Paper Reviewed
Gizzi, F., de Mas, L., Airi, V., Caroselli, E., Prada, F., Falini, G., Dubinsky, Z. and Goffredo, S. 2017. Reproduction of an azooxanthellate coral is unaffected by ocean acidification. Scientific Reports 7: 13049, DOI: 10.1038/s41598-017-13393-1.

Introducing the reason for their study, Gizzi et al. (2017) write that "sexual reproduction represents a crucial process in the development and persistence of populations and its reduction threatens the resilience of species, leading to shifts in size and abundance of populations." Despite this importance, however, very few studies have examined the effects of ocean acidification on the sexual reproduction of corals. And for those that do, they are typically conducted in a laboratory setting, which often is quite different from conditions that exist in the complex natural environment.

Hoping to add some knowledge about the impact of ocean acidification on the sexual reproduction of a temperate coral in its natural environment, the team of eight researchers set out to conduct such an experiment in naturally acidified waters of the Tyrrhenian Sea (36.64°N, 15.11°E). There, a volcanic vent off the coast of Italy (the Panarea CO2 vent) emits nearly pure CO2 into the surrounding seawater, creating a natural pH gradient expanding outward from the vent some 34 meters.

Within these waters, Gizzi et al. transplanted sexually mature specimens of a temperate azooxanthellate solitary scleractinian coral (Leptopsammia pruvoti), which were obtained from a location less than 2 km away from the vent site, into one of four sites with mean seawater pH values representing conditions of normal (8.07), intermediate (7.87 and 7.74) and severe (7.40) ocean acidification. After three months, the scientists measured a number of reproductive parameters of the transplanted corals, attempting to discern if there were any effects of the differing seawater pH regimes.

Results of the analysis revealed, in the words of the authors, that the solitary non-zooxanthellate L. pruvoti showed "no effects on gametogenesis, spermatogenesis and embryogenesis along the pH gradient," which findings suggest that the "reproductive potential may be quite tolerant to decreasing pH" and that L. pruvoti "will be fine in [the] coming decades."