The Impact of Climate Change on Winter Diatom Blooms in Lake Erie

As spring weather brings favorable conditions for flowers and plant life to bloom, a fascinating discovery in Lake Erie back in 2012 shed light on the unexpected abundance of diatoms beneath the ice cover. These microscopic, photosynthetic algae were thriving in the icy waters, thanks to a symbiotic relationship with heterotrophic bacteria that formed tiny ice crystals. These “diatom ice cubes” floated to the lake’s surface, allowing them to absorb the light needed for photosynthesis during the winter months.

However, the warming global temperatures have led to a significant decline in ice cover across the Great Lakes, including Lake Erie. In recent years, Lake Erie has experienced nearly ice-free winters, leaving diatoms in murky, light-deprived waters. This rapid environmental change has posed a threat to the adaptations that once benefited these winter diatoms, leaving them struggling to survive.

Research and Findings

Microbiologists, including Brittany Zepernick, have been studying the evolving situation of the diatoms in Lake Erie. With the help of the US and Canadian Coast Guard, they have sampled both ice-covered and ice-free winter waters to understand how these diatoms are responding to the changing environmental conditions. Their recent publication in The ISME Journal revealed that two main diatom genera, Aulacoseira islandica and Stephanodiscus spp., dominate the winter blooms.

The study found that the abundance of Stephanodiscus spp. was significantly lower in ice-free water compared to ice-covered water. Similarly, Aulacoseira islandica showed a 50 percent decrease in abundance in ice-free water columns. With ice cover across the Great Lakes at record lows, researchers anticipate that this trend will continue in future winters and have lasting effects on Lake Erie’s ecosystem.

Role of Diatoms in Aquatic Ecosystems

Diatoms play a crucial role in global biogeochemical cycles and are essential for maintaining the health of freshwater systems. They contribute to carbon sequestration, oxygen production, and overall aquatic ecosystem stability. The changes in winter-spring diatom communities in Lake Erie and other lakes worldwide will lead to significant biological and biogeochemical changes.

Despite the challenges posed by climate change, there is potential for diatoms to adapt to these changing conditions. Zepernick’s research suggests that diatoms may form clusters with adhesive proteins to “raft” to the surface of the water through underwater waves. Additionally, diatoms could increase their use of proton-pumping rhodopins as an alternative to traditional photosynthesis, offering them a survival advantage in a rapidly changing climate.

The impact of climate change on winter diatom blooms in Lake Erie highlights the urgency of understanding and protecting these vital components of our aquatic ecosystems. By studying how diatoms respond to environmental changes, researchers can gain valuable insights into their adaptive mechanisms and the potential implications for the global environment.