Validating the chronic Pb algae bioavailability model at high pH : single-species evaluation : final report, 12 June 2017

We investigated toxicity of Pb to Pseudokirchneriella subcapitata using the standard 72h-growth inhibition assays at 2 pH levels (pH 7.2 & pH 8.4) and 2 P (P 10 ug/L & P 100 ug/L) levels, i.e. at 4 treatments in total. This was done to test whether an existing algae Pb bioavailability model developed for pH≤8.0, can be used at higher pH>8.0. The algae Pb bioavailability model calibrated on Pb toxicity at pH 7.2 (P 100 µg/L) predicted filtered Pb toxicity(EC50 and EC20) at pH 8.4 (P 100 µg/L) with reasonable accuracy, i.e. within 2-fold error. Although the slope of the linear relationship between pH and log10(EC50 as Pb2+ acitivity) for the pH range between 7.2 and 8.4 (present study) was slightly lower than that of the pH range between 6 and 8 (existing model), our study suggests that the chronic algae Pb bioavailability model can be extrapolated to predict Pb toxicity up to pH 8.4

Antidepressants stimulate population growth in the harpacticoid copepod Nitocra spinipes

Like many pharmaceuticals, antidepressants are designed in such a way that they do not degrade easily. Due to their limited breakdown capabilities, they often enter sewage systems in their active form and may even end up in the environment. Significant concentrations of the commonly prescribed antidepressant citalopram have been measured in freshwater systems in the past. Moreover, recent experiments in our laboratory revealed effects on the life history of the harpacticoid copepod Nitocra spinipes caused by exposure to citalopram at concentrations of 100 ng/L and upward. It is, however, unclear how these effects on individuals propagate to the population level. In this study, freshly initialized populations of N. spinipes were exposed to citalopram hydrobromide at concentrations of 0 (control), 100, 1000 μg/L (18 populations per treatment). After 1, 3, 5, 6, 7, and 8 weeks, 3 replicate populations per treatment were permanently removed from the setup and preserved in 70% ethanol. All samples were first counted manually under a light microscope (excluding the larval stages which were too small) and subsequently photo-documented using a FlowCam. Manual counts showed no effects on the population abundance at 100 μg/L. At 1000 μg/L, population abundances were slightly reduced, at first, but strongly exceeded the control at weeks 7 and 8. This supposed stimulation effect may be attributed to an increased reproduction rate which had been observed earlier in individual females exposed to citalopram. At the time of abstract submission, the FlowCam pictures are still being processed. They are, however, expected to allow for a more thorough evaluation of the population dynamics, including high-resolution size-distributions of each sample, over time. The results of this study indicate no immediate threat of citalopram to N. spinipes at concentrations found in the environment (< 1 μg/L). However, they provide valuable insights into the form and timing of stressor-induced population-level effects on N. spinipes

Harpacticoid copepods in a DEB framework : investigating pharmaceutical effects on Nitocra spinipes

C

The initial tolerance to sub-lethal Cd exposure is the same among ten naïve pond populations of Daphnia magna, but their micro-evolutionary potential to develop resistance is very different

A

Chronic copper gBAM for fish : investigating possibilities and limitations of a generalised bioavailability model (gBAM) for predicting chronic copper toxicity to freshwater fish : final report

This study developed a fully parameterised de novo chronic Cu generalised bioavailability model (gBAM) for juvenile rainbow trout that incorporates toxicity modifying effects of pH, dissolved organic carbon (DOC), Ca, Mg, and Na. This gBAM genreally performs better than a previously developed biotic ligand model (BLM), notably with respect to a more accurate prediction of the effect of pH on chronic copper toxicity. The extrapolation of this model to early life stages of fish is encouraging. The gBAM developed in this study is the first model to integrate all available data on the chronic toxicity of copper to fish in a consistent way