MEPS 339:93-98 (2007)  -  doi:10.3354/meps339093

ABSTRACT: It is well documented that biotic effects play an important role in determining the distribution and abundance of sponges on Caribbean coral reefs: predation by fishes restricts some species to refugia, and allelopathic interactions result in a competitive hierarchy for space. Recently, it has been proposed that biotic effects are similarly important in mangrove habitats; specifically, that sponges common to mangrove habitats grow fast and rapidly out-compete species otherwise found in reef habitats for prop-root space. To begin to test this hypothesis, 9 species of common reef sponges were transplanted to prop roots at 3 mangrove sponge sites with different flow regimes (as measured with plaster clods) near Key Largo, Florida. Reef sponges transplanted to all 3 mangrove sites declined in health and died, most within 60 d, while those back-transplanted to a reef site survived and grew. Reef sponge decline was most rapid at sites with the lowest flow during periods of the month with the least tidal flux, when a combination of freshwater input, high temperature and turbidity were likely responsible for their demise. We conclude that some mangrove sites that support sponge growth do so because the species found there can endure the abiotic conditions of mangrove habitats, and not because of competitive dominance over species otherwise found on the reef.

KEY WORDS:Physical effects · Flow regime · Mangrove · Fouling community · Temperature-salinity stress · Predation