Purple pools and purple waves

Eric and I did some early morning field work today.  When we first got there, we noticed a purplish hue at the high tide line.  When we got closer to the tidepools we saw this:

 

The pools were filled with doliolids!

Here's a close-up showing how dense they were:

 

And another shot, with some of the doliolids floating at the surface.  You can see their barrel-shape, with prominent muscle bands:

 

I don't recall seeing abundances and concentrations of doliolids in the intertidal zone like this before.  For the record, here are a few more examples:

Draped over Feather Boa Kelp (Egregia menziesii)

 

Undigestible portions being spit out by Aggregating Anemones (Anthopleura elegantissima) — the large pinkish blobs emerging from the anemones' mouths:

 

There were so many doliolids, they were painting the waves purple!

 

I introduced doliolids last year, so to learn more about them, read the post from 15 June 2015.

P.S.  I heard that doliolids were also seen at Doran Beach today.  If you come across them, let me know — it would be fun to know where else they're showing up.

 

Roll out the Barrel

Last night I showed a picture of doliolids washed up on Salmon Creek Beach:

 

 

I thought it would be valuable to document this event, and to illustrate what the doliolids looked like en masse on the sand because you might encounter them that way.  However, I felt badly that the picture didn't provide a proper introduction to doliolids.

So here you go!

 

These animals were ~1 cm long.  Doliolids are barrel-shaped with prominent muscle bands.  (In doliolids the muscle bands completely encircle the animal, whereas in salps the muscle bands are incomplete.)  They have openings at both ends — water is drawn in through the oral siphon and expelled through the atrial siphon (see diagram below).  The muscle bands are used for swimming, and for opening and closing the siphons.

 

Modified from Biology of the Invertebrates, 6th Edition by Pechenik (2009)

 

Doliolids are active filter-feeders, using a mucous net to capture small particles in the water.

Cilia on the pharynx generate a water current.  As the water passes through the pharyngeal cavity, food is trapped on a mucous sheet (secreted by the endostyle) and then is rolled into a string and transferred to the mouth.  The pharynx is also a site for gas exchange.

Here's another individual in which you can still see the pharynx (at the bottom of the picture):

 

I was intrigued by the structure of the pharynx, so I've included an even closer view where you can see the gill slits (the long, narrow openings in the pharynx):

 

Although many doliolids are tropical or semi-tropical, Dolioletta gegenbauri is a relatively cold-tolerant species.  This species is found in northern California, but it's uncommon to see them near shore.  They're open ocean animals, so finding them on the beach is rare (and fascinating!).

Purple slime

A quick walk at Salmon Creek Beach on 14 June 2015 yielded some interesting sightings.

 

There were quite a few (perhaps 25?) Blue Buoy Barnacles (Dosima fascicularis).  Many individuals were attached to By-the-wind Sailors (Velella velella), but some had their own floats, as above.

There was a lot of foam, and many bubbles, and you know I can't resist photographing colorful bubbles.  

I couldn't choose a favorite bubble picture, so I've included a few (below).  Which one do you like?  (Some of these bubbles were attached to Velella, which created a vivid blue backdrop.)

 

 

 

 

One of the most interesting things we saw wasn't easily photographed.  Here's a picture:

 

I know it doesn't look like much, but I'm guessing you can tell that it looks gelatinous, and purple!

There were probably millions of doliolids washing up on the beach tonight.  Doliolids are planktonic animals related to salps and pyrosomes.  We first noticed doliolids in the surf zone about ten days ago.  This is the first time we've observed large numbers stranding on Salmon Creek Beach.  Although we didn't identify them for sure, it's likely to be Dolioletta gegenbauri.  You can see a nice picture of an individual doliolid at the JelliesZone web site.  (They also include a description of doliolids.)

Unfortunately, the doliolids didn't retain their shape when washed up on the sand, so they just looked like patches of purple slime.  If I get a better picture in the days ahead, I'll post one.  Meanwhile, if you're walking local beaches and see something similar to the picture above, perhaps you'll recognize it as an interesting pelagic animal!

 

P.S.  Eric also noticed an unusual, strong sulfur smell while walking the beach — perhaps emitted by phytoplankton?