Figure 6

Examples of NH₄⁺ (a–c) and PO₄³⁻ (d–f) uptake rates of different species as a function of the external NH₄⁺ and PO₄³⁻ concentration. Species included are (a,d) the coral Madracis mirabilis, (b,e) turf algae, and (c,f) the cyanobacterium Lyngbya majuscula. NH₄⁺ and PO₄³⁻ uptake rates were calculated over 20 min time intervals during the nutrient uptake experiments. For turf algae and L. majuscula, the first 10 min of uptake was not included as they had a biphasic NH₄⁺ and PO₄³⁻ uptake. Data included specimens collected from both 5 and 20 m depth, and from uptake experiments performed at both low and high initial NH₄⁺ and PO₄³⁻ concentrations. Trend lines are based on linear regression (P < 0.05) forced through the origin. Error bars represent s.d. of the mean (n = 9). Results from the other species can be found in the Supplementary Figs S5 and S6.