Human activities are rapidly changing the structure and function of coastal marine ecosystems. Large-scale replacement of kelp forests and coral reefs with turf algal mats is resulting in homogenous habitats that have less ecological and human value. Ocean acidification has strong potential to substantially favour turf algae growth, which led us to examine the mechanisms that stabilise turf algal states. Here we show that ocean acidification promotes turf algae over corals and macroalgae, mediating new habitat conditions that create stabilising feedback loops (altered physicochemical environment and microbial community, and an inhibition of recruitment) capable of locking turf systems in place. Such feedbacks help explain why degraded coastal habitats persist after being initially pushed past the tipping point by global and local anthropogenic stressors. An understanding of the mechanisms that stabilise degraded coastal habitats can be incorporated into adaptive management to better protect the contribution of coastal systems to human wellbeing.

人类活动正在迅速改变沿海海洋生态系统的结构和功能。用草皮藻垫大规模取代海带森林和珊瑚礁导致生态和人类价值较低的同质栖息地。海洋酸化具有极大的促进草坪藻类生长的潜力，这促使我们研究了稳定草坪藻类状态的机制。在这里，我们表明海洋酸化促进了珊瑚和大型藻类上的草坪藻类，调节了新的栖息地条件，创造了能够将草坪系统锁定到位的稳定反馈回路（改变的物理化学环境和微生物群落，以及抑制补充）。这些反馈有助于解释为什么退化的沿海栖息地在最初被全球和当地人为压力因素推动超过临界点后仍然存在。对稳定退化的沿海栖息地的机制的理解可以纳入适应性管理，以更好地保护沿海系统对人类福祉的贡献。