Metal Concentrations In Mussels Research Articles

A comparative eco toxicological study of heavy metal concentrations in mussels collected in 2004 from the western and eastern coastal waters in the straits of Johore

The concentrations of Cu, Cd, Zn, Pb, Ni and Fe in the different soft tissues of Perna viridis from the west and east coast of The Straits of Johore (SOJ) were determined. Crystalline style (CS) recorded higher accumulation of Cu (west: 58.2 mg/kg dry weight; east: 56.0 mg/kg dry weight), Cd (west: 9.45 mg/kg dry weight; east: 3.93 mg/kg dry weight), Pb (west: 49.5 mg/kg dry weight; east: 7.07 mg/kg dry weight) and Ni (west: 40.0 mg/kg dry weight; east: 20.2 mg/kg dry weight) than those other soft tissues. Byssus meanwhile recorded high levels of Zn (west: 173 mg/kg dry weight; east: 193 mg/kg dry weight) and Fe (west: 3213 mg/kg dry weight; east: 1221 mg/kg dry weight). By comparing the accumulation of heavy metal concentrations in all the eight tissues, CS and byssus recorded the highest accumulation of heavy metals among all tissues, followed by other tissues namely foot, gill, gonad, mantel, muscle and remainder, which recorded relatively low level on heavy metal concentrations. Generally, the soft tissues recorded higher heavy metal concentrations on the east coast than on the west coast of the SOJ. This indicated a high bioavailability and contamination of the potentially toxic heavy metals on the east coast which was due to various human activities.

Bioaccumulation of trace metals in Mediterranean mussels (Mytilus galloprovincialis) from a fish farm with copper-alloy mesh pens and potential risk assessment

ABSTRACTConcentrations of trace metals were determined in the muscle tissue, digestive gland and gills of Mediterranean mussels (Mytilus galloprovincialis) collected from different locations around an offshore copper alloy fish farm. Levels of copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) as mg/kg wet weight in the edible part of the mussels collected from distant zone (upstream Zn7.33 > Fe2.8 > Cu0.13 > Mn0.07 and downstream Zn9.9 > Fe5.67 > Cu0.18 > Mn0.17) were significantly lower (p < 0.05) than those sampled from the cage zone (bottom panel Zn22.25 > Fe13.75 > Cu2.39 > Mn0.85 and cage frame Zn17.1 > Fe8.74 > Cu1.39 > Mn0.26). Trace metal concentrations in mussels were significantly higher (p < 0.05) in the samples from the frame and bottom panel of the copper alloy mesh pen, compared to those from distant areas, namely the farm affected downstream -and non-affected upstream locations. However, the rates of target hazard quotients (THQ) for all tested trace metals from all locations in the present study were smaller than “one” (THQ < 1), indicating that the consumption of mussels grown around a cage farm with copper alloy mesh pens were within safe limits and did not exceed maximum levels suggested by the US Food and Drug Administration (USFDA) and European Union (EU) regulations for seafood consumption.

Blue mussels (Mytilus edulis) as bioindicators of stable water quality in Sydney Harbour during remediation of the Sydney Tar Ponds, Nova Scotia, Canada

Contaminants were measured in blue mussels (Mytilus edulis) in Sydney Harbour (SH) during remediation of the Sydney Tar Ponds (STPs) to assess the spatio-temporal distribution of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and metals during baseline and remediation. Overall distribution of chemicals in mussels was compared to contaminants in other marine indicators. Metal concentrations in mussels showed some minor temporal variability, but did not appear to be directly related to remediation activities. Contaminants showed stable or decreasing concentrations, except Pb and Zn. Individual PAH compounds were mostly undetected, except for fluoranthene and pyrene. Concentrations of fluoranthene in mussels and water were weakly related (R2 = 0.72). PCBs were undetected, except during year 2 remediation at some near-field stations. Contaminants measured during this study were much lower than previously reported in other studies of mussels in SH, likely due to ongoing natural recovery and because of environmental mitigation measures implemented during remediation activities at the STPs. The lack of detection of most individual PAHs, PCBs, and low bioaccumulation of metals during baseline and remediation using mussels as bioindicators reveal subtle improvements in environmental quality in SH.

Monitoring water quality in Sydney Harbour using blue mussels during remediation of the Sydney Tar Ponds, Nova Scotia, Canada

Using mussels as monitoring tools we measured water quality in Sydney Harbour during a large scale, multi-year remediation project of the Sydney Tar Ponds (STPs); one of Canada's most contaminated sites. Chemical contaminants were measured in blue mussels (Mytilus edulis) in Sydney Harbour, which were used as monitoring tools to assess the spatio-temporal distribution of polycyclic aromatic hydrocarbons (PAHs); polychlorinated biphenyls (PCBs); metals (As, Cd, Cu, Hg, Pb, Zn) and lipid content during baseline and 3years of remediation. The overall spatio-temporal distribution of chemicals in mussels was also compared to contaminants in other marine indicators (e.g., sediment, water and crab tissue). Measured metal concentrations in mussels showed some minor temporal variability (4years), but these did not appear to be directly related to remediation activities, with the highest concentrations of As, Hg and Zn measured at reference stations. Most measured contaminants showed stable or potentially decreasing concentrations during the study, except Pb and Zn. Individual PAH compounds were mostly undetected during baseline and remediation, except for fluoranthene and pyrene. Concentrations of fluoranthene in mussels and deep water samples were moderately related. Generally, PCBs were undetected (<0.05μgg(-1)), except during year 2 remediation at some near-field stations. Contaminants measured during this study were at much lower concentrations than previously reported in other studies of mussels in Sydney Harbour and eastern Canada. This is likely due to the ongoing natural recovery of Sydney Harbour and to a lesser extent because of the environmental mitigation protection measures implemented during remediation activities at the STPs. The lack of detection of most individual PAHs and PCBs, plus relatively low bio-accumulation of metals observed during baseline and remediation attest to the effectiveness of using mussels as monitoring tools for environmental quality.

Stable lead isotope ratios and metals in freshwater mussels from a uranium mining environment in Australia’s wet-dry tropics

Abstract Concentrations of Fe, Mn, Cu, Zn, U and Pb, and stable Pb isotopes 206Pb, 207Pb and 208Pb were measured via inductively coupled plasma mass spectrometry in sediments, water and freshwater mussels (Velesunio angasi) from two catchments in the Alligator Rivers Region, Australia. Sediment U and Pb concentrations were higher in Magela Creek downstream than upstream of the Ranger U mine due to the mineralised nature of the catchment and potential local input of sediment from the mine site. Water metal concentrations were highest in Georgetown Creek, which is a tributary of Magela Creek and part drains the Ranger mine site, but there was little difference in concentrations between the Magela Creek upstream and downstream sites. Metal concentrations in mussels collected immediately upstream and downstream of the mine site also showed little difference, whereas Pb isotope ratios displayed a very distinct pattern. The 206Pb/207Pb and 208Pb/207Pb isotope ratios were more uranogenic downstream than upstream of the site and also more uranogenic than ratios measured in Sandy Billabong, a reference billabong in a catchment not influenced by U mineralisation. Isotope ratios were also more uranogenic in younger mussels, potentially due to the increasing footprint of the mine site over the past decade. The most uranogenic ratios were found in mussels from Georgetown Creek and at a site approximately 2 km downstream. At Mudginberri Billabong, approximately 12 km downstream of the Ranger mine, the relative contribution of uranogenic Pb to the total Pb concentration in mussels was small and overwhelmed by the input of industrial Pb with a Broken Hill type Pb signature. Whereas metal uptake by and thus concentrations in mussel flesh are influenced by water chemistry, mussel condition and metabolic rates, Pb isotope ratios are independent of these factors and provide a powerful means of source apportionment of contaminants in mussels and waterways, in particular in an U mining environment.

Spatial and temporal distribution of heavy metal concentrations in mussels (Mytilus edulis) from the Baie des Chaleurs, New Brunswick, Canada

Previous studies on heavy metal contamination of the Baie des Chaleurs focus only on industrial centers and overlooked the ecosystem as a whole. To fill this gap, the objective of this study is to establish a baseline of the spatio-temporal distribution of heavy metals in mussels from the Baie des Chaleurs based on the ecosystem approach. Our results show, for the first time, a cadmium contamination in mussels across the south coast of the Baie des Chaleurs and not only in industrial centers. Our results also confirm previous studies showing heavy metal contamination of the Belledune area. This study demonstrates that the use of the ecosystemic approach is essential to obtain a comprehensive picture of environmental contamination in marine ecosystems.

Metal contamination in Portman Bay (Murcia, SE Spain) 15 years after the cessation of mining activities

To evaluate the state and temporal trends of the residual metal contamination caused by the dumping of mine tailings into Portman Bay (SE Spain) during the 20th century, concentrations of Hg, Cd, Pb, Cu, Zn, and As in wild mussels (Mytilus galloprovincialis) were studied over the period 1991–2005. The results show significant downward trends (P &lt; 0.05) in the concentrations of Hg, Cu, Pb, and Zn. Nevertheless, trace metal concentrations in mussels from Portman in 2005 were higher than the reference concentrations established for the coast of Murcia and the Spanish Mediterranean littoral, the only exceptions being Cu and As. Red mullets (Mullus barbatus) caught at Portman in 1990 and 2004 presented higher levels of Hg, Cd, and Pb, in comparison with other areas of the south and southeastern coast of Spain. The results indicate that Portman Bay is still one of the areas most heavily contaminated by Pb and Cd along the Mediterranean coast of Spain 15 years after the cessation of mining activities.

The influence of body size, condition index and tidal exposure on the variability in metal bioaccumulation in Mytilus edulis

Mussels are commonly used to monitor metal pollution despite high inter-individual variability in tissue concentrations. In this study, influences of body size, condition index and tidal height on concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were investigated. Body weight was inversely related to metal concentrations and for Cd, Mn, Pb and Zn the regression was affected by tidal height. Except for As, Fe and Mn metal concentrations were inversely related to physiological status though no differences between essential and non-essential metals were obvious. After correcting for body size, tidal height was related positively to As, Cd and Zn, negatively related to Cu, Fe and Mn while Co, Cr, Ni and Pb were independent of tidal height. The study recommends stringent measures during sampling for biomonitoring or metal concentrations at each location must be normalized to a common body size, CI and tidal height.

Heavy metals in mussels and associated sediments from the coastal sites along the Pearl River Delta, South China

The concentrations of cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), antimony (Sb) and tin (Sn) in mussel and sediment samples collected together from ten different geographical coastal sites of the Pearl River Delta of South China were determined. The mussels studied were ‘green-lipped mussels’ (Perna viridis). Sampling was carried out from 30 December 2002 to 2 February 2003 (winter season in South China). The results showed that the average concentrations of Cd, Cu, Zn, Pb, Ni, Cr, Sb and Sn in mussels were 0.45–3.19, 5.01–29.14, 46.5–86.6, 0.77–4.97, 5.39–12.05, 8.2–86.4, 0.09–0.76 and 4.08–37.98 μg g−1 dry weight basis; and 2.14–6.9, 5.58–297.5, 32.4–229, 3.76–18.95, 1.73–42.67, 1.93–72.87, 1.33–6.21 and 46.2–250.2 dry weight basis in sediments, respectively. The metal levels in these mussels varied among the samples from different sites; there were six out of ten sampling stations where the metal concentrations in mussels exceeded the criteria level for chromium in shellfish products: 1 μg g−1 wet weight. Good correlation was observed for Cd concentrations in sediments with those in mussels, and a strong correlation was also observed for Cu and Sn in mussels. According to the present results, considerable contamination of Cu, Zn, Cr and Ni in east estuarine zone was evident. Estuarine zone seemed to suffer from Cd, Cu, Ni and Sn contamination as judged by metal concentrations in the mussels and sediments. In west estuarine zone, contamination was mainly due to Cu, Cr and Ni.

A comparative assessment of heavy metal accumulation in soft parts and byssus of mussels from subarctic, temperate, subtropical and tropical marine environments

Existing data on metal concentrations in mussels from subarctic, temperate, subtropical and tropical waters were analyzed using multivariate statistics in order to assess regional variations in metal contamination. Potential errors were reduced by only analyzing data from surveys that employed the same protocols, analytical methodologies and analysts. Factor analysis demonstrated that mussels inhabiting extremely contaminated areas (e.g. from Japanese and Swedish metallurgy sources) could be separated from mussels from other contaminated areas, and that metals such as Cd, Pb, Cu and Zn could be used to identify heavily contaminated samples while Co, Fe, Cr and Ni concentrations were good markers for exposure to inputs from different industrial sources. Furthermore byssus, like soft tissue, selectively and sensitively reflects variations of certain metal concentrations in ambient waters and thus serves as a reliable biomonitor for these contaminants in a variety of coastal and estuarine areas.

Temporal and spatial trends in heavy metal concentrations in the marine mussel Mytilus edulis from the Western Scheldt estuary (The Netherlands)

Since the first North Sea Conference (1984, Bremen), all countries bordering the North Sea made commitments to reduce discharge of hazardous substances into the North Sea. From Belgium and The Netherlands, large reductions (upto 90) in heavy metal emissions from land-based sources have been reported between 1985 and 2000. Recently, some studies in the Western Scheldt estuary (WS) have shown that total metal concentration in the water, sediments and suspended particles have decreased compared to levels in the 70s. However, data on aquatic organisms is still very limited and it is therefore difficult to confirm whether the reductions in pollution input and generally improving water quality in the WS have a corresponding impact on the levels of heavy metals in aquatic organisms. The current study measured metal concentrations in the soft tissues of mussels, Mytilus edulis (known to be good indicators of environmental metal pollution) during the period 1996–2002. Spatial (salinity and pollution gradients), temporal and seasonal variations were also studied. Results showed a down-stream decreasing trend for the metals studied (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) during all sampling campaigns. There was also a significant seasonal effect on tissue metal concentrations, with a peak observed around spring in both WS and the nearby less polluted Eastern Scheldt (ES). On temporal trends, a clear drop of metals in mussels was observed in the early 80s coinciding with the start of the efforts to reduce chemical pollution input into the North Sea. Since those early reductions, metal concentrations in mussels generally remained unchanged upto mid 90s. However, in recent times metal concentration in mussels have increased significantly, for example Cd in 2002 was almost 10 times the values in 1983 and similar to levels seen during the peak in the 70s. Other metals also increased in the 90s also reaching levels seen in the 70s. As there is no indication of recent increase in metal input into the estuary, we suggest that increased metal concentrations observed in mussels in recent years especially in the upper estuary are most likely a result of changes in physical and chemical speciation and metal bioavailability. Such changes may be caused by changes in some water quality parameters in the estuary (i.e. increased dissolved oxygen, concentration of organic matter), resulting in conditions that favour releases of sediment-bound metals into the water column. The relationship between metal content and season showed very similar annual profiles in the polluted WS and less polluted ES. Thus, seasonal variations in metal concentrations appear to be largely controlled by biological processes, while total body burdens are dependent on environmental levels and bioavailability.

Metal concentrations in zebra mussels and sediments from embayments and riverine environments of eastern Lake Erie, southern Lake Ontario, and the Niagara River.

Concentrations of 14 metals were studied in the soft tissues of zebra mussels ( Dreissena polymorpha) and sediments from 16 Great Lakes embayments and riverine environments. Samples were collected in 1993 and 1994 during the early and late autumn period when the body mass of mussels is least affected by reproductive activities. There was a significant difference in geometric mean concentrations of all metals except Cu in mussels sampled from different sites, and there was a significant difference in the geometric mean concentrations of all metals but Cd, Mn, and Zn between years. The higher metal concentrations in mussels from this study were generally similar to those in mussels from contaminated European and U.S. locations, and those with lower concentrations were similar to those from uncontaminated European and U.S. locations. Geometric mean sediment concentrations of all metals differed significantly among sites. Sediment concentrations of metals from some sites were above EPA guidelines for moderately polluted harbor sediments. Sites where zebra mussels had higher concentrations of Al, Cr, and V tended to be the same sites as those where sediment concentrations of these metals were also higher. However, there was not a significant statistical relationship between concentrations of metals in zebra mussels and sediments, except for Mg.

Temporal variability of bioavailable Cd, Hg, Zn, Mn and Al in an upwelling regime

Monthly variability of Cd, Hg, Zn, Mn and Al concentrations in mussels ( Mytilus californianus) soft tissue and brown seaweed ( Macrocystis pyrifera) was studied at a pristine rocky shore off San Quintı́n Bay, Baja California, México. The results were related to climatic and hydrographic conditions and to the physiological state of the mussels (condition index) by correlation analysis and principal component analysis (PCA). A “normalization” to account for the variability induced by the physiological state of the mussel was performed. The PCA was performed in two ways to relate the environmental variables and the condition index to: (1) the metal concentrations in mussels, and (2) the “normalized” mussel concentrations. The association of the variability of Cd with the upwelling season was revealed in both PCAs. The temporal variability of this metal in mussels was highly correlated to that in seaweed, suggesting that the dissolved phase determined the variability of Cd in mussels. However, for Hg, Zn, Mn and Al the results from both PCAs were different. The first PCA showed the relationship of these metals to pluvial precipitation and to the condition index. The PCA for the normalized mussel concentrations showed that, after eliminating the effect of the condition index, only Al was related to pluvial precipitation. Manganese, and to a less degree Zn, were related to these metals in seaweed. Because zinc is an essential element in mussels, some regulation of their internal concentrations is likely. Mercury was not detected in seaweed, but because of its reactive nature, it is not expected that the dissolved fraction could be a significant pathway; therefore, it can be concluded that its temporal variability was determined by the variability in the condition index only.

Quality of Moroccan Atlantic coastal waters: water monitoring and mussel watching

The quality of Moroccan Atlantic coastal wasters was monitored from 1993 to 1997 by measuring hydrological parameters (dissolved oxygen, suspended particulate matter, phosphates, and nitrates), and using the mussel Mytilus galloprovincialis as a quantitative bioindicator of cadmium, copper, manganese, and zinc contamination. Mean concentrations of dissolved oxygen and suspended particulate matter were indicative of the effects of urban and industrial discharges of wastewater, particularly at Mohammedia, Casablanca, Mehdiya, Jorf Lasfar and Safi. Stations receiving urban wastewater showed high nitrate concentrations, especially at Mehdiya, Rabat, Mohammedia, Casablanca and El Jadida. Metal concentrations in mussels showed significant variations depending on the station and sampling period. Jorf Lasfar and Safi had the highest mean concentrations for cadmium (8 and 7 μg·g –1 dry weight respectively) and copper (74 and 25 μg·g –1 dry weight). The relation between cadmium concentrations in mussels, and phosphate concentrations in water suggests that the processing of phosphate ores at these two sites is responsible for contamination. Mussels in the Mohammedia–Casablanca sector had the highest zinc concentrations (338–379 μg·g –1 dry weight), followed by those collected at Jorf Lasfar (267 μg·g –1 dry weight), and Sidi Moussa and Safi (290–301 μg·g –1 dry weight). The distribution of manganese concentrations, which were maximal in estuaries (up to 19 μg·g –1 dry weight), was indicative of terrigenous inputs. Seasonal variations in mussel metal concentrations were characterised by winter minima, and apparently related to the physiological cycle of the animal. With the exception of cadmium-contaminated areas, the quality of mussels on the Moroccan Atlantic coast is good with respect to food safety standards.

Trace metals in mussels from mariculture zones, Hong Kong

In 1997, concentrations of cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and nickel (Ni) were analysed in green-lipped mussels ( Perna viridis) from three mariculture zones located in the north-east (Kat O), south (Lo Tik Wan) and to the west (Ma Wan) of Hong Kong. Spatial differences in the concentration of metals were found, chromium and copper were higher at Ma Wan and Lo Tik Wan compared to Kat O in the north-east. In contrast, the highest levels of lead (mean=4.37 μg/g dry wt) were recorded at Kat O. There were no differences in the level of nickel between the study sites. A comparison of the metal concentrations in mussels with the results of a previous study seven years before, in 1990, showed a twofold increase in the mean levels of cadmium for all three sites. However, levels of the other metals in 1997 were lower by 12–32% for chromium, 32–39% for copper and 24–25% for nickel. The greatest reductions were recorded for lead: Kat O (39%), Ma Wan (51%) and Lo Tik Wan (75%). This may be related to the introduction of lead-free petrol in 1991. Despite the apparent reduction in some heavy metal bioaccumulation between 1990 and 1997, from a public health risk perspective, the data suggest a continued need for monitoring of heavy metals in mussels from mariculture zones.

Mussels as bioindicators of trace metal pollution in the Danube Delta of Romania

Specimens of mussels species Anodonta anatina, Unio pictorum, U. tumidus and surfical sediment samples were collected in the summers of 1994 and 1995 from twelve lakes in the Danube Delta, Romania. Whole mussel tissues were analyzed for metals (Ag, As, Cd, Co, Cu, Cr, Ni, Pb, Se and Zn), and sediment samples were subjected to weak acid extraction and to a sequential extraction procedure, and analyzed for Cr, Cu, Ni and Zn. Total mean Cu and Ag concentrations were statistically greater in Unio species than in Anodonta species, but other metal levels did not significantly differ between mussel species. There was a ten fold variation for Cd and Pb and five fold variation for Zn, Ag and Co concentrations in mussels among lakes. Mean concentrations of As, Cu, Se and Zn in mussel tissues varied two fold among lakes. Zn, Co and Cd concentrations in mussels were significantly negatively correlated with distance gradients from the origin of the Delta and with distance from main channels of the Danube. Other metal concentrations in mussels did not correlate with either distance gradient. Trace metal levels in mussel tissues were correlated with those in weak acid and in sequential extractions of sediment. Zn concentrations in the carbonate fraction was the best predictor of Zn concentrations in mussels. Cu and Ni levels in the organic matter and sulfide fraction were the best estimators of Cu and Ni concentrations in mussels.

The Tomlinson Pollution Load Index applied to heavy metal, ‘Mussel-Watch’ data: a useful index to assess coastal pollution

The Tomlinson Pollution Load Index (PLI) is calculated as the chemical product concentrations that are measured in marine mussels. It can be used as an index of bioavailability of pollutants for mussels in coastal waters. For the computations, published data from ‘Mussel-Watch’ programs have been used. The PLI standardizes the data by using the quotients obtained by dividing each concentration by a baseline concentration for each chemical, that is, by the lowest concentration of each chemical found in mussels and listed in the literature. The results indicate that the PLI has a normal distribution with a marked positive asymmetry. The exceptional values that surpass a PLI of 100 correspond to very contaminated sites and require immediate intervention; a PLI > 50 requires a detailed survey. The PLI does not show any relationship with either the year when specimens were sampled or with mussel species but it does detect an annual cycle in metal concentrations in mussels. It is also observed that the number of measured metals influences the PLI, because the pollution of a site is usually due to the presence of a few pollutants in large concentrations. The PLI is proposed as a standardized system for detecting pollution which permits a comparison of pollution levels between different sites and at different times.

Heavy metal concentrations in mussels from the gulf of Olympias ‐ Chalkidiki, Greece

Abstract Concentrations of lead, cadmium, copper and zink in sixty six (66) samples of Mytillus galloprovincialis (mussel). The samples were obtained from the gulf of Olympias and Makriyalos Greece. The results indicate high concentrations of lead (mean values over 1 mg/kg) while the concentrations of other metals are at acceptable levels. It also seems that the concentrations of lead and cadmium are higher during Spring and lower in Summer and Autumn.

Seasonal variation of trace metal concentrations in the digestive gland of the Mediterranean mussel Mytilus galloprovincialis: Comparison between a polluted and a non-polluted site

Seasonal changes in metal (Cu, Fe, Mn, Pb, and Zn) concentrations were observed in the digestive gland of the Mediterranean mussel, Mytilus galloprovincialis, from both a polluted and a non-polluted population. Digestive gland of mussels from the polluted site showed metal concentrations appreciably higher than in non-polluted organisms, especially for Pb (up to 160 micrograms/g d.w.), Mn (up to 300 micrograms/g d.w.), and Fe (up to 8,500 micrograms/g d.w.), whereas the two populations showed maximum mean values, respectively, of 34 and 20 micrograms/g d.w. for Cu and 170 and 120 micrograms/g d.w. for Zn. Over 1 year (1991), differences between maximum and minimum values were moderate only in the unpolluted organisms. During gametogenesis, while the metal concentrations (expressed as microgram/g dry weight) decreased in the digestive gland, the tissue burden (as microgram) in that organ remained nearly constant or increased slightly. The apparent decrease in metal concentrations was probably due to the penetration of gonadic tissues into the digestive gland during gametogenesis, which biologically diluted metal concentrations in mussels from both the polluted and unpolluted populations. The effect of mussel size on trace metal concentrations in the digestive gland was demonstrated during different stages of the reproductive cycle. Higher concentrations were found in smaller organisms; however, during the spawning period, due to the fact that this is not a synchronous process within a population, the organisms exhibit a high variability in digestive gland weight which can mask this relationship when digestive gland weight is used as a size-index and as a parameter of the trace metal digestive gland burden.

Trace metal concentrations in mussels ( Mytilus edulis planulatus L.) transplanted into Southern Australian waters

Trace metal concentrations in mussels ( Mytilus edulis planulatus L.) transplanted into Southern Australian waters