Many people have experienced the roll of a boat on a rough body
of wateralong with a queasy stomach and uneasy legs. The pitch
of the boat and the distasteful physiological effects can be blamed
on fluid motion. Luckily, people can escape an uncomfortable boat
ride by eventually returning to port. But for organisms that live
in the ocean there is no escape. They exist continuously in a dynamic
fluid environment, which scientists do not yet fully understand.
Scripps marine biologist Michael Latz and his graduate students
are studying the effects of fluid motion on single-celled algae
known as dinoflagellates.
In the ocean, turbulence is created by wind, waves, tides, and
currents. This turbulent motion not only carries around plankton,
including dinoflagellates, but also directly affects their biology.
"We know essentially nothing about the physiological effects of
flow on marine cells," explains Latz. "But we do know that dinoflagellates
are among the most flow-sensitive cells, far more so than mammalian,
plant, or insect cells."
Dinoflagellates commonly occur throughout the
world's oceans and have several interesting characteristics.
Certain species form red tides, which occur
when populations congregate and reproduce so densely that they discolor
the water red or brown. Some dinoflagellate "blooms" can
degrade water quality and some produce toxins that are harmful to
other marine organisms, such as seals or whales. The same toxins
also affect humans through paralytic shellfish poisoning.
Many dinoflagellate species are bioluminescent,
emitting bright flashes of light at night in response to agitation.
In large accumulations, they produce "phosphorescent seas" in which
crests of waves, surf, and waters around boats and swimming organisms
glow electric blue. In San Diego, a common dinoflagellate named
Lingulodinium polyedrum is responsible for these light displays,
which are most prominent during red tides.
Although luminescent dinoflagellates have been studied at Scripps by Latz for several years and by others since the 1950's, some ofthe cellular and environmental factors affecting the bioluminescent response are stil not understood.