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IntroductionIn recent decades, Caribbean coral reefs have lost many vital marine species due to diseases. The well-documented mass mortality event of the long-spined black sea urchinDiadema antillarumin the early 1980s stands out among these collapses. This die-off killed over 90% ofD. antillarumchanging the reefscape from coral to algal-dominated. Nearly 40 years later,D. antillarumpopulations have yet to recover. In early 2022, a new mortality event ofD. antillarumwas reported along the Caribbean, including Puerto Rico. MethodsThis study identifies the gut microbiota changes associated with theD. antillarumduring this mortality event. It contrasts them with the bacterial composition of gut samples from healthy individuals collected in 2019 by using 16S rRNA sequencing analyses. ResultsNotably, the die-off group’s core microbiome resembled bacteria commonly found in the human skin and gut, suggesting potential anthropogenic contamination and wastewater pollution as contributing factors to the 2022 dysbiosis. The animals collected in 2022, especially those with signs of disease, lacked keystone taxa normally found inDiademaincludingPhotobacteriumandPropionigenium. DiscussionThe association between human microbes and disease stages in the long-spined urchinD. antillarum, especially in relation to anthropogenic contamination, highlights a complex interplay between environmental stressors and marine health. While these microbes might not be the direct cause of death in this species of sea urchins, their presence and proliferation can indicate underlying issues, such as immune depletion due to pollution, habitat destruction, or climate change, that ultimately compromise the health of these marine organisms.
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Transglobal spread of an ecologically relevant sea urchin parasite
Abstract Mass mortality of the dominant coral reef herbivore Diadema antillarum in the Caribbean in the early 1980s contributed to a persistent phase shift from coral- to algal-dominated reefs. In 2022, a scuticociliate most closely related to Philaster apodigitiformis caused further mass mortality of D. antillarum across the Caribbean, leading to >95% mortality at affected sites. Mortality was also reported in the related species Diadema setosum in the Mediterranean in 2022, though the causative agent of the Mediterranean outbreak has not yet been determined. In April 2023, mass mortality of Diadema setosum occurred along the Sultanate of Oman's coastline. Urchins displayed signs compatible with scuticociliatosis including abnormal behavior, drooping and loss of spines, followed by tissue necrosis and death. Here we report the detection of an 18S rRNA gene sequence in abnormal urchins from Muscat, Oman, that is identical to the Philaster strain responsible for D. antillarum mass mortality in the Caribbean. We also show that scuticociliatosis signs can be elicited in Diadema setosum by experimental challenge with the cultivated Philaster strain associated with Caribbean scuticociliatosis. These results demonstrate the Philaster sp. associated with D. antillarum mass mortality has rapidly spread to geographically distant coral reefs, compelling global-scale awareness and monitoring for this devastating condition through field surveys, microscopy, and molecular microbiological approaches, and prompting investigation of long-range transmission mechanisms.
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- Award ID(s):
- 2049225
- PAR ID:
- 10559214
- Publisher / Repository:
- ISME Journal
- Date Published:
- Journal Name:
- The ISME Journal
- Volume:
- 18
- Issue:
- 1
- ISSN:
- 1751-7362
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/ismejo/wrae024
