Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The ocean surface, a whole world in motion

02.07.2007
Technical advances over the past 50 years have allowed improved knowledge to be gained of the properties of sea water at great depths. Yet the first centimetres of the ocean remain its least well known part.

They are difficult to sample and study owing to the mixing the oceanographic vessel provokes between this superficial layer and the deeper strata of water. Nevertheless, a whole ecosystem exists within this layer, carrying numerous living organisms like bacteria, zooplankton and larger animals such as flying fish, which feed and reproduce in it.

Research usually focuses rather on the whole of the sunlit part of the ocean (the first 30 to 120 metres) where the phytoplankton elaborates organic matter (in primary production) thanks to chlorophyll – its green pigment - during photosynthesis. Through this process, the ocean proves to be capable of trapping the carbon dioxide from the atmosphere by incorporating it with the organic matter produced and storing it by sedimentation down towards the deep waters. This downward movement of carbon-carrying particles is the focus of great attention among oceanographers.

In this theoretical context, IRD scientists (1) advanced the hypothesis that part of this carbon flux would rise up instead of descend, feeding the surface fauna. These living beings and the organic particles they absorb are still little known as a whole and are designated as “floating biogenic material”. A physical ocean circulation model, coupled with a model reproducing the behaviour of the ecosystems, was used in order to obtain more accurate notions of the distribution of these particles present at the ocean surface and of their relationships with the food “hot spots”, first observed several years ago (2).

The simulation run showed that the distribution of the biogenic material does not follow that of the primary production that generates it. The surface-layer organisms with their associated organic matter are under the direct influence of the surface currents. These currents carry this floating material as far as the oceanic convergence zones, places where two water masses meet. These “fronts”, where the concentrations of biogenic material are up to 10 times higher than those of other marine regions, prove to be no richer in phytoplankton and chlorophyll than the surrounding waters. The surface layer of the convergence zones is a site of accumulation only for floating debris of marine life and the organisms that feed on it.

Such concentrations of floating biomass in the otherwise nutrient-poor ocean, with low productivity and little organic-matter, is like an oasis for fish in search of food. They help explain in particular why tuna fishing is carried out essentially near these fronts, a factor that had not hitherto been clearly elucidated.

Another finding was that the optical properties of this floating material were quite close to those of chlorophyll. Consequently, this biogenic material influences observation of the colour of the ocean in the same way as the green pigment. Its presence thus distorts calculation systems which use these satellite colour data to estimate the chlorophyll concentration and therefore that of the phytoplankton. The great quantities of chlorophyll apparently detected in the convergence zones could in reality correspond to the presence of floating debris. More accurate definition of the distribution of the chlorophyll and biogenic material that accumulate at the fronts could therefore lead to a better perception and use of ocean colour as an indicator of oceanic circulation and of the ecosystem’s biological and biogeochemical processes.

Further, the accumulation of microorganisms and floating debris might influence carbon dioxide (CO2) absorption by the ocean. In fact, the life forms of the ecosystem in the first centimetres of the water breath and produce CO2. The existence of an excess of carbon dioxide just under the surface could therefore call into question the assessment methods used for the quantifying the CO2 absorbed by the ocean.

A surface sampling device is currently being developed. This kind of tool is a prerequisite for studying this theme, highly important for understanding climatic phenomena and atmospheric carbon concentration, a key parameter in global warming. (3)

Celine Bezy– DIC

(1)This research work was conducted by the “Laboratoire d'océanographie et du climat: expérimentations et approches numériques (LOCEAN)”, which jointly involves scientists from the IRD, the CNRS, the Université Paris VI and MNHN.
(2)See scientific bulletin N° 190, December 2003, accessible on www.ird.fr/fr/actualites/fiches/2003/fiche190.htm

(3)This is the GRABISU programme, in turn part of the national programme LEFE-CYBER, one of the present priorities of which is to develop new techniques for sample-taking from the surface film of the ocean.

Marie Guillaume | alfa
Further information:
http://www.ird.fr/fr/actualites/fiches/2007/fas268.pdf

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF

nachricht Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.

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: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>