Alterations in sea urchin (Mesocentrotus nudus) microbiota and their potential contributions to host according to barren severity

Abstract

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.

The sea urchin intestinal microbiome responds dynamically to food intake and contains nitrogen-fixing symbionts

“…Field-captured sea urchins also featured relatively diverse microbiomes, which may reflect the lower food availability typical for the winter conditions they were sampled from, or a more varied diet compared to our laboratory conditions. In sea urchin barren grounds in South Korea, the severity of the barren ground, which is related to starvation, did not influence gut bacterial diversity although it did influence microbiome composition (Park et al 2023).…”

“…The intestinal microbiome of S. purpuratus was also found to be distinct from another cooccurring sea urchin species, and varied depending on whether it was sampled from kelp beds or from barren grounds (Miller et al 2021). Similarly, the gut microbiome of another sea urchin, Mesocentrotus nudus, differed depending on barren ground severity (Park et al 2023). M. nudus, S. purpuratus and S. droebachiensis all cause catastrophic grazing of kelp forests, and the latter is a quantitatively relevant grazer of kelp in the entire northern hemisphere (Filbee-Dexter and Scheibling 2014).…”