Scientists found that some corals from cooler waters tolerate more heat than those from warmer reefs, offering new insights into coral resilience and restoration.<\/p>\n
Many reef-building corals already live close to the most heat they can take. Yet reef-builders that share a stretch of coast don\u2019t all respond to warming the same way. <\/p>\n
In a heat test, finger corals from a cooler, wave-exposed bay in Hawai\u02bbi tolerated more heat than members of the same species from a warmer bay nearby.<\/p>\n
A second species, rice coral, showed about the same tolerance from either bay. <\/p>\n
The results suggest that heat tolerance depends on both the coral species and the conditions where it lives.<\/p>\n
Too much heat makes corals bleach, which means they lose the tiny algae in their tissues that supply most of their food.<\/p>\n
Testing heat tolerance in corals<\/p>\n
Allison M. Klein, a postdoctoral fellow at FAU Harbor Branch<\/a>, ran the comparison with Professor Joshua D. Voss and colleagues at the University of Hawai\u02bbi\u2019s Hawai\u02bbi Institute of Marine Biology. <\/p>\n The team tested small fragments collected in both bays, in tanks rather than on reefs during a real heat wave.<\/p>\n \u201cBy exposing corals from distinct environmental histories to a standardized thermal stress experiment, we were able to directly compare differences in thermal tolerance across species and populations,\u201d Klein said. <\/p>\n \u201cThis approach allowed us to examine how prior environmental conditions may shape physiological responses to heat stress.\u201d<\/p>\n Two nearby bays differ<\/p>\n K\u0101ne\u02bbohe Bay, on the east coast of O\u02bbahu, is the largest sheltered bay in the main Hawaiian Islands. <\/p>\n Its many reefs help keep the water warm and stable, with summer surface temperatures of about 81\u00b0F to 84\u00b0F (27\u00b0C to 29\u00b0C). <\/p>\n The bay lost up to 22% of its coral cover during mass bleaching<\/a> in 2014 and 2015.<\/p>\n Kailua Bay, just southeast of K\u0101ne\u02bbohe, is open to trade winds and ocean swells. <\/p>\n It has more water movement and cooler water, about 77\u00b0F to 82\u00b0F (25\u00b0C to 28\u00b0C) in summer, and its temperatures change more over short periods. <\/p>\n At the team\u2019s site there, called Ulupa\u02bbu, finger coral grows in compact, knobby shapes instead of the open branches common in K\u0101ne\u02bbohe Bay.<\/p>\n Heating coral in tanks<\/p>\n Rice coral, Montipora capitata, can form broad plates or branching colonies with a textured surface, while finger coral, Porites compressa, grows in clusters of slender, finger-like branches. <\/p>\n The team collected five colonies of each from three sites in K\u0101ne\u02bbohe Bay in December 2023 and from Ulupa\u02bbu in April 2024, 40 in all. <\/p>\n Before testing, the K\u0101ne\u02bbohe corals spent about five months in an underwater nursery, while the Ulupa\u02bbu corals spent about one month.<\/p>\n In May 2024, two branches from each colony, each about 2 inches (5 centimeters) long, were placed in outdoor seawater tanks. <\/p>\n Over six days, the water warmed from about 78\u00b0F (25.5\u00b0C) to 90\u00b0F (32\u00b0C), roughly 7\u00b0F (4\u00b0C) above the area\u2019s warmest monthly average. <\/p>\n Every two days, the team measured the faint light given off by the algae\u2019s chlorophyll, which shows how well the algae turn sunlight<\/a> into energy.<\/p>\n Both species tolerated heat<\/p>\n Scientists measure heat stress on reefs in degree heating weeks, a running total of the extra heat a reef has faced over the past three months. <\/p>\n A week of water 1.8\u00b0F (1\u00b0C) above the usual summer peak adds one degree heating week. <\/p>\n NOAA Coral Reef Watch says significant bleaching usually begins at 4, and stress of 8 or more has been linked to widespread bleaching and death on reefs<\/a>.<\/p>\n The team tallied heat in the tanks the same way. For each colony, the researchers calculated how much heat it took for its algae<\/a> to lose 30% of their efficiency. <\/p>\n The colonies reached that threshold after accumulating between 5.93 and 7.21 degree heating weeks, exceeding NOAA\u2019s benchmark for significant bleaching risk on natural reefs.<\/p>\n Some finger corals stood out<\/p>\n Finger corals from Ulupa\u02bbu tolerated about 0.39 more degree heating weeks than their K\u0101ne\u02bbohe Bay counterparts. <\/p>\n They also tolerated 0.65 more than rice coral collected at Ulupa\u02bbu.<\/p>\n That species, by contrast, scored about the same in both bays. So colonies from the cooler bay weren\u2019t tougher across the board.<\/p>\n \u201cThis study identified more resilient corals from certain locations in these testing conditions, which provides important hope for the future,\u201d Voss said.<\/p>\n \u201cThe results demonstrate that both species identity and local environmental history can influence coral thermal performance and success in coral restoration efforts.\u201d <\/p>\n Species may cope differently<\/p>\n Inside K\u0101ne\u02bbohe Bay, both species had about the same heat limits. <\/p>\n Finger coral also bleached more slowly than rice coral, which suggests the two species may cope with warming in different ways.<\/p>\n \u201cOur findings highlight that coral resilience to ocean warming<\/a> is not uniform, even among species living in close geographic proximity,\u201d Voss said.<\/p>\n \u201cAs reefs around the world face more frequent and intense marine heat events, understanding which corals can tolerate that stress \u2013 and why \u2013 will be critical for protecting and restoring reefs.\u201d<\/p>\n \u201cWhat works for one species or population may not work for another, so conservation strategies need to account for both the biological and the environmental diversity that exists within coral reef ecosystems.\u201d<\/p>\n Stronger reefs may need diversity<\/p>\n Ulupa\u02bbu\u2019s finger corals may be one source of naturally heat-tolerant<\/a> colonies for restoration, where fragments are grown in nurseries and planted on damaged reefs. <\/p>\n Still, the researchers cautioned that the most heat-tolerant ones aren\u2019t always the best choice. <\/p>\n Keeping genetic variety and a range of traits could help a restored reef adjust to different conditions over time.<\/p>\n Why the Ulupa\u02bbu finger corals did better is still unknown, and the differences in collection season and nursery time may play a part. <\/p>\n Repeated exposure to Ulupa\u02bbu\u2019s cooler, more changeable water may help prepare them for heat, but the team didn\u2019t test that idea or check the colonies\u2019 genes or which algae they carry. <\/p>\n Next, the researchers plan to read the DNA of those algae to see whether they help explain the difference.<\/p>\n The full study was published in the journal Scientific Reports<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.\u00a0<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Scientists found that some corals from cooler waters tolerate more heat than those from warmer reefs, offering new…\n","protected":false},"author":2,"featured_media":931104,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[64,63,128],"class_list":["post-931103","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-au","tag-australia","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/931103","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=931103"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/931103\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/931104"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=931103"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=931103"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=931103"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}