MEPS 286:1-12 (2005)  -  doi:10.3354/meps286001

ABSTRACT: Phytoplankton were exposed to 4 antifouling booster biocides (Sea-Nine 211^®, Irgarol 1051^®, diuron and zinc pyrithione) to investigate toxicological responses. Initially, single species/ single biocide exposure experiments revealed changes in pigment ratios under all biocide exposures for the prymnesiophyte Emiliania huxleyi, but not for the cyanophyte Synechococcus sp. Growth inhibition results following 72 h exposures indicated that Synechococcus sp. was more tolerant to zinc pyrithione (NOEC of 1.0 µg l^-1) and Sea-Nine 211^® (NOEC of 0.9 µg l^-1) than E. huxleyi (EC₅₀ of 0.54 and EC₅₀ of 0.35 µg l^-1, respectively). In contrast, Synechococcus sp. was more sensitive to diuron (EC₅₀ of 0.55 µg l^-1) than E. huxleyi (EC₅₀ of 2.26 µg l^-1), whereas exposure to Irgarol 1051^® similarly impacted both species (EC₅₀ of 0.16 and 0.25 µg l^-1, respectively). In addition, the impact on photosynthesis and on pigment chemotaxonomy was investigated through a laboratory exposure experiment using a natural phytoplankton community. Pigment signatures were measured by High Performance Liquid Chromatography (HPLC) and densities of size-classified phytoplankton groups were monitored using Analytical Flow Cytometry (AFC). Group-specific sensitivity of the natural phytoplankton community was detected through pigment composition after 72 h exposure to 5 µg l^-1 zinc pyrithione and 10 µg l^-1 Sea-Nine 211^®. Zeaxanthin increased proportionally, indicating a relative increase in Cyanophyceae. This result was corroborated using AFC. Primary production, estimated by ¹⁴C-HCO₃^- uptake, was compared to maximum quantum yield of Photosystem II (F_V/F_M), which was quantified by Fast Repetition Rate Fluorimetry (FRRF). The 2 techniques were in good agreement (R² = 0.89, p = 0.0001), both primary production and F_V/F_M being impaired by exposure to all biocides tested. These results are discussed in the context of the potential environmental impact of biocides on phytoplankton communities and the ecological implications of any modifications in species composition.

KEY WORDS: Marine phytoplankton · Antifouling booster biocides · Emiliania huxleyi · Synechococcus sp. · Analytical Flow Cytometry · Pigments · Fast Repetition Rate Fluorescence · ¹⁴C-HCO₃^- uptake