EFFECT OF DISSOLVED NUTRIENTS ON 2 AQUATIC HYPHOMYCETES GROWING ON LEAF-LITTER

Concentrations of potassium nitrate, potassium phosphate, or calcium c hloride were varied in stream-simulating microcosms containing leaf di scs colonized by the aquatic hyphomycetes Anguillospora filiformis or Lunulospora curvula. Cumulative conidium production of the fungi deter mined from rates of sporulation at 2 d intervals was stimulated by inc reasing concentrations of both potassium nitrate and potassium phospha te but not by calcium chloride. Leaf weight loss was also stimulated b y increasing concentrations of potassium nitrate and potassium phospha te. The amount of fungal biomass (determined as ATP concentrations) as sociated with leaf discs increased significantly only in the treatment s in which A. filiformis received increasing concentrations of potassi um nitrate. These results indicate that as aquatic hyphomycetes grow o n leaf litter, they can obtain at least a portion of their inorganic n utrition from the water flowing over the leaves. They also suggest tha t sporulation is more sensitive to changes in nutrient concentrations than growth.