MEPS 589:85-96 (2018)  -  DOI: https://doi.org/10.3354/meps12443

Reef sponges facilitate the transfer of coral-derived organic matter to their associated fauna via the sponge loop

Laura Rix1,*, Jasper M. de Goeij2, Dick van Oevelen3, Ulrich Struck4, Fuad A. Al-Horani5, Christian Wild6,**, Malik S. Naumann6,7,**

1GEOMAR Helmholtz Centre for Ocean Research Kiel, RD3 Marine Microbiology, Düsternbrooker Weg 20, 24105 Kiel, Germany
2Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94248, 1090 GE Amsterdam, The Netherlands
3Department of Estuarine and Delta Systems, NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University, PO Box 140, 4400 AC Yerseke, The Netherlands
4Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstr. 43, 10115 Berlin, Germany
5The University of Jordan - Aqaba and Marine Science Station, PO Box 2595, Aqaba 77110, Jordan
6Faculty of Biology and Chemistry (FB 2), University of Bremen, UFT, Leobener Str. 6, 28359 Bremen, Germany
7Coral Reef Ecology Group, Leibniz Center for Tropical Marine Research (ZMT), Fahrenheitstr. 6, 28359 Bremen, Germany
*Corresponding author: **These authors contributed equally to this work

ABSTRACT: The high biodiversity of coral reefs results in complex trophic webs where energy and nutrients are transferred between species through a multitude of pathways. Here, we hypothesize that reef sponges convert the dissolved organic matter released by benthic primary producers (e.g. corals) into particulate detritus that is transferred to sponge-associated detritivores via the sponge loop pathway. To test this hypothesis, we conducted stable isotope (13C and 15N) tracer experiments to investigate the uptake and transfer of coral-derived organic matter from the sponges Mycale fistulifera and Negombata magnifica to 2 types of detritivores commonly associated with sponges: ophiuroids (Ophiothrix savignyi and Ophiocoma scolopendrina) and polychaetes (Polydorella smurovi). Findings revealed that the organic matter naturally released by the corals was indeed readily assimilated by both sponges and rapidly released again as sponge detritus. This detritus was subsequently consumed by the detritivores, demonstrating transfer of coral-derived organic matter from sponges to their associated fauna and confirming all steps of the sponge loop. Thus, sponges provide a trophic link between corals and higher trophic levels, thereby acting as key players within reef food webs.


KEY WORDS: Coral mucus · Reef trophic web · Detritus · Sponge loop · Detritivore · Trophic interactions · Interspecific associations


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Cite this article as: Rix L, Goeij JMd, Oevelen Dv, Struck U, Al-Horani FA, Wild C, Naumann MS (2018) Reef sponges facilitate the transfer of coral-derived organic matter to their associated fauna via the sponge loop. Mar Ecol Prog Ser 589:85-96. https://doi.org/10.3354/meps12443

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