Fungal content and activities in standing-decaying leaf blades of plants of the Georgia Coastal Ecosystems research area

Abstract

Change in salinity, including expansion or contraction of salt-and freshwater marshes, due to altered river outflow may influence a variety of ecosystem processes, and the literature to date suggests that fungal activity in standing-decaying blades of macrophytes may be lower in freshwater marshes than in saltmarshes. I measured living-fungal mass (as ergosterol), rate of CO 2 evolution, and rate of fungal membrane synthesis (acetate incorporation into ergosterol) for standing-decaying blades from a series of macrophytes, including saltmarsh cordgrass in both saline and fresher-water sites. Three terrestrial plants with prominent standing-decaying leaf blades were included for comparison. Species involved were: Spartina alterniflora, S. cynosuroides, Zizaniopsis miliacea, Typha angustifolia, Sabal palmetto, Uniola paniculata, and Panicum amarum. Although there was no difference in fungal content of S. alterniflora blades from saltier and fresher sites, there was a significant trend downwards (from > 500 to < 250 µg ergosterol g -1 system organic mass) in mean content of living-fungal mass moving from saltmarsh-adapted toward freshwater-adapted plants, and 2 of 3 terrestrial plants were also low (ca. 100 µg g -1 ). The activity measurements (CO 2 , acetate incorporation) revealed an opposite pattern: blades from fresher-water plants had higher activities per unit livingfungal mass (range of about 4-fold for mean rate of acetate incorporation per unit ergosterol), and lower CO 2 release per unit fungal membrane synthesis, than did more saline-adapted plants. It is proposed that this is perhaps largely a consequence of the microstructure (lignification, cuticular hydrophobicity) of the blades of the fresher-water plants (and 2 of the terrestrial plants) limiting duration of fungal activity. Upon thorough wetting, such as eventually occurs when blades move to the marsh-sediment surface, fungi within the fresher-water blades would be permitted to grow quickly, which would explain reported increases in ergosterol content of fallen blades.KEY WORDS: Fungal biomass · Fungal productivity · CO 2 release · Standing decay · Ergosterol · Saltmarsh · Freshwater marsh · Altamaha River Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 32: [95][96][97][98][99][100][101][102][103] 2003 acetate incorporation into ergosterol (Newell 2001a). This substantial fungal productivity is consistent with findings of high rates of animal outflow associated with Georgia saltmarshes (Turner & Boesch 1988, Kneib 2000, Teal & Howes 2000, Zimmerman et al. 2000, and with accumulating evidence of fungal input into the marsh foodweb (e.g. Graça et al. 2000).The high rates of fungal production per unit decaysystem mass found for smooth cordgrass contrast sharply with rates found using the same techniques during cold and warm seasons for a freshwater sedge (Carex walteriana, Walter's sedge) (1 technique difference: 20°C incubation for cordgrass and 25°C for sedge; Newell et al. 1995). The maxi...

effect of tetracycline on the colonization and growth of microbes on Scirpus lacustris litter in oligotrophic and eutrophic waters

“…Our data confirm the increase in microbial cell volume following submergence of dry litter in other studies (Newell 2003), which is likely due to the availability of moisture, a limiting factor for microbes in/on standing litter.…”

Organic Biogeochemistry of Detrital Flocculent Material (Floc) in a Subtropical, Coastal Wetland

“…Candau et al (1992) and Ferna´ndez-Martı´n et al (2000) showed that fungi can biosynthesize kaurene instead of ergosterol, which has been frequently used as a biomarker for fungi under nitrogen limiting conditions (e.g. Newell 2003;Nikolcheva et al 2003). In fact, ergosterol was not observed in these samples.…”

Introduction and Overview

“…Filamentous fungi and yeasts are found in the oceans, but these heterotrophic eukaryotes do not appear to be abundant and are not ecologically important in aquatic ecosystems, except as decomposers of dry detritus from vascular plants in coastal regions (Newell 2003). Fungi and yeasts live on DOM or particulate organic detritus, and thus would have to compete with heterotrophic bacteria and archaea in the oceans.…”