Sulphite and pH Effects on CO2Evolution by Fungi Growing on Decomposing Coniferous Needles

The relative sensitivities of Mycena galopus (Pers.) Kummer, Phoma exigua (Desm.), Cladosporium cladosporioides (Fres.) de Vries and Aureobasidium pullulans (de Bary) Arnaud to low concentrations (12.5-100.0 μM) of sulphite (SO3 2-) when growing on decomposing needles of Picea sitchensis (Bongard) Carriere (Sitka spruce) and Pinus sylvestris L. (Scots pine) were assessed. Carbon dioxide evolution from the decomposing needles was strongly inhibited by SO3 2-at pH 3.0-4.5. P. exigua was the most sensitive of the species tested in the mycelial state, and C. cladosporioides was the most sensitive species tested as spores. Mycelium was consistently less sensitive than spores. The inhibitory effect of SO3 2-on CO2evolution was increased by increasing the SO3 2-concentration or decreasing the pH. The concentrations shown to exert toxicity were similar to those which have been measured in rainfall in the UK, and the results provide evidence that SO3 2-can be toxic to litter fungi at environmentally realistic concentrations.