Mass-transfer-limited nitrate uptake on a coral reef flat, Warraber island, Torres Strait, Australia

Previous research has identified a relationship between the rate of dissipation of turbulent kinetic energy, e, and the mass-transfer-limited rate of uptake by a surface, herein called the epsilon(1/4) law, and suggests this law may be applicable to nutrient uptake on coral reefs. To test this suggestion, nitrate uptake rate and gravitational potential energy loss have been measured for a section of Warraber Island reef flat, Torres Strait, northern Australia. The reef flat section is 3 km long, with a 3 m tidal range, and on the days measured, subject to 6 in s(-1) tradewinds. The measured nitrate uptake coefficient, S, on two consecutive days during the rising tide was 1.23 +/- 0.28 and 1.42 +/- 0.52x 10(-4) m s(-1). The measured loss of gravitational potential energy across the reef flat, AGPE, on the same rising tides over a 178 m section was 208 +/- 24 and 161 20 kg m(-1) s(-2). Assuming the AGPE is dissipated as turbulent kinetic energy in the water column, and using the epsilon(1/4) law, the mass-transfer-limited nitrate uptake coefficient, S-MTL, on the two days was 1.57 +/- 0.03 and 1.45 +/- 0.04x 10(-4) M s(-1). Nitrate uptake on Warraber Island reef flat is close to the mass-transfer limit, and is determined by oceanographic nitrate concentrations and energy climate.