Blue-green algae and nutrient concentrations in two Tor tambroides aquaculture ponds differing in construction

Two mahseer fish (Tor tambroides) aquaculture ponds located in Serian district, Sarawak were investigated for blue-green algae composition and nutrient dynamics in a six month period (January to June 2007). A total of 35 blue-green algae species belonging to 11 genera and four families were recorded. Genera Chroococcus, Nostoc, Oscil/atoria, Pleurocapsa andSynechocystis were found in both ponds. Potential toxin producer genera, Microcystis and Anabaena formed a visible brown bloom on the surface of the earth pond. The highest blue-green algal cell density was recorded in June for the earth pond (1,009,000 cells ml^-1) and in January for the HDPE pond (521,000 cells ml^-1). The highest chlorophyll a concentration was documented in June for both ponds (10.2377 11-µgl^-1 in HDPE pond and 172.1160 11-µgl^-1 in the earth pond). Nutrient concentration, namely soluble reactive phosphorus (SRP) (0.01-2.02 mgl^-1 in HDPE pond, and 0.01-0.29 mgl^-1 in earth pond), ammonia-nitrogen (0.01-0.90 mgl^-1 in HDPE pond and 0.01-0.45 mgl^-1 in earth pond) and nitrate (0.02-0.08 mgl^-1 in HDPE pond and 0.01-0.05 mgl^-1 in earth pond) were also recorded. This finding suggested that the earth pond is prone to experience algae bloom and at the same time, could support greater population of blue-green algae. Results also showed that SRP and nitrate are not the only factors that influence blue-green algae composition in aquaculture ponds but rather a combination of other multiple environmental factors.