MICROBIAL CONSORTIA IN WETLAND SEDIMENTS - A BIOMARKER ANALYSIS OF THE EFFECTS OF HYDROLOGICAL REGIME, VEGETATION AND SEASON ON BENTHIC MICROBES

Microbial consortia in the sediments from a permanent wetland near Alb ury-Wodonga in north-eastern Victoria, Australia (Ryans 1 Billabong), and an ephemeral wetland near Shepparton in central Victoria (Raftery' s Swamp) were quantified by analyses of phospholipid fatty acid (PLFA) , polar lipid ether lipid (PLEL), sterol and alcohol profiles. Prokary otic organisms dominated the benthic assemblages in both wetlands, Tot al prokaryotic abundance (i,e. eubacteria plus archaea) was estimated to be (7-17) x 10(9) cells g(-1) sediment (dry weight). Methanogenic a rchaea were estimated to number (1-5.4) x 10(9) cells g(-1) and to acc ount for 11-35% of the total benthic prokaryotes; these values are app arently among the highest recorded for temperate lake or river environ ments, PLFAs indicative of specific metabolic groups (e.g. sulfate-red ucing bacteria (SRB), methanotrophic bacteria, etc.) were also detecte d. The PLFA profiles indicated that Type I methanotrophs (abundant in C-16 PLFAs) were more abundant than the Type II group, which contain C -18 PLFAs. Acetate-utilizing SRB were more abundant than were lactate- utilizing SRB, but neither group was dominant. Ergosterol was not dete cted, which suggested that fungi were not a significant component of t he benthic microbial consortia in spite of both wetlands having abunda nt inputs from aquatic and fringing vascular plants, Other biomarkers, such as sterols, long-chain alcohols, triterpenoids and phytol, demon strated inputs from these higher plants. PLFA, PLEL and sterol profile s indicated that benthic microbial consortia were affected by hydrolog ical regime, the presence of aquatic vegetation, and season. Informati on from this preliminary study may assist in the making of informed ma nagement decisions on environmental water allocations for natural ecos ystems.