Assessment of the Sex Ratio Oscillations in Two Populations of Acartia clausi and Acartia tonsa and Responses to a Model Xenoestrogenic Compound

Supervisors: Fernando Villate, Maren Ortiz-Zarragoitia (UPV/EHU)
Pollution is a serious problem facing Estuaries. Such pollution can have detrimental effects on the marine and zooplanktonic communities in the estuaries. Our study is investigating the sex ratio oscillations in two calanoids population (Acartia clausi and Acartia tonsa) abundant in two estuaries in the Bay of Biscay. In addition, we investigated the effects of exposure to EE2 in the females of the two copepod species. Two approaches were used in the evaluation. Field approach was used to investigate the sex ratio of the population of the two calanoids and its correlation with environmental variables. While the experimental approach was used to check the sensitivity of the two calanoids towards a potent endocrine disruptor “Ethinylestradiol” in respect of the copepod survivability, fecundity and egg hatching success. Our field approach results showed no correlation between the environmental variables and the copepod sex ratio. However sex ratio seems to change throughout the year. Such result indicates that sex ratio did not change with the changing environmental pattern and pollution. On the other hand, our experimental approach results showed that both A.clausi and A.Tonsa were sensitive towards high doses of ethyinylestradiol (500 μg/L). Such dose affected both the calanoid’s survivability and fecundity. Egg hatching success of the two calanoids was not significantly affected by Ethinylestradiol. Additionally,LC50 for both calanoids were calculated. Compared to other studied organisms survivability towards the pollutant, both Acartia clausi and Acartia tonsa survivability are the most sensitive towards the pollutant, thus a suitable candidate to investigate the effect of the xenoestrogen. However, A. tonsa results are not that much reliable due to very few experimental trials on the specie.