Aquatic Sciences Meeting, Albuquerque 2001

SS19 Revisiting Redfield: C:N:P Stoichiometry in Aquatic Ecosystems (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 10:30:00 AM

Location: Acoma/Zuni/Tesuque

Urban, N, R, Michigan Technological University, Houghton, USA, nurban@mtu.edu

Apul, D, S, Michigan Technological University, Houghton, USA, dapul@hopper.unh.edu

C:N:P RATIOS IN FRESHWATERS: TRACERS OF TERRESTRIAL INPUTS, FOOD WEBS, CARBON FLOWS AND NUTRITIONAL STATUS

Major element ratios (C:N:P) in freshwaters have been shown to be more variable than in marine systems, but, nevertheless, to be useful indicators of nutritional status of phytoplankton and regulators of zooplankton species composition. This study will present a comparison of element ratios in seston, zooplankton, settling material, and surface sediments from five deep, alpine lakes and L. Superior. This comparison will demonstrate that (1) C:N ratios can be used to track terrestrially-derived organic matter even in large lakes; (2) C:N ratios change systematically as organic matter is processed within most lakes; (3) under particular circumstances, C:N ratios are decoupled from C:P ratios and are not good indicators of nutritional status; and (4) under the ultra-oligotrophic conditions in L. Superior, C:P ratios are tightly coupled with carbon (and phosphorus) flows and can discriminate foodwebs while C:N ratios track primarily the flow of terrestrially-derived carbon. Elemental ratios in L. Superior are one manifestation of the very different rates of cycling of carbon in near- and offshore waters.

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Aquatic Sciences Meeting, Albuquerque 2001

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