Effects of bisphenol A on different trophic levels in a lotic experimental ecosystem.

Bisphenol A (BPA) is commonly used by manufacturers and can be found in many aquatic ecosystems. Data relative to BPA ecotoxicity are only available for studies in laboratory conditions on macro-invertebrates and fish. There is thus a lack of information for other trophic levels such as macrophytes. Moreover, the impacts of BPA within an ecosystem context, i.e. with populations from different trophic levels studied at long term in environmental conditions, have never been assessed. We carried out a long-term lotic mesocosm study in 20 m long channels under three exposure concentrations of BPA (nominal concentrations of 0, 1, 10 and 100 µg/L) delivered continuously for 165 days. Three trophic levels were followed: macrophytes, macro-invertebrates (with a focus on Radix balthica) and fish (Gasterosteus aculeatus). Significant effects were shown at 100 µg/L BPA on the three trophic levels. BPA had a direct impact on macrophyte community structure, direct and indirect impacts on macro-invertebrates and on fish population structure. Gonad morphology of fish was affected at 1 and 10 µg/L of BPA, respectively for female and male sticklebacks. In addition to these ecotoxicity data, our results suggest that fish are good integrators of the responses of other communities (including macro-invertebrates and macrophytes) in mesocosm systems.

A non-invasive method based on head morphology to sex mature three-spined stickleback (Gasterosteus aculeatus L.) in rearing conditions.

A mathematical model to distinguish mature female and male three-spined sticklebacks Gasterosteus aculeatus L. 1758 is proposed. This method is based on sexual dimorphism in the head morphology. The discrimination was established on five distances of interest on the head, adjusted by the standard length of fish. The parameters were estimated based on a training set composed of 102 fish with an equilibrium sex ratio and validated on a test set composed of 69 fish. The model estimates the relationship between the percentage of fish that can be sexed with our model and the percentage of fish correctly sexed. For instance, to reach 1% of error in the sex determination, only 53% of the fish should be considered, whereas to reach 5% of error, 90% of the fish can be used. Compared to other available methods to sex G. aculeatus, the model is non invasive, not expensive, rapid, replicable, and can be calibrated outside of the breeding period.