We watched the wave push onto the beach, pause
momentarily, then pull back to sea, leaving it's pale trace on the
sand. Then we noticed that this wave left a green trace.
The north wind has been blowing well along the Oregon coast this
summer, driving the upwelling currents that
bring nutrient-rich water from below up to the sunlight. This
fertilization has fueled a dramatic growth of plankton, turning the
near-shore sea into a verdant, opaque plankton soup.
The word "plankton" is derived from the Greek for wandering
or drifting. Plankton are organisms that float with the currents,
with little or no ability to resist the water's flow. While some
plankton are very large, such as giant sea jellies, most plankton are
microscopic.
Many plankton have specialized floating mechanisms that keep them
afloat. Such mechanisms range from pulsing bodies and beating cilia
(small hairs) or appendages, to long spikes that increase the surface
area, to buoying bubbles of oil or air.
Familiar diatoms are a major component of plankton. Tiny diatoms
come in a wide variety of symmetrical shapes of dazzling silica
boxes. Another major group of plankton, dinoflagellates, are armored
one-celled organisms sporting two whip-like appendages, one wrapped around
and one dangling, that apparently help them orient in the water.
Diatoms and dinoflagellates, like many other plankton, are
"autotrophs," producing their own food from nutrients and
sunlight. Such phytoplankton are sometimes called the "grass of
the sea" because they are the primary producers in oceans. In
addition to making food, phytoplankton, like most land plants, give off
oxygen during photosynthesis. In fact, at least 80% of our planet's
atmospheric oxygen was produced by phytoplankton.
Zooplankton, a combination of microscopic animals and the tiny larvae
of larger animals (from crabs to sea
urchins), feed on the phytoplankton. In turn, tiny fish feed on the larger
plankton, then become food for larger predators—all the way up to whales
and people. Perhaps most non-swimming sea animals (such as barnacles
and clams) feed on the phytoplankton and zooplankton they filter from the
water ("filter feeders").
Although they can't effectively direct lateral movement—especially
against a current, many zooplankton can move weakly vertically in the
water: up at night and down during the day.
Sometimes conditions favor a population explosion of certain species of
dinoflagellates that produce chemicals toxic to humans—a "red
tide." Filter-feeders collect the dinoflagellates and the
toxins. While the toxins may not harm the filter-feeders, they can
greatly harm the people who eat the filter-feeders: paralytic shell
fish poisoning.
Next time you watch the green ocean waves, take a deep breath.
Even if you never eat seafood you partake of plankton's bounty.
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Visit our pages on related topics:
upwelling
el Niño
Dungeness crab
tideflat denizens
tidepooling
waves
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Wavecrest Discoveries can craft your personal discovery of this
delightful part of our world by customizing one of our distinctive guided
excursions. Our walks, tours,
and special activities are wonderful ways to
explore this fascinating region—and are the
perfect entertainment for guests.
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