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Tropical estuaries often have a low buffering capacity and may experience acidification, both naturally through microbial degradation and run-off from acid sulphate soils (ASS), or from various anthropogenic sources. Here, we describe phytoplankton communities from the turbid, acidified, and eutrophic Sungai Brunei and Brunei Bay estuarine system. Four sampling stations were selected, representing the full spectrum of the salinity (0.4-28.5 PSU) and pH (5.87-8.06) gradients associated with this system. A total of 25 microalgal families of phytoplankton (including 22 diatom and seven dinoflagellate genera) and one of ciliates were recorded in the survey, which was carried out between August 2011 and June 2012. Phytoplankton density ranged from 7 to 9107 cells ml(-1). Diatoms were a dominant component of the communities, with Nitzschia spp., Rhizosolenia spp., and Leptocylindrus sp. reaching the highest abundances. Phytoplankton communities present at the four sampling stations differed significantly in terms of both algal abundance and composition and were strongly influenced by the effect of season (30% of the total variance). The interactive effects of pH and salinity, and of pH and temperature, explained 16.7% and 17.5% of the total observed variation, respectively. A positive correlation between pH and the number of taxa found was detected. The functional diversity observed in phytoplankton from the Brunei River estuary was generally low with few taxa adapted well to the chronically low pH conditions. This study provides baseline data about structural and compositional changes in a tropical estuarine phytoplankton community associated with various levels of acidification of both natural and anthropogenic origins.

Direct sampling of microalgae from nature inevitably brings together the problem of massive growth of bacteria and fungi. In this study, bacterial and fungal contamination level was evaluated from the Chlorella sp. isolated from two different locations of local freshwater area. Attempts to obtain axenic Chlorella sp. culture by combinations of antibiotic and antifungal at different range of concentration treatment were investigated. It is evident that there were three different bacteria and two different fungi present in the culture, but apparently sterility can be achieved when ampicillin, cefotaxime and carbendazim cocktail were employed at concentrations of 700 µg/mL, 200 µg/mL and 0.1µg/mL, respectively. These concentrations are also proven harmless toward Chlorella sp. as higher concentrations inhibit the growth of microalgae. It was found that by streaking the contaminated microalgae twice onto the TAP agar containing the previously described cocktail, completely removed the contaminating fungi and bacteria from the culture. In conclusion, this study suggested that axenic Chlorella sp. can be attained with this method and cocktail recipe.

Phytoplan11on is an important organism in the aquatic ecosystem as a primary producer. However, some species of phytoplankton also causes red tides or harmful algal blooms (HAB) which lead to negative impacts on human health, economics, aquaculture, fisheries and tourism. In this study, dinoflagellates, the main causative organism of red tides, were identified and enumerated from samples taken at Sebatu and Sungai Rambai, Malacca. In the identification of dinoflagellates, thecal plate tabulation and morphological characters of the cells were observed by light and electron microscopy.Thirty four species of dinoflageRates were identified, which consists of 10 potential HAB species viz.