MEPS 608:133-147 (2019)  -  DOI: https://doi.org/10.3354/meps12758

ABSTRACT: Sponges can have powerful effects on ecosystem processes in shallow tropical marine ecosystems. They drive benthic-pelagic coupling by filtering dissolved and particulate organic matter from the water column, alter water chemistry in association with their symbiotic microorganisms, and increase habitat structural complexity. Anthropogenic degradation of coastal waters is widespread and can reduce the density and diversity of foundation species such as sponges, potentially diminishing their contributions to ecosystem processes. We used a novel mesocosm design that minimized artifacts associated with traditional single-species and closed-system filtration experiments to examine the effects of water turnover and sponge biomass on water-column properties. Using a 3-factor, fully-crossed design, we manipulated water turnover and the biomass of 10 sponge species common in Florida Bay, Florida (USA), and measured the effects of their feeding on concentrations of nutrients (nitrogen, carbon, and phosphorus) and plankton (measured as chl a and bacterioplankton). High sponge biomass and low water turnover greatly reduced chl a, ammonium, and dissolved organic carbon (DOC) in the water and increased concentrations of nitrites, nitrates, and phosphates. Sponge species identity had idiosyncratic effects on water-column constituents, especially with respect to the influence of sponges on chl a, DOC, and ammonium. This study demonstrates the importance of sponge biomass and species-specific filtration on nutrient cycling and highlights how changes in the abundance and diversity of sponges in coastal ecosystems can drastically alter water-column properties.

KEY WORDS: Community · Density · Ecosystem function · Florida Bay · Sponge · Flow regime