Sea cucumbers as bioindicators of pollution and sea cucumber microbiomes as markers of environmental stress: A review

The gut microbiota of sea cucumbers has been revealed to be a sensitive indicator of both the physiological state and environmental conditions affecting these echinoderms. Thus, they offer promising potential as a biomonitoring tool for assessing environmental stress. The present review article aims to synthesize the most relevant findings on the composition and variability of gut microbiota in different species of sea cucumbers. The review focuses on their response to emerging contaminants such as microplastics, heavy metals, endocrine disruptors and pharmaceutical compounds, given the relevance of this to antibiotics. Included studies reveal that the intestinal microbial community is highly diverse and dynamic, depending on multiple factors such as the physiological state of the organism, environmental conditions of the habitat, diet, seasonality and exposure to contaminants. Among the microbial groups identified, Pseudomonadota clearly stands out as the predominant phylum in all species studied. Overall, the evidence produced supports the use of gut microbiota as an effective bioindicator for assessing anthropogenic impact on marine ecosystems. However, further research incorporating multi-omics approaches and functional analyses are needed to better understand the ecological implications of changes in the microbial community. An important contribution of the present work is the update of the taxonomic nomenclature pertaining to the microorganisms described in the work according to the LPSN (List of Prokaryotic names with Standing in Nomenclature).