Behavioral and Neurological Responses of Southern California Fish Exposed to Ocean Acidification

Anthropogenic CO₂ is changing the oceanic carbonate system, a phenomenon known as Ocean Acidification (OA). Since the Industrial Revolution, the average pH of the global ocean surface has dropped by 0.1 and is predicted to drop another 0.3 to 0.4 by 2100. However, fish in La Jolla, CA frequently experience pH fluctuation of similar magnitude through upwelling events and diurnal variation in kelp forests. To differentiate chronic low-pH effects and oscillating low-pH effects, juvenile Blacksmith (Chromis punctipinnis) were placed in three treatments for 11 days: chronic control conditions (pH ~8.0), chronic OA conditions (pH ~7.73), and oscillating pH treatment (control conditions during daytime, OA conditions during nighttime; 12/12 hour cycle). Three behavioral tests – light/dark preference, shoaling, and novel approach test – were administered and quantified using a software-based motion tracking system. Contrary to a similar study done on juvenile Splitnose Rockfish (Sebastes diploproa), Blacksmith showed no differences in light/dark preference among treatments (N=16). We are currently analyzing results from the other two behavioral tests and quantifying GABA_A­ receptor density in the brains. Given the potential disparity between Blacksmith and Rockfish, further research on the mechanisms that result in species-specific responses would provide greater insights on fish vulnerability to OA.