Concentrations In Clams Research Articles

Tapes philippinarum seed exposure to metals in polluted areas of the Venice lagoon

The concentration changes of 12 metals (As, Hg, Cd, Cr, Co, Cu, Pb, Mn, Ni, V, Zn, Fe, and Hg) in the soft tissues of Tapes philippinarum during growth were investigated. Clams were seeded in two contaminated areas of the Venice lagoon (San Giuliano and Fusina) and in an area of the Marano lagoon (Lignano Sabbiadoro) close to the clam-farm where the seed was produced. Metal trends were very different according to the considered element, the study site and the growth period. Arsenic was always higher in clam tissues than in surface sediments and suspended particles in all the three stations. Mercury, Cd and Cu were higher in the clams from Marano and Fusina but not in those from San Giuliano. Zinc and Co in clams exceeded the concentrations in the sediment and suspended particles only at Marano. The other elements (Cr, Pb, Mn, Ni, and Fe) were always higher in SPM and sediments. In general metal concentrations in clams were more highly correlated to concentrations in the suspended particles rather than in the surface sediments and in suspended clams rather than in bottom clams, nevertheless significant differences between stations and contaminants were found. Metal concentrations in clams were always lower than the European regulatory limits.

Using trace element concentrations in Corbicula fluminea to identify potential sources of contamination in an urban river

We used the biomonitor, Corbicula fluminea, to investigate the contributions of trace elements associated with different point sources and land uses in a large river. Trace elements were analyzed in tissues of clams collected from 15 tributary streams draining five land use or point source types: agriculture, forest, urban, coal-fired power plant (CFPP), and wastewater (WWTP). Clams from forested catchments had elevated Hg concentrations, and concentrations of arsenic and selenium were highest (5.0 ± 0.2 and 13.6 ± 0.9 μg g −1 dry mass (DM), respectively) in clams from CFPP sites. Cadmium concentrations were significantly higher in clams from urban and CFPP sites (4.1 ± 0.2 and 3.6 ± 0.9 μg g −1 DM, respectively). Non-metric multidimensional scaling (NMS) of tissue concentrations in clams clustered at CFPP and forest/agriculture sites at opposite ends of the ordination space, and the distribution of sites was driven by Cu, Zn, Cd, and Hg.

Trace metal concentrations in suspended particles, sediments and clams (Ruditapes philippinarum) from Jiaozhou Bay of China

Suspended particulate matter (SPM), sediments and clams were collected at three sites in Jiaozhou Bay to assess the magnitude of trace metal pollution in the area. Metal concentrations in SPM (Cu: 40.11-203; Zn: 118-447; Pb: 50.1-132; Cd: 0.55-4.39; Cr: 147.6-288; Mn: 762-1670 microg/g), sediments (Cu: 17.64-34.26; Zn: 80.79-110; Pb: 24.57-49.59; Cd: 0.099-0.324; Cr: 41.6-88.1; Mn: 343-520 microg/g) and bivalves (Cu: 6.41-19.76; Zn: 35.5-85.5; Pb: 0.31-1.01; Cd: 0.51-0.67; Mn: 27.45-67.6 microg/g) are comparable to those reported for other moderately polluted world environments. SPM showed a less clear pattern. Metal concentrations in sediments displayed a clear geographical trend with values increasing with proximity to major urban centers. The clams (on dry weight) showed a complex pattern due to the variability introduced by age-related factors. Cd showed an apparent reverse industrial trend with higher concentrations in clams collected at distant stations. Zn, Pb and Mn showed no clear geographical pattern, whereas Cu increased in the clams collected in the most industrialized area. In addition, the bioaccumulation factors (BAF) were calculated. The result indicated that the studied Ruditapes philippinarum in Jiaozhou Bay possessed different bioaccumulation capacities for Cd, Zn, Cu, Pb and Mn, and Cd, Zn had a relatively high assimilation of those metals from sediment particles. A significant relationship with clam age was observed for Zn (positive) and Cu (negative) suggesting different physiological requirements for both metals with age. Trace metal concentrations measured in the tissue of the investigated clam were in the range considered safe by the WHO for human use.

Kinetic modeling of Ag, Cd and Co bioaccumulation in the clam Macoma balthica: quantifying dietary and dissolved sources

A biokinetic model was used to better understand Ag, Cd and Co concentrations in a population of the clam Macoma balthica in San Francisco Bay. Model parameters included labora- tory-derived uptake- and loss-rate constants from food and water and field measurements of metal concentrations in food, overlying water and oxidized pore water. Parameters used in modeling were taken from recent studies of metal influx from dissolved sources and metal assimilation from ingested sediment, and from laboratory experiments and field measurements in this study. Assimilation effi- ciencies from surface sediments ranged from 12 to 22% for Ag, 6 to 13% for Cd and 8 to 20% for Co. Assimilation efficiencies from phytoplankton were higher than metal assimilation efficiencies from sediment, ranging from 36 to 42% for Ag, 47 to 55% for Cd and 27 to 33% for Co. Influx of dissolved metals from overlying water increased with increasing ambient concentration, with uptake-rate con- stants for Ag (0.34 l g -1 d -1 ) about an order of magnitude higher than for Cd and Co. Influx-rate con- stants for Ag and Cd from oxidized pore water were comparable to overlying water-rate constants, whereas the rate constant for Co influx from oxidized pore water was 3 times lower than that from overlying water. Efflux rates of all metals out of the clams ranged from 1 to 3% d -1 . To estimate the potentially bioavailable fraction of particle-bound metals, assumed to be the metal bound to particle surfaces, mean metal concentrations in shale were subtracted from metal concentrations in total sedi- ment digestions. Metal accumulation was modeled for clams that were assumed to be surface deposit- feeding and those that were filter-feeding. By adding uptake from food (surface sediment or phyto- plankton) and from dissolved sources (oxidized pore water or overlying water), the modelpredicted ranges of concentrations of Ag, Cd and Co in deposit-feeding clams are shown to be directly compa- rable to tissue concentrations in field-collected clams from San Francisco Bay. Thus, it appears that the parameters experimentally derived for M. balthica are applicable to field conditions and that the model can account for the major processes governing metal concentrations in these clams. Further, through modeling, ingested sediment was shown to be a major source for Ag and Cd under all real- istic environmental conditions, but Co accumulation was principally from the dissolved phase.

Trace metals in suspended particles, sediments and Asiatic clams ( Corbicula fluminea) of the Río de la Plata Estuary, Argentina

Suspended particulate matter (SPM), sandy sediments and Asiatic clams were collected at seven sites along 150 km of the Río de la Plata coast to assess the magnitude of trace metal pollution in the area. Metal concentrations in SPM (Cu: 7.4–109; Cr: 75–408; Mn: 525–1341 μ g −1), sediments (Cr: 16–27; Zn: 26–99; Mn: 221–489 μ g −1) and bivalves (Cd: 0.5–1.9; Ni: 1.3–6.4; Cr: 1.3–11; Mn: 15–81; Cu: 28–89; Zn: 118–316 μg g −1) are comparable to those reported for other moderately polluted world rivers. Cu levels in Asiatic clams are among the highest, similar to those reported for heavily polluted sites. SPM Cu and Cr concentrations displayed a clear geographical trend with values increasing with proximity to major urban centers. Sediments showed a less clear pattern possibly due to their coarse nature (>98% sand) and higher proportion of mineral-associated residual metals. The clams showed a complex pattern due to the variability introduced by size-related factors and the natural dynamics of SPM in the estuary. Cr and Mn showed an apparent reverse industrial trend with higher concentrations in clams collected at distant stations near the turbidity maximum zone, possibly reflecting enhanced particle retention. Cu, Cd and Ni showed no clear geographical pattern, whereas Zn increased in the clams collected in the most industrialized area. A significant relationship with clam size was observed for Cu (positive) and Zn (negative) suggesting different physiological requirements for both metals with age. A principal component analysis confirmed these geographical and size-related trends.

Accumulation and elimination of cyanobacterial hepatotoxins by the freshwater clam Anodonta grandis simpsoniana

Freshwater clams (Anodonta grandis simpsoniana) exposed to 51-55 µg · L-1 of dissolved microcystin-LR (MC-LR) in the laboratory for 3 days did not accumulate MC-LR equivalents (MC-LReq). However, clams placed in three eutrophic lakes with phytoplankton containing MC-LR (concentrations from below detection to 8.3 µg · L-1 cellular toxin) for 12-28 days accumulated the toxin (24 ± 7 to 527 ± 330 ng · g-1 MC-LReq; mean ± SE). The relative MC-LReq concentrations in clams reflected MC-LR concentrations in lake phytoplankton, but individual variation was high. In individual clams exposed for 24 days, the average MC-LReq concentration was usually greater in the visceral mass than in gills and muscle, but average toxin concentrations in the three tissues were similar (587, 310, and 364 ng · g dry weight-1). In clams removed from the lake and placed in toxin-free water, MC-LReq concentrations in tissues declined rapidly for 6 days (by 69-88%) but remained relatively stable for the remaining 15 days. Analysis of clam tissues appears to be a more sensitive MC-LR indicator than analysis of phytoplankton. Accumulation of potent cyanobacterial toxins by this clam warrants further study as many are consumed by muskrats (Ondatra zibethicus), which in turn are consumed by terrestrial predators.

Bioaccumulation of nickel and vanadium by clams ( Meretrix meretrix) living in different salinities along the Saudi coast of the Arabian Gulf

The objective of this study was to investigate bioaccumulation of nickel (Ni) and vanadium (V) in clams living in different salinity regimes along the Saudi coast of the Arabian Gulf. Several hundred clam (Meretrix meretrix), sediment, and seawater samples were collected from 12 locations. Concentrations of Ni and V were determined in these samples using an inductively coupled argon plasma analyzer. Concentrations of Ni and V in the clams varied between 0·35 and 2·61 mg kg −1 and between 0·13 and 0·35 mg kg −1 wet tissue, respectively. Analysis of variance of the data revealed significant ( P < 0·01) inter- and intra-station variations in Ni concentrations in clams. In contrast, the mean concentration of V in clams from all the stations were statistically similar. Correlation between the biometric characteristics of clams and Ni and V concentrations were not statistically significant. Significant ( P < 0·05) geographical variations in Ni and V concentrations in the sediment samples were found, with relatively higher concentrations in the northern part of the Gulf where there are many oil fields. Ni and V in the sediments were significantly ( P < 0·05) correlated, suggesting a common contamination source for these elements. Interactions between Ni and V in clams and sediment were poor.

Cadmium bioaccumulation by clams dwelling in different salinity regimes along the Saudi coast of the Arabian gulf

The objective of this study was to investigate Cd bioaccumulation in clams living in different salinities. Several hundred clams (Maritrix maritrix) and sediment samples were collected during 1985–1986 from 12 locations on the Saudi coastal areas of the Arabian Gulf. Soft tissue from each clam was removed and digested in HNO3. Sediments were also digested in HNO3. Cadmium in the recently collected seawater samples was extracted using pyrrolidine carbodithioic acid-chloroform system. Cadmium in all the collected samples was determined using an inductively coupled argon plasma analyzer. Concentrations of Cd in the sediments varied insignificantly between 0.1 and 0.22 mg kg−1. Significant geographical variations in the mean Cd concentrations in clams (P < 0.05) were found. Intrastation differences in Cd bioaccumulation were also significant. Correlation between biometric observations and Cd concentrations in clams was not significant (P < 0.05). Seawater salinity was significantly (P < 0.05) correlated to the mean Cd concentrations in clams and seawater. Cadmium accumulation in the clams was supported by the chemical behavior of Cd in seawater.

Distribution of Contaminants in Clams and Sediments from the Huron-Erie Corridor. II–Lead and Cadmium

The St. Clair River is a major center for the Canadian petrochemical industry, while the shoreline of the Detroit River is heavily urbanized. The extent of lead and cadmium discharge from these sources was assessed by determining contaminant concentrations in unionid clams ( Lampsilis radiata siliquoidea) and sediments from 102 sites in Lake St. Clair and from the Canadian side of the Detroit and St. Clair rivers. Overall, lead and cadmium levels in sediments averaged 20.5 and 0.18 mg kg −1 dry weight, respectively. These concentrations are lower than those reported in prior studies, but the decline is likely a consequence of shifts in sampling methodology and site location. Lead concentrations in clams (7.1 mg kg −1) averaged only one half those in the sediments, whereas cadmium concentrations were 30 times higher in clam tissues than in the surrounding sediments. There was a significant positive correlation between lead and cadmium concentrations in sediment, and between the concentrations of both metals and the amount of organic carbon present. There was no correlation between the level of either lead or cadmium in clams and levels in the sediments from which they were collected. Patterns of variation in contaminant concentrations support the conclusion that industries along the Canadian side of the St. Clair River are the primary source of both lead and cadmium.

PCB availability assessment of river dredging using caged clams and fish

AbstractThe effects of dredging to remove sediments contaminated with polychlorinated biphenyls (PCBs) were studied in the South Branch of the Shiawassee River in south‐central Michigan. Caged fingernail clams, Sphaerium striatinum (Lamarck), and fathead minnows, Pimephales promelas Rafinesque, were used to monitor the bioavailability of PCBs, and these data were compared with changes in water column concentrations before dredging, during dredging and up to six months after dredging was completed. Monitoring of water, clams and fish during dredging confirmed that significant amounts of PCBs were released from the sediments. At all locations downstream and in the area of the dredging, there were increases in the availability of PCBs for at least six months. PCB concentrations in clams and fish in the dredged zone increased from 64.5 to 87.95 μg/g dry weight and from 13.82 to 18.30 μg/g dry weight, respectively, after dredging. Downstream (11 km), post‐dredge uptake was also higher; however, clams showed less uptake than fish. This implied different uptake routes for the two organisms. There was no noticeable change in total PCB concentration in the water after dredging.In situ experiments were run to determine uptake curves and time to uptake equilibrium for both clams and fish. Results of tests for equilibrium uptake by fatheads agreed with literature values. Uptake maxima occurred within 20 to 30 d. For clams, maximum uptake for Aroclor 1242 occurred after 9 d. Log bioconcentration factors for clams ranged from 2.6 to 4.5 for Aroclor 1242 and from 3.0 to 4.4 for Aroclor 1254; for fish, they ranged from 3.0 to 4.4 for Aroclor 1242 and from 4.5 to 5.5 for Aroclor 1254.

Enteric Bacterial and Viral Pathogens and Indicator Bacteria in Hard Shell Clams

Enteric bacteria and virus levels were determined in hard shell clams, Mercenaria mercenaria, harvested from areas open or closed for commercial shellfishing on the basis of total coliform levels in water. Four pairs of open and closed stations were sampled seasonally over a 1-year period. Enteric viruses were isolated from 3 of 13 100-g clam samples from open beds and 6 of 15 samples from closed beds. Salmonella was found in 1 of 15 samples from closed areas, but not in any samples from open areas. No Shigella or Yersinia were isolated from clams taken from either open or closed beds. Levels of Vibrio parahaemolyticus, an indigenous estuarine microorganism, were similar in clams from open and closed areas. No statistically significant difference was found in the occurrence of enteric viruses in clams from open and closed areas. Product-moment correlations between concentrations of enteric viruses and bacteria in clams or water demonstrated no statistically significant correlations between virus concentrations in clams and total coliforms or fecal coliforms in water or total coliforms, fecal coliforms, fecal streptococci or aerobic plate counts in clams.

Concentrations of unsubstituted polycyclic aromatic hydrocarbons in softshell clams from Coos Bay, Oregon, USA

Concentrations of benzo[a]pyrene (BAP) were measured in subpopulations of softshell clams, Mya arenaria, from four intertidal sites in Coos Bay from June 1976 to June 1978. Subsequently, concentrations of 15 unsubstituted polynuclear aromatic hydrocarbons (PNAH) were determined in two subpopulations from September 1978 to August 1979. There were significant differences between BAP concentrations in clams from the four sites. For the two-year period, they were highest in clams inhabiting areas adjacent to the industrialized bayfront and lowest in clams inhabiting more remote areas. There were no significant seasonal variations in BAP concentrations during this period. During the 1978–1979 study, the average total PNAH concentration in clams from the bayfront area was 555.1 μg kg −1 compared to 76.3 μg kg −1 for clams from a more remote environment. In general, PNAH concentrations were lowest in the fall-winter and highest during the spring-summer.