PARENT SESSION

(MOP/163) Application of a fluorescence variable for the detection of marine pollution in natural phytoplankton assemblages.

Pérez, Patricia¹, Estévez, Patricia¹, Fernández, Emilio ¹, Beiras, Ricardo¹, ¹ Universidade de Vigo, Vigo, Galicia, Spain

ABSTRACT- The toxic effect of pollutants is reflected on inhibition of photosynthesis and growth in microalgae. In this study we attempt to prove the usefulness of the fluorescence variable: potential photochemical efficiency of the open reaction centres of PSII (_po), as an indicator of the degree of chemical pollution in natural populations of microalgae. Preliminar experiments have already been done using cultures of two common microalgae: Isochrysis galbana and Skeletonema costatum. They were exposed to Copper concentrations of 0, 45, 90, 180g/L. The parameters daily assayed were cell density and _po. Both variables showed a significant inverse linear correlation with [Cu] (R²>0.82). As a general rule, higher values of _po appear to be related to greater photosynthetic efficiency. This correspondence is shown during the exponential growth of the cultures. _po measured in the control (0.530) and [Cu]=180g/L cultures (0.450) were significantly different (GLM Analysis of repeated measurements, Bonferroni test, p<0.05). Experiments with I. galbana cultured in sediment elutriates have also been done, comparing sediments from a clean area and from a well known polluted beach, according to our previous data. In this case, significant differences were found after only 1 hour-exposure, where _po got values of 0.226 and 0.151 respectively. Our current research is based on the measurement of _po by using the Fast Repetition Rate Fluorometer, which can measure _po at natural phytoplankton densities, and thus the effect of pollutants on natural microalgae assemblages. The development of this technique is potentially valuable as a rapid, non-destructive way of detecting toxicity on natural populations of microalgae under polluted conditions.

Key words: photochemical efficiency, pollutants, toxicity, microalgae