Distribution and Diversity of Coccolithophores in Surface Sediments of the Northern Red Sea: Coccolith Accumulation in Brine Pools and Observation of Productivity

A quantitative analysis of coccoliths is presented in 18 core-top samples ranging between 26 degrees N and 21 degrees N and covering two major deep brine pools in the northern part of the Red Sea. Non-brine sites are characterized by rich coccoliths that may reach up to 3.31 x 10(9) coccoliths/g made by 22 species, whereas brine sites of Shaban and Kebrit Deeps with additional two non-brine sites are characterized by a decline in coccoliths/g (3.25 x 10(8) coccoliths/g), Shannon diversity, CaCO3(%), and high TOC (%). Carbonate dissolution, inferred by qualitative observation and quantitative indices, was only observed at one brine site GeoB7828 in Kebrit Deep. This suggests that the decline in coccolith assemblages may not entirely be attributed to carbonate dissolution. The major decline, however, is probably related to the suspension of fecal pellets and marine aggregates containing delicate coccolith shields within a nepheloid layer and subsequently grazed by zooplankters in which reduced the numbers of coccolith that reached the bottom of the brine sites, or alternatively a deep-sea flow current that carried and remobilized some suspended particles outside the brine pool. Latitudinal fluctuations of eutrophic/oligotrophic coccoliths suggest profound trophic changes in the photic zone in the northern part of the Red Sea.C. braarudii,a valuable nutrient-indicator species is here reported for the first time, along withG. oceanica, H. carterias well as biogenic opal dominating the assemblage between 26 degrees N and 24 degrees N, suggesting elevated nutrient conditions and supporting recent high chl-arecords, whereas areas between 21 degrees N and 23 degrees N lie under oligotrophic conditions due to the presence ofU. sibogae,U. tenuis,R. clavigera,F. profunda, andS. pulchra.

Automated summary

The study demonstrates a general decline in coccolith abundance in deep brine pool sites in the northern Red Sea, potentially related to carbonate dissolution, suspended particles, and deep-sea flow currents. It also highlights areas with elevated nutrient conditions supporting diverse coccolith assemblages, contrasting with oligotrophic conditions in other regions.