Environmental drivers of stream ecosystem structure and function in subarctic Labrador, Canada
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Date
2013
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University of New Brunswick
Abstract
The ecology of riverine ecosystems in the eastern Canadian subarctic remains
relatively unknown and, like their circumpolar counterparts, these systems are predicted
to be vulnerable to climate-induced ecological changes that are likely to affect species
composition, distribution, and overall ecosystem functioning. Thus, lotic systems in this
area must be evaluated in order to begin long-term monitoring of climate-driven
alterations to ecological structure and function. The aim of the present research was to
assess contemporary patterns in stream structure and function within the Torngat
Mountains National Park in subarctic Labrador and determine the environmental
(physicochemical) drivers of these ecological patterns. In particular, the study examined
the influence of environmental variables from multiple spatial scales on
macroinvertebrate assemblage structure, consumer trophic diversity and dietary overlap,
and cellulose decomposition rates. Environmental variables that were measured at the
reach scale ( a 1-km buffer around study sites), which included the relative area of
glaciers and various land cover types, produced the most variation in stream structure
and function. Glacier-fed streams had the lowest consumer richness and abundance, the
lowest trophic diversity and little dietary overlap, arid the lowest cellulose decay rates.
Cellulose decay rates were highest where consumer richness, trophic diversity and
dietary overlap were highest and where riparian input was greatest. Consumer diets
consisted primarily of allochthonous carbon (53 - 95%) and cellulose decay was likely
mediated primarily by shredder invertebrates, as microbial activity was not correlated
with decay rates. The present study provides baseline ecological data for long-term
stream ecosystem monitoring in the Park and suggests that changes in glacial extent,
source water contribution, and quantity and quality of riparian vegetation may cause the
greatest alteration in stream structure and function.