Water quality assessment of the Seven Lakes of San Pablo City, Laguna using the Zebrafish (Danio rerio) embryo toxicity test

Abstract

The Seven Crater Lakes of San Pablo City, Laguna are comprised of Lakes Bunot, Calibato, Mohicap, Palakpakin, Pandin, Sampaloc and Yambo. These lakes serve a variety of ecosystem functions but have been recently subjected to varying levels of anthropogenic stress. As such, the Zebrafish Embryo Toxicity (ZFET) Test was utilized in this study to determine the potential embryotoxicity and teratogenicity of the lakes. Embryo responses were compared with varying dilutions of Estero de Paco (EDP). Physicochemical analysis revealed that the lakes pass most of the set standards for Class C waters. However, some lakes exceeded the set limits for total nitrogen, total phosphorus, iron and lead. All lakewater samples had low mortality rates and did not manifest any sublethal endpoints. Average head and tail lengths were also statistically insignificant between all lakes. However, the total body length of embryos exposed to Sampaloc lakewater was significantly different from the negative control. This may be attributed to higher levels of pollution in the lake due to its large size and location within the city proper. Given these results, it was determined that the seven lakes do not pose any apparent threat on zebrafish embryo development. This information could act in conjunction with previous water quality reports for a better evaluation of the lakes and for implementing better strategies for the lake management.