Effects of Salinity and pH on the Growth of Blue-Green Algae, Oscillatoria sp. and Microcystis sp., Isolated from Pacific White Shrimp (Litopenaeus vannamei) Ponds

Abstract

Experiments were carried out to determine the effects of salinity and pH on the growth of Oscillatoria sp. and Microcystis sp. under laboratory conditions. Oscillatoria sp. and Microcystis sp. were isolated from Pacific white shrimp (Litopenaeus vannamei) low-salinity culture ponds. Mono-clonal culture of each species was kept in 250-ml BG 11 media in the laboratory for 10 days. For Oscillatoria sp. salinities of 0, 5, 10, 15, 20, 25 and 30 ppt were maintained throughout the experimental period, while for Microcystis sp. salinities of 0, 3, 6, 12, 15 and 18 ppt were maintained. The water pH was maintained at 3.0, 4.5, 6.0, 7.5, 9.0, 10.5 and 12.0 for both species.  The algal growth was measured by the determination of chlorophyll-a every 2 days. Results under laboratory conditions showed that the optimal salinity levels for growth ranged from 0 to 10 ppt for Oscillatoria sp., and from 0 to 6 ppt for Microcystis sp. An increase of the salinity decreased growth of both species. Water pH levels from 7.5 to 9.0 were suitable for growth of both species, while a pH below or above these range caused significant decrease in growth of these blue-green algae.