Coral mucus functions as an energy carrier and particle trap in the reef ecosystem

Zooxanthellae, endosymbiotic algae of reef-building corals, substantially contribute to the high gross primary production of coral reefs, but corals exude up to half of the carbon assimilated by their zooxanthellae as mucus. Here we show that released coral mucus efficiently traps organic matter from the water column and rapidly carries energy and nutrients to the reef lagoon sediment, which acts as a biocatalytic mineralizing filter. In the Great Barrier Reef, the dominant genus of hard corals, Acropora, exudes up to 4.8 litres of mucus per square metre of reef area per day. Between 56% and 80% of this mucus dissolves in the reef water, which is filtered through the lagoon sands. Here, coral mucus is degraded at a turnover rate of at least 7% per hour. Detached undissolved mucus traps suspended particles, increasing its initial organic carbon and nitrogen content by three orders of magnitude within 2 h. Tidal currents concentrate these mucus aggregates into the lagoon, where they rapidly settle. Coral mucus provides light energy harvested by the zooxanthellae and trapped particles to the heterotrophic reef community, thereby establishing a recycling loop that supports benthic life, while reducing loss of energy and nutrients from the reef ecosystem.

[1]  Ron Johnstone,et al.  Degradation and mineralization of coral mucus in reef environments , 2004 .

[2]  The Theory of Brittle Fracture Initiation under Triaxial Stress Conditions—II , 1970 .

[3]  L. Muscatine,et al.  Wax in coral mucus: Energy transfer from corals to reef fishes1 , 1974 .

[4]  David A. Krupp,et al.  Mucus Production by Corals Exposed during an Extreme Low Tide , 1984 .

[5]  B. Thomassin,et al.  Microbial utilization of coral mucus in long term in situ incubation over a coral reef , 1991, Hydrobiologia.

[6]  L. Muscatine,et al.  Estimating the daily contribution of carbon from zooxanthellae to coral animal respiration1 , 1981 .

[7]  W. Muehlberger.  Conjugate Joint Sets of Small Dihedral Angle , 1961, The Journal of Geology.

[8]  Mohammed Rasheed,et al.  Endoscopic exploration of Red Sea coral reefs reveals dense populations of cavity-dwelling sponges , 2001, Nature.

[9]  J. Jaubert,et al.  Enhancement of pico- and nanoplankton growth by coral exudates , 2000 .

[10]  G. Gust,et al.  Solute release mechanisms from confined sediment cores in stirred benthic chambers and flume flows , 1992 .

[11]  N. Marshall,et al.  Observations on organic aggregates in the vicinity of coral reefs , 1968 .

[12]  K. Parnell,et al.  Water movement within a fringing reef flat, Orpheus Island, North Queensland, Australia , 1986, Coral Reefs.

[13]  S. Murrell,et al.  The Effect of Triaxial Stress Systems on the Strength of Rocks at Atmospheric Temperatures , 1965 .

[14]  Yossi Loya,et al.  The rate of mucus production by corals and its assimilation by the coral reef copepod Acartia negligens1 , 1975 .

[15]  Kiyoo Mogi,et al.  Effect of the intermediate principal stress on rock failure , 1967 .

[16]  D. Lockner,et al.  Nucleation and growth of faults in brittle rocks , 1994 .

[17]  Denis Allemand,et al.  Photosynthesis, respiration and calcification of a zooxanthellate scleractinian coral under submerged and exposed conditions , 1997 .

[18]  R. W. Buddemeier,et al.  Coral-reef hydrology: field studies of water movement within a barrier reef , 1986, Coral Reefs.

[19]  Jessica J. Meeuwig,et al.  Preferences of planktotrophic larvae of the tropical serpulid Spirobranchus giganteus (Pallas) for exudates of corals from a Barbados reef , 1990 .

[20]  T. Engelder.  TRANSITIONAL-TENSILE FRACTURE PROPAGATION : A STATUS REPORT , 1999 .

[21]  W. F. Brace,et al.  An extension of the Griffith theory of fracture to rocks , 1960 .

[22]  D. J. W. Moriarty,et al.  Temporal and spatial variation in bacterial production in the water column over a coral reef , 1985 .

[23]  Richard H. Sibson,et al.  Brittle-failure controls on maximum sustainable overpressure in different tectonic regimes , 2003 .

[24]  P. Spencer Davies,et al.  The role of zooxanthellae in the nutritional energy requirements of Pocillopora eydouxi , 1984, Coral Reefs.

[25]  A. Shanks,et al.  Laboratory-made artificial marine snow: a biological model of the real thing , 1989 .

[26]  John Stimson,et al.  The temporal pattern and rate of release of zooxanthellae from the reef coral Pocillopora damicornis (Linnaeus) under nitrogen-enrichment and control conditions , 1991 .

[27]  Norden E. Huang,et al.  The subtidal pump: a mechanism of interstitial water exchange by wave action , 1972 .

[28]  M. Pieri,et al.  Rheological and microstructural evolution of Carrara marble with high shear strain: results from high temperature torsion experiments , 2001 .

[29]  G. N. Richards,et al.  Structural investigations on the mucus from six species of coral , 1988 .

[30]  T. Engelder.  Analysis of pinnate joints in the Mount Desert Island granite: Implications for postintrusion kinematics in the coastal volcanic belt, Maine , 1989 .

[31]  R. E. Johannes.  ECOLOGY OF ORGANIC AGGREGATES IN THE VICINITY OF A CORAL REEF1 , 1967 .

[32]  J. Handin,et al.  On the Coulomb‐Mohr failure criterion , 1969 .

[33]  J. Handin,et al.  Chapter 13: Observations on Fracture and a Hypothesis of Earthquakes , 1960 .

[34]  Michael A. Borowitzka,et al.  Diurnal lipid and mucus production in the staghorn coral Acropora acuminata , 1980 .

[35]  E. R. Hoskins.  The failure of thick-walled hollow cylinders of isotropic rock , 1969 .

[36]  D. Secor.  Role of fluid pressure in jointing , 1965 .

[37]  R. R. Strathmann,et al.  Observations on coral mucus “flocs” and their potential trophic significance1 , 1973 .

[38]  Cr Wilkinson,et al.  MICROBIAL ECOLOGY ON A CORAL-REEF , 1987 .

[39]  T. Goreau,et al.  Corals and Coral Reefs , 1979 .

[40]  Ralph Mitchell,et al.  Bacterial populations and adaptations in the mucus layers on living corals1 , 1979 .

[41]  Branko Velimirov,et al.  Microheterotrophic utilization of mucus released by the Mediterranean coral Cladocora cespitosa , 1986 .

[42]  J. C. Jaeger,et al.  Stresses and failure in rings of rock loaded in diametral tension or compression , 1966 .

[43]  R. Schock,et al.  Strain behavior of a granite and a Graywacke sandstone in tension , 1982 .