Flow cytometry and pigment analyses as tools to investigate the toxicity of herbicides to natural phytoplankton communities.

Characterisation of natural phytoplanktonic communities is currently being advanced through flow cytometry and high resolution pigment analyses. To date, toxicological methods to assess impacts of herbicides on natural phytoplankton populations are lacking. Here, we report the novel use of these techniques in combination to study changes in phytoplankton populations exposed to 2-methylthio-4-tertiary-butylamino-6-cyclopropylamino-s-triazine (Irgarol 1051), a herbicide used in antifouling paints. Flow cytometry results revealed that following a 72-h exposure to approximately 100 ngL(-1), eukaryote abundance was less than half that in the controls. High performance liquid chromatographic analyses of pigments demonstrated that 19'-hexanoyloxyfucoxanthin was selectively lost relative to the control. This carotenoid is specific to the prymnesiophytes which are key constituents of phytoplanktonic communities within temperate marine waters. Values of EC(50) (72 h) as low as 70 ngL(-1) were calculated from the selective reduction in this compound. Concentrations substantially exceeding this level have been reported in UK and other European coastal waters.

Antifouling paint booster biocides in the UK coastal environment and potential risks of biological effects.

In the yachting sector of the UK antifouling market, organic biocides are commonly added to antifouling preparations to boost performance. Few data presently exist for concentrations of these compounds in UK waters. In this study the concentrations of tributyltin (TBT) and eight booster biocides were measured before and during the 1998 yachting season. The Crouch Estuary, Essex, Sutton Harbour, Plymouth and Southampton Water were chosen as representative study sites for comparison with previous surveys of TBT concentrations. Diuron and Irgarol 1051 were the only organic booster biocides found at concentrations above the limits of detection. Diuron was measured at the highest concentrations, whilst detectable concentrations of both Irgarol 1051 and diuron were determined in areas of high yachting activity (e.g. mooring areas and marinas). Maximum measured values were 1,421 and 6,740 ng/l, respectively. Lower concentrations of both compounds were found in open estuarine areas, although non-antifouling contributions of diuron may contribute to the overall inputs to estuarine systems. TBT was found to be below or near the environmental quality standard (EQS) of 2 ng/l for all samples collected from estuarine areas frequented by pleasure craft alone, but with much higher concentrations measured in some marinas, harbours and in areas frequented by large commercial vessels. Using the limited published environmental fate and toxicity data available for antifouling booster biocides, a comparative assessment to evaluate the risk posed by these compounds to the aquatic environment is described. TBT still exceeds risk quotients by the greatest margins, but widespread effects due to Irgarol 1051 and less so diuron cannot be ruled out (particularly if use patterns change) and more information is required to provide a robust risk assessment.