Microorganisms uniquely capture and predict stony coral tissue loss disease and hurricane disturbance impacts on US Virgin Island reefs

• Published in: Environmental microbiology 2024-04, Vol.26 (4), p.e16610-n/a
• Main Authors: Becker, Cynthia C., Weber, Laura, Llopiz, Joel K., Mooney, T. Aran, Apprill, Amy
• Format: Article
• Language: English
• Subjects: Algae; Ammonium; Ammonium Compounds; Animals; Anthozoa; Benthos; Coral reef ecosystems; Coral Reefs; Cyclonic Storms; Disease outbreaks; Disturbances; Ecosystem; Epidemics; Hurricanes; Microbiomes; Microorganisms; Nutrients; Outbreaks; Turf; United States Virgin Islands; Water
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1111/1462-2920.16610

Coral reef ecosystems are now commonly affected by major climate and disease disturbances. Disturbance impacts are typically recorded using reef benthic cover, but this may be less reflective of other ecosystem processes. To explore the potential for reef water‐based disturbance indicators, we conducted a 7‐year time series on US Virgin Island reefs where we examined benthic cover and reef water nutrients and microorganisms from 2016 to 2022, which included two major disturbances: hurricanes Irma and Maria in 2017 and the stony coral tissue loss disease outbreak starting in 2020. The disease outbreak coincided with the largest changes in the benthic habitat, with increases in the percent cover of turf algae and Ramicrusta, an invasive alga. While sampling timepoint contributed most to changes in reef water nutrient composition and microbial community beta diversity, both disturbances led to increases in ammonium concentration, a mechanism likely contributing to observed microbial community shifts. We identified 10 microbial taxa that were sensitive and predictive of increasing ammonium concentration. This included the decline of the oligotrophic and photoautotrophic Prochlorococcus and the enrichment of heterotrophic taxa. As disturbances impact reefs, the changing nutrient and microbial regimes may foster a type of microbialization, a process that hastens reef degradation. US Virgin Island reefs were recently impacted by major disturbances, but the ecosystem‐wide impacts are not well characterized. Therefore, we measured reef seawater nutrients and microorganisms. Over time, as the underlying reef habitat became enriched in algae, the overlying seawater ecosystem became enriched in ammonium and certain heterotrophic bacteria, while the primary producer, Prochlorococcus, declined. Microbes and nutrients captured ecosystem‐wide impacts of disturbances and may be useful to future reef monitoring programs.