Fish are losing their olfactory ability due to ocean acidification caused by increased carbon dioxide in the atmosphere. A team of researchers that includes members of the Center for Marine Sciences (CCMAR) has just published a study in the journal Nature Climate Change which reinforces the great concern of the scientific community in relation to ocean acidification and its impact on the species that inhabit it.
When carbon dioxide reacts with seawater, carbonic acid forms, which makes the water more acidic. Researchers say carbon dioxide has increased by 43 percent in the ocean since the industrial revolution, and is expected to double from current levels by the end of this century.
Fish use their sense of smell to find food, look for safe habitats, avoid predators, recognize each other and even find places to breed.
Experts warn that any reduction in olfactory ability can compromise some of the essential functions of fish and even their own survival.
The new study, now published in the journal Nature Climate Change, shows that commercially important fish species will be affected by increased atmospheric levels of carbon dioxide, leaving them more vulnerable as it affects their ability to detect odors.
The study was led by Cosima Posteus of the University of Exeter, who highlights its innovative aspects, saying it is the first study to analyze the impact of ocean carbon dioxide directly on the olfactory system of fish.
Scientists began by comparing the behavior of juvenile sea bass at levels of carbon dioxide currently found in the ocean with levels predicted by the end of this century.
Sea bass swam less in more acidic waters and were also less prepared to respond to predators. These fish were also less active, indicating some anxiety.
A large part of this work was carried out on the premises of the Centro de Ciências do Mar (CCMAR) in the Algarve, where the ability of sea bass to detect different odors was tested, using the recording of activity in the nervous system when sea bass were exposed to different conditions. acidity and carbon dioxide levels in water.
The olfactory sensitivity of sea bass was greatly reduced, to about 50% of normal, when carbon dioxide levels approached those estimated for the end of the century.
Their ability to detect and respond to odors associated with food or threatening situations were more affected than the detection of other odors without vital functions.
The researcher in charge believes that this is due to the fact that acidified water changes the way in which olfactory molecules bind to olfactory receptors, reducing their sensitivity and ability to distinguish important stimuli.
This could be one more consequence of the increase in the levels of carbon dioxide in the atmosphere that threatens aquatic ecosystems and consequently our food.
Scientists have also studied how the high carbon dioxide content and acidification of water affect the activity of genes in the nostrils and brain of sea bass and found evidence of alterations in genes involved in odor recognition and processing and information.
Although this study focused on sea bass, the fact that olfactory processes are common to many other aquatic fish species indicates that many species could be affected.
The person responsible for the study says that the fish examined, even when they felt their sense of smell reduced, showed no indications of having compensatory capacity.
In addition, in addition to olfactory problems, possible alterations in the function of the nervous system associated with them also arise.
Scientists thus pose the question of the resilience of fish under these conditions, whether they will manage to survive these adversities, whether they will be able to adapt, and in what time frame, as they will have to face a significant impact with the predicted increase in the levels of carbon dioxide. carbon.
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