Invasive species appears to be beneficial for Baltic Sea
Marenzelleria worm found to reduce oxygen depletion on sea bottom
Plant and animal species which are introduced into habitats other than their own often have harmful effects on their new environments. However, the Marenzelleria , a sea worm native to waters of North America, has been found to have a beneficial effect on the Baltic Sea.
In an article in the Global Change Biology series, a group of Nordic researchers point out the beneficial effects that the new species is having on the nutrient cycle at the bottom of the Baltic Sea, which has long suffered from hypoxia, or oxygen depletion.
The worm has been found to loosen the bottom sediments, increasing the oxygen content.
It also binds phosphorous to the sediments, preventing its release into the water where it promotes the growth of toxic blue-green algae in the summertime, says Joanna Norkko, an assistant at the Tvärminne zoological station, who was a member of the research group.
“On the other hand, we did not investigate how it affects other species – whether or not there would be the kind of harmful competition between the Marenzelleria and other species. No evidence or observations of this have been made”, Norkko points out.
A mature Marenzelleria is between four and five centimetres in length, and it is harmless to humans.
“In the 1990s considerable investments were made in the Stockholm area in sewage treatment. The new study found that the improvement to the ecosystem caused by the Marenzelleria was twice that of the benefits achieved through improved sewage treatment”, Norkko says.
The Marenzelleria was introduced to the Baltic Sea in the ballast water of ships. It was first observed in the Baltic in 1985, and in the past ten years it has become one of the most prolific species in the Baltic Sea.
Previously in HS International Edition:
Combating harmful alien invasive species calls for tougher measures (15.2.2011)
Invasive comb jellies now found throughout Baltic Sea (17.12.2007)
Global Change Biology: A welcome can of worms? Hypoxia mitigation by an invasive species (abstract)