A novel rapid assay for evaluating the efficacy of biocides to inhibit the development of marine photoautotrophic biofilms

Abstract

In this paper a novel settlement and growth assay is presented that uses field-collected marine photoautotrophic biofilms as inoculum. The multitude of indigenous species that are the potential foulers aretherefore included in the assay, which overcomes the limitation of testing only those species that can be cultivated in the laboratory. The assay was evaluated using eight antifouling biocides. The methodological considerations are discussed thoroughly and full concentration response curves are presented for all testedbiocides. The efficacy ranking based on EC 98 values from the most to the least efficacious compound is as follows: copper pyrithione > TPBP > DCOIT > tolylfluanid > zinc pyrithione > medetomidine > copper (Cu 2+ ). The algaecide irgarol did not cause a full inhibition of settlement and growth but the inhibition leveled out at 95% already at 30 nmol l -1 , at a concentration that is clearly lower than for any other of the tested biocides.