Studies on fungal biomass and activity associated with the decomposition of plant litter in freshwater

Cook, Paul Edward (1987) Studies on fungal biomass and activity associated with the decomposition of plant litter in freshwater. Doctoral thesis, City of London Polytechnic.


A clearing and staining method using 2 stains, with one acting as a counter-stain for fungi, gave higher estimates of fungal biomass than other staining methods and it correlated well with the agar film technique. Using the method, it was possible to examine the spatial distribution of hyphae on leaves which varied between leaf types and fungal species.

Improvements were made to the agar film method by optimising extraction of hyphae from leaf litter and using a tetrazolium staining technique to detect metabolically active hyphae. An indirect method for estimating fungal biomass was developed using ergosterol as a marker. Conversion factors for ergosterol and biovolume to fungal biomass were shown to vary with fungal species, age and growth conditions, but no single parameter was found which could adequately explain this.

In field studies on flooded gravel pits biomass was 0.02-6.66/0 leaf dry weight depending on leaf type, biomass method and submersion time. Biomass estimated using clearing and staining was significantly correlated with ergosterol and with the agar film method; the latter gave the highest estimates. In terms of allochthonous litter inputs, fungal biomass represented 0.03-16.22 kg/ha.

Studies on a number of the gravel pit lakes demonstrated variation in communities of Ingoldian fungi both between lakes and within a single lake. Correlations were found with magnesium levels and litter inputs, but not with fungal biomass in the litter or cellulose decomposition. In one lake, decomposition of litter, fungal biomass and microbial populations were followed. No differences were found in biomass when animals were excluded although this influenced Ingoldian fungi. Higher numbers of Ingoldian fungi correlated with weight losses and biomass , and a competitive hierarchy was suggested to explain changes in fungal populations during decomposition.

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