How can Ocean Acidification affect the Behaviour of Marine Species?

The increase in carbon dioxide (CO2) in the atmosphere is causing global warming and ocean acidification. This is the result of a decrease in pH and an increase in acidity caused by carbon dioxide dissolving in water, thus changing its chemical balance. Through the ODORACID project, Zélia Velez, a researcher at the Centre of Marine Sciences (CCMAR) at the University of Algarve, is trying to determine how ocean acidification influences the neuronal changes that lead to behavioural changes in fish, in order to be able to predict the environmental impact of these changes and try to develop strategies to reduce them.

In recent years, an alarming increase of CO2 has been detected, much of which dissolves in the ocean, leading to behavioural changes in many fish species. There are serious concerns about the impact this will have on biodiversity and marine ecosystems.

This project aims to assess the effects of ocean acidification on the perception of various odours by the olfactory epithelium, and the further processing of sensory information at different levels of the central nervous system.

It also seeks to assess the ability of fish to detect changes in the concentration of ions in the water, more specifically those causing ocean acidification. The researcher goes on to explain that, “Some species of coral reef fish seem to be attracted by the smell of predators and repelled by the smell of food, when exposed to the conditions predicted for the end of this century. It is easy to understand how such behavioural changes could compromise the survival of these species.”

The main aim of this project is to understand the changes that take place in fish brains that then lead to these behavioural changes, using a species that is highly important in aquaculture, both in ecological and economic terms, as an experimental model the Senegalese sole (Solea senegalensis). The results gathered, however, can be applied to many other species.

Studies related to olfaction have been limited to studying behavioural changes in coral reef fish exposed to high amounts of CO2. No studies have yet been conducted with coastal species and/or those of economic importance. Although evidence does exist that the atmospheric concentrations of CO2 predicted for the end of this century will have substantial effects on behaviours related to the olfactory perception of coral reef fish, nothing is known about the cellular mechanisms involved in these changes. Ocean acidification is expected to cause significant changes in the ionic content of seawater, and the ability of fish to adapt to such changes clearly depends on their ability to detect them.

What is known is that ocean warming and acidification is resulting in a loss of biodiversity and changing the distribution of these species. The behavioural changes noted could compromise the survival of many species of fish and the collapse of the marine ecosystem as we know it.

“By understanding the physiological consequences of ocean acidification, we are able to assess different species’ ability to adapt to these changes, and detect those most vulnerable to this phenomenon,” explains Zélia Velez.

The researcher believes that, “In the future, this type of knowledge may help devise strategies to minimise the impact of these changes, both on an environmental level and for aquaculture.”

 Encompassed under Goal 14, “Life Below Water”, this project focuses on taking very concrete action, aiming to “minimise and face the impacts of ocean acidification, including

Zélia Velez has a Bachelor’s Degree in Biology, a PhD in Neurophysiology and Analytical Chemistry and is a researcher at the Centre of Marine Sciences (CCMAR) of the University of Algarve.