Scientists: Ocean acidification due to climate change could weaken salmon sperm - Ocean Acidification Threatens Salmon and Sea Urchin Reproduction, Study Finds

Rising ocean acidification could threaten the reproduction of salmon and sea urchins, according to new research. The study reveals how changes in seawater chemistry disrupt a key process that controls sperm movement in these species. Scientists warn that global warming may worsen the problem, putting marine life at risk.

Both salmon and sea urchins rely on external fertilisation during mass spawning. Their sperm depend on a signalling molecule called cAMP to stay active. This molecule is produced by an enzyme that responds to lower pH levels in seawater.

Researchers first discovered this pH-sensitive mechanism in sea urchins before confirming it in salmon. In mammals, cAMP production is instead triggered by high bicarbonate levels, not pH. But in these marine species, alkaline conditions slow down the enzyme, reducing sperm motility.

If sperm cannot swim properly, fertilisation fails. Without cAMP, they would remain motionless, making reproduction impossible. The team suggests similar processes may affect other marine animals that spawn externally.

Ocean acidification shifts seawater towards more alkaline conditions, altering its chemical balance. This change could interfere with sperm function in vulnerable species, potentially disrupting their breeding cycles.

The findings highlight a direct link between ocean chemistry and marine reproduction. If acidification continues, salmon and sea urchins may struggle to reproduce, affecting their populations. Further research could reveal whether other species face the same risks.