Nitrification in reef corals

Abstract

N-Serve blockage of NH4+ oxidation showed that nitrification in reef corals is quantitatively important. Average NO3- production was 9.4+-6.0 nmol (mg coral tissue N)-1 h-1 (mean +- 1 SE; n = 12), equivalent to 17% of the NH4+ consumption and 21% of the uptake by zooxanthellae showing an effective competition for NH4+ by nitrifiers. NH4+ utilization rates were equal to inorganic N production rates, and NO3- production rates were equal to NO3- uptake rates by zooxanthellae, suggesting close coupling between these processes. Density of nitrifying bacteria associated with living corals may vary from 4 to 260 x 10power3 cells (mg coral tissue N)power-1.