Subscribe to our free daily newsletters
. Earth Science News .




Subscribe to our free daily newsletters



WATER WORLD
Sentinel-2 captures coral bleaching of Great Barrier Reef
by Staff Writers
Paris (ESA) May 25, 2017


Images from the Copernicus Sentinel-2A satellite captured on 8 June 2016 and 23 February 2017 show coral turning bright white for Adelaide Reef, Central Great Barrier Reef.

Scientists observed the bleaching of Australia's Great Barrier Reef early this year using satellite images. While capturing these events from space has been difficult in the past, Sentinel-2's frequent revisits and its resolution makes it possible.

The corals of the Great Barrier Reef have now suffered two bleaching events in successive years. Experts are very concerned about the capacity for reef survival under the increased frequency of these global warming-induced events.

Bleaching happens when algae living in the corals' tissues, which capture the Sun's energy and are essential to coral survival, are expelled owing to high water temperatures.

The whitening coral may die, with subsequent effects on the reef ecosystem, and thus fisheries, regional tourism and coastal protection.

The bleached state of a coral can last up to six weeks. The corals might recover, or die and become covered by algae, in either case turning dark again, making them hard to distinguish from healthy coral in a satellite image. Such a pattern requires systematic and frequent monitoring to reliably identify a coral bleaching event from space.

Studying Sentinel-2 images captured over the reef between January and April, scientists working under ESA's Sen2Coral project noticed areas that were likely to be coral appearing to turn bright white, then darken as time went on.

The event was confirmed by two successive images captured in February, indicating the approximate duration of the bleaching being at least 10 days.

"In general, interpreting changes is ambiguous. You can't just jump to the conclusion brightening is bleaching because the brightness of any spot on a reef varies from image to image for many reasons due to both the water and bottom changes," said Dr John Hedley, scientific leader of Sen2Coral.

Dr Chris Roelfsema of the University of Queensland's Remote Sensing Research Centre, and lead of the Great Barrier Reef Habitat Mapping Project, conducted field campaigns in the area, collecting thousands of geo-located photos of the corals in January and again in April. These were used to confirm the satellite observations.

"Sadly, in the areas where bleaching can be seen, the abundant coral cover we observed in January was in April mostly overgrown with turf algae, with only some individual coral species surviving. The imagery and field data suggest this area has been hit badly," he said.

Since monitoring of bleaching is typically conducted manually by airborne surveys or diving, many reefs of the world are not effectively monitored.

Bleaching is also difficult to monitor in satellite imagery because of constant variations in the overlying water and other changes in the bottom such as micro-algal blooms.

The frequent revisits of Sentinel-2 allow these variations to be removed and help the detection of bleaching events before coral recovery or algal overgrowth turns the area dark again.

With both Sentinel-2 satellites now in orbit, the mission can contribute significantly to an increased understanding of pressures on coral reefs at a global scale.

"Sentinel 2 is a game-changer for coral reef remote sensing; the combination of frequent revisit and spatial resolution is enabling us to see genuinely new things," said Dr Hedley.

"We now know bleaching can be visible in satellite imagery, but the challenge is to produce reliable software that can map or quantify that.

"It has to account for all sources of temporal variation and, importantly, the uncertainty in the methods. The methods have to be open for scientists to be able to interpret the outputs."

Towards this aim, a set of software specifically for coral reef applications is being created by ESA's Sen2Coral project and is expected to be available on the open-source SNAP toolbox by the end of the year.

WATER WORLD
Sea level as a metronome of Earth's history
Geneva, Switzerland (SPX) May 28, 2017
Sedimentary layers record the history of the Earth. They contain stratigraphic cycles and patterns that precisely reveal the succession of climatic and tectonic conditions that have occurred over millennia, thereby enhancing our ability to understand and predict the evolution of our planet. Researchers at the University of Geneva (UNIGE), Switzerland, - together with colleagues at the Univ ... read more

Related Links
Sen2Coral Project
Water News - Science, Technology and Politics


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

WATER WORLD
Countries most affected by weather disasters do not spend more on weather services

UN braces for up to 200,000 Iraqis to flee Mosul

Trump budget calls for deep cuts to social safety net

Disaster risk management: Science helps save lives

WATER WORLD
A new tool for discovering nanoporous materials

One-dimensional crystals for low-temperature thermoelectric cooling

New theory predicts wetted area of droplets colliding with flat surface

Physicists discover mechanism behind granular capillary effect

WATER WORLD
Researchers untangle causes of differences in East Coast sea level rise

LA lawns use 70 billion gallons of water a year

How X-rays helped to solve mystery of floating rocks

Water is surprisingly ordered on the nanoscale

WATER WORLD
Methane seeping from Arctic seabed may have an upside

NASA Discovers a New Mode of Ice Loss in Greenland

NASA's Arctic Ecosystem Science Flights Begin

Elevation could help explain why Antarctica is warming slower than Arctic

WATER WORLD
Bordeaux pins hopes for ravaged vineyards on June bloom

Bordeaux pins hopes for ravaged vineyards on June bloom

Popular artificial sweetener also works as pesticide and insect birth control

Helping plants pump iron

WATER WORLD
Researchers discover hottest lavas that erupted in past 2.5 billion years

Study explains severity of 9.2 magnitude Sumatra earthquake

Mexico next in line to examine geothermal energy

Expect above-average Atlantic hurricane season, US forecasters say

WATER WORLD
Nigeria seizes illegal arms shipment

Four killed in I.Coast clashes between ex-rebels and police

Africa, so close yet so far from G7 summit

Angry Ivory Coast ex-rebels block access to cities

WATER WORLD
Portions of human skeletal structure were established millions of years earlier than previously thought,

Study reveals architecture of the 'second brain,' the enteric nervous system

'Moral enhancement' technologies are neither feasible nor wise

Adolescent orangoutan breastfeed for eight years




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement