Phytoplankton composition and some physico-chemical analyses of water in Laguna de Bay at Tunasan, Muntinlupa

Water samples were collected from Laguna de Bay once a month for a period of six months from each of the four stations at Tunasan, Muntinlupa and physico-chemical analyses were conducted.The physico-chemical parameters studied include temperature (C), salinity (0/00), pH, conductivity (umhos/cm), dissolved oxygen content (mg/l), nitrate, orthophosphate and silicate content (mg/l). The average monthly temperature ranged from 27.00 to 30.50 centigrade, conductivity ranged from 630.00 to 1095.00 umhos/cm, the pH throughout the sampling period was 7, salinity ranged from 0.20 to 0.60 0/00, dissolved oxygen concentrations ranged from 3.49 to 9.70 mg/l, nitrate levels ranged from 0.0.42 to 0.450 mg/l, orthophosphate levels ranged from 0.198 to 0.520 mg/l and silicate levels ranged from 25.57 to 45.17 mg/l.Phytoplankton were collected by passing 20 liters of water into an 80 u-mesh plankton net. The phytoplankton identified were found to belong to 3 divisions, 4 classes, 8 orders, 21 genera and 15 families. The species of phytoplankton identified were Pediastrum simplex, P. simplex var. duodenarium, P. boryayum, Oscillatoria limosa, O. granulata Oscillatoria sp., Anabaena spiroides, Ankistrodesmus falcatus, Chlorella vulgaris, Tetraedron tumidulum, Sorastrum spinolum, Chlorococcum humicola, Scenedesmus dimorphus, S. quadricauda, Actinastrum sp. Ulothrix sp., Palmella mucosa, Volvox aureus, Closterium acutum. C. acerosum var. elongatum, Lyngbya limnetica, L. nordgardhi Wille, Microcystis aeruginosa, Chroococcus limneticus, Characiopsis spinifer, Cladophora glomerata, Synedra ulna and Nitzschia actinastroides. Pediastrum simplex was found to persist throughout the sampling period. The green algae were the most number of phytoplankton species collected, followed by the blue green algae and the diatoms.Simple correlation was done using 0.05 level of significance between the phytoplankton count and the physico-chemical parameters. It was found that only silicate, nitrate and salinity levels could be significantly associated with the phytoplankton count.Identification of phytoplankton was done by using key illustrations of Umaly and Cuvin (1988), Presscott (1978), Pantastico (1977), and Shirota (1966)