Nutrient levels in sea and river water along the ‘Coral Coast’ of Viti Levu, Fiji

Abstract

Nutrient (nitrate and phosphate) levels potentially damaging to coral reefs have been detected at several sites along the Coral Coast of Viti Levu, Fiji. Nutrient concentrations were determined using standard techniques on an autoanalyser capable of measuring to sub-micromolar levels. The mean nitrate level for 34 seawater samples was 1.69 mM and the mean phosphate level was 0.21 mM which exceeded levels considered to be harmful to coral reef ecosystems (>1.0 mM N, >0.1 mM P). It is proposed that these elevated nutrient levels coupled with overfishing of herbivore species have contributed to the recent widespread growth of macro -algae species along this coast. Nutrient levels were highest at sites located near hotels and other populated sites. At sites not significantly influenced by human activity, levels were comparable to that of non-polluted sites elsewhere in Fiji. Concentrations of nutrients in rivers along the coast were generally higher than in seawater. Urgent action is needed at community, regional and government levels to try and reduce the nutrient inputs to this coast.