Environmental Quality of Lake Mainit as a Habitat of Indigenous Goby, Glossogobius giuris (Hamilton, 1882) in Northeastern Mindanao, Philippinese

Abstract

Changes in environmental quality of Lake Mainit could adversely affect the inhabiting organisms like the indigenous goby, Glossogobius giuris or pijanga. Hence, a thorough 16-month (i.e. December 2016 to March 2018) water quality study was undertaken, specifically on obtaining data for water temperature (OC), Dissolved Oxygen (ppm), pH, nitrate (NO3-N, ppm), ammonia (NH3-N, ppm), nitrite (NO2-N, ppm), phosphate (PO4-N, ppm) and light intensity (Lum/ft2) at the seven (7) established sampling stations within the Lake. Standard collection of water samples and their physico-chemical analyses were done and results were compared to DENR standards for freshwater water bodies. Results showed that the water quality of the Lake were still within the desirable range for Class A and Class C waters. This answered the underlying occurrence of fish kills to other factors and not on water quality changes. Highlight of this study is the notable increase of 0.9oC for surface and vertical temperatures of Lake Mainit over a decade and would show a glaring impact of global warming. Based on the 16 months monitoring, turnover occurred once in the Lake, particularly during northeast monsoon, indicating that Lake Mainit is a “monomictic Lake.”