New detection system for marine parasites developed

9 December 2008

Marine parasites that infect great forests of seaweed have been difficult to detect in the past.

Kelp

Kelp forest support large marine ecosystems around the UK and Europe.

But now scientists in Scotland and Germany have developed a new genetic technique to rapidly and reliably identify the most common parasite of kelp, Eurychasma.

In terms of weight, kelp accounts for most of the biomass in temperate and cold marine habitats worldwide. It is a brown algae that can form towering underwater forests up to sixty metres high.

The researchers think the parasite interferes with the kelp's reproductive cycle, slowing population growth, which would have consequences for efforts to harvest kelp sustainably for biofuel or to manage fragile threatened populations.

Dr Claire Gachon, who developed the new technique, explains, "We have reasons to believe that Eurychasma's biggest impact might be through perturbing the sexual reproduction of kelps."

She adds, "But this hypothesis is not demonstrated yet."

Before developing the new process, researchers had overlooked the parasite largely because of the difficulty identifying it.

The ocean's forests

Kelp provides a home, protection and food for many species. Sea urchins thrive on kelp, and these in turn feed sea otters. The seaweed is also essential for economically important species like lobsters and is a much-touted green energy source. A Eurychasma epidemic might have far-reaching consequences for sea life.

Using a molecular genetic technique called real-time PCR that rapidly replicates DNA, scientists from the Culture Collection of Algae & Protozoa based at the Scottish Association for Marine Science in Oban and at the biology faculty at Konstanz University in Germany found the parasite in samples of brown algae from Northern Europe and South America.

Real-time PCR enables researchers to identify quickly and accurately very small amounts of DNA specific to the parasite from a sample of algae. The only other way to find the parasite - using a microscope - is laborious and time-consuming.

The technique is the first time anyone has been able to reliably and systematically check for the parasite in the field.

Real-time PCR has another advantage: it can show that some of algae are more resistant to some strains of the parasite than others.

Gachon believes this is because the algae's immune response is genetically determined. Although scientists knew this occurred in terrestrial plants the new research is strong evidence that it also applies to brown algae.

The team now plan to look at how the algae manage to resist infection and whether this has changed the genetic make-up of whole populations of the algae over time.

"This is only the beginning of the story," says Gachon, who wants to use the new technique to show conclusively just how widespread and abundant the parasite is.

"Now we have the technique to detect Eurychasma in the field." she says, "So let's go out and apply it."

The research is published online in the journal Applied and Environmental Microbiology.