The Conversation - Losing winter ice is changing the Great Lakes food web – here’s how light is shaping life underwater
Low-ice winters are becoming more common across the Great Lakes. NOAA Great Lakes Environmental Research Laboratory
This article from The Conversation reviews the changing dynamics of the Great Lakes food web due to the loss of winter ice, highlighting how light is shaping life underwater. The traditional focus on summer months by scientists has been challenged by emerging research revealing vibrant winter ecosystems under the ice.
As the Great Lakes' winter ice diminishes, hitting record lows in the winter of 2023-24, new studies show that diatoms, tiny photosynthesizing algae, are adapting to survive in dark, ice-free water. These diatoms play a crucial role in maintaining the health of the Great Lakes by cleaning pollutants and forming the base of a food web that supports a significant regional fishery.
Interest in life under the ice surged in 2007 when scientists onboard a Canadian Coast Guard icebreaker observed dark brown water oozing up from Lake Erie, teeming with diatoms. Although winter microbes had been sporadically studied before, it wasn't until recent advancements in molecular biology that scientists could fully understand their behavior. The U.S. Department of Energy's Joint Genome Institute has been sequencing the RNA of microorganisms from Lake Erie to study their winter survival mechanisms and potential adaptations to future climate scenarios.
Typically, diatoms use sunlight to convert carbon dioxide into living material through photosynthesis, contributing to the Great Lakes' summer fisheries. However, in winter, when ice is absent, diatoms are mixed into murky water with limited light penetration. Recent findings suggest that some diatoms use a pigment called rhodopsin to generate energy. Rhodopsins, known for their role in animal vision, help produce ATP, the molecular currency of living cells, enabling diatoms to survive despite the lack of light for photosynthesis.
The shift from photosynthesis to rhodopsin-driven energy production means that diatoms can persist without growing in murky waters, enhancing their survival in ice-free winters. This adaptation may lead to the replacement of traditional diatom species with those equipped with rhodopsins, potentially affecting the entire food web and regional fisheries.
As the climate warms and ice cover decreases, understanding these changes offers a unique opportunity to study the impact on the Great Lakes and similar ecosystems worldwide. This evolving scenario connects to earlier insights shared in an earlier blog post by Canada1Water (C1W) on lake modelling titled “Major North American Lakes Simulations for High Quality Continental Climate Change Projections”- which is a significant component of C1W’s climate and land surface modelling effort. The blog detailed the critical role of major North American lakes in climate projections and the importance of accurate lake models for realistic hydrologic simulations. These efforts are essential for improving our understanding of how climate change will affect regional climates, particularly through mechanisms like ice cover and its impact on moisture and temperature transfer between lakes and the atmosphere. By integrating advanced lake models, C1W aims to enhance the accuracy of climate simulations, thereby informing better management and conservation strategies for freshwater ecosystems.