A paleolimnological perspective on avian population dynamics and their effect on lake productivity in a rapidly warming Arctic

Rapid warming since the 19th century is transforming the Arctic, including its freshwater ecosystems as warmer temperatures and greater nutrient inputs from a greening landscape are increasing lake and pond productivity. However, nutrients from growing avian nesting colonies can have a much greater effect on aquatic primary production, as undisturbed Arctic catchments have relatively low nutrient inputs. Therefore, a more complete assessment of climate warming’s influence on Arctic aquatic primary production should consider how warming may influence avian population dynamics. This seminar presents results from two paleolimnological studies from the Arctic Archipelago in Canada where we used markers for primary production (chlorophyll a, C/N ratio), avian fecal inputs (δ15N, sterols/stanols), and paleotemperature (branched glycerol dialkyl glycerol tetraethers (brGDGTs)) to examine how these variables have changed over time. The first study analyzed a sediment core from a pond at Cape Vera (Devon Island, Nunavut), that is known to be impacted by seabirds. Our paleotemperature reconstructions based on brGDGTs showed rapid warming over the last 250 years that coincided with a seabird population increase based on avian sedimentary markers. The second study examined primary production, paleoclimate, and avian indicators in Cambridge Bay (Nunavut) lakes, where climate warming was less pronounced. Paleotemperature reconstructions largely indicate more stable thermal conditions in all lakes over the last 150 years, which corroborates instrumental temperature records, whereas increases in avian markers in some lake sediment cores corroborate reports of higher goose populations in some sites. High avian marker sedimentary concentrations also often coincided with elevated primary production markers. These studies provide some of the first brGDGT-based paleotemperature reconstructions from the Arctic Archipelago and showcase their validity, as we were able to correctly discern two distinct local temperature trends. This work also further supports the idea that avian fecal inputs can have a major positive impact on lake primary production in the Arctic.