(Revised 3 January 2007)
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Microscopic plankton is best appreciated back at the lab. As I prepare a slide for viewing I never know just what to expect … plants (phytoplankton), animals (zooplankton), or both; larval forms of the tidepool critters or other unique species that live only in the plankton. Each tow is different. For this lecture demonstration, I used plankton caught by my students in the Santa Barbara Harbor. I videotaped this in my laboratory last month with our unique classroom videomicroscopy unit. The sample is dominated by phytoplankton--it is diatoms, like the big round Coscinodiscus, that are the base of so many marine food chains. It is these diatoms that are fed upon by small planktonic animals (like the small zooplanktonic crustaceans that are the food for filter-feeding whales, such as the gray whale). Another diatom, Pseudo-nitzschia, is one that the California State Department of Health is particularly interested in. This diatom produces a toxin, called domoic acid, which could affect humans if concentrated in the flesh of filter feeding shellfish consumed by man. Recent blooms of this species have caused the Department of Health to closely monitor it and even to close some bays to the consumption of their shellfish by humans. My students at SBCC are involved each semester in taking plankton tows from Santa Barbara Harbor for the Department of Health. Toxic substances from plankton are more commonly attributed to dinoflagellates. There are many species of dinoflagellates in our waters--most have little influence on humans but a few species are responsible for shellfish poisoning (and the mussel quarantine each year from May through October) and red tide. In addition, a few other species are bioluminescent and produce light if disturbed. When bioluminescent dinoflagellates bloom in our ocean the waves light up at night and produce an exciting spectacle. A few hours after dark, bioluminescent dinoflagellates make two chemicals (luciferin and luciferase) that glow for a few seconds when mixed. Each single celled dinoflagellate mixes these only when disturbed. If a predator tries to eat this dinoflagellate, it gets a flash of light and is usually scared away. When waves break the dinoflagellates are also disturbed and glow. These bioluminescent dinoflagellates are often cultured by biologists for research on this phenomenon. A warm water species, Pyrocystis fusiformis, is packaged and sold for educational purposes by Sunnyside Sea Farms in Goleta. Small vials of this bioluminescent dinoflagellate live for months and provide glowing light each night when gently shaken. [Vials of Pyrocystis fusiformis were distributed to the audience, the house lights turned off and everyone in the theater participated in a one-minute activity shaking their vials for a spectacular show of bioluminescence.] The plankton is the last of the treasures that can be introduced in this short lecture. There are thousands of other species that might be found in the lower tidepools here in Santa Barbara--most are visible but remember that there is a whole world right below your level of vision, the plankton. |
| © 2002 Genny Anderson (Revised 3 January 2007) |
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