Proliferation and demise of deep-sea corals in the Mediterranean during the Younger Dryas

Uranium-series and radiocarbon ages are reported for deep-sea corals Madrepora oculata, Desmophyllum dianthus, Lophelia pertusa and Caryophyllia smithii from the Mediterranean Sea. U-series dating indicates that deep-sea corals have persisted in the Mediterranean for over 480,000 years, especially during cool interstadial periods. The most proli fi c period of growth however appears to have occurred within the Younger Dryas (YD) period from 12,900 to 11,700 years BP followed by a short (~330 years) phase of post- YD coral growth from 11,230 to 10,900 years BP. This indicates that deep-sea corals were proli fi c in the Mediterranean not only during the return to the more glacial-like conditions o the YD, but also following the rapid deglaciation and transition to warmer conditions that followed the end of the YD. Surprisingly, there is a paucity Last Glacial Maximum (LGM) coral ages, implying they were largely absent during this period when cold-water conditions were more prevalent. Radiocarbon ages show that the intermediate depth waters of the Mediterranean generally had Δ 14 C compositions similar to surface waters, indicating that these waters were extremely well ventilated. The only exception is a narrow period in the YD (12,500 ?100 years BP) when several samples of Lophelia pertusa from the Ionian Sea had Δ 14 C values falling signi fi cantly below the marine curve. Using a re fi ned approach, isolation ages (τ isol ) of 300 years to 500 years are estimated for these intermediate (800-1000 m) depth waters relative to surface marine waters, indicating a reduction or absence of deep-water formation in the Ionian and adjacent Adriatic Seas during the YD. Contrary to previous fi ndings, we fi nd no evidence for widespread intrusion of low Δ 14 C Atlantic waters into the Mediterranean. Proli fi c growth of deep-sea corals in the Mediterranean ended abruptly at ~10,900 years BP, with many of the coral-bearing mounds on the continental slopes being draped in a thin veneer of mud. Their demise is attributed to a number of factors, including the direct loss of habitat due to high sedimentation that accompanied glacial meltwater pulses, together with rising temperatures that would have fi nally pervaded the deeper water of the Mediterranean following the onset of Holocene warming