Title: GROWTH HISTORY RECORDED IN SKELETAL STABLE ISOTOPES IN THE MESOPHOTIC PORITES CORAL FROM THE GULF OF EILAT, RED SEA

Abstract: Mesophotic coral ecosystems are found at depth below 30m. Due to its depth, the mesophotic zone is relatively protected from climatic and anthropogenic disturbance at the surface. Under relatively undisturbed conditions, mesophotic coral ecosystems may act as refugia. 　Owing to its depth, it has been difficult to observe mesophotic coral growth patterns and histories. Here we introduce geochemical approaches recording ocean environment for Porites coral growing from the mesophotic zone. Oxygen isotope provides sea temperature (ST) and salinity variability with distinct seasonal cycles. We used oxygen isotopes in coral carbonate skeleton to discuss coral growth histories in mesophotic zone. 　Two Porites corals were collected at sea surface and 50m depth from the Gulf of Eilat, the northernmost part of Red Sea. We applied skeletal oxygen and carbon isotopic analysis using stable mass spectrometry. Analytical results were compared with in-situ environmental data to discuss about difference of growth responses. 　These existed the difference of histograms of oxygen isotope record between predicted from ST and coral skeletons. The histogram of the mesophotic coral oxygen isotope records showed higher frequency of those recorded in summer than winter. This suggested a decrease or cessation of coral growth at mesophotic zone in winter. Usually, sea surface corals cease coral extension below 18ºC at high latitude. Comparison of coral growth history between sea surface and mesophotic zone revealed that the temperature threshold of coral growth varied in response to coral water depth.

Authors: Watanabe TK, Watanabe T, Eyal G, Loya Y

Presentation: Poster (#338)

Session: 29

Date: 06/21/16

Time: 18:15 - 19:45

Location: Poster/Exhibit Hall

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