Effects of intermittent exposure of marine pollutants on sugar kelp and periphyton

Pollution in the natural aquatic environment is erratic and manifests as temporary increments of chemical concentrations, pulses. Traditional ecotoxicological testing does not consider intermittent exposures and does not consider the post-exposure period even though latent effects may occur. Sugar kelp (Saccharina latissima, L.) was exposed to pulses of seven antifouling compounds with different mechanisms of action and marine periphyton were exposed to pulses of a photosystem-II inhibitor and a sterol synthesis inhibitor. Effects of pulsed exposure that did not appear until after the end of exposure were observed in both systems. The pollution history of periphyton communities was found to alter the effect of the exposure of both irgarol and clotrimazole but with dissimilar consequences. Even brief pulses of chemical pollution needs to be considered as latent effects may appear. Sequences of pulsed exposures are hypothesised to differ in toxicity depending on whether the ecological mechanisms of action of the toxicants are similar or dissimilar.