DFAAs within undisturbed waters in One Tree Island lagoon ranged between 0 and 0.122 lM and mostly comprised serine and glycine. The total concentration of DFAAs in the water column was signi®cantly lower (undetectable) in microatolls that received 20 lM ammonium ions as opposed to the control microatolls (Fig. 3; ANOVA, F1,4 46.35, P < 0.0024). Pocillopora damicornis rapidly took up total DFAAs (Fig. 4) at rates ranging between 4.9 and 9.8 nmol N cm)2 h)1 (Table 1). The exception was a single colony of P. damicornis measured in the light in which there was an eux of amino acids. Rates were
also calculated per colony (range: 1.44 to 2.16 lmol N colony)1 h)1, ignoring the single outward ¯ux) and as a function of wet tissue weight (range: 0.15 to 0.66 lmol N g)1 h)1). Rates of DFAA uptake were higher in the dark (P < 0.05). Rates of uptake for individual amino acids ranged between 0.14 (tyrosine, light) and 0.98 nmol cm)2 h)1 (histidine, dark), and were generally similar between dierent amino acids (Fig. 5). The exception was tyrosine, which was taken up at rates that were consistently one-third to one-half that of the rates measured for the other amino acids (Fig. 5). There was no clear dierence between the uptake of amino acids belonging to acidic, neutral or basic classes.