Autumnal Biomass and Potential Productivity of Salt Marsh Fungi from 29° to 43° North Latitude along the United States Atlantic Coast

Abstract

It has been established that substantial amounts of fungal mass accumulate in standing decaying smooth cordgrass (Spartina alterniflora) marshes in the southeastern United States (e.g., in standing decaying leaf blades with a total fungal organic mass that accounts for about 20% of the decay system organic mass), but it has been hypothesized that in marshes farther north this is not true. We obtained samples of autumnal standing decaying smooth cordgrass from sites in Florida to Maine over a 3-year period. The variation in latitude could not explain any of the variation in the living fungal standing crop (as determined by ergosterol content) or in the instantaneous rates of fungal growth (as determined by acetate incorporation into ergosterol at a standard temperature, 20°C), which led to the conclusion that the potential levels of fungal production per unit of naturally decaying grass are not different in northern and southern marshes. Twenty-one percent of the variation in the size of the living fungal standing crop could be explained by variation in the C/N ratio (the higher the C/N ratio the smaller the fungal crop), but the C/P ratio was not related to the size of the fungal crop. Instantaneous rates of fungal growth were negatively related to the size of the living fungal crop (r ‫؍‬ ؊0.35), but these rates were not correlated with C/nutrient ratios. The same two predominant species of ascomycetes (one Phaeosphaeria species and one Mycosphaerella species) were found ejecting ascospores from standing decaying smooth cordgrass blades at all of the sites examined from Florida to Maine.

Microbial biomass, growth, and respiration associated with submerged litter of Phragmites australis decomposing in a littoral reed stand of a large lake

“…4 & 5). Both of these components of litter quality have been shown to affect the extent of microbial colonization and activity in other freshwater (Moran & Hodson 1989, Sinsabaugh et al 1993, Gessner & Chauvet 1994 and marine litter decomposition systems (Newell et al 1996, Newell et al 2000. However, of interest in the present study is that fungal growth rates were similar in leaf and stem litter, indicating that activity per unit biomass did not differ despite large differences in litter nutrient concentrations.…”

“…Collected fractions were mixed with 10 ml of scintillation fluid (Scintillator Plus, CanberraPackard) and radioactivity was determined using a scintillation counter (Canberra-Packard, model 1600 CA) that automatically corrected for quenching. Acetate incorporation rates were converted to fungal growth rates assuming 12.6 µg fungal biomass nmol -1 acetate incorporated, a value that has been established for fungi associated with standing dead leaves of the salt-marsh grass Spartina alterniflora (Newell et al 2000).Microbial respiration. Rates of microbial respiration associated with decomposing Phragmites australis litter were estimated from measurements of dissolved oxygen consumption.…”

Experimentally Simulated Global Warming and Nitrogen Enrichment Effects on Microbial Litter Decomposers in a Marsh

“…Fungi in both salt and freshwater marshes accumulate substantial biomass on leaves during the decomposition of standing dead shoots (20,36,40,41), but fungal biomass declines when the leaves eventually are dropped (35,36,46). This decline supposedly reflects stressful conditions when the fungi associated with the leaves move from the plant canopy to the sediment surface (36,46).…”

“…This includes wetlands dominated by emergent aquatic vegetation (21) where plant production often is high (1.5 kg shoot dry mass m Ϫ2 year Ϫ1 or more [23,29]), and only a small fraction is consumed by herbivores (11). In these systems, both bacteria and fungi colonize plant litter and produce a substantial biomass and/or play an important role in the decomposition process (9,21,36,41). The microbial communities colonizing decomposing plant litter can be characterized by means of bulk measures such as total bacterial and fungal biomass and by activity measurements such as respiration, which provide a broad integrative assessment of aerobic microbial metabolism (e.g., see reference 26).…”

Increasing evidence for the important role of Labyrinthulomycetes in marine ecosystems

“…One of the present constraints in understanding the ecological role of thraustochytrids is the lack of a suitable technique to measure productivity in natural samples. In contrast to the thymidineincorporation method for bacteria (Fuhrman and Azam 1982) and the ergosterol synthesis rate technique for fungi (Newell 2001, Newell et al 2000, no specific biochemical processes for estimating productivity of thraustochytrids has been found to date. Devising a technique to study productivity will tremendously help in understanding the dynamics of production and grazing that control the biomass of Labyrinthulomycetes in the marine environment.…”