|
Jellyfish “blooms”
- signs
of ailing seas
By Kelly G. Robertson
Last year, the Jellyfish “Bloom” in Perdido Bay and Old River was
impressive due to the volume and variety of individual species, and this
summer, jellyfish such as the Man O’ War arrived early at the beach and
Sea Nettles can be seen in large numbers inshore along both Perdido Key
and Santa Rosa Island. Blooms around the world are raising concerns
about the health of marine ecosystems. In the Gulf of Mexico, jellyfish
are competing with humans for the larvae of commercially important
species such as shrimp. In recent decades, humans’ “expanding influence
on the oceans has begun to cause changes, and the ‘blooms’ of jellyfish
may be occurring in response to these impacts,” said Claudia Mills of
the University of Washington in Seattle. As parts of the ocean are
increasingly disturbed and over-fished, jellyfish may be taking the
place of fish in the food web of the seas. “Jellyfish feed on the same
kinds of prey as adult and young fishes,” said Marsh Youngbluth, a
jellyfish researcher at the Harbor Branch Oceanographic Institution in
Fort Pierce, Florida, “so, if fish are removed from the equation,
jellyfish are likely to move in.
The formation of “blooms” is a complex process that depends on ocean
currents, nutrients, temperature and ambient oxygen concentrations. So,
over-fishing isn’t the only explanation for rapidly expanding jellyfish
populations, said scientist Monty Graham of the Dauphin Island Sea Lab
in Alabama. “Ecosystems in which there are high levels of nutrients as a
result of agricultural run off provide nourishment for the small
organisms on which jellyfish feed. In waters where there is over
fertilization, low oxygen levels often result, favoring jellyfish as
they thrive in less oxygen-rich water than fish can tolerate. The fact
that jellyfish are increasing is a symptom of something happening in the
ecosystem.” Graham cited the northern Gulf of Mexico, in which all
species of jellyfish are rapidly increasing.
Jellyfish lack basic sensory organs and a brain, but their nervous
systems allow them to perceive stimuli, such as light and odor, and
respond quickly. They feed on small fish and plankton that become caught
in their tentacles. Most jellyfish are passive drifters and slow
swimmers. They possess light-sensitive organs that do not form images
but are used to determine up from down, responding to sunlight. They
have limited control over movement and mostly free-float, but can use
the water pouch to accomplish vertical movement through pulsations of
the disc-like body. Many jellyfish have a lifespan of two and a half
months; few live longer than six months, but one species can live as
long as 30 years and another species, T. nutricula, is effectively
immortal.
Jellyfish are an important source of food to the Chinese community and
in many Asian countries. Gulf and southern Atlantic fisheries have even
begun harvesting cannonball jellyfish for export to Asian nations. Green
fluorescent protein in the jellyfish Aequorea Victoria has become a
useful tool in biology, used mainly by scientists studying in which
tissues genes are expressed. Jellyfish are also harvested for their
collagen, which can be used for a variety of applications including the
treatment of rheumatoid arthritis.
Jellyfish stings are not generally deadly, though some species of box
jellies can be fatal. Serious stings may cause anaphylaxis and may
result in death, and nonfatal stings are known to be extremely painful.
Care may include administration of an antivenin and other supportive
care such as required to treat the symptoms of anaphylactic shock.
There are three goals of first aid for uncomplicated jellyfish stings:
prevent injury to rescuers, inactivate the nematocysts (stinging cells),
and remove any tentacles stuck on the patient. Vinegar should be applied
for some stings, however it is not recommended for Portuguese Man O’ War
stings. In the case of sting on or around the eves, vinegar may be
placed on a towel and dabbed around the eyes, but not in them. Salt
water may also be used in case vinegar is not readily available. Fresh
water should not be used as a change in the pH can cause release of
additional venom. Rubbing the wound, or using alcohol, spirits, ammonia,
or urine will encourage the release of venom and also should be avoided.
A shower or bath as hot as can be tolerated can neutralize stings.
Once deactivated, the stinging cells must be removed. This can the
accomplished by picking off tentacles left on the body. After large
pieces or tentacles of the jellyfish are removed, shaving cream may be
applied to the area and a knife edge, safety razor, or credit card may
be used to take away any remaining nematocysts.
Beyond initial first aid, antihistamines such as Benadryl may be used to
control skin irritation. To remove the venom in the skin apply a paste
of baking soda and water and apply a cloth covering on the sting. If
possible, reapply paste every 15-20 minutes. Ice can be applied to stop
the spread of venom until either of these is available.
|
|
 |
|
Common
jellyfish found around Perdido Key
The
Portuguese Man O’
War,
also known as the bluebubble, bluebottol or the man-of-
war, is actually a colony of specialized polyps and medusoids.
It has an air bladder, or sail, that allows it to float on the
surface of the ocean, and is pushed by the winds and the current
as it has no means of propulsion. Below the main body dangle
long tentacles, sometimes reaching 30 feet lone, although 3 feet
is the average.
The sting from the tentacles is dangerous to humans, usually
causing excruciating pain, have even been the cause of several
deaths. Detached tentacles and specimens which wash up on shore
remain dangerous and can sting just as painfully weeks later.
Medical attention is usually necessary, especially in extreme
cases.
The best treatment for a sting is to apply hot water to the
affected area, which eases the pain of a sting by denaturing the
toxins. Ice is also effective, reducing the activity of the
toxins and the sensation of the area of skin affected.
Additionally, ice constricts blood vessels, reducing the speed
at which the venom travels to other parts of the body.
Loggerhead Turtles and sea slugs commonly feed on the Man O’
War.
 |
 |
|
The stinging
Sea Nettle
is a bell-shaped,
semi-transparent jellyfish that usually has small, white dots
and reddish brown stripes. The nettle’s sting is rated from
“moderate” to “severe” and can be deadly to smaller prey; it is
not, however, potent enough to cause human death except by
allergic reaction. Most often, the sting causes a painful rash
typically persisting for about 20 minutes. The sting can be
effectively neutralized by misting vinegar over the affected
area, which keeps unfired nematocysts from activating and adding
to the discomfort.
|
|
The
Moon Jellyfish
(common jellyfish, saucer jelly, or crystal jellyfish) is
translucent, can be 10-16 inches across, and has characteristic
patterns of color within its body. Like other jellyfish, it is
capable of only limited motion and drifts with
|
 |
|
the current. The Moon jelly is an inshore species that can be
found in places like estuaries and harbors. It prefers mildly
cold salt water with consistent currents.
|
|
The adult medusa of the Moon jelly has an umbrella margin
membrane and tentacles that are attached to the bottom. It has
four bright circular gonads that are under the stomach. It is a
common food source for a variety of predators, including the
Ocean Sunfish, the Leatherback Sea Turtle, and other jellyfish
species. They are also hunted by some birds. Moon jellies are
human food sources in countries such as China, Philippines,
Thailand, Malaysia and Indonesia.
|
 |
|
Ctenophores
(pronounced “teen-o-fors”, or “comb jellies”, can be found as
easily far out to sea as they can near the shore. Most of the
150 species of Ctenophores prefer warmer waters although a few
species live deep down in the sea and a few others are found
around the poles.
Comb Jellies can occur in huge numbers and are known to effect
fisheries because they feed on fish egg and hatchlings.
Normally, comb jellies feed on copepods or the larval forms of
various other marine animals including Oysters. They sometimes
accumulate in such vast numbers that they have a negative effect
on an areas’ Oyster crop. They do not, however, produce harmful
stings to humans.
Some species of comb jellies are able to glow with a faint
phosphorescent light that is generally visible only at night.
Although almost transparent, the external surfaces of
ctenophores have eight rows of cilia (small, hair-like
structures) that are used for swimming and to maintain correct
orientation in the water. |
|
