Transcript No Slide Title

Introduction
Harmful algal blooms, often called red tides, occur worldwide from Norway to New Zealand. They can cause fish
kills and human health hazards and are caused by phytoplankton or microalgae that produce potent toxins. Less than
2% of microalgal species produce these toxins, which can affect the nerves, blood or immune systems of animals.
Microalgae are best known for their role in forming the base of the food web and producing oxygen that is released to
the atmosphere.
When these single-celled microscopic plants, which contain chlorophyll and other pigments, reach high
concentrations (blooms) in seawater, they can discolor the sea surface and make it appear red, brown, yellow or
green. For one species, there have to be about one million cells per liter of seawater to notice the discoloration.
Discolored Seawater
In California coastal waters there are several examples of discolored water caused by
dinoflagellates. Dinoflagellates are very slow-swimming microalgae that can move up
and down in the water in response to light, gravity and other factors. At high
concentrations, the dinoflagellate Lingulodinium polyedrum produces a vivid orange-red
color. According to the fossil record, this dinoflagellate has existed for more than 50
million years.
Red water in California
In the North Sea, the discoloration caused by the dinoflagellate Gymnodinium cf.
mikimotoi is greenish. This type of harmful algal bloom can cover over 30,000 km
and is a major threat to salmon and trout cage cultures. [The presenter may want to
give a concrete example of how big this really is.]
The Gulf of Mexico (GOM) has more than 40 species of
microalgae that produce toxins. Not all of these species form
blooms. There are also non-toxic microalgae that form blooms
and discolor seawater.
The most common and frequent GOM coastal blooms that
discolor seawater are caused by the blue-green alga
Trichodesmium erythreum and the toxic dinoflagellate
Gymnodinium breve.
Both of these species cause the water to look brownish-red to yellow
depending on the state of the bloom. Commercial airline pilots have
occasionally reported Trichodesmium blooms as oil slicks. The size of these
blooms in the Gulf of Mexico can exceed 30,000 km and occur from Mexico to
Florida.
In many harmful algal blooms, the causative organism is not found just at the
surface. It can be distributed throughout the water column down to more than 50
meters. In culture, G. breve cells concentrate at the surface when the lights are on,
yet cells are distributed throughout the culture vessel; this is evidenced by the cloudy
nature of the water. In the dark, the population is generally dispersed evenly
throughout the water. Thus, not all red tides are red and not all of them are alike
because they are caused by different species.
Fish kills are common during GOM red tides. The first fish kills are often spotted
offshore and involve bottom fishes such as grouper, snapper, hogfish and eels. As
winds and currents move the red tide inshore, other fishes such as catfish, mullet and
drums are affected. The toxin produced by G. breve is a neurotoxin and affects nerve
transmission. It paralyzes fish so they cannot breathe.
How long have fish kills been around?
In 1530, the Spanish explorer Núñez Cabeza deVaca recounted
what the local Indians told him about seasonal fish kills off
Tampa Bay, Florida. This is the first written record we have of
fish kills in the GOM.
In the 1880s, reports of fish kills on eastern GOM sailing routes
were common. Captains would notice that fish kept in the ship’s
live wells were dying even before the vessel encountered
discolored water. They referred to it as poisoned water.
In addition to fish, invertebrates also die during red tides.
Invertebrates such as scallops and sponges are impacted by red
tides either directly by poisoning or in-directly by reduction of
water quality.
Red tides also affect birds. The first record of sick and dying ducks and
cormorants comes from an account of the 1880 red tide. In 1977, scientists
documented that toxic shellfish could make ducks sick and even cause
death.
Manatees are an endangered species in Florida and in 1996 a record number were
killed by boats, barges, locks, and red tide. Of the 415 manatees that died in southwest
Florida during the winter/spring months, 149 are attributed to red tide.
Their deaths were associated with the unusually prolonged red tide in the Pine Island
Sound and Marco Island areas. In the last 25 years, there have been only two years
(1982 and 1996) with documented mass moralities of manatees.
In both of these years,
there were unique
contributing factors: an
uncommon winter red
tide, high salinity in the
outer reaches of Pine
Island Sound, and
prolonged high cell
counts of G. breve in the
higher salinity areas.
Areas with <27 parts per
thousand (ppt) salinity
(open ocean seawater is
about 35 parts per
thousand) did not
support red tide and
appeared to be safe
havens for manatees in
that estuarine system. G.
breve are partial to high
salinity. In other areas of
the GOM, G. breve is
able to tolerate salinities
of less than 25 ppt.
Scientists who
tested tissues from
dead manatees
determined that
the manatees were
exposed to red tide
toxin levels high
enough to kill
them. They found
toxin in liver,
kidney, spleen and
brain tissue, as
well as in the
stomach contents.
Scientists continue
to study why the
manatees died and
how the red tide
toxin killed them.
Effects of Gymnodinium breve on Humans
In addition to affecting marine animals, Florida red tides can affect humans in several ways.
Unlike deaths associated with Paralytic Shellfish Poisoning (PSP), it is important to know
there have been no human deaths attributed to a GOM red tide. G. breve, the Florida red tide
organism, can make shellfish, such as clams and oysters, toxic to humans who eat them.
These shellfish filter microalgae and other food from the water and can accumulate the
toxins.
The Florida Department of Environmental Protection has a Biotoxin Control Plan to
regulate the harvesting of shellfish during red tides. Its primary goal is to safeguard
public health. Since this plan has been implemented, no human illnesses have
occurred from eating oysters, clams, or other shellfish taken from regulated
harvesting areas. However, illnesses have been documented in people who have
eaten shellfish that were illegally harvested.
How long have red tides been around?
There is a documented case of a man becoming ill in 1880 after consuming
oysters from the Tampa Bay area during a fish kill. He experienced symptoms
identical to those known for Neurotoxic Shellfish Poisoning (NSP) caused by G.
breve. Some of these symptoms include tingling or numbness of the mouth and
throat, muscular aches, dizziness and gastrointestinal distress.
Another human impact is caused by the red tide aerosol. Toxic substances
become airborne in seaspray, and these substances cause some people to
cough, get teary eyes, or feel a "tickle" in their throats. A man walking on a
Sarasota beach during one red tide episode protected himself by using a wet
bandana around his face to trap particles and droplets of seawater.
How long has this been going on?
Accounts of the red tide aerosol date back to 1916, when beach-goers referred to a "gas"
with no odor that caused cold-like symptoms not long after visits to the beach.
Sometimes the aerosol is confused with odor from beached dead fish. In 1996, some
people working on the beach wore gas masks to alleviate the smell of rotting dead fish.
Red tides that lasted 3–4 months over several west Florida counties in the 1970s
caused a 15–20 million dollar loss in revenue from tourism and fisheries. Beach
hotels have even resorted to advertising the daily red tide status to attract business
or to avert patrons from leaving because of the bad publicity associated with red
tide. The 1987 North Carolina episode caused a $25 million loss to the shellfish
fishery alone because of harvesting closures.
Gymnodinium breve Blooms in the Gulf of Mexico:
Introduction
More than 40 toxic phytoplankton species exist in the GOM; most are dinoflagellates. Only
one of these causes fish kills, toxic shellfish poisoning, and an irritating aerosol—G. breve. It
is 1 Ú1000 of an inch long, yellow-green, and has two whip-like appendages that propel and
direct it through the water. It can swim at speeds of 1 meter per hour. In Florida, G. breve likes
high salinity and does not do well in back brackish (lower salinity) areas. G. breve can also
tolerate a wide temperature range.
The highest concentration of G. breve cells ever recorded was 1 billion cells per liter in Texas
waters. Concentrations in Florida bays have been known to reach the hundreds of millions of
cells per liter.
Although more than 70 % of G. breve blooms occur in late summer/fall and about 92%
of them have occurred off Florida’s west coast, G. breve is distributed throughout Gulf
coastal and open waters all year long at very low concentrations (<1,000 cells per liter).
Texas has had five G. breve red tides since 1935 (1935 is onerous because the species was
not described until 1948). In Texas waters, blooms seem to occur on a ten to 20-year
cycle, but they are almost an annual event in Florida Gulf coast waters. The first G. breve
blooms off Louisiana, Mississippi and Alabama occurred in 1996 after a red tide was
detected in north-western Florida waters.
Most G. breve red tides occur from Clearwater to Sanibel,
Florida. This area can be termed high-risk. Red tides occurred in
the high-risk area in 20 of the 21 years between 1975 and 1995.
Currents, eddies, water circulation patterns and winds appear to influence the occurrence
and distribution of blooms from Mexico to North Carolina. Before 1973, scientists thought
red tides started inshore near passes because that is where people noticed the discoloration
and floating dead fish. But an analysis of federal and state data from sampling cruises on the
West Florida Shelf showed that G. breve oncentrations start to increase offshore before they
are recorded inshore. A zone of initiation of 18 to 74 km was suggested. Data from the
1976, 1977, 1979 and 1985 red tides confirm that initiation is offshore. Often, red tides
initiate off-shore and stay offshore without inoculating inshore areas (for example,
September 1996 to February 1997).
For example, data from 1976 show G. breve concentrations increasing offshore on the midshelf before being found inshore.
The offshore initiation of red tides is associated with the intrusion of oceanic
(salinity around 36 parts per thousand) water. An analysis of physical
oceanographic data for 1967 to 1976 showed that six of seven red tides were
directly preceded by an oceanic intrusion of Loop Current water. The Loop
Current is part of the Gulf Stream System—it is the dominant current in the
eastern GOM.
There are four identifiable stages in the development of G. breve blooms in Florida
coastal waters. First there is initiation when G. breve is inoculated into mid-shelf
waters. This is followed by growth which results in increasing concentrations of G.
breve cells. Increased cell concentrations can then be maintained and even
concentrated in the maintenance phase, thus forming blooms. In the fourth stage,
blooms may dissipate or disperse and terminate, or be transported to a new area.
Life Cycle of Gymnodinium breve
We do not know the complete life cycle of G. breve, but we are trying to determine whether this
organism, like other bloom organisms, produces a bottom resting stage called a cyst. Cysts can seed
or inoculate blooms offshore when there is intrusion of oceanic water. Cyst-like cells have been
observed in culture and in blooms but scientists have not been able to induce the cyst stage in
culture. Life cycle studies have demonstrated that G. breve has a sexual cycle and can produce
zygotes (cells formed from the fusion of two gametes). Researchers are investigating whether these
zygotes produce resting cysts that settle to the sea floor. An alternate possibility is that G. breve has
a resident population in the water (rather than on the seafloor) and this population acts as
the inoculum for blooms, and is maintained by the unique circulation pattern on the west Florida
shelf.
Transport of Blooms
Florida red tides were actually entrained and transported from the Gulf of
Mexico to the South Atlantic in 1972, 1977, 1980, 1983, and 1987 via the Gulf
Stream System. Transport probably occurred earlier than that, but was not
documented until 1972. For example, a Jacksonville newspaper reported beached
dead fish and beach goers experiencing respiratory irritation in 1946.
In 1987, a G. breve bloom was transported by the Gulf Stream up to the
Carolinas. AVHRR satellite imagery of the Gulf Stream off North Carolina shows
an oceanic filament intruding onto the North Carolina shelf. In the color-enhanced
image, the warmer Gulf Stream water is red.
Now North Carolina officials and scientists monitor the Gulf Stream for G. breve.
Pollution
Are Florida red tides caused by pollution? Although they start offshore in oligotrophic
(low nutrient) waters, they can be transported inshore by winds and currents. Once red
tides get inshore into bays, people often ask if nutrient runoff into the bays increases the
intensity or duration of blooms. Many bay areas are poorly flushed so blooms can reach
high concentrations. Nutrient enrichment could increase the intensity of the bloom, but at
the same time, blooms crash or terminate in enriched bays. Thus, the effects of
eutrophication are not yet clear.
Can Florida red tides be controlled? In the 1950s, federal and state regulators and
scientists tried to control inshore concentrations of red tide by applying copper sulfate, an
algicide. They applied 105 tons to a coastal area greater than 30 miles. A panel of scientists
and managers judged the experiment to be unsuccessful. Why? Because the toxin was
released from the cells and more G. breve reoccupied the treated area from surrounding
areas (Recall that G. breve is always present in the water)
•
•
•
•
Red tide cells release toxins when cells are killed
Toxins are stable in seawater for weeks
Offshore red tides repopulate inshore waters
Red tides cover hundreds to thousands of square miles down to 50 meters deep
Why did officials attempt this? In a public media demonstration, copper pennies were
put into an aquarium tank filled with G. breve. The organisms died and settled out. At this
time they did not know that the toxin was released. If they had put fish into the aquarium,
the fish would have died too.
More recently, clays have been suggested as a control agent and are currently being
studied. However, the same potential problems exist. Scientists will first study the use of
clays in the laboratory, then in big outdoor tanks. They need to determine whether clay,
which draws out particles in seawater, will release the toxins from G. breve cells and cause
problems for bottom-dwelling animals. How much clay, what type of clay, and how many
treatments also need to be assessed.
Predicting Gymnodinium breve Red Tides
Can red tides be predicted? Can scientists predict and track red tides with satellite
sensors that record sea surface temperature and color? The Loop Current, eddies and
filaments can be visualized using sea surface temperature patterns. This means the
physical processes that set up or move a red tide can be followed depending on the
availability and quality of the satellite imagery.
Red tides, represented by higher levels of chlorophyll (cellular pigment) in sea surface
waters, have been detected in analyses of historical Coastal Zone Color Scanner (CZCS)
imagery. The CZCS is just one of many types of satellite monitors. Some CZCS images
clearly show G. breve blooms in areas and time slots that fit the historical database. The
potential use of satellite imagery in predicting red tides is good news for scientists.
Can scientists predict red tides?
A federally funded program called Ecology and Oceanography of Harmful Algal Blooms
(ECOHAB) for Florida and other GOM projects will address predicting blooms. In Florida,
scientists will use moored buoys to study shelf circulation patterns and physical-chemical
variables in relation to G. breve bloom development and movement on the continental shelf.
ECOHAB: Florida is a collaborative program with 23 investigators from 13 institutions.
Can Florida red tides be managed? Yes.
We manage shellfish harvesting areas, and since we started the biotoxin control plan, there have
not been any human illnesses from regulated harvesting areas. However, there have been illnesses
associated with shellfish that was illegally harvested from prohibited areas. This problem will have
to be addressed through a public education and outreach program.
We can also help the aquaculture industry with site-planning and risk management by helping
them select the most appropriate species to culture in a known red tide area. We can help them
understand red tide effects so they know what to do if a red tide does occur.
Public education is a key component in management. The public needs to be in-formed about red
tides and their effects on marine ecosystems and humans. This needs to be a continual effort. The
public needs to be updated during red tide events and community volunteers can help report events
and sample discolored water.
Prediction and tracking of red tides is within our grasp. Forewarning can initiate contingency plans
for regulatory agencies, local governments, and local businesses.
Offshore monitoring during red tide events is necessary to detect the possibility of reinoculating
inshore areas from the offshore populations.
Fish-removal strategies need to be developed and tested to better handle beached and floating dead
fish. The accumulation of carcasses influences whether people can use the beaches and continue
recreational activities, such as boating and fishing.
Eradication of red tide is a popular topic of discussion. If there are isolated
pockets of G. breve populations on the sea floor, can they be controlled before
a bloom develops offshore—before it becomes a threat to inshore marine and
human resources? Once a bloom develops, treating large areas of the ocean
does not seem practical nor feasible. One often-raised question is whether a
small embayment can be effectively treated to improve the quality of life for
local residents and businesses.
Reducing nutrient input into our estuaries will help the resiliency and health
of the system, but it will not stop red tides from occurring nearshore. Inshore
G. breve blooms are inoculated from low-nutrient, offshore waters and as long
as the nearshore waters are within a certain salinity range, red tides will occur.
The question becomes not whether they will occur but how long they will last
and how intense they will be.
Blue-green bloom