Retention efficiencies of the coral reef sponges Aplysina lacunosa, Callyspongia vaginalis and Niphates digitalis determined by Coulter counter and plate culture analysis

Sponges are the dominant organisms on many coral reefs and through feeding they may greatly reduce the concentration of suspended food particles. Retention efficiencies of the tubular sponges Aplysina lacunosa, Callyspongia vaginalis and Niphates digitalis were examined on a coral reef located in the Florida Keys. Replicate ambient and exhalant water samples were collected in situ from individuals of each species and analysed using two methods. Retention efficiencies of suspended particles (0.75-18 mu m) examined using Coulter counter analysis were similar among the three sponge species, averaging 86%. For all sponges, particle retention decreased as particle size increased from 0.7 to 18 mu m. Water samples plated on to Marine Agar produced 54 microbial types. Retention efficiencies of culturable microbes were similar among the three species, averaging 82%. This study suggests that the coral reef sponges Aplysina lacunosa, Callyspongia vaginalis and Niphates digitalis play an important role in the transfer of energy between the pelagic and benthic environments.