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I go on a treasure hunt

California is being slammed by a very intense El Niño event, and the effects are being felt up and down the coast. Seawater temperatures here in Santa Cruz have been in the 15-16°C since late May, and in the past week have shot up to 18.5°C. While Californians have their fingers crossed that El Niño will bring drought-relieving rain this winter, I'm also concerned about how it is affecting marine life.

On a whim, I decided this morning to take a look at what's going on in the local marine plankton. I grabbed a plankton net with a mesh size of 165 µm (we call a net with this mesh size a "zooplankton net") and headed out to the end of the wharf. The water is a milky greenish aqua color, which the Monterey Bay Aquarium says is due to a bloom of a type of phytoplankton called coccolithophores. I've never seen living coccolithophores before, as they are usually not common in Monterey Bay. Besides, they are really small and don't often get caught in the type of plankton net that I deploy. So while I didn't really think I'd catch any coccolithophores, it is always fun looking at plankton. Given the warm water and lack of productive upwelling this season, I didn't know what to expect.

Water under the Santa Cruz Municipal Wharf, 19 July 2015. © Allison J. Gong
Water under the Santa Cruz Municipal Wharf, 19 July 2015.
© Allison J. Gong
Water on the west side of the Santa Cruz Municipal Wharf, 19 July 2015. © Allison J. Gong
Water on the west side of the Santa Cruz Municipal Wharf, 19 July 2015.
© Allison J. Gong

When the water around here is this color, it usually means that phytoplankton are not very abundant. And sure enough, when I pulled up the net it wasn't very brown and didn't have that certain smell of diatoms, which were extremely thick earlier in the season. In fact, earlier this month the Central and Northern California Ocean Observing System (CeNCOOS) detected high levels of both the toxin domoic acid and the diatom, Pseudo-nitzschia, that produces it. But in today's sample I didn't see a single diatom and only a few dinoflagellates. It's conditions like this--warm, nutrient-depleted water--that the coccolithophores like.

One of the best things about examining a plankton sample is that you never know what you'll find. Despite the lack of phytoplankton in the water, my sample was chock full of interesting zooplankters. In addition to the usual copepods (probably the most abundant animals in the world) and their larvae, there were larval polychaete worms and molluscs, medusae of multiple species, and assorted other goodies.

Goodies #1 and #2:

A metamorphosing sea urchin (left) and larval polychaete (right), collected from the plankton. 19 July 2015. © Allison J. Gong
A metamorphosing sea urchin (left) and larval polychaete (right), collected from the plankton. 19 July 2015.
© Allison J. Gong

In the video clip below you can see the familiar baby-urchin-learning-how-to-walk, as well as a better view of the polychaete. Note the conspicuous segmentation and chaetae (bristles) that the animal splays out when disturbed or, in this case, gently squashed under a cover slip.

The little worm looks like it's dancing! Sometimes you can see its four eyes.


Goodie #3:

Cyphonautes larva collected in plankton sample, 19 July 2015. © Allison J. Gong
Cyphonautes larva collected from the plankton. 19 July 2015.
© Allison J. Gong

This creature is called a cyphonautes larva. It is the sexually produced pelagic propagule of a benthic bryozoan colony, most likely Membranipora membranacea. If it looks like a swimming triangle, well, that's exactly what it is.


Goodie #4:

This living lava lamp is very enigmatic. I called it a shmoo-type thing and was so intrigued that I isolated it into a separate dish for further observation. I was delighted to see that, a few minutes later, it had settled and metamorphosed into this:

It has eight stubby little tentacles and an obvious cnidarian appearance. I think it is a little anemone, but only time will tell.


Goodie #5:

Radiolarian collected from the plankton. 19 July 2015. © Allison J. Gong
Radiolarian collected from the plankton. 19 July 2015.
© Allison J. Gong

This beautiful object is a radiolarian, a type of marine amoeba. The main part of the cell is concentrated towards the center and pseudopodia are extended along the skeletal spines, which, in addition to making the cell an unpleasant mouthful, also aid in buoyancy. This one was rather large, measuring about 2 mm across. I saw many of these in today's sample.

All in all I spent a very enjoyable morning collecting and looking at plankton. I didn't see any coccolithophores, but I'm thinking that I probably should go out again with a finer-meshed net to see if I can catch them. And to see what will happen with the zooplankton if the phytoplankton remain scarce for the rest of the season.

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