Summary of Abstract Submission

Abstract Submission No. IO50-02-0019PresentationPoster

CORAL REEFS VERSUS PLANKTON CALCIFICATION RATES IN THE RED SEA AND WESTERN INDIAN OCEAN

Zvi Steiner*1, Jonathan Erez1, Aldo shemesh2, Ruth Yam2, Amitai Katz1, Boaz Lazar1

1 Hebrew University, Israel
2 Weizmann Institute of Science, Israel

ABSTRACT :

Surface water was collected in 50 stations during a cruise from the northern Red Sea to the Seychelles and analyzed for chemical and isotopic composition. The calcification rate in the Red Sea basin was estimated from surface water total alkalinity depletion along their axial flow, using the water flux in the strait of Bab el Mandeb. The relative role of calcareous plankton and coral reefs in CaCO3 precipitation was calculated by fitting a Rayleigh distillation model to the observed increase of the surface water Sr/Ca ratios. We estimate the total net rate of carbonate precipitation in the Red Sea to be 7.30.4∙10^10 kg∙y-1 of which calcareous plankton precipitated 805% while the flourishing coral reefs surrounding the Red Sea coasts precipitated 205%. In the Gulf of Aden corals precipitated 137% of the total CaCO3 and in the northwestern Indian Ocean coral contribution to CaCO3 precipitation was below our detection limit. Surface seawater Mg was depleted along the Red Sea, possibly due to mixing with hot brines. This study demonstrates that changes in major ion composition on a basin scale can be used to estimate CaCO3 precipitation rates and establish the relative role of the main marine communities in the production of carbonates.