Bioanalytical Monitoring of Laguna Lake (Philippines) to Assess Water Research Priorities Associated with Organic Chemical Pollution and Cyanobacterial Blooms

Over several decades, anthropogenic influence has contributed to continuing water quality deterioration in Laguna Lake (Philippines), affecting the vital ecosystem services that it provides. To evaluate the potential ecotoxicological impacts of organic chemical pollution in the lake, a battery of in vitro bioassays (cytotoxicity, mutagenicity, and estrogenicity) was employed across 15 sites on Laguna Lake and a pond receiving secondary treated effluent that served as a positive control. Microcystin-LR concentrations were evaluated, given the historical occurrence of cyanobacterial blooms. Cytotoxicity (3.73 to 270 IC10-REF), mutagenicity (0.315 to 0.683 μg/L 4-NQO eq), and microcystin-LR (0.2 and 135 μg/L) were detected in lake samples suggesting potential toxicity risks. Cytotoxicity was correlated with microcystin-LR concentrations (r = 0.84) though at this stage, it is difficult to directly associate cytotoxicity with cyanoblooms due to other potentially co-occurring substances that were not analyzed. Estrogenicity was not detected in the lake, despite previous studies suggesting the presence of estrogens. Overall, results indicate a need for a long-term monitoring plan that considers cyanobloom presence and effects-based monitoring. To improve reporting on the environmental state and communication among stakeholders, a water quality index was established. The index suggests that current conventional monitoring parameters may not accurately predict water quality, particularly during cyanoblooms.