Carbon conversion efficiency for bacterial growth on lignocellulose: Implications for detritus‐based food webs

Abstract

Carbon conversion efficiencies were determined for the bacterial utilization of lignocellulosic detritus in waters from an estuarine and a freshwater wetland. Conversion efficiencies during bacterial growth on lignocellulose averaged ∼30% in both estuarine (salt marsh) and freshwater (Okefenokee Swamp) samples. Our estimates of bacterial growth efficiencies on refractory particulate detritus are twofold to threefold higher than previous estimates owing, in large part, to the higher biovolume‐to‐carbon conversion factor (0.22 g C cm‒3) used in the present study to convert bacterial biovolumes into units of carbon. Bacterial growth on lignocellulosic detritus was N limited in salt‐marsh water and P limited in Okefenokee water; carbon conversion efficiencies increased to 45% upon addition of ammonium and phosphate to salt‐marsh and Okefenokee incubations, respectively. These results indicate that bacterial biomass produced at the expense of lignocellulosic detritus is likely to be an important nutrient source to food webs in aquatic ecosystems with an abundance of macrophyte detritus and favorable conditions for microbial decomposition.