Pink salmon affected by freshwater acidification

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Researchers have suggested that though there have been multiple studies about the effects of ocean acidification on marine species, there have been far fewer studies to understand the consequences of freshwater acidification on marine species.

In a new study that targets this relatively unchartered topic, researchers have found that pink salmon that begin life in freshwater with high concentrations of carbon dioxide, which causes acidification, are smaller and may be less likely to survive.

University of British Columbia professor Colin Brauner says that 40 per cent of all fish are freshwater and there is a need to think beyond ocean acidification and look at how carbon dioxide is affecting freshwater species.

The professor said that in their study that examines the link between increased carbon dioxide concentrations and its effect on marine species, they found that freshwater acidification affects pink salmon and may impact their ability to survive and ultimately return to their freshwater spawning grounds.

The study, which is published in Nature Climate Change and is one of the first that examines the link, examined how baby salmon respond to fresh and ocean water with the levels of carbon dioxide expected 100 years in the future. Researchers monitored the salmon for ten weeks, from before they hatched to after the time they would migrate to ocean water.

Researchers found that these salmon were smaller and their ability to smell the water was reduced, which is important for returning to their spawning ground at the end of the life cycle and for sensing danger and responding to it. Once the salmon reached the age when they would typically begin their seaward migration, researchers found they were less able to use oxygen to exercise, which is likely to hurt their ability to find food, evade predators, and migrate.

“The increase in carbon dioxide in water is actually quite small from a chemistry perspective so we didn’t expect to see so many effects,” said Michelle Ou, a former master’s student who is the lead author of the study. “The growth, physiology and behavior of these developing pink salmon are very much influenced by these small changes.”

Brauner and Ou worked with pink salmon for their study as it’s the most abundant salmon species on the West Coast and of high economic and ecological importance. Pink salmon enter the ocean at the smallest size of all Pacific salmon and consequently may be the most sensitive to aquatic acidification. Further research is needed to examine the long-term impacts of freshwater and ocean acidification on all salmon species.