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Monday, October 25, 2010

Lion's Mane Jellyfish and Current Flows

A lot of my beach walks this fall have featured dead lion's mane jellyfish (Cyanea capillata) washed up on shore or in the surf. I've noticed that throughout the year we have periodic explosions of live and/or dead jellyfish of various species, and I never really understood why that was until I came across this 2002 article by a scientist from the Friday Harbor Labs.

It turns out that despite the daily tidal fluctuations the prominent water flow in the area is out towards the ocean. Occasionally, usually at least once in the spring and once in the fall, the water flow temporarily reverses and we get a huge influx of typically oceanic species into our inland waters. These species then can persist here for months, giving researchers an opportunity to study species of plankton, etc. that aren't always as accessible. The influx of jellyfish I've noticed are also due to these current shifts. Typically, we see smaller jellyfish coming in with the spring flow, and lion's mane with the fall flow. I'm glad I finally learned a little more about this!

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