Nova Scotia, Canada, became the backdrop for a groundbreaking experiment during the past summer, offering a unique solution to alleviate the impact of rising water temperatures on fish in the Wrights River. Civil engineer Kathryn Smith unveiled this pioneering concept at the Geological Society of America meeting on October 17. While still in its experimental stage, this approach holds significant promise for the conservation of cold-water species struggling with the mounting challenge of river warming linked to climate change.
Elevated water temperatures are known to put fish at risk, leading to stress and, in severe cases, fatalities. In river ecosystems, cold-water species like Atlantic salmon often seek refuge in cooler zones, typically associated with groundwater springs or cooler tributaries.
Despite dedicated efforts to protect and enhance these naturally occurring refuges, Smith, representing Dalhousie University in Halifax, Canada, highlighted the limited focus on creating artificial cold-water habitats.
In response, Smith and her team introduced a pioneering approach, whereby groundwater with a temperature of approximately 9°C (about 48°F) from a nearby well was introduced into the river. This endeavor resulted in the creation of an artificial cold-water plume, which could be as much as 20 degrees Celsius cooler than the surrounding water.
This created plume acted as a magnet, attracting a diverse array of fish in various life stages and of different species, including Atlantic salmon and brown trout. Notably, the majority of inhabitants were alevins, young fish still reliant on yolk sacs, who were consistently present within the plume throughout the testing. As the region experienced a heatwave, causing water temperatures to rise to about 30°C, more mature fish also sought refuge within the plume.
In addition to this approach, the team also explored a pump-free alternative, redirecting river water into an underground trench. This method allowed the water to cool before re-entering the river. Although this approach led to a reduction in temperature of only a few degrees Celsius, fish were observed using this passively cooled flow throughout the summer.
Further research is required to ascertain the number of such sites needed to make a substantial impact on fish populations and to establish a cost-effective means of maintaining them. John Ackerman, a consulting engineer from Hazleton, Pennsylvania, who was not involved in the study, emphasized the significance of this research, acknowledging that it demonstrates the feasibility of these solutions and confirming that "the concept is sound."