Title: TEMPERATURE VARIATION AND CORAL COMMUNITY STRUCTURE OF MESOPHOTIC REEF ECOSYSTEM IN PALAU

Abstract: Tropical mesophotic reef ecosystems are receiving attention in recent years among coral reef researchers due to their potential as refugia for shallow coral reef ecosystems. Light has been shown to be a limiting factor of coral community in mesophotic reefs while temperature was suggested as not a significant abiotic factor. In light of the prediction of severe El Nino event for 2015/16, seawater temperature variation and its effects on coral community in mesophotic reefs can fill the critical gap in knowledge in the physical-biological link between mesophotic reefs and their shallow counterparts. An on-going seawater temperature monitoring in several mesophotic reef ecosystems in Palau has been carried out since year 2014. Temperature loggers are being deployed at every 5-m depth interval up to 40 m depth in the outer reefs in Palau. Temperatures as low as 19 to 22 degree Celsius have been recorded in depths between 30 to 40 meters with daily fluctuation ranged from 8 to 10 degree Celsius. Extent of cool water pulsing was recorded as shallow as 15 m depth. Seasonal upwelling occurred at higher frequency between January to June resulted in bigger daily and monthly temperature fluctuations in deep water compared to other months. This indicates that corals in mesophotic reefs in Palau are constantly being subjected to big temperature variations. Additional information such as reef community, hydrodynamic processes, light availability, nutrient flux is needed to provide comprehensive baseline data of mesophotic reefs in Palau.

Authors: Yuen YS, Nakamura T, Rengiil G

Presentation: Oral

Session: 54

Date: 06/21/16

Time: 10:30

Location: 303 A/B

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