The effects of climatic warming on the properties of boreal lakes and streams at the Experimental Lakes Area, northwestern Ontario

Abstract

A period of prolonged warmer, drier-than-normal weather in northwestern Ontario during the 1970s and 1980s resulted in severe forest fires that caused dramatic changes to lake and stream catchments. The changed interactions of weather with catchments and hydrological processes caused unexpected changes in physical, chemical, and biological processes in lakes and streams. Permanent first-order streams became ephemeral. Flows at spring melt were lower, and chemical exports from catchments were reduced. Although catchments burned by forest fire had slightly higher flows and chemical exports than unburned basins in the years following fires, chemical exports generally declined due to lower streamflow. Decreased exports of silica indicated lower rates of weathering. Base cation exports also decreased, as did the ratio of base cations to strong acid anions in streams.Changes in lakes included warmer temperatures, clearer waters, deeper thermoclines and euphotic zones, higher alkalinities, and higher concentrations of base cations and nitrogen, but lower concentrations of dissolved organic C, silica, and P. The increase in alkalinity was caused by increases in the ratio of base cations to strong acid anions, resulting from the interaction of increased water retention, microbial sulfate reduction, and exchanges of cations between water and sediments. Declines in chlorophyll and increases in phytoplankton biomass were observed, but there was no detectable effect on areal phytoplankton production. Summer subthermocline habitats for cold stenotherms were reduced slightly in extent as the results of thermocline deepening and lower hypolimnetic oxygen. There is considerable potential for interaction between climatic change and other human perturbations affecting boreal lakes, including acidification, increased incident UV radiation, eutrophication, and overharvesting.

Temperature-controlled organic carbon mineralization in lake sediments

“…Within the boreal zone, warming affects organic matter load from primary production and import from the watershed widely different among regions, depending on different trajectories of precipitation. For example, while watershed OC export has decreased in parts of the Canadian boreal zone 50,51 , it has increased in some, but not all parts of Scandinavia 52,53 potentially resulting in concomitant changes in C delivery to the sediments 54. The robust relationship between temperature and OC mineralization ( Fig.…”

Landscape effects of climate, agriculture, and urbanization on benthic invertebrate communities of Canadian prairie lakes

“…Finally, community variability was also maximal since 1980 in Buffalo Pound Lake, a site without direct sewage inputs. Instead, we suggest that recent increases in algal production (Dixit et al 2000) and invertebrate community variation reflect regional climate change, as recorded east (Schindler et al 1996) and west (Vinebrooke et al 1998) of the Qu'Appelle drainage.…”

Increases in terrestrially derived carbon stimulate organic carbon processing and CO2 emissions in boreal aquatic ecosystems

“…There is now mounting evidence that shifts in climate and other environmental factors are driving increasing aquatic concentrations of terrestrially derived DOC in many landscapes of the world [7][8][9] , in what has been termed the 'browning' 10 of inland waters. Whereas the magnitude and regulation of the browning phenomenon are the focus of intense research and debate 7,[11][12][13][14][15][16][17] , the potential implications of such a shift in terrestrial carbon (C) concentrations for the functioning of the receiving aquatic systems have been less explored, particularly in terms of the impacts on aquatic CO 2 emissions.…”