Sea urchins are biotic factors driving the decline of kelp forests in marine ecosystems. However, few studies have analyzed the microbiota of surviving sea urchins in barren regions with scarce diet resources. Here, we analyzed the microbiota in the pharynx and gut of the sea urchin Mesocentrotus nudus located along the coast of an expanding barren region in South Korea. The ecological adaptation of genera in sea urchins was predicted using the neutral assembly model. The pharynx and gut microbiota were different, and microbes in the surrounding habitats dispersed more to the pharynx than to the gut. The gut microbiota in sea urchins is altered by barren severity and plays different roles in host energy metabolism. These findings help to understand the microbiota in sea urchins according to urchin barren and its contribution to the survival of sea urchins in severe barren regions with limited macroalgae.

海胆是驱动海洋生态系统中海带森林衰退的生物因素。然而，很少有研究分析饮食资源稀缺的贫瘠地区幸存海胆的微生物群。在这里，我们分析了位于韩国不断扩大的贫瘠地区沿岸的海胆Mesocentrotus nudus的咽部和肠道中的微生物群。使用中性装配模型预测了海胆属的生态适应。咽部和肠道微生物群不同，周围栖息地的微生物更多地分散到咽部而不是肠道。海胆的肠道微生物群会因贫瘠的严重程度而改变，并在宿主能量代谢中发挥不同的作用。这些发现有助于根据海胆贫瘠了解海胆中的微生物群，及其对大型藻类有限的严重贫瘠地区海胆生存的贡献。