RESEARCH ARTICLE Sponge chemical defenses are a possible mechanism for increasing sponge abundance on reefs in Zanzibar Stephanie B. Helber1,2*, Dieuwke J. J. Hoeijmakers1, Christopher A. Muhando3, Sven Rohde2, Peter J. Schupp2,4* 1 Leibniz Centre for Tropical Marine Research (ZMT), Bremen, Germany, 2 Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl-von-Ossietzky University Oldenburg, Wilhelmshaven, Germany, 3 Institute of Marine Sciences (IMS), University of Dar es Salaam, Stonetown, Zanzibar, Tanzania, a1111111111 4 Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg, Oldenburg, Germany a1111111111 a1111111111 *
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[email protected] (SBH) a1111111111 a1111111111 Abstract Coral reefs are experiencing increasing anthropogenic impacts that result in substantial declines of reef-building corals and a change of community structure towards other benthic OPEN ACCESS invertebrates or macroalgae. Reefs around Zanzibar are exposed to untreated sewage and Citation: Helber SB, Hoeijmakers DJJ, Muhando CA, Rohde S, Schupp PJ (2018) Sponge chemical runoff from the main city Stonetown. At many of these sites, sponge cover has increased defenses are a possible mechanism for increasing over the last years. Sponges are one of the top spatial competitors on reefs worldwide. Their sponge abundance on reefs in Zanzibar. PLoS ONE success is, in part, dependent on their strong chemical defenses against predators, micro- 13(6): e0197617. https://doi.org/10.1371/journal.