Taxonomy and ecology of phytoplankton in Balayan Bay, and its tributaries, Batangas Province, Philippines

Balayan Bay is considered as one of the most productive fishing grounds in the Philippines. Hence, taxonomic and ecological studies of the phytoplankton of the bay were conducted for one year from February 2006 to January 2007. The study was conducted in the four stations of Balayan Bay: Station 1 (Anilao), Station 2 (San Luis), Station 5 (Balayan), Station 6 (Calatagan) and two freshwater tributaries: Station 3 (Pansipit) and Station 4 (Palanas). A total of 97 taxa belonging to four divisions (Chlorophyta, Bacillariophyta, Pyrrhophyta, Cyanophyta), 34 families and 50 genera were identified. Of the 83 species belonging to division Bacillariophyta, four were identified as new records for the Philippines, i.e., Triceratium antedeluvianum Ehrenberg, Trigonium cf. margaritiferum, Cleve, Trigonium pileatum Grun, Trigonium frauenfeldii var. Latum Grev. One taxon has been evaluated and described as a new species: Trigonium gossianum Evangelista, sp. nov. This study also proved that diatoms dominate in terms of density and frequency of occurrence. The centric diatom, Cyclotella meneghiniana Kutz, recorded the highest average annual density in Station 2 (San Luis), 2600 units/ml and Station 6 (Calatagan) 2100 units/ml while the pennate diatom, Pinnularia ambigua Cleve, recorded the highest average annual density (2600 units/ml) in Station 3 (Pansipit). The highest number of phytoplankton collected was in Station 2 (San Luis) with a total of 4600 2600 units/ml, followed by Station 5 [Balayan (4500 units/ml)] and Station 1 [Anilao (4400 units/ml)]. Station 3 (Pansipit) had the least number of phytoplankton at 1200 units/ml. The density of phytoplankton found in Station 2 (San Luis) and Station 5 (Balayan) could be attributed to their approximate similarity in their salinity, pH, nitrates, phosphates, turbidity and total dissolved solids. Among the six stations, Station 5 (Balayan) had the highest species diversity index (H= 1,402) followed by Station 1 [Anilao (=1.35)] and Station 2 [San Luis (H=1.35)]. Of the 11 abiotic parameters examined, temperature had a significant negative correlation with the density of Pinnularia ambigua in Station 1 [Anilao (-0.796)] but a positive correlation between temperature and density of Cyclotella meneghiniana in Station 4 [Palanas (+0.614)]. Rainfall has also influenced the density of Pinnularia ambigua in Station 3 [Pansipit (+0.598)]. On the other hand, pH had significant correlation on the occurrence of the diatom, Podosira cf. montagnei in Station 4 (Palanas) (0.588)] and on the occurrence of Navicula sp. 1(0.642) and Oscillatoria subbrevis (0.639) in Station 5 (Balayan). There were three algal species that were usually present during the entire collection period: Cylotella meneghiniana, Coscindiscus radiatus and Nitzxchia sp.1. All of these species belong to division Bacillariophyta. The presence of these three species indicates that they have a wide range of tolerance for salinity, temperature and rainfall.