Siliceous algae response to the “Great Acceleration” of the mid-20th century in Crawford Lake (Ontario, Canada): A potential candidate for the Anthropocene GSSP

Cale Ac Gushulak,R Timothy Patterson,Matthew Marshall,Brendan Llew-Williams,Brian F Cumming,Francine Mg Mccarthy

doi:10.1177/20530196211046036

Cale Ac Gushulak, R Timothy Patterson + Show 4 more

Open Access

https://doi.org/10.1177/20530196211046036

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Abstract

Diatom and chrysophyte assemblages from varved sediments of meromictic Crawford Lake, Ontario record major environmental changes resulting from spatially broadening anthropogenic environmental stressors related to the “Great Acceleration” in the mid-20th century. Biannual assessment of diatom and chrysophyte assemblages over the last ~200 years allowed for rate of change analysis between adjacent samples that increased substantially during the mid-20th century, concurrent with significant generalized additive model trends. Changes in diatom and chrysophyte assemblages were likely driven by multiple anthropogenic stressors including local forestry harvesting, agriculture, and milling activities, acidic deposition from regional industrial processes, and anthropogenic climate warming. Novel siliceous algal assemblages now exist in Crawford Lake, likely related to the complexities of the above mentioned local and regional stressors. The major assemblage changes at the proposed base of the Anthropocene Epoch detected in this study support the laminated sequence from Crawford Lake as a strong potential candidate for the Anthropocene GSSP.

Highlights

The anthropogenic impacts on the environment and climate of our planet cannot be overstated
This study examines siliceous diatom and scaled chrysophyte subfossils collected at a high temporal resolution to examine biological responses to spatially broadening anthropogenic stressors over the last ~200 years of Crawford Lake
High rates of significant changes in diatom and chrysophyte assemblages occurred during the mid20th century of Crawford Lake and reflect spatially broadening anthropogenic impacts and the onset of the Great Acceleration (Steffen et al, 2015)

Summary

Introduction

The anthropogenic impacts on the environment and climate of our planet cannot be overstated. Human activities have been detrimental to freshwater systems, many of which have experienced and/or continue to experience eutrophication (Carpenter and Lathrop, 2008), acidification (Stoddard et al, 1999), changes in nitrogen cycling (Elser et al, 2009), carbon cycling dynamics (Alin and Johnson, 2007), and biodiversity loss (Lake et al, 2000) These changes are encompassed within a rapidly warming climate (Winslow et al, 2017; Woolway and Merchant, 2019; Woolway et al, 2020) which has made the management of freshwater systems extremely difficult. Considering these growing pressures, highly resolved and nuanced understanding of past freshwater system responses to anthropogenic impacts are required to better prepare for future management and conservation challenges

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