THE IMPACT OF VARIATION IN STREAM FLOW ON THE ECOLOGY OF A CLOSED-BASIN LAKE IN TAYLOR VALLEY, ANTARCTICA

The McMurdo Dry Valleys of Antarctica constitute a large and significantly ice free area of Antarctica at 78 degrees south latitude. Over the past 19 years data have been gathered on the lakes located in Taylor Valley, Antarctica as part of the McMurdo Valley Long-Term Ecological Research program (MCM-LTER). This study is part of a larger study that seeks to understand the impact of climate on the biological processes in all the ecosystems within Taylor Valley, including the lakes. These lakes are stratified, closed-basin systems and are permanently covered with ice. Previous work has demonstrated that biological activity in the lakes is mostly driven by ice thickness and the input of photosynthetically active radiation (PAR). Stream input of nutrients is also thought to be a significant factor in lake productivity. The work presented here focuses on one of the three main lakes in Taylor Valley, Lake Fryxell, which is fed by 13 streams. The majority of these streams are gaged and discharge measurements are available for the entire time period of the LTER. We summarize these discharge data over different time scales (from daily to seasonally) and use it as an explanatory variable for variations in lake properties: primary production, bacterial production, etc. In our statistical approach we show the effect of stream input on the biological activity in Lake Fryxell. In this study, light and temperature profiles of the lake, stream temperature and discharge, and ice thickness data will be related temporally. Our calculations suggest that discharge into the lake contributes heat energy to the lake and that this heat energy is significant enough to noticeably reduce ice thickness and hence may affect primary production.