Carbon dioxide induced freshwater acidification alters anxiety-like behaviour in zebrafish

Abstract

Atmospheric carbon dioxide (CO2) levels are on the rise due to natural and anthropogenic (human generated) causes. As a result, CO2 diffuses into the ocean and is causing a net increase in acidity, termed ocean acidification. Over the last decade many studies have shown that elevated CO2 can alter the behaviour in marine fish, although it is also important to consider that other studies show no effects. There has been much less emphasis on the potential impact of elevated CO2 on freshwater fish. In this study we manipulate CO2 levels in freshwater aquaria for a 4-day period and test the anxiety-like behaviour in zebrafish using a well-validated novel tank diving test and motion-tracking software. Previous studies have shown that in this test drugs that are anxiolytic (anxiety reducing) cause zebrafish to spend more time in the upper zone of the tank whereas anxiogenic (anxiety causing) drugs do the opposite and cause fish to spend more time in the lower zone. We found that an elevation of CO2 levels to 3248 ± 442 μatm caused fish to spend more time in the lower zone of the tank compared to controls (454 ± 49 μatm). There was no difference in distance moved or immobility. These results suggest that with short-term exposures to high levels of CO2 there are significant behavioural changes. Future studies will investigate whether this is reversible and whether fish will adapt to high CO2 levels.

Discipline: Psychology

Faculty Mentor: Dr. Trevor Hamilton