Study links altered brain chemistry, behavioral impairments in fish exposed to elevated CO2
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Jodie L. Rummer
Study Links Altered Brain Chemistry, Behavioral Impairments in Fish Exposed to Elevated CO2 Research team studied damselfish behavior physiology under ocean acidification conditions predicted for year 2300 MIAMI–In a first-of-its-kind study, researchers from the University of Miami (UM) Rosenstiel School of Marine Atmospheric Science the ARC Centre of Excellence for Coral Reef Studies at James Cook University showed that increased carbon dioxide concentrations alters brain chemistry that may lead to neurological impairment in some fish.
Understanding the impacts of increased carbon dioxide levels in the ocean, which causes the ocean to become more acidic, allows scientists to better predict how fish will be impacted by future ocean acidification conditions.
“Coral reef fish, which play a vital role in coral reef ecosystems, are already under threat from multiple human natural stressors,” said lead author of the study Rachael Heuer, a UM Rosenstiel School alumna which conducted the study as part of her Ph.D. work. “By specifically understanding how brain blood chemistry are linked to behavioral disruptions during CO2 exposure, we can better understnot only ‘what’ may happen during future ocean acidification scenarios, but ‘why’ it happens.”
In this study, the researchers designed conducted a novel experiment to directly measure behavioral impairment brain chemistry of the Spiny damselfish, (Acanthochromis polyacanthus) a fish commonly found on coral reefs in the western Pacific Ocean.
During a three-week period, the scientists collected spiny damselfish from reefs off Lizard Isllocated on Australia’s Great Barrier Reef. The fish were separated into two groups–those exposed to ordinary CO2 “control” conditions those exposed to elevated CO2 levels that are predicted to occur in the near future, but have already been observed in many coastal upwelling areas throughout the world. Following the exposure, the fish were subjected to a behavioral test, brain blood chemistry were measured.
The unique behavioral test, employed a two-choice flume system, where fish were given the choice between control seawater or water containing a chemical alarm cue, which they typically avoid since it represents the smell associated with an injured fish of its own species.
The researchers found that the damselfish exposed to elevated carbon dioxide levels were spending significantly more time near the chemical alarm cue than the control fish, a behavior that would be considered abnormal. The measurements of brain blood chemistry provided further evidence that elevated CO2 caused the altered behavior of the fish.
“For the first time, physiological measurements showing altered chemistry in brain blood have been directly linked to altered behavior in a coral reef fish,” said UM Rosenstiel School Maytag Professor of Ichthyology lead of the RECOVER Project Martin Grosell, the senior author of the study. “Our findings support the idea that fish effectively prevent acidification of internal body fluids tissues, but that these adjustments lead to downstream effects including impairment of neurological function.”
“If coral reef fish do not acclimate or adapt as oceans continue to acidify, many will likely experience impaired behavior that could ultimately lead to increased predation risk to negative impacts on population structure ecosystem function,” said Heuer, currently a postdoctoral researcher at the University of North Texas. “This research supports the growing number of studies indicating that carbon dioxide can drastically alter fish behavior, with the added benefit of providing accurate measurements to support existing hypotheses on why these impairments are occurring.”