Weather and human activity impact lake extremophiles

The Great Salt Lake, located in Utah, USA, has become a focal point for scientific research due to its unique ecological dynamics and the influence of both human activity and weather patterns on its microbial life. The lake is divided by a 20-mile (32-kilometer) causeway into a highly saline north arm and a less saline south arm, each home to distinct communities of extremophiles, organisms capable of surviving in extreme conditions. A gap in the causeway, intended to regulate salinity, has allowed scientists to observe how these microscopic life forms respond to environmental changes. In the fall of 2022, the lake reached a historic low due to several years of severe drought. This period was followed by a dramatic rise in water levels as mountain snowmelt flooded the area. To manage the fluctuating water levels and maintain the desired salinity in the south arm, government agencies constructed a berm, a raised structure, to control the flow of water through the channel. The height of this berm could be adjusted, offering a tool to mitigate the effects of extreme weather and human interventions. Researchers from Duke University, including Dr. Amy Schmid and Dr. Alex Phillips, conducted seasonal sampling over the course of a year, marking the first comprehensive study of microbial communities in the Great Salt Lake throughout all seasons. Their findings, published in Applied and Environmental Microbiology, reveal that changes in water flow, whether caused by weather or human management, significantly alter the distribution and interaction of microbial species. Hydrodynamic modeling confirmed that these changes extend beyond the immediate vicinity of the breach, influencing microbial communities even in areas distant from the causeway. During the 2022 drought, microbial diversity in the north arm remained relatively stable, while the south arm saw a notable decline. This shift is attributed to altered water flow patterns around the underwater berm. Dr. Phillips noted that the movement of extreme hypersaline microbes from the north arm into the less dense waters of the south arm appears unidirectional, suggesting a possible imbalance in the ecosystem’s natural processes. Future studies will explore the underlying reasons for these directional movements. The Great Salt Lake is a terminal lake, meaning it receives water primarily from rivers and loses it solely through evaporation. Its size and location make it particularly vulnerable to environmental pressures. Over decades, river redirection for agriculture and ongoing drought have pushed the lake toward increasingly low water levels. The two arms of the lake now represent different phases of desiccation, with the north arm possibly approaching a critical threshold where it could transition into a fully landlocked environment. Understanding how microbial communities react to stressors such as human intervention and climate variability is crucial for developing strategies to preserve the lake’s ecosystem. Dr. Schmid emphasized that identifying the tipping point for the south arm could provide insights into preventing further degradation. The microbial populations form the foundation of the lake’s food web, feeding invertebrates like brine shrimp and flies, which support millions of migratory birds that rely on the lake annually. Dr. Bonnie Baxter, a molecular biologist at the Great Salt Lake Institute, highlighted the importance of the study in understanding how the berm influences microbial interactions. She noted that the baseline data gathered thus far have already informed conservation efforts and sparked discussions among state officials regarding the broader implications of altering the lake’s natural channels. The research underscores the delicate balance between human activity and natural systems, offering valuable knowledge that could guide future policies aimed at protecting one of North America’s most unique ecosystems.