Notes on primary productivity of coastal waters in the Gulf of Elat (Red Sea)

The following parameters were measured during May 1976 along the coasts of the Gulf of Elat (or: Gulf of Aqaba): phytoplankton species composition, chlorophyll content and photosynthetic production; weight of suspended particles and nutrient concentration; chlorophyll content of the sediments. The study areas were coral reefs of the northern part of the Gulf and a mangrove pool south of it. Phytoplankton characteristics and nutrient levels are those of oligotrophic waters. However, the sediments harbour such an abundant plant biomass that in coastal waters per m² surface area, there is several hundred times more chlorophyll in the sand than in the plankton. Reasons why both the mangrove and the coral reef may exhibit the same trends are discussed.