Long- and short-term carbon fluctuations in the Eastern Mediterranean during the late Holocene

A high-resolution record of carbon isotope changes during the late Holocene was obtained in core GA-112 from the easternmost Mediterranean. Over the past 3600 yr, a gradual ¹³C-depletion trend shown by both planktonic and benthic foraminifera corresponds to a global rise in atmospheric CO₂. The global and local trends suggest that aridification and biomass destruction in the Nile basin played a major role in the global CO₂ rise in the late Holocene. Superimposed on the general δ¹³C trend are four mirror-image cycles in δ¹³C of planktonic and benthic foraminifera. Higher planktonic δ¹³C values reflect periods of high productivity off the coast of Israel. Simultaneously, decrease in the benthic δ¹³C values occurred because of degradation of higher organic-matter fluxes to the sediment. Therefore, large differences between the two records indicate periods of high productivity. The Eastern Mediterranean productivity fluctuations respond to a periodical replenishment of nutrients to the mixed layer via Nile runoff. Historical data of the Nile flood fluctuations for the past ~1400 yr show a remarkable coincidence between high and low Nile floods and high and low Eastern Mediterranean productivity levels, which are correlated with the periodic monsoonal activity over the Nile headwaters.