B018-0015
Winter limnology: how do hydrodynamics and carbon biogeochemistry shape unique ecosystems under ice?

Tuesday, 8 December 2020
Poster
Joachim Jansen1, Sally MacIntyre2, David Barrett3, Yu-Ping (Yo) Chin4, Alicia Cortes5, Alexander Forrest6, Allison R. Hrycik7, Rosemary Martin8, Bailey C. McMeans8, Milla Rautio9 and Robert Schwefel10, (1)Stockholm University, Department of Geological Sciences, Stockholm, Sweden, (2)Univ California Santa Barbara, Marine Science Institute, Santa Barbara, CA, United States, (3)University of Calgary, Biological Sciences, Calgary, AB, Canada, (4)University of Delaware, Civil and Environmental Engineering, Newark, DE, United States, (5)University of California Santa Barbara, Santa Barbara, CA, United States, (6)University of California - Davis, Civil and Environmental Engineering, Davis, CA, United States, (7)University of Vermont, Biology Department, Burlington, VT, United States, (8)University of Toronto, Biology (Mississauga), Toronto, ON, Canada, (9)University of Quebec at Chicoutimi UQAC, Sciences fondamentales, Chicoutimi, QC, Canada, (10)UC Santa Barbara, Earth Research Institute, Santa Barbara, CA, United States
Abstract:
In freshwater systems the carbon cycle acts as an important intermediary between abiotic processes of chemical, thermal and kinetic energy exchange between sediment, water and atmosphere, and ecosystem structure and function. In lakes that are ice-covered in winter, these abiotic-biotic interactions are characterized by strong seasonal shifts. The ice cover limits inputs of light, oxygen and turbulent kinetic energy, and winter has long been perceived as a ‘dormant season’. While today the ice-cover period is increasingly recognized for its unique hydrodynamic and biogeochemical phenomena and ecological relevance, it remains poorly studied compared to the ice-free season.

Knowledge gaps exist where research areas – hydrodynamics, biogeochemistry and biology – intersect. Density-driven currents under ice likely contribute to the expansion of anoxic zones into substrate-rich areas and the accumulation of greenhouse gases below the chemocline. Under-ice currents may impart heat and turbulence to the sediment boundary layer, but it is unknown whether this contributes to enhanced production and exchange of greenhouse gases. And while methanotrophs at the chemocline may mitigate methane emissions in spring, the vitality and richness of winter communities is largely unexplored, as well as the efficiency of transfer to higher trophic levels (zooplankton and fish). Understanding the coupling between state transitions and the reorganization of trophic hierarchies is essential to predicting complex ecosystem responses to climate change. Moreover, under-ice processes cascade into and from the ice-free season, and are therefore relevant to annual cycling of energy and carbon through aquatic food webs.

This short communication follows from the interdisciplinary AGU Chapman conference on winter limnology, held in October 2019 at the Flathead Lake Biological Station in Polson, Montana. We focus on abiotic-biotic interactions in lakes in winter and in spring. First we detail the state of the art of hydrodynamic processes under ice, followed by a brief overview of current developments in under-ice biogeochemistry and ecology. Then we identify extant knowledge gaps. Finally we present (novel) methods available to address outstanding questions.

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