Water Quality and Phytoplankton Density in Alinsaog River, Zambales, Central Luzon, Philippines: Implications on Its Land Use

Abstract

The study aimed to assess the water quality and phytoplankton density of Alinsaog River in Zambales, Central Luzon, Philippines. Water quality on the four designated stations along the stretch of the river was evaluated based on physicochemical parameters such as temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), salinity, total dissolved solids (TDS), Secchi disk visibility, nitrate-nitrogen, phosphate, and chemical oxygen demand (COD); hydrologic properties like stream flow; and biological characteristics like phytoplankton density. The results were compared with the water quality standards for freshwater using the Department of Environment and Natural Resources Administrative Order 34, series 1990. The results showed that TDS and COD, and the DO concentration during the dry season exceeded the standard limit for Class C water. A high density of non-toxic red tide organism Peridinium sp. of up to 111,982 cells/L was recorded two months after storm-induced flooding caused by typhoon Koppu. This result was concurrent with the increased level of nitrate and phosphate in the upstream and downstream stations. There was a negative correlation between dinoflagellates density and EC, TDS, and salinity and between total phytoplankton density and EC. The results suggest that the water quality of Alinsaog River failed to meet the local regulatory standards in terms of DO, COD, and TDS. Some land-based activities were found to influence the health status of the river. These findings can be used as a basis for the formulation of river management plan including the policies and strategies for its protection and rehabilitation.

Keywords: Peridinium sp., typhoon Koppu, chemical oxygen demand, stream flow

JEL Classification: Q53, Q25