Short-therm exposure at CO2 vents affect spermatogenesis in a temperate non-zooxanthelate coral

Ocean acidification is expected to significantly affect calcifying marine organisms, such as corals. While ocean acidification effects on coral calcification have been widely investigated, the effects on coral gametogenesis are almost unknown. A volcanic vent at Panarea Island (Mediterranean Sea, Italy) characterized by continuous and localized CO2 emission, generates a stable pCO2 gradient from the centre to its periphery, providing a unique natural laboratory for ocean acidification studies. Here we assessed the effects of ocean acidification on gametogenesis and embryogenesis of the Mediterranean non-zooxanthellate coral Leptopsammia pruvoti transplanted along this natural pCO2 gradient. After 3 months under experimental conditions, increasing pCO2 seemed to negatively influence spermary production and development. In the control Site, all spermaries showed the latest (most advanced) maturation stage while in the most acidic Sites they also displayed earlier stages, indicating a delay in spermatogenesis and consequently of fertilization and planulation processes. Considering the negative response showed by this species after a short-term exposure, an even stronger negative effect on sexual reproduction is hypothesized under a long-term exposure.