Panel 1: summary

The GCE/LTER is focused on predicting impacts on coastal marshes of altered freshwater-river flow. We have begun our long-term research by measuring the secondary microbial productivity that takes place within naturally decaying, standing dead shoots. We estimate annual fungal production in cordgrass shoots to be about 0.5 kg m^-2 (about 40% microbial yield). Together, fungal plus sediment-bacterial annual production is about 0.7 kg m^-2. For one 11-km² saltmarsh watershed, grass+sediment decomposer-microbial production was about 8.5 tonnes yr^-1. [Fun calculation: this microbial mass would provide about 78 million 10-cm white shrimp at 1% yield!] We monitored biodiversity of ascomycetes and prokaryotes of the cordgrass-decay system, examining leaf blades at early decay (standing above the sediment) and late decay (clay-covered and collapsed onto the sediment), using cultural, direct-microscopic, and DNA-technological methods. We found no evidence via ascomycete-specific ITS/rDNA examination for cryptically active ascomycetes; the ascomycetes of this decay system (only 4-5 major species) are detectable by microscopy and agar-culturable. All of the principal ascomycetes exhibit laccase activity (which they probably use in lignocellulose decay), and their laccase genes can be detected in the naturally decaying leaves. Many of the prokaryotic species (α-proteobacteria 65-81% of clones; γ-proteobacteria, Gram+, and cytophagas <14%) detected by 16S rDNA cloning/sequencing and T-RFLP were not found as cultured isolates, but strains identical (rDNA sequences) or very close to the very common α-proteobacteria of standing-decaying leaves are culturable (e.g., Erythrobacter sp.), suggesting that experimental searches for fungal/bacterial consortial partners are feasible. A recent examination of living-fungal content and activities in leaves of marsh plants from saltmarsh toward freshwater marsh confirmed an hypothesized downward trend in fungal biomass, and revealed an unexpected upward trend in potential activity of the living biomass.