Diversity of periphytic ciliates on vessel surface and effects of antifouling paint from the surface

Abstract

Periphyton on vessel surface has a potential risk on endemic ecosystems through moving habitats on transportation routes. As ciliates can live on various natural and artificial substrates, they were targeted to investigate vessel biofouling organisms in this study. To know diversity of periphytic ciliates, biofilms were sampled from the surface of five vessels, and then ciliate species in the samples were identified by molecular analyses as well as microscopic observations of living and silverimpregnated cells. To monitor effects of antifouling biocidal agents painted on the vessel surface, non-treated and antifouling coated (Intersmooth 7475 Si) plates were deployed in a nearshore water for 7 weeks, and then ciliate species succession on the plates was weekly tracked. A periphytic ciliate species, Diophrys appendiculata, was isolated from the plates and cultured to be established as a toxicity test species for antifouling biocide Sea-Nine 211. Fourteen species of periphytic ciliates were found from the samples of vessel surface. Ciliate fauna was different on the non-treated and antifouling coated plates for earlier 4 weeks. Aspidisca leptaspis and D. appendiculata were attached on the non-treated plates while Euplotes balteatus on the paint treated plates. D. appendiculata exhibited toxic responses to Sea-nine 211 as follows; very low mortality at 1-250 ppb concentration range, encystment of ciliate cells at 500-1000 ppb range, and 100% mortality within 5 minutes at 10,000 ppb. Future studies need to address in detail survival and invasive strategies of periphytic ciliates on vessel surface.