CO2-induced ocean acidification increases anxiety in Rockfish via alteration of GABAA receptor functioning

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: Hamilton, Trevor James, Holcombe, Adam, Tresguerres, Martin
• Format: Text
• Language: English
• Published: The Royal Society 2014
• Subjects: Research Articles; Ocean acidification
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3866405; http://www.ncbi.nlm.nih.gov/pubmed/24285203; https://doi.org/10.1098/rspb.2013.2509

The average surface pH of the ocean is dropping at a rapid rate due to the dissolution of anthropogenic CO2, raising concerns for marine life. Additionally, some coastal areas periodically experience upwelling of CO2-enriched water with reduced pH. Previous research has demonstrated ocean acidification (OA)-induced changes in behavioural and sensory systems including olfaction, which is due to altered function of neural gamma-aminobutyric acid type A (GABAA) receptors. Here, we used a camera-based tracking software system to examine whether OA-dependent changes in GABAA receptors affect anxiety in juvenile Californian rockfish (Sebastes diploproa). Anxiety was estimated using behavioural tests that measure light/dark preference (scototaxis) and proximity to an object. After one week in OA conditions projected for the next century in the California shore (1125 ± 100 µatm, pH 7.75), anxiety was significantly increased relative to controls (483 ± 40 µatm CO2, pH 8.1). The GABAA-receptor agonist muscimol, but not the antagonist gabazine, caused a significant increase in anxiety consistent with altered Cl− flux in OA-exposed fish. OA-exposed fish remained more anxious even after 7 days back in control seawater; however, they resumed their normal behaviour by day 12. These results show that OA could severely alter rockfish behaviour; however, this effect is reversible.