COMPARISON OF DETRITUS DYNAMICS IN 2 TIDAL FRESH-WATER WETLANDS

Examined the generation and persistence of detritus in 2 contrasting tidal freshwater wetlands on the Hudson River: Tivoli South Bay is dominated by a floating-leafed macrophyte (water chestnut Trapa natans); North Bay is a typical Typha marsh. In South Bay, there was a large amount of water-chestnut dry biomass (400 g/m2) available to enter the detritus pool, but there was no increase in the standing stock of benthic organic matter following senescence of water-chestnut. Mineralization plus leaching of dissolved material are sufficient to remove much of this detritus. In the Typha marsh, there is a large amount of detritus generated (c25% of annual primary production); this material persists as a thick litter layer. Decomposition of this litter is very slow (0.3/yr). A portion of the litter may be exported because decomposition alone cannot account for the observed rate of disappearance from the marsh surface. Bacterial growth on water-chestnut detritus is relatively slow (106 cells.mg-1.d-1), resulting in a turnover of bacterial biomass in 10-36 d. Bacterial and fungal biomass associated with Typha were low, and could not account for the observed increase in N content. -from Authors