Toxicity of Antifouling Paints on Three Microalgae Species: Growth, Biomarkers and Photosynthesis Efficiency.
Supervisor: Esther Blanco (UPV/EHU)
Marine biofouling is the settlement and growth of marine organisms such as algae, plants, and/or animals on artificial surfaces in contact with seawater. To prevent the settlement and growth of these communities, antifouling coatings are usually applied. Over the years, the use of biocide-based antifouling coatings (BC) has been standard practice, in the maritime industry, but it has raised environmental concerns due to their direct and indirect impact, potential toxicity to non-target organisms, and their persistence in the marine environment. Therefore, new commercially available green alternatives, such as foul-release coatings (FRCs), are being developed. This study tested the effects of two antifouling typologies on three microalgae species, by exposing the selected microalgae species to different concentrations of the paint lixiviates in laboratory conditions. PVC panels with a standardized surface were coated with BC and FR coatings, submerged in 1 L filtered and sterilized seawater and placed on a shaker for 24 hours. The solutions were used to expose cultures of three different phytoplankton species (Isochrysis galbana, Tetraselmis chui, and Cylindrotheca sp.) to different lixiviate concentrations, each of which had 3 replicates, following OECD guidelines with some minor modifications.

Exposure was carried out for 72 hours and growth was estimated every 24 hours. After 72 hours, samples from each culture were taken to measure 1) growth 2) oxidative stress biomarkers (CAT) and lipid peroxidation and 3) photosynthesis efficiency. Exposure to BC lixiviates significantly affected the growth of the three microalgae species. Out of the three species considered, Tetraselmis chui was the only phytoplankton species that grew and showed a better response after 72hours of exposure to the highest (25%) BC lixiviate concentration indicating more contaminant tolerance or resistant capacity. Selected biomarker analysis revealed that the species experienced substantial stress when exposed to the lixiviate concentrations of the biocide-based paint under consideration. Regarding photosynthesis efficiency, the fluorescence yield (Fv/Fm) particularly dropped for BC-exposed Cylindrotheca cultures. FR-exposed cultures performed without differences from the controls in all the examined microalgae species.

Keywords: Microalgae, Growth inhibition, Biofouling, Antifouling paints, Photosynthesis efficiency, Biomarkers, Lixiviate