Title: THERMAL-STRESS REFUGIA FOR CORALS: OBSERVATIONS IN MESOPHOTIC COMMUNITIES OF APO REEF, PHILIPPINES

Abstract: On top of local scale coral mortalities, climate change induced mass coral bleaching has alarmingly reduced reefs worldwide over the last decades. Coral bleaching, which is primarily caused by anomalous changes in sea surface temperature and irradiance, is commonly reported for euphotic reefs (<20 m) while still generally viewed as less prevalent in mesophotic reefs (≥30 m). However, more studies are needed to determine whether mesophotic coral communities are indeed less susceptible to bleaching. In May 2015, we studied the prevalence of bleaching in coral communities at shallow (~5 m) and mesophotic reefs (~30 m) at three sites in Apo Reef (Mindoro), which at the time of study was in the 'Bleaching Watch' level of NOAA's Coral Reef Watch Program. Based on in situ measurements, sea surface temperatures of the shallow reefs were 2ºC higher than the mesophotic reefs in all sites. Bleaching occurred in only one of three sites. A shallow reef of this site registered 31ºC and had higher bleaching prevalence among Acropora corals; acroporids were however uncommon at the mesophotic reef. Seriatopora corals also had higher bleaching prevalence at the shallow than at the mesophotic reef. These initial results suggest that deeper sites may serve as refugia for coral communities from thermal stress, and warrants further monitoring of more sites, especially in relation to predicted El Niño-associated sea surface temperature anomalies. Studies on genetic connectivity and other ecological factors between shallow and deep reefs may provide insights on the resilience of reefs in the face of thermal stress events.

Authors: Cabaitan PC, Cabactulan DC, Olavides RD, Siringan FP, Villanueva RD, Da-anoy JP

Presentation: Oral

Session: 29

Date: 06/22/16

Time: 17:45

Location: 308 A/B

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