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Friday, April 18, 2025

Just in time for Easter -- lots of eggs!

  

We went out to the rocky shore early this morning to start some surveys.  Right away Eric noticed that the tidepools looked unusual.  All of them appeared cloudy or milky.  We were aware recent ocean conditions might trigger spawning in some marine invertebrates, and sure enough, this was a massive spawning event of California Mussels (Mytilus californianus), probably the largest we've encountered.

In the photo above, the orange coloration is eggs released by female mussels.  Here's another example, with clusters of eggs concentrated along the edge of a pool:

 

In other pools, the color was white or gray, clouded by vast quantities of sperm released by male mussels:

 

Nearly every tidepool we observed on Bodega Head appeared to have mussels spawning, so the extent of this synchronous mass spawning event was truly remarkable.  Even the largest pools were visibly cloudy:
 
 
The ocean temperature went up from 11°C (52°F) to 13°C (55°F) yesterday, and there was a phytoplankton bloom nearshore — both environmental cues that are thought to trigger spawning in some invertebrates.

Amazing!  Let us know (and send photos) if you notice local marine invertebrates spawning, too!

3 comments:

Sybold said...

Wow. And what does this bode for the near future of our coast?

Jackie Sones said...

Well, it depends! It could mean a lot of little mussels recruiting into the rocky intertidal zone. But there are a lot of unknowns -- e.g. How widespread was the event beyond Bodega Head? Are there good conditions for growth and development of the embryos and larvae? Will ocean currents be favorable for returning the larvae to shore?

Overall, spawning is one important of the life cycle, but there are a lot of factors that will ultimately determine whether this event leads to an increase in the mussel populations along our coast.

:) Jackie

Limantour walker said...

Thank you! You answered the question in my mind too!