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Toxicokinetics and Mussel Watch: Addressing Interspecies Differences for Coastal Cadmium Contamination Assessment

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... In contrast, studies have reported that the k e s for Cu and Zn in M. sikamea is around 0.08 d −1 , suggesting that M. sikamea is capable of effluxing a portion of these metals. Notably, the k e s for Cd in both M. angulata and M. sikamea is also close to 0 d −1 [20,43]. These findings suggest that the primary factors controlling interspecies differences in heavy metal accumulation in oysters are physiological in nature. ...
... In contrast, studies have reported that the s for Cu and Zn in M. sikamea is around 0.08 d −1 , suggesting that M. sikamea is capable of effluxing a portion of these metals. Notably, the s for Cd in both M. angulata and M. sikamea is also close to 0 d −1 [20,43]. These findings suggest that the primary factors controlling interspecies differences in heavy metal accumulation in oysters are physiological in nature. ...
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Intertidal bivalves are periodically exposed in air. It is tempting to speculate that the organisms would temporarily escape from contaminants when they are out of water and thus have lower risks. In this study, we tested this speculation by investigating cadmium (Cd) toxicokinetics in an intertidal mussel, Xenostrobus atratus, under the effects of tidal exposure using simulated tidal regimes. The uptake rate constant (ku) of Cd ranged from 0.045 L g⁻¹ d⁻¹ to 0.109 L g⁻¹ d⁻¹, whereas the elimination rate constant (ke) of Cd ranged from 0.029 d⁻¹ to 0.091 d⁻¹. Cd bioaccumulation was slightly higher in the continuously immersed mussels than the alternately immersed mussels, but much lower than what would be expected if assuming bioaccumulation being proportional to immersion duration. Cd uptake was observed even when mussels were exposed in air, due to uptake of Cd dissolved in mantle cavity fluid and internalization of Cd adsorbed on mussel tissues. Overall, tidal height showed limited effects on Cd bioaccumulation, consistent with the trend of Cd concentrations found in X. atratus collected from different tidal heights. The mantle cavity uptake mechanism is expected to be applicable to other contaminants and bivalves, and should have important implications in risk assessments for intertidal environment.
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The Yellow Sea Large Marine Ecosystem (YSLME) is an important socioeconomic zone in Asia, but has been deteriorated by various environmental pollutants over the last half century. However, comprehensive coastal pollution assessments, particularly for heavy metals (HMs), have been limited from an international perspective. Here, we first evaluate coastal HM pollution in sediment and water from 119 riverine, estuarine, and marine locations along the BS and Yellow Sea to perform a comparative assessment between the two countries of China and South Korea. The occurrence, distribution, sources, multimedia fate, interactions, associated environmental factors, and potential ecological risks relating to the HM pollution are widely addressed. Eight typical HMs (As, Hg, Zn, Cu, Pb, Cd, Cr, and Ni) were targeted in both sediments and water, and in situ water properties (pH, dissolved oxygen, salinity, and temperature) and sediment properties (pH and organic matter (OM) content) were analyzed. The results indicated that As, Cd, Cr, Cu, Ni, and Pb concentrations in water were higher in the estuarine area than those in riverine and marine areas and that particularly severe HM pollution was evidenced in the BS. The dominant elements in pollution hot spots varied greatly among the countries and regions. According to the geo-accumulation index (Igeo) and pollution load index (PLI) values, the sediments exhibited high Hg and Pb pollution in the BS; high As, Hg, and Pb pollution in the Yellow Sea of China; and high Cd and Hg pollution in the Yellow Sea of South Korea. In general, the sediments were moderately contaminated by HMs based on the high PLI (>1.0) and risk index (RI) values (>160). Ni and Cr in the sediment mainly originated from geogenic sources, while the other elements (Zn, As, Cd, Cu, Hg, and Pb) were primarily linked to anthropogenic sources. Based on the partial redundancy analysis, we found that environmental factors, especially OM, contributed significantly to the concentrations of HMs in both the sediments and water. The sediment HMs significantly contributed to the waterborne HMs due to their release from the sediments to the water column. An overall assessment of the contamination status, spatial distribution, and potential sources of HMs suggested that the water-sediment interaction of HMs and the influence by environmental factors should be subsequently considered for a better understanding of the multimedia fate of HMs in the given dynamic YSLME system or similar environments elsewhere.
Article
Bivalve farming is a major European aquaculture activity, representing 48.5% of total biomass produced. Italy is one of the largest consumers of oysters but local production does not meet the market demand. Italy has approximately 384,000 ha of shallow lagoons in its coastal area, already devoted to extensive aquaculture activities, which could also represent potential locations for Pacific oyster (Crassostrea gigas, Thunberg, 1793) farming. The aim of this study is to enhance Pacific oyster farming in shallow coastal lagoons by testing novel farming technologies and validating an existing bioenergetic growth model (ShellSIM). Commercial performance of Pacific oysters and associated environmental parameters were monitored in two Sardinian coastal lagoons (San Teodoro and Santa Gilla, Italy). Oyster growth and survival were compared during a production cycle for two rearing systems: traditional systems (floating bags or lanterns) and Ortac units. The latter has not been previously tested in coastal lagoons. Measured performances were compared with ShellSIM predictions to evaluate the model's ability to predict growth and the potential production in other coastal lagoons. Results showed that at the end of a six months cycle the oysters mean weight and Condition Index were significantly higher (p value< 0.05) in floating bags than in Ortac, (55.8 ± 0.9 g and 50.1 ± 1.3 28 g; 4.6 ± 0.1 and 3.9 ± 0.1respectively). Also, the minimum commercial size (40 g) was reached by 98 % and 68 % of the oyster farmed in floating bags and Ortac units respectively. On the other hand, oysters reared in the Ortac showed a higher survival than in the floating bags (95.8 ± 0.9 % 31 and 82.1 ± 3.4 %, respectively). ShellSIM growth predictions were highly correlated with the observed data in both lagoons. However, high values for root mean square deviation (RMSD) indicated that ShellSIM predictions were significantly validated for San Teodoro lagoon but not for Santa Gilla suggesting further tailoring to some environmental conditions to produce more realistic growth predictions. Results of this study indicate that both floating bags and Ortac system should be employed during the production cycle to maximise oysters' survival and growth performances. Furthermore, this study provides a new validated tool to farmers and stakeholders to monitor oysters' performances and estimate productivity in local waters.
Article
Microplastics (MP; 1 µm–1 mm) of various shapes and compositions are ingested by numerous marine animals. Recently, proposals have been made to adopt bivalve molluscs as bioindicators of MP pollution. To serve as indicators of MP pollution, however, the proposed organisms should ingest, without bias, the majority of plastic particles to which they are exposed. To test this premise, eastern oysters, Crassostrea virginica, and blue mussels, Mytilus edulis, were offered variously sized polystyrene microspheres (diameters 19-1000 µm) and nylon microfibers (lengths 75-1075 x 30 µm), and the proportion of each rejected in pseudofeces and egested in feces determined. For both species, the proportion of microspheres rejected increased from ca. 10-30% for the smallest spheres to 98% for the largest spheres. A higher proportion of the largest microsphere was rejected compared with the longest microfiber, but similar proportions of microfibers were ingested regardless of length. Differential egestion of MP also occurred. As a result of particle selection, the number and types of MP found in the bivalve gut will depend upon the physical characteristics of the particles. Thus, bivalves will be poor bioindicators of MP pollution in the environment, and it is advised that other marine species be explored.
Article
Comprehensive information on heavy metals in coastal waters at national scale of China is limited. Therefore, this study investigated the distribution, pollution, and ecological-health risks of heavy metals in coastal waters along 18,000 km coastline of China. Total 13 target heavy metals in coastal waters along coastline of China showed drastic spatial variations with average concentrations ranging from .14 (Cd) to 136.26 (Cu) μg/L. Cu was the dominant heavy metal with the maximal concentration of 1485.92 μg/L. Three methods including heavy metal pollution index (HPI), Nemerow index (NI), and contamination degree (CD) were adopted to explore heavy metal pollution. HPI obtained the worst-case evaluation results to illustrate that heavy pollution occurred at over 50% of sampling sites. Anthropogenic sources were the main sources of heavy metals in the coastal waters. Approximately 28.13% and 9.38% of sampling sites illustrated considerable and very high ecological risks, respectively. Metals including Cu, As, and Hg were the main pollution and risk contributors. Heavy metals in coastal waters posed high cancer risks and unacceptable non-cancer risks to both adults and children. Therefore, effective control of heavy metals is necessary for regional sustainability and well-beings of residents in coastal regions of China.
Article
This review evaluates the three dynamic models (biokinetic model: BK, physiologically based pharmacokinetic model: PBPK, and toxicokinetic-toxicodynamic model: TKTD) in our understanding of the key questions in metal ecotoxicology in aquatic systems, i.e., bioaccumulation, transport and toxicity. All the models rely on the first-order kinetics principle of metal uptake and elimination. The BK model basically treats organisms as a single compartment, and is both physiologically and geochemically based. With a good understanding of each kinetic parameter, bioaccumulation of metals in any aquatic organisms can be studied holistically and mechanistically. Modeling efforts are not merely restrained from the prediction of metal accumulation in the tissues, but instead provide the direction of the key processes that need to be addressed. PBPK is more physiologically based since it mainly addresses the transportation, transformation and distribution of metals in the organisms. It can be treated conceptually as a multi-compartmental kinetic model, whereas the physiology is driving the development of any good PBPK model which is no generic for aquatic animals and contaminants. There are now increasingly applications of the PBPK modeling specifically in metal studies, which reveal many important processes that are impossible to be teased out by direct experimental measurements without adequate modeling. TKTD models further focus on metal toxicity in addition to metal bioaccumulation. The TK part links exposure and bioaccumulation, while the TD part links bioaccumulation and toxic effects. The separation of TK and TD makes it possible to model processes, e.g., toxicity modification by environmental factors, interaction between different metals, at both the toxicokinetic and toxicodynamic levels. TKTD models provide a framework for making full use of metal toxicity data, and thus provide more information for environmental risk assessments. Overall, the three models reviewed here will continue to provide guiding principles in our further studies of metal bioaccumulation and toxicity in aquatic organisms.
Article
Salinity has considerable effects on the toxicity of metals in estuarine waters. The effects of salinity are manifold, making it difficult to summarize for risk assessments. In this study, we separated and quantified the multiple effects of salinity on cadmium (Cd) in a toxicokinetic-toxicodynamic framework. The estuarine clam, Potamocorbula laevis, was used as a model organism. Cd bioaccumulation was measured using a stable-isotope-tracer technique; in parallel, toxicity tests were conducted. With the increase of salinity from 5 to 30, Cd uptake decreased monotonically. In contrast, the intrinsic sensitivity of organisms, measured by the toxicodynamic parameters, reached its minimum at intermediate salinities (i.e., 10 to 20). The overall salinity effects were dominated by the effects on Cd bioaccumulation; therefore, Cd toxicity decreased monotonically with the increases of salinity. The model developed in this study could provide predictions of no-effect concentration (1.7 to 34.9 μg L−1, endpoint mortality) and the median lethal concentration (LC50) of Cd at different salinities. In conclusion, we developed a framework for quantifying the multiple effects of salinity and a method for estimating no-effect concentration from acute toxicity tests, which can be used for better assessments of metal risks in estuarine waters.
Article
The profile of 11 trace metals in two commonly used biomonitors (the native oyster Crassostrea palmula and mussel Mytella strigata) from Estero de Urias lagoon, Gulf of California, were studied for six months, covering both dry and wet seasons. Metal concentrations in these two bivalves were compared with concentrations accumulated by Artificial Mussels (AMs) deployed alongside during the same period. Significant temporal variations in Cd, Cr and Mn were observed in both bivalve species and AMs. Temporal changes were observed for Fe in both bivalve species, Pb in oyster only and Cu in both AMs and oysters, revealing seasonal changes in inputs and/or chemical forms of these metals in the lagoon. Significant correlations for Cd, Cr and Cu were found in mussels and oysters, but their Co, Fe, Mn and Zn profiles were very different, despite these two species being taxonomically closely related and often used as biomonitors for metals. Interestingly, Hg and U were detected in AMs but not in oysters and mussels. The difference in metal profile in oysters, mussels and AMs revealed in the present study clearly showed that different biomonitors and AM take up metals differentially from the same environment, and metal profile in a single biomonitor or AM alone therefore, cannot provide a good estimate on metal concentrations in the ambient environment. As such, different biomonitors and AM should be used in metal monitoring, in order to provide a comprehensive picture on metal levels in aquatic ecosystems. Concentrations of Ni and Pb in oysters, and Cr, Fe and Mn in mussels were among the highest reported in coastal waters worldwide. Concentrations of Pb in oysters exceeded legal limits set for bivalve mollusks in EU. Concentrations of Cr in mussels and oysters exceeded or were very close to, respectively, the legal limit for fish, crab-meat, oysters, prawns, and shrimps in Hong Kong. The results indicate a potential public health risk on human consumption of oysters and mussels commonly harvested from the Estero de Urias lagoon, and corresponding pollution control measures are deemed necessary.
Article
Metal contamination is a major problem in many estuaries. Toxicokinetic models are the useful tools for predicting metal accumulation in estuarine organisms and managing the associated ecological risks. However, obtaining toxicokinetic parameter values with sufficient predictive power is challenging for the dynamic estuarine waters. In this study, we determined the toxicokinetics of multiple metals in the oyster Crassostrea hongkongensis in a dynamic estuary polluted by metals using a 48-day transplant experiment. During the experiment, metal concentrations in oysters, water and suspended particles were intensively monitored at 3 d intervals. The toxicokinetic parameters were then estimated using the Markov chain Monte Carlo (MCMC) method. The calibrated model could well simulate the time-course of metal bioaccumulation in oysters and was further validated by predicting the bioaccumulation at another site in the estuary. Furthermore, the model was used to assess the relative importance of different pathways in metal bioaccumulation. With the MCMC method, distributions instead of single values were assigned to model parameters. This method makes the model predictions probabilistic with clearly defined uncertainties, and are thus particularly useful for the risk assessments of metals in aquatic systems.
Article
To investigate the distribution and variability of trace metal pollution in the Chinese coastal waters, over 1000 adult oyster individuals were collected from 31 sites along the entire coastline, spanning from temperate to tropical regions (Bohai Sea, Yellow Sea, East China Sea and South China Sea), between August and September 2015. Concentrations of macroelements [sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) and phosphorus (P)] and trace elements [cadmium (Cd), copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), chromium (Cr), silver (Ag), and titanium (Ti)] in these oysters were concurrently measured and analyzed. The results showed high Ti, Zn and Cu bioaccumulation in oysters from Guangdong (South China Sea) and Zhejiang (East China Sea). Oysters at Nanji Island (Wenzhou) and Daya Bay (Huizhou) accumulated significantly high concentrations of Ni and Cr. The elements in these oysters were several times higher than the national food safety limits of China. On the other hand, the present study found that normalization of metals by salinity (Na) and nutrient (P) could reflect more details of metal pollution in the oysters. Biomonitoring of metal pollution could benefit from incorporating the macroelement calibration instead of focusing only on the total metal concentrations. Overall, simultaneous measurement of macroelements and trace metals coupled with non-linear analysis provide a new perspective for revealing the underlying mechanism of trace metal bioavailability and bioaccumulation in marine organisms.
Article
Monitoring bioavailable contaminants and determining baseline conditions in aquatic environments has become an important aspect of ecology and ecotoxicology. Since the mid-1970s and the initiation of the Mussel Watch program, this has been successfully accomplished with bivalve mollusks. These (mostly) sessile organisms reliably and proportionately record changes of a range of organic and inorganic pollutants occurring in the water, food or sediment. The great majority of studies have measured the concentration of pollutants in soft tissues and, to a much lesser extent, in whole shells or fractions thereof. Both approaches come with several drawbacks. Neither soft tissues nor whole shells can resolve temporal changes of the pollution history, except through the analysis of multiple specimens collected at different times. Soft tissues and shell fractions provide time-averaged data spanning months or years, and whole shells time-averaged data over the entire lifespan of the animal. Even with regular sampling of multiple specimens over long intervals of time, the resulting chronology may not faithfully resolve short-term changes of water quality. Compounding the problem, whole shell averages tend to be non-arithmetic and non-linear, because shell growth rate varies through seasons and lifetime, and different shell layers often vary ultrastructurally and can thus be chemically different from each other. Mussel Watch could greatly benefit from the potential of bivalve shells in providing high-resolution, temporally aligned archives of environmental variability. So far, only circa a dozen studies have demonstrated that the sclerochronological approach – i.e., combined growth pattern and high-resolution chemical analyses – can provide sub-seasonally to annually resolved time-series documenting the history of pollution over centuries and even millennia. On the other hand, the sclerochronological community has failed to fully appreciate that the formation of the shell and its chemical composition is controlled by the soft parts and that a robust interpretation of the shell record requires a detailed understanding of bivalve physiology, behavior and ecology. This review attempts to bring together the Mussel Watch and sclerochronology communities and lay the foundation of a new subdiscipline of the Mussel Watch: retrospective environmental biomonitoring. For this purpose, we provide an overview of seminal work from both fields and outline potential future research directions.
Article
We chronicle the extensive influence over the past forty years of Professor Edward D. Goldberg and his call in 1975 for a "Mussel Watch" or bivalve sentinel organism approach to assess geographic status and temporal trends of several chemicals of environmental concern in the coastal ocean. Examples of local, regional, national and international programs are discussed briefly as are examples of interesting useful findings and limitations to the Mussel Watch concept. Mussel Watch continues to provide useful data about status and trends of chemical contamination in coastal ecosystems.
Article
Discovery of colored oysters in an estuary in Southern China raised questions on how these oysters could survive in such an unpredictable estuary. In the present study, we conducted a transplant experiment using oysters Crassostrea hongkongensis in the estuary to quantify the changes of metal biokinetics (cadmium and zinc) and the responses of metallothionein-like proteins (MTLPs). Oysters in the transplantation experiment accumulated extremely high concentrations of Cd, Cu, Cr, Ni and Zn. The present study provided the field evidence of the time-course coupling relationship between Cd and Zn bioaccumulation. Over the 2-month transplantation, the uptake rate constants of Cd and Zn varied greatly during the early stage of exposure, but subsequently became comparable among the different locations. The dietary Zn assimilation remained relatively constant, whereas the Cd assimilation increased gradually with increasing period of exposure. There was no notable difference in dietary metal assimilation among the different locations. In contrast, the efflux rates quantified by the end of transplantation were 26-42% higher for Cd and 12-37% higher for Zn than that in the unexposed oysters. We further demonstrated that the incoming Cu and Zn were not stored in MTLPs pool, and that MTLPs synthesis and breakdown were little affected by metal exposure. Overall, our transplantation experiments suggested that oysters displayed rather weak ability to modify their biokinetics and metallothionein turnover under metal exposure. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Article
In the present study, seasonal variations of metal concentrations were examined in two oyster species, Crassostrea hongkongensis and Crassostrea sikamea, and in seawater from a heavily contaminated estuary and a reference estuary. Strong temporal fluctuations of metal concentration were observed in oyster tissues as well as in seawater from both estuaries, especially for the contaminated estuary and for C. hongkongensis with higher accumulation ability. A closer inter-element correlation was observed for Cu, Zn, Cr and Ni in both the dissolved and particulate phases from the contaminated site, indicating that these metals originated from the same industrial sources. Seasonal variations of metals in oysters were not significantly related to their concentrations in seawater, but were related to the variations of condition index. Our results showed that the seasonal patterns of metal concentrations in oysters were largely controlled by the biological process, while the variation as well as the concentration were dependent on the contamination levels and bioaccumulation ability.
Article
A systematic investigation was carried out to analyze the concentration levels of heavy metals in the sample seawater, sediments and biota collected from the coastal area of Yancheng City of Jiangsu Province of China. An assessment was carried out on the impact of these heavy metals in different environmental samples in terms of potential risks to ecology and also to the human population exposed to this area. Additionally, a further investigation was carried out on selected samples which were considered to pose higher level of potential risks to ecology or human health, to test their toxicity to zebrafish (Danio rerio) at early-life stage. Chemical analysis showed relatively higher concentrations of heavy metals in the seawater and biota samples collected from Xiangshui County and Binhai County. The heavy metal concentrations in different samples collected from the close vicinity of Dafeng Port were also comparable. Considering all the seawater and sediment samples, heavy metals showed a relatively moderate level of risk to ecological species; for consumption of marine organisms, heavy metals had adverse impacts on the human health. Toxicity assessment indicated the selected environmental samples or their extracts showed significant toxicity to zebrafish early-life stage, such as lethality, teratogenicity, and hatching delay (or advance). So, this current investigation provides very useful and important information on the heavy metals pollution in Jiangsu Province. Environ Toxicol Chem © 2014 SETAC.
Article
The use of bivalves as sentinel organisms for collectives of marine pollutants is evaluated with data from the U.S. Mussel Watch, 1976-1978. The utilization of soft parts and of the shells are compared for metals and plutonium. Finally, the need for a global mussel watch, emphasizing the analyses of chlorinated hydrocarbon biocides in the tropics and southern hemisphere, is presented.
Article
Radiotracer techniques were employed to quantify the rates of uptake from aqueous and dietary sources, and rates of elimination of Cd, Se and Zn by a marine predatory fish, the mangrove snapper Lutjanus argentimaculatus. The relative significance of bioaccumulation of metals by fish from water and food and the food chain transfer factor were then assessed using a kinetic modeling approach. Cd and Zn in the aqueous phase exhibited an approximately linear uptake pattern over a 1 to 2 d exposure, whereas Se exhibited a 2-compartmental uptake at a low ambient concentration, with a slow initial uptake followed by a rapid increase in Se influx. Most of the accumulated aqueous Se and Zn were incorporated into the muscles, whereas Cd was evenly distributed in the viscera and the remaining tissue, with a lower proportion in the gills. The influx rates were dependent on the ambient metal concentration and were tissue-specific for each metal. The assimilation efficiency of trace metals in fish ingesting different prey (copepods, Artemia sp. and clam tissue) ranged from 6 to 24% for Cd, 32 to 68% for Se and 15 to 46% for Zn, and decreased with an increase in ingestion rate. The efflux rate constant of Cd in fish following uptake from the dietary phase (0.047 d(-1)) was higher than that following aqueous uptake (0.025 d(-1)), whereas the efflux rate constants of Se and Zn were comparable between these 2 exposure pathways. Our modeling calculations indicate that dietary uptake of Cd and Zn dominates their accumulation in fish when zooplankton are the main prey, whereas aqueous uptake may be the dominant pathway when planktivorous fish are the dominant prey for the predatory fish. Dietary uptake always dominates Se accumulation in these fish. The modeling results also indicated that the food chain transfer factor of Cd was <0.5 in the fish regardless of the ingestion rate and the assimilation efficiency, consistent with the results of field studies. However, Se and Zn may potentially be biomagnified when the ingestion rate and assimilation efficiency are at the high end of the range possibly encountered by the predatory fish.
Article
Biomonitors can be used to establish geographical and/or temporal variations in the bioavailabilities of heavy metals in the marine environment, offering time-integrated measures of those portions of the total ambient metal load that are of direct ecotoxicological relevance. Heavy metal biomonitors need to conform to certain required characteristics, not least being metal accumulators. Use of a suite of biomonitors allows recognition of the presence and relative magnitude of different metal sources. For example, a macrophytic alga responds essentially to dissolved metal sources only, a suspension feeder like a mussel responds to metal sources in dissolved and suspended phases, and a deposit feeder responds to metal available in the sediment. Examples are given of suitable heavy metal biomonitors in the coastal waters of Europe, New Zealand, Hong Kong and China. It is not valid to compare absolute accumulated metal concentrations in biomonitors interspecifically, although interspecific comparisions of rank orders do allow cross correlations of relative bioavailabilities of heavy metals to different biomonitors at the same sites. There is a need to identify widespread cosmopolitan biomonitors to allow intra-specific comparisons of bioavailabilities between geographical areas. Such cosmopolitan biomonitors may include the alga Ulva lactuca, mussels of the genera Mytilus and Perna, the oysters Ostrea and Crassostrea, barnacles like Balanus amphitrite and Tetraclita squamosa, and the talitrid amphipod Platorchestia platensis. A major caveat in the use of such cosmopolitan biomonitors remains the need for reliable, specific taxonomic identification.
Article
The levels of four sets of pollutants (heavy-metals, artificial radionuclides, petroleum components, and halogenated hydrocarbons), have been measured in U.S. coastal waters, using bivalves as sentinel organisms. The strategies of carrying out this programme are outlined and the results from the first year's work are given. Varying degrees of pollution in U.S. coastal waters have been indicated by elevated levels of pollutants in the bivalves, which comprised certain species of mussels and oysters and were collected at over one hundred localities.
Article
Green lipped mussels, Perna viridis, and blue mussels, Mytilus edulis, were collected from seven locations along the east coast of China in September and October 2001. The mussel tissues were analyzed for metals (Ag, As, Cd, Cr, Ni, Pb, Se, Zn, Cu, Fe and Hg), and trace organic contaminants including organochlorine compounds (OCs), polycyclic aromatic hydrocarbons (PAHs; based on 24 individual PAHs), polychlorinated biphenyls (PCBs) and petroleum hydrocarbons (PHCs). Maximum concentrations of Ag, As, Cd, Cr, Ni, Pb, Se, Zn, Cu, Fe and Hg in the mussel tissues were 0.14, 26.76, 5.31, 15.72, 4.78, 2.93, 7.40, 231.0, 54.17, 1002 and 317.3 microg/g dry weight respectively. Levels of DDTs, PAHs, PCBs and PHCs in the mussel samples were 14-640, 456-3495, 1-13 ng/g and 621-2863 microg/g dry weight, respectively. Results of this study indicated that contaminant levels were, in general, higher or at least comparable to those reported in other local or regional studies. Mussel samples collected in Chongming Dao in Shanghai and Jiao Zhou Wan in Qingdao had significantly higher levels of metal and trace organic contaminants among the seven sampling stations. Examination of the contaminant profiles suggests that PHCs originated from petrogenic sources, while both petrogenic and pyrolytic sources were important for PAHs. The generally high levels of metals and organochlorine compounds are probably the result of increasingly intense industrial activities along the east coast of China. An assessment of potential risks to human health due to consumption of the mussels was undertaken for the metals, PCBs, DDTs and chlordanes, and the results indicated that all metals, except Ni, could pose a health risk to heavy seafood consumers, while Hg appears to be of concern even for low level consumers.
Article
Mussels are used as bioindicator organisms to assess bioavailable contaminant concentrations in coastal waters. This study used radiotracer methodologies to examine the bioaccumulation and efflux rates of six metals (Ag, Am, Cd, inorganic Co, organic Co [as cobalamine], Pb, and Zn) in the mussel Mytilus galloprovincialis, in which the dissolved phase and ingested phytoplankton food were compared quantitatively as sources. Mussels maintained in the laboratory in running seawater and caged in the field for up to 4 months generally displayed similar metal absorption efficiencies (AEs) and efflux rates from their soft parts. AEs from food were typically lower than radioisotope retention efficiencies from the dissolved phase and ranged from 4% for Am to about 60% for Pb; values were comparable to those reported for the common blue mussel, Mytilus edulis. Efflux rate constants from mussel soft parts (1−5% daily) were comparable to M. edulis values from short-term depurations; biological half-lives of all metals in soft parts, shells, and whole mussels typically ranged from 10 to 60 days, although exceptions were noted. Metals obtained from food were primarily bound to soft part tissues; metals from the dissolved phase were mostly associated with the mussel shells. Higher AEs and lower efflux rates of cobalamine than of inorganic Co suggest that cobalamine is a more bioavailable form of cobalt for mussels. Mussel fecal pellets were enriched with metals following ingestion, with retention half-times of the metals in the pellets ranging from 18 days for Ag to 107 days for Am. Fecal pellet deposition beneath mussel beds may play an important role in the biogeochemical cycling of these metals in coastal ecosystems. The efflux rate constants and AEs can be used in kinetic models to estimate the relative importance of food and water as source terms for metals in mussels and to predict metal concentrations in mussels under different field conditions. A sensitivity analysis was performed to show that AEs are critical parameters influencing metal concentrations in mussels (particularly for Am, Ag, and Zn), and the results from this study indicate that laboratory-derived estimates of AEs are applicable to field conditions.
Article
Oyster Crassostrea hongkongensis, a widely cultivated oyster species in Southern China, can accumulate metals (especially for Cu and Zn) to extraordinarily high concentrations (up to 3% of body dry weight). It remains unknown how they were acclimated to contaminated environment and built up such high metal concentrations in their bodies. A seven month transplantation experiment was conducted to rebuild the physiological process of acclimation in oysters to illustrate how they cope with increasing metal bioavailability. The metal concentrations increased substantially in the transplanted oysters from a reference site to a contaminated site. Our results showed that metal biokinetics in the oysters changed dramatically after suffering from metal stress. The clearance rate, dissolved uptake rate (for Cd and Zn), and metal assimilation efficiency (for Zn) was depressed, while the metal efflux rate (for Zn) was enhanced in the contaminated oysters. Beside the change of metal homeostasis, the oysters were able to sequester metals into subcellular nontoxic forms and maintain a low portion of metals distributing in the metal-sensitive fraction. This comparative bioaccumulation study of C. hongkongensis suggested that adjustment of metal biokinetics played an important role in the survival of oysters in metal contaminated environment.
Article
We measured assimilation efficiencies (AEs) from ingested algal food, uptake rates from the dissolved phase, and efflux rate constants of 4 trace elements (Cd, Co. Se and Zn) in 3 size classes (1.5, 2.5, and 5.0 cm) of the mussel Mytilus edulis. AEs of Se and Zn remained constant among the 3 body sizes. AEs of Cd decreased with increasing body size, whereas AEs of CO increased with body size The rate constant of metal uptake from the dissolved phase decreased with increasing body size, but the calculated metal absorption efficiencies remained relatively constant or increased slightly in larger mussels. Efflux rate constants were comparable among the 3 body sizes, except for Cd whlch was lost about 2 times faster in the smaller mussels than in the largest mussels. A bioenergetic-based lunetic model was used to calculate the allometric coefficient (b) of metal accumulation with mussel body size; predicted b values were comparable to field measurements However, b increased expo-nent~ally with the growth rate constant, indicating that no single b value 1s likely to be observed in nature for a specific metal. The growth rate constant is needed for the model to predict metal concen-tration and allometry of metal accumulation in mussels, especially for smaller mussels. The relative importance of trace element uptake from the dissolved phase versus particulate ingestion in the over-all metal uptake in mussels was relatively independent of mussel body size, primarily because the influx rates from the dissolved phase and from food were conlparably related to body size.
Article
Particle feeding on suspended and deposited material is a common mode of food collection among many groups of the Metazoa. In particular, many members of the Mollusca, most notably the bivalves, have specialized in particle feeding. Because suspension- and deposit-feeding activities often play significant roles in ecosystem processes, particular attention has been given to the mechanisms of particle feeding by these molluscs, and to the impacts of environmental factors upon these mechanisms.Early studies of the feeding organs of bivalve molluscs were descriptive and emphasis soon was placed upon the actual uptake of particulate material from the environment and identification of this material. Introduction of electronic particle counters led to a better understanding of the rates and efficiencies at which particle removal occurred, and the interface between food availability in the ocean and responses of these animals to temporal and spatial variability. While some early workers inferred the capabilities of these animals to select particles, it was the introduction of more advanced technologies (e.g., flow cytometry, video endoscopy, confocal microscopy) that allowed more detailed studies of the mechanisms associated with particle uptake and selection by these animals. These techniques have provided a more comprehensive analysis which clearly demonstrate that the mechanisms associated with particle feeding and selection are complex, with species-specific processes based upon both physical and chemical characteristics of the particles. In this review, we summarize prior research on particle selection in suspension- and deposit-feeding bivalve molluscs, discuss current theory and controversy regarding these processes, and propose areas for further study. In particular, more research is needed to elucidate the mechanisms responsible for particle selection, particulate characteristics that impact selection, and the intrinsic and extrinsic factors that mediate these processes.
Article
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