EFFECT OF PH ON THE DISTRIBUTION AND OCCURRENCE OF AQUATIC FUNGI IN 6WEST-VIRGINIA MOUNTAIN STREAMS

Aquatic fungi in six streams located on or near the Fernow Experimenta l Forest in Tucker County, West Virginia, were studied during the 1991 and 1992 growing seasons. Water pH was > 5.9 in three of the streams, while the others were more acidic, with average pH = 4.2, 3.9, and 3. 2. Sampling methods included (i) isolating conidia from stream water u sing membrane filtration, (ii) placing bags containing leaves of four tree species in the streams for periods ranging from 2 to 16 wk, and ( iii) baiting the streams with various types of other organic material. The stream mycoflora included 156 taxa (47 zoosporic fungi [chytridia ceous fungi and water molds] and 109 hyphomycetes [60 Ingoldian and 49 non-Ingoldian forms]). Twenty-seven taxa of zoosporic fungi were reco rded from the stream with the highest pH (7.9); only 15 to 18 taxa wer e collected from other streams. Based on conidia filtered from water s amples, the number of taxa of hyphomycetes generally was lower in stre ams with low pH; however, fewest conidia were recorded at the two extr emes of the pH gradient. Northern red oak (Quercus rubra L.) leaves we re colonized by an average of 16.0 hyphomycete taxa in the six streams , sugar maple (Acer saccharum Marsh.) by 15.3 taxa, and mixed red mapl e (A. rubrum L.), and American beech (Fagus grandifolia Ehrh.) by 15.2 taxa. For all three types of leaves, more taxa generally were present in the less acidic streams and fewer in the more acidic streams.