Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Endangered Turtles’ Trek Along Ocean Currents Revealed By Satellite

04.08.2004


The site where Europe’s spacecraft are launched into orbit, the Atlantic shoreline of French Guiana, is also the starting point for another hardly less remarkable journey: the epic migration of the critically endangered leatherback turtle.



Scientists have been using tracking sensors to follow the long treks of individual leatherbacks, then overlaying their routes with sea state data, including near-real time maps of ocean currents gathered by satellites including ESA’s ERS-2 and now Envisat.
They are working to uncover connections between the apparently meandering routes followed by turtles and the local ocean conditions, and so develop strategies to minimise the unintended but deadly threat posed to leatherbacks by deep-sea fishing.

These giant reptiles - known to reach 2.1 metres in length and weigh in at 365 kg - briefly come ashore to lay their eggs on beaches across French Guiana and neighbouring Suriname, the turtles’ last remaining major nesting sites in the Atlantic Ocean. Around nine weeks later the hatchlings emerge en masse and head into the sea, one day to return when they reach maturity and lay eggs themselves.



However each turtle’s return is by no means certain. While in open water the turtles have been known to dive as deep as 1,230 metres in search of food, most of the time they do not venture deeper than 250 metres down, leaving them vulnerable to the hooks of longline fishermen – hundreds of thousands of such hooks are deployed daily across the Atlantic.

Ongoing ’bycatching’ of leatherbacks by fishermen has left the 100-million-year-old species on the brink of extinction in the Pacific and Indian oceans. In the Atlantic their numbers are higher – partly due to a ban on longline US fishermen operating in the Ocean’s northern section - but the turtles are still being lost at an unsustainable rate.

A paper was recently published in Nature summarising the work done so far in tracking leatherbacks through the Atlantic, submitted by a team of researchers from France’s National Centre for Scientific Research in Strasbourg, neighbouring Louis Pasteur University, the French Guiana Regional Department of the Environment and the company Collecte Localisation Satellites (CLS) in Ramonville, specialising in satellite-based systems for location-finding, data collection and Earth Observation.

Pacific leatherbacks follow narrow migration corridors. Researchers hoped that if their Atlantic counterparts acted in the same way then fishing could be restricted across these zones.

Starting in 1999 individual turtles were tracked using the CLS-run Argos system, based on radio-emitting tags whose position can be tracked worldwide to a maximum accuracy of 150 metres. Six American NOAA spacecraft currently carry Argos receivers, with ESA’s MetOp series due to join the system following their initial satellite launch next year.

The turtles’ tracks were then overlaid with maps of sea level anomalies obtained by merging data with the radar altimeter aboard ESA’s ERS-2 with another aboard the NASA-CNES satellite TOPEX-Poseidon.

ERS-2, like its successor Envisat, is part of the select group of satellites equipped with a Radar Altimeter (RA) instrument. By firing thousands of radar pulses off the surface of the sea every second extremely precise ocean height measurement is made possible. Height anomalies detected by this type of sensor are often indicators of the presence of ocean currents and eddies: warm currents can stand up to a metre above colder waters.

By merging multiple radar altimeter results together, the result is a more frequent and higher resolution measurement of sea level anomalies than any one spacecraft could achieve. For example, now that ERS-2’s global mission is over, results from Envisat’s RA-2 instrument are being combined with similar data from the joint French-US Jason spacecraft and the US Navy’s GFO.

"The altimetry data has been very useful to our work because we have been able to check the turtles’ trajectory against ocean currents," said Philippe Gaspar, co-author of the Nature paper and Head of the Satellite Oceanography Division of CLS. "What we have found is that their relationship with currents alters considerably over the course of their journeys.

Unlike their Pacific relations, the Atlantic leatherbacks do not follow narrow migration corridors but disperse widely - to begin with, the leatherbacks carry out long nearly straight migrations either to the north or to the Equator, swimming across currents as they encounter them. One made it to within 500 km of West Africa before turning back, another came close to Nova Scotia.

"Then having either made it to the Gulf Stream area or to the equatorial belt, the turtles tend to slow down and follow the frontal areas associated with local ocean current systems, which are generally rich in marine life."

Unfortunately fishing fleets target these frontal systems for exactly the same reason, so these turtles are placing themselves in danger. This finding means limited closures of Atlantic fishing areas is unlikely to have much impact in turtle bycatch reduction, and other solutions will have to be considered, such as turtle-friendly fishing gear and hooks recently developed by NOAA and endorsed by the World Wildlife Fund.

Meanwhile leatherback tracking continues on an ongoing basis, Gaspar added: "We are now looking at estimating the swimming speed of turtles during their trips by obtaining their total velocity from the Argos receivers, then subtracting the current velocity made available to us by altimetry. This has never been done before and should provide us with useful information on the energy they expend throughout their migration."

French schools have been given the chance to take part as part of an educational oceanographic scheme called Argonautica, with classes participating in the Argo-luth project, analysing turtle movements against outputs from MERCATOR, a model that presently covers the North and Equatorial Atlantic Ocean and assimilates radar altimeter data on an operational basis.

Mariangela D’Acunto | alfa
Further information:
http://www.esa.int

More articles from Life Sciences:

nachricht Bolstering fat cells offers potential new leukemia treatment
17.10.2017 | McMaster University

nachricht Ocean atmosphere rife with microbes
17.10.2017 | King Abdullah University of Science & Technology (KAUST)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Ocean atmosphere rife with microbes

17.10.2017 | Life Sciences

Neutrons observe vitamin B6-dependent enzyme activity useful for drug development

17.10.2017 | Life Sciences

NASA finds newly formed tropical storm lan over open waters

17.10.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>