A Comparison of the Pythoplankton community structure and productivity between aquaculture and non-aquaculture areas in Taal Lake, Philippines.

Abstract

Taal Lake, with its growing agricultural investments, is being threatened with unsustainable development and poor management of its aquatic resources. To describe and compare the effects of aquaculture in the lake, the study correlated the physico-chemical parameters such as pH, temperature, total nitrogen (TN) and total phosphate (TP) content, ammonium nitrogen (NH-N), dissolved oxygen (DO) content, total dissolved solids (TDS), total soluble solids (TSS) heavy metals (cadmium, copper, lead, zinc) with the biological parameters using phytoplankton community structure and productivity. The physico-chemical parameters were analyzed for nonaquaculture site represented by Gonzales described to be having no fish pens and fish culture activities in the area and nearby proximity. The aquaculture sites were represented by Balakilong and Banaga described as having more than 1000 fish cages and aquaculture activities. Phytoplankton community structure was used to show dominance, evenness and pollution index. Chlorophyll a was used to measure productivity. The high nutrient input favored the increased frequency of the Dinophycean Ceratium furcoides and Staurastrum sp., Synedra ulna, Chlorophycean Staurastrum sp., Protoococcus sp., Closterium acutum, and Pediastrum duples. There was higher productivity in the aquaculture sites than in the non-aquaculture site. The class distribution and productivity was correlated to nutrient present in the sites. Banaga (aquaculture site) had high organic pollution, high organic matter, 1.05% and organic carbon, 0.61%. This could have resulted to higher productivity and shift s in class distribution. Palmer’s Algal Pollution Index was used to determine the degree of organic pollution in the three areas in Taal Lake, and Banaga had a total index score of 24, indicating high organic pollution. Nygaard’s Trophic Index was used to determine the trophic status of the lake based on the indicators phytoplankton species found in the three areas in the Lake; and all sites were found to be eutrophic. This would suggest that eutrophication could be taking place on the aquaculture sites.