SS3.01 Landscape Control of High Latitude Lake and River Ecosystems
Date: Thursday, June 13, 2002
Time: 10:30:00 AM
Location: Carson A
 
MoorheadDL, University of Toledo, Toledo, USA, dmoorhe@uoft02.utoledo.edu
Hawes, I, , National Institute of Water and Atmospheric Research, Christchurch, New Zealand, i.hawes@niwa.cri.nz
 
INTERMITTENT PRODUCTION AND EROSION OF ORGANIC MATTER FROM SMALL PONDS OF THE ANTARCTIC DRY VALLEYS
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Small ponds are common features of ice-free terrain in continental Antarctica. Many receive water only from melting snow or glaciers, with losses occurring through evaporation and sublimation. Within these desert landscapes, many ponds contain dense benthic mats of algae and cyanobacteria. Organic matter accumulations exceeding 2 kg AFDW/sq m were recorded at pond margins in Taylor Valley during January 2000, a time of low water level. Model simulations based on field measurements of mat photosynthesis and respiration suggested accumulation rates of 25 g C/sq m/yr, for the time period corresponding to summer stream flow in the valley (ca. 75 days). However, liquid water is sustained beneath ice by solar heating even when air temperature is considerably below zero, likely supporting even greater annual production. Records of the Onyx River in adjacent Wright Valley demonstrate lower flows in the 1990s than in the previous 20 years. We suggest that mat production during periods of inundation and subsequent wind erosion of exposed organic matter during periods of desiccation provides an intermittent, local carbon subsidy from these ponds to adjacent dry valley soils.