SS3.13 Natural Disturbances on Landscapes and Their Impacts on Aquatic Systems
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
GarciaE, Univ. Montreal, Montreal, Canada, edenise.garcia@umontreal.ca
Carignan, R, , Univ. Montreal, Montreal, Canada, richard.carignan@umontreal.ca
 
INFLUENCE OF WILDFIRES ON THE NITROGEN ISOTOPIC RATIO IN AQUATIC ORGANISMS
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We determined the carbon and nitrogen stable isotope ratios (delta 13C and delta 15N) of four groups of benthic invertebrates (Amphipoda, Ephemeroptera, Trichoptera and Odonata) and six species of fish (walleye, whitefish, white sucker, northern pike, yellow perch and brook trout) from 38 lakes with burnt, logged or undisturbed catchments. The delta 13C ranges of organisms from the three groups of lakes tended to overlap. Organisms from nine severely burnt lakes, however, showed a consistent enrichment in delta 15N. In these lakes, a pulse of nitrate was observed following fire, with concentrations up to 60-fold those found in reference or logged lakes. Total nitrogen and NH4+ also tended to be higher in fire-impacted lakes. Possible causes leading to the clear aquatic 15N signal due to wildfire will be discussed.