Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Health of coral reefs detected from orbit

04.10.2005


Australian researchers have found Envisat’s MERIS sensor can detect coral bleaching down to ten metres deep. This means Envisat could potentially monitor impacted coral reefs worldwide on a twice-weekly basis.



Coral bleaching happens when symbiotic algae living in symbiosis with living coral polyps (and providing them their distinctive colours) are expelled. The whitening coral may die with subsequent impacts on the reef ecosystem, and thus fisheries, regional tourism and coastal protection. Coral bleaching is linked to sea temperatures above normal summer maxima and to solar radiation. Bleaching may take place on localised and mass scales – there was an extensive bleaching event in 1998 and 2002 likely linked to El Niño events.

"An increase in frequency of coral bleaching may be one of the first tangible environmental effects of global warming," states Dr. Arnold Dekker of Australia’s Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) Wealth from Oceans Flagship program."The concern is that coral reefs might pass a critical bleaching threshold beyond which they are unable to regenerate."


Aerial or boat-based observation is the current method of detecting bleaching, but many reefs are either inaccessible or simply too large (the Great Barrier Reef has an area of 350 000 square kilometres) for an event that happens within a fortnight. Bleached corals may rapidly be colonised by blue-green to brown algae, more difficult to distinguish from live coral.

Repetitive, objective and broad-scale satellite coverage is the alternative. At this week’s MERIS/AATSR Workshop in Frascati, Italy, the CSIRO team presented initial results using Envisat’s Medium Resolution Imaging Spectrometer (MERIS). MERIS acquires images in 15 different spectral bands at 300 m resolution.

"Coral bleaching needs to be mapped at the global scale," Dekker adds. "High-spatial resolution satellites can only do it on a few reefs due to cost and coverage constraints. We need a system that has appropriate coverage and revisit frequency, with a sufficient amount of spectral bands and sensitivity. There is no more suitable system than MERIS."

The team studied Heron Island reef at the southern end of the Great Barrier Reef, site of a University of Queensland research station. Validating MERIS Full Resolution mode results, they found that observed changes in live coral cover were correlated to an existing bleaching event.

Theoretical studies indicate that for each complete 300-metre pixel of coral under one metre of water it is possible to detect a 2% bleaching of live coral. MERIS should remain sensitive to detecting from 7-8% bleached coral even under ten metres of water.

"MERIS Full Resolution covers the world every three days, a bottleneck for global monitoring could be data processing," Dekker concludes. "However satellite sensors measuring sea surface temperature such as Envisat’s Advanced Along Track Scanning Radiometer (AATSR) can be applied to prioritise reefs that are subject to sea temperature heating anomalies-thus focusing the MERIS based bleaching detection.

Australia’s Great Barrier Reef Marine Park Authority has expressed interest in the project. Australian scientists plan to progress to perform MERIS monitoring of bleaching events up to the scale of the whole Great Barrier Reef.

Mariangela D’Acunto | EurekAlert!
Further information:
http://www.esa.int/esaEO/SEMCAY4Y3EE_planet_0.html
http://www.esa.int

More articles from Ecology, The Environment and Conservation:

nachricht Global threat to primates concerns us all
19.01.2017 | Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung

nachricht Reducing household waste with less energy
18.01.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Tracking movement of immune cells identifies key first steps in inflammatory arthritis

23.01.2017 | Health and Medicine

Electrocatalysis can advance green transition

23.01.2017 | Physics and Astronomy

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>