Effect of Ammonium-supplemented Seawater on Glutamine Synthetase and Glutamate Dehydrogenase Activities in Host Tissue and Zooxanthellae of Pocillopora damicornis and on Ammonium Uptake Rates of the Zooxanthellae

Abstract

Host glutamine synthetase activity decreases in Pocillopora damicornis (Linnaeus) following exposure of the coral to seawater containing elevated ammonium (20 uM). Zooxanthellae isolated from these corals exhibited lower ammonium uptake capacity and glutamine synthetase activity compared with those from the control corals. Ammonium concentration of the surrounding seawater had no effect on the NADPH-dependent glutamate dehydrogenase activity in the host.