Under-ice and open-water ecosystem metabolism in temperate water bodies

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Authors

Rebecca Lee North, Jason Venkiteswaran , Greg Silsbe, Joel Harrison, Jeff Hudson, Ralph EH Smith, Peter Dillon, Patricia Pernica, Stephanie Guildford, Michael Kehoe, Helen Baulch

Abstract

Winter, historically a largely un-monitored season, is influential and changing. There is evidence of the importance of under-ice phytoplankton in temperate lakes, but it is currently unknown if high winter phytoplankton biomass translates to high productivity and what influence it has on year-round lake metabolism. Winters are getting shorter, but our ability to forecast change is hindered by our limited understanding of under-ice processes. Here, we compare under-ice and open-water rates of areal gross production (AGP) and areal respiration (AR) from 3 Canadian reservoirs and one large lake using oxygen (O2) δ18O-O2 models and fluorometry. During the open-water season, AGP was 5× greater than under-ice rates, with AR rates 8× higher than measured during winter. Open-water samples indicated autotrophy (P:R= 1.10) with heterotrophy dominant under ice (P:R= 0.67). Consistent with current assumptions, the cold under-ice environment is associated with low primary productivity. Our results challenge the assumption that mean water column irradiance is lowest during the winter in dimictic water bodies; we find similar light conditions during the open-water season. Winter mean light is regulated by snow thickness; upon manual snow removal, we observe a 67 % increase in under-ice mean water column irradiance. The first-ever under-ice application of the δ18O2-method indicated that AGP responded to improvements in light. This study reveals further insights into the importance of under-ice metabolism on year-round processes in a changing climate. 

DOI

https://doi.org/10.31223/X5RQ1V

Subjects

Environmental Sciences

Keywords

production, respiration, autotrophic, heterotrophic, under-ice, Lake Simcoe, Lake Diefenbaker, winter limnology, respiration, autotrophic, heterotrophic, under-ice, Lake Simcoe, Lake Diefenbaker, Winter limnology

Dates

Published: 2023-02-01 15:57

Last Updated: 2024-06-04 10:12

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License

CC BY Attribution 4.0 International

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