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

nachricht 100 % Organic Farming in Bhutan – a Realistic Target?
15.06.2018 | Humboldt-Universität zu Berlin

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: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Better model of water under extreme conditions could aid understanding of Earth's mantle

21.06.2018 | Earth Sciences

What are the effects of coral reef marine protected areas?

21.06.2018 | Life Sciences

The Janus head of the South Asian monsoon

21.06.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>