Coral reefs are among the most sensitive ecosystems in the world. When the corals are subjected to stress is bleached, and a large proportion die. They can recover, but it takes upwards of a decade.
the Corals can be bleached by, for example, lack of nutrition, of light or of the water becomes too warm.
Among other things, when väderfenomenet El Niño is in progress is heated parts of the tropical seas up so sharply that many rev can hit hard. So it was, for example, in 1998, and now no later than 2016-2017. In klimatforskarnas scenarios such värmeepisoder to get denser in the future.
new study published in the scientific the journal Nature analyzed the cases of coral bleaching over the past two decades. The study shows in particular two things that suggest that the resilience of the corals might be larger than previously thought.
For the first, it indicates that there is more fading between 15 and 20 latitude than closer to the equator, where the diversity of species among the corals is greatest. It contradicts the previous regional studies from the south pacific.
One theory is that just artvariationen provides a greater resistance in itself. Another is that the reefs near the equator may be more resistant to värmeökningar because the water temperature which is a little higher in the starting position. There is no evidence that the rise in temperature during the harmful värmeepisoderna would be higher between latitude 15 and 20 than at the equator.
Other paleoekologiska studies have shown that ekvatornära areas in general are more resistant to exclusion of species when the climate quickly changed, according to the research team.
in the group, where the Shannon Sully at the Florida technical university has been the lead author, concluded that the corals seem to have an ability, to some extent, adapt to higher temperatures.
the Study shows although, like other surveys, to coral bleaching has been occurring in ever more frequent in recent years. But when the two last decades were compared with each other showed that bleaching occurred at a higher temperature during the last decade (the period 2007-2017) than during the preceding quarter (1998-2006). During the latter period was the critical limit to 28.7 degrees and in the previous was the of 28.1 degrees.
It suggests that the reefs recovered carries with it a kind of memory of the previous dramatic event, and that the remaining population adjusted up their toleranströskel.
”heat-sensitive genotypes may have been reduced in number and / or adapted so that the remaining korallpopulationen now has a higher temperaturtröskel for bleaching,” the researchers write in their report.
Corals in areas with a large natural fluctuation in the water temperature also proved to be more resilient than corals in areas that normally have a more even temperature over the year.
the Researchers are careful to point out that it is not in any way expect that an unexpectedly high resistance means that the corals can handle the värmeökningar at any time.
on the Contrary, they emphasize as well as others to measures against global warming is crucial for coral survival. But the new knowledge can be important to have with when you should make the decision to protect the coral reefs.
another research report in the same journal, which warns that the Great barrier reef outside of Australia is not ”too big to collapse”, as sometimes has been claimed.
In this study, the effects of the major El Niño bleaching 2016-2017 been reviewed, and it turned out that not only do many older corals died, but also a significant number of the youngest, which raises concerns about the ability to recovery between blekningarna may not be large enough.
For a couple of years ago, a large meta-study led by, among others, the International union for conservation of nature and united nations environmental bodies concluded that the extensive koralldöden other islands in the caribbean was mainly due to two things: over-fishing by local fishermen and diseases. The importance of värmeepisoder was significantly less than the researchers in the study had expected.
Read more: the Caribbean's reefs could be saved,