The Lake Ice Continuum Concept: Influence of Winter Conditions on Energy and Ecosystem Dynamics

Abstract

Millions of lakes worldwide are distributed at latitudes or elevations resulting in the formation of lake ice during winter. Lake ice affects the transfer of energy, heat, light, and material between lakes and their surroundings creating an environment dramatically different from open-water conditions. While this fundamental restructuring leads to distinct gradients in ions, dissolved gases, and nutrients throughout the water column, surprisingly little is known about the resulting effects on ecosystem processes and food webs, highlighting the lack of a general limnological framework that characterizes the structure and function of lakes under a gradient of ice cover. Drawing from the literature and three novel case studies, we present the Lake Ice Continuum Concept (LICC) as a model for understanding how key aspects of the physical, chemical, and ecological structure and function of lakes vary along a continuum of winter climate conditions mediated by ice and snow cover. We examine key differences in energy, redox, and ecological community structure and describe how they vary in response to shifts in physical mixing dynamics and light availability for lakes with ice and snow cover, lakes with clear ice alone, and lakes lacking winter ice altogether. Global change is driving ice covered lakes toward not only warmer annual average temperatures but also reduced, intermittent or no ice cover. The LICC highlights the wide range of responses of lakes to ongoing climate-driven changes in ice cover and serves as a reminder of the need to understand the role of winter in the annual aquatic cycle.Plain Language Summary Millions of lakes worldwide freeze during winter. The formation of lake ice dramatically alters lakes by isolating them from their surrounding landscape and atmosphere. The thickness and optical qualities of ice and snow regulate the amount of solar radiation entering lakes, while shielding them from wind energy. Consequently, lake ice is an important factor regulating physical mixing dynamics within lakes, and structuring vertical thermal and chemical gradients. Although organisms from bacteria to fish have adapted to the winter environment, we lack a comprehensive understanding of how variation in lake ice cover conditions affects fundamental ecosystem processes or food web structure. Here, we combine a synthesis of the current literature with three novel case studies to develop the Lake Ice Continuum Concept as a framework for understanding how key aspects of the physical, chemical, and ecological structure and function of lakes vary along a continuum of energy inputs mediated by winter climate. This framework is useful for understanding changes associated with seasonal ice dynamics and for predicting how lakes may respond to climate change.

Multi-annual comparisons of summer and under-ice phytoplankton communities of a mountain lake

“…In summer, 1% of light reaches a depth of approximately 23 m (Cellamare et al, 2016). Chl-a fluorescence profiles indicate that algae are widely distributed along the water column under ice (Obertegger, 2022) as postulated by the lake ice continuum concept (Cavaliere et al, 2021). Therefore, we were confident that the upper layer reflects the habitat of most phytoplankton, both during summer and under ice.…”

Whither Winter: The Altered Role of Winter for Freshwaters as the Climate Changes

“…Cavaliere et al. (2021) present important hypotheses about the within lake differences under various types of winter regimes, and the significance of these within lake dynamics to ecosystem scale processes in winter and subsequent seasons needs further exploration.…”

“…A key component discussed in the LICC (Cavaliere et al., 2021) are the effects of ice, and snow and ice, on redox conditions. Redox is a master variable (Wetzel, 2001) that strongly influences the types of metabolism that occur in aquatic ecosystems.…”

“…The significance of winter to freshwater processes has long been recognized (Wetzel, 2001) but the underpinnings of the relationships between the physical drivers and biogeochemical dynamics have lacked a conceptual model. In the Lake Ice Continuum Concept (LICC), Cavaliere et al (2021) identify key drivers of variation in winter processes in lakes focusing particularly on the myriad aspects of ice itself and the subsequent role of ice in mediating ecosystem energetics. Ice can be present or absent, it can cover a lake for a long time or a short time, and it can vary from optically transparent columnar ice ("black ice") to more opaque ("white ice"), all with important implications for biological, chemical, and physical processes.…”

“…These metabolic differences at the bottom of the food web impact higher trophic levels but our understanding of these connections are understudied. Cavaliere et al (2021) present important hypotheses about the within lake differences under various types of winter regimes, and the significance of these within lake dynamics to ecosystem scale processes in winter and subsequent seasons needs further exploration.…”