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Diagnosing Coral Reef Diseases

By Ines Morales - 24 Nov 2011 14:10:0 GMT
Diagnosing Coral Reef Diseases

Coral reef in the Lembeh Striats of Indonesia via Shutterstock

Coral reefs are in big trouble. That's not new news. However, coral reefs are an important marine environment, habitat and ecosystem and an indicator of the general health of tropical seas, as well as a potential source of sustainable income - if properly managed.

For all these reasons, lately scientists and managers have been spending quite a lot of time researching the causes of coral reef mortality and coming up with appropriate strategies. Their efforts, unfortunately, have been hampered by the lack of an essential tool - namely, an effective diagnostic method.

A green fluorescent protein (GFP) labeled strain of the coral pathogen Vibrio coralliilyticus. Coral diseases have fundamentally altered Caribbean coral reef ecosystems and they pose a growing threat to Indo-Pacific reefs, yet little is known about the etiologies and pathogeneses of many of these diseases. Coral disease researchers require the development of tools to detect and quantify putative pathogens in both controlled laboratory experiments and environmentally-derived samples. Novel tools, such as this GFP-labeled strain of the coral pathogen V. coralliilyticus (shown here as a green aggregate), are currently being used to clarify the role of individual microbes in the onset and spread of coral disease lesions.

A green fluorescent protein (GFP) labeled strain of the coral pathogen Vibrio coralliilyticus; Credit: ARC Centre of Excellence

Coral diseases have been shown to have a broad range of causes. Some coral reefs are attacked by viruses, others by fungi or bacteria. As with any other living organism, determining the exact source of the illness is instrumental in finding the best treatment and/or prevention method. However, this hasn't been easy to do in the case of coral reefs. Marine researchers have been forced to rely on the description of external symptoms in order to produce a diagnosis.

For instance, researchers will look at the changes on the coloring of an affected coral reef and the ways in which its tissue has degraded, and they will identify a particular infection based on these visual clues. However, this is a rather unreliable method because different coral illnesses can resemble one another to a significant extent, or even look alike. The risk of getting it wrong, therefore, is substantial.

Now, fortunately, marine scientists and managers can rejoice. Joseph Pollock, a doctoral student at the ARC Centre for Excellence for Coral Reef Studies, headquartered at James Cook University in Australia, has applied a diagnostic technique called quantitative-PCR, generally used in medical research and forensics, to the study of coral diseases. The result is a much more accurate way of detecting and classifying pathogens in the affected corals.

Acropora millepora coral colony infected with the coral disease white syndrome, one of many coral diseases impacting coral reefs worldwide

Coral colony infected with the coral disease white syndrome, one of many coral diseases impacting coral reefs worldwide via Shutterstock

Beyond its immediate importance for the planet's coral reef ecosystems - which are in need of urgent action, given that they are rapidly declining, Pollock's discovery could also be adapted for use in other marine and oceanic environments. If the practical details can be worked out, what we have just acquired would be a valuable tool for the conservation of the seas and oceans as a whole.

The seas and the oceans badly need it, believe me, threatened as they are from so many fronts: unsustainable coastal development, pollution, overfishing and climate change.

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Topics: Coral