Whole sediment toxicity tests for metal risk assessments: on the importance of equilibration and test design to increase ecological relevance.

Current laboratory-based approaches for predicting metal toxicity in sediments exhibit a number of limitations. The most important are (1) a lack of sufficient equilibration resulting in unrealistically low pH values or unnaturally high porewater metal concentrations and (2) an inadequate test design regarding the metal concentrations selected for spiking. The present study illustrates that by explicitly accounting for these limitations, one obtains reliable and environmentally realistic toxicity data, thus advancing the metal risk assessments of sediments.

Single versus combined exposure of Hyalella azteca to zinc contaminated sediment and food.

The amphipod Hyalella azteca was exposed for 28 d to different combinations of Zn contaminated sediment and food. Sediment exposure (+clean food) resulted in increased Zn body burdens, increased mortality and decreased body mass when the molar concentrations of simultaneously extracted Zn were greater than the molar concentration of Acid Volatile Sulfide (SEM(Zn)-AVS>0), suggesting that dissolved Zn was a dominant route of exposure. No adverse effect was noted in the food exposure (+clean sediment), suggesting selective feeding or regulation.

The micro-evolutionary potential of Daphnia magna population exposed to temperature and cadmium stress.

This study examines micro-evolutionary aspects of a natural Daphnia magna population exposed to Cd. To this end, a set of hypotheses related to micro-evolutionary responses and to how these are influenced by temperature and Cd stress, were tested. Life-table experiments were conducted with 14 D.

Combined cadmium and temperature acclimation in Daphnia magna: physiological and sub-cellular effects.

Effects of temperature and Cd acclimation (>or=6 generations) on life history and tolerance responses to stress in three clones of Daphnia magna was examined using a 2x2 design (20 and 24 degrees C, 0 and 5 microg L(-1) Cd). Endpoints include acute Cd and heat tolerance, individual traits such as ingestion rates, growth and reproduction responses and physiological attributes such as acute Cd and heat tolerance, energy reserves, electron transport system activity, haemoglobin and oxidative stress enzymes. Cd (20 degrees C+Cd) did reduce reproduction, but acclimation to 24 degrees C+Cd did not decrease reproductive output additionally.

Integration of molecular with higher-level effects of dietary zinc exposure in Daphnia magna.

We exposed Daphnia magna for 21 days to dietary Zn, incorporated in a diet of the green alga Pseudokirchneriella subcapitata at 720 microg Zn/g dry wt and compared its response to D. magna fed with a control diet (116 microg Zn/g dry wt). Exposure to dietary Zn resulted in an increased body burden of D.