Degradation and mineralization of coral mucus in reef environments

Abstract

With in situ and laboratory chamber incubations we demonstrate that coral mucus, an important component of particulate organic matter in reef ecosystems, is a valuable substrate for microbial communities in the water column and sandy sediments of coral reefs. The addition of coral mucus to the water of benthic chambers placed on lagoon sands in the coral cay Heron Island, Australia, resulted in a rapid and significant increase in both O 2 consumption and DIC production in the chambers. The permeable coral sands permitted the transport of mucus into the sediment with interfacial water flows, resulting in the mucus being mainly (> 90%) degraded in the sediment and not in the water column of the chambers. A low ratio of 0.48 (in situ) to 0.64 (laboratory) for O 2 consumption/DIC production after the addition of coral mucus, and high sulfate reduction rates (SRR) in natural sediments which were exposed to coral mucus, suggest a large contribution of anaerobic processes to the degradation of coral mucus. Oxygen penetrated less than 5 mm deep into these sediments. The microbial reaction to mucus addition was rapid, with a calculated in situ C turnover rate ranging from 7 to 18% h -1 . The degradation of coral mucus showed a dependency on the permeability of the carbonate sediments, with faster degradation and remineralization in coarse sands. This indicates the importance of permeable reef sediments for the trapping and degradation of organic matter. We suggest that coral mucus may have a function as a carrier of energy to the benthic microbial consumers.KEY WORDS: Coral mucus · POM · Degradation · Permeable carbonate sands · O 2 consumption · DIC production · C turnover Resale or republication not permitted without written consent of the publisher

Depleted dissolved organic carbon and distinct bacterial communities in the water column of a rapid-flushing coral reef ecosystem

“…DOM adsorbtion to the high-porosity carbonate sands common in the backreef habitats of Moorea is another abiotic removal process that may be important and has been demonstrated in similar environments (Suess, 1970;Hillgärtner et al, 2001). However, this process is difficult to distinguish from heterotrophic reef sediment biofilms that can remove DOM (Wild et al, 2004(Wild et al, , 2006. Although the backreef habitats in Moorea have abundant carbonate sands, preliminary results show no difference in DOC concentrations in these surficial sediments (data not shown).…”

Coral sand O2 uptake and pelagic–benthic coupling in a subtropical fringing reef, Aqaba, Red Sea

“…For each experiment, between 1 and 4 stirred benthic chambers identical to those described by Huettel & Gust (1992) and Wild et al (2004bWild et al ( ,c, 2005 were used to measure sedimentary O 2 uptake. The opaque cylindrical chambers were 30 cm in height with an inner diameter of 19 cm and excluded all light from the enclosed water and sediment (benthic primary production rate was not addressed in the present study).…”

“…The reef sediments, in particular the permeable calcareous sands with their high abundances of phototrophic and heterotrophic microbes , contribute significantly to primary production, carbon mineralization and nutrient cycling of reef ecosystems (Johnstone et al 1990, Clavier & Garrigue 1999, Wild et al 2004b,c, 2005. Sedimentary production and decomposition processes control O 2 flux across the sediment -water interface, and investigations by Werner et al (2006) suggest that O 2 is the dominant electron acceptor over sulphate in permeable coral reef sands.…”

Signaling-mediated cross-talk modulates swarming and biofilm formation in a coral pathogen Serratia marcescens

“…Bacterial receptors can bind to mucus (Rosenberg and Falkovitz, 2004;Kvennefors et al, 2008), and this directly controls the composition of the associated microbiota. The mucus polymer itself and small molecular weight compounds within it serve as both nutrient sources for the microbes and signals that modulate behavior and gene expression in the associated microbial communities (Vacelet and Thomassin, 1991;Wild et al, 2004;Ritchie, 2006;Sharon and Rosenberg, 2008;Krediet et al, 2009aKrediet et al, , 2009b. Although the fate of coral mucus in the reef environment and its role in coral-associated microbial communities are becoming more clear, significantly less is known about the microbe-microbe interactions within the coral surface mucus layer.…”