RED TIDE
Background: Algae are vitally important to
marine ecosystems, and most species of algae are not harmful. However, under
certain environmental conditions, microscopic marine algae called Karenia
brevis (K. brevis) grow quickly, creating blooms that can make the ocean appear
red or brown. People often call these blooms “red tide.”
K. brevis
produces powerful toxins called brevetoxins, which have killed millions of fish
and other marine organisms. Red tides have damaged the fishing industry,
shoreline quality, and local economies in states such as Texas and Florida.
Because K. brevis blooms move based on winds and tides, pinpointing a red tide at
any given moment is difficult.
Red tides
occur throughout the world, affecting marine ecosystems in Scandinavia, Japan,
the Caribbean, and the South Pacific. Scientists first documented a red tide
along Florida’s Gulf Coast in fall 1947, when residents of Venice, Florida,
reported thousands of dead fish and a “stinging gas” in the air, according to
Mote Marine Laboratory. However, Florida residents have reported similar events
since the mid-1800s.
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| Red Tide |
Karenia
brevisK. brevis is a microscopic, single-celled,
photosynthetic organism that can "bloom" (see algal bloom) frequently
along Florida coastal waters. Each cell has two flagella that allow it to move
through the water in a spinning motion. K. brevis naturally produces a suite of
potent neurotoxins collectively called brevetoxins, which cause
gastrointestinal and neurological problems in other organisms and are
responsible for large die-offs of marine organisms and seabirds. K. brevis is
unarmored, and does not contain peridinin. Cells are between 20 and 40 μm in
diameter.
Ecology and distribution
In its
normal environment, K. brevis will move in the direction of greater light and
against the direction of gravity, which will tend to keep the organism at the
surface of whatever body of water it is suspend within. Cells are thought to
require photosynthesis to obtain nutrition. Its swimming speed is about one
metre per hour.K. brevis is the causative agent of Red Tide, when K. brevis has
grown to very high concentrations and the water can take on a reddish or
pinkish coloration. The region around southwest Florida is one of the major
hotspots for red tide blooms. Red Tide outbreaks have been known to occur since
the Spanish explorers of the 15th century, although not nearly as common, or for
as lengthy a duration as now. Some sources say Florida red tide blooms are
about 10- to 15-fold more abundant than they were 50 years ago. Algal species
that have harmful effects on either the environment or human health are
commonly known as Harmful Algal Blooms (HABs). HABs are harmful to organisms
that share the same habitat as them, though only when in high concentrations.
Detection
Traditional
methods for the detection of K. brevis are based on microscopy or pigment
analysis. They are time-consuming and typically require a skilled microscopist
for identification. Cultivation based identification is extremely difficult and
can take several months. A molecular, real-time PCR-based approach for
sensitive and accurate detection of K. brevis cells in marine environments has
therefore been developed. Another upcoming technique for the detection of K.
brevis is multiwavelength spectroscopy, which uses a model-based examination of
UV-vis spectra. This particular protist is known to be harmful to humans, large
fish, and other marine mammals. It has been found that the survival of
scleractinian coral is negatively affected by brevetoxin. Scleractinian coral
exhibits decreased rates of respiration when there is a high concentration of
K. brevis.
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| Karenia Brevis |
Harmul Algal Blooms (HABs)
Harmful algal blooms, or HABs, occur when colonies of algae—simple plants
that live in the sea and freshwater—grow out of control while producing toxic
or harmful effects on people, fish, shellfish, marine mammals, and birds. The
human illnesses caused by HABs, though rare, can be debilitating or even fatal.
While many people call these blooms 'red tides,' scientists prefer the term
harmful algal bloom. One of the best known HABs in the nation occurs nearly
every summer along Florida’s Gulf Coast. This bloom, like many HABs, is caused
by microscopic algae that produce toxins that kill fish and make shellfish
dangerous to eat. The toxins may also make the surrounding air difficult to
breathe. As the name suggests, the bloom of algae often turns the water red.
HABs have been reported in every U.S. coastal state, and their occurrence
may be on the rise. HABs are a national concern because they affect not only the
health of people and marine ecosystems, but also the 'health' of local and
regional economies.
But not all algal blooms are harmful. Most blooms, in fact, are beneficial
because the tiny plants are food for animals in the ocean. In fact, they are
the major source of energy that fuels the ocean food web.
A small percentage of algae, however, produce powerful toxins that can kill
fish, shellfish, mammals, and birds, and may directly or indirectly cause
illness in people. HABs also include blooms of non-toxic species that have
harmful effects on marine ecosystems. For example, when masses of algae die and
decompose, the decaying process can deplete oxygen in the water, causing the
water to become so low in oxygen that animals either leave the area or die.
Scientists at the National Ocean Service have been monitoring and studying
this phenomenon for a number of years to determine how to detect and forecast
the location of the blooms. The goal is to give communities advance warnings so
they can adequately plan for and deal with the adverse environmental and health
effects associated with these 'red-tide' events.
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| HABs or Scientific name of "Red Tide" |
Assessing the Impact on Public
Health
In
addition to killing fish, brevetoxins can become concentrated in the tissues of
shellfish that feed on K. brevis. People who eat these shellfish may suffer
from neurotoxic shellfish poisoning, a food poisoning that can cause severe
gastrointestinal and neurologic symptoms, such as tingling fingers or toes.
The human
health effects associated with eating brevetoxin-tainted shellfish are well
documented. However, scientists know little about how other types of
environmental exposures to brevetoxin—such as breathing the air near red tides
or swimming in red tides—may affect humans. Anecdotal evidence suggests that
people who swim among brevetoxins or inhale brevetoxins dispersed in the air
may experience irritation of the eyes, nose, and throat, as well as coughing,
wheezing, and shortness of breath. Additional evidence suggests that people
with existing respiratory illness, such as asthma, may experience these
symptoms more severely.
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| Fish Carcasses that are poisoned by "Red Tide" |
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| A warning about "Red Tide" |
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| Warning! |
This is a
kind of an interesting phenomenon that God has given to us. Although it’s
dangerous to us but we have to admit that God is awesome…..
http://en.wikipedia.org/wiki/Karenia_brevis
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