Nitrification in reef corals

N‐Serve blockage of NH 4 + oxidation showed that nitrification in reef corals is quantitatively important. Average NO 3 − production was 9.4±6.0 nmol (mg coral tissue N) −1 h −1 (mean ± 1 SE; n = 12), equivalent to 17% of the NH 4 + consumption and 21% of the uptake by zooxanthellae showing an effective competition for NH 4 + by nitrifiers. NH 4 + utilization rates were equal to inorganic N production rates, and NO 3 − production rates were equal to NO 3 − uptake rates by zooxanthellae, suggesting close coupling betweenpocesses. Density nitrifying bacteria associated with living corals may vary from 4 to 260 × 10 3 cells (mg coral tissue N) −1 .