynamic coastal systems and for informing the experimental design of species response studies that aim to mimic carbon chemistry experienced by coastal marine organisms.

Opening Pandora's Box: The impact of open system modeling on interpretations of anoxia

NASA Astrophysics Data System (ADS)

Hotinski, Roberta M.; Kump, Lee R.; Najjar, Raymond G.

2000-06-01

The geologic record preserves evidence that vast regions of ancient oceans were once anoxic, with oxygen levels too low to sustain animal life. Because anoxic conditions have been postulated to foster deposition of petroleum source rocks and have been implicated as a kill mechanism in extinction events, the genesis of such anoxia has been an area of intense study. Most previous models of ocean oxygen cycling proposed, however, have either been qualitative or used closed-system approaches. We reexamine the question of anoxia in open-system box models in order to test the applicability of closed-system results over long timescales and find that open and closed-system modeling results may differ significantly on both short and long timescales. We also compare a scenario with basinwide diffuse upwelling (a three-box model) to a model with upwelling concentrated in the Southern Ocean (a four-box model). While a three-box modeling approach shows that only changes in high-latitude convective mixing rate and character of deepwater sources are likely to cause anoxia, four-box model experiments indicate that slowing of thermohaline circulation, a reduction in wind-driven upwelling, and changes in high-latitude export production may also cause dysoxia or anoxia in part of the deep ocean on long timescales. These results suggest that box models must capture the open-system and vertically stratified nature of the ocean to allow meaningful interpretations of long-lived episodes of anoxia.

Dynamics of carbonate chemistry, production, and calcification of the Florida Reef Tract (2009-2010): Evidence for seasonal dissolution

NASA Astrophysics Data System (ADS)

Muehllehner, Nancy; Langdon, Chris; Venti, Alyson; Kadko, David

2016-05-01

Ocean acidification is projected to lower the Ωar of reefal waters by 0.3-0.4 units by the end of century, making it more difficult for calcifying organisms to secrete calcium carbonate while at the same time making the environment more favorable for abiotic and biotic dissolution of the reefal framework. There is great interest in being able to project the point in time when coral reefs will cross the tipping point between being net depositional to net erosional in terms of their carbonate budgets. Periodic in situ assessments of the balance between carbonate production and dissolution that spans seasonal time scales may prove useful in monitoring and formulating projections of the impact of ocean acidification on reefal carbonate production. This study represents the first broad-scale geochemical survey of the rates of net community production (NCP) and net community calcification (NCC) across the Florida Reef Tract (FRT). Surveys were performed at approximately quarterly intervals in 2009-2010 across seven onshore-offshore transects spanning the upper, middle, and lower Florida Keys. Averaged across the FRT, the rates of NCP and NCC were positive during the spring/summer at 62 ± 7 and 17 ± 2 mmol m-2 d-1, respectively, and negative during the fall/winter at -33 ± 6 and -7 ± 2 mmol m-2 d-1. The most significant finding of the study was that the northernmost reef is already net erosional (-1.1 ± 0.4 kg CaCO3 m-2 yr-1) and midreefs to the south were net depositional on an annual basis (0.4 ± 0.1 kg CaCO3 m-2 yr-1) but erosional during the fall and winter. Only the two southernmost reefs were net depositional year-round. These results indicate that parts of the FRT have already crossed the tipping point for carbonate production and other parts are getting close.

Forward Modeling of Carbonate Proxy Data from Planktonic Foraminifera using Oxygen Isotope Tracers in a Global Ocean Model

NASA Technical Reports Server (NTRS)

Schmidt, Gavin A.

1999-01-01

The distribution and variation of oxygen isotopes in seawater are calculated using the Goddard Institute for Space Studies global ocean model. Simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth, column temperature, season, light intensity, and density stratification. These models are combined to forward model isotopic signals recorded in calcareous ocean sediment. The sensitivity of the results to the changes in foraminiferal ecology, secondary calcification, and dissolution are also examined. Simulated present-day isotopic values for ecology relevant for multiple species compare well with core-top data. Hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes. Paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature, salinity, and delta (sup 18)O(sub w). Habitat-imposed biases are less important, although errors due to temperature-dependent abundances can be significant.

Template occluded SBA-15: An effective dissolution enhancer for poorly water-soluble drug

NASA Astrophysics Data System (ADS)

Tingming, Fu; Liwei, Guo; Kang, Le; Tianyao, Wang; Jin, Lu

2010-09-01

The aim of the present work was to improve the dissolution rate of piroxicam by inclusion into template occluded SBA-15. Our strategy involves directly introducing piroxicam into as-prepared SBA-15 occluded with P123 (EO 20PO 70EO 20) by self assembling method in acetonitrile/methylene chloride mixture solution. Ultraviolet spectrometry experiment and thermogravimetric analysis-differential scanning calorimetry (TG-DSC) profiles show that the piroxicam and P123 contents in the inclusion compound are 12 wt% and 28 wt%, respectively. X-ray powder diffraction and DSC analysis reveal that the included piroxicam is arranged in amorphous form. N 2 adsorption-desorption experiment indicates that the piroxicam has been introduced to the mesopores instead of precipitating at the outside of the silica material. The inclusion compound was submitted to in vitro dissolution tests, the results show that the piroxicam dissolve from template occluded inclusion compound more rapidly, than these from the piroxicam crystalline and template removed samples in all tested conditions. Thus a facile method to improve the dissolution rate of poorly water-soluble drug was established, and this discovery opens a new avenue for the utilization of templates used for the synthesis of mesoporous materials.

Flow microcapillary plasma mass spectrometry-based investigation of new Al-Cr-Fe complex metallic alloy passivation.

PubMed

Ott, N; Beni, A; Ulrich, A; Ludwig, C; Schmutz, P

2014-03-01

Al-Cr-Fe complex metallic alloys are new intermetallic phases with low surface energy, low friction, and high corrosion resistance down to very low pH values (0-2). Flow microcapillary plasma mass spectrometry under potentiostatic control was used to characterize the dynamic aspect of passivation of an Al-Cr-Fe gamma phase in acidic electrolytes, allowing a better insight on the parameters inducing chemical stability at the oxyhydroxide-solution interface. In sulfuric acid pH 0, low element dissolution rates (in the µg cm(-2) range after 60 min) evidenced the passive state of the Al-Cr-Fe gamma phase with a preferential over-stoichiometric dissolution of Al and Fe cations. Longer air-aging was found to be beneficial for stabilizing the passive film. In chloride-containing electrolytes, ten times higher Al dissolution rates were detected at open-circuit potential (OCP), indicating that the spontaneously formed passive film becomes unstable. However, electrochemical polarization at low passive potentials induces electrical field generated oxide film modification, increasing chemical stability at the oxyhydroxide-solution interface. In the high potential passive region, localized attack is initiated with subsequent active metal dissolution. © 2013 Published by Elsevier B.V.

Cloud iron speciation: Experimental simulations

NASA Astrophysics Data System (ADS)

Sofikitis, A. M.; Colin, J. L.; Desboeufs, K. V.; Losno, R.

2003-04-01

The aim of our contribution is to identify major processes controlling iron speciation in the atmospheric aqueous phase. Fe is known to participate in a variety of redox reactions in cloud chemistry, as well as controlling free radical production in the troposphere. Iron cycling is slower than cycles with other catalytic transition metals (Cu, Mn). The residence time of each iron species is around ten minutes, this allows analytical separation and determination of each iron redox species and therefore its ratio. As the only source of trace metals in aqueous atmospheric phase is due to the solubilization of aerosols, we present here dissolution rate measurements obtained by laboratory experiments with an open flow reactor. This reactor enables us to reproduce the dissolution of a particle in aqueous atmospheric water. The dissolution rate and the speciation of iron are dependent on the mineralogy of the solid phase. Our experiments included Goethite, hematite and vermiculite, which are typical mineral constituents of dust particles. Comparisons were made with natural loess which is a blend of various crystalline and amorphous phases. We will present results of crustal origin particles dissolution experiments where kinetic parameters are determined, including iron speciation. Major functions of variation are pH and photochemistry in the aqueous weathering solution.

[Troubleshooting of bioinequivalence of compound valsartan tablets].

PubMed

Shao, Da; Zhang, Yi-Fan; Zhan, Yan; Chen, Xiao-Yan; Zhong, Da-Fang

2014-04-01

The study aims to evaluate the bioequivalence of valsartan hydrochlorothiazide tablets, and to investigate the potential cause of bioinequivalence. This was a single-center study with an open, randomized double-way crossover design. Test and reference preparations containing 160 mg of valsartan and 25 mg of hydrochlorothiazide were given to 36 healthy male volunteers. Plasma concentrations of valsartan and hydrochlorothiazide were determined simultaneously by LC-MS/MS. The pharmacokinetic parameters and relative bioavailability were calculated, while the bioequivalence between test and reference preparations were evaluated. The dissolution profiles of test and reference preparations in four different mediums were determined via dissolution test and HPLC. The similarity was investigated according to the similarity factors (f2). The F(o-t) and F(0-infinity) were (139.4 +/- 65.2)% and (137.5 +/- 61.2)% for valsartan of test preparations. It led to get the conclusion that test and reference preparations were not bioequivalent for valsartan. A significant difference was observed between test and reference tablets in the valsartan dissolution test of pH 1.2 hydrochloric acid solution. The key factor of the bioinequivalence might be that dissolution of valsartan in acid medium has marked difference between two preparations.

76 FR 13999 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

..., and other current issues in the ocean science and management communities; including, the review and... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research and Resources Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research...

76 FR 22083 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-20

... other current issues in the ocean science and management communities; including, the review and... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research and Resources Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research...

Chemical leaching methods and measurements of marine labile particulate Fe

NASA Astrophysics Data System (ADS)

Revels, B. N.; John, S.

2012-12-01

Iron (Fe) is an essential nutrient for life. Yet its low solubility and concentration in the ocean limits marine phytoplankton productivity in many regions of the world. Dissolved phase Fe (<0.4μm) has traditionally been considered the most biologically accessible form, however, the particulate phase (>0.4μm) may contain an important, labile reservoir of Fe that may also be available to phytoplankton. However, concentration data alone cannot elucidate the sources of particulate Fe to the ocean and to what extent particulate iron may support phytoplankton growth. Isotopic analysis of natural particles may help to elucidate the biogeochemical cycling of Fe, though it is important to find a leaching method which accesses bioavailable Fe. Thirty-three different chemical leaches were performed on a marine sediment reference material, MESS-3. The combinations included four different acids (25% acetic acid, 0.01M HCl, 0.5M HCl, 0.1M H2SO4 at pH2), various redox conditions (0.02M hydroxylamine hydrochloride or 0.02M H2O2), three temperatures (25°C, 60°C, 90°C), and three time points (10 minutes, 2 hours, 24 hours). Leached Fe concentrations varied from 1mg/g to 35mg/g, with longer treatment times, stronger acids, and hotter temperatures generally associated with an increase in leached Fe. δ56Fe in these leaches varied from -1.0‰ to +0.2‰. Interestingly, regardless of leaching method used, there was a very similar relationship between the amount of Fe leached from the particles and the δ56Fe of this iron. Isotopically lighter δ56Fe values were associated with smaller amounts of leached Fe whereas isotopically heavier δ56Fe values were associated with larger amounts of leached Fe. Two alternate hypotheses could explain these data. Either, the particles may contain pools of isotopically light Fe that are easily accessed early in dissolution, or isotopically light Fe may be preferentially leached from the particle due to a kinetic isotope effect during dissolution. To explore the first hypothesis, we modeled dissolution of Fe from particles assuming two separate pools, labile and refractory. The model produces a good fit to the data assuming 3mg/g of a labile Fe pool with δ56Fe = -0.9‰ and a refractory Fe pool with δ56Fe = +0.1‰. If the second hypothesis is true, and there is a kinetic isotope effect during dissolution, the similar relationship between amount of Fe leached and δ56Fe for both organic and mineral acids suggests that Fe is leached from particles via proton-promoted dissolution. Several of these leaching techniques will be employed on sediment trap material from the Cariaco Basin to further investigate the relationship between δ56Fe and the labile, bioavailable fraction of iron particles. A leach or series of leaches will be chosen to provide the most useful information about the bioavailability of iron from particles, and they will be applied to filtered particle samples from portions of the US GEOTRACES A10 (North Atlantic) transect. δ56Fe values from particulate material in these regions will provide a better understanding of the sources of particulate iron to the ocean, and may help to trace how particulate iron is involved in global biogeochemical cycles.

Increase of apatite dissolution rate by Scots pine roots associated or not with Burkholderia glathei PML1(12)Rp in open-system flow microcosms

NASA Astrophysics Data System (ADS)

Calvaruso, Christophe; Turpault, Marie-Pierre; Frey-Klett, Pascale; Uroz, Stéphane; Pierret, Marie-Claire; Tosheva, Zornitza; Kies, Antoine

2013-04-01

The release of nutritive elements through apatite dissolution represents the main source of phosphorus, calcium, and several micronutrients (e.g., Zn, Cu) for organisms in non-fertilized forest ecosystems. The aim of this study was to quantify, for the first time, the dissolution rate of apatite grains by tree roots that were or were not associated with a mineral weathering bacterial strain, and by various acids known to be produced by tree roots and soil bacterial strains in open-system flow microcosms. In addition, we explored whether the mobilization of trace elements (including rare earth elements) upon apatite dissolution was affected by the presence of trees and associated microorganisms. The dissolution rate of apatite by Scots pine plants that were or were not inoculated with the strain Burkholderia glathei PML1(12)Rp, and by inorganic (nitric) and organic (citric, oxalic and gluconic) acids at pH 5.5, 4.8, 3.8, 3.5, 3.0, and 2.0 was monitored in two controlled experiments: "plant-bacteria interaction" and "inorganic and organic acids". Analyses of the outlet solutions in the "plant-bacteria interaction" experiment showed that Scots pine roots and B. glathei PML1(12)Rp produced protons and organic acids such as gluconate, oxalate, acetate, and lactate. The weathering budget calculation revealed that Scots pines (with or without PML1(12)Rp) significantly increased (factor > 10) the release of Ca, P, As, Sr, Zn, U, Y, and rare earth elements such as Ce, La, Nd from apatite, compared to control abiotic treatment. Scanning electron microscopy observation confirmed traces of apatite dissolution in contact of roots. Most dissolved elements were taken up by Scots pine roots, i.e., approximately 50% of Ca, 70% of P, 30% of As, 70% of Sr, 90% of Zn, and 100% of U, Y, and rare earth elements. Interestingly, no significant additional effect due to the bacterial strain PML1(12)Rp on apatite dissolution and Scots pine nutrition and growth was observed. The "inorganic and organic acids" experiment demonstrated that the apatite dissolution efficacy of organic acids was higher than for the inorganic acid and varied in function of the acids: oxalic acid > citric acid > gluconic acid > nitric acid for pH ⩽3.5. In addition, apatite dissolution increased with increasing acidity for each acid. Only oxalic acid generated non-stoichiometric release of calcium and phosphorus from apatite in the solution at pH ⩽3.5, due to the precipitation of Ca-oxalate crystals at apatite surfaces. Comparison of the experiments revealed that the apatite dissolution rate by Scots pines supplied with nutritive solution at pH 5.5 reached 2.0 × 10-13 mol cm-2 s-1 and was equivalent to rates with nitric acid at pH 3.2, gluconic acid at pH 3.5, citric acid at pH 3.7, and oxalic acid at pH 3.8. Altogether our results highlight that, through the production of weathering agents, notably protons and organic acids, tree roots and root-associated microorganisms are able to significantly increase the release of macro- and micro-nutrients from apatite, thus maintaining high-nutrient conditions to support their growth.

Particle Geochemistry of Hydrothermal Systems and Implications for Mining Seafloor Massive Sulfides

NASA Astrophysics Data System (ADS)

Gartman, A.; Hein, J. R.

2016-12-01

Seafloor massive sulfide deposits form due to high-temperature hydrothermal venting that occurs globally, in every ocean basin, along plate boundaries and intra-plate hotspots. At these sites, the rapid mixing of hot, metal- and sulfur-rich reduced fluids into cold, oxygenated ocean water results in abundant mineral precipitation. The mining of seafloor massive sulfides is likely to occur in the near future and will generate a new class of mainly inorganic particulates, different from those formed in hydrothermal `black smoke.' While the major components of both black smoke & SMS tailings are Cu, Fe and Zn sulfides, many other minerals, including those containing technology critical elements, especially tellurium, are present. A comparison of these two classes of particulates will be presented, including chemical composition and reactivity to oxidative dissolution.

Atmospheric Transport and Input of Iron to the Southern Ocean

NASA Astrophysics Data System (ADS)

Tindale, N. W.

2002-12-01

While Australia is not generally considered to be a major source of mineral dust to the atmosphere, at least compared to Asian and African desert regions, it does appear to be the main source of mineral material to the Southern Ocean region south of Australia and New Zealand. In common with most of the greater Southern Ocean, this region contains high nitrate, low chlorophyll (HNLC) waters. Recent open ocean iron enrichment experiments in this region have demonstrated that phytoplankton growth and biomass are limited by iron availability. However the flux of atmospheric iron to this open ocean region is poorly known with very few direct measurements of mineral aerosol levels and input. Using mineral aerosol samples collected on Macquarie Island and at Cape Grim, together with other chemical data, air mass trajectories and satellite data, the spatial and temporal variability of aerosol iron transport and input to the Southern Ocean region south of Australia is estimated.

The global distribution and dynamics of chromophoric dissolved organic matter.

PubMed

Nelson, Norman B; Siegel, David A

2013-01-01

Chromophoric dissolved organic matter (CDOM) is a ubiquitous component of the open ocean dissolved matter pool, and is important owing to its influence on the optical properties of the water column, its role in photochemistry and photobiology, and its utility as a tracer of deep ocean biogeochemical processes and circulation. In this review, we discuss the global distribution and dynamics of CDOM in the ocean, concentrating on developments in the past 10 years and restricting our discussion to open ocean and deep ocean (below the main thermocline) environments. CDOM has been demonstrated to exert primary control on ocean color by its absorption of light energy, which matches or exceeds that of phytoplankton pigments in most cases. This has important implications for assessing the ocean biosphere via ocean color-based remote sensing and the evaluation of ocean photochemical and photobiological processes. The general distribution of CDOM in the global ocean is controlled by a balance between production (primarily microbial remineralization of organic matter) and photolysis, with vertical ventilation circulation playing an important role in transporting CDOM to and from intermediate water masses. Significant decadal-scale fluctuations in the abundance of global surface ocean CDOM have been observed using remote sensing, indicating a potentially important role for CDOM in ocean-climate connections through its impact on photochemistry and photobiology.

LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model

NASA Astrophysics Data System (ADS)

Zeebe, R. E.

2011-06-01

The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

Modern Deep-sea Sponges as Recorders of Bottom Water Silicon Isotopes

NASA Astrophysics Data System (ADS)

Hendry, K. R.; Georg, R. B.; Rickaby, R. E.; Robinson, L. F.; Halliday, A. N.

2008-12-01

Major zones of opal accumulation in the world oceans have experienced geographical shifts during the Cenozoic coincident with times of transition in oceanic circulation and climate. The global marine silica cycle is likely to respond to various large-scale changes including the distillation of Si and other nutrients in ocean basins; weathering and continental inputs; and biological productivity in surface waters. These processes could potentially be distinguished by their impact on the isotopic composition of dissolved silica in the world oceans. Although diatoms dominate uptake of silica in surface waters, box-modelling (de la Rocha and Bickle, 2005) suggests that sponges spicules have a greater potential to reflect whole ocean changes in the silica cycle, by recording deep-water silicon isotopes. Here, we introduce a new calibration study of modern deep- sea sponges collected on a transect cruise across the Drake Passage, in the Southern Ocean, from a range of depths and seawater silicic acid concentrations. Sponges were collected by benthic trawling, and dried immediately. The spicules were later isolated from cellular material and cleaned for surface contaminants, before dissolution and analysis by NuPlasma HR MC-ICP-MS in medium resolution mode. We discuss our preliminary data, the extent to which inter and intraspecies variations reflect environmental conditions, and the implications for palaeoreconstructions of the marine silicon cycle. de la Rocha, C. and M. Bickle (2005). Sensitivity of silicon isotopes to whole-ocean changes in the silica cycle. Marine Geology 217, 267-282.

Potential Increasing Dominance of Heterotrophy in the Global Ocean

NASA Astrophysics Data System (ADS)

Kvale, K.; Meissner, K. J.; Keller, D. P.

2016-02-01

Autotrophs are largely limited by resources in the modern ocean. However, standard metabolic theory suggests continued ocean warming could globally benefit heterotrophs, thereby reducing autotrophic nutrient limitation. The paleo record as well as modern observations offer evidence this has happened in the past and could happen again. Increasing dominance of heterotrophs would result in strong nutrient recycling in the upper ocean and high rates of net primary production (NPP), yet low carbon export to the deep ocean and sediments. We describe the transition towards such a state in the early 22nd century as a response to business-as-usual Representative Concentration Pathway forcing (RCP8.5) in an intermediate complexity Earth system model in three configurations: with and without an explicit calcifier phytoplankton class and calcite ballast model. In all models nutrient regeneration in the near surface becomes an increasingly important driver of primary production. The near-linear relationship between changes in NPP and global sea surface temperature (SST) found over the 21st century becomes exponential above a 2-4 °C global mean SST change. This transition to a more heterotrophic ocean agrees roughly with metabolic theory. Inclusion of small phytoplankton and calcifiers increase the model NPP:SST sensitivity because of their relatively higher nutrient affinity than general phytoplankton. Accounting for organic carbon "protected" from remineralization by carbonate ballast mitigates the exponential increase in NPP and provides an increasingly important pathway for deep carbon export with higher SST changes, despite simultaneous increasing carbonate dissolution rates due to ocean acidification.

Dissolved strontium and calcium levels in the tropical Indian Ocean

NASA Astrophysics Data System (ADS)

Steiner, Zvi; Sarkar, Amit; Turchyn, Alexandra

2017-04-01

Measurements of seawater alkalinity and dissolved calcium concentrations along oceanic transects are often used to calculate calcium carbonate precipitation and dissolution rates. Given that the distribution coefficient of strontium in CaCO3 varies greatly between different groups of organisms, adding precise measurements of dissolved strontium concentrations provides opportunities to also track relative contributions of these different groups to the regional CaCO3 cycle. However, there are several obstacles to this approach. These obstacles include unresolved systematic discrepancies between seawater calcium and alkalinity data, very large analytical noise around the calcium concentration measurements and the unconstrained role of acantharia (radiolarian precipitating SrSO4 skeletons) in the marine strontium cycle. During the first cruise of the second International Indian Ocean Expedition (IIOE-2) water samples were collected along 67°E from 9°N to 5°S to explore the dissolution rate of calcium carbonate in the water. The dissolution rate can be calculated by combining measurements of water column potential alkalinity with calcium and strontium concentrations measured by ICP-OES and calcium concentration measurements using isotope dilution thermal ionization mass spectrometry (ID-TIMS). CaCO3 mineral saturation state calculated using pH and total alkalinity suggests that along 67°E, the aragonite saturation horizon lays at depth of 500 m on both sides of the equator. Across the cruise transect, dissolved strontium concentrations increase by 2-3% along the thermocline suggesting rapid recycling of strontium rich phases. This is particularly evident just below the thermocline at 8-9°N and below 1000 m water depth, south of the equator. The deep, southern enrichment in strontium does not involve a change in the Sr/Ca ratio, suggesting that this strontium enrichment is related to CaCO3 dissolution. In contrast, in the intermediate waters of the northern part of the section Sr/Ca ratios increase significantly. This finding is opposite to expectations based on plankton net tows collected during the cruise, where we found high abundance of acantharia in the southern parts of the section, while the preferential enrichment in strontium is in the northern part of the section. When potential alkalinity is calculated by correcting the normalized total alkalinity for the effects of nutrient accumulation below the thermocline, we observe that the increase in alkalinity begins at 100 m, well above the aragonite saturation horizon. The total change in dissolved calcium concentrations between 0 and 2000 m is similar to the total change in potential alkalinity yet their profiles do not overlap; calcium concentrations increase faster than total alkalinity between 100-1000 m and the gap is closed between 1000-1500 m. This suggests an additional, unaccounted process that is likely occurring in the Red Sea and Persian Gulf, the intermediate water sources of this region.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faye, Sherry A.; Richards, Jason M.; Gallardo, Athena M.

Sequential extraction is a useful technique for assessing the potential to leach actinides from soils; however, current literature lacks uniformity in experimental details, making direct comparison of results impossible. This work continued development toward a standardized five-step sequential extraction protocol by analyzing extraction behaviors of 232Th, 238U, 239,240Pu and 241Am from lake and ocean sediment reference materials. Results produced a standardized procedure after creating more defined reaction conditions to improve method repeatability. A NaOH fusion procedure is recommended following sequential leaching for the complete dissolution of insoluble species.

Reversal of ocean acidification enhances net coral reef calcification.

PubMed

Albright, Rebecca; Caldeira, Lilian; Hosfelt, Jessica; Kwiatkowski, Lester; Maclaren, Jana K; Mason, Benjamin M; Nebuchina, Yana; Ninokawa, Aaron; Pongratz, Julia; Ricke, Katharine L; Rivlin, Tanya; Schneider, Kenneth; Sesboüé, Marine; Shamberger, Kathryn; Silverman, Jacob; Wolfe, Kennedy; Zhu, Kai; Caldeira, Ken

2016-03-17

Approximately one-quarter of the anthropogenic carbon dioxide released into the atmosphere each year is absorbed by the global oceans, causing measurable declines in surface ocean pH, carbonate ion concentration ([CO3(2-)]), and saturation state of carbonate minerals (Ω). This process, referred to as ocean acidification, represents a major threat to marine ecosystems, in particular marine calcifiers such as oysters, crabs, and corals. Laboratory and field studies have shown that calcification rates of many organisms decrease with declining pH, [CO3(2-)], and Ω. Coral reefs are widely regarded as one of the most vulnerable marine ecosystems to ocean acidification, in part because the very architecture of the ecosystem is reliant on carbonate-secreting organisms. Acidification-induced reductions in calcification are projected to shift coral reefs from a state of net accretion to one of net dissolution this century. While retrospective studies show large-scale declines in coral, and community, calcification over recent decades, determining the contribution of ocean acidification to these changes is difficult, if not impossible, owing to the confounding effects of other environmental factors such as temperature. Here we quantify the net calcification response of a coral reef flat to alkalinity enrichment, and show that, when ocean chemistry is restored closer to pre-industrial conditions, net community calcification increases. In providing results from the first seawater chemistry manipulation experiment of a natural coral reef community, we provide evidence that net community calcification is depressed compared with values expected for pre-industrial conditions, indicating that ocean acidification may already be impairing coral reef growth.

Reversal of ocean acidification enhances net coral reef calcification

NASA Astrophysics Data System (ADS)

Albright, Rebecca; Caldeira, Lilian; Hosfelt, Jessica; Kwiatkowski, Lester; MacLaren, Jana K.; Mason, Benjamin M.; Nebuchina, Yana; Ninokawa, Aaron; Pongratz, Julia; Ricke, Katharine L.; Rivlin, Tanya; Schneider, Kenneth; Sesboüé, Marine; Shamberger, Kathryn; Silverman, Jacob; Wolfe, Kennedy; Zhu, Kai; Caldeira, Ken

2016-03-01

Approximately one-quarter of the anthropogenic carbon dioxide released into the atmosphere each year is absorbed by the global oceans, causing measurable declines in surface ocean pH, carbonate ion concentration ([CO32-]), and saturation state of carbonate minerals (Ω). This process, referred to as ocean acidification, represents a major threat to marine ecosystems, in particular marine calcifiers such as oysters, crabs, and corals. Laboratory and field studies have shown that calcification rates of many organisms decrease with declining pH, [CO32-], and Ω. Coral reefs are widely regarded as one of the most vulnerable marine ecosystems to ocean acidification, in part because the very architecture of the ecosystem is reliant on carbonate-secreting organisms. Acidification-induced reductions in calcification are projected to shift coral reefs from a state of net accretion to one of net dissolution this century. While retrospective studies show large-scale declines in coral, and community, calcification over recent decades, determining the contribution of ocean acidification to these changes is difficult, if not impossible, owing to the confounding effects of other environmental factors such as temperature. Here we quantify the net calcification response of a coral reef flat to alkalinity enrichment, and show that, when ocean chemistry is restored closer to pre-industrial conditions, net community calcification increases. In providing results from the first seawater chemistry manipulation experiment of a natural coral reef community, we provide evidence that net community calcification is depressed compared with values expected for pre-industrial conditions, indicating that ocean acidification may already be impairing coral reef growth.

Effect of atmospheric organic complexation on iron-bearing dust solubility

NASA Astrophysics Data System (ADS)

Paris, R.; Desboeufs, K. V.

2013-05-01

Recent studies reported that the effect of organic complexation may be a potentially important process to be considered by models estimating atmospheric iron flux to the ocean. In this study, we investigated this process effect by a series of dissolution experiments on iron-bearing dust in the presence or the absence of various organic compounds (acetate, formate, oxalate, malonate, succinate, glutarate, glycolate, lactate, tartrate and humic acid as an analogue of humic like substances, HULIS) typically found in atmospheric waters. Only 4 of tested organic ligands (oxalate, malonate, tartrate and humic acid) caused an enhancement of iron solubility which was associated with an increase of dissolved Fe(II) concentrations. For all of these organic ligands, a positive linear dependence of iron solubility to organic concentrations was observed and showed that the extent of organic complexation on iron solubility decreased in the following order: oxalate >malonate = tartrate > humic acid. This was attributed to the ability of electron donors of organic ligands and implies a reductive ligand-promoted dissolution. This study confirms that among the known atmospheric organic binding ligands of Fe, oxalate is the most effective ligand promoting dust iron solubility and showed, for the first time, the potential effect of HULIS on iron dissolution under atmospheric conditions.

Atmospheric Processing and Iron Mobilization of Ilmenite: Iron-Containing Ternary Oxide in Mineral Dust Aerosol.

PubMed

Hettiarachchi, Eshani; Hurab, Omar; Rubasinghege, Gayan

2018-02-08

Over the last several decades, iron has been identified as a limiting nutrient in about half of the world's oceans. Its most significant source is identified as deposited iron-containing mineral dust that has been processed during atmospheric transportation. The current work focuses on chemical and photochemical processing of iron-containing mineral dust particles in the presence of nitric acid, and an organic pollutant dimethyl sulfide under atmospherically relevant conditions. More importantly, ilmenite (FeTiO 3 ) is evaluated as a proxy for the iron-containing mineral dust. The presence of titanium in its lattice structure provides higher complexity to mimic mineral dust, yet it is simple enough to study reaction pathways and mechanisms. Here, spectroscopic methods are combined with dissolution measurements to investigate atmospheric processing of iron in mineral dust, with specific focus on particle mineralogy, particle size, and their environmental conditions (i.e., pH and solar flux). Our results indicate that the presence of titanium elemental composition enhances iron dissolution from mineral dust, at least by 2-fold comparison with its nontitanium-containing counterparts. The extent of iron dissolution and speciation is further influenced by the above factors. Thus, our work highlights these important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol.

Stability of the Orca Basin Brine Interface Determined Using Radium Isotopes

NASA Astrophysics Data System (ADS)

Peterson, R. N.; Peterson, L.; Montoya, J. P.; Joye, S. B.

2016-02-01

The Orca Basin is an intraslope basin in the northern continental slope of the Gulf of Mexico, and contains a deep (up to 220 m) anoxic, hypersaline brine lake. The brine interface extends from ocean salinity (at a water depth of 2125 m) to a constant salinity of 215 psu below a depth of 2250 m. This interface is considered to be among the most stable interfaces on the planet, and contains distinct zones of macrofaunal and microbial assemblages. The brine lake is supported by continued dissolution of exposed rock salt at an estimated rate of 0.5 million t/yr. Such dissolution of salt should serve as a source of radium isotopes, and given their range of half-lives, these isotopes can serve as unique proxies to the location and rate of salt dissolution into this basin. We have collected a series of radon and radium isotope profiles through this brine lake over the past 4 years, which allow us to assess the spatial and temporal stability of this interface. Throughout the brine lake, we observe strong enrichments in unsupported Ra-224, Rn-222, and Ra-226 in a 10 m thick zone near the base of the brine interface, between 2232 m and 2242 m. The strong enrichment in unsupported Ra-224 in this layer must be supported by a continuous source, presumably the dissolution of exposed salt rock. Various degrees of isotopic enrichment throughout the lake provide an assessment of the rates of lateral and vertical dispersion of salt and associated chemical constituents.

NASA Oceanic Processes Program, Fiscal Year 1981

NASA Technical Reports Server (NTRS)

1982-01-01

Summaries are included for Nimbus 7, Seasat, TIROS-N, Altimetry, Color Radiometry, in situ data collection systems, Synthetic Aperture Radar (SAR)/Open Ocean, SAR/Sea Ice, Scatterometry, National Oceanic Satellite System, Free Flying Imaging Radar Experiment, TIROS-N/Scatterometer and/or ocean color scanner, and Ocean Topography Experiment. Summaries of individual research projects sponsored by the Ocean Processes Program are given. Twelve investigations for which contracting services are provided by NOAA are included.

Abyssal ostracods from the South and Equatorial Atlantic Ocean: Biological and paleoceanographic implications

USGS Publications Warehouse

Yasuhara, Moriaki; Cronin, T. M.; Martinez, Arbizu P.

2008-01-01

We report the distribution of ostracods from ???5000 m depth from the Southeast and Equatorial Atlantic Ocean recovered from the uppermost 10 cm of minimally disturbed sediments taken by multiple-corer during the R/V Meteor DIVA2 expedition M63.2. Five cores yielded the following major deep-sea genera: Krithe, Henryhowella, Poseidonamicus, Legitimocythere, Pseudobosquetina, and Pennyella. All genera are widely distributed in abyssal depths in the world's oceans and common in Cenozoic deep-sea sediments. The total number of ostracod specimens is higher and ostracod shell preservation is better near the sediment-water interface, especially at the 0-1 cm core depths. Core slices from ???5 to 10 cm were barren or yielded a few poorly preserved specimens. The DIVA2 cores show that deep-sea ostracod species inhabit corrosive bottom water near the carbonate compensation depth (CCD) even though their calcareous valves are rarely preserved as fossils in sediment cores due to postmortem dissolution. Their occurrence at great water depths may partially explain the well-known global distributions of major deep-sea taxa in the world's oceans, although further expeditions using minimal-disturbance sampling devices are needed to fill geographic gaps. ?? 2008 Elsevier Ltd. All rights reserved.

The Effects of Ocean Acidification on Predator-Prey Interactions between Mya arenaria and Callinectes sapidus

NASA Astrophysics Data System (ADS)

Longmire, K.; Glaspie, C.; Seitz, R.

2016-02-01

The study examined the implications of ocean acidification for Mya arenaria and the predator-prey dynamics between M. arenaria and Callinectes sapidus. Clams were subjected to either ambient conditions or acidified conditions and grown over four weeks. Mortality, shell lengths, and biomass (ash-free dry weights) were recorded for clams destructively sampled each week. Clams were subjected to behavioral experiments to determine their response to an approaching physical disturbance. Crabs were exposed to acidified or ambient conditions for 48 hours, and placed in 48 hour mesocosm trials with clams. Shell lengths, mortality and biomass between the ambient and acidified clams were not significantly different between acidified and ambient treatments. Shell ash weights were lower for acidified clams, evidence of shell dissolution. In the behavioral experiment, ocean acidification reduced the ability of clams to respond to a predator stimulus. Lastly, in predator-prey mesocosm trials, in ambient conditions, crabs ate all or none of the available clams, whereas acidified crabs ate all available clams in many trials and ate at least one acidified clam per trial. The early effects of ocean acidification on M. arenaria will manifest in trophic interactions with other species, rather than impacting M. arenaria alone.

Untangling biogeochemical processes from the impact of ocean circulation: First insight on the Mediterranean dissolved barium dynamics

NASA Astrophysics Data System (ADS)

Jullion, L.; Jacquet, S. H. M.; Tanhua, T.

2017-08-01

Based on an unprecedented dissolved barium (D_Ba) data set collected in the Mediterranean Sea during a zonal transect between the Lebanon coast and Gibraltar (M84/3 cruise, April 2011), we decompose the D_Ba distribution to isolate the contribution of biogeochemical processes from the impact of the oceanic circulation. We have built a simple parametric water mass analysis (Parametric Optimum Multiparameter analysis) to reconstruct the contribution of the different Mediterranean water masses to the thermohaline structure. These water mass fractions have then been used to successfully reconstruct the background vertical gradient of D_Ba reflecting the balance between the large-scale oceanic circulation and the biological activity over long time scales. Superimposed on the background field, several D_Ba anomalies have been identified. Positive anomalies are associated with topographic obstacles and may be explained by the dissolution of particulate biogenic barium (P_Ba barite) of material resuspended by the local currents. The derived dissolution rates range from 0.06 to 0.21 μmol m-2 d-1. Negative anomalies are present in the mesopelagic region of the western and eastern basins (except in the easternmost Levantine basin) as well as in the abyssal western basin. This represents the first quantification of the nonconservative component of the D_Ba signal. These mesopelagic anomalies could reflect the subtraction of D_Ba during P_Ba barite formation occurring during organic carbon remineralization. The deep anomalies may potentially reflect the transport of material toward the deep sea during winter deep convection and the subsequent remineralization. The D_Ba subtraction fluxes range from -0.07 to -1.28 μmol m-2 d-1. D_Ba-derived fluxes of P_Ba barite (up to 0.21 μmol m-2 d-1) and organic carbon (13 to 29 mmol C m-2 d-1) are in good agreement with other independent measurements suggesting that D_Ba can help constrain remineralization horizons. This study highlights the importance of quantifying the impact of the large-scale oceanic circulation in order to better understand the biogeochemical cycling of elements and to build reliable geochemical proxies.

The growth of finfish in global open-ocean aquaculture under climate change.

PubMed

Klinger, Dane H; Levin, Simon A; Watson, James R

2017-10-11

Aquaculture production is projected to expand from land-based operations to the open ocean as demand for seafood grows and competition increases for inputs to land-based aquaculture, such as freshwater and suitable land. In contrast to land-based production, open-ocean aquaculture is constrained by oceanographic factors, such as current speeds and seawater temperature, which are dynamic in time and space, and cannot easily be controlled. As such, the potential for offshore aquaculture to increase seafood production is tied to the physical state of the oceans. We employ a novel spatial model to estimate the potential of open-ocean finfish aquaculture globally, given physical, biological and technological constraints. Finfish growth potential for three common aquaculture species representing different thermal guilds-Atlantic salmon ( Salmo salar ), gilthead seabream ( Sparus aurata ) and cobia ( Rachycentron canadum )-is compared across species and regions and with climate change, based on outputs of a high-resolution global climate model. Globally, there are ample areas that are physically suitable for fish growth and potential expansion of the nascent aquaculture industry. The effects of climate change are heterogeneous across species and regions, but areas with existing aquaculture industries are likely to see increases in growth rates. In areas where climate change results in reduced growth rates, adaptation measures, such as selective breeding, can probably offset potential production losses. © 2017 The Author(s).

Open Vessel Data Management (OpenVDM), Open-source Software to Assist Vessel Operators with the Task of Ship-wide Data Management.

NASA Astrophysics Data System (ADS)

Pinner, J. W., IV

2016-02-01

Data from shipboard oceanographic sensors are collected in various ASCii, binary, open and proprietary formats. Acquiring all of these formats using single, monolithic data acquisition system (DAS) can be cumbersome, complex and difficult to adapt for the ever changing suite of emerging oceanographic sensors. Another approach to the at-sea data acquisition challenge is to utilize multiple DAS software packages and corral the resulting data files with a ship-wide data management system. The Open Vessel Data Management project (OpenVDM) implements this second approach to ship-wide data management and over the last three years has successfully demonstrated it's ability to deliver a consistent cruise data package to scientists while reducing the workload placed on marine technicians. In addition to meeting the at-sea and post-cruise needs of scientists OpenVDM is helping vessel operators better adhere to the recommendations and best practices set forth by 3rd party data management and data quality groups such as R2R and SAMOS. OpenVDM also includes tools for supporting telepresence-enabled ocean research/exploration such as bandwidth-efficient ship-to-shore data transfers, shore-side data access, data visualization and near-real-time data quality tests and data statistics. OpenVDM is currently operating aboard three vessels. The R/V Endeavor, operated by the University of Rhode Island, is a regional-class UNOLS research vessel operating under the traditional NFS, P.I. driven model. The E/V Nautilus, operated by the Ocean Exploration Trust specializes in ROV-based, telepresence-enabled oceanographic research. The R/V Falkor operated by the Schmidt Ocean Institute is an ocean research platform focusing on cutting-edge technology development. These three vessels all have different missions, sensor suites and operating models yet all are able to leverage OpenVDM for managing their unique datasets and delivering a more consistent cruise data package to scientists and data archives.

Dissolution Studies of Papaverine Hydrochloride from Tablets in Three Pharmacopoeia Apparatuses.

PubMed

Polski, Andrzej; Kasperek, Regina; Rogowska, Magdalena; Iwaniak, Karol; Sobòtka-Polska, Karolina; Poleszak, Ewa

2015-01-01

In tablet production, the most important aspects are the physical properties of the tablets and their dissolution studies, which can be performed in four pharmacopoeial apparatuses. There are differences between them in construction and action, so differences in the results obtained are possible. The aim of the study was to compare the release of a model drug substance (papaverine hydrochloride) from tablets in three pharmacopoeial dissolution apparatus: a basket, a paddle (closed system) and flow-through cell (open system). The one series of tablets were produced by direct compression in a tablet press. The physical properties of the tablets (weight and size uniformity test, friability and hardness tests, disintegration time test), drug content and the release study of papaverine hydrochloride from tablets were studied in three dissolution apparatuses. The content of the active substance was studied spectrophotometrically. All tablets met the pharmacopoeic requirements. Over 80% of the model substance released from the tablets after 14 min in flow through the cell apparatus, while in the basket and paddle apparatuses after about 7 min 30 sec. After 20 min, the amount of the substance released in all apparatuses was over 90%. The release profiles of the drug substance in paddle and basket apparatuses were similar, while in the flow-through cell apparatus it was slightly slower. When the study conditions and composition of the tablets are the same, the release profile of the drug can be affected by the type of dissolution apparatus.

Oceanic ecosystem dynamics during gigantic volcanic episodes: the Ontong Java and Manihiki Plateaus recorded by calcareous nannoplankton. (Invited)

NASA Astrophysics Data System (ADS)

Erba, E.

2010-12-01

Earth's volcanic activity introduces environmental stress that biota are forced to survive. There is a general consensus on the role of volcanogenic carbon dioxide increases, and implicit tectonic-igneous events, triggering major climate changes and profound variations in chemical, physical and trophic characteristics of the oceans through the Phanerozoic. Cretaceous geological records indicate conditions of excess atmCO2 (up to 2000-3000 ppm) derived from construction of Large Igneous Provinces (LIPs). In such “high CO2 world” and greenhouse conditions, the deep ocean became depleted of oxygen promoting the accumulation and burial of massive amounts of organic matter; such episodes are recognized as Oceanic Anoxic Events (OAEs) and their geological records merit careful examination of how the Earth system, and Life in particular, can overcome extreme experiments of global change. The Early Aptian (˜ 120 million years ago) OAE1a is a complex example of volcanicCO2-induced environmental stress. There is a general consensus on the causes of this case-history, namely excess CO2 derived from the construction of the Ontong Java-Manihiki LIP. Multi- and inter-disciplinary studies of the OAE1a have pointed out C, O, Os, Sr isotopic anomalies, a biocalcification crisis in pelagic and neritic settings, enhanced fertility and primary productivity, as well as ocean acidification. Available cyclochronology allows high-resolution dating of biotic and environmental fluctuations, providing the precision necessary for understanding the role of volcanogenic CO2 on nannoplankton biocalcification, adaptations, evolutionary innovation and/or extinctions. The reconstructed sequence of volcanogenic CO2 pulses, and perhaps some clathrate melting, triggered a climate change to supergreenhouse conditions, anoxia and ocean acidification. The demise of heavily calcified nannoconids and reduced calcite paleofluxes marks beginning of the pre-OAE1a calcification crisis. Ephemeral coccolith dwarfism and malformation represent adjustments to survive lower pH. Deep-water acidification occurs with a delay of 25-30 thousand years: a dissolution event recording 1 to 2km shallowing of the Calcite Compensation Depth anticipated the onset of anoxic sedimentation. A major acceleration in weathering has been identified in the lowermost part of OAE1a. After acidification-dissolution climax, nannoplankton and carbonate recovery developed over ~160 kyr, under persisting global dysoxia-anoxia. This recovery presumably implies a stasis of the LIP activity and gradual buffering of ocean acidification or a decrease in volcanogenic CO2 emissions and consistently higher CO2 drawdown through Corg burial and/or weathering. Rising CO2 and surface-ocean acidification during OAE1a triggered false extinctions among calcareous nannoplankton. Conversely, a major origination episode starts approximately 1 My before global anoxia and persists through OAE1a and associated acidification. Increasing pCO2 caused complex and species-specific reactions, including production of r-strategist taxa, which, however, secreted dwarf and malformed coccoliths as a strategy to overcome acidification.

Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene

USGS Publications Warehouse

Toth, Lauren T.; Cheng, Hai; Edwards, R. Lawrence; Ashe, Erica; Richey, Julie N.

2017-01-01

A growing body of research suggests that the marine environments of south Florida provide a critical link between the tropical and high-latitude Atlantic. Changes in the characteristics of water masses off south Florida may therefore have important implications for our understanding of climatic and oceanographic variability over a broad spatial scale; however, the sources of variability within this oceanic corridor remain poorly understood. Measurements of ΔR, the local offset of the radiocarbon reservoir age, from shallow-water marine environments can serve as a powerful tracer of water-mass sources that can be used to reconstruct variability in local-to regional-scale oceanography and hydrology. We combined radiocarbon and U-series measurements of Holocene-aged corals from the shallow-water environments of the Florida Keys reef tract (FKRT) with robust statistical modeling to quantify the millennial-scale variability in ΔR at locations with (“nearshore”) and without (“open ocean”) substantial terrestrial influence. Our reconstructions demonstrate that there was significant spatial and temporal variability in ΔR on the FKRT during the Holocene. Whereas ΔR was similar throughout the region after ∼4000 years ago, nearshore ΔR was significantly higher than in the open ocean during the middle Holocene. We suggest that the elevated nearshore ΔR from ∼8000 to 5000 years ago was most likely the result of greater groundwater influence associated with lower sea level at this time. In the open ocean, which would have been isolated from the influence of groundwater, ΔR was lowest ∼7000 years ago, and was highest ∼3000 years ago. We evaluated our open-ocean model of ΔR variability against records of local-to regional-scale oceanography and conclude that local upwelling was not a significant driver of open-ocean radiocarbon variability in this region. Instead, the millennial-scale trends in open-ocean ΔR were more likely a result of broader-scale changes in western Atlantic circulation associated with an increase in the supply of equatorial South Atlantic water to the Caribbean and shifts in the character of South Atlantic waters resulting from variation in the intensity of upwelling off the southwest coast of Africa. Because accurate estimates of ΔR are critical to precise calibrations of radiocarbon dates from marine samples, we also developed models of nearshore and open-ocean ΔR versus conventional 14C ages that can be used for regional radiocarbon calibrations for the Holocene. Our study provides new insights into the patterns and drivers of oceanographic and hydrologic variability in the Straits of Florida and highlights the value of the paleoceanographic records from south Florida to our understanding of Holocene changes in climate and ocean circulation throughout the Atlantic.

The Growing Human Footprint on Coastal and Open-Ocean Biogeochemistry

NASA Astrophysics Data System (ADS)

Doney, Scott C.

2010-06-01

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources.

The growing human footprint on coastal and open-ocean biogeochemistry.

PubMed

Doney, Scott C

2010-06-18

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources.

Forecasting tsunamis in Poverty Bay, New Zealand, with deep-ocean gauges

NASA Astrophysics Data System (ADS)

Power, William; Tolkova, Elena

2013-12-01

The response/transfer function of a coastal site to a remote open-ocean point is introduced, with the intent to directly convert open-ocean measurements into the wave time history at the site. We show that the tsunami wave at the site can be predicted as the wave is measured in the open ocean as far as 1,000+ km away from the site, with a straightforward computation which can be performed almost instantaneously. The suggested formalism is demonstrated for the purpose of tsunami forecasting in Poverty Bay, in the Gisborne region of New Zealand. Directional sensitivity of the site response due to different conditions for the excitation of the shelf and the bay's normal modes is investigated and used to explain tsunami observations. The suggested response function formalism is validated with available records of the 2010 Chilean tsunami at Gisborne tide gauge and at the nearby deep-ocean assessment and reporting of tsunamis (DART) station 54401. The suggested technique is also demonstrated by hindcasting the 2011 Tohoku tsunami and 2012 Haida Gwaii tsunami at Monterey Bay, CA, using an offshore record of each tsunami at DART station 46411.

Tracking changes in ocean redox during the PETM using stable chromium isotopes

NASA Astrophysics Data System (ADS)

Dixon, S. K.; Parkinson, I. J.; Sexton, P.; Fehr, M.; James, R. H.; Peacock, C.

2012-12-01

Climate models predict a decline in oceanic dissolved oxygen under global warming conditions and observations suggest the expansion of tropical oxygen minimum zones is already underway1, with concern over the trend for future seawater oxygen levels. Therefore, previous deoxygenation events in the geological record may provide insight into the dynamics of changing oxygen levels in the Earth's oceans. One such event, is the Palaeocene-Eocene Thermal Maximum (PETM) at ~55Ma which represents a period of rapid global warming. Multiple lines of evidence suggest that at least on a local scale, near bottom anoxia occurred during the event2,3 and further understanding of changing redox conditions during this period may provide insight into future sea level oxygenation. To track seawater oxygenation during the PETM, we are utilising stable Cr isotope composition of marine carbonates, a new palaeo-redox proxy, which has shown potential when applied to modern and ancient carbonates 4,5. We present δ53Cr, trace element and REE data of foraminiferal ooze deposits over the PETM interval. Samples were taken from the North East Atlantic DSDP site 401, which preserves an exceptional and complete carbonate sequence over the interval, at a time when ocean acidification lead to massive sea floor carbonate dissolution6. Foraminifera were taken from the 63 - 150μm size fraction and planktic count data indicate that the relative proportions of dominant species do not change significantly over the event7. Systematic changes occur in REEs, Cr concentration and δ53Cr coincident with the onset of the negative δ13C excursion. The Cr concentrations of the carbonates decrease into the event, which suggests the sea level Cr concentration has fallen. We interpret this to reflect falling oxygen concentration in the seawater, leading to a decrease in aqueous Cr (VI) via precipitation of Cr out of the water column in the form of insoluble Cr (III) hydroxide. Additionally, we will demonstrate how stable Cr isotopes in carbonates respond to changes in ocean chemistry during the PETM. (1) Stramma et al. (2008). Science, 320, 655-658. (2) Dickson et al. (2012). Geology, 40, 639-642. (3) Dypvik et al. (2011). Palaeogeography, Palaeoclimatology, Palaeoecology, 302, 156-169. (4) Bonnand (2011). PhD thesis, The Open University ; (5) Frei et al. (2011). Earth and Planet. Sci. Lett., 312, 114-125. (6) Zachos et al. (2005). Science, 308, 1611-1615. (7) Pardo et al. (1997). Marine Micropaleontology, 29, 129-158.

Earth 2075 (CO2) - can Ocean-Amplified Carbon Capture (oacc) Impart Atmospheric CO2-SINKING Ability to CCS Fossil Energy?

NASA Astrophysics Data System (ADS)

Fry, R.; Routh, M.; Chaudhuri, S.; Fry, S.; Ison, M.; Hughes, S.; Komor, C.; Klabunde, K.; Sethi, V.; Collins, D.; Polkinghorn, W.; Wroobel, B.; Hughes, J.; Gower, G.; Shkolnik, J.

2017-12-01

Previous attempts to capture atmospheric CO2 by algal blooming were stalled by ocean viruses, zooplankton feeding, and/or bacterial decomposition of surface blooms, re-releasing captured CO2 instead of exporting it to seafloor. CCS fossil energy coupling could bypass algal bloom limits—enabling capture of 10 GtC/yr atmospheric CO2 by selective emiliania huxleyi (EHUX) blooming in mid-latitude open oceans, far from coastal waters and polar seas. This could enable a 500 GtC drawdown, 350 ppm restoration by 2050, 280 ppm CO2 by 2075, and ocean pH 8.2. White EHUX blooms could also reflect sunlight back into outer space and seed extra ocean cloud cover, via DMS release, to raise albedo 1.8%—restoring preindustrial temperature (ΔT = 0°C) by 2030. Open oceans would avoid post-bloom anoxia, exclusively a coastal water phenomenon. The EHUX calcification reaction initially sources CO2, but net sinking prevails in follow-up equilibration reactions. Heavier-than-water EHUX sink captured CO2 to the sea floor before surface decomposition occurs. Seeding EHUX high on their nonlinear growth curve could accelerate short-cycle secondary open-ocean blooming—overwhelming mid-latitude viruses, zooplankton, and competition from other algae. Mid-latitude "ocean deserts" exhibit low viral, zooplankton, and bacterial counts. Thermocline prevents nutrient upwelling that would otherwise promote competing algae. Adding nitrogen nutrient would foster exclusive EHUX blooming. Elevated EHUX seed levels could arise from sealed, pH-buffered, floating, seed-production bioreactors infused with 10% CO2 from carbon feedstock supplied by inland CCS fossil power plants capturing 90% of emissions as liquid CO2. Deep-water SPAR platforms extract natural gas from beneath the sea floor. On-platform Haber and pH processing could convert extracted CH4 to buffered NH4+ nutrient, enabling ≥0.7 GtC/yr of bioreactor seed production and 10 GtC/yr of amplified secondary open-ocean CO2 capture—making CCS fossil energy 1400% carbon negative.

Investigation of Ruthenium Dissolution in Advanced Membrane Electrode Assemblies for Direct Methanol Based Fuel Cell Stacks

NASA Technical Reports Server (NTRS)

Valdez, Thomas I.; Firdosy, S.; Koel, B. E.; Narayanan, S. R.

2005-01-01

Dissolution of ruthenium was observed in the 80-cell stack. Duration testing was performed in single cell MEAs to determine the pathway of cell degradation. EDAX analysis on each of the single cell MEAs has shown that the Johnson Matthey commercial catalyst is stable in DMFC operation for 250 hours, no ruthenium dissolution was observed. Changes in the hydrophobicity of the cathode backing papers was minimum. Electrode polarization analysis revealed that the MEA performance loss is attributed to changes in the cathode catalyst layer. Ruthenium migration does not seem to occur during cell operation but can occur when methanol is absent from the anode compartment, the cathode compartment has access to air, and the cells in the stack are electrically connected to a load (Shunt Currents). The open-to-air cathode stack design allowed for: a) The MEAs to have continual access to oxygen; and b) The stack to sustain shunt currents. Ruthenium dissolution in a DMFC stack can be prevented by: a) Developing an internally manifolded stacks that seal reactant compartments when not in operation; b) Bringing the cell voltages to zero quickly when not in operation; and c) Limiting the total number of cells to 25 in an effort to limit shunt currents.

Enhanced in vivo absorption of CB-1 antagonist in rats via solid solutions prepared by hot-melt extrusion.

PubMed

Ranzani, L S; Font, J; Galimany, F; Santanach, A; Gomez-Gomar, A M; Casadevall, G; Gryczke, A

2011-06-01

The aim of the present work was to investigate in vitro dissolution properties of three binary solid solutions prepared by a hot-melt extrusion (HME) process with vinyl pirrolidone--vinyl acetate copolymer (Kollidon VA 64), ethyl acrylate, methyl methacrylate polymer (Eudragit E) polyetilenglicol 8000 (PEG 8000) with a cannabinoid type 1 (CB-1) antagonist. Hansen solubility parameters were calculated from the chemical structures of the drug and the individual polymers in order to predict miscibility. Solid state characterizations of drug substance, physical blends and HME formulations were performed with differential scanning calorimetry. The dissolution testing conducted under sink conditions revealed that the dissolution rate of HME formulations improved around 1.8-fold vs drug substance. Supersaturation dissolution study demonstrated that HME formulations composed by Eudragit E and Kollidon VA64 increased drug solubility between 30- and 35-fold, respectively comparing to the drug substance. Physical and chemical stability of formulations were studied at 40°C/75%HR with open dish during 15 days. The formulation composed by the drug and Eudragit E at 10:90 was evaluated for in vivo drug absorption in male Wistar-Hannover rats and it was found to increase CB-1 absorption threefold greater than pure drug oral suspension.

On the role of mesoscale eddies for the biological productivity and biogeochemistry in the eastern tropical Pacific Ocean off Peru

NASA Astrophysics Data System (ADS)

Stramma, L.; Bange, H. W.; Czeschel, R.; Lorenzo, A.; Frank, M.

2013-06-01

Mesoscale eddies seem to play an important role for both the hydrography and biogeochemistry of the eastern tropical Pacific Ocean (ETSP) off Peru. However, detailed surveys of these eddies are not available, which has so far hampered an in depth understanding of their implications for nutrient distribution and biological productivity. In this study three eddies along a section at 16°45' S have been surveyed intensively during R/V Meteor cruise M90 in November 2012. A coastal mode water eddy, an open ocean mode water eddy and an open ocean cyclonic eddy have been identified and sampled in order to determine both their hydrographic properties and their influence on the biogeochemical setting of the ETSP. In the thermocline the temperature of the coastal anticyclonic eddy was up to 2 °C warmer, 0.2 more saline and the swirl velocity was up to 35 cm s-1. The observed temperature and salinity anomalies, as well as swirl velocities of both types of eddies were about twice as large as had been described for the mean eddies in the ETSP and the observed heat and salt anomalies (AHA, ASA) show a much larger variability than the mean AHA and ASA. We found that the eddies contributed significantly to productivity by maintaining pronounced subsurface maxima of chlorophyll. Based on a comparison of the coastal (young) mode water eddy and the open ocean (old) mode water eddy we conclude that the aging of eddies when they detach from the coast and move westward to the open ocean considerably influences the eddies' properties: chlorophyll maxima are weaker and nutrients are subducted. The coastal mode water eddy was found to be a hotspot of nitrogen loss in the OMZ, whereas, the open ocean cyclonic eddy was of negligible importance for nitrogen loss. Our results show that the important role the eddies play in the ETSP can only be fully deciphered and understood through dedicated high spatial and temporal resolution oceanographic/biogeochemical surveys.

Evaluating the performance of Sentinel-3 SRAL SAR Altimetry in the Coastal and Open Ocean, and developing improved retrieval methods - The ESA SCOOP Project.

NASA Astrophysics Data System (ADS)

Benveniste, J.; Cotton, D.; Moreau, T.; Varona, E.; Roca, M.; Cipollini, P.; Cancet, M.; Martin, F.; Fenoglio-Marc, L.; Naeije, M.; Fernandes, J.; Restano, M.; Ambrozio, A.

2016-12-01

The ESA Sentinel-3 satellite, launched in February 2016 as a part of the Copernicus programme, is the second satellite to operate a SAR mode altimeter. The Sentinel 3 Synthetic Aperture Radar Altimeter (SRAL) is based on the heritage from Cryosat-2, but this time complemented by a Microwave Radiometer (MWR) to provide a wet troposphere correction, and operating at Ku and C-Bands to provide an accurate along-track ionospheric correction. Together this instrument package, including both GPS and DORIS instruments for accurate positioning, allows accurate measurements of sea surface height over the ocean, as well as measurements of significant wave height and surface wind speed. SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, started in September 2015, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, in the coastal zone and open-ocean, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. There is also a work package to develop and evaluate an improved Wet Troposphere correction for Sentinel-3, based on the measurements from the on-board MWR, further enhanced mostly in the coastal and polar regions using third party data, and provide recommendations for use. At the end of the project recommendations for further developments and implementations will be provided through a scientific roadmap. In this presentation we provide an overview of the SCOOP project, highlighting the key deliverables and discussing the potential impact of the results in terms of the application of delay-Doppler (SAR) altimeter measurements over the open-ocean and coastal zone. We also present the initial results from the project, including: Key findings from a review of the current "state-of-the-art" for SAR altimetry, Specification of the initial "reference" delay-Doppler and echo modelling /retracking processing schemes, Evaluation of the initial Test Data Set in the Open Ocean and Coastal Zone Overview of modifications planned to the reference delay-Doppler and echo modelling/ re-tracking processing schemes.

Life-cycle modification in open oceans accounts for genome variability in a cosmopolitan phytoplankton.

PubMed

von Dassow, Peter; John, Uwe; Ogata, Hiroyuki; Probert, Ian; Bendif, El Mahdi; Kegel, Jessica U; Audic, Stéphane; Wincker, Patrick; Da Silva, Corinne; Claverie, Jean-Michel; Doney, Scott; Glover, David M; Flores, Daniella Mella; Herrera, Yeritza; Lescot, Magali; Garet-Delmas, Marie-José; de Vargas, Colomban

2015-06-01

Emiliania huxleyi is the most abundant calcifying plankton in modern oceans with substantial intraspecific genome variability and a biphasic life cycle involving sexual alternation between calcified 2N and flagellated 1N cells. We show that high genome content variability in Emiliania relates to erosion of 1N-specific genes and loss of the ability to form flagellated cells. Analysis of 185 E. huxleyi strains isolated from world oceans suggests that loss of flagella occurred independently in lineages inhabiting oligotrophic open oceans over short evolutionary timescales. This environmentally linked physiogenomic change suggests life cycling is not advantageous in very large/diluted populations experiencing low biotic pressure and low ecological variability. Gene loss did not appear to reflect pressure for genome streamlining in oligotrophic oceans as previously observed in picoplankton. Life-cycle modifications might be common in plankton and cause major functional variability to be hidden from traditional taxonomic or molecular markers.

Major hydrogeochemical processes in an acid mine drainage affected estuary.

PubMed

Asta, Maria P; Calleja, Maria Ll; Pérez-López, Rafael; Auqué, Luis F

2015-02-15

This study provides geochemical data with the aim of identifying and quantifying the main processes occurring in an Acid Mine Drainage (AMD) affected estuary. With that purpose, water samples of the Huelva estuary were collected during a tidal half-cycle and ion-ion plots and geochemical modeling were performed to obtain a general conceptual model. Modeling results indicated that the main processes responsible for the hydrochemical evolution of the waters are: (i) the mixing of acid fluvial water with alkaline ocean water; (ii) precipitation of Fe oxyhydroxysulfates (schwertmannite) and hydroxides (ferrihydrite); (iii) precipitation of Al hydroxysulfates (jurbanite) and hydroxides (amorphous Al(OH)3); (iv) dissolution of calcite; and (v) dissolution of gypsum. All these processes, thermodynamically feasible in the light of their calculated saturation states, were quantified by mass-balance calculations and validated by reaction-path calculations. In addition, sorption processes were deduced by the non-conservative behavior of some elements (e.g., Cu and Zn). Copyright © 2014 Elsevier Ltd. All rights reserved.

A Possible Late Paleocene-Early Eocene Ocean Acidification Event Recoded in the Adriatic Carbonate Platform

NASA Astrophysics Data System (ADS)

Weiss, A.; Martindale, R. C.; Kosir, A.; Oefinger, J.

2017-12-01

The Paleocene-Eocene Thermal Maximum (PETM) event ( 56.3 Ma) was a period of massive carbon release into the Earth system, resulting in significant shifts in ocean chemistry. It has been proposed that ocean acidification - a decrease in the pH and carbonate saturation state of the water as a result of dissolved carbon dioxide in sea water - occurred in both the shallow and deep marine realms. Ocean acidification would have had a devastating impact on the benthic ecosystem, and has been proposed as the cause of decreased carbonate deposition in marine sections and coral reef collapse during the late Paleocene. To date, however, the only physical evidence of Paleocene-Eocene ocean acidification has been shown for offshore sites (i.e., a shallow carbonate compensation depth), but isotope analysis (i.e. B, I/Ca) suggests that acidification occurred in the shallow shelves as well. Several sites in the Kras region of Slovenia, has been found to contain apparent erosion surfaces coeval with the Paleocene-Eocene Boundary. We have investigated these potentially acidified horizons using petrography, stable carbon isotopes, cathodoluminescence, and elemental mapping. These datasets will inform whether the horizons formed by seafloor dissolution in an acidified ocean, or are due to subaerial exposure, or burial diagenesis (i.e. stylotization). Physical erosion and diagenesis can easily be ruled out based on field relationships and petrography, but the other potential causes must be analyzed more critically.

LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4

NASA Astrophysics Data System (ADS)

Zeebe, R. E.

2012-01-01

The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

Polaro–cryptic mirror of the lookdown as a biological model for open ocean camouflage

PubMed Central

Brady, Parrish C.; Travis, Kort A.; Maginnis, Tara; Cummings, Molly E.

2013-01-01

With no object to hide behind in 3D space, the open ocean represents a challenging environment for camouflage. Conventional strategies for reflective crypsis (e.g., standard mirror) are effective against axially symmetric radiance fields associated with high solar altitudes, yet ineffective against asymmetric polarized radiance fields associated with low solar inclinations. Here we identify a biological model for polaro–crypsis. We measured the surface-reflectance Mueller matrix of live open ocean fish (lookdown, Selene vomer) and seagrass-dwelling fish (pinfish, Lagodon rhomboides) using polarization-imaging and modeling polarization camouflage for the open ocean. Lookdowns occupy the minimization basin of our polarization-contrast space, while pinfish and standard mirror measurements exhibit higher contrast values than optimal. The lookdown reflective strategy achieves significant gains in polaro–crypsis (up to 80%) in comparison with nonpolarization sensitive strategies, such as a vertical mirror. Lookdowns achieve polaro–crypsis across solar altitudes by varying reflective properties (described by 16 Mueller matrix elements mij) with incident illumination. Lookdowns preserve reflected polarization aligned with principle axes (dorsal–ventral and anterior–posterior, m22 = 0.64), while randomizing incident polarization 45° from principle axes (m33 = –0.05). These reflectance properties allow lookdowns to reflect the uniform degree and angle of polarization associated with high-noon conditions due to alignment of the principle axes and the sun, and reflect a more complex polarization pattern at asymmetrical light fields associated with lower solar elevations. Our results suggest that polaro–cryptic strategies vary by habitat, and require context-specific depolarization and angle alteration for effective concealment in the complex open ocean environment. PMID:23716701

The study of aluminium anodes for high power density Al/air batteries with brine electrolytes

NASA Astrophysics Data System (ADS)

Nestoridi, Maria; Pletcher, Derek; Wood, Robert J. K.; Wang, Shuncai; Jones, Richard L.; Stokes, Keith R.; Wilcock, Ian

Aluminium alloys containing small additions of both tin (∼0.1 wt%) and gallium (∼0.05 wt%) are shown to dissolve anodically at high rates in sodium chloride media at room temperatures; current densities >0.2 A cm -2 can be obtained at potentials close to the open circuit potential, ∼-1500 mV versus SCE. The tin exists in the alloys as a second phase, typically as ∼1 μm inclusions (precipitates) distributed throughout the aluminium structure, and anodic dissolution occurs to form pits around the tin inclusions. Although the distribution of the gallium in the alloy could not be established, it is also shown to be critical in the formation of these pits as well as maintaining their activity. The stability of the alloys to open circuit corrosion and the overpotential for high rate dissolution, both critical to battery performance, are shown to depend on factors in addition to elemental composition; both heat treatment and mechanical working influence the performance of the alloy. The correlation between alloy performance and their microstructure has been investigated.

Ocean Acidification Effects on Atlantic Cod Larval Survival and Recruitment to the Fished Population

PubMed Central

Stiasny, Martina H.; Mittermayer, Felix H.; Sswat, Michael; Voss, Rüdiger; Jutfelt, Fredrik; Chierici, Melissa; Puvanendran, Velmurugu; Mortensen, Atle; Reusch, Thorsten B. H.; Clemmesen, Catriona

2016-01-01

How fisheries will be impacted by climate change is far from understood. While some fish populations may be able to escape global warming via range shifts, they cannot escape ocean acidification (OA), an inevitable consequence of the dissolution of anthropogenic carbon dioxide (CO2) emissions in marine waters. How ocean acidification affects population dynamics of commercially important fish species is critical for adapting management practices of exploited fish populations. Ocean acidification has been shown to impair fish larvae’s sensory abilities, affect the morphology of otoliths, cause tissue damage and cause behavioural changes. Here, we obtain first experimental mortality estimates for Atlantic cod larvae under OA and incorporate these effects into recruitment models. End-of-century levels of ocean acidification (~1100 μatm according to the IPCC RCP 8.5) resulted in a doubling of daily mortality rates compared to present-day CO2 concentrations during the first 25 days post hatching (dph), a critical phase for population recruitment. These results were consistent under different feeding regimes, stocking densities and in two cod populations (Western Baltic and Barents Sea stock). When mortality data were included into Ricker-type stock-recruitment models, recruitment was reduced to an average of 8 and 24% of current recruitment for the two populations, respectively. Our results highlight the importance of including vulnerable early life stages when addressing effects of climate change on fish stocks. PMID:27551924

Ocean Acidification Effects on Atlantic Cod Larval Survival and Recruitment to the Fished Population.

PubMed

Stiasny, Martina H; Mittermayer, Felix H; Sswat, Michael; Voss, Rüdiger; Jutfelt, Fredrik; Chierici, Melissa; Puvanendran, Velmurugu; Mortensen, Atle; Reusch, Thorsten B H; Clemmesen, Catriona

2016-01-01

How fisheries will be impacted by climate change is far from understood. While some fish populations may be able to escape global warming via range shifts, they cannot escape ocean acidification (OA), an inevitable consequence of the dissolution of anthropogenic carbon dioxide (CO2) emissions in marine waters. How ocean acidification affects population dynamics of commercially important fish species is critical for adapting management practices of exploited fish populations. Ocean acidification has been shown to impair fish larvae's sensory abilities, affect the morphology of otoliths, cause tissue damage and cause behavioural changes. Here, we obtain first experimental mortality estimates for Atlantic cod larvae under OA and incorporate these effects into recruitment models. End-of-century levels of ocean acidification (~1100 μatm according to the IPCC RCP 8.5) resulted in a doubling of daily mortality rates compared to present-day CO2 concentrations during the first 25 days post hatching (dph), a critical phase for population recruitment. These results were consistent under different feeding regimes, stocking densities and in two cod populations (Western Baltic and Barents Sea stock). When mortality data were included into Ricker-type stock-recruitment models, recruitment was reduced to an average of 8 and 24% of current recruitment for the two populations, respectively. Our results highlight the importance of including vulnerable early life stages when addressing effects of climate change on fish stocks.

Model-Based Assessment of the CO2 Sequestration Potential of Coastal Ocean Alkalinization

NASA Astrophysics Data System (ADS)

Feng, E. Y.; Koeve, W.; Keller, D. P.; Oschlies, A.

2017-12-01

The potential of coastal ocean alkalinization (COA), a carbon dioxide removal (CDR) climate engineering strategy that chemically increases ocean carbon uptake and storage, is investigated with an Earth system model of intermediate complexity. The CDR potential and possible environmental side effects are estimated for various COA deployment scenarios, assuming olivine as the alkalinity source in ice-free coastal waters (about 8.6% of the global ocean's surface area), with dissolution rates being a function of grain size, ambient seawater temperature, and pH. Our results indicate that for a large-enough olivine deployment of small-enough grain sizes (10 µm), atmospheric CO2 could be reduced by more than 800 GtC by the year 2100. However, COA with coarse olivine grains (1000 µm) has little CO2 sequestration potential on this time scale. Ambitious CDR with fine olivine grains would increase coastal aragonite saturation Ω to levels well beyond those that are currently observed. When imposing upper limits for aragonite saturation levels (Ωlim) in the grid boxes subject to COA (Ωlim = 3.4 and 9 chosen as examples), COA still has the potential to reduce atmospheric CO2 by 265 GtC (Ωlim = 3.4) to 790 GtC (Ωlim = 9) and increase ocean carbon storage by 290 Gt (Ωlim = 3.4) to 913 Gt (Ωlim = 9) by year 2100.

Coupled alkali feldspar dissolution and secondary mineral precipitation in batch systems: 4. Numerical modeling of kinetic reaction paths

NASA Astrophysics Data System (ADS)

Zhu, Chen; Lu, Peng; Zheng, Zuoping; Ganor, Jiwchar

2010-07-01

This paper explores how dissolution and precipitation reactions are coupled in batch reactor experimental systems at elevated temperatures. This is the fourth paper in our series of "Coupled Alkali Feldspar Dissolution and Secondary Mineral Precipitation in Batch Systems". In our third paper, we demonstrated via speciation-solubility modeling that partial equilibrium between secondary minerals and aqueous solutions was not attained in feldspar hydrolysis batch reactors at 90-300 °C and that a strong coupling between dissolution and precipitation reactions follows as a consequence of the slower precipitation of secondary minerals ( Zhu and Lu, 2009). Here, we develop this concept further by using numerical reaction path models to elucidate how the dissolution and precipitation reactions are coupled. Modeling results show that a quasi-steady state was reached. At the quasi-steady state, dissolution reactions proceeded at rates that are orders of magnitude slower than the rates measured at far from equilibrium. The quasi-steady state is determined by the relative rate constants, and strongly influenced by the function of Gibbs free energy of reaction ( ΔG) in the rate laws. To explore the potential effects of fluid flow rates on the coupling of reactions, we extrapolate a batch system ( Ganor et al., 2007) to open systems and simulated one-dimensional reactive mass transport for oligoclase dissolution and kaolinite precipitation in homogeneous porous media. Different steady states were achieved at different locations along the one-dimensional domain. The time-space distribution and saturation indices (SI) at the steady states were a function of flow rates for a given kinetic model. Regardless of the differences in SI, the ratio between oligoclase dissolution rates and kaolinite precipitation rates remained 1.626, as in the batch system case ( Ganor et al., 2007). Therefore, our simulation results demonstrated coupling among dissolution, precipitation, and flow rates. Results reported in this communication lend support to our hypothesis that slow secondary mineral precipitation explains part of the well-known apparent discrepancy between lab measured and field estimated feldspar dissolution rates ( Zhu et al., 2004). Here we show how the slow secondary mineral precipitation provides a regulator to explain why the systems are held close to equilibrium and show how the most often-quoted "near equilibrium" explanation for an apparent field-lab discrepancy can work quantitatively. The substantiated hypothesis now offers the promise of reconciling part of the apparent field-lab discrepancy.

Sources of reactive nitrogen in marine aerosol over the Northwest Pacific Ocean in spring

NASA Astrophysics Data System (ADS)

Luo, Li; Kao, Shuh-Ji; Bao, Hongyan; Xiao, Huayun; Xiao, Hongwei; Yao, Xiaohong; Gao, Huiwang; Li, Jiawei; Lu, Yangyang

2018-05-01

Atmospheric deposition of long-range transport of anthropogenic reactive nitrogen (Nr, mainly comprised of NHx, NOy and water-soluble organic nitrogen, WSON) from continents may have profound impact on marine biogeochemistry. In addition, surface ocean dissolved organic nitrogen (DON) may also contribute to aerosol WSON in the overlying atmosphere. Despite the importance of off-continent dispersion and Nr interactions at the atmosphere-ocean boundary, our knowledge of the sources of various nitrogen species in the atmosphere over the open ocean remains limited due to insufficient observations. We conducted two cruises in the spring of 2014 and 2015 from the coast of China through the East China seas (ECSs, i.e. the Yellow Sea and East China Sea) to the open ocean (i.e. the Northwest Pacific Ocean, NWPO). Concentrations of water-soluble total nitrogen (WSTN), NO3- and NH4+, as well as the δ15N of WSTN and NO3- in marine aerosol, were measured during both cruises. In the spring of 2015, we also analysed the concentrations and δ15N of NO3- and the DON of surface seawater (SSW; at a depth of 5 m) along the cruise track. Aerosol NO3-, NH4+ and WSON decreased logarithmically (1-2 orders of magnitude) with distance from the shore, reflecting strong anthropogenic emission sources of NO3-, NH4+ and WSON in China. Average aerosol NO3- and NH4+ concentrations were significantly higher in 2014 (even in the remote NWOP) than in 2015 due to the stronger wind field in 2014, underscoring the role of the Asian winter monsoon in the seaward transport of anthropogenic NO3- and NH4+. However, the background aerosol WSON over the NWPO in 2015 (13.3 ± 8.5 nmol m-3) was similar to that in 2014 (12.2 ± 6.3 nmol m-3), suggesting an additional non-anthropogenic WSON source in the open ocean. Obviously, marine DON emissions should be considered in model and field assessments of net atmospheric WSON deposition in the open ocean. This study contributes information on parallel isotopic marine DON composition and aerosol Nr datasets, but more research is required to explore complex Nr sources and deposition processes in order to advance our understanding of anthropogenic influences on the marine nitrogen cycle and nitrogen exchange at land-ocean and atmosphere-ocean interfaces.

Chemical and biological impacts of ocean acidification along the west coast of North America

NASA Astrophysics Data System (ADS)

Feely, Richard A.; Alin, Simone R.; Carter, Brendan; Bednaršek, Nina; Hales, Burke; Chan, Francis; Hill, Tessa M.; Gaylord, Brian; Sanford, Eric; Byrne, Robert H.; Sabine, Christopher L.; Greeley, Dana; Juranek, Lauren

2016-12-01

The continental shelf region off the west coast of North America is seasonally exposed to water with a low aragonite saturation state by coastal upwelling of CO2-rich waters. To date, the spatial and temporal distribution of anthropogenic CO2 (Canth) within the CO2-rich waters is largely unknown. Here we adapt the multiple linear regression approach to utilize the GO-SHIP Repeat Hydrography data from the northeast Pacific to establish an annually updated relationship between Canth and potential density. This relationship was then used with the NOAA Ocean Acidification Program West Coast Ocean Acidification (WCOA) cruise data sets from 2007, 2011, 2012, and 2013 to determine the spatial variations of Canth in the upwelled water. Our results show large spatial differences in Canth in surface waters along the coast, with the lowest values (37-55 μmol kg-1) in strong upwelling regions off southern Oregon and northern California and higher values (51-63 μmol kg-1) to the north and south of this region. Coastal dissolved inorganic carbon concentrations are also elevated due to a natural remineralized component (Cbio), which represents carbon accumulated through net respiration in the seawater that has not yet degassed to the atmosphere. Average surface Canth is almost twice the surface remineralized component. In contrast, Canth is only about one third and one fifth of the remineralized component at 50 m and 100 m depth, respectively. Uptake of Canth has caused the aragonite saturation horizon to shoal by approximately 30-50 m since the preindustrial period so that undersaturated waters are well within the regions of the continental shelf that affect the shell dissolution of living pteropods. Our data show that the most severe biological impacts occur in the nearshore waters, where corrosive waters are closest to the surface. Since the pre-industrial times, pteropod shell dissolution has, on average, increased approximately 19-26% in both nearshore and offshore waters.

76 FR 27019 - Interagency Ocean Observation Committee, Meeting of the Data Management and Communications...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-10

... Observation Committee, Meeting of the Data Management and Communications Steering Team AGENCY: National Ocean...). ACTION: Notice of open meeting. SUMMARY: NOAA's Integrated Ocean Observing System (IOOS) Program... meeting of the IOOC's Data Management and Communications Steering Team (DMAC-ST). The DMAC-ST membership...

78 FR 46932 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-02

... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research Advisory Panel (ORAP..., Office of Naval Research, 875 North Randolph Street, Suite 1425, Arlington, VA 22203- 1995, telephone 703...

PCDDs, PCDFs, and coplanar PCBs in albatross from the North Pacific and Southern Oceans: levels, patterns, and toxicological implications.

PubMed

Tanabe, Shinsuke; Watanabe, Mafumi; Minh, Tu Binh; Kunisue, Tatsuya; Nakanishi, Shigeyuki; Ono, Hitoshi; Tanaka, Hiroyuki

2004-01-15

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) were determined in five albatross species collected from the North Pacific and Southern Oceans to assess the north-south differences in residue levels, accumulation patterns, and toxic potential. Black-footed and Laysan albatrosses from the North Pacific Ocean contained higher levels of PCDD/Fs and coplanar PCBs than albatrosses from the Southern Ocean, indicating that emission sources of these contaminants were predominant in the northern hemisphere. Residue levels in albatrosses from the remote North Pacific Ocean far from the point source of pollution were comparable to or higher than those in terrestrial and coastal birds from contaminated areas in developed nations, suggesting the specific exposure and accumulation of PCDD/Fs and coplanar PCBs in albatross. The long life span and ingestion of plastic resin pellets by albatrosses could be the plausible explanations for the elevated accumulation of persistent and lipophilic contaminants including PCDD/Fs and coplanar PCBs in these birds. Relative proportions of PCDFs and coplanar PCBs in albatross were higher than those observed in birds inhabiting terrestrial and coastal areas, suggesting that these toxic chemicals may have higher transportability by air and water than PCDDs. Congener patterns of PCDD/Fs in albatross showed less variability as compared to those in terrestrial species, indicating that contamination patterns of PCDD/Fs were similar within the open ocean environment. Contributions of PCDD/Fs to total TEQs in albatrosses from the open ocean were generally lower than those in terrestrial birds, suggesting different toxic potency of PCDD/Fs and coplanar PCBs on animals inhabiting open ocean and terrestrial environment. Whereas albatrosses from southern oceans retained lower TEQ concentrations, possible adverse effects of PCDD/Fs and coplanar PCBs to black-footed and Laysan albatrosses of the North Pacific Ocean may be suspected from TEQ levels.

Skipjack tuna as a bioindicator of contamination by perfluorinated compounds in the oceans.

PubMed

Hart, Kimberly; Kannan, Kurunthachalam; Tao, Lin; Takahashi, Shin; Tanabe, Shinsuke

2008-09-15

Perfluorinated chemicals (PFCs) have emerged as global environmental contaminants. Studies have reported the widespread occurrence of PFCs in biota from marine coastal waters and in remote polar regions. However, few studies have reported the distribution of PFCs in biota from offshore waters and open oceans. In this study, concentrations of nine PFCs were determined in the livers of 60 skipjack tuna (Katsuwonus pelamis) collected from offshore waters and the open ocean along the Pacific Rim, including the Sea of Japan, the East China Sea, the Indian Ocean, and the Western North Pacific Ocean, during 1997-1999. At least one of the nine PFCs was found in every tuna sample analyzed. Overall, perfluorooctanesulfonate (PFOS) and perfluoroundecanoic acid (PFUnDA) were the predominant compounds found in livers of tuna at concentrations of <1-58.9 and <1-31.6 ng/g, wet wt, respectively. Long-chain perfluorocarboxylates such as perfluorodecanoic acid (PFDA) and perfluorododecanoic acid (PFDoDA) were common in the tuna livers. In livers of tuna from several offshore and open-ocean locations, concentrations of PFUnDA were greater than the concentrations of PFOS. The profiles and concentrations of PFCs in tuna livers suggest that the sources in East Asia are dominated by long-chain perfluorocarboxylates, especially PFUnDA. High concentrations of PFUnDA in tuna may indicate a shift in sources of PFCs in East Asia. The spatial distribution of PFOS in skipjack tuna reflected the concentrations previously reported in seawater samples from the Pacific and Indian Oceans, suggesting that tuna are good bioindicators of pollution by PFOS. Despite its predominance in ocean waters, PFOA was rarely found in tuna livers, indicative of the low bioaccumulation potential of this compound. Our study establishes baseline concentrations of PFCs in skipjack tuna from the oceans of the Asia-Pacific region, enabling future temporal trend studies of PFCs in oceans.

Impacts of atmospheric anthropogenic nitrogen on the open ocean.

PubMed

Duce, R A; LaRoche, J; Altieri, K; Arrigo, K R; Baker, A R; Capone, D G; Cornell, S; Dentener, F; Galloway, J; Ganeshram, R S; Geider, R J; Jickells, T; Kuypers, M M; Langlois, R; Liss, P S; Liu, S M; Middelburg, J J; Moore, C M; Nickovic, S; Oschlies, A; Pedersen, T; Prospero, J; Schlitzer, R; Seitzinger, S; Sorensen, L L; Uematsu, M; Ulloa, O; Voss, M; Ward, B; Zamora, L

2008-05-16

Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.

Source and sink of fluid in pelagic siliceous sediments along a cold subduction plate boundary

NASA Astrophysics Data System (ADS)

Yamaguchi, Asuka; Hina, Shoko; Hamada, Yohei; Kameda, Jun; Hamahashi, Mari; Kuwatani, Tatsu; Shimizu, Mayuko; Kimura, Gaku

2016-08-01

Subduction zones where old oceanic plate underthrusting occurs are characterized by thick pelagic sediments originating from planktonic ooze as well as cold thermal conditions. For a better understanding of dehydration from pelagic sediments and fluid behavior, which would play a key role in controlling the dynamics in the shallow portion of the subduction zone, as observed in the 2011 Tohoku earthquake and tsunami, we investigate cherts in a Jurassic accretionary complex in Japan. The microstructure and microchemistry of these cherts indicate dissolution of SiO2 from a pressure solution seam and precipitation of SiO2 to the ;white chert layer,; which would act as a fluid conduit. The amount of water necessary to precipitate SiO2 in the white chert is 102 times larger than that produced by compaction and silica/clay diagenesis. Other fluid sources, such as hydrated oceanic crust or oceanic mantle, are necessary to account for this discrepancy in the fluid budget. A large amount of external fluid likely contributed to rising pore pressure along cold plate boundaries.

Humboldt Open Ocean Disposal Site (HOODS) Survey Work 2014

EPA Pesticide Factsheets

The Humboldt Open Ocean Disposal Site (HOODS) is a dredged material disposal site located 3 nautical miles (nm) offshore of Humboldt Bay in Northern California. HOODS was permanently designated by EPA Region 9 in 1995, and has been actively used for dredged material disposal operations since then. The HOODS has received higher volumes of dredged material than predicted since its designation in 1995, mainly from USACE construction and maintenance dredging.

Interoperable Data Access Services for NOAA IOOS

NASA Astrophysics Data System (ADS)

de La Beaujardiere, J.

2008-12-01

The Integrated Ocean Observing System (IOOS) is intended to enhance our ability to collect, deliver, and use ocean information. The goal is to support research and decision-making by providing data on our open oceans, coastal waters, and Great Lakes in the formats, rates, and scales required by scientists, managers, businesses, governments, and the public. The US National Oceanic and Atmospheric Administration (NOAA) is the lead agency for IOOS. NOAA's IOOS office supports the development of regional coastal observing capability and promotes data management efforts to increase data accessibility. Geospatial web services have been established at NOAA data providers including the National Data Buoy Center (NDBC), the Center for Operational Oceanographic Products and Services (CO-OPS), and CoastWatch, and at regional data provider sites. Services established include Open-source Project for a Network Data Access Protocol (OpenDAP), Open Geospatial Consortium (OGC) Sensor Observation Service (SOS), and OGC Web Coverage Service (WCS). These services provide integrated access to data holdings that have been aggregated at each center from multiple sources. We wish to collaborate with other groups to improve our service offerings to maximize interoperability and enhance cross-provider data integration, and to share common service components such as registries, catalogs, data conversion, and gateways. This paper will discuss the current status of NOAA's IOOS efforts and possible next steps.

Deep winter convection and phytoplankton dynamics in the NW Mediterranean Sea under present climate and future (horizon 2030) scenarios.

PubMed

Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

2018-04-26

Deep water convection (DC) in winter is one of the major processes driving open-ocean primary productivity in the Northwestern Mediterranean Sea. DC is highly variable in time, depending on the specific conditions (stratification, circulation and ocean-atmosphere interactions) of each specific winter. This variability also drives the interannual oscillations of open-ocean primary productivity in this important region for many commercially-important fish species. We use a coupled model system to 1) understand to what extent DC impacts phytoplankton seasonality in the present-day and 2) to explore potential changes in future scenarios (~2030). Our model represents quite accurately the present-day characteristics of DC and its importance for open-ocean phytoplankton blooms. However, for the future scenarios the importance of deep nutrients in fertilizing the euphotic layer of the NW Mediterranean decreases. The model simulates changes in surface density and on the levels of kinetic energy that make mesoscale activity associated with horizontal currents to become a more important fertilization mechanism, inducing subsequently phenological changes in seasonal plankton cycles. Because of our focus on the open-sea, an exact quantification of the impact of those changes on the overall biological production of the NW Mediterranean cannot be made at the moment.

Olfaction and topography, but not magnetic cues, control navigation in a pelagic seabird: displacements with shearwaters in the Mediterranean Sea

PubMed Central

Pollonara, Enrica; Luschi, Paolo; Guilford, Tim; Wikelski, Martin; Bonadonna, Francesco; Gagliardo, Anna

2015-01-01

Pelagic seabirds wander the open oceans then return accurately to their habitual nest-sites. We investigated the effects of sensory manipulation on oceanic navigation in Scopoli’s shearwaters (Calonectris diomedea) breeding at Pianosa island (Italy), by displacing them 400 km from their colony and tracking them. A recent experiment on Atlantic shearwaters (Cory’s shearwater, Calonectris borealis) breeding in the Azores indicated a crucial role of olfaction over the open ocean, but left open the question of whether birds might navigate by topographical landmark cues when available. Our experiment was conducted in the Mediterranean sea, where the availability of topographical cues may provide an alternative navigational mechanism for homing. Magnetically disturbed shearwaters and control birds oriented homeward even when the coast was not visible and rapidly homed. Anosmic shearwaters oriented in a direction significantly different from the home direction when in open sea. After having approached a coastline their flight path changed from convoluted to homeward oriented, so that most of them eventually reached home. Beside confirming that magnetic cues appear unimportant for oceanic navigation by seabirds, our results support the crucial role of olfactory cues for birds’ navigation and reveal that anosmic shearwaters are able to home eventually by following coastal features. PMID:26548946

Manifestation, Drivers, and Emergence of Open Ocean Deoxygenation.

PubMed

Levin, Lisa A

2018-01-03

Oxygen loss in the ocean, termed deoxygenation, is a major consequence of climate change and is exacerbated by other aspects of global change. An average global loss of 2% or more has been recorded in the open ocean over the past 50-100 years, but with greater oxygen declines in intermediate waters (100-600 m) of the North Pacific, the East Pacific, tropical waters, and the Southern Ocean. Although ocean warming contributions to oxygen declines through a reduction in oxygen solubility and stratification effects on ventilation are reasonably well understood, it has been a major challenge to identify drivers and modifying factors that explain different regional patterns, especially in the tropical oceans. Changes in respiration, circulation (including upwelling), nutrient inputs, and possibly methane release contribute to oxygen loss, often indirectly through stimulation of biological production and biological consumption. Microbes mediate many feedbacks in oxygen minimum zones that can either exacerbate or ameliorate deoxygenation via interacting nitrogen, sulfur, and carbon cycles. The paleo-record reflects drivers of and feedbacks to deoxygenation that have played out through the Phanerozoic on centennial, millennial, and hundred-million-year timescales. Natural oxygen variability has made it difficult to detect the emergence of a climate-forced signal of oxygen loss, but new modeling efforts now project emergence to occur in many areas in 15-25 years. Continued global deoxygenation is projected for the next 100 or more years under most emissions scenarios, but with regional heterogeneity. Notably, even small changes in oxygenation can have significant biological effects. New efforts to systematically observe oxygen changes throughout the open ocean are needed to help address gaps in understanding of ocean deoxygenation patterns and drivers.

The sources of Antarctic bottom water in a global ice ocean model

NASA Astrophysics Data System (ADS)

Goosse, Hugues; Campin, Jean-Michel; Tartinville, Benoı̂t

Two mechanisms contribute to the formation of Antarctic bottom water (AABW). The first, and probably the most important, is initiated by the brine released on the Antarctic continental shelf during ice formation which is responsible for an increase in salinity. After mixing with ambient water at the shelf break, this salty and dense water sinks along the shelf slope and invades the deepest part of the global ocean. For the second one, the increase of surface water density is due to strong cooling at the ocean-atmosphere interface, together with a contribution from brine release. This induces deep convection and the renewal of deep waters. The relative importance of these two mechanisms is investigated in a global coupled ice-ocean model. Chlorofluorocarbon (CFC) concentrations simulated by the model compare favourably with observations, suggesting a reasonable deep water ventilation in the Southern Ocean, except close to Antarctica where concentrations are too high. Two artificial passive tracers released at surface on the Antarctic continental shelf and in the open-ocean allow to show clearly that the two mechanisms contribute significantly to the renewal of AABW in the model. This indicates that open-ocean convection is overestimated in our simulation. Additional experiments show that the amount of AABW production due to the export of dense shelf waters is quite sensitive to the parameterisation of the effect of downsloping and meso-scale eddies. Nevertheless, shelf waters always contribute significantly to deep water renewal. Besides, increasing the P.R. Gent, J.C. McWilliams [Journal of Physical Oceanography 20 (1990) 150-155] thickness diffusion can nearly suppress the AABW formation by open-ocean convection.

Manifestation, Drivers, and Emergence of Open Ocean Deoxygenation

NASA Astrophysics Data System (ADS)

Levin, Lisa A.

2018-01-01

Oxygen loss in the ocean, termed deoxygenation, is a major consequence of climate change and is exacerbated by other aspects of global change. An average global loss of 2% or more has been recorded in the open ocean over the past 50-100 years, but with greater oxygen declines in intermediate waters (100-600 m) of the North Pacific, the East Pacific, tropical waters, and the Southern Ocean. Although ocean warming contributions to oxygen declines through a reduction in oxygen solubility and stratification effects on ventilation are reasonably well understood, it has been a major challenge to identify drivers and modifying factors that explain different regional patterns, especially in the tropical oceans. Changes in respiration, circulation (including upwelling), nutrient inputs, and possibly methane release contribute to oxygen loss, often indirectly through stimulation of biological production and biological consumption. Microbes mediate many feedbacks in oxygen minimum zones that can either exacerbate or ameliorate deoxygenation via interacting nitrogen, sulfur, and carbon cycles. The paleo-record reflects drivers of and feedbacks to deoxygenation that have played out through the Phanerozoic on centennial, millennial, and hundred-million-year timescales. Natural oxygen variability has made it difficult to detect the emergence of a climate-forced signal of oxygen loss, but new modeling efforts now project emergence to occur in many areas in 15-25 years. Continued global deoxygenation is projected for the next 100 or more years under most emissions scenarios, but with regional heterogeneity. Notably, even small changes in oxygenation can have significant biological effects. New efforts to systematically observe oxygen changes throughout the open ocean are needed to help address gaps in understanding of ocean deoxygenation patterns and drivers.

CryoSat Plus For Oceans: an ESA Project for CryoSat-2 Data Exploitation Over Ocean

NASA Astrophysics Data System (ADS)

Benveniste, J.; Cotton, D.; Clarizia, M.; Roca, M.; Gommenginger, C. P.; Naeije, M. C.; Labroue, S.; Picot, N.; Fernandes, J.; Andersen, O. B.; Cancet, M.; Dinardo, S.; Lucas, B. M.

2012-12-01

The ESA CryoSat-2 mission is the first space mission to carry a space-borne radar altimeter that is able to operate in the conventional pulsewidth-limited (LRM) mode and in the novel Synthetic Aperture Radar (SAR) mode. Although the prime objective of the Cryosat-2 mission is dedicated to monitoring land and marine ice, the SAR mode capability of the Cryosat-2 SIRAL altimeter also presents the possibility of demonstrating significant potential benefits of SAR altimetry for ocean applications, based on expected performance enhancements which include improved range precision and finer along track spatial resolution. With this scope in mind, the "CryoSat Plus for Oceans" (CP4O) Project, dedicated to the exploitation of CryoSat-2 Data over ocean, supported by the ESA STSE (Support To Science Element) programme, brings together an expert European consortium comprising: DTU Space, isardSAT, National Oceanography Centre , Noveltis, SatOC, Starlab, TU Delft, the University of Porto and CLS (supported by CNES),. The objectives of CP4O are: - to build a sound scientific basis for new scientific and operational applications of Cryosat-2 data over the open ocean, polar ocean, coastal seas and for sea-floor mapping. - to generate and evaluate new methods and products that will enable the full exploitation of the capabilities of the Cryosat-2 SIRAL altimeter , and extend their application beyond the initial mission objectives. - to ensure that the scientific return of the Cryosat-2 mission is maximised. In particular four themes will be addressed: -Open Ocean Altimetry: Combining GOCE Geoid Model with CryoSat Oceanographic LRM Products for the retrieval of CryoSat MSS/MDT model over open ocean surfaces and for analysis of mesoscale and large scale prominent open ocean features. Under this priority the project will also foster the exploitation of the finer resolution and higher SNR of novel CryoSat SAR Data to detect short spatial scale open ocean features. -High Resolution Polar Ocean Altimetry: Combination of GOCE Geoid Model with CryoSat Oceanographic SAR Products over polar oceans for the retrieval of CryoSat MSS/MDT and currents circulations system improving the polar tides models and studying the coupling between blowing wind and current pattern. -High Resolution Coastal Zone Altimetry: Exploitation of the finer resolution and higher SNR of novel CryoSat SAR Data to get the radar altimetry closer to the shore exploiting the SARIn mode for the discrimination of off-nadir land targets (e.g. steep cliffs) in the radar footprint from nadir sea return. -High Resolution Sea-Floor Altimetry: Exploitation of the finer resolution and higher SNR of novel CryoSat SAR Data to resolve the weak short-wavelength sea surface signals caused by sea-floor topography elements and to map uncharted sea-mounts/trenches. One of the first project activities is the consolidation of preliminary scientific requirements for the four themes under investigation. This paper will present the CP4O project content and objectives and will address the first initial results from the on-going work to define the scientific requirements.

Charting the Course for Ocean Science in the United States for the Next Decade: An Ocean Research Priorities Plan and Implementation Strategy

DTIC Science & Technology

2007-01-26

ocean affects calcifying organisms, such as corals , with significant effects to reefs , the ecosystems they support, and their ability to pro- tect...water coral reefs , to open- ocean systems. For example, increasing ocean acidity, altered biogeochemistry, changing current patterns, loss of sea ice...for example, large swings in the populations of commercial fisheries, changes in seabird-population distributions, and coral - reef -bleaching events

Global biogeochemical implications of mercury discharges from rivers and sediment burial.

PubMed

Amos, Helen M; Jacob, Daniel J; Kocman, David; Horowitz, Hannah M; Zhang, Yanxu; Dutkiewicz, Stephanie; Horvat, Milena; Corbitt, Elizabeth S; Krabbenhoft, David P; Sunderland, Elsie M

2014-08-19

Rivers are an important source of mercury (Hg) to marine ecosystems. Based on an analysis of compiled observations, we estimate global present-day Hg discharges from rivers to ocean margins are 27 ± 13 Mmol a(-1) (5500 ± 2700 Mg a(-1)), of which 28% reaches the open ocean and the rest is deposited to ocean margin sediments. Globally, the source of Hg to the open ocean from rivers amounts to 30% of atmospheric inputs. This is larger than previously estimated due to accounting for elevated concentrations in Asian rivers and variability in offshore transport across different types of estuaries. Riverine inputs of Hg to the North Atlantic have decreased several-fold since the 1970s while inputs to the North Pacific have increased. These trends have large effects on Hg concentrations at ocean margins but are too small in the open ocean to explain observed declines of seawater concentrations in the North Atlantic or increases in the North Pacific. Burial of Hg in ocean margin sediments represents a major sink in the global Hg biogeochemical cycle that has not been previously considered. We find that including this sink in a fully coupled global biogeochemical box model helps to balance the large anthropogenic release of Hg from commercial products recently added to global inventories. It also implies that legacy anthropogenic Hg can be removed from active environmental cycling on a faster time scale (centuries instead of millennia). Natural environmental Hg levels are lower than previously estimated, implying a relatively larger impact from human activity.

An Integrative Approach to Understand a Rich Ecosystem in the Southern Ocean From Carbon to Top Predators

NASA Astrophysics Data System (ADS)

Cotté, C.; d'Ovidio, F.; Behagle, N.; Roudaut, G.; Brehmer, P.; Bost, C. A.; Guinet, C.; Cherel, Y.

2016-02-01

Large parts of the Southern Ocean waters are rich in macronutrients, but blooms of phytoplankton occur in a patchy and localized way. This is in part due to the presence of sources of limiting micronutrients scattered along the continental breaks, whose inputs are stirred into the open ocean very inhomogeneously. At the highest levels of ecosystems, top predators reveal areas of ecological importance where no other information is available on the underpinning trophic web. A dramatic example of this situation is provided by the region around Kerguelen archipelago, in the Southern Indian Ocean. Here, the high nutrient, low iron waters transported eastward by the Antarctic Circumpolar Current encounter the iron-rich Kerguelen shelf break. As a consequence, a plume of high chlorophyll water develops east of the plateau, extending from the shelf break for hundreds of kms into the open ocean, and strongly modulated by the intense mesoscale activity. Large populations of top predators use this area to forage during the summer periode, despite very scarce knowledge on their micronektonic prey and on mid-trophic oragnisms. By combining in campaign data, satellite observations, and biologging, we adopt an end-to-end approach and describe the mechanisms by which the ocean physics impacts the regional biogeochemistry firstly by redistributing iron-rich coastal waters into the open ocean, and then by focusing on the trophic interactions. We consider in particular the role of mesoscale eddies and submesoscale fronts, whose temporal dynamics resonates with biological processes and organises the variability of ecosystems.

Millennial-scale iron fertilization of the eastern equatorial Pacific over the past 100,000 years

NASA Astrophysics Data System (ADS)

Loveley, Matthew R.; Marcantonio, Franco; Wisler, Marilyn M.; Hertzberg, Jennifer E.; Schmidt, Matthew W.; Lyle, Mitchell

2017-10-01

The eastern equatorial Pacific Ocean plays a crucial role in global climate, as it is a substantial source of CO2 to the atmosphere and accounts for a significant portion of global new export productivity. Here we present a 100,000-year sediment core from the eastern equatorial Pacific, and reconstruct dust flux, export productivity and bottom-water oxygenation using excess-230Th-derived fluxes of 232Th and barium, and authigenic uranium concentrations, respectively. We find that during the last glacial period (71,000 to 41,000 years ago), increased delivery of dust to the eastern equatorial Pacific was coeval with North Atlantic Heinrich stadial events. Millennial-scale pulses of increased dust flux coincided with episodes of heightened biological productivity, suggesting that dissolution of dust released iron that promoted ocean fertilization. We also find that periods of low atmospheric CO2 concentrations were associated with suboxic conditions and increased storage of respired carbon in the deep eastern equatorial Pacific. Increases in CO2 concentrations during the deglaciation are coincident with increases in deep Pacific and Southern Ocean water oxygenation levels. We suggest that deep-ocean ventilation was a primary control on CO2 outgassing in this region, with superimposed pulses of high productivity providing a negative feedback.

Vulnerability of coral reefs to bioerosion from land-based sources of pollution

USGS Publications Warehouse

Prouty, Nancy G.; Anne Cohen,; Yates, Kimberly K.; Storlazzi, Curt; Swarzenski, Peter W.; White, Darla

2017-01-01

Ocean acidification (OA), the gradual decline in ocean pH and [ ] caused by rising levels of atmospheric CO2, poses a significant threat to coral reef ecosystems, depressing rates of calcium carbonate (CaCO3) production, and enhancing rates of bioerosion and dissolution. As ocean pH and [ ] decline globally, there is increasing emphasis on managing local stressors that can exacerbate the vulnerability of coral reefs to the effects of OA. We show that sustained, nutrient rich, lower pH submarine groundwater discharging onto nearshore coral reefs off west Maui lowers the pH of seawater and exposes corals to nitrate concentrations 50 times higher than ambient. Rates of coral calcification are substantially decreased, and rates of bioerosion are orders of magnitude higher than those observed in coral cores collected in the Pacific under equivalent low pH conditions but living in oligotrophic waters. Heavier coral nitrogen isotope (δ15N) values pinpoint not only site-specific eutrophication, but also a sewage nitrogen source enriched in 15N. Our results show that eutrophication of reef seawater by land-based sources of pollution can magnify the effects of OA through nutrient driven-bioerosion. These conditions could contribute to the collapse of coastal coral reef ecosystems sooner than current projections predict based only on ocean acidification.

Experimental determination of CO2 content at graphite saturation along a natural basalt-peridotite melt join: Implications for the fate of carbon in terrestrial magma oceans

NASA Astrophysics Data System (ADS)

Duncan, Megan S.; Dasgupta, Rajdeep; Tsuno, Kyusei

2017-05-01

Knowledge of the carbon carrying capacity of peridotite melt at reducing conditions is critical to constrain the mantle budget and planet-scale distribution of carbon set at early stage of differentiation. Yet, neither measurements of CO2 content in reduced peridotite melt nor a reliable model to extrapolate the known solubility of CO2 in basaltic (mafic) melt to solubility in peridotitic (ultramafic) melt exist. There are several reasons for this gap; one reason is due to the unknown relative contributions of individual network modifying cations, such as Ca2+ versus Mg2+, on carbonate dissolution particularly at reducing conditions. Here we conducted high pressure, temperature experiments to estimate the CO2 contents in silicate melts at graphite saturation over a compositional range from natural basalts toward peridotite at a fixed pressure (P) of 1.0 GPa, temperature (T) of 1600 °C, and oxygen fugacity (log ⁡ fO2 ∼ IW + 1.6). We also conducted experiments to determine the relative effects of variable Ca and Mg contents in mafic compositions on the dissolution of carbonate. Carbon in quenched glasses was measured and characterized using Fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy and was found to be dissolved as carbonate (CO32-). The FTIR spectra showed CO32- doublets that shifted systematically with the MgO and CaO content of silicate melts. Using our data and previous work we constructed a new composition-based model to determine the CO2 content of ultramafic (peridotitic) melt representative of an early Earth, magma ocean composition at graphite saturation. Our data and model suggest that the dissolved CO2 content of reduced, peridotite melt is significantly higher than that of basaltic melt at shallow magma ocean conditions; however, the difference in C content between the basaltic and peridotitic melts may diminish with depth as the more depolymerized peridotite melt is more compressible. Using our model of CO2 content at graphite saturation as a function of P-T-fO2-melt composition, we predict that a superliquidus shallow magma ocean should degas CO2. Whereas if the increase of fO2 with depth is weak, a magma ocean may ingas a modest amount of carbon during crystallization. Further, using the carbon content of peridotite melt at log ⁡ fO2 of IW and the knowledge of C content of Fe-rich alloy melt, we also consider the core-mantle partitioning of carbon, showing that DCmetal/peridotite of a shallow magma ocean is generally higher than previously estimated.

Developing a low-cost open-source CTD for research and outreach

NASA Astrophysics Data System (ADS)

Thaler, A. D.; Sturdivant, K.

2013-12-01

Developing a low-cost open-source CTD for research and outreach Andrew David Thaler and Kersey Sturdivant Conductivity, temperature, and depth (CTD). With these three measurements, marine scientists can unlock ocean patterns hidden beneath the waves. The ocean is not uniform, it its filled with swirling eddies, temperature boundaries, layers of high and low salinity, changing densities, and many other physical characteristics. To reveal these patterns, oceanographers use a tool called the CTD. A CTD is found on almost every major research vessel. Rare is the scientific expedition-whether it be coastal work in shallow estuaries or journeys to the deepest ocean trenches-that doesn't begin with the humble CTD cast. The CTD is not cheap. Commercial CTD's start at more the 5,000 and can climb as high as 25,000 or more. We believe that the prohibitive cost of a CTD is an unacceptable barrier to open science. The price tag excludes individuals and groups who lack research grants or significant private funds from conducting oceanographic research. We want to make this tool-the workhorse of oceanographic research-available to anyone with an interest in the oceans. The OpenCTD is a low-cost, open-source CTD suitable for both educators and scientists. The platform is built using readily available parts and is powered by an Arduino-based microcontroller. Our goal is to create a device that is accurate enough to be used for scientific research and can be constructed for less than $200. Source codes, circuit diagrams, and building plans will be freely available. The final instrument will be effective to 200 meters depth. Why 200 meters? For many coastal regions, 200 meters of water depth covers the majority of the ocean that is accessible by small boat. The OpenCTD is targeted to people working in this niche, where entire research projects can be conducted for less than the cost of a commercial CTD. However, the Open CTD is scalable, and anyone with the inclination can adapt our plans to operate in deeper waters. Through a crowdfunding initiative and collaboration with numerous interested scientists, researchers, educators, and developers, we developed the framework for a low-cost, open-source, CTD that is appropriate for both scientific research and public outreach. We envision a network or researchers and educators using the OpenCTD to contribute to local and region scientific programs through open-source databases.

Broad-scale trophic shift in the pelagic North Pacific revealed by an oceanic seabird

PubMed Central

Wiley, Anne E.; James, Helen F.; Rossman, Sam; Walker, William A.; Zipkin, Elise F.; Chikaraishi, Yoshito

2017-01-01

Human-induced ecological change in the open oceans appears to be accelerating. Fisheries, climate change and elevated nutrient inputs are variously blamed, at least in part, for altering oceanic ecosystems. Yet it is challenging to assess the extent of anthropogenic change in the open oceans, where historical records of ecological conditions are sparse, and the geographical scale is immense. We developed millennial-scale amino acid nitrogen isotope records preserved in ancient animal remains to understand changes in food web structure and nutrient regimes in the oceanic realm of the North Pacific Ocean (NPO). Our millennial-scale isotope records of amino acids in bone collagen in a wide-ranging oceanic seabird, the Hawaiian petrel (Pterodroma sandwichensis), showed that trophic level declined over time. The amino acid records do not support a broad-scale increase in nitrogen fixation in the North Pacific subtropical gyre, rejecting an earlier interpretation based on bulk and amino acid specific δ15N chronologies for Hawaiian deep-sea corals and bulk δ15N chronologies for the Hawaiian petrel. Rather, our work suggests that the food web structure in the NPO has shifted at a broad geographical scale, a phenomenon potentially related to industrial fishing. PMID:28356448

The Ocean as a teaching tool: the first MOOC on Ocean Literacy

NASA Astrophysics Data System (ADS)

Santin, Selvaggia; Santoro, Francesca

2017-04-01

Education its broader understanding (in both formal and informal settings) serves as a high potential channel to reach young citizens. As a lack of sufficient 'Ocean Literacy' has been identified in many countries, this clearly presents a barrier for citizens to engage in ocean responsible behaviour or consider ocean-related careers. In order to sensitize and enable teachers and students to incorporate ocean literacy into educational programmes we build up a first Massive Open Online Course on Emma Platform, an European Multiple MOOC Aggregator that provides a system for the delivery of free, open, online courses in multiple languages from different European universities. Almost 500 students were enrolled from all over the world and we proposed a multi-perspective approach building on the UNESCO experience in the field of education for sustainable development. The course had two sections: a narrative format which introduces to the Ocean Literacy principles, focusing on how to incorporate them into lessons with tips, advice, references and activities; and an interactive section with webinairs which covers contemporary and emerging issues such as seafood, marine pollution and human health, simulating a "real-world experiences" with a problems-solutions approach.

Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches.

PubMed

Hirai, Hisashi; Takada, Hideshige; Ogata, Yuko; Yamashita, Rei; Mizukawa, Kaoruko; Saha, Mahua; Kwan, Charita; Moore, Charles; Gray, Holly; Laursen, Duane; Zettler, Erik R; Farrington, John W; Reddy, Christopher M; Peacock, Emily E; Ward, Marc W

2011-08-01

To understand the spatial variation in concentrations and compositions of organic micropollutants in marine plastic debris and their sources, we analyzed plastic fragments (∼10 mm) from the open ocean and from remote and urban beaches. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichloro-diphenyl-trichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), alkylphenols and bisphenol A were detected in the fragments at concentrations from 1 to 10,000 ng/g. Concentrations showed large piece-to-piece variability. Hydrophobic organic compounds such as PCBs and PAHs were sorbed from seawater to the plastic fragments. PCBs are most probably derived from legacy pollution. PAHs showed a petrogenic signature, suggesting the sorption of PAHs from oil slicks. Nonylphenol, bisphenol A, and PBDEs came mainly from additives and were detected at high concentrations in some fragments both from remote and urban beaches and the open ocean. Copyright © 2011 Elsevier Ltd. All rights reserved.

Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars

PubMed Central

Hu, Yongyun; Yang, Jun

2014-01-01

The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere–ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an “eyeball.” For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs’ habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets. PMID:24379386

Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars.

PubMed

Hu, Yongyun; Yang, Jun

2014-01-14

The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere-ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an "eyeball." For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs' habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets.

Lagrangian ocean analysis: Fundamentals and practices

DOE PAGES

van Sebille, Erik; Griffies, Stephen M.; Abernathey, Ryan; ...

2017-11-24

Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. A variety of tools and methods for this purpose have emerged, over several decades. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolvedmore » physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. Our overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.« less

Lagrangian ocean analysis: Fundamentals and practices

NASA Astrophysics Data System (ADS)

van Sebille, Erik; Griffies, Stephen M.; Abernathey, Ryan; Adams, Thomas P.; Berloff, Pavel; Biastoch, Arne; Blanke, Bruno; Chassignet, Eric P.; Cheng, Yu; Cotter, Colin J.; Deleersnijder, Eric; Döös, Kristofer; Drake, Henri F.; Drijfhout, Sybren; Gary, Stefan F.; Heemink, Arnold W.; Kjellsson, Joakim; Koszalka, Inga Monika; Lange, Michael; Lique, Camille; MacGilchrist, Graeme A.; Marsh, Robert; Mayorga Adame, C. Gabriela; McAdam, Ronan; Nencioli, Francesco; Paris, Claire B.; Piggott, Matthew D.; Polton, Jeff A.; Rühs, Siren; Shah, Syed H. A. M.; Thomas, Matthew D.; Wang, Jinbo; Wolfram, Phillip J.; Zanna, Laure; Zika, Jan D.

2018-01-01

Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. The overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.

Lagrangian ocean analysis: Fundamentals and practices

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Sebille, Erik; Griffies, Stephen M.; Abernathey, Ryan

Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. A variety of tools and methods for this purpose have emerged, over several decades. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolvedmore » physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. Our overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.« less

Benthic foraminifera show some resilience to ocean acidification in the northern Gulf of California, Mexico.

PubMed

Pettit, L R; Hart, M B; Medina-Sánchez, A N; Smart, C W; Rodolfo-Metalpa, R; Hall-Spencer, J M; Prol-Ledesma, R M

2013-08-30

Extensive CO2 vents have been discovered in the Wagner Basin, northern Gulf of California, where they create large areas with lowered seawater pH. Such areas are suitable for investigations of long-term biological effects of ocean acidification and effects of CO2 leakage from subsea carbon capture storage. Here, we show responses of benthic foraminifera to seawater pH gradients at 74-207m water depth. Living (rose Bengal stained) benthic foraminifera included Nonionella basispinata, Epistominella bradyana and Bulimina marginata. Studies on foraminifera at CO2 vents in the Mediterranean and off Papua New Guinea have shown dramatic long-term effects of acidified seawater. We found living calcareous benthic foraminifera in low pH conditions in the northern Gulf of California, although there was an impoverished species assemblage and evidence of post-mortem test dissolution. Copyright © 2013 Elsevier Ltd. All rights reserved.

Air pollution-aerosol interactions produce more bioavailable iron for ocean ecosystems.

PubMed

Li, Weijun; Xu, Liang; Liu, Xiaohuan; Zhang, Jianchao; Lin, Yangting; Yao, Xiaohong; Gao, Huiwang; Zhang, Daizhou; Chen, Jianmin; Wang, Wenxing; Harrison, Roy M; Zhang, Xiaoye; Shao, Longyi; Fu, Pingqing; Nenes, Athanasios; Shi, Zongbo

2017-03-01

It has long been hypothesized that acids formed from anthropogenic pollutants and natural emissions dissolve iron (Fe) in airborne particles, enhancing the supply of bioavailable Fe to the oceans. However, field observations have yet to provide indisputable evidence to confirm this hypothesis. Single-particle chemical analysis for hundreds of individual atmospheric particles collected over the East China Sea shows that Fe-rich particles from coal combustion and steel industries were coated with thick layers of sulfate after 1 to 2 days of atmospheric residence. The Fe in aged particles was present as a "hotspot" of (insoluble) iron oxides and throughout the acidic sulfate coating in the form of (soluble) Fe sulfate, which increases with degree of aging (thickness of coating). This provides the "smoking gun" for acid iron dissolution, because iron sulfate was not detected in the freshly emitted particles and there is no other source or mechanism of iron sulfate formation in the atmosphere.

Air-Sea Enthalpy and Momentum Exchange at Major Hurricane Wind Speeds Observed during CBLAST

DTIC Science & Technology

2012-11-01

Oceanic and Atmospheric Administration, and ONR for organizing the CBLAST experiment and collecting the data used for this study. Thanks also go to...Atmos. Oceanic Technol., 21, 457–469. Gill, A., 1982: Atmosphere – Ocean Dynamics. Academic Press, 662 pp. Haus, B. K., D. Jeong,M.A.Donelan, J. A...Open ocean momentum flux measurements in moderate to strong winds. J. Phys. Ocean - ogr., 11, 324–336. Lindzen, R., 1990: Dynamics in Atmospheric

50 CFR 660.316 - Open access fishery-observer requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Open access fishery-observer requirements. 660.316 Section 660.316 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC... West Coast Groundfish-Open Access Fisheries § 660.316 Open access fishery—observer requirements. (a...

50 CFR 660.316 - Open access fishery-observer requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Open access fishery-observer requirements. 660.316 Section 660.316 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC... West Coast Groundfish-Open Access Fisheries § 660.316 Open access fishery—observer requirements. (a...

50 CFR 660.316 - Open access fishery-observer requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Open access fishery-observer requirements. 660.316 Section 660.316 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC... West Coast Groundfish-Open Access Fisheries § 660.316 Open access fishery—observer requirements. (a...

50 CFR 660.316 - Open access fishery-observer requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Open access fishery-observer requirements. 660.316 Section 660.316 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC... West Coast Groundfish-Open Access Fisheries § 660.316 Open access fishery—observer requirements. (a...

50 CFR 660.316 - Open access fishery-observer requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Open access fishery-observer requirements. 660.316 Section 660.316 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC... West Coast Groundfish-Open Access Fisheries § 660.316 Open access fishery—observer requirements. (a...

Convective Available Potential Energy of World Ocean

NASA Astrophysics Data System (ADS)

Su, Z.; Ingersoll, A. P.; Thompson, A. F.

2012-12-01

Here, for the first time, we propose the concept of Ocean Convective Available Potential Energy (OCAPE), which is the maximum kinetic energy (KE) per unit seawater mass achievable by ocean convection. OCAPE occurs through a different mechanism from atmospheric CAPE, and involves the interplay of temperature and salinity on the equation of state of seawater. The thermobaric effect, which arises because the thermal coefficient of expansion increases with depth, is an important ingredient of OCAPE. We develop an accurate algorithm to calculate the OCAPE for a given temperature and salinity profile. We then validate our calculation of OCAPE by comparing it with the conversion of OCAPE to KE in a 2-D numerical model. We propose that OCAPE is an important energy source of ocean deep convection and contributes to deep water formation. OCAPE, like Atmospheric CAPE, can help predict deep convection and may also provide a useful constraint for modelling deep convection in ocean GCMs. We plot the global distribution of OCAPE using data from the World Ocean Atlas 2009 (WOA09) and see many important features. These include large values of OCAPE in the Labrador, Greenland, Weddell and Mediterranean Seas, which are consistent with our present observations and understanding, but also identify some new features like the OCAPE pattern in the Antarctic Circumpolar Current (ACC). We propose that the diagnosis of OCAPE can improve our understanding of global patterns of ocean convection and deep water formation as well as ocean stratification, the meridional overturning circulation and mixed layer processes. The background of this work is briefly introduced as below. Open-ocean deep convection can significantly modify water properties both at the ocean surface and throughout the water column (Gordon 1982). Open-ocean convection is also an important mechanism for Ocean Deep Water formation and the transport of heat, freshwater and nutrient (Marshall and Schott 1999). Open-ocean convection may arise through strong surface buoyancy fluxes (Schott et al. 1996), or by thermobaric instability (Akitomo 1999a, b). Ingersoll (2005) demonstrated that thermobaric-induced deep convection is due to the abrupt release of ocean potential energy into kinetic energy. In atmospheric dynamics, Convective Available Potential Energy (CAPE) has long been an important thermodynamic variable (Arakawa and Schubert 1974) that has been used to forecast moist convection (Doswell and Rasmussen 1994) and to test the performance of GCMs (Ye et al. 1998). However, the development of a similar diagnostic in the ocean has received little attention.; World Ocean Convective Available Potential Energy distribution in North-Hemisphere Autumn (J/kg)

Pole-to-pole biogeography of surface and deep marine bacterial communities

PubMed Central

Ghiglione, Jean-François; Galand, Pierre E.; Pommier, Thomas; Pedrós-Alió, Carlos; Maas, Elizabeth W.; Bakker, Kevin; Bertilson, Stefan; Kirchman, David L.; Lovejoy, Connie; Yager, Patricia L.; Murray, Alison E.

2012-01-01

The Antarctic and Arctic regions offer a unique opportunity to test factors shaping biogeography of marine microbial communities because these regions are geographically far apart, yet share similar selection pressures. Here, we report a comprehensive comparison of bacterioplankton diversity between polar oceans, using standardized methods for pyrosequencing the V6 region of the small subunit ribosomal (SSU) rRNA gene. Bacterial communities from lower latitude oceans were included, providing a global perspective. A clear difference between Southern and Arctic Ocean surface communities was evident, with 78% of operational taxonomic units (OTUs) unique to the Southern Ocean and 70% unique to the Arctic Ocean. Although polar ocean bacterial communities were more similar to each other than to lower latitude pelagic communities, analyses of depths, seasons, and coastal vs. open waters, the Southern and Arctic Ocean bacterioplankton communities consistently clustered separately from each other. Coastal surface Southern and Arctic Ocean communities were more dissimilar from their respective open ocean communities. In contrast, deep ocean communities differed less between poles and lower latitude deep waters and displayed different diversity patterns compared with the surface. In addition, estimated diversity (Chao1) for surface and deep communities did not correlate significantly with latitude or temperature. Our results suggest differences in environmental conditions at the poles and different selection mechanisms controlling surface and deep ocean community structure and diversity. Surface bacterioplankton may be subjected to more short-term, variable conditions, whereas deep communities appear to be structured by longer water-mass residence time and connectivity through ocean circulation. PMID:23045668

A daily global mesoscale ocean eddy dataset from satellite altimetry.

PubMed

Faghmous, James H; Frenger, Ivy; Yao, Yuanshun; Warmka, Robert; Lindell, Aron; Kumar, Vipin

2015-01-01

Mesoscale ocean eddies are ubiquitous coherent rotating structures of water with radial scales on the order of 100 kilometers. Eddies play a key role in the transport and mixing of momentum and tracers across the World Ocean. We present a global daily mesoscale ocean eddy dataset that contains ~45 million mesoscale features and 3.3 million eddy trajectories that persist at least two days as identified in the AVISO dataset over a period of 1993-2014. This dataset, along with the open-source eddy identification software, extract eddies with any parameters (minimum size, lifetime, etc.), to study global eddy properties and dynamics, and to empirically estimate the impact eddies have on mass or heat transport. Furthermore, our open-source software may be used to identify mesoscale features in model simulations and compare them to observed features. Finally, this dataset can be used to study the interaction between mesoscale ocean eddies and other components of the Earth System.

A baroclinic quasigeostrophic open ocean model

NASA Technical Reports Server (NTRS)

Miller, R. N.; Robinson, A. R.; Haidvogel, D. B.

1983-01-01

A baroclinic quasigeostrophic open ocean model is presented, calibrated by a series of test problems, and demonstrated to be feasible and efficient for application to realistic mid-oceanic mesoscale eddy flow regimes. Two methods of treating the depth dependence of the flow, a finite difference method and a collocation method, are tested and intercompared. Sample Rossby wave calculations with and without advection are performed with constant stratification and two levels of nonlinearity, one weaker than and one typical of real ocean flows. Using exact analytical solutions for comparison, the accuracy and efficiency of the model is tabulated as a function of the computational parameters and stability limits set; typically, errors were controlled between 1 percent and 10 percent RMS after two wave periods. Further Rossby wave tests with realistic stratification and wave parameters chosen to mimic real ocean conditions were performed to determine computational parameters for use with real and simulated data. Finally, a prototype calculation with quasiturbulent simulated data was performed successfully, which demonstrates the practicality of the model for scientific use.

A daily global mesoscale ocean eddy dataset from satellite altimetry

PubMed Central

Faghmous, James H.; Frenger, Ivy; Yao, Yuanshun; Warmka, Robert; Lindell, Aron; Kumar, Vipin

2015-01-01

Mesoscale ocean eddies are ubiquitous coherent rotating structures of water with radial scales on the order of 100 kilometers. Eddies play a key role in the transport and mixing of momentum and tracers across the World Ocean. We present a global daily mesoscale ocean eddy dataset that contains ~45 million mesoscale features and 3.3 million eddy trajectories that persist at least two days as identified in the AVISO dataset over a period of 1993–2014. This dataset, along with the open-source eddy identification software, extract eddies with any parameters (minimum size, lifetime, etc.), to study global eddy properties and dynamics, and to empirically estimate the impact eddies have on mass or heat transport. Furthermore, our open-source software may be used to identify mesoscale features in model simulations and compare them to observed features. Finally, this dataset can be used to study the interaction between mesoscale ocean eddies and other components of the Earth System. PMID:26097744

The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model

NASA Astrophysics Data System (ADS)

Tagliabue, Alessandro; Hawco, Nicholas J.; Bundy, Randelle M.; Landing, William M.; Milne, Angela; Morton, Peter L.; Saito, Mak A.

2018-04-01

Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B12 and is a co-factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state-of-the-art three-dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom-water oxygen conditions. The basin-scale distribution of cobalt supplied from margins is facilitated by the activity of manganese-oxidizing bacteria being suppressed under low oxygen and low temperatures, which extends the residence time of cobalt. Overall, we find a residence time of 7 and 250 years in the upper 250 m and global ocean, respectively. Importantly, we find that the dominant internal resupply process switches from regeneration and recycling of particulate cobalt to dissolution of scavenged cobalt between the upper ocean and the ocean interior. Our model highlights key regions of the ocean where biological activity may be most sensitive to cobalt availability.

The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

NASA Astrophysics Data System (ADS)

de la Fuente, Maria; Calvo, Eva; Skinner, Luke; Pelejero, Carles; Evans, David; Müller, Wolfgang; Povea, Patricia; Cacho, Isabel

2017-12-01

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state (Δ[CO32-], and therefore [CO32-]), along with δ13C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower [CO32-], δ13C, and [O2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a "counteracting" mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be "sequestered" by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity.

Coral Calcification Across a Natural Gradient in Ocean Acidification

NASA Astrophysics Data System (ADS)

Cohen, A. L.; Brainard, R. E.; Young, C.; Shamberger, K. E.; McCorkle, D. C.; Feely, R. A.; Mcleod, E.; Cantin, N.; Rose, K.; Lohmann, G. P.

2011-12-01

Much of our understanding of the impact of ocean acidification on coral calcification comes from laboratory manipulation experiments in which corals are reared under a range of seawater pH and aragonite saturation states (μar) equivalent to those projected for the next hundred years. In general, experiments show a consistently negative impact of acidification on coral calcification, leading to predictions of mass coral reef extinctions by dissolution as natural rates of carbonate erosion exceed the rates at which corals and other reef calcifiers can replace it. The tropical oceans provide a natural laboratory within which to test hypotheses about the longer term impact and adaptive potential of corals to acidification of the reef environment. Here we report results of a study in which 3-D CT scan and imaging techniques were used to quantify annual rates of calcification by conspecifics at 12 reefs sites spanning a natural gradient in ocean acidification. In situ μar calculated from alkalinity and DIC measurements of reef seawater ranged from less than 2.7 on an eastern Pacific Reef to greater than 4.0 in the central Red Sea. No correlation between μar and calcification was observed across this range. Corals living on low μar reefs appear to be calcifying as fast, sometimes faster than conspecifics living on high μar reefs. We used total lipid and tissue thickness to index the energetic status of colonies collected at each of our study sites. Our results support the hypothesis that energetics plays a key role in the coral calcification response to ocean acidification. Indeed, the true impact of acidification on coral reefs will likely be felt as temperatures rise and the ocean becomes more stratified, depleting coral energetic reserves through bleaching and reduced nutrient delivery to oceanic reefs.

Tadalafil inclusion in microporous silica as effective dissolution enhancer: optimization of loading procedure and molecular state characterization.

PubMed

Mehanna, Mohammed M; Motawaa, Adel M; Samaha, Magda W

2011-05-01

Tadalafil is an efficient drug used to treat erectile dysfunction characterized by poor water solubility, which has a negative influence on its bioavailability. Utilization of microporous silica represents an effective and facile technology to increase the dissolution rate of poorly soluble drugs. Our strategy involved directly introducing tadalafil as guest molecule into microporous silica as host material by incipient wetness impregnation method. To optimize tadalafil inclusion, response surface methodology (RSM) using 3(3) factorial design was utilized. Furthermore, to investigate the molecular state of tadalafil, Fourier-transform infrared spectroscopy, differential scanning calorimetery, thermal gravimetrical analysis, nitrogen adsorption, and powder X-ray diffraction (PXRD) were carried out. The results obtained pointed out that the quantity of microporous silica was the predominant factor that increased the loading efficiency. For the optimized formula, the loading efficiency was 42.50 wt %. Adsorption-desorption experiments indicated that tadalafil has been introduced into the micropores. Powder XRD and differential scanning calorimetry analyses revealed that tadalafil is arranged in amorphous form. In addition, the dissolution rate of tadalafil from the microporous silica was faster than that of free drug. Amorphous tadalafil occluded in microporous silica did not crystallize over 3 months. These findings contributed in opening a new strategy concerning the utilization of porous silica for the dissolution rate enhancement. Copyright © 2010 Wiley-Liss, Inc.

Atmospheric and Oceanic Response to Southern Ocean Deep Convection Oscillations on Decadal to Centennial Time Scales in Climate Models

NASA Astrophysics Data System (ADS)

Martin, T.; Reintges, A.; Park, W.; Latif, M.

2014-12-01

Many current coupled global climate models simulate open ocean deep convection in the Southern Ocean as a recurring event with time scales ranging from a few years to centennial (de Lavergne et al., 2014, Nat. Clim. Ch.). The only observation of such event, however, was the occurrence of the Weddell Polynya in the mid-1970s, an open water area of 350 000 km2 within the Antarctic sea ice in three consecutive winters. Both the wide range of modeled frequency of occurrence and the absence of deep convection in the Weddell Sea highlights the lack of understanding concerning the phenomenon. Nevertheless, simulations indicate that atmospheric and oceanic responses to the cessation of deep convection in the Southern Ocean include a strengthening of the low-level atmospheric circulation over the Southern Ocean (increasing SAM index) and a reduction in the export of Antarctic Bottom Water (AABW), potentially masking the regional effects of global warming (Latif et al., 2013, J. Clim.; Martin et al., 2014, Deep Sea Res. II). It is thus of great importance to enhance our understanding of Southern Ocean deep convection and clarify the associated time scales. In two multi-millennial simulations with the Kiel Climate Model (KCM, ECHAM5 T31 atmosphere & NEMO-LIM2 ~2˚ ocean) we showed that the deep convection is driven by strong oceanic warming at mid-depth periodically overriding the stabilizing effects of precipitation and ice melt (Martin et al., 2013, Clim. Dyn.). Sea ice thickness also affects location and duration of the deep convection. A new control simulation, in which, amongst others, the atmosphere grid resolution is changed to T42 (~2.8˚), yields a faster deep convection flip-flop with a period of 80-100 years and a weaker but still significant global climate response similar to CMIP5 simulations. While model physics seem to affect the time scale and intensity of the phenomenon, the driving mechanism is a rather robust feature. Finally, we compare the atmospheric and oceanic responses among CMIP5 models. Since open ocean convection is the dominant mode of AABW formation in these models, the northward extent and strength of the AABW cell in the Atlantic correlates with the deep convection intensity but varies between models. Likewise, atmospheric response patterns outside the Southern Ocean region are not consistent among models.

[Method for the evaluation of the stability and usability after opening packages of orally disintegrating tablets: case of amlodipine besilate products].

PubMed

Hori, Katsuhito; Yoshida, Naoko; Okumura, Tomonori; Okamura, Yasufumi; Kawakami, Junichi

2010-08-01

Orally disintegrating (OD) tablets are widely used in clinical practice. However, drug information on the choice and dispensing based on their stability after opening packages and usability in patients and dispensaries is not sufficient. The aim of this study was to investigate possible evaluation methods of the stability and usability of amlodipine OD tablets. Additives of the brand were changed in April 2009, and therefore the previous and current forms and two generics, current and newly marketed (in November 2009) products of different firms, were used. OD tablets were stored at 25 degrees C and 75% relative humidity for 3 months after opening the packages, and their physicochemical properties were evaluated. Their weight, diameter, thickness, and color difference increased slightly from the initial state. The extent of the change in their hardness, disintegration time, and friability was different among products. These physicochemical changes were acceptable in dispensary practice. Storage after opening the packages did not affect their dissolution rate. The dissolution rate at the initial state of the current brand was slower than that of the previous one. All products used were able to be dispensed by an automatic tablet-packing machine and applied to the so-called simple suspension method for intubational administration. Sensory evaluation tests revealed no major difference in the oral disintegration time, taste, impression, and preference among products. In conclusion, the stability and usability of amlodipine OD tablets used in this study were examined using several methods, and they can be used equivalently from the stability and usability viewpoints.

Enhanced terrestrial weathering/runoff and surface ocean carbonate production during the recovery stages of the Paleocene-Eocene thermal maximum

NASA Astrophysics Data System (ADS)

Kelly, D. Clay; Zachos, James C.; Bralower, Timothy J.; Schellenberg, Stephen A.

2005-12-01

The carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the Paleocene-Eocene thermal maximum (PETM) (circa 55 Ma). The rapid release of large quantities of carbon into the ocean-atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion (CIE). The brevity (120-220 kyr) of the PETM reflects the rapid enhancement of negative feedback mechanisms within Earth's exogenic carbon cycle that served the dual function of buffering ocean pH and reducing atmospheric greenhouse gas levels. Detailed study of the PETM stratigraphy from Ocean Drilling Program Site 690 (Weddell Sea) reveals that the CIE recovery period, which postdates the CIE onset by ˜80 kyr, is represented by an expanded (˜2.5 m thick) interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate. Collectively, the micropaleontological and sedimentological changes preserved within the CIE recovery interval reflect a transient state when ocean-atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths. A prominent peak in the abundance of the clay mineral kaolinite is associated with the CIE recovery interval, indicating that continental weathering/runoff intensified at this time as well (Robert and Kennett, 1994). Such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering/runoff and carbonate precipitation helped sequester carbon during the PETM recovery period (e.g., Dickens et al., 1997; Zachos et al., 2005).

Pteropods as indicators for Cumulative Ocean Acidification Exposure

NASA Astrophysics Data System (ADS)

Bednarsek, N.; Klinger, T.

2016-02-01

Pteropods are ubiquitously distributed pelagic marine zooplankton of importance in productive upwelling regimes, where they represent an important prey item for variety of economically, ecologically, and culturally important fish species. Because of their extreme sensitivity to ocean acidification conditions, pteropods can be used to establish cause and effect relationships between OA status and biological condition. Incorporating biological responses into a successful management framework requires laboratory studies that demonstrate sentinel organism responses to specific stressors, while also documenting population or community level effects in the field linked to that stressor. Here, we describe the state of the science and an approach that demonstrates the linkage necessary to use pteropods as a sentinel organism for resource management under conditions of ocean acidification. To demonstrate this utility, newly developed methods were used to determine and quantify pteropod responses in the natural environment. Responses such as shell dissolution, shell calcification, changes in vertical distribution, and survival success were assessed to establish pteropod condition under a variety of OA conditions. While no single species or set of species can adequately capture all aspects of ecosystem change, pteropods represent first quantifiable, specific indicators for ocean acidification's effects on marine systems. The approach can be used in water quality assessments and in living marine resource management as part of the rapid and cost-effective monitoring of biological responses to ocean acidification. The social challenges of changing ocean chemistry will continue to grow in coming decades, making the availability of such straightforward metrics of impact indispensable across scales of time and space of relevance to managers.

Open ocean Internal Waves, Namibia Coast, Africa.

NASA Technical Reports Server (NTRS)

1990-01-01

These open ocean Internal Waves were seen off the Namibia Coast, Africa (19.5S, 11.5E). The periodic and regularly spaced sets of incoming internal appear to be diffracting against the coastline and recombining to form a network of interference patterns. They seem to coincide with tidal periods about 12 hours apart and wave length (distance from crest to crest) varies between 1.5 and 5.0 miles and the crest lengths stretch beyond the image.

Open ocean Internal Waves, Namibia Coast, Africa.

NASA Image and Video Library

1990-12-10

These open ocean Internal Waves were seen off the Namibia Coast, Africa (19.5S, 11.5E). The periodic and regularly spaced sets of incoming internal appear to be diffracting against the coastline and recombining to form a network of interference patterns. They seem to coincide with tidal periods about 12 hours apart and wave length (distance from crest to crest) varies between 1.5 and 5.0 miles and the crest lengths stretch beyond the image.

Open ocean Internal Waves, Namibia Coast, Africa.

NASA Image and Video Library

1990-12-10

These open ocean Internal Waves were seen off the Namibia Coast, Africa (23.0S, 14.0E). The periodic and regularly spaced sets of internal waves most likely coincide with tidal periods about 12 hours apart. The wave length (distance from crest to crest) varies between 1.5 and 5.0 miles and the crest lengths stretch across and beyond the distance of the photo. The waves are intersecting the Namibia coastline at about a 30 degree angle.

Open ocean Internal Waves, Namibia Coast, Africa.

NASA Technical Reports Server (NTRS)

1990-01-01

These open ocean Internal Waves were seen off the Namibia Coast, Africa (23.0S, 14.0E). The periodic and regularly spaced sets of internal waves most likely coincide with tidal periods about 12 hours apart. The wave length (distance from crest to crest) varies between 1.5 and 5.0 miles and the crest lengths stretch across and beyond the distance of the photo. The waves are intersecting the Namibia coastline at about a 30 degree angle.

Santa Margarita Lagoon Water Quality Monitoring Data

DTIC Science & Technology

2012-08-01

sits entirely within the boundaries of Marine Corps Base Camp Pendleton. It forms up where the Santa Margarita River meets the Pacific Ocean just north...of Oceanside, California. The western boundary of the lagoon is the beach berm that borders the ocean . The estuarine lagoon is usually open to the... ocean through a limited section of berm, although there are occasions when the lagoon is effectively closed to exchange with the ocean . The eastern

Environmental Conditions in the Norwegian-Iceland Seas, May 1987.

DTIC Science & Technology

1987-06-01

Ocanography Division auI W May Joseph W. McCaffrey Ocean Science Directorate Ocean Sensing and Prediction Division June 1987 88330 8 I - I PRELIMINARY REPORT...Leonard Walstad) using an open ocean model; and (4) ship observations aboard the West German ship PLANET . This report concentrates on the first two...validation and delivery for operational use of oceanic and acoustic numerical forecast systems, and the assimilation of in-situ and remotely sensed data

Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic

NASA Astrophysics Data System (ADS)

Buckingham, Christian E.; Khaleel, Zammath; Lazar, Ayah; Martin, Adrian P.; Allen, John T.; Naveira Garabato, Alberto C.; Thompson, Andrew F.; Vic, Clément

2017-08-01

A high-resolution satellite image that reveals a train of coherent, submesoscale (6 km) vortices along the edge of an ocean front is examined in concert with hydrographic measurements in an effort to understand formation mechanisms of the submesoscale eddies. The infrared satellite image consists of ocean surface temperatures at ˜390 m resolution over the midlatitude North Atlantic (48.69°N, 16.19°W). Concomitant altimetric observations coupled with regular spacing of the eddies suggest the eddies result from mesoscale stirring, filamentation, and subsequent frontal instability. While horizontal shear or barotropic instability (BTI) is one mechanism for generating such eddies (Munk's hypothesis), we conclude from linear theory coupled with the in situ data that mixed layer or submesoscale baroclinic instability (BCI) is a more plausible explanation for the observed submesoscale vortices. Here we assume that the frontal disturbance remains in its linear growth stage and is accurately described by linear dynamics. This result likely has greater applicability to the open ocean, i.e., regions where the gradient Rossby number is reduced relative to its value along coasts and within strong current systems. Given that such waters comprise an appreciable percentage of the ocean surface and that energy and buoyancy fluxes differ under BTI and BCI, this result has wider implications for open-ocean energy/buoyancy budgets and parameterizations within ocean general circulation models. In summary, this work provides rare observational evidence of submesoscale eddy generation by BCI in the open ocean.