Phytoplankton composition and diversity in response to abiotic factors in Lake Buhi, Camarines Sur, Philippines

Phytoplankton were collected from eight sampling stations around Lake Buhi (Camarines Sur, Philippines) in September and November 2013. The eight sites represented varied zonation and resource uses. A total of 29 species were identified belonging to five major taxonomic groups: the diatoms (Heterokontophyta), green algae (Chlorophyta), cyanobacteria (Cyanophyta), eustigmatophytes (Heterokontophyta) and dinoflagellates (Dinophyta). Diatoms were the most abundant group (50%), followed by the green algae (41%). Sampling station with high concentration of fish pens generated high diversity (Shannon-Wiener diversity index 2.65) with dominance of pollution tolerant taxa, while the site near the outlet of the lake has the highest phytoplankton abundance (0.139 cells/ml). Results revealed significant differences in relative abundance of phytoplankton among sampling sites and between sampling months within each site. These differences were attributed to the variation in physico-chemical parameters among the sites. Canonical Correspondence Analysis (CCA) showed that nitrate, depth and turbidity positively influenced phytoplankton abundance. Variation in the abiotic factors, including resource use, affected spatial and temporal distribution of the phytoplankton community. Remediation measures on the lake must be directed towards the primary sources of these variations.