Does enrichment by inorganic nutrients prevent bleaching in the coral Galaxea fascicularis exposed to high temperature

We examined whether increased concentration of ammonium or phosphate prevents bleaching in the coral Galaxea fascicularis exposed to a high temperature to test the hypothesis that bleaching occurs when cnidarian hosts fail to supply their symbiotic algae with sufficient inorganic nutrients. Isolated polyps of G. fascicularis were incubated at 32°C for 9 days either in filtered sea water (FSW), 100μM NH4Cl in FSW, or 10μM Na2PO4 in FSW. The density of zooxanthellae and areal concentration of chlorophyll decreased to about a half regardless of when inorganic nutrients were present and absent in the treatments. The present results suggest that the loss of zooxanthellae at a high temperature is not due to a reduction in the supply of inorganic nutrients to zooxanthellae by their host.