by S. Xu et al., December 2017, in AGU1000Biogeosciences
Coral bleaching is becoming a serious issue for coral reefs under the stress of global warming. However, whether it has occurred in the past in times of thermal stress remains unclear. Moreover, an understanding of historic coral bleaching events would greatly improve our insight into the adaptive capabilities of corals under such stresses. It is known that Porites corals, a massive coral, have relatively high levels of symbiotic zooxanthellae and a strong thermal tolerance when compared with most other corals (and particularly branched corals). Thus, growth hiatuses and/or mortality surfaces of fossil Porites may be used to indicate past ecological or environmental stress events, such as severe bleaching. In this study, monthly geochemical and isotopic environmental proxies of four fossil Porites corals with well‐preserved growth hiatuses and mortality surfaces (aged 3,800–4,200 years before 2013 A.D.), collected from Wenchang fringing reef, Hainan Island, Northern South China Sea were analyzed. Specifically, the Sr/Ca, δ18O, and δ13C were measured with a monthly resolution for each sample.
By taking a closer look, scientists find resilience in face of heat stress.
Coral reef bleaching is stark evidence of the damage being inflicted by global climate change on marine ecosystems, but a research team has found some cause for hope. While many corals are dying, others are showing resilience to increased sea surface temperatures, pointing to possible clues to the survival and recovery of these vitally important aquatic habitats (…)
Coral reefs are facing no shortage of threats including ocean acidification, overfishing, plastic pollution, and rising temperatures. Sea surface temperatures have been climbing on average for over a century, and ocean heat waves—which can trigger coral bleaching events—are becoming more common and severe. Scientists have long worried that as coral-killing spikes in temperature become more frequent, corals won’t have enough time to recover between bleaching events and will ultimately go extinct. But a new paper, published today in PLoS Genetics, suggests that corals might be able to adapt to another century of warming.
Recent findings suggest that episodes of very rapid sea-level rise of about 20m in less than 500 years occurred in the last deglaciation, caused by periods of catastrophic ice-sheet collapse as the Earth warmed after the last ice age about 20,000 years ago.
Lead author, PhD candidate at the University of Sydney, Kelsey Sanborn, has shown this sea-level rise event was associated with “drowning” or death of coral reefs in Hawaii.
