Monday, February 16, 2009

Misidentified Mnemiopsis (it's actually Mertensia)


Baltic Sea interests were concerned about an invasion of the "American pseudo-jellyfish" (actually a ctenophore, or comb jelly) in 2007 (they probably blamed it on President Bush). Here's what Mnemiopsis looks like at left. Mnemiopsis has/had the potential to alter the Baltic ecosystem -- not that it hasn't been altered considerably already, with some noxious blooms and increasing eutrophication just about everywhere. A little Mnemiopsis might actually do something about the eutrophication, but too many Mnemiopsids would eat too much plankton, and not leave enough for the fish.

But it turns out that it wasn't Mnemiopsis, it was the Arctic ctenophore Mertensia, which is common in the Arctic and hadn't been reported in the Baltic, even though given how close the Baltic is to the Arctic, it probably had been hanging out somewhere. Here's what Mertensia looks like at right.

It's easy to see why there was a bit of confusion. Well, this is one invasion of Europe that the Americans aren't participating in.

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