Coralline algae, a major calcifying component of coastal shallow water communities, have been shown to be one of the more vulnerable taxonomic groups to ocean acidification (OA). Under OA, the interaction between corallines and epiphytes was previously described as both positive and negative. We hypothesized that the photosynthetic activity and the complex structure of non-calcifying epiphytic algae that grow on corallines ameliorate the chemical microenvironmental conditions around them, providing protection from OA. Using mesocosm and microsensor experiments, we showed that the widespread coralline Ellisolandia elongata is less susceptible to the detrimental effects of OA when covered with non-calcifying epiphytic algae, and its diffusive boundary layer is thicker than when not covered by epiphytes. By modifying the microenvironmental carbonate chemistry, epiphytes, facilitated by OA, create micro-scale shield (and refuge) with more basic conditions that may allow the persistence of corallines associated with them during acidified conditions. Such ecological refugia could also assist corallines under near-future anthropogenic OA conditions.

珊瑚藻是沿海浅水群落的主要钙化成分，已被证明是最易受海洋酸化（OA）影响的生物分类群之一。在开放获取下，珊瑚和附生植物之间的相互作用以前被描述为阳性和阴性。我们假设在珊瑚线上生长的光合作用活性和非钙化附生藻类的复杂结构改善了它们周围的化学微环境条件，从而为OA提供了保护。使用中观宇宙和微传感器实验，我们发现广泛分布的珊瑚大肠埃里索兰达当覆盖有非钙化的附生藻类时，它对OA的有害作用较不敏感，并且其扩散边界层比未覆盖附生菌时更厚。通过改变微环境的碳酸盐化学性质，在OA的帮助下，附生植物可以在更基本的条件下形成微尺度的防护层（和避难所），这些条件可能会使与珊瑚有关的珊瑚在酸化条件下持续存在。这样的生态避难所还可以在近来的人为OA条件下协助珊瑚礁。