Kiritimati's reefs are bleaching On October 8th 2015 NOAA declared that the world's 3rd ever global coral bleaching event is underway. Our field site, Kiritimati (Christmas) atoll in the central equatorial Pacific (northern Line Islands) sits at the epicentre of predicted bleaching impacts. Kiritimati has been at the highest bleaching alert level (Alert 2) for several months now and is predicted to stay in this state for several more months.
In July 2015 the Baum Lab team completed our 10th expedition to Kiritimati. Led by PhD student Danielle Claar, the team documented the beginning impacts from the massive El Niño that is underway.
Our sites are located along the 10 meter isobath, and are comprised primarily of a mixed scleractinian coral community composition of Porites, Montipora, Hydnophora, Favia, Favites, Platygyra, Montastrea, Pocillopora and several other less abundant hard corals (as well as leather corals and zoanthids). In July 2015, coral bleaching was approximately 30% overall severity (at 10m depth). As previously reported by other groups, bleaching incidence and severity was observed to be taxon-specific. The most impacted taxa on Kiritimati in July were Platygyra, Favia stelligera, corymbose Acropora, Fungia, Pavona and Montastrea. Bleaching or significant color paling was also commonly observed for most Favids (e.g. Favia matthai, Favites pentagona, etc), and about half of Montipora and Hydnophora colonies. Poriteshealth varied by site, with some sites exhibiting more resistant colonies (no bleaching or very light paling) and others exhibiting more susceptible colonies (significant paling and/or bleaching). Shallow corals (2-5m) are undergoing more intense bleaching, which we estimate to be 40-80%, dependent on site and coral composition of the site. Acroporids are faring particularly badly, although some individual colonies have shown remarkable resistance to bleaching stress so far. Surprisingly, one of the least affected taxa was Pocillopora (primarily P. eydouxi), which showed essentially no bleaching at any of our surveyed sites. Although we observed bleaching at all of our 19 surveyed sites, there were no visible “newly dead” colonies.
We will be conducting additional field seasons in the spring and summer of 2016 to follow coral community bleaching and mortality trajectories over the next year. Contact Julia (baum 'at' uvic.ca) or Danielle (dclaar 'at' uvic.ca) for more information. For more information about our fieldwork on Kiritimati: kiritimati.weebly.com/ Follow us on Twitter: @baumlab and @ClaarDanielle