Document: DAR-3-88-9

Carbon fluxes within the pelagic food web of an Antarctic lake: Even slower than expected.

MOORHEAD, D.* ¹, E.ROBERTS ², J.LAYBOURN-PARRY ² and J.SCHMELING ¹

University of Toledo, Toledo, OH 43606 USA ¹
University of Nottingham, Loughborough UK ²

Abstract:
A model was developed to simulate carbon flow through the pelagic food web of Lake Fryxell, a permanently ice-covered lake in the McMurdo Dry Valleys, Antarctica. This community consists of seven trophic groups: Bacteria, phytoplankton, photosynthetic nanoflagellates (PNAN), heterotrophic nanoflagellates (HNAN), bacterial-feeding ciliates, flagellate-feeding ciliates and rotifers. Respiratory rates for groups were estimated according to allometric equations based on average individual mass and total pool size, and adjusted for temperature. Carbon inputs were set equal to losses due to respiration and predation, assuming no net change in pool sizes. Relative magnitudes of carbon flows between trophic groups were similar between simulations and estimates based upon clearance rates determined in laboratory studies. However, absolute values of fluxes were approximately an order of magnitude greater for simulations. Simulated rates of total community respiration also were nearly an order of magnitude higher than field observations (ca. 46.4 vs. 5.5 ugC l^-1 d^-1), although the relative contribution of bacterioplankton to total community respiration was similar between observations and simulations (79 vs. 76%, respectively). These results suggest metabolic processes of microplankton at low temperatures (ca. 2 C) are lower than could be predicted from standard allometric equations and Q₁₀ functions for a size-based carbon flow model.

Keywords: aquatic food webs antarctica

This abstract is being presented at: 12:00 PM in session:
Oral Session #54: Lake Ecology.