Underwater lake heat waves are a new global phenomenon, leading to mass aquatic deaths and drastic ecosystem changes. According to recent research, climate change is driving this trend. As a consequence, we are now facing longer lasting and stronger marine heatwaves. Consequently, the sensitive thermal balance of lake ecosystems is becoming jeopardized.
Healthy lake ecosystems support biodiversity and productive natural aquatic habitats, which are important for supporting both recreational and commercial fishery species. Yet, as this study shows, underwater heat waves had not historically been studied, as much of the available research has focused mainly on atmospheric or surface temperatures. Scientists are just beginning to understand the effects of these underwater heat waves. Similar to atmospheric and oceanic heat waves, these events can have catastrophic effects on aquatic organisms.
The Impact of Climate Change on Lake Temperatures
Climate change is already responsible for a significant increase in the frequency and intensity of heat waves in recent decades. This trend has severe implications for changing the composition and interactions of lake thermal dynamics. Researchers have noted a disturbing rise in bottom heat waves. Since 1980, the number of these hot bottoms heat waves has increased by over seven additional days per decade. What’s more, their length of stay has lapsed by an average of over two days per decade.
Bottom heat waves occur when warm water accumulates on the bottom of a lake. This results in thermal stratification, limiting habitat suitability for fish and other connectivity-dependent species. On average, fish have to swim almost a full meter more every 10 years to reach the water temperature they prefer. These migrations are physically demanding and often result in higher rates of mortality or disease among the aquatic species.
“These hidden extremes could have serious consequences for lake ecosystems.” – Nature Climate Change
Lakes are critical to global ecosystems and freshwater resources, sustaining life at almost all levels of the food web. For these reasons, figuring out the dynamics behind underwater heat waves is key to protecting these vital ecosystems.
The Growing Frequency of Bottom Heat Waves
The increase in bottom heat waves has serious consequences for marine life. As temperatures rise, aquatic species may struggle to adapt to changing conditions. Of these doubled-up events, these pernicious combined storms are now happening over three days per decade more often.
In thermally stratified lakes, more heat-sensitive species have started moving into deeper waters trying to find shelter from increasing temperatures. This shocking move impacts local ecosystems and changes predator-prey relationships in such a way that fish populations continue to decline.
By the end of this century, many bottom heat waves may persist for months at a time. This combination of factors could produce new temperature extremes never before seen. As climate models evolve, researchers emphasize the importance of representing vertical processes in lakes accurately within global Earth system models.
“When they strike, aquatic species can be left with no place to escape the heat.” – The Conversation
Future Considerations for Aquatic Life
Increasing frequency of underwater heat waves likely has dire impacts on directly affected species. Added to this is the threat they pose to the general health of whole freshwater systems. These types of changes often result in reduced biodiversity and degraded habitats for many aquatic species.
The intensity and pervasiveness of these occurrences have increased. Now more than ever, scientists and policymakers need to act to mitigate a cascade of public health threats. Enhanced monitoring and modeling techniques are necessary to better understand and predict how these heat waves will affect lake environments in the future.
The good news is that the scientific community is intensely studying these phenomena. We need to quickly get their valuable results into on-the-ground conservation practices that shield our freshwater ecosystems. Safeguarding lakes from the damaging consequences of climate change will take commitment from scientists, advocates, and policymakers involved in lake protection and restoration.