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Nicholas S Fisher - One of the best experts on this subject based on the ideXlab platform.
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factors influencing the assimilation of arsenic in a Deposit Feeding polychaete
Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2012Co-Authors: Zofia Baumann, Antonius Koller, Nicholas S FisherAbstract:Abstract We investigated mechanisms leading to the assimilation of particle-bound arsenic (As) ingested by the Deposit-Feeding polychaete Alitta succinea using a radiotracer approach. The release of As from different particle types into extracted gut fluid or bovine serum albumin (BSA), a gut fluid mimic, was measured. In addition, gut fluid proteins were analyzed by separating proteins via 2D gel electrophoresis, and protein peptide sequences were determined by mass spectrometry. Major ions in the gut fluid were measured by ion chromatography and metals by mass spectrometry. Percentages of particulate As release were related to As assimilation efficiencies (AEs) in polychaetes Feeding on different particle types. AEs of As were highest from radiolabeled pure diatoms (72%) and radiolabeled diatoms added to sediment (51%), lower from radiolabeled sediment (10%), and lowest from a radiolabeled iron oxide mineral, goethite (2%). It appears that As release from particles is a necessary but not sufficient requirement of As assimilation. For example, 15% of As was released from goethite into the gut fluid but only 2% was assimilated by A. succinea. Our results suggest that the likelihood of As assimilation is higher when it is bound to an organic compound of nutritional value in the ingested particles.
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modeling metal bioaccumulation in a Deposit Feeding polychaete from labile sediment fractions and from pore water
Science of The Total Environment, 2011Co-Authors: Zofia Baumann, Nicholas S FisherAbstract:Estuarine sediments are often highly enriched in particle-reactive metal contaminants and because aquatic animals have often been shown to acquire metals predominantly from their diet, benthic animals Feeding on Deposited or resuspended sediments may also accumulate metals through this uptake pathway. Laboratory experiments were performed in which the surface Deposit-Feeding polychaete, Nereis succinea, was exposed to As(+5), Cd, and Cr(+3) in pore water or in estuarine sediments with and without enrichment with algal debris. These experiments generated metal uptake parameters (assimilation efficiency of ingested metal [AE], uptake rate constant of dissolved metal, efflux rate constants following dietary or aqueous metal exposures) used in a kinetic model of metal bioaccumulation. The model showed that > 97% of the body burden of these metals is accumulated through ingested sediment. The kinetic model was further modified to consider the geochemical fractionation of the metals in the sediments because metals bound to some fractions were shown to be unavailable to these polychaetes. The modified model substituted the AE term for each metal by the percentage of metal extracted in neutral and weak acid exchangeable fractions (termed "carbonex" fraction) multiplied by the slope of the regression between the metal AE and its fractionation in carbonex. The modified model generated predictions of As, Cd, and Cr body burdens in polychaetes at three different estuarine sites that matched independent field observations at these sites (r²=0.84 for sediments without organic enrichment, r²=0.87 with organic enrichment). Model predictions that relied on total metal concentrations showed weaker relationships (r²=0.11-0.50). This study adds to the evidence for the dominance of dietary uptake of metals in aquatic animals and identifies a key sedimentary fraction of metals that can account for bioavailability of sediment-bound metals.
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relating the sediment phase speciation of arsenic cadmium and chromium with their bioavailability for the Deposit Feeding polychaete nereis succinea
Environmental Toxicology and Chemistry, 2011Co-Authors: Zofia Baumann, Nicholas S FisherAbstract:We studied the influence of sediment geochemistry on bioavailability of As, Cd, and Cr in Deposit-Feeding polychaetes. Metal phase speciation in sediments was determined with a sequential extraction scheme, and assimilation efficiencies (AEs) of ingested metals were determined by pulse-chase Feeding experiments using γ-emitting isotopes. Worms were fed sediments collected from geochemically diverse estuaries that were labeled by sorbing dissolved radiotracers or mixing with radiolabeled algae. Uptake of sediment-bound metals was compared with that from labeled algae or goethite. Metal AEs showed a positive relationship with the exchangeable and carbonate sedimentary fractions, whereas metals in iron and manganese oxides and acid-volatile sulfides, or in pyrite and other refractory material, were inversely correlated with AEs. Arsenic was most bioavailable from algae (72%), less from sediments mixed with algae (24–70%) and least from sediments labeled directly (1–12%). Arsenic AEs in sediments labeled directly showed a positive correlation with sedimentary Mn and Al and negative correlation with Fe. Cadmium AEs were positively correlated with salinity and negatively correlated with sedimentary organic C. The AEs of Cr from sediments or algae were less than 5%, but they were 34% from pure goethite. By quantifying the relationship of metal speciation in sediments with their bioavailability for Deposit-Feeding polychaetes, the present study provides new insight into understanding metal bioaccumulation in benthic invertebrates. Environ. Toxicol. Chem. 2011; 30:747–756. © 2011 SETAC
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bioavailability of dissolved and sediment bound metals to a marine Deposit Feeding polychaete
Marine Ecology Progress Series, 1999Co-Authors: Wen-xiong Wang, Ian Stupakoff, Nicholas S FisherAbstract:Assimilation efficiencies (AEs) of trace elements (Ag, Cd, Co, Se and Zn) in a marine Deposit-Feeding polychaete, Nereis succinea, from ingested sediments were measured using a pulse-chase radiotracer Feeding technique. Radiolabeled sediments were encapsulated and fed to the worms for 1 h, after which the worms were allowed to depurate their ingested materials for 3 d. The ranges of AEs were 12 to 36% for Ag, 5 to 44% for Cd, 35 to 96% for Co, 29 to 60% for Se and 21 to 59% for Zn. Trace metal assimilation was little affected by sediment source and sediment grain size. Metals (Ag, Cd, Co and Zn) associated with anoxic sediments were assimilated with a significantly lower efficiency than metals from oxic sediments. The AE of Cd decreased with the duration of sediment radiolabeling; AEs of Ag, Co, Se and Zn were weakly affected by sediment aging. Metal uptake in worms from the dissolved phase was proportional to metal concentration in the dissolved phase, although there was some evidence of Cd and Zn regulation in response to an increase in ambient concentrations. Uptake rate constants were highest for Ag, followed by Zn > Co > Cd > Se. By incorporating metal influx from both the dissolved and particulate (sediment) phases, a bioenergetic-based kinetic model indicates that most (>98%) of the Cd, Co, Se and Zn in polychaetes arises from sediment ingestion due to the high ingestion rates of these animals and the low uptake rate of metals from the dissolved phase (porewater or overlying water). For Ag, approximately 5 to 35 % is due to uptake from the dissolved phase. Our study suggests that the establishment of sediment quality criteria must consider sediment as a potentially important source for metal uptake in benthic invertebrates.
Valery E Forbes - One of the best experts on this subject based on the ideXlab platform.
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long term effects of sediment associated silver nanoparticles and silver nitrate on the Deposit Feeding polychaete capitella teleta
Aquatic Toxicology, 2021Co-Authors: Maria Bille Nielsen, Janna M Vavra, Annemette Palmqvist, Valery E ForbesAbstract:Abstract Aquatic sediments are predicted to be an important sink for released silver nanoparticles (AgNPs). Knowing the long-term effects of AgNPs on benthic Deposit-feeders is therefore an important step towards assessing their potential environmental risks. The aim of this study was to examine the effects on survival, growth and reproduction of the Deposit-Feeding polychaete Capitella teleta exposed for ten weeks to sediment-associated un-coated AgNPs or silver nitrate (AgNO3). C. teleta exhibited tolerance towards exposure to both AgNPs and AgNO3. Significant effects were observed for percentage of pairs that reproduced as well as worm growth after eight weeks, but the effects did not show a clear concentration- or Ag type-dependent pattern. Further investigations of long-term effects of un-coated AgNPs in additional sediment-dwelling organisms are needed and should involve comparisons to coated AgNPs.
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effects of sediment associated copper to the Deposit Feeding snail potamopyrgus antipodarum a comparison of cu added in aqueous form or as nano and micro cuo particles
Aquatic Toxicology, 2012Co-Authors: Chengfang Pang, Henriette Selck, Valery E Forbes, Superb K Misra, Deborah Berhanu, Agnieszka Dybowska, Eugenia ValsamijonesAbstract:Increasing use of engineered nanoparticles (NPs) is likely to result in release of these particles to the aquatic environment where the NPs may eventually accumulate in sediment. However, little is known about the potential ecotoxicity of sediment-associated engineered NPs. We here consider the case of metal oxide NPs using CuO to understand if the effects of NPs differ from micron-sized particles of CuO and aqueous Cu (CuCl₂). To address this issue, we compared effects of copper added to the sediment as aqueous Cu, nano- (6 nm) and micro- (<5 μm) CuO particles on the Deposit-Feeding snail, Potamopyrgus antipodarum. Effects were assessed as mortality, specific growth rate, Feeding rate, reproduction, and bioaccumulation after 8 weeks of exposure to nominal concentrations of 0, 30, 60, 120 and 240 μg Cu/g dry weight sediment. The results demonstrate that copper added to sediment as nano-CuO had greater effects on growth, Feeding rate, and reproduction of P. antipodarum than copper added as micro-CuO or aqueous Cu. P. antipodarum accumulated more copper in the nano-CuO treatment than in aqueous Cu or micro-CuO treatments, indicating that consideration of metal form may be important when assessing risks of metals to the aquatic environment.
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effects of chronic metal exposure and sediment organic matter on digestive absorption efficiency of cadmium by the Deposit Feeding polychaete capitella species i
Environmental Toxicology and Chemistry, 1999Co-Authors: Henriette Selck, Alan W Decho, Valery E ForbesAbstract:Organic matter such as humic acid and bacterial slime exopolymer are common in estuarine and coastal sediments, where they are ingested by animals that process particulate detritus. Both humic acid (HA; refractory) and exopolymer (EPS; easily digestible) bind metals and therefore might represent a source of particulate-bound metals to Deposit-Feeding organisms. This study examined how cadmium preexposure (3 and 30 μg Cd/g dry wt. sed.), gut passage time (GPT), and quality and quantity of the organic coating on sediment particles interact to determine cadmium absorption efficiency (Cd-AE) in Capitella sp. I. Pulse-chase experiments using 109Cd and 51Cr were used to determine Cd-AE in individual worms. Worms were given a pulse of carbon-cleaned, HA-coated or EPS-coated sediment particles. The third treatment was divided into three EPS concentrations (high, medium, and low). A 5-d preexposure to cadmium did not affect the egestion rates during either the preexposure period or the chase phase. Worms given a pulse of carbon-cleaned particles exhibited higher egestion rates during the chase phase than worms given a pulse of organic-coated particles, and no differences were seen in egestion rate between worms exposed to HA- and high-EPS-coated particles. Egestion rates decreased with increasing EPS concentration. The presence of refractory organic material decreased the absorption efficiency of cadmium from sediment relative to Cd-AE from carbon-cleaned sediment but not relative to Cd-AE from sediment coated with a high concentration of EPS. The Cd-AE increased linearly with increasing exopolymer coating on sediment particles. Overall, Cd-AE increased with increasing gut passage time in worms that were not preexposed, although Cd-AE from HA-coated particles was independent of gut passage time. Preexposure to cadmium reversed the relationship between gut passage time and cadmium absorption efficiency. Thus, the implications are that sedimentary organic matter and worm physiology might be especially important in controlling metal bioavailability in Deposit-Feeding organisms and should be considered in sediment quality approaches.
Wen-xiong Wang - One of the best experts on this subject based on the ideXlab platform.
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Arsenic biokinetics and bioavailability in Deposit-Feeding clams and polychaetes.
The Science of the total environment, 2018Co-Authors: Wei Zhang, Wen-xiong WangAbstract:Abstract In the present study, the arsenic (As) biokinetics and bioavailability in two Deposit-Feeding invertebrates (clams Gafrarium tumidum and polychaetes Nereis succinea) were quantified. Radiotracer techniques were applied to measure the dissolved uptake rate, dietary assimilation efficiency and efflux of As by the clams and polychaetes. Simultaneously, arsenic species analysis was conducted to examine the As biotransformation following dietary uptake. The radiotracer results showed that the uptake rate constant and efflux rate constant were 0.068 L/g/d and 0.07 d− 1, and 0.173 L/g/d and 0.09 d− 1, in the clams and polychaetes, respectively. Sediments labeled for different times (1.5–60 d) with different inorganic/organic As percentages led to diverse assimilation efficiencies of As (35.1–56.1% in the clams, and 51.6–72.6% in the polychaetes). Modeling calculations showed that sediment was a significant source for As bioaccumulation in the two Deposit-feeders. After Feeding on the spiked sediments, inorganic As (75.6%) was initially the predominant form, but arsenobetaine (AsB) became the predominant compound (> 90%) in the clams and polychaetes during depuration, suggesting biotransformation of inorganic As. Combined with the biokinetics and biotransformation measurements, we showed that AsB was more efficiently assimilated and tended to be accumulated, whereas As(III) was less efficiently assimilated and more rapidly eliminated by the two invertebrates. This study demonstrated that As speciation in the sediments as a significant source for As bioaccumulation caused different bioavailability in Deposit-Feeding clams and polychaetes.
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influences of aging on the bioavailability of sediment bound cd and zn to Deposit Feeding sipunculans and soldier crabs
Environmental Toxicology and Chemistry, 2006Co-Authors: Huan Zhong, Wen-xiong WangAbstract:The radiotracer technique was used to assess the influences of sediment-metal contact time or aging (up to two years) on the bioavailability and geochemical speciation of Cd and Zn in sediments. Bioavailability was quantified by measuring the assimilation efficiency of metals in two Deposit-Feeding invertebrates (sipunculans and soldier crabs) and the extraction by the sipunculans' gut juices. Sediment aging generally did not significantly affect the Cd speciation in the sediments, Cd assimilation, and Cd extraction. In contrast, sediment aging significantly affected the Zn distribution in different geochemical phases and the Zn bioavailability. With increasing aging, the Zn distributed in the carbonate phase decreased, whereas that in the reducible phase increased. Accordingly, the Zn gut-juice extraction decreased significantly. Two years of aging were not sufficient for Zn to be associated with the organic and residual phases. A significant positive correlation was found between Cd gut-juice extraction and assimilation efficiency. Gut-juice extraction of Cd and Zn generally increased with metal distribution in the exchangeable and carbonate phases but decreased with that in the reducible phase. Our results suggest that different metals are influenced by sediment aging differently and that geochemical speciation analysis is useful in studying the bioavailability of sediment-bound metals. This study may have implications for designing sediment toxicity tests using spiking techniques and for understanding the fates of anthropogenically derived metals in sediments.
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metal exposure and bioavailability to a marine Deposit Feeding sipuncula sipunculus nudus
Environmental Science & Technology, 2002Co-Authors: Qilun Yan, Wen-xiong WangAbstract:Sediments often constitute the major repository of metals and may be a potential source for metal bioaccumulation by marine Deposit- and suspension-Feeding invertebrates. In this study, we compared the uptake of Cd, Cr, and Zn from solute and sedimentary sources by a Deposit-Feeding peanut worm, Sipuncula nudus. The uptake rate constants determined for the three metals were generally low and were 0.0016-0.0020 l g -1 d -1 for Cd, 0.0107-0.0269 l g -1 d -1 for Cr, and 0.0235-0.0463 l g -1 d -1 for Zn. The uptake rate of Zn increased at a disproportionately slower rate with increasing Zn concentrations in the ambient water, indicating that Zn may have been partially regulated at a high Zn concentration. The assimilation efficiency (AE) of the metals was determined using a pulse-chase radiotracer technique. The AEs were in the range of 6-30% for Cd, 0.5-8% for Cr, and 5-15% for Zn. The sediment grain size and radiolabeling duration (between 7 and 30 d) did not affect the metal AE. There was no major difference in the metal AE from natural sediment collected from a contaminated environment. The desorption of metals from the radiolabeled sediments was also concurrently measured using the gut juice extracted from the sipuncula. Up to 63% of Cd was extracted by the gut juice, whereas only <4% of Cr was extracted by the gut juice. There was a significant relationship between the metal AE and the metal extraction by gut juice for Cd, whereas no significant relationship was found for Cr and Zn. Thus, the bioavailability study using the gut juice extraction method may indicate Cd bioaccumulation in the sipuncula. With a simple kinetic model, we show that the bioaccumulation of Cd, Cr, and Zn in the worms is largely dominated by sediment ingestion due to the low uptake from the solute phase as well as the high metal concentrations in the sediment. Thus, sediment should be considered as a direct source for metal accumulation in sipuncula when setting the sediment quality criteria.
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bioavailability of dissolved and sediment bound metals to a marine Deposit Feeding polychaete
Marine Ecology Progress Series, 1999Co-Authors: Wen-xiong Wang, Ian Stupakoff, Nicholas S FisherAbstract:Assimilation efficiencies (AEs) of trace elements (Ag, Cd, Co, Se and Zn) in a marine Deposit-Feeding polychaete, Nereis succinea, from ingested sediments were measured using a pulse-chase radiotracer Feeding technique. Radiolabeled sediments were encapsulated and fed to the worms for 1 h, after which the worms were allowed to depurate their ingested materials for 3 d. The ranges of AEs were 12 to 36% for Ag, 5 to 44% for Cd, 35 to 96% for Co, 29 to 60% for Se and 21 to 59% for Zn. Trace metal assimilation was little affected by sediment source and sediment grain size. Metals (Ag, Cd, Co and Zn) associated with anoxic sediments were assimilated with a significantly lower efficiency than metals from oxic sediments. The AE of Cd decreased with the duration of sediment radiolabeling; AEs of Ag, Co, Se and Zn were weakly affected by sediment aging. Metal uptake in worms from the dissolved phase was proportional to metal concentration in the dissolved phase, although there was some evidence of Cd and Zn regulation in response to an increase in ambient concentrations. Uptake rate constants were highest for Ag, followed by Zn > Co > Cd > Se. By incorporating metal influx from both the dissolved and particulate (sediment) phases, a bioenergetic-based kinetic model indicates that most (>98%) of the Cd, Co, Se and Zn in polychaetes arises from sediment ingestion due to the high ingestion rates of these animals and the low uptake rate of metals from the dissolved phase (porewater or overlying water). For Ag, approximately 5 to 35 % is due to uptake from the dissolved phase. Our study suggests that the establishment of sediment quality criteria must consider sediment as a potentially important source for metal uptake in benthic invertebrates.
B. D. Smith - One of the best experts on this subject based on the ideXlab platform.
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assessing metal bioaccumulation from estuarine sediments comparative experimental results for the polychaete arenicola marina
Journal of Soils and Sediments, 2013Co-Authors: Carmen M Casadomartinez, B. D. SmithAbstract:Purpose The purpose of this paper is to compare three approaches for providing information on the bioaccumulation potential of metals from contaminated sediments to the Deposit-Feeding polychaete Arenicola marina.
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bioaccumulation of arsenic from water and sediment by a Deposit Feeding polychaete arenicola marina a biodynamic modelling approach
Aquatic Toxicology, 2010Co-Authors: M C Casadomartinez, B. D. Smith, Samuel N Luoma, P S RainbowAbstract:Abstract Arsenic bioaccumulation in the Deposit-Feeding polychaete Arenicola marina has been investigated using biodynamic modelling. Radiotracer techniques were used to determine the rates of uptake of As as arsenate from water and sediment and its subsequent efflux in the laboratory. Lugworms accumulated As from solution linearly at concentrations of 2–20 μg l−1, with a corresponding uptake rate constant of 0.1648 ± 0.0135 l g−1 d−1. 7.8 ± 0.8% (assimilation efficiency) of the As ingested bound to sediments was retained after egestion of unassimilated metal. Elimination of As followed a two-compartment model, with mean efflux rate constants (from the slow pool) very similar for As accumulated from solution and ingested sediments (0.0449 ± 0.0034 and 0.0478 ± 0.0225 d−1, respectively) and a corresponding biological half-time of roughly 15 d. A biodynamic model was constructed and validated through the comparison of biodynamic model predictions against measured bioaccumulated concentrations in lugworms from five UK estuaries. The model accurately predicted bioaccumulated As concentrations in lugworms using mean values of relevant physiological parameters (uptake rate, efflux rate and growth rate constants), a site-specific ingestion rate (calculated according to mean worm size and sediment organic matter content and expressed as the rate of ingestion of the mass of fine sediment), a site-specific sediment concentration measured after HCl extraction, and a standard dissolved As concentration. This combination of parameters showed that sediment ingestion contributed 30–60% of the total As accumulated by lugworms at the studied sites, depending on the different geochemistry at each site. This study showed that it is difficult to predict accurately As bioaccumulation at sites with different chemistries, unless that chemistry is taken into account.
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bioaccumulation of arsenic from water and sediment by a Deposit Feeding polychaete arenicola marina a biodynamic modelling approach
Aquatic Toxicology, 2010Co-Authors: M C Casadomartinez, B. D. Smith, Samuel N Luoma, P S RainbowAbstract:Arsenic bioaccumulation in the Deposit-Feeding polychaete Arenicola marina has been investigated using biodynamic modelling. Radiotracer techniques were used to determine the rates of uptake of As as arsenate from water and sediment and its subsequent efflux in the laboratory. Lugworms accumulated As from solution linearly at concentrations of 2-20 microg l(-1), with a corresponding uptake rate constant of 0.1648+/-0.0135 l g(-1)d(-1). 7.8+/-0.8% (assimilation efficiency) of the As ingested bound to sediments was retained after egestion of unassimilated metal. Elimination of As followed a two-compartment model, with mean efflux rate constants (from the slow pool) very similar for As accumulated from solution and ingested sediments (0.0449+/-0.0034 and 0.0478+/-0.0225 d(-1), respectively) and a corresponding biological half-time of roughly 15 d. A biodynamic model was constructed and validated through the comparison of biodynamic model predictions against measured bioaccumulated concentrations in lugworms from five UK estuaries. The model accurately predicted bioaccumulated As concentrations in lugworms using mean values of relevant physiological parameters (uptake rate, efflux rate and growth rate constants), a site-specific ingestion rate (calculated according to mean worm size and sediment organic matter content and expressed as the rate of ingestion of the mass of fine sediment), a site-specific sediment concentration measured after HCl extraction, and a standard dissolved As concentration. This combination of parameters showed that sediment ingestion contributed 30-60% of the total As accumulated by lugworms at the studied sites, depending on the different geochemistry at each site. This study showed that it is difficult to predict accurately As bioaccumulation at sites with different chemistries, unless that chemistry is taken into account.
Zofia Baumann - One of the best experts on this subject based on the ideXlab platform.
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factors influencing the assimilation of arsenic in a Deposit Feeding polychaete
Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2012Co-Authors: Zofia Baumann, Antonius Koller, Nicholas S FisherAbstract:Abstract We investigated mechanisms leading to the assimilation of particle-bound arsenic (As) ingested by the Deposit-Feeding polychaete Alitta succinea using a radiotracer approach. The release of As from different particle types into extracted gut fluid or bovine serum albumin (BSA), a gut fluid mimic, was measured. In addition, gut fluid proteins were analyzed by separating proteins via 2D gel electrophoresis, and protein peptide sequences were determined by mass spectrometry. Major ions in the gut fluid were measured by ion chromatography and metals by mass spectrometry. Percentages of particulate As release were related to As assimilation efficiencies (AEs) in polychaetes Feeding on different particle types. AEs of As were highest from radiolabeled pure diatoms (72%) and radiolabeled diatoms added to sediment (51%), lower from radiolabeled sediment (10%), and lowest from a radiolabeled iron oxide mineral, goethite (2%). It appears that As release from particles is a necessary but not sufficient requirement of As assimilation. For example, 15% of As was released from goethite into the gut fluid but only 2% was assimilated by A. succinea. Our results suggest that the likelihood of As assimilation is higher when it is bound to an organic compound of nutritional value in the ingested particles.
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modeling metal bioaccumulation in a Deposit Feeding polychaete from labile sediment fractions and from pore water
Science of The Total Environment, 2011Co-Authors: Zofia Baumann, Nicholas S FisherAbstract:Estuarine sediments are often highly enriched in particle-reactive metal contaminants and because aquatic animals have often been shown to acquire metals predominantly from their diet, benthic animals Feeding on Deposited or resuspended sediments may also accumulate metals through this uptake pathway. Laboratory experiments were performed in which the surface Deposit-Feeding polychaete, Nereis succinea, was exposed to As(+5), Cd, and Cr(+3) in pore water or in estuarine sediments with and without enrichment with algal debris. These experiments generated metal uptake parameters (assimilation efficiency of ingested metal [AE], uptake rate constant of dissolved metal, efflux rate constants following dietary or aqueous metal exposures) used in a kinetic model of metal bioaccumulation. The model showed that > 97% of the body burden of these metals is accumulated through ingested sediment. The kinetic model was further modified to consider the geochemical fractionation of the metals in the sediments because metals bound to some fractions were shown to be unavailable to these polychaetes. The modified model substituted the AE term for each metal by the percentage of metal extracted in neutral and weak acid exchangeable fractions (termed "carbonex" fraction) multiplied by the slope of the regression between the metal AE and its fractionation in carbonex. The modified model generated predictions of As, Cd, and Cr body burdens in polychaetes at three different estuarine sites that matched independent field observations at these sites (r²=0.84 for sediments without organic enrichment, r²=0.87 with organic enrichment). Model predictions that relied on total metal concentrations showed weaker relationships (r²=0.11-0.50). This study adds to the evidence for the dominance of dietary uptake of metals in aquatic animals and identifies a key sedimentary fraction of metals that can account for bioavailability of sediment-bound metals.
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relating the sediment phase speciation of arsenic cadmium and chromium with their bioavailability for the Deposit Feeding polychaete nereis succinea
Environmental Toxicology and Chemistry, 2011Co-Authors: Zofia Baumann, Nicholas S FisherAbstract:We studied the influence of sediment geochemistry on bioavailability of As, Cd, and Cr in Deposit-Feeding polychaetes. Metal phase speciation in sediments was determined with a sequential extraction scheme, and assimilation efficiencies (AEs) of ingested metals were determined by pulse-chase Feeding experiments using γ-emitting isotopes. Worms were fed sediments collected from geochemically diverse estuaries that were labeled by sorbing dissolved radiotracers or mixing with radiolabeled algae. Uptake of sediment-bound metals was compared with that from labeled algae or goethite. Metal AEs showed a positive relationship with the exchangeable and carbonate sedimentary fractions, whereas metals in iron and manganese oxides and acid-volatile sulfides, or in pyrite and other refractory material, were inversely correlated with AEs. Arsenic was most bioavailable from algae (72%), less from sediments mixed with algae (24–70%) and least from sediments labeled directly (1–12%). Arsenic AEs in sediments labeled directly showed a positive correlation with sedimentary Mn and Al and negative correlation with Fe. Cadmium AEs were positively correlated with salinity and negatively correlated with sedimentary organic C. The AEs of Cr from sediments or algae were less than 5%, but they were 34% from pure goethite. By quantifying the relationship of metal speciation in sediments with their bioavailability for Deposit-Feeding polychaetes, the present study provides new insight into understanding metal bioaccumulation in benthic invertebrates. Environ. Toxicol. Chem. 2011; 30:747–756. © 2011 SETAC