Quantitative multi-species toxicity assessment by analysis of freshwater stream periphyton pigments and lipids

Periphyton that colonizes unglazed ceramic tiles provides an easily obtainable, multi-species community that can be used to monitor toxic insults in stream environments. Changes in taxonomic composition, biomass and physiological status are readily determined by chromatographic techniques through the analysis of pigments, phospholipid ester-linked fatty acids (PLFAs), and lipid classes from a single solvent extraction. Tiles were sampled 2, 5, 7, 14, and 28 days following their transfer from reference to impacted sites in three different streams. Eight major pigments and one pigment degradation product were identified by high performance liquid chromatography (HPLC). An incremental sum of squares dendrogram of pigments and PLFAs correctly clustered samples with respect to the stream and differentiated between reference and impacted sites in each stream. Differentiation was due primarily to shifts in species composition, as evidenced by changes in the percentages of pigments and PLFAs common to algal types. In outdoor artificial streams, periphyton biomass decreased significantly, as determined by measurements of chlorophyll a, PLFAs, and total lipids, following 5 d of exposure to chlorine (100 µg L^-1 as total residual chlorine). Diatom populations decreased in the chlorine-impacted streams, as evidenced by decreases in the percentages of fucoxanthin, a pigment biomarker, and eicosapentaenoic acid (20:5w3), a fatty acid biomarker. This study showed that pigment analysis is a more cost-effective technique than lipid analysis for a rapid, quantitative assessment of the effect of pollutants on periphyton.