Seasonal variation in mineralization rates (C-N-P-Si) of mussel Mytilus edulis biodeposits.

To determine seasonal variability in mineralization dynamics of mussel biodeposits, we applied a multiple-element approach measuring mineralization rates of carbon (C), nitrogen (N), phosphorus (P) and silicate (Si) during three periods (March, August and November). The results of this study showed that mineralization rates vary between seasons and between elements and that mineralization dynamics were influenced by both temperature and biodeposit nutrient composition. Mineralization rates were 3.2 ± 0.4 mmol C, 0.17 ± 0.04 mmol N, 0.06 ± 0.02 mmol P and 3.91 ± 3.75 mmol Si per gram biodeposit (DW) per day, which represented 24 % of the particulate organic C and 17 % of the particulate organic N in mussel biodeposits. Seasonal variability was largest for Si mineralization with 60-80-fold higher rates measured in March compared to August and November. This difference is most likely related to the difference in biodeposit nutrient composition. It was furthermore shown that the labile fraction of biodeposits became mineralized after, respectively, 18, 9 and 13 days during the experimental periods in March, August and November. This indicates that temperature enhances biodeposit decomposition with approximately 2-3 times faster turnover at a 10 °C temperature interval (Q10 ).

A field study on stress indices in the sea mussel, Mytilus edulis: application of the "stress approach" in biomonitoring.

Sea mussels, Mytilus edulis, collected from a relatively unpolluted area of the Eastern Scheldt, were transplanted along contaminated sites of the Western Scheldt for 2 1/2 and 5 months. Several established stress indices were determined such as accumulation of pollutants, adenylate energy charge (AEC), and condition index. Following field exposure, mussels were also subjected to an additional lethal or sublethal stress. The data show that environmental exposure alters the mussel's response to stress, viz., aerial exposure and increased temperature, at the organismal (anoxic survival time), biochemical (AEC), and molecular (heat shock protein synthesis) level. The "stress approach" to assessment of environmental contamination appears to be a promising method to disclose early changes in the organism at a stage when conventional parameters (condition index, AEC) remain still unchanged.

Response to stress of mussels (Mytilus edulis) exposed in Dutch tidal waters.

1. Mussels were exposed in the Dutch coastal zone and the Western Scheldt estuary. After six weeks of exposure, trace metals, PCBs and PAHs were measured in the soft tissue. 2. Tissue concentrations of contaminants are high in the Western Scheldt and intermediate near the Rhine outflow, except for the lower PCB congeners. 3. Results show that the survival in air is significantly lower at higher tissue concentrations, in particular of the lower PCB congeners. 4. The clearance rate is reduced at the highest tissue concentrations.