Study: Rising oceanic acidity could disorient fish

Posted by Samantha Rose Hunt

Chicago (IL) - With global carbon levels reportedly on the rise, it is possible that ocean life could potentially be in danger. As the carbon levels rise, ocean acid levels also rise giving fish a biologically difficult time living in the seas.





When fish grow and develop in waters with high acidity they lose certain senses. For example, a study found that baby clownfish rely on their sense of smell to search for a home. When exposed to high acidity levels, they no longer responded to smells which should have been familiar.



Marine biologists Phillip Munday and Kjell Doving conducted a study which was published in the Proceedings of the National Academy of Scientists. It was found that if acidification of the ocean continues without any slow down, then the sustainability of marine wildlife populations will be significantly reduced because the fish will be growing and developing with reduced sensory abilities.



The study was conducted due to the reportedly rapid rise in acidity in of Earth's oceans.



The process works like this: Seawater absorbs carbon dioxide, when this occurs the proportion of hydrogen ions fall. Since pre-industrial times the pH of the ocean has fallen by .1, and it's predicted that it will "more than likely fall" by another .3 to .4 within the next 100 years. These numbers probably sound small, but they represent an unprecedented change - not only in degree but also pace when compared to the past 650,000 years. Marine life might not be capable of survival.



Typically research on acidification and the environment has focused on the vulnerability of shellfish, corals, and crustaceans whose shells become not only weakened but also dissolve within the confines of acidic waters. The latest findings prove that fish could also be directly and significantly affected.



When the study was conducted, Doving's and Munday's team raised young clownfish in waters with a pH of 8.15, which is the equivalent to the typical oceanic pH. The fish were then placed in a plastic chute and separated into two channels.



The researchers put different scents within the tubes. The scents consisted of oil from a tree which clownfish are typically attracted to, oil from a swamp tree which the fish would generally avoid, secretions of anemones (which are a habitat clownfish prefer) and secretions from their own parents (which fish typically avoid).



Under average pH conditions the clownfish behaved as they were expected to. When researchers placed the fish within water that had an expected end-of-century pH of 7.8, the fish were drawn to scents which they had typically ignored. When placed in a pH of 7.6 the fish no longer responded to scents at all.



It has not yet been determined if these findings could be applied to not only clownfish, but also to other saltwater fish species as well. The researchers did note however, that many species utilize olfactory cues when making important life decisions. It is also hopeful and possible that fish might find a way to adapt, however researchers are not optimistic for this outcome.