Mass‐transfer limitation of nutrient uptake by a wave‐dominated reef flat community

Abstract

Maximum rates of phosphate, nitrate, and ammonium uptake by a reef flat community were estimated from rates of frictional dissipation that were calculated from the attenuation of waves propagating over the Kaneohe Bay Barrier Reef flat. Time‐averaged flow speeds across the entire study area ranged from 0.08 to 0.22 m s−1. Observed decreases in wave energy fluxes and near‐bottom orbital velocities gave a mean estimate for the bottom friction coefficient (cf) of 0.22 ± 0.03. Friction coefficients were used to estimate nutrient mass‐transfer coefficients of 5–9 m d−1 for phosphate and 9–16 m d−1 for ammonium and nitrate. Wave heights offshore of Kaneohe Bay were also used to estimate an annual phosphate mass‐transfer coefficient of 8 ± 2 m d21. This value is similar to a published value of 9 ± 2 m d−1 that was determined from measured changes in phosphate concentrations across the reef flat. We conclude that rates of phosphate uptake by the Kaneohe Bay Barrier Reef flat community are occurring near the limits of mass transfer.