Abundance and distribution of the green alga Botryococcus braunii Kützing (1849) in Paoay Lake, Ilocos Norte

Abstract

Botryococcus braunii, a green colonial freshwater microalga that is currently found in Paoay Lake, Ilocos Norte, is recognized as a renewable source of energy. The monthly abundance and distribution of B. braunii in the lake in relation to the different physico-chemical parameters and other phytoplankton species were done from April 2009 to March 2010. Throughout the period of study, analysis of samples showed that B. braunii populations were present in all samples collected in the four sampling sites. Changes in cell density were noticeable, especially during the months of April and August. The highest recorded mean density was in August (2515 cells /mL) while the lowest mean density was in May (83 cells/mL). There were 38 genera of phytoplankton that co-existed with B. braunii in the lake. Physico-chemical parameters and nutrients were still within the range for growth of the alga. Fluctuations of these nutrients may be caused by seasonal variation and the occurrence of typhoons in the region. Growth of B. braunii population is positively correlated with temperature, conductivity and phytoplankton count while it is negatively correlated with DO, pH, transparency depth, NO₃-, and PO₄³. Although B. braunii populations were present within the water column throughout the sampling period, the present environmental conditions did not allow the formation of blooms of this algal species.