In the late 1980s, a number of countries restricted the use of tri-n-butyltin (TBT) as an active ingredient in antifouling paint for small boats, including pleasure craft, Irgarol 1051-2-(tert-butylamino)-4-(cyclopropylamino)-6-(methylthio)-1,3,5-triazine, belonging to the s-triazine group of herbicides-is now used in combination with copper in several antifouling products, Irgarol 1051 contamination of the marine environment was studied close to a marina on the west coast of Sweden, Highest concentrations (1.6 nM, 0.4 mu g l(-1)) were observed during the peak of the boating season, To investigate the potential for toxic effects, marine periphyton communities were established on artificial substrata in 22-litre flow-through aquaria and exposed to Irgarol 1051 during a 3-week period in April 1994, The algicide was continuously added at concentrations ranging from 0.06 to 260 nM, Irgarol 1051 was found to significantly (p<0.05) inhibit periphyton photosynthetic activity at 3.2 nM in short-term (hour) tests, Long-term (weeks) exposure produced effects at even lower concentrations, A significant change in community structure was found at 1 nM, which produced a shift towards tolerant species, Photosynthetic activity and algal biomass (chlorophyll a content) was significantly lowered at concentrations of 1 and 4 nM, respectively, indicating only minor functional redundancy in the communities, The most sensitive long-term effects were detected at 0.25-1 nM (0.063-0.25 mu g l(-1)) of Irgarol 1051, which is within the concentration range detected in the contaminated areas around the marina, It can be concluded that the present use of Irgarol 1051 is likely to damage microalgal communities in contaminated coastal waters. Copyright (C) 1996 Elsevier Science Ltd
