Ocean acidification induces budding in larval sea urchins@en

Ocean acidification (OA), the reduction of ocean pH due to hydration of atmospheric CO2, is known to affect growth and survival of marine invertebrate larvae. Survival and transport of vulnerable planktonic larval stages play important roles in determining population dynamics and community structures in coastal ecosystems. Here, we show that larvae of the purple urchin, Strongylocentrotus purpuratus, underwent high-frequency budding (release of blastula-like particles) when exposed to elevated pCO2 level (>700 µatm). Budding was observed in >50 % of the population and was synchronized over short periods of time (~24 h), suggesting this phenomenon may be previously overlooked. Although budding can be a mechanism through which larval echinoids asexually reproduce, here, the released buds did not develop into viable clones. OA-induced budding and the associated reduction in larval size suggest new hypotheses regarding physiological and ecological tradeoffs between short-term benefits (e.g. metabolic savings and predation escape) and long-term costs (e.g. tissue loss and delayed development) in the face of climate change.海洋酸化（Ocean Acidification, OA）是指因大气二氧化碳发生水合反应而导致的海洋pH值下降现象，已知其会影响海洋无脊椎动物幼虫的生长与存活。脆弱的浮游幼虫阶段的存活与扩散，是决定海岸生态系统种群动态与群落结构的关键因素。本研究发现，紫海胆（Strongylocentrotus purpuratus）幼虫在暴露于升高的二氧化碳分压（pCO₂）水平（>700 µatm）环境时，会发生高频出芽现象（即释放囊胚样颗粒）。该种群中超过50%的个体出现出芽现象，且该过程在约24小时的短时段内同步发生，这表明该现象此前可能被忽视。尽管出芽可作为海胆幼虫无性繁殖的一种途径，但本研究中释放出的芽体无法发育为具有存活能力的克隆个体。海洋酸化诱导的出芽现象及其伴随的幼虫体型减小，为理解气候变化背景下生理与生态权衡（如短期收益：代谢节约与逃避捕食；长期代价：组织损失与发育延迟）提供了新的假说。