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Insights into Coral Resilience Following a Major Bleaching Event

Paper Reviewed
Schoepf, V., Jung, M.U., McCulloch, M.T., White, N.E., Stat, M. and Thomas, L. 2020. Thermally variable, macrotidal reef habitats promote rapid recovery from mass coral bleaching. Frontiers in Marine Science 7: 245, doi: 10.3389/fmars.2020.00245.

Increasing efforts have been expended to assess both the vulnerability and resilience of natural ecosystems to disturbances predicted to occur from climate change. The latest work to dive into this topic -- at least for coral reefs -- comes from the research team of Schoepf et al. (2020), who examined macrotidal coral recovery following a 2016 mass bleaching event in the Kimberley region, NW Australia.

Coral community health surveys were conducted before, during and 6 months after the bleaching event using an integrated ecological, physiological and genetic approach at two reef habitats with distinct environmental conditions at low tide, including (1) an environmentally extreme and thermally-variable intertidal pool where corals regularly get exposed to air and (2) a thermally-moderate subtidal reef that remains submerged (average depth of 4 meters) with water. And what did those surveys reveal?

Results indicated strong differences in survival and recovery percentages between the intertidal and subtidal reef locations. In particular, Schoepf et al. report "the intertidal coral community suffered 72% bleaching (± 5 SE; moderately and severely bleached corals combined) but mostly recovered within 6 months with little mortality (9% ± 5 SE)." However, they add, "in stark contrast, the large majority of the bleached subtidal coral community ultimately died (71% ± 11 SE) although being separated by only 200-300 m and experiencing a similar though slightly higher degree of bleaching (81% ± 4 SE versus 72% ± 5 SE for intertidal." What is more, they say "the intertidal community fully recovered to its prebleaching configuration within 6 months, whereas the adjacent subtidal suffered extensive mortality (68% loss of live coral cover)." Thus, corals living in the more extreme and thermally-variable intertidal habitat experienced a near complete recovery six months after the bleaching event whereas corals from the thermally-moderate subtidal reef did not.

In discussing their findings, Schoepf et al. write that the differential recovery responses observed among the intertidal and subtidal reef corals "highlight the important role of tidally controlled temperature variability in promoting coral recovery capacity." Consequently, they conclude "shallow reef environments characterized by strong environmental gradients may generally promote coral resilience to extreme climatic events," adding "thermally variable reef environments may therefore provide important spatial refugia for coral reefs under rapid climate change." And that suggests coral reefs are not headed toward extinction any time soon!

Posted 19 August 2020