Adaptive resilience of sea urchins against seawater acidification: A study on egg quality and offspring performance within a volcanic vents area.

Local adaptation plays a critical role in an organism's ability to survive and reproduce in diverse environmental conditions, potentially improving an organism's response to stressful conditions such as ocean acidification or pollution. In this study, the effects of lower pH coupled with the presence of environmental contaminants were assessed on sea urchins (Paracentrotus lividus) collected outside and inside a volcanic CO2-vent system, where the mean ambient pH is 8.1 and 7.7, respectively. Both groups of sea urchins were spawned, and offspring were reared at pH 8.1 and 7.7, and in the presence or absence of a mixture of 100 μg/L of glyphosate and its main metabolite aminomethylphosphonic acid. Offspring performance metrics (development, abnormalities, and growth) were investigated under the different exposure conditions. The exposure to reduced pH affected the development and larval growth in echinoplutei obtained from adults of both sites, although to a different extent. Chemicals mixture had an additive effect in slowing embryo development. Results revealed that sea urchins living within the lower pH Vents area exhibited significantly higher egg quality, which likely enhanced embryonic development, reduced abnormalities, and increased larval size compared to their counterparts outside the Vents system, both in the presence and absence of contaminants. Findings suggest that sea urchins living within the CO2-Vents system developed adaptations to thrive under lower pH conditions. Elevated egg quality and improved offspring performance suggest organisms' resilience to environmental stressors associated with seawater acidification. Although insights gained from this study are preliminary, mostly due to the limited number of replicates in the egg biochemical analysis, they contribute to unveiling the adaptive capabilities of sea urchins in facing ongoing ocean acidification challenges.