NORTH PACIFIC CLIMATE VARIABILITY INFERRED FROM A 600-YEAR SEDIMENTARY LIPID BIOMARKER RECORD AND ECOSYSTEM RESPONSES IN CULTUS LAKE, BRITISH COLUMBIA, CANADA

Branched glycerol dialkyl glycerol tetraethers (brGDGT) are bacterial membrane lipids widely used as indicators of past temperature. We developed a lake-specific brGDGT temperature calibration for Cultus Lake, British Columbia, using seasonally resolved suspended particulate matter and in situ measurements. Among all compounds, brGDGT Ib showed the strongest thermal sensitivity, and multivariate modelling identified two-predictor regression (including Cal1(brGDGT Ib and IIa') and Cal2 (brGDGT Ib and IIb')) that substantially improved temperature prediction compared with the commonly used MBT'5Me index and existing regional or global models. Applying Cal2 to a ~600-year sediment record (since ~1400 CE) reconstructs pronounced multi-centennial temperature variability consistent with independent regional proxies, including tree-ring indices and Na⁺ from Mt. Logan ice core records. This multi-centennial temperature variability tracks sedimentary δ¹⁵N, a proxy for Pacific salmon escapement, until the late nineteenth century, when a sustained δ¹⁵N enrichment reflected increasing anthropogenic nitrogen loading and a decoupling from Pacific salmon escapement dynamics. These results demonstrated that lake-specific brGDGT calibrations capture both long-term regional climate variability and decadal Pacific forcing while highlighting the growing influence of anthropogenic nutrient inputs on modern lake biogeochemistry.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Daniel Dagodzo, University of Ottawa (ddago070@uottawa.ca)

Authors:

Daniel Dagodzo, University of Ottawa  (ddago070@uottawa.ca)

Adriana Raats, University of Ottawa  (araat027@uottawa.ca)

Raphael Siegel, University of Ottawa  (rsieg075@uottawa.ca)

David Eickmeyer, University of Ottawa  (deickmey@uottawa.ca)

Linda Kimpe, University of Ottawa  (linda.kimpe@uottawa.ca)

Daniel Selbie, Fisheries and Oceans Canada (DFO) Science Branch, the Cultus Lake Salmon Research Laboratory (CLSRL), Cultus Lake, BC.  (daniel.selbie@dfo-mpo.gc.ca)

Jules Blais, University of Ottawa  (jules.blais@uottawa.ca)