Rising Ocean Acidity Could Mean Some Very Anxious Fish [VIDEOs]

Rising ocean acidity could lead to some very anxious fish, according to a study published in the journal Proceedings of the Royal Society B.

Researchers from the Scripps Institution of Oceanography at UC San Diego and MacEwan University in Edmonton, Canada used a camera-based tracking software system to compare a control group of juvenile rockfish, a key commercial species in California, to one exposed to those acidity levels projected to occur by the end of the century.

They then measured each group's preference when it came to swimming in light or dark areas of a testing tank -- a known fish anxiety test.

The results showed that while the control fish swam continuously back and forth between the light and dark parts of the tank, those exposed to acidified ocean conditions holed up in the dark area of the tank, their stress levels remaining high up to almost two weeks in normal conditions.

The reason has to do with changes in the fish's GABAa, or neural gamma-aminobutyric acid type A, receptors, which are also implicated in human anxiety levels. WHen exposed to acidified water, the fish underwent changes in the concentrations of ions in their blood that then reversed the flux of ions through the GABAa receptors, which then went on to alter the fish's behavior.

"These results are novel and thought-provoking because they reveal a potential negative effect of ocean acidification on fish behavior that can possibly affect normal population dynamics and maybe even affect fisheries," said Martín Tresguerres, a Scripps marine biologist and study co-author.

The juvenile rockfish is of particular concern to scientists due to the fact that they occupy areas such as kelp forests, which offer a wide range of lighting and shading conditions.

"If the behavior that we observed in the lab applies to the wild during ocean acidification conditions, it could mean that juvenile rockfish may spend more time in the shaded areas instead of exploring around," Tresguerres said. "This would have negative implications due to reduced time foraging for food, or alterations in dispersal behavior, among others."