Fungal colonization and breakdown of sedge (Cyperus malaccensis Lam.) in an Indian mangrove

We studied patterns of fungal colonization, mass loss and biochemical changes during decomposition of the dominant mangrove sedge Cyperus malaccensis in a mangal located in southwestern India. Litter bags containing dried bracts, basal stem and top stem were introduced into a sedge sward in a mid-tidal zone for periods of up to 8 weeks (April-June 2005). After retrieval of sedge substrates and incubation in the laboratory, 19 fungi (10 anamorphs, 8 ascomycetes and one zygomycete) were found. Terrestrial fungi dominated over the first 2-3 weeks. Later, in spite of falling water temperatures and salinity, they were replaced by typical mangrove/marine ascomycetes and anamorphs. Up to 79% of bract mass loss occurred in 4 weeks; respective losses for basal stems and top stems were 88% and 51% through 8 weeks. The estimated durations of 50% mass loss (t₅₀) were 4.5, 10.9 and 22.9 days for bract, basal stem and top stem, respectively. Accordingly, there were significant differences in daily decay coefficients (k) among substrates. Organic carbon and phenolics decreased steadily in all substrates. Phosphorus concentrations decreased, attained a minimum and increased again, reaching final concentrations similar to initial values. Nitrogen concentration increased through the end of the experiment. Cellulase, xylanase and pectinase in all sedge substrates generally peaked within 4 weeks. This is the first study on decomposition of the macrophyte C. malaccensis.