Invasive seaweed develops stronger defences

04.01.2016 07:20
Kategorie: News


Possibility of higher food poisoning cases if invasive strain returns to place of origin

The algae Gracilaria vermiculophylla and the snail Littorina brevicula - a major Lepidoptera enemy of algae in East Asia. Photo: F. Weinberger, GEOMAR
The algae Gracilaria vermiculophylla and the snail Littorina brevicula
- a major Lepidoptera enemy of algae  © F. Weinberger, GEOMAR

A higher level of defence has been found within an invasive strain of seaweed from Asia that has translocated to North America and Europe. Should this migrant strain find its way back to its native home, cases of food poisoning may become more frequent.

This is the conclusion of a paper written by an international team of scientists from the GEOMAR Helmholtz Centre for Ocean Research Kiel, published in the journal Harmful Algae.

Newly introduced species do their best to survive in their new environments. Sometimes, they are lucky and find themselves in a place where they have few predators. In such environments, they become invasive, spreading rapidly and causing damage. Examples are the Chinese mitten crab, the naval ship worm or the Japanese oyster, all of which have successfully invaded the North Sea and Baltic Sea regions. Other species do not have it so easy and have to adapt by strengthening their defensive capabilities; one such species is the seaweed Gracilaria vermiculophylla from East Asia that has recently spread to Europe and North America.

In Asia, this algae is used as food and preferably eaten raw. Occasionally, the presence of the prostaglandin hormone within its body have led to instances of severe or fatal poisonings. Prostaglandin is useful as it protects the algae against predators like snails and small crustaceans, which are sensitive towards it.

In recent decades, the algae has spread to Europe and North America. These strains have a more pronounced defence (by possessing more prostaglandin) than the native strains, and are thus better able to protect themselves against predators.

According to Dr Florian Weinberger, project leader and co-author of the study, twelve selected populations of the algae in East Asia, Mexico and Europe were studied. "That was a difficult task because we used living specimens that had to be collected from all populations and to be transported alive to the cultivation facility of GEOMAR. Only in this way we could compare the capacity of all the specimens to produce deterrents under identical environmental conditions.

The results revealed that the non-native species contained more prostaglandin than those from Asia – with the concentration being elevated by up to 390%. After translocating to the new environments, Gracilaria vermiculophylla needed to be better protected against predators, explaining the higher level of prostaglandin, said lead author Mareike Hammann, who had wrote the paper as part of her doctoral thesis.

The results of the study raises the question of what would happen if the invasive strain of Gracilaria vermiculophylla finds its way back to Asia. Should this happen, Weinberger predicts an increase in the number of poisoning incidents. As a result, continual monitoring is needed so that there would be sufficient time to issue timely warnings to prevent or minimise cases of food poisoning.

Link to the study: