Bacterial suspension feeding by coral reef benthic organisms

Abstract

The l~nkage between the pelagic microbial loop in coral reefs and reef benthic communities needs study in view of changing characteristics of trop~cal coastal seas. We conducted field experiments, using standard microbial techniques, to assess the uptake of natural water-borne bacteria (at natural densities, 0.4 to 0.6 X 106 cm-3) by 2 common Caribbean reef organisms, the scleractinian coral Madracis mirabilis and the colonial ascidian Trididemnum solidun1 The data show that these organisms are effective bactenal suspension feeders. Feeding rates of 0.75 to 1.07 X log bacterial cells 100 cm-2 h-' translate into a nitrogen input of 3 to 4 nmol N cm-2 h-' These values indicate that a large part of the nitrogen derived from particulate sources could be supplied by bacteria. We suggest that such efficient linkage between these reef organisms and the pelagic microbial communities explains the increasing/continued abundance of such benthic organisms on detenorating Caribbean reefs.