Microbiota responses to environmental stress in mobile and sessile marine invertebrates: evidence for the effect of dissolved oxygen variations

Resumen: Microbiomes can modulate plant and animal responses to environmental fluctuations, revealing their central role in global biogeochemical cycles and the physiology of individual organisms, and in how these fluctuations are modulated. In marine ecosystems, Eastern Boundary Upwelling Systems (EBUS) allow us to examine host-microbiome dynamic interactions that respond to environmental variation, offering critical insights into the potential impacts of global environmental change. This study investigates the microbiota response of two marine invertebrates that co-occur at sites with strong synoptic and seasonal fluctuations in temperature and dissolved oxygen concentration between winter and summer. Specimens of the sessile marine tunicate Pyura chilensis (“Piure”) and the porcelain crab Allopetrolisthes punctatus (“Changai”) were collected at about 10 m depth under contrasting oxygen regimes in summer and winter at Chome, central Chile. Microbiota from gills and digestive glands were assessed via 16S rRNA Nanopore sequencing, which showed clear differences in bacterial community structure and composition between species and across summer and winter surveys. Functional predictions suggest that shifts in the microbiota are primarily associated with variations in exposure to hypoxic waters induced by intensified upwelling. This suggests that the microbiomes may positively influence host performance under environmental stress, enhancing resistance to low dissolved oxygen conditions.