Life in the sea

This morning I collected another plankton sample from the end of the Santa Cruz Municipal Wharf, equipped this time with a 53-µm net used to collect phytoplankton. Phytos, as we refer to them, are the (mostly) unicellular photosynthetic organisms that make up the bottom of the pelagic trophic web. In a nutshell, they are the food that sustains all other organisms in the pelagic realm; i.e., every creature that lives away from the sea floor. Without phytoplankton, we would essentially have zero life in the sea. Think about that the next time you see a "Save the Whales" sign:  To save the whales, maybe we should work harder at saving the phytoplankton.

The water is still that pretty shade of aquamarine, but to the naked eye it seemed a little less opaque than it was a week ago. One thing I did see immediately was a huge school of bait fish, and a gaggle of teenage boys trying to catch them with their fishing poles. The school was pretty impressive; the teenage boys, not so much. But they get props for trying.

School of bait fish on the east side of the Santa Cruz Municipal Wharf, 24 July 2015. © Allison J. Gong
School of bait fish on the east side of the Santa Cruz Municipal Wharf, 24 July 2015.
© Allison J. Gong

I find schooling behavior fascinating. I love how the amorphous blob moves through the water, avoiding predators and obstacles (including my plankton net) alike with apparently little effort. Even the sea lions swimming around the pilings didn't generate much of a response from the fish except a lazy move out of the way.

The arrival of bait fish makes me wonder if whales will follow.


Back in the lab I looked at what I had caught. As expected there were very few large animals, but quite a lot of interesting phytoplankters and small zooplankters. Here's a sort of representative sample:

Marine phytoplankton collected from Santa Cruz Municipal Wharf, 24 July 2015. Key:  (a) Radiolarian, a type of amoeba; (b) Protoperidinium, a dinoflagellate; (c) Ceratium, a dinoflagellate; (d) unidentified golden cells. © Allison J. Gong
Marine phytoplankton collected from Santa Cruz Municipal Wharf, 24 July 2015.
Key: (a) radiolarian, a type of amoeba; (b) Protoperidinium, a dinoflagellate; (c) Ceratium, a dinoflagellate; (d) unidentified golden cells.
© Allison J. Gong

The coolest thing I found in today's sample was a silicoflagellate. I think in all my years of observing local marine plankton I've seen silicoflagellates only once before today, when I was in graduate school. Not much is known about their biology, but their siliceous fossils have been pretty well studied.

Silicoflagellate in plankton sample collected from Santa Cruz Municipal Wharf, 24 July 2015. © Allison J. Gong
Silicoflagellate in plankton sample collected from Santa Cruz Municipal Wharf, 24 July 2015.
© Allison J. Gong

Silicoflagellates are flat unicellular phytoplankters with two flagella that they use to swim. You can sort of see one flagellum sticking out at about 10:30 on the cell perimeter. You can see it better in this video clip (apologies for the background music). Watch as the flagellum wiggles and pushes the cell around.

Did you see the flagellum? How cool is that? Pretty fancy for a simple unicell, isn't it?

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