Rapid breakdown of allochthonous and autochthonous plant material in a eutrophic river

Carbon/nitrogen ratios and breakdown of leaves of Populus tremuloides (allochthonous) and the aquatic macrophytes, Ceratophyllum demersum and Potamogeton pectinatus (autochthonous), were investigated in a eutrophic river. The allochthonous material had a C/N ratio 5-6 x greater and decayed slower than either of the macrophytes. The decay rates measured for these species were greater in this eutrophic system than has been reported for the same species in more oligotrophic systems. The rapid breakdown of the plant material and the eutrophic condition of the river suggest the microbial decomposer community may have been limited, at least in part, by the availability of detrital organic carbon, rather than dissolved nutrients only.