Publication Abstract

Anthropogenic enrichment of atmospheric CO₂ concentration has lead to a reduction in surface ocean pH with further decreases predicted. Despite the importance of fishes to supporting ecosystem function and human food security, little is known about the effects of ocean acidification on reproduction and early development in fish. These effects may be profound as pH plays a key role in regulating reproductive processes, gametes and early developmental stages are often directly exposed to changes in water chemistry, and early developmental stages of fish are most sensitive to toxicants. We examined the effects of CO₂ enrichment on fertilisation and embryological development of the cod, Gadus morhua, with experiments at ambient (380), 970 and 4000 ppm CO₂. Relative fertilisation success in the 970 and 4000 ppm trials declined by 3.5 and 40% respectively. At 4000 ppm no embryos survived to hatch. Average hatch rate in the air control and 970 ppm trials was 19 and 42% respectively. This indicates that fertilisation and early development in cod may be robust to direct effects of acidification under reasonable emissions scenarios although cod populations could be threatened under more extreme emissions scenarios.