Release rates of trace elements and protein from decomposing planktonic debris. 2. Copepod carcasses and sediment trap particulate matter

In experiments designed to relate the release kinetics of various elements with that of protein from biogenic particles, 110mAg, 241Am, 109Cd, 60Co, 75Se and protein were measured over time in radiolabeled copepod carcasses and particles caught in unpoisoned sediment traps (mostly zooplankton fecal pellets and amorphous marine snow). Log-linear release rate constants (k) of 110mAg, 241Am, 109Cd, and 60Co from carcasses ranged from 0.079 d−1 for 60Co at 2°C to 0.130 d−1 for 109Cd at 15°C, and did not vary significantly with temperature. 75Se was lost most rapidly from copepod carcasses at 2°C, with k = 0.168 d−1; however, at 15°C, 75Se was in two compartments, with 56% in a rapidly exchanging pool (k = 0.391 d−1) and 44% in a slowly exchanging pool (k = 0.107 d−1). Protein displayed loss from two compartments at both temperatures. At 2°C, protein was lost slowly (k = 0.065 d−1) for 1 wk, after which it was released from the carcasses very rapidly (k = 0.245 d−1). At 15°C, however, the loss of protein from carcasses was more rapid over the first 2 d (k = 0.627 d−1) than thereafter (k = 0.127 d−1). The k values of 110mAg, 241Am, and 60Co from sediment trap particles (15°C) ranged from 0.008 to 0.011 d−1. Protein was lost twice as fast as 110mAg, 241Am, and 60Co, more slowly than half of the particulate 109Cd and 75Se in rapidly exchanging pools (k = 0.168 and 0.237 d−1, respectively), and at rates comparable to 109Cd and 75Se in slowly exchanging pools. Overall, copepod carcasses and fecal pellets could act as vectors of these five elements and protein to the deep ocean, the vertical flux being dependent on settling velocity and water column temperature structure. Of the elements considered here, Se follows the cycling of protein most closely

Ocean acidification reshapes the otolith-body allometry of growth in juvenile seabream

International audienceThe effects of elevated CO2 partial pressure (pCO2) on otolith calcification and on the coupling between the somatic and otolith growth were investigated in juvenile gilthead seabream Sparus aurata. Six-month old individuals were raised during seven weeks under four pCO2 conditions set according to projected future ocean acidification scenarios. Body and otolith biometric parameters were measured throughout the experiment along with the otolith biomineralization monitored using a radiotracer technique based on 45Ca incorporation. Seabream exhibited somatic growth resilience to all treatments. In contrast, increased growth rate and shape complexity of otoliths were observed with a pHT drop from 8.1 to 7.5. Hypercalcification was observed under lowered pH, with a rate of calcium incorporation increasing by up to 18% between pHT 8.1 and pHT 7.7. This work highlighted an uncoupling of otolith and body growth of juvenile seabream within 40 d at pHT 7.9 projected to be reached by the end of the century. As the otolith is an essential tool used in reconstructing fish life history, this work suggests that information resulting from otolith studies should be interpreted with caution with respect to the potential impacts that ocean acidification projected modifications could have on otolith biomineralization

Ocean acidification and temperature rise: effects on calcification during early development of the cuttlefish Sepia officinalis

This study investigated the effects of seawater pH (i.e., 8.10, 7.85 and 7.60) and temperature (16 and 19 °C) on (a) the abiotic conditions in the fluid surrounding the embryo (viz. the perivitelline fluid), (b) growth, development and (c) cuttlebone calcification of embryonic and juvenile stages of the cephalopod Sepia officinalis. Egg swelling increased in response to acidification or warming, leading to an increase in egg surface while the interactive effects suggested a limited plasticity of the swelling modulation. Embryos experienced elevated pCO2 conditions in the perivitelline fluid (>3-fold higher pCO2 than that of ambient seawater), rendering the medium under-saturated even under ambient conditions. The growth of both embryos and juveniles was unaffected by pH, whereas 45Ca incorporation in cuttlebone increased significantly with decreasing pH at both temperatures. This phenomenon of hypercalcification is limited to only a number of animals but does not guarantee functional performance and calls for better mechanistic understanding of calcification processes

Response of the Arctic Pteropod Limacina helicina to Projected Future Environmental Conditions

Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels o

Cadmium bioconcentration in the echinoid Paracentrotus lividus: Influence of the cadmium concentration in seawater

Uptake and loss kinetics of cadmium were studied in Paracentrotus lividus exposed for 24 d to different stable Cd concentrations (0 to 1.14 μg Cd l-1) and 109Cd tracer added to seawater. The whole-body uptake kinetics were linear over the time course of the experiment. The whole-body 109Cd concentration factor was independent of the stable Cd concentration in ambient seawater. Bioconcentration of Cd in whole individuals and their body compartments was directly proportional to the Cd concentration added to the seawater. The echinoid digestive tract wall showed the highest degree of Cd uptake. Whole-body loss kinetics were described by a 2-component exponential equation. The loss kinetics were similar for each of the treatments examined. Cadmium was found to display a long biological half-life in echinoid tissues; the major fraction (73 to 85%) of the Cd taken up by echinoids was eliminated following a loss component whose biological half-life was of the order of 1 year, regardless of the absolute Cd concentration accumulated by the echinoid. Paracentrotus lividus is suggested as a valuable biomonitor of Cd, particularly where knowledge of Cd concentration variations over long-term is of interest.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Biokinetics of radiocobalt in the asteroid Asterias rubens (Echinodermata): Sea water and food exposures

Uptake and loss of cobalt-57 were investigated in the starfish Asterias rubens, in order to assess its value as a sentinel organism for nearshore radionuclide contamination. Whole-body uptake from sea water was linear over a 32-day exposure period and reached wet weight concentration factor (CF) of 23±5. Bioaccumulation of 57Co was dependent upon body compartment, the aboral part of the body wall concentrating cobalt to the greatest degree (wet weight CF: 77±16). After restoration of uncontaminated conditions, radiocobalt was released following an exponential loss kinetics characterized by a biological half-life (T(b1/2)) of 27±6 day. Dietary radiocobalt (taken up during a short-term feeding for 24 h on radiolabelled mussels) showed a much more rapid turnover time (T(b1/2): 14±4 d), suggesting that A. rubens accumulates this radionuclide predominantly from sea water. A. rubens, and more particularly the aboral part of its body wall, would readily reveal the presence of an environmental contamination by radiocobalt and could preserve this information over a period of few months. Copyright (C) 1999 Elsevier Science Ltd.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Seawater carbonate chemistry and biological processes during experiments with Limacina helicina, 2009

Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels of 280, 380, 550, 760 and 1020 µatm and at control (0°C) and elevated (4°C) temperatures. The respiration rate was unaffected by pCO2 at control temperature, but significantly increased as a function of the pCO2 level at elevated temperature. pCO2 had no effect on the gut clearance rate at either temperature. Precipitation of CaCO3, measured as the incorporation of 45Ca, significantly declined as a function of pCO2 at both temperatures. The decrease in calcium carbonate precipitation was highly correlated to the aragonite saturation state. Even though this study demonstrates that pteropods are able to precipitate calcium carbonate at low aragonite saturation state, the results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems

Biokinetics of selected heavy metals and radionuclides in the common Mediterranean echinoid Paracentrotus lividus: Sea water and food exposures

Uptake and loss kinetics of Zn, Ag, Cd, 134Cs, and 241Am by the echinoid Paracentrotus lividus contaminated through either water or food were determined in controlled laboratory radiotracer experiments using low contaminant concentrations. The echinoid efficiently accumulated most of the elements from water. The only exception was 134Cs (concentration factor at steady state = 2.7). With respect to relative metal bioavailability, concentrations in the different body compartments of P. lividus were generally ranked in the order: digestive wall > gonads ≤ body wall > Aristotle's lantern > coelomic fluid. However, for 241Am, body wall uptake was as efficient as that of the digestive wall. The loss kinetics for Zn, Ag and 134Cs were described by a 2-component model whereas loss of Cd and 241Am was linear during the time course of the experiment. Loss of the different elements was relatively slow, except for 134Cs, whose long-lived loss component was characterized by a biological half-life of 6 d. Loss of the different elements ingested with food was described by a single-component model for Cd, 134Cs, and 241Am and by a 2-component model for Zn and Ag. Parameters of the kinetics indicate that all (for Cd, 134Cs, and 241Am) or most (for Zn and Ag) of the ingested amount of element is readily lost from the organism with the faeces. However, estimation of the assimilated fraction of elements ingested by the echinoids suggests that food could contribute significantly t the iota body burden of Ag in P. lividus.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Biokinetics of selected heavy metals and radionuclides in two marine macrophytes: The seagrass Posidonia oceanica and the alga Caulerpa taxifolia

Uptake and loss kinetics of Zn, Ag, Cd, 134Cs, and 241Am by shoots of the seagrass Posidonia oceanica and fronds of the green alga Caulerpa taxifolia were determined in controlled laboratory radiotracer experiments using low contaminant concentrations. The two species accumulated most of the elements efficiently. The only exceptions were 134Cs in both P. oceanica and C. taxifolia and Cd in C. taxifolia (concentration factors ≤ 6.4). Steady state in uptake was reached in C. taxifolia for each element except Ag. In P. oceanica, steady state was noted for the uptake of Ag and 134Cs whereas Zn, Cd, and 241Am were linearly accumulated during the course of the experiment (15 d). With respect to relative metal bioavailability, the different compartments of P. oceanica shoots were generally ranked in the order: leaf epiphytes > adult leaves = intermediate leaves > leaf sheaths. The long-lived component of the loss kinetics for each element in P. oceanica was characterized by a relatively short biological half-life (T(b1/2) ≤ 28 d). However, observations for the individual compartments indicated that adult leaves had a high retention capacity for Ag and 134Cs. With virtually 100% retained after 21 d in uncontaminated sea water. In C. taxifolia, the long-lived component of the loss kinetics for each element was characterized by a T(b1/2) value that was not significantly different from infinity, an observation which suggests that a substantial fraction of the metal or radionuclide incorporated during a contamination event would be irreversibly bound by this algal species.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Seawater carbonate chemistry in Kongsfjorden, Svalbard, May 2009

Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels of 280, 380, 550, 760 and 1020 µatm and at control (0°C) and elevated (4°C) temperatures. The respiration rate was unaffected by pCO2 at control temperature, but significantly increased as a function of the pCO2 level at elevated temperature. pCO2 had no effect on the gut clearance rate at either temperature. Precipitation of CaCO3, measured as the incorporation of 45Ca, significantly declined as a function of pCO2 at both temperatures. The decrease in calcium carbonate precipitation was highly correlated to the aragonite saturation state. Even though this study demonstrates that pteropods are able to precipitate calcium carbonate at low aragonite saturation state, the results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems