Microbial regeneration of ammonium in the water column of Davies Reef, Australia

Abstract

Regeneration was highest inside a patch reef followed by reef flat, lagoon and fore-reef. Bacteria and heterotrophic nanoplankton accounted for 40 to 88% of the NH super(+)d4 regenerated in 208 mu m filtered water. There was a trend of increasing importance of these organisms as water passed from the fore-reef, across the reef flat, and into the lagoon and patch reef areas. Remineralization was highest where water was in most intimate contact with the reef benthos. A first approximation of the relative importance of bacteria versus heterotrophic nanoplankton in NH super(+)d4 regeneration, suggested that suspended bacteria were about an order of magnitude more important than nanoplankton. Long biologically-mediated turnover times of NH super(+)d4 (21 to 154 h) suggest a greater importance of physical processes.