Associations of planktonic and periphytic rotifers in a Malaysian estuary and two nearby ponds

Samples were taken from a Malaysian estuary along a salinity gradient from full strength sea water down to a conductivity of 27 µS cm^–1. In a region where the conductivity fluctuated between 6500 and 14000 µS only empty loricas of Keratella cochlearis and Lecane bulla were found. Where the salinity reached a maximum of 3800 µS Lecane bulla was the dominant rotifer, and 17 other species were found. Where the conductivity remained below 1000 µS at all stages of the tidal cycle there were more species of rotifers, up to 33 at one station.The rotifer fauna of the estuary was compared to the assemblage found in two local ponds. Of the 63 species found in the estuary only 29 were also found in the ponds. Compared to the total known rotifer fauna of Malaysia the estuary has a higher proportion of Lecane species (40%), and the genera Brachionus and Trichocerca are under-represented.Species associated with inland saline waters, such as Brachionus plicatilis, B. dimidiatus and Hexarthra jenkinae were not found in the estuary.