A NOVEL IN-SITU BIOMONITOR USING ALGINATE IMMOBILIZED ALGAE (SCENEDESMUS-SUBSPICATUS) FOR THE ASSESSMENT OF EUTROPHICATION IN FLOWING SURFACE WATERS

A technique has been developed using alginate-immobilised algae that i s suitable for in-situ biomonitoring of flowing waters. This approach Hill facilitate the site-specific assessment of eutrophication in runn ing waters and the prediction of ecosystem response to altered nutrien t inputs. Effects of the cell immobilisation process were assessed and it was demonstrated that entrapment increased the rate of response to , and growth in, increased nutrient supply compared to free cells, alt hough this effect was not significant at environmentally relevant nutr ient concentrations. Significant differences in growth were detected w hen nutrients were supplied at a constant concentration but at differe nt flow rates (0.5, 16 and 230 cm(3) min(-1)). Growth was determined a s the rate of change in algal biomass measured using a non-destructive , automated scan of the absorbance (650 nm) across thin (similar to 0. 75-1 mm) nylon-supported films of immobilised algal cells. This novel technique was compared with the established methodologies of chlorophy ll-ic extraction and cell enumeration as measurements of algal biomass . All three methods showed that algal growth was inversely related to how rate of growth medium over the immobilised cells. These results de monstrate the value of this technique as a tough, durable and sensitiv e method for the continuous, or ''on-line'', water monitoring of algal growth potential in running waters. (C) 1997 Elsevier Science Ltd.