Effects of pH and plant source on lignocellulose biodegradation rates in two wetland ecosystems, the Okefenokee Swamp and a Georgia salt marsh1,2,3

Abstract

The microbial mineralization of synthetic [ L4C]lignin, specifically radiolabeled [ 14C-ligninl-lignocellulose and [ L4C-polysaccharide]-lignocellulose from a variety of aquatic herbaceous and woody plants was investigated in water and sediment from a salt marsh on Sapelo Island, Georgia, and from the Okefenokee Swamp, an acidic peat-forming freshwater swamp in southern Georgia. Rates of microbial degradation of lignocellulose were depressed in the Okefenokee relative to those in the salt marsh. About 50% of the difference in mineralization rates was attributable to the low ambient pH (3.9) of Okefenokee water relative to the pH of salt marsh water (pH 7.1). Rates of mineralization of the lignin component of lignocellulose were only minimally affected within the range of pH 4-8, whereas mineralization of the polysaccharide component increased severalfold with increasing pH. Differences in the biodegradability of the various lignocelluloses were also observed; lignocelluloses from herbaceous plants were mineralized several times faster than lignocellulose from wood.

Decomposition in salt marsh ecosystems: phenolic dynamics during decay of litter of Spartina alterniflora

“…Thus, over this period of decomposition, these results are consistent with those of Marinucci et al (1983). Similarly, Benner et al (1985) found a strong positive correlation between initial nitrogen content of several plant species, including S. alterniflora, and rates of lignocellulose decomposition over the course of a 1 mo laboratory incubation experiment.…”

Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes

“…Early studies suggested that the lignin polymer was essentially inert in the absence of oxygen (Hackett etal., 1977). However, it has since been shown that the complex lignin polymer can undergo anaerobic degradation (Benner et al, 1985(Benner et al, , 1986, but the process can be rather slow and tends to yield unmetabolized products (Colberg and Young, 1982;Young and Frazer, 1987). Anaerobic loss of lignin polymers is -3-30% as complete as aerobic degradation of the same polymers (Benner et al, 1984); the cellulose component is more labile than the lignin component.…”

“…Organic matter deposited in near-shore marine and most freshwater habitats is composed primarily (-75% by weight) of lignocellulose, a complex mixture of lignin and the polysaccharides cellulose and hemicellulose (Benner et al, 1985). Lignin is a unique phenolic polymer of nonrepeating units that makes up 25-30% of the biopolymers in vascular plants and is second only to cellulose as the most abundant organic carbon source in the biosphere.…”

“…Eukaryotes also contributed significantly to lignin degradation in an acidic freshwater wetland, and eukaryotes degraded both lignin and polysaccharides in a slightly alkaline freshwater wetland. The polysaccharide component is usually decomposed several fold more rapidly than lignin, and the lignocellulose of herbaceous plants decomposes more readily than that of woody plants (Benner et al, 1985). The aerobic catabolism of lignin by fungi and filamentous bacteria utilizes ligninolytic peroxidases (Black and Reddy, 1991;Eriksson et ah, 1990), that often require manganese to be active (Brown et al, 1990;Gettemy et al, 1998).…”

A preliminary study on estimating extra-cellular nitrate reductase activities in estuarine systems

“…Conversion of complex organic molecules to simpler organic and inorganic constituents by various processes such as abiotic leaching (Harrison and Mann, 1975;Benner et al, 1985), fragmentation (Boulton and Boon, 1991), extracellular enzymatic hydrolysis (Cunningham and Wetzel, 1989), and aerobic and anaerobic catabolic activities of microorganisms could occur depending on environmental conditions, and export or recycle through the ecosystems. Learning the resilience and threshold levels allows to gauge the strengths and weaknesses of our technological advancement and policies to tackle adversities of hydro-climatic changes to many ecosystems including aquatic and semi-aquatic ones.…”