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Notes: Abstract The net uptake of zinc by the common mussel Mytilus edulis (L.) has been investigated under different natural and artificial salinity stresses. The effects of stable and fluctuating salinities on the uptake of zinc by the mussel are discussed in terms of three possible modes of action. Under certain highly-stressful conditions, salinity may affect the uptake of zinc by the mussel. This factor should be considered when the mussel is used as an indicator of environmental pollution by zinc in estuarine areas, or spurious conclusions may result.

Notes: Abstract Concentrations of lead, iron and manganese in whole soft parts of mussels, Mytilus edulis (L.), collected from 54 locations in Scandinavian waters were determined. The indicator ability of the mussel for these metals was tested by considering local variations in concentrations of the three metals in relation to known industrial sources. A general agreement with previous published data was reached; the indicator ability of the mussel for lead and iron was supported over the entire range of salinity prevalent in the study area, whereas that for manganese appeared dubious, at least in low-salinity regions. Consideration of the overall profiles of metal contamination revealed similar trends to those previously reported for zinc and cadmium in mussels from the study area, at least for lead and iron. Thus, higher concentrations of lead and iron were found in mussels from low-salinity waters east of Sweden than in mussels from high-salinity waters west of Sweden. The decrease from the high-metal mussel samples to those with low metal concentrations was apparent in the areas of the Sound and Great Belt, coincident with the mixing of Baltic water with water of Kattegat/Skagerrak origin. Concentrations of manganese in mussels followed this trend only weakly, possibly due to the partial regulation of body loads of this element in M. edulis. The comparison of lead and iron concentrations in mussels with those reported for water suggested a greater biological availability of these metals in the low-salinity water masses east of Sweden. This availability difference may be related to the low primary productivity of these waters compared to the more typically marine waters to the west of Sweden. The comparison of the concentrations of lead and iron in mussels from the present study with those in mussels from other waters of the world showed Swedish coasts to be severely polluted by lead, particularly on the eastern seaboard; iron concentrations are also rather high in the Baltic samples, but decrease in the Sound and Great Belt to much lower levels, which are maintained in Kattegat and Skagerrak. The profiles for manganese reveal rather higher values in mussels from Scandinavian waters than in those from Britain or New Zealand; however, the uncertainty concerning the indicator ability of M. edulis for this element renders the implications of this obscure.

Notes: Abstract Mussels, Mytilus edulis L., were subjected to high temperatures, low salinities and dissolved zinc in order to investigate possible environmental hazards of a discharge of heated effluent near Newport on the Yarra River estuary, Victoria, Australia. Exposure to zinc at 0.8 mg l-1 for 14 d in otherwise favourable conditions significantly increased mortality resulting from subsequent exposure to temperatures between 29° to 31°C for 24 h without added zinc. Mussels collected from water of temporarily lowered salinity (8‰–16‰ S) showed significantly lower thermal resistance than controls collected from marine salinities (35‰ S). Mussels taken from a marine environment and exposed to 10‰ S died at a rate which increased with temperature. Mussels acclimated for 14 d to combinations of 10°, 16° and 22°C and 22‰ and 35‰ S, and subsequently exposed to increased zinc concentrations accumulated zinc to levels which were independent of temperature and salinity. The zinc was lethal more quickly at 22°C and 35‰ S than at the lower temperatures and salinities. The modes of toxic action of the salinity, zinc and temperature factors are discussed and it is argued that zinc which has been found accumulated in mussels near Newport could be reducing their resistance to raised temperatures and perhaps other stresses, probably as a result of effects on lysosomal functioning. The evidence suggests that the heated effluent will accelerate any toxic effects of zinc or low salinities which occur near Newport and so poses a hazard in winter as well as in summer.

Notes: Abstract Concentrations of zinc, cadmium, lead and copper were determined in whole soft parts of the common mussel Mytilus edulis (L.) sampled in Port Phillip Bay and Western Port Bay, both in Victoria, Australia. The mussels were sampled according to procedures suggested by previous studies in order to eliminate the effects of natural environmental variables. Results of the analytical studies were compared to data on the quantities of trace metals known to be discharged by industry into the catchments of each Bay. This allowed an evaluation of the indicator ability of the mussel without the need for multiple analyses of water samples. The results suggest that the mussel is capable of acting as an efficient time-integrated indicator of zinc, cadmium and lead over a wide variety of environmental conditions. Although additional variables may remain to be investigated, the mussel is recommended as an alternative to the analysis of water and sediments. With further development this organism may also be useful for monitoring industrial effluent characteristics at the discharge site, allowing rapid, reliable and inexpensive control of water quality. In contrast, the mussel is of doubtful use as an indicator of copper; other indicator types such as macroalgae may be better-suited to the study of this element.

Notes: Abstract The net uptake of zinc, cadmium, lead and copper by the common mussel Mytilus edulis (L.) exposed to different conditions was investigated with a view to using this species as an indicator of contamination of the marine environment by these metals. The variables studied were season, position of the mussel in the water column, water salinity, water temperature, and the simultaneous presence of all four metals. Each of these 5 variables affected the net uptake of some or all of the metals studied under some conditions. Seasonal variation in concentrations of zinc, cadmium and copper was found in samples collected at three separate locations. The relationship of seasonal variation to tissue weight and absorption route of the metals is discussed. Near to freshwater inputs of trace metals, the concentrations of zinc, cadmium and lead in mussels were found to vary according to the depth at which the mussels were collected; in summer when freshwater run-off is less, this effect was absent. Low salinities did not affect the net uptake of zinc by mussels, but increased the net uptake of cadmium and decreased that of lead. Low temperatures had no effect on the net uptake of zinc or lead; the net uptake of cadmium was unaffected by low temperatures at high salinities but was decreased by low temperatures at low salinities. The presence of the other metals had no effect on the individual net uptake of either zinc, cadmium or lead. A sampling programme was devised to eliminate the effects of these environmental variables and to allow the use of M. edulis as an indicator of zinc, cadmium and lead in marine and estuarine environments. In contrast to the other metals, the net uptake of copper by the mussel was extremely erratic, and was affected by salinity and temperature changes and by the presence of the other metals and changes in their relative concentrations. The effects of other metals on the net uptake of copper cannot be easily eliminated or allowed for; it is, therefore, suggested that the mussel should not be used as an indicator of copper in the marine environment.

Notes: Abstract An urgent need for a sub-tropical and tropical indicator organism for use in the biological monitoring of pollutants is recognised. To this end, preliminary studies have been undertaken to test the indicator ability of the rock oyster Saccostrea glomerata (=Crassostrea glomerata Gould) for monitoring the trace metals cadmium, copper, iron and zinc. A survey of these trace metals in rock oysters from 54 sites in Hong Kong waters revealed elevated levels of metals in several areas. Profiles of metal abundance in S. glomerata agreed substantially with the distribution of industrial and domestic discharges in Hong Kong, and also with patterns of contamination found in studies of the Pacific oyster Crassostrea gigas and of sediments. Application of POLYDIV statistical analysis to these data has aided their interpretation and confirmed the relationship between known areas of contamination and elevated metal levels in S. glomerata. This oyster, which exhibits an unusually great capacity to accumulate a range of elements from the ambient environment, thus appears to be a reliable indicator organism, and may be of great value in global monitoring studies.