Contrasting Patterns of Coral Bleaching Susceptibility in 2010 Suggest an Adaptive Response to Thermal Stress

Background: \ud Coral bleaching events vary in severity, however, to date, the hierarchy of susceptibility to bleaching among coral taxa has been consistent over a broad geographic range and among bleaching episodes. Here we examine the extent of spatial and temporal variation in thermal tolerance among scleractinian coral taxa and between locations during the 2010 thermally induced, large-scale bleaching event in South East Asia.\ud \ud Methodology/Principal Findings: \ud Surveys to estimate the bleaching and mortality indices of coral genera were carried out at three locations with contrasting thermal and bleaching histories. Despite the magnitude of thermal stress being similar among locations in 2010, there was a remarkable contrast in the patterns of bleaching susceptibility. Comparisons of bleaching susceptibility within coral taxa and among locations revealed no significant differences between locations with similar thermal histories, but significant differences between locations with contrasting thermal histories (Friedman = 34.97; p,0.001). Bleaching was much less severe at locations that bleached during 1998, that had greater historical temperature variability and lower rates of warming. Remarkably, Acropora and Pocillopora, taxa that are typically highly susceptible, although among the most susceptible in Pulau Weh (Sumatra, Indonesia) where respectively, 94% and 87% of colonies died, were among the least susceptible in Singapore, where only 5% and 12% of colonies died.\ud \ud Conclusions/Significance: \ud The pattern of susceptibility among coral genera documented here is unprecedented. A parsimonious explanation for these results is that coral populations that bleached during the last major warming event in 1998 have adapted and/or acclimatised to thermal stress. These data also lend support to the hypothesis that corals in regions subject to more variable temperature regimes are more resistant to thermal stress than those in less variable environments

New Seeding Approach Reduces Costs and Time to Outplant Sexually Propagated Corals for Reef Restoration

The use of sexually propagated corals is gaining popularity as an approach for reef restoration. However, manually attaching substrates with recently settled corals to the reef using binding materials is both time-consuming and expensive, limiting the use of this technique to small spatial scales. We present a novel approach whereby young corals are ‘seeded’ on the reef without the need for manual attachment to the benthos. We tested two tetrapod-shaped concrete substrates (7.9 and 9.8 cm in diameter) on which coral larvae were settled. The tetrapods were efficiently deployed by wedging them in reef crevices, in 1.5 to 7% of the time required for traditional outplanting techniques. Seeding tetrapods was most effective in reefs with moderately to highly complex topographies, where they rapidly became lodged in crevices or cemented to the benthos by encrusting organisms. After one year, average recruit survival was 9.6% and 67% of tetrapods still harboured at least one coral colony, and overall, this approach resulted in a 5 to 18 fold reduction in outplanting costs compared to common outplanting methods. This seeding approach represents a substantial reduction in costs and time required to introduce sexually propagated corals to reefs, and could possibly enable larger scale reef restoration