What’s all the fuss about bioluminescence? What IS
bioluminescence?
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| Sunset over White Gulch on Tomales Bay. Photo by Casey Newman, 2011, All Rights Reserved. |
It’s the production of light by living organisms. It can be
used to attract prey, to communicate, and to help an organism blend in with its
surroundings. Bioluminescence is also responsible for the glow that can
sometimes be seen on moonless nights in the waters of the ocean. In several
places in the world, including our own Bay Area, conditions are perfect for an
annual “bloom” of dinoflagellates, a type of single celled organisms that are
bioluminescent.
Dinoflagellates are a type of unicellular planktonic
organism (whew, what a mouthful). They drift with the currents of the ocean
(planktonic), using two whip-like structures (flagella) to move their
single-celled selves around a bit. They can photosynthesize, or get energy from
sunlight, but some dinoflagellates also eat other, smaller organisms. Most of
them have armored plates made of cellulose for a cell wall, which makes them
tough for their size (and also beautiful under a microscope). Some
dinoflagellate species cause red tides, and release toxins that are harmful to
humans. Other species, like the species that is found in Tomales Bay certain
times of year, are bioluminescent.
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During certain times of the year, strong winds push the top
layer of coastal water offshore, allowing cold, nutrient-rich water to flow up
from the ocean floor. This is known as upwelling, and it is responsible for the
surge in nutrients that feed an explosion in the population of single celled
algae. One species of those algae are the dinoflagellates that produce the
light we see on Tomales Bay. Their bioluminescence can occasionally be seen
year round, but tends to be strongest in the summer and early fall. The amount
of nutrients in the water affects when we can see the bioluminescence and how
long it lasts.
The waters of Tomales Bay are a perfect location for viewing
the bioluminescence. Tomales Bay has a narrow opening which limits the amount
of water that is exchanged during the tides, concentrating the dinoflagelates
in the bay. Beds of eelgrass, a plant with long blades, further trap and
concentrate the dinoflagellates in the shallow parts of the bay. The northern
end of the bay is relatively undeveloped, which keeps light pollution from
washing out the flashes of green light when the organisms are moved.
A paddle through the bioluminescent waters of Tomales Bay is
an amazing experience. As we paddle through the water, our boats, paddles, and
even hands can jostle the organisms and make them flash. The bioluminescence
does not hurt the dinoflagellates, and they can continue to emit flashes of
light for hours. On especially dark nights, fish can be seen setting off the
bioluminescence as they swim through the waters underneath our boats. The
peaceful waters of Tomales Bay provide a protected location filled with
wonderful wildlife to paddle past, and the bioluminescence is truly
breathtaking.
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| Sunset on Tomales Bay. Photo by Casey Newman, 2011, All Rights Reserved. |
