Microbial dynamics associated with decomposing Typha angustifolia litter in two contrasting Lake Erie coastal wetlands

Abstract

We compared the decomposition of sediment-associated litter of Typha angustifolia in 2 Lake Erie coastal wetlands, examining the effects of sedimentation on microbial biomass, production and litter decay dynamics. Experimental manipulations of sediment had no statistically significant effect (p > 0.05) on microbial biomass or metabolism. However, unforeseen differences between wet- land sites (i.e. permanently inundated vs. exposed) had a major influence on microbial colonization and growth, litter mass loss, and nutrient dynamics. Litter-associated bacterial biomass and produc- tion were greater at the inundated site vs. the exposed wetland site (e.g. 487 vs. 158 µg C g -1 detrital C after 146 d, respectively). In contrast, fungal biomass and production were greater at the exposed site (e.g. 125 vs. 56 mg C g -1 detrital C after 146 d, respectively). Microbial degradative enzymes involved in the acquisition of phosphorus, nitrogen and carbon followed similar patterns as observed for fungal biomass and production, with higher activities associated with decaying litter at the exposed site. Microbial respiration rates were initially similar at both sites, but increased at the inun- dated site towards the end of the study period. Despite greater litter-associated microbial biomass, production and enzyme activities at the exposed wetland site, rates of litter mass loss were similar, suggesting that the greater metabolic potential of microbiota at the exposed site may have been off- set by environmental conditions (e.g. fluctuations in water availability). Although mass loss rates were similar, significant differences in nutrient dynamics were observed, with higher N and P asso- ciated with higher litter-associated microbial biomass. These results illustrate how microbial decay dynamics can potentially interact with environmental variables (e.g. water availability) to modulate the carbon and nutrient dynamics of a litter resource that dominates many wetlands.