Microbial Interactions with Dissolved Organic Matter Are Central to Coral Reef Ecosystem Function and Resilience

Abstract

To thrive in nutrient-poor waters, coral reefs must retain and recycle materials efficiently. This review centers microbial processes in facilitating the persistence and stability of coral reefs, specifically the role of these processes in transforming and recycling the dissolved organic matter (DOM) that acts as an invisible central currency in reef production, nutrient cycling, and organismal interactions. The defining characteristics of coral reefs, including high productivity, balanced metabolism, high biodiversity, nutrient recycling efficiency, and structural complexity, are inextricably linked to microbial processing of DOM. The composition of microbes and DOM in reefs is summarized, and the spatial and temporal dynamics of biogeochemical processes carried out by microorganisms in diverse reef habitats are explored in a variety of key reef processes, including decomposition, accretion, trophic transfer, and macronutrient recycling. Finally, we examine how widespread habitat degradation of reefs is altering these important microbe–DOM interactions, creating feedbacks that reduce reef resilience to global change. Expected final online publication date for the Annual Review of Marine Science, Volume 15 is January 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Small-scale oxygen distribution patterns in a coral reef

“…Our results further highlight the importance of previously described positive feedback loops that may be created during phase-shifts from coral-to algal-dominance on reefs (Smith et al, 2006;Barott and Rohwer, 2012). Initial increases in algal biomass or productivity (due to natural and/or anthropogenic stressors) results in an increase and a compositional change of dissolved organic compounds released in the water column (Kelly et al, 2022;Nelson et al, 2022). These compounds promote increased microbial activity and a change towards more copiotrophic and pathogenic communities resulting in a higher prevalence of diseases and local hypoxic zones that can rapidly stress or even kill corals giving algae a competitive advantage.…”

“…However, these water movements play a pivotal role in the ecology of nearshore systems. Not only do they affect the concentrations and dispersal of land-derived substances (Li et al, 1999), which, in the Anthropocene, are mostly pollutants or other agents harmful to the environment (e.g., DeGeorges et al, 2010;Macıás-Zamora, 2011;Prouty et al, 2017), they also affect metabolism or interactions of virtually all reef denizens (e.g., Koehl, 1982;Abelson and Denny, 1997;Mass et al, 2010;Lenihan et al, 2015;Nelson et al, 2022). But these turbulent water movements close to the reef framework are hard to measure or to predict (Nowell and Jumars, 1984).…”

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

“…Though most nutrients and the community of microorganisms in reef water changed across sampling events, we identified microorganisms impacted by disturbance based on their sensitivity to and predictability of ammonium concentration. The depletion of dominant reef oligotrophic photoautotrophs, Prochlorococcus , and the increase in abundance of multiple lineages of heterotrophic microorganisms may be indicators of microbialization on these reefs, which is a mechanism that hastens reef decline (Haas et al, 2016; Nelson et al, 2023). We found that microbial communities were both sensitive and predictive of disturbance‐based impacts to reef habitats, lending support for their further inclusion in programs that monitor increasingly threatened reef ecosystems.…”

Nutrient subsidies restructure coral reef dissolved carbon fluxes via biogeochemical cascades

“…5e,p; Fig. S1 -S4), likely because producers release exudates during the day and microbial respiration utilizes DOM at night 60 . NEC generally decreased proteinaceous fDOM in the water column (Fig.…”