AQUATIC FULVIC-ACIDS IN MICROBIALLY BASED ECOSYSTEMS - RESULTS FROM 2 DESERT LAKES IN ANTARCTICA

We characterized fulvic acids from two Antarctic lakes to determine the chemical characteristics of dissolved fulvic acid derived from organic material of microbial origin. These lakes receive very limited inputs of organic material from the surrounding barren desert, but they sustain algal and bacterial populations under permanent ice cover. One lake has an extensive anoxic zone and high salinities; the other is oxic and has low salinities. Despite these differences, fulvic acids from both lakes had similar elemental compositions, carbon distributions, and amino acid contents, indicating that the chemistry of microbially derived fulvic acids is not strongly influenced by chemical conditions in the water column. Compared to fulvic acids from other natural waters, these fulvic acids have low C: N atomic ratios (19-25) and low contents of aromatic carbons (5-7% of total carbon atoms); they are most similar to marine fulvic acids.