Uptake and release of nitrogen compounds in coral reef and seagrass, Thalassia hemprichii (Ehrenb.) Aschers., bed sediments at Lizard Island, Queensland

Abstract

The interstitial water in sediments from coral reef areas and seagrass (T. hemprichii) beds at Lizard Island contained 6-48 µmol l^-1 ammonium, 4-7 µmol I^-1 nitrate plus nitrite, and 1 .5-2.5 µmol I^-1 soluble reactive phosphorus. Concentrations of total dissolved primary amines were an order of magnitude higher in sediments from seagrass beds (about 140 µmol l^-1) than from coral reef areas (about 10 µmol I^-1). Ammonium-nitrogen was produced at rates of 0.7,6, and 10 nmol g^-1 h^-1 in sediments from a bare beach, reef flat and seagrass bed, respectively. Added glycine and nitrate were also rapidly metabolized by microbes in the sediment (3 to > 5 nmol g^-1 h^-1).