Document: LAU-3-88-6

Dynamics of the deep chlorophyll maximum in lakes of the McMurdo Dry Valleys, Antarctica.

BURNETT, L.L.* and D.L.MOORHEAD

University of Toledo, Toledo, OH 43606 USA ¹

Abstract:
A common feature of many Antarctic lakes is the presence of a deep chlorophyll maximum layer (DCM). The DCM is a layer of chlorophyll a and phytoplankton biomass well below the water's surface. Such a DCM layer generally is found near a nitracline with a peak of primary production coincident with or just above that same maximum. DCMs are common to many regions and appear to arise from several different factors. Data provided by the McMurdo Long-Term Ecological Research program were used to examine four lakes in the Taylor Valley, Antarctica, (east Bonney, west Bonney, Fryxell, Hoare). Stepwise linear regressions were used to test the hypothesis that DCMs in these permanently ice-covered lakes were resource limited. The variables examined were: Photosynthetically active radiation (PAR) intensity, soluble reactive phosphorous concentrations, and dissolved inorganic nitrogen (NH₄ + NO₂ + NO₃) concentrations. Using data from all depths, the overall model for east Lake Bonney had an R² value of 0.554, with PAR being the most significant factor. Values for Lakes Fryxell, Hoare and Bonney west were (0.182, 0.661, and 0.254 respectively)dissolved inorganic nitrogen was the most significant factor in these models. When analyses focused on depths bracketing the DCM, dissolved inorganic nitrogen was the most important factor for all lakes; R² values decreased in Bonney east (0.352); remained essentially identical in Fryxell (0.186); and increased in Bonney west (0.329). Lake Hoare has no distinct DCM layer.

Keywords: deep chlorophyll maximum, Antarctica Antarctic lakes, nutrients

This abstract is being presented at: 11:30 AM in session:
Oral Session #54: Lake Ecology.