Results of an international interlaboratory study on dioxin-like activities in drinking-, river surface- and wastewater using DR CALUX bioassay.

Aquatic animals and consumers of aquatic animals are exposed to increasingly complex mixtures of known and as-yet-unknown chemicals with dioxin-like toxicities in the water cycle. Effect- and cell-based bioanalysis can cover known and yet unknown dioxin and dioxin-like compounds as well as complex mixtures thereof but need to be standardized and integrated into international guidelines for environmental testing. In an international laboratory testing (ILT) following ISO/CD 24295 as standard procedure for rat cell-based DR CALUX un-spiked and spiked extracts of drinking-, surface-, and wastewater were validated to generate precision data for the development of the full ISO-standard.

Ecophysiological strategies for growth under varying light and organic carbon supply in two species of green microalgae differing in their motility.

Mixing events in stratified lakes result in microalgae being exposed to varying conditions in light and organic carbon concentrations. Stratified lakes consist of an upper illuminated strata and a lower, darker strata where organic carbon accumulates. Therefore, in this contribution we explore the importance of dissolved organic carbon for growth under various light intensities by measuring some ecophysiological adaptations in two green microalgae.

Daphnia's dilemma: adjustment of carbon budgets in the face of food and cholesterol limitation.

We studied the carbon (C) metabolism in Daphnia when the amount of C (food quantity) and/or the content of biochemical nutrients (food quality) was limiting. Growth performances and C budgets of Daphnia magna (assimilation, faeces egestion, excretion and respiration measured by [(14)C]-tracing) were analysed when animals were raised on different food quantities and concentrations of cholesterol, an essential biochemical food compound. Cholesterol is of special interest because it not only acts as limiting nutrient but also contributes to the overall C pool of the animals.