Calibration and Application of Biomarkers in Sediment to Track Paleoclimate and Large-scale Migratory Animal Population Dynamics

Abstract

The primary objective of this thesis was to develop and apply lipid biomarker and isotope-based methods for reconstructing large-scale migratory animal populations and climatic histories in western North America from lake sediments. Specifically, this thesis aimed to (1) develop sterol and stanol biomarkers as quantitative proxies for Sockeye salmon escapement alongside the traditional lake sediment proxies (δ¹⁵N); (2) utilize sterols, stanols, and δ¹⁵N to track changes on large cormorant colonies on Lake Ontario Islands; (3) develop and validate lake-specific branched glycerol dialkyl glycerol tetraether (brGDGT) calibrations to refine paleotemperature estimates for Cultus Lake, British Columbia (BC); and (4) to reconstruct past temperatures using lake-specific brGDGT calibrations and assess their relationship with large-scale climate oscillations (Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO)). I will then integrate these results with salmon escapement records and sedimentary δ¹⁵N dynamics from dated Cultus Lake sediment cores to evaluate how climate variability has influenced long-term salmon production. In Chapter Two, I applied sterol, stanols, and δ¹⁵N markers in sediment to track a sharp rise in cormorant population on Lake Ontario Islands. In Chapter Three, I developed novel sterol indices that strongly correlated with historical Sockeye salmon returns record in Alaska and BC, providing robust tools for reconstructing long-term Sockeye salmon population dynamics. In Chapter Four, I calibrated brGDGT distributions in soils, sediments, and water column samples from Cultus Lake, BC, establishing the first lake-specific temperature transfer functions in coastal BC. Chapter Five integrated lake-specific brGDGT-based temperature reconstructions with isotope (δ¹⁵N) based salmon proxies, revealing linkages between large-scale climate systems such as PDO, and ENSO variability, regional climate forcing, and salmon escapement trends over the past century. Together, these chapters demonstrated that lipid biomarkers and isotopes preserved in sediments provide high-resolution ecological and climatic archives, offering tools to disentangle the effects of climate oscillations and anthropogenic pressures on migratory animal populations and freshwater ecosystems. The overall conclusions of this thesis are: (1) sterol and stanol biomarkers provide reliable, independent proxies of Sockeye salmon escapement and can be used alongside traditional salmon proxies; (2) sterol, stanols, and δ¹⁵N signatures enabled the reconstruction of cormorant population and their ecosystem impacts from pond sediments; (3) lake-specific brGDGT calibrations significantly improved the accuracy and ecological relevance of paleotemperature estimates at Cultus lake; and (4) integrating biomarkers, isotopes, and climate indices strengthens our ability to assess the coupled dynamics of climate variability, nutrient cycling, and salmon populations across timescales.