Ocean Acidification and Fish Populations

Ocean acidification, due to increased CO2, threatens fish populations.
Experiments show altered larval fish behavior at predicted future CO2 levels (700-850 ppm).
Increased mortality during recruitment due to riskier behavior and impaired predator detection.

At 700 ppm CO2, some larvae are attracted to predator smells; at 850 ppm, predator sensing is impaired.
Elevated CO2 leads to increased activity and riskier behavior in reef habitats.
Mortality from predation increases 5-9 times at elevated CO2 levels.

Atmospheric CO2 could exceed 500 ppm by mid-century, reaching 730-1020 ppm by century's end.
This could lower ocean pH by 0.3-0.4 units, faster than in the past 650,000 years.
Experiments used clownfish (Amphiprion percula) and damselfish (Pomacentrus wardi) larvae.

Control larvae avoided predator odor; those in 700 ppm CO2 showed mixed responses; 850 ppm CO2 caused attraction to predators.
Similar results found in wild-caught damselfish larvae.
Transplanted damselfish exposed to elevated CO2 showed riskier behavior and higher mortality.

Larvae at 850 ppm CO2 had 9-fold higher mortality; 700 ppm, 5-fold higher, compared to controls.
Mortality was due to predation.

CO2 levels predicted for the end of the century could dramatically affect fish larvae behavior and survival.
550 ppm CO2 had no detectable effect on olfactory responses.
Increased activity and reduced risk sensitivity may be due to impaired olfactory ability or general effects on physiological processes.
Adaptation may be possible at 700 ppm CO2 if there's a genetic basis for variation in sensitivity.
Little scope for adaptation at 850 ppm CO2, risking irreversible consequences for marine biodiversity.
Even moderate CO2 increases can significantly impact fish population sustainability.