Authors: Conrad A Murphy Patrick L Thompson Rolf D Vinebrooke
Publish Date: 2010/02/24
Volume: 648, Issue: 1, Pages: 83-90
Abstract
To demonstrate the sensitivity of aquatic ecosystems to forecasted increases in nitrogen deposition along the eastern ranges of the Canadian Rocky Mountains we conducted midsummer limnological surveys of 29 remote alpine lakes and ponds via helicopter in 2007 Chemical analysis of water and in vitro nitrogenenrichment bioassays of phytoplankton collected from each site were performed to estimate nutrient limitation Use of a common chemical index for nutrient limitation total dissolved inorganic nitrogen total phosphorus DINTP together with supportive experimental evidence revealed nitrogen limitation in only 14 of the cases Shallow ≤1 m maximum depth ponds were more likely to be nitrogenlimited than lakes especially as the former exhibited a significantly lower mean DINTP ratio of 74 during the late summer Chemical and bioassaybased inferences of nitrogen limitation agreed in 745 of the cases owing mainly to evidence of phosphorus limitation of the surveyed lake ecosystems mean DINTP = 18 being supported by nonsignificant responses of their phytoplankton to nitrogen amendment Our findings reveal that increased nitrogen deposition should not result in immediate widespread eutrophication of the Canadian Rockies however certain alpine ponds appeared nitrogenlimited making them sensitive early indicators of the potential effects of anthropogenic nitrogen deposition in remote mountainous regionsThis study was supported by grants from the Alberta Ingenuity Centre for Water Research and the Natural Sciences and Engineering Research Council of Canada to RDV We also thank Parks Canada for their permission to conduct our research in the national mountain parks of Canada
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