Thermal Performance in Aquatic Species Under a Changing Climate

Pacific Ocean sunset. (Credit: Mark Taylor via Flickr CC BY-SA 2.0)

Under a rapidly changing climate regime with rising average temperatures, aquatic species are just one of many rungs of the global ecological ladder expected to be negatively impacted. Understanding thermal performance under this changing environment and studying the ability of species to adapt and survive is key to managing natural resources and fisheries.

Since changing temperatures and thermal stress can lead to the loss of key species in waterbodies all over the world, understanding the limits of aquatic species is essential to conserving and protecting fish.

Understanding Thermal Performance

It’s important to understand how thermal changes impact aquatic species. While thermal stress is commonly talked about as it can lead to death or disease in some species, thermal performance is a bit more complicated.

Broadly, thermal performance in aquatic species like fish refers to how well they can tolerate and function under various temperatures, per a 2016 research article. This refers to physiological processes, like growth or energy expenditure (metabolic rate), which can be impacted by temperature spikes or drops.

Changes in thermal performance are often represented by a curve that illustrates how these processes change under different temperature conditions (referred to as thermal performance curves or TPC). TPC plays an important role in determining the resilience and responses of species in a warming climate.

For example, temperature acclimation is an important process that fish undergo when exposed to temperatures near the thresholds of their preferred temperature range. According to an article published in The Conversation, fish acclimate when temperature forces a natural change in physiological processes.

Many researchers have sought to unravel the limits of thermal acclimation and the processes involved in hopes of furthering our understanding of climate response in aquatic species. Though many performance studies are conducted in a laboratory setting, a 2024 study found that the results of lab acclimation treatment are applicable to wild fish.

The Difference and Connection Between Thermal Performance and Thermal Resilience

It’s important to understand that, though similar, thermal performance differs from resilience. Simply put, resilience refers to how well species can withstand and recover from exposure to temperatures outside of their optimal range, while performance relates to the capacity to carry out essential processes at various temperatures.

An aquatic species’ performance can contribute to their overall resilience, as those less capable of adjusting to temperatures outside of their preferred range. And of course, both of these pieces are connected to thermal stress, which triggers both processes.

Conclusion

Ultimately, thermal performance is an important piece of conservation work and critical to future fisheries management. As temperatures are expected to continue to rise, according to Berkeley Earth, understanding the impacts of thermal stress, the intricacies of thermal performance, and the limits of thermal resilience will shape how humanity interacts with aquatic resources.