Document: JAM-3-88-7

Carbon flow dynamics in benthic microbial mats of Lake Hoare, Antarctica.

SCHMELING, J.D.* and D.L.MOORHEAD

University of Toledo, Toledo, OH 43606 USA ¹

Abstract:
Carbon is sequestered by cyanobacteria-dominated microbial mats in the permanently ice-covered lakes of Antarctica. Light availability under the ice of Lake Hoare, in the McMurdo Dry Valleys, is approximately 1% of ambient photosynthetically active radiation (PAR). A mathematical model was used to simulate the response of microbial mats in Lake Hoare to changing light intensity, in relation to annual accumulation of mat biomass. Currently, microbial mats at 5 m depth accumulate about 97 ug C m² annually at a maximum photosynthetic rate equal to 1.40 u g C m^-2h^-1. This occurs during a brief period of approximately 145 days. Inactivity during winter allows for sediment accumulation/deposition on the top of the mat, resulting in a layering of organic and inorganic materials in sediments. Model simulations suggest that microbial mats at 4 meters depth would show little response to increased light intensity, as their photosynthetic rates are saturated at extremely low light levels. Thus, variations in organic matter deposition revealed by benthic sediment cores over the past 1200 years are unlikely to be the direct result of fluctuating light intensity that could have resulted from changing ice thickness or attenuation by the water column.

Keywords: Microbial Mats, Antarctic Lakes

This abstract is being presented at: 11:15 AM in session:
Oral Session #54: Lake Ecology.