Coral cavities are sinks of dissolved organic carbon (DOC)

Abstract

We studied the removal of dissolved organic carbon (DOC) by coral cavities of 50-250 dm 3 at a depth range of 5-17 m along the coral reefs of Curaçao, Netherlands Antilles, and the Berau area, East Kalimantan, Indonesia. We found significantly lower DOC concentrations in cavity water compared with ambient reef water. On average, DOC concentrations in cavity water were 15.1 6 6.0 mmol L 21 (Curaçao) and 4.0 6 2.4 mmol L 21 (Berau) lower than in reef water. When the cavities were closed, DOC concentrations in the cavities declined by 22% 6 8% and 11% 6 4% in Curaçao and Berau, respectively, within 30 min. This corresponded to average DOC removal rates per cavity surface area of 342 6 82 mmol C m 22 d 21 in Curaçao and 90 6 45 mmol C m 22 d 21 in Berau. Bioassays showed that bacterioplankton are not responsible for this DOC removal by coral cavities. DOC fluxes exceeded bacterioplankton carbon (BC) fluxes into cavities by two orders of magnitude. On average BC fluxes per cavity surface area were 3.6 6 1.3 mmol C m 22 d 21 (Curaçao) and 1.9 6 1.3 mmol C m 22 d 21 (Berau area). The net DOC removal per square meter of cryptic surface likely exceeded the gross primary production per square meter of planar reef area. We conclude that coral cavities and their biota are net sinks of DOC and play an important role in the energy budget of coral reefs.

Osmotrophy in modular Ediacara organisms

“…As organisms increase in size, SA/V drops and osmotrophy alone becomes insufficient to meet nutrient demands. Thus, strictly osmotrophic organisms tend to be microscopic (e.g., bacteria), although some macroscopic animals, including sponges, corals, brachiopods, bryozoans, molluscs, and echinoderms, use osmotrophic feeding on DOC as a supplemental food source (22)(23)(24)(25)(26).…”

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

“…Corals may rapidly consume DOC and bacterioplankton (Sorokin, 1973), although many recent studies show corals to be sources, rather than sinks, for DOC (Ferrier-Pages et al, 1998;Van Duyl and Gast, 2001;Hata et al, 2002;Nakajima et al, 2009). Recent work has demonstrated the potential for sponges to consume both DOC and bacterioplankton at biogeochemically significant rates (Yahel et al, 2003;Van Duyl et al, 2006;de Goeij and Van Duyl, 2007;De Goeij et al, 2008). However, conspicuous sponge taxa, which exhibit the highest filtration rates (Southwell et al, 2008), are virtually absent from our study area, and even inconspicuous benthic sponges cover o1% of the reef benthos in Moorea on average (Adjeroud, 1997, http://mcr.…”

“…However, conspicuous sponge taxa, which exhibit the highest filtration rates (Southwell et al, 2008), are virtually absent from our study area, and even inconspicuous benthic sponges cover o1% of the reef benthos in Moorea on average (Adjeroud, 1997, http://mcr. lternet.edu/data/), although cryptic coelobite communities can increase reef surface area sevenfold and rapidly remove both DOC and bacterioplankton (Richter et al, 2001;Scheffers et al, 2004;de Goeij and Van Duyl, 2007).…”

Combined Effects of Experimental Acidification and Eutrophication on Reef Sponge Bioerosion Rates

“…Labile DOC represents the portion of the total DOC pool on which sponges can feed, here ∼20% of ∼80 µmolC/kg (Van Duyl and Gast, 2001;De Goeij and Van Duyl, 2007). Treatments were E1: control labile DOC conditions (i.e., only ∼16 µmol/kg natural labile DOC), E2: double labile DOC conditions (natural DOC + 16 µmol/kg DOC as RPMI1640) and E3: triple labile DOC conditions (natural + 32 µmol/kg RPMI 1640).…”