Scientists map living corals before and after marine heat wave: Winners
and losers discovered
Findings could help manage and build a resilient network of coral reefs


Date:
May 2, 2022
Source:
Arizona State University
Summary:
Scientists reveal that different corals and environments influence
the likelihood of their survival when ocean temperatures rise. The
findings also demonstrate that advanced remote sensing technologies
provide an opportunity to scale-up reef monitoring like never
before.



FULL STORY ==========================================================================
As the world sees rising ocean temperatures, it will also see more cases
of coral bleaching. When corals bleach, they become more vulnerable to
other stressors such as water pollution. However, many reefs harbor
corals that persist despite warming oceans. Unraveling the complex
issue of coral bleaching and its impact on their survival or death may
be key to conserving coral reefs -- ecosystems that more than half a
billion people around the world rely on for food, jobs, recreation and coastline protection.


==========================================================================
For the first time, scientists have mapped the location of living corals
before and after a major marine heat wave. In the new study, research
shows where corals are surviving despite rising ocean temperatures caused
by climate change. The study also finds that coastal development and
water pollution negatively affect coral reefs.

In the study, published today in Proceedings of the National Academy
of Sciences, Arizona State University scientists with the Julie Ann
Wrigley Global Futures Laboratory reveal that different corals and
environments influence the likelihood of their survival when ocean
temperatures rise. The findings also demonstrate that advanced remote
sensing technologies provide an opportunity to scale-up reef monitoring
like never before.

From its home in the Hawaiian Islands, ASU researchers with the Center
for Global Discovery and Conservation Science took to the sky on
the Global Airborne Observatory (GAO). The aircraft is equipped with
advanced spectrometers that map ecosystems both on land and beneath the
ocean surface.

With these maps, the researchers can assess changes in coastal ecosystems
over time.

"Repeat coral mapping with the GAO revealed how Hawaii's coral reefs
responded to the 2019 mass bleaching event," said Greg Asner, lead author
of the study and director of the ASU Center for Global Discovery and Conservation Science.

"We discovered coral 'winners' and 'losers.' And these winning corals
are associated with cleaner water and less coastal development despite
elevated water temperatures." When the Hawaiian Islands faced a
mass bleaching event in 2019, the GAO mapped live coral cover along
eight islands before the marine heat wave arrived. With these data, the researchers identified more than 10 potential coral refugia - - habitats
that may offer a safe haven for corals facing climate change. Among
the potential refugia, there was up to 40% less coral mortality than on neighboring reefs, despite similar heat stress.

The results also indicated that reefs near heavily developed coasts are
more susceptible to mortality during heat waves. When development occurs
on land, the amount of pollution entering the reef ecosystem increases, creating an unfavorable environment for coral reefs already fighting to
survive the warming water.

"This study supports Hawaii's Holomua Marine 30x30 Initiative by not
only identifying areas impacted by ocean heat waves, but also areas
of refugia," said Brian Neilson, study co-author and head of Hawaii's
Division of Aquatic Resources, "These findings can be incorporated
into management plans to aid in building a resilient network of reef
regions and sustaining Hawaii's reefs and the communities that depend on
them into the future." The Holomua 30x30 initiative aims to establish
marine management areas across 30% of Hawaii's nearshore waters. Coral
reefs in Hawaii are integral to life on the islands, tied to culture
and livelihoods. Understanding which corals are surviving is key to
achieving conservation that is targeted and effective.

"Previous approaches have failed to deliver actionable interventions
that might improve coral survival during heat waves or to locate places
of heatwave resistance, known as coral refugia, for rapid protection,"
said Asner, who is also director of the Global Airborne Observatory. "Our findings highlight the new role that coral mortality and survival
monitoring can play for targeted conservation that protects more
corals in our changing climate." The Center for Global Discovery and Conservation Science at ASU collaborated on this study with the Hawaii
Division of Aquatic Resources and the National Oceanic and Atmospheric Administration's Pacific Islands Fisheries Science Center. The Lenfest
Ocean Program of Pew Charitable Trusts supported this study.


========================================================================== Story Source: Materials provided by Arizona_State_University. Original
written by Makenna Flynn. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Gregory P. Asner et al. Mapped coral mortality and refugia in an
archipelago-scale marine heat wave. PNAS, 2022 DOI: 10.1073/
pnas.2123331119 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220502170854.htm

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