Sulphite and pH effects on CO2 evolution by fungi growing on decomposing coniferous needles

summary The relative sensitivities of Mycena galopus (Pers.) Kummer, Phoma exigua (Desm.), Cladosporium clodosporioides (Fres.) de Vries and Aureobasidium pullulans (de Bary) Arnaud to low concentrations (12.5–100.0 μM) of sulphite (SO2−3) when growing on decomposing needles of Picea sitchensis (Bongard) Carrière (Sitka spruce) and Pinus sylvestris L. (Scots pine) were assessed. Carbon dioxide evolution from the decomposing needles was strongly inhibited by SO32− 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 SO32− on CO2, evolution was increased by increasing the SO32− 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 SO32− can be toxic to litter fungi at environmentally realistic concentrations.