Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Potential new threat for coral reefs and the health of communities in the tropics

04.09.2008
Human activities bear a large part of the responsibility for coral reef degradation. Several threats hang over this complex ecosystem with its extraordinary biodiversity, whether in the form of anthropogenic effluents emitted at certain times or global warming which causes coral bleaching.

The dead corals can be colonized by a blanket of algae in turn favouring colonization by dinoflagellates of the Gambierdiscus genus. These microorganisms secrete a toxin which the reef fish ingest when they feed. Then when humans eat the flesh of contaminated fish they fall victim to an infection called Ciguatera.

Some regions like French Polynesia or New Caledonia are particularly strongly exposed to this effect which triggers over 100 000 cases of severe poisoning annually throughout the world. Between 2001 and 2005, the recording of 35 cases of Ciguatera-type poisoning that had hit the same tribe, the Hunete, living on the New Caledonian island of Lifou, prompted a scientific team from the IRD to conduct a more searching enquiry. Their investigations first indicated that the part of the coral reef where these fishermen caught their fish had been destroyed in order to facilitate launching of their fishing vessels.

Submarine observations showed that in places the dead coral was covered by a carpet of cyanobacteria. Epidemiological study then revealed that herbivorous fish species were involved in 70% of the poisoning outbreaks registered in the tribe studied. Now, Ciguatera poisoning generally comes from the flesh of carnivorous fish, placed at the top of the food chain, and which remains the most toxic for humans owing to bioaccumulation. The exceptional speed with which symptoms appear in these new cases (burning in the mouth or throat as soon as the fish is ingested), the complete lack of effect of traditional remedies such as false tobacco (or elephant’s foot) and the gravity of symptoms (one-third of people poisoned had to go to hospital, compared with 2% for Ciguatera) , signals something other than the classic form of poisoning.

As well as this finding, this study also brought the first demonstration that consumption of giant clams (Tridacna) was linked to poisoning outbreaks. These newly revealed elements support the idea of a contamination mechanism which differs significantly from that caused by dinoflagellate algae even though certain neurological symptoms, such as sensation inversion, are identical. The research team therefore took samples of cyanobacteria, giant clams and different species of coral fish in the Hunëtë fishing zone most at risk.

An array of toxicological analyses performed on mollusc and cyanobacterial extracts brought evidence of complex paralysing substances, some of which had a structure closely similar to ciguatoxins. These results overall point to a hitherto unknown poisoning agent, similar to Ciguatera, yet produced by cyanobacteria. However, unlike dinoflagellates, these microorganisms contaminate mollusc species such as the giant clam and also a broad range of coral reef fish local people use as food.

Another potential consequence emerged from this study. The rise in oceanic temperature by a few degrees, associated with global warming, is already known to have a negative impact on coral reefs: bleaching and eventual death. Such reef ecosystem degradation creates the danger of colonization of this environment-and therefore the fishing grounds-by these cyanobacteria, hence endangering the marine way of life of the area’s human populations. This already seems to be the case in the French Polynesian island of Raivavae, in, where certain sites are indeed covered with an extensive matting of cyanobacteria. The thousand or so inhabitants of this “paradise” island, faced with increasingly frequent Ciguatera-like poisoning incidents, are switching from a diet where proteins come almost exclusively from lagoon-caught fish and shellfish to one based strongly on other animal proteins. For these fishing communities therefore, global warming could be expressed not only by a degradation of their fishing grounds but also by the emergence of cardiovascular diseases linked to too rapid a transition in diet.
1. This research was conducted jointly with scientists from the Institut Louis Malardé in Papeete (French Polynesia), the Institut Pasteur of New Caledonia, the CNRS, INSERM and the University of Boston (USA).

Grégory Fléchet | alfa
Further information:
http://www.ird.fr

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>