Some reef-building corals have genetic variants necessary to tolerate warm waters, according to a new study co-led by Dr Line Bay from the Australian Institute of Marine Science and Dr Groves Dixon from the University of Texas at Austin. The discovery has implications for many reefs threatened by global warming and shows for the first time that mixing corals from different latitudes may boost reef survival.
Corals along the Northern part of the Great Barrier Reef. Image credit: Line K Bay / Australian Institute of Marine Science.
In their study, Dr Bay, Dr Dixon and co-authors crossbred reef-building corals Acropora millepora from two locations in Australia with five degrees of latitude between them – Princess Charlotte Bay and Orpheus Island.
They exposed the corals’ larvae to increasingly warm temperatures for long periods of time, and then analyzed the genes of the surviving individuals.
Their results, published online in the journal Science, reveal that the more heat-tolerant corals from Princess Charlotte Bay produced larvae that were ten times more likely to survive heat exposure than the larvae of the less heat-tolerant Orpheus Island corals.
Furthermore, the scientists show that when corals from Princess Charlotte Bay cross with Orpheus Island corals, they can pass their tolerance for heat on to their offspring.
They identified differences in the corals’ gene expression that appear to be heritable and related to heat-tolerance.
The study suggests that corals’ tolerance for temperature, which varies depending upon latitude, is passed down from generation to generation – and that far-flung populations of coral did not simply acclimate to their different environments but instead inherited their ability to thrive in higher temperatures.
“We show an up-to-ten-fold increase in odds of survival of coral larvae under heat stress when their parents come from a warmer lower-latitude location,” the scientists said.
“Elevated thermal tolerance was associated with heritable differences in expression of oxidative, extracellular, transport, and mitochondrial functions that indicated a lack of prior stress. Moreover, two genomic regions strongly responded to selection for thermal tolerance in interlatitudinal crosses.”
“Our research found that corals do not have to wait for new mutations to appear. Averting coral extinction may start with something as simple as an exchange of coral immigrants to spread already existing genetic variants,” said co-author Dr Mikhail Matz of the University of Texas at Austin.
“Coral larvae can move across oceans naturally, but humans could also contribute, relocating adult corals to jump-start the process.”
Dr Bay said: “this discovery adds to our understanding of the potential for coral to cope with hotter oceans.”
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Groves B. Dixon et al. 2015. Genomic determinants of coral heat tolerance across latitudes. Science, vol. 348, no. 6242, pp. 1460-1462; doi: 10.1126/science.1261224
