Epilithic microalgal species discriminate low and high levels of dissolved phosphate in rivers of Northern Mindanao, Southern Philippines

Abstract

Environmental conditions influence communities of riverine epilithic microalgae. In order to test the hypothesis that certain species can discriminate high and low dissolved phosphate concentrations, epilithic microalgae were collected and dissolved orthophosphate concentration concurrently determined at 63 rivers of Northern Mindanao. Microalgae were identified to the lowest taxon, and density of each species was estimated following standard methods for epilithic microalgae. Dissolved phosphate varied significantly between rivers with 27% of the sites registering high levels which were primarily attributed to anthropogenic input. Constrained multivariate linear Redundancy Analysis (RDA) showed that phosphate significantly explained the variability of abundance for Gomphonema sp.1, Melosira varians, Navicula concentrica, Navicula sp.8, Navicula sp.9, Navicula sp.12, Navicula sp.15, and Oscillatoria sp.1. Discriminant analysis showed that Gomphonema sp.1 and Navicula sp.12, and Oscillatoria sp.1 can discriminate high and low phosphate concentrations, respectively. Hence, these species may be regarded as practical environmental indicators of levels of dissolved phosphate in tropical river systems. This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.