EFFECTS OF ALUMINUM IN ACID STREAMS ON GROWTH AND SPORULATION OF AQUATIC HYPHOMYCETES

We investigated, by field and laboratory experiments, the effects of a luminium lit an acid sti earn (pH 5.0) on the growth and sporulation o f aquatic hyphomycete fungi which degrade organic litter. The stream w ater had monomeric aluminium (Al-m) concentrations of 9.1-13.4 mu M - fifty times higher than a nearby circumneutral stream. Alder leaves su bmersed in the stream accumulated Al, most of which was tightly bound. Growth rates of four species of aquatic hyphomycetes were altered by inclusion of Al-m in the culture medium. On a polypectate substrate, a nd on low-phosphate medium with glucose, growth rates increased signif icantly. On a low-nutrient substrate of homogenized alder leaves, grow th rates were inhibited by aluminium. The pattern of mycelial growth w as found to be different on a polypectate medium including Al-m, compa red with a control without aluminium. There was a significant increase in hyphal radial growth and a decrease in the hyphal growth unit. The effect resembled the growth of a starved fungal colony. Treatment wit h Al-m, decreased pectinase production It the four fungal species test ed. The capacity of these species to sporulate Mas reduced by flooding culture plates with Al-m solution. These deleterious metabolic effect s were most severe in isolates taken from circumneutral streams and le ss marked, though significant, in species originating from acid stream s. (C) 1997 Elsevier Science Ltd.