Aquatic hyphomycetes in Catamaran Brook: colonization dynamics, seasonal patterns, and logging effects

Abstract

Aquatic fungal colonization dynamics and seasonal patterns were investigated in two sites in Catamaran Brook, New Brunswick, Canada, as part of a larger study to evaluate logging effects on a salmon stream. Four leaf-pack trials were conducted between May 1995 and Dec 1996 to determine species composition of the fungal community, the seasonal pattern of colonization on decaying maple leaves, and what effects, if any, invertebrate feeding and logging activities might have on community structure. Contrary to expectation, neither mesh size (i.e., invertebrate presence or absence) nor preliminary logging activity (road construction near one site) had a consistent effect on community structure. Time of immersion of the leaves in the stream, followed by season, were the major factors controlling community structure. Spore production and species diversity measures were highest during the middle part of the colonization period (generally 4–8 wk of immersion in summer trials and 2–4 wk immersion in the autumn trial), and were also higher in the autumn (Sep to Dec) than in the summer trials. Forty-five species of hyphomycetes were recorded during the study period, although 6 taxa (Alatospora acuminata, Anguillospora filiformis, Articulospora tetracladia, Geniculospora inflata, Lunulospora cymbiformis, and a sigmoid species, probably Flagellospora curvula) made up nearly 95% of all identified spores. A total of 35 species were found during the autumn trial, compared to 27 in each of the two summer trials, and 25 during a winter trial. Colonization dynamics also varied with season, but generally there were three main colonization patterns; some taxa were only present or showed highest abundance very early in the colonization period, most arrived or peaked during intermediate stages of leaf decay, and a few were characteristic of the latest stages.