Effects of Climate, Limnological Features and Watershed Clearcut Logging on Long-Term Variation in Zooplankton Communities of Boreal Shield Lakes

Abstract

Abstract:In Canada, climate change and forest harvesting may both threaten the ecological integrity of boreal lakes. To disentangle the effects of natural variation in climate and lake environments from those of logging, we evaluated long-term variation (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) in zooplankton communities of six boreal lakes in Ontario. We monitored concomitantly changes in zooplankton abundance and composition in three undisturbed and three harvested lakes, five years prior and eight years after watershed clearcut logging. We tested the hypothesis that long-term natural variation in climate and lake environments will be more important drivers of zooplankton community changes than short-term impacts of logging. We used space/time interaction tests and asymmetric eigenvector maps to model zooplankton responses to environmental changes and logging. Year-to-year variation in zooplankton abundance and composition were almost an order of magnitude whereas among-lake variation was stable through time. Breakpoints in time series of zooplankton in each lake were not directly related to logging. Climatic and limnological features were the most important drivers of long-term variation in the zooplankton community, shading the effect of logging. These results highlight the need to better understand the pressures exerted by climate change on boreal lake ecosystems in the context of anthropogenic pressure, such as logging.

Ecological Responses of Lakes to Climate Change

“…While we intuitively expect that, for many other kinds of land use change, particular modifications that are long-lasting will influence how climate affects lakes, there are no experimental studies like that done by Levesque et al [31] to confirm this, because it is not feasible. The gap could be filled with long-term assessment of lakes with similar limnological characteristics and climate variation but different land uses, or by scenario modeling.…”

“…However, these are major lasting changes, and there may be some alternations in land use that are of shorter duration and that do not have these synergistic effects with climate change. In this special issue, Levesque et al [31] consider one such example-clear-cut logging in boreal Canada. They examine the long-term (1991-2003) temporal variation in zooplankton in six lakes to determine how they are affected by variation in precipitation, limnological conditions, and by factors linked to logging.…”

“…The aim of the study performed by Levesque et al [31] was to test whether natural variation in climate and limnological conditions are more important than the short-term impacts of logging. To do this, the authors performed whole-lake experiments.…”

Global lake responses to climate change

“…Many emerging changes in lake ecosystems are the result of complex interactions among a multitude of climatic factors, in addition to human activities and lake characteristics. The influence of climate remains persistently detectable, however, even across lakes also affected by factors such as oil and gas extraction 162 , forest harvest 163,164 and invasive species 164 . Human impacts on terrestrial nutrient cycles are among the most prevalent interacting factors, and the combination of increases in both nutrient inputs and temperature could be syner gistic, leading to hypoxic conditions and influencing community structure and biodiversity 165,166 and the fre quency, intensity, extent and duration of harmful algal blooms 138,167 .…”

“…Negative effects of legacy conditions can be magnified in the presence of warming, supporting proposed synergisms between chemical pollution and other stressors 168 . Lake responses are not necessarily regionally synchronous, as morphometric character istics are known to drive trajectories of warming 10 and ice loss 7 , and lake depth has also been linked to commu nity responses 163 . In general, climate change will likely amplify the negative effects of eutrophication and other stressors to lake ecosystems 169,170 .…”