SS3.01 Landscape Control of High Latitude Lake and River Ecosystems
Date: Thursday, June 13, 2002
Time: 11:30:00 AM
Location: Carson A
 
SpearsBM, Simon Fraser University, Burnaby, Canada, bspearsa@sfu.ca
Lesack, L, F, Simon Fraser University, Burnaby, Canada, Lance_Lesack@sfu.ca
 
EFFECTS OF NUTRIENT LIMITATION ON BACTERIAL PRODUCTIVITY AMONG LAKES OF THE MACKENZIE DELTA, WESTERN CANADIAN ARCTIC
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Lakes within the Mackenzie Delta (25,000 lakes) exhibit variation in flooding frequency and duration (will change with climatic warming), that may strongly influence the relative roles of bacteria versus autotrophs. To assess links among bacterial production versus nutrient supply and demand associated with flooding regimes, the weekly dynamics of bacterial productivity (3H-thymidine uptake) was tracked among 6 lakes of varying flooding-frequencies and mixtures of colored and non-colored DOC, over an open-water season. To assess nutrient demand, bioassays of N-debt and P-debt were performed weekly on the plankton community from the 6 lakes, and bacterial productivity was compared among lakes via lab-incubated microcosms after amending with nutrients (N versus P versus both). Bacterial productivity generally increased from frequently-flooded lakes to infrequently-flooded lakes. Bioassays showed significant demand for N or P among all study lakes (frequently- and infrequently-flooded), and showed seasonal switches between P-demand and N-demand. Bacterial productivity among all lakes increased significantly in response to nutrient enhancements in early summer, but showed little response to the enhancements later in the season.