Geology Club Seminar

Microbialization is a process by which trophic restructuring shunts organic matter away from higher trophic levels into inefficient microbial biomass production and respiration. It is supported by a positive feedback loop, where DOC released by ungrazed fleshy macro- and turf algae fosters copiotrophic, potentially pathogenic bacteria, ultimately leading to coral disease and increased algal competitive dominance (DDAM: DOC, Disease, Algae, Microbes). Here we provide geochemical and microbiological evidence that microbialization is tightly coupled to phase shifts in benthic reef communities on a global scale. Using an unprecedented dataset of 430 samples on 60 coral reef sites across three oceans we show that increased algal cover correlates with lower concentrations of DOC and higher microbial abundance. Metagenomic analysis further shows a shift in microbial community metabolism towards faster, but less efficient glycolytic pathways. This yield-to-power switch in the microbial communities directly threatens reefs through higher disease prevalence and by depleting oxygen and organic nutrients at the expense of higher trophic levels.