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 Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

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: 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

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>