Ecosystems in transition: Exploring limnological conditions in lakes spanning the Canadian prairie to Montane Cordillera ecotone

Environmental characteristics shift predictably with altitude, generating gradients of temperature, hydrology, and vegetation. However, how such environmental gradients transmit an effect on the ecology of freshwater ecosystems is not well understood in ecotones. To test this, we sampled 11 lakes spanning a 600m elevation gradient along the ecotone between the Canadian Prairies and Montane Cordillera. We hypothesized that shifting lake elevation and climatic and catchment features would alter the quality and quantity of allochthonous inputs, thus determining lake chemical composition and metabolic rates. We analyzed catchment variables, water chemistry, lake metabolic rates, and dissolved organic matter (DOM) composition. Surprisingly, the differences in catchment composition and water temperature along the elevation gradient were not clearly linked to DOM content nor composition. DOM composition was dominated by autochthonous sources, and most lakes were net autotrophic. Yet, primary production and respiration rates were linked to elevation indirectly through changes in water temperature. While production and respiration both scaled with DOM content, net ecosystem production was unrelated to elevation and peaked at intermediate DOM levels. Overall, while environmental features shift predictably along the ecotone, they transmit inconsistent effects to the limnology of regional lakes. We attribute the limited influence of elevation (i.e., position in the ecotone) to the region's overall low precipitation regime and lakes' low hydrological connectivity with their catchments

Presentation Preference: Oral

Primary Presenter: Paola Ayala-Borda, University of Lethbridge (p.ayalaborda@gmail.com)

Authors:

Paola Ayala-Borda, University of Lethbridge  (paola.ayalaborda@uleth.ca)

Jean-François Lapierre, Université de Montréal  (jean-francois.lapierre.1@umontreal.ca)

Milla Rautio, Universté du Québec à Chicoutimi  (milla.rautio@uqac.ca)

Sarah Ellen Johnston1, University of Alaska Fairbanks  (sejohnston2@alaska.edu)

Matthew Bogard, University of Lethbridge  (matthew.bogard@uleth.ca)