Peri-urban lakes offer many valued ecosystem services, but their vulnerability to climate change and anthropogenic disturbances increases with increasing human populations the effects and interactions of multiple stressors on lakes can lead to unexpected outcomes, affecting societal and ecological values, it is necessary to evaluate ecosystem trajectories and respective drivers in peri-urban lakes. Better management practices could thus be applied to preserve ecosystem services of peri-urban lakes. We conducted a multi-proxy paleolimnological study on Cultus Lake, British Columbia, a Canadian peri-urban lake experiencing cultural eutrophication, to reconstruct a comprehensive ecological trajectory of the lake over the past ~ 200 years. We also integrated historical data as well as historical archival information to identify the potential drivers of the changes. We identified ca. 1800–1900 CE as a reference period, reflected in muted variations across most paleo-indicators. Minor increases in sedimentary δ15N ca. 1880–1940 CE coincided with the onset of anthropogenic modifications to the Cultus Lake watershed. Signs of early eutrophication were evident by ca. 1940 CE, as indicated by increases in all sedimentary pigments. By ca. 1970–1990 CE, elevated concentrations of sedimentary cyanobacterial pigments and changes in diatom species assemblages highlighted the potential interactive effects of multiple stressors, including cultural eutrophication, climate warming and declines in the endangered Cultus Lake sockeye salmon population. Recent (ca. 1990–2008 CE) declines in sedimentary pigments and increases in cladoceran fluxes suggested an increase in top-down control of the lake food web. From the collection of changes observed in the past ~ 200 years in our study, it is clear that Cultus Lake and its associated ecosystem services would benefit from abatement of nutrient loadings from terrestrial and atmospheric sources. Our study emphasizes the complexity and interactivity of drivers in peri-urban lake ecosystems and the necessity of long-term perspectives to contextualize modern ecological conditions to inform lake and watershed management.
Bibliographical noteFunding Information:
We thank Andrew Grant and Steve McDonald of DFO for their assistance in the core collection. We also thank Kelly Malange, Garrett Lindin and Lucas Pon for the sediment traps deployment. Thanks to Alexandre Baud for helping with producing figures of the paper. Thank you to Tristan Evans and Laurie Benton for providing help with the historical research at the Chilliwack Museum and Archives. Dr. Zoraida Quinones-Rivera assisted with fossil pigment analysis. This research was supported by an NSERC postgraduate scholarship and an award from CREATE-Ecolac program through the Groupe de Recherche Interuniversitaire en Limnologie et Environnement Aquatique (GRIL) to JG. Financial support was also provided by Gordon and Betty Moore Foundation to DES, PRL, IGE, BF and Canada Research Chairs to PRL and IGE. We acknowledge Fisheries and Oceans Canada for their financial support. We are also thankful for the constructive comments of the two anonymous reviewers.
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- Anthropogenic drivers
- Climate change
- Lake ecosystem
- Multiple indicators