Title: BLEACHING AND DEPTH REFUGES IN THE EASTERN PACIFIC DURING THE STRONG 2015-2016 EL NIÑO

Abstract: The ongoing 2015-16 El Niño is third severe El Niño to impact reefs of the eastern tropical Pacific in the last 35 years. In the two previous events communities of the hydrocoral Millepora intricata were extirpated from shallow water but survived in deeper water (> 12 m depth), facilitating shallow water recovery between disturbances. This supported the deep reef refugia hypothesis, which posits that cooler temperatures and other physical characteristics buffer corals in deep environments. However, this evidence lacked supporting oceanographic observations, and recent evidence from Caribbean mesophotic reefs suggests that thermal tolerance is set by the mean warmest conditions, allowing bleaching even when conditions are cool relative to shallow reefs. To understand the oceanographic and biological processes that might support or inhibit a depth refuge, we are studying the response of six species of stony coral at depths of 5 – 30 m in Panama and the Galápagos. By August 2015, M. intricata had once again been nearly extirpated from shallow water study sites in Panama and other species showed paling, bleaching or early stages of mortality. Below 15 m depth temperatures were cooler and corals were unaffected. From the ultimate response of corals and the physical environment to be sampled during the predicted spring 2016 thermal maximum, we will be able to determine what physical factors support a bleaching refuge. These studies are critical to assessing the importance of refugia in preventing regional and global coral extinction in a warmer future.

Authors: Smith TB, Baker AC, Brandtneris VW, Glynn PW, Manzello DP, Maté JL, McGillis WR, Palacio A, Fong P

Presentation: Oral

Session: 28A

Date: 06/20/16

Time: 14:00

Location: 308 A/B

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