Nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse

Terrestrial runoff after heavy rainfall can increase nutrient concentrations in waters overlying coralreefs that otherwise experience low nutrient levels. Field measurements during a runoff event showed asharp increase in nitrate (75-fold), phosphate (31-fold) and ammonium concentrations (3-fold) in watersoverlying a fringing reef at the island of Curaçao (Southern Caribbean). To understand how benthicreef organisms make use of such nutrient pulses, we determined ammonium, nitrate and phosphateuptake rates for one abundant coral species, turf algae, six macroalgal and two benthic cyanobacterialspecies in a series of laboratory experiments. Nutrient uptake rates differed among benthic functionalgroups. The filamentous macroalga Cladophora spp., turf algae and the benthic cyanobacteriumLyngbya majuscula had the highest uptake rates per unit biomass, whereas the coral Madracis mirabilishad the lowest. Combining nutrient uptake rates with the standing biomass of each functional groupon the reef, we estimated that the ammonium and phosphate delivered during runoff events is mostlytaken up by turf algae and the two macroalgae Lobophora variegata and Dictyota pulchella. Our resultssupport the often proposed, but rarely tested, assumption that turf algae and opportunistic macroalgaeprimarily benefit from episodic inputs of nutrients to coral reefs