Coccolithophore assemblages from Gulf of Aqaba sediments and their implications for climate change

Abstract

Gulf of Aqaba exhibits a nearly close marine system characterized with oligotrophic conditions which makes it potential for phytoplankton flourishing. One hundred and ninety two smear slides, from seven sites in Gulf of Aqaba, collected during the OceanX expedition, were prepared for coccolithophores identifications and paleoecological investigation. The smear slides were studied under polarized microscope with 1500x magnification. Coccolithophores assemblages are extremely abundant in well preserved conditions allowing for clear identifications and exact assessment of climatic change based on the paleoecological study. Gephyrocapsa group, Emiliana Group, Helicosphaera spp, Reticulofenestra spp and Coccolithus spp, Pontosphaera spp, Braarudosphaera sp and Umbilicosphaera spp were found in high numbers through all the cores. Results showed that the fluctuations in numbers of cold-preference (Gephyrocapsa group) versus warm-preference coccolithophores (Emiliana Group) led to track the change in climate periodically. Emiliana Group was the most abundant genus through all cores indicating to long term of warming. The significance increase in numbers of Gephyrocapsa oceanica, Gephyrocapsa muellerae, Gephyrocapsa ericsonii, and Calcidiscus leptoporus in some samples relatively to Emiliana Group is revealing a period of cold environment dominated the Gulf during the Pleistocene time. This clear shift in the climatic conditions can be correlated easily in the seven sites. The high numbers of coccolithophores which reached to 20 specimens per field of view implying that the primary production system in Gulf of Aqaba is still working fine and can save the whole food chain system in the Gulf.