Biogeochemical cycling of lignocellulosic carbon in marine and freshwater ecosystems: Relative contributions of procaryotes and eucaryotes1

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Abstract
The relative contributions of procaryotes and eucaryotes to the degradation of the lignin and polysaccharide components of lignocellulosic detritus in two marine and two freshwater wetland ecosystems were determined. Two independent methods—physical separation of bacteria from fungi and other eucaryotes by size fractionation, and antibiotic treatments— were used to estimate procaryotic and eucaryotic contributions to the degradation of [14C‐lignin]lignocelluloses and [14C‐polysaccharide]lignocelluloses in samples of water and decaying plant material from each environment. Both methods yielded similar results; bacteria were the predominant degraders of lignocellulose in each of the aquatic ecosystems. Fungi and other eucaryotes contributed only minimally to the overall degradation of lignocellulose in both marine ecosystems and in the Okefenokee Swamp but did contribute significantly to the degradation of lignocellulose in the Big Cypress Swamp. These results indicate a basic difference between the microbial degradation of lignocellulosic material in terrestrial and aquatic environments. Fungi have long been considered the predominant degraders of lignocellulose in terrestrial systems; our results indicate that in aquatic systems bacteria are the predominant degraders of lignocellulose.