Benthic jellyfish facilitate the release of sediment pore water in coastal mangrove habitats

The benthos plays a critical role in regulating nutrient cycling in mangrove ecosystems by acting as a nutrient sink. Several known processes, including diffusion and bioturbation by burrowing animals, have been shown to liberate nutrients from benthic sediments. This study demonstrates a novel pathway by which the epibenthic jellyfish, Cassiopea sp., can release pore water from marine sediments into the water column at rates that are several orders of magnitude greater than diffusion. Such an alteration to benthic-pelagic flux gives this species the potential to dynamically alter nutrient flow in areas where they occur. We found that pore water liberation scales with animal size and an average-sized individual (8.6 cm bell diameter) can release 2.64 ml h^-1 of benthic pore water into the water column. Since Cassiopea have been found to frequently relocate along the benthos, the likelihood of continually encountering nutrient rich pore water is high. Given the results of this study and previously reported data on nutrient availability in Florida mangrove ecosystems, the presence of an average population density of 29 animals m^-2 of Cassiopea sp. can increase NH₄ concentrations in the water column by up to 26% over the course of a day. Since Cassiopea sp. can occur at high densities (> 100 animals m^-2), fully carpeting the bottom in some locations, this study also discusses the effects of population density and crowding on pore water release.