Colonization patterns of wood-inhabiting fungi on baits in Hong Kong rivers, with reference to the effects of organic pollution

The diversity of wood-inhabiting fungi was investigated by submerging woody baits at upstream and downstream sites of the Lam Tsuen and Tai Po Rivers in Hong Kong. The diversity of fungi in the Lam Tsuen River was also compar ed with that on natural woody substrates found in a previous study. There w ere differences in the species composition between the upstream and downstr eam sites, possibly reflecting natural variations along the river. The Tai Po River downstream was organically polluted, which appeared to have little effect on species diversity since more species were recorded. Organic poll ution may, however, cause a shift in species composition. The fungal commun ities on baits and natural substrates in the Lam Tsuen River were similar, although a lower diversity was observed on baits. This may be related to th e period of submergence and the fact that a single wood type was used. Cerc ophora spp. occurred frequently downstream in the Tai Po River, while the c ommon species in the Lam Tsuen River were Aquaticola rhomboidea and Pseudop roboscispora aquatica. Further interpretation on the effects of organic pol lution was limited because of single collection data but appropriate experi mental designs - putting baits in unimpacted sites for assessing human impa cts in streams - are suggested.