Efeitos dos biocidas dcoit e diclofluanida para as microalgas Chaetoceros muelleri, Thalassiosira pseudonana, Chlorella minutissima e Dunaliella salina

Abstract

Biofouling is a phenomenon that can impair the maritime industry. Currently, a third generation of antifouling paints is widely used to prevent this phenomenon, applying various biocidal compounds as active ingredients. However, even tought the compounds having fast degradation, their presence in the environment can still pose risks to non-target and ecologically important organisms such as microalgae. The aim of this study was to evaluate the toxicity of the biocides DCOIT and dichlofluanid on different species of marine microalgae (Chaetoceros muelleri, Thalassiosira pseudonana, Chlorella minutissima and Dunaliella salina), analyzing growth, chlorophyll a content and cell viability. It was possible to observe that all microalgae were more sensitive to DCOIT than to dichlofluanid, and its effects were observed at level previously detected on the environment. Based on the EC50 (72 h) values, the order of sensitivity of microalgae to biocides was: C. muelleri > C. minutissima > T. pseudonana > D. salina, and all species proved to be efficient for use in chronic exposure tests to biocides. Chlorophyll a content and the algal growth proved to be effective tools for evaluating the effects, however, it was not possible to accurately assess the effects of biocides on the cell viability of microalgae. Based on our results, we observed that although third generation biocides are considered less harmful to ecosystems due to their fast degradation in the natural environment, the intensity of use of biocides in antifouling systems, especially DCOIT, can cause negative effects on the environment by affecting species of ecological importance to the marine phytoplankton.