Nocturnal dissolved organic matter release by turf algae and its role in the microbialization of reefs

The increased release of dissolved organic matter (DOM) by algae has been associated with the fast but inefficient growth of opportunistic microbial pathogens and the ongoing degradation of coral reefs. Turf algae (consortia of micro- and macroalgae commonly including cyanobacteria) dominate benthic communities on many reefs worldwide. Opposite to other reef algae that predominantly release DOM during the day, turf algae containing cyanobacteria may additionally release large amounts of DOM at night. However, this night-DOM release and its potential contribution to the microbialization of reefs remains to be investigated.
We first tested the occurrence of hypoxic conditions at the turf algae-water interface, as a lack of oxygen will facilitate the production and release of fermentation intermediates as night-time DOM. Secondly, the dissolved organic carbon (DOC) release by turf algae was quantified during day- and nighttime, and the quality of day and night exudates as food for bacterio...