Colonization of periphytic algae on artificial substrates in a tropical stream

Standard periphyton samplers were used to examine the colonization pattern of periphytic algae on an artificial substrate (glass slides) in the Lam Tsuen River, Hong Kong, between October 1995 and August 1996. Changes in the taxonomic composition, species diversity (Shannon-Wiener diversity index), total standing crop, as well as the abundance of individual algal species were monitored over a six-week period in each season. Diatoms were most dominant in terms of cell density and biovolume, while green algae were important in terms of cell biovolume in autumn and summer. Of the 81 algal species observed, the pennate diatoms were most abundant. Dominant algal species included Achnanthes minutissima, Gomphonema parvulum, G. angustatum, G. rhombicum, Synedra rumpens var. familiaris, Nitzschia palea, Cocconeis placentula, Mougeotia spp., Spirogyra spp., Stigeoclonium aestivale and Schizothrix calcicola. A maximum algal density of 3.45 x 10⁶ cells per cm² was observed after a 4-week field incubation in spring (April and May), while maximum algal biovolume (1.20 x 10⁶ μm³cm^-2) was recorded after a 6-week field incubation in summer (July and August). In general, the standing crop reached its maximum at week 4. Seasonal variations in the succession patterns of the periphytic algal communities are described.