Red_tides

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





KEYWORDS

red tides, red tides tutorial, phytoplankton blooms, algae blooms, algal blooms, oxygen

depletion, hypoxia, fish kills, human poisoning, toxic tides, harmful algae bloom, HAB,

HAB tutorial, brevetoxin.



Word count: 3,150



Toxic Red Tides Threaten Us All1



Red tides, also known as harmful algae blooms (HABs), occur around the world. They

release toxic wastes that can kill plants and animals, and they can cause death to humans

who eat marine life contaminated by the tides. Cooking tainted food does not kill or alter

the toxins. Although these blooms occur naturally, many suspect that human pollution

and other activity in coastal waters are contributing to them.



We often hear of water pollution problems caused by brown and red tides, excessive

plankton or algae growth or propagation, called blooms, that discolor the water.



While blooms are a natural phenomena, many scientists are concerned that human

activity (read pollution) is increasing both the number and extensiveness of the blooms

around the world. Blooms are a problem that created when:

 Nutrients in the water, such nitrogen and phosphates, trigger tiny marine plants

called phytoplankton to rapidly reproduce;

 The rapid increase in plant food triggers an increase in reproduction by

zooplankton, tiny marine creatures, and attract other herbivores to the area;

 Other marine plants are either stressed or begin to die as the dying as the

phytoplankton bloom block the sunlight necessary for plant photosynthesis;

 Once the nutrients triggering the phytoplankton bloom are consumed, the

phytoplankton start to die off;

 Zooplankton, who can’t swim against a current, also start to die off as their

phytoplankton food source disappears;

 Bacteria begin to consume the dead plants, zooplankton, and other creatures,

which removes life-giving dissolved oxygen in the waters and can creat an

anaerobic condition -- a complete loss of oxygen;

 Marine animals that can’t leave the oxygen-starved waters, such as zooplankton,

shell fish, crustaceans, and small fish, begin to die;

 In addition, some phytoplankton produce as waste products water-borne toxins

that can accumulate in the fish, crustaceans, and water foul that consume them,

and air-borne toxins that can cause respiratory problems in mammals, including

humans. These toxic blooms also can be poisonous to humans higher up on the

food web (or chain or matrix), who eat the tainted seafood.





1

The article is based on materials, used with permission, on the website of the Delaware Department of

Natural Resources, Tidewater Ecosystem Assessment Division. See

http://www.dnr.state.md.us/bay/hab/brown_tide.html .





-1-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





For some reason, we lay folk incorrectly call these mass blooms brown or red ―tides.‖

The reference to tides was incorrectly coined because initially it was thought that tides

helped create the blooms. Phytoplankton blooms have nothing to do with tidal actions,

but the blooms may be distributed by tidal currents and ocean currents as they expand

their habitat along a coastline. Most blooms usually are not harmful; and even toxic

species that could be harmful may never reach the densities required to discolor the water

or concentrate their toxins at harmful levels.



We discuss this a rapid growth of plankton, also called algal, algae, or phytoplankton

blooms, in a tutorial on ‖brown tides.‖ In this tutorial, we discuss a special form of

bloom called ―toxic red tides.‖



For purposes of this tutorial, we place these ―blooms‖ in three categories;

 Brown blooms – Harmless but annoying population explosions that discolor the

water but don’t cause any harm to local marine life,

 Brown harmful algae blooms – Called HABs for short, these population

explosions are not toxic but in extreme cases can block sunlight, which affects

other plant life, or contribute to the depletion of dissolved oxygen in the water

when they die and bacteria consuming them, whih adversely affects all local

marine life; and

 Red blooms – Automatically classified as HABs, these blooms produce

neurotoxins that can be concentrated in creatures in a food chain or released into

the atmosphere. Both situations have been injurious to humans.



Many people use the terms ―red‖ and ―brown‖ interchangeably, although neither type of

bloom has to be either brown or red. Many are colorless. Just remember, scientists prefer

the term HABs if a bloom injures the environment, whether toxic or non-toxic.



In this tutorial, we discuss toxic blooms or ―red tides.‖ Non-toxic ―brown‖ blooms,

whether regarded as HABs or not, are discussed in a tutorial on ‖brown tides.‖ We

discuss the importance of plankton, phytoplankton or plant photosynthesis and the marine

food chain in another tutorial on marine life. We also should note that while we are

concentrating on brackish bay and saline ocean phytoplankton blooms, phytoplankton

blooms occur in fresh waters as well.

BCC/Red tides/Bloom_process









-2-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc









A toxic algae, prorocentrum concavum.



The role of phytoplankton in our

lives

Algae and other phytoplankton are

microscopic, single-celled plants that

live in fresh and salt water.

Phytoplankton are called energy

producers because they create matter

through the chemical process of

photosynthesis. They such, they are

regarded as the basis of the marine the

food web. They also produce 50 to 60

percent of our planet’s oxygen. Simply

put, without phytoplankton, higher life

on this planet would not exist.



Occasionally, phytoplankton grow very

fast or "bloom" and accumulate into

dense, visible patches near the surface

of the water. During a bloom, a single-

celled plant can replicate itself one

million times in two to three weeks.

This concentration of sun-seeking

phytoplankton causes the water to

become discolored by the various

pigments the plants use to trap sunlight.

The terms brown and red tides come

from certain phytoplankton species that

contain reddish brown or red pigments and "bloom" so profusely – as many as 7 billion

plants per square meter -- that the water appears to be colored reddish brown, red.

However, many blooms are also pink, violet, orange, yellow, blue, and green.









-3-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc









P. Alejandro Díaz and Ginny

Velasquez

A ―red tide‖ or algae bloom is quite evident in the Pacific Ocean off La Jolla, Calif.

BCC/Red-Tide-La-Jolla









Wikipedia



Bioluminescent red tide in 2005 at a beach in Carlsbad, California, shows brilliantly glowing crashing

waves (blue) containing billions of Lingulodinium polyedrum dinoflagellates.

BCC/Red-tides-bioluminescence



Toxic harmful algal blooms (HABs)

Some species of algae produce neurotoxins, which at high cell concentrations reached

during some blooms can have severe biological impacts on wildlife. Scientists refer to

algal blooms known to produce biotoxins as Harmful Algal Blooms (HABs), a term they

prefer over ―red tides‖ (although some scientists still use the term). However, as noted,

non-toxic or brown blooms that adversely affect local habitats with their profusely

accumulated biomass also are called HABs. Toxic and non-toxic HABs occur in waters

around the world.







-4-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





Three common signs of a red tide bloom are.

 Discolored water (although this also could be the result of non-toxic brown

tides);

 Dead fish (although this also could be the result of low dissolved oxygen or DO

in the water unrelated to brown or red tides); and

 Fish breathing with difficulty (although this also could be the result of low

dissolved oxygen in the water unrelated to brown or red tides).



In other words, the three above examples indicate, but aren’t conclusive, that red tides are

occurring. The only sure way of determining a toxic red tide is to identify the

phytoplankton in the water, since most phytoplankton do not generate neutotoxins.



Life-threatening toxic red tides

About 85 of the 4,400 species of algae generate potent neurotoxins that can be transferred

through the food web, where they can afflict and even kill higher forms of life, such as

zooplankton, shellfish, fish, birds, marine mammals, and humans that feed either directly

or indirectly on them.2



Humans have been severely affected by toxic blooms by eating contaminated seafood,

most commonly mussels and clams. Some of the people who ate tainted shellfish during a

1987 bloom in North Carolina suffered from sweating, anxiety, dizziness, muscular

aches, diarrhea, vomiting, and abdominal pain.



The same year, another toxic HAB bloom occurred in Nova Scotia, where four people

died from eating contaminated shellfish and another 150 suffered from comas, seizures,

short-term memory loss, headaches, and dizziness. Many other incidents have also been

reported in past years.



An example of a red tide - Karenia brevis

In Florida, scientists from the MOTE Laboratory and the Florida Fish and Wildlife

Research Institute believe that the one of the causes of the state’s red tides is Karenia

brevis, a phytoplankton dinoflagellate species that occurs naturally in Gulf of Mexico

waters. It may have been responsible for the deaths of 150 manatees in 1996.3









2

―The Gulf of Mexico Dead Zone and Red Tides,‖ by Elizabeth Carlisle, Tulane University,

http://www.tulane.edu/~bfleury/envirobio/enviroweb/DeadZone.htm



3

MOTE Laboratories article (date unknown) at

http://mote.org/index.php?src=directory&view=magazine&srctype=display&id=519&category=All%20Art

icles





-5-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc









NOAA

Microscopic view of Karenia brevis

BCC/Red-tides-karenia_brevis









NOAA

Karenia brevis, a toxic dinoflagellate.



The toxins produced by Karenia brevis, called somewhat logically and perhaps

redundantly brevetoxin poisoning, is characterized by a combination of gastrointestinal

and neurologic symptoms. The cells of Karenia brevis produce a toxin that leaches into

the water and also vaporizes into the air. The toxin causes short-term respiratory

problems in humans when it vaporizes and also attacks the central nervous systems of

fish, birds and sea mammals. The toxin also kills sea life by direct poisoning, by clogging

gills, and by reducing the amount of dissolved oxygen (DO) in the water, in effect,

―suffocating‖ the fish.



The incubation period of brevetoxin in a marine animal or a human ranges from 15

minutes to 18 hours. Gastrointestinal symptoms include abdominal pain, vomiting, and

diarrhea. Neurologic symptoms include paresthesias, a skin sensation such as burning,

prickling, itching, or tingling, with no apparent physical cause; a reversal of hot and cold

temperature sensation; vertigo; and ataxia, a coordination problem that affects the fingers,

hands, arms, legs, body, speech, and eye movements.



Yet, you don’t have to eat contaminated fish or shellfish to become ill from Karenia

brevis. You just have the breath the air above the water. The airborne toxin irritates the

eyes, noses, throats, and lungs of beachgoers — a sensation sometimes called the ―red

tide tickle.‖ Breathing in the vapors of Karenia brevis results in general coughs; dyspnea,





-6-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





difficult or labored breathing or shortness of breath; and bronchospasms, a contraction of

the smooth muscle of the bronchi that results in an acute narrowing and obstruction of the

respiratory airway that causes coughs and wheezing.



Many people experience these symptoms when swimming in a bloom of Karenia brevis.

However, there have been reports of passengers on boats passing through a bloom of

Karenia brevis, as well as other toxic blooms, who have became so sick from breathing

the neurotoxic vapors that they had to be given emergency medical treatment.



Scientists are not sure what triggers the bloom and why it sometimes lasts more than nine

months, although pollution is suspected. There are, of course, many other dinoflagellates

that produce brevetoxin, including the Ptychodiscus brevis.



Spotting the killer phytoplankton – or not

There are few safeguards to avoid eating seafood contaminated by phytoplankton blooms

other than awareness, and not even that may help. Although state and the federal

governments closely monitor algal blooms by a variety of programs, local authorities

might not immediately distinguish between a toxic and non-toxic bloom until after the

local seafood is contaminated or someone gets sick. Unfortunately, some toxic blooms

are detected only after fish start to die or people become ill. Nor are there any outward

signs that seafood is contaminated. HABs don’t change the smell or flavor of seafood,

and cooking doesn’t kill the toxins.









-7-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc









An example of a red tide



In one dramatic example of this problem, six fishermen in 1990 almost died from

unwittingly eating steamed shellfish that had been contaminated by a toxic bloom. They

were on a commercial fishing trip well off the coastline on Georges Bank, 100 miles east

of Cape Cod, Maine. They picked up some clams in their fish nets and ate them for

dinner. Instantly, they were stricken by the toxin’s paralytic effect. The captain, who had

only sampled the meal, was able to call the Coast Guard, who rescued them. They all

survived the experience.



In New Jersey, the National Park Service and the state’s Division of Fish and Wildlife

have ―raided‖ bayside beaches at Sandy Hook, catching individuals who take clams from

the polluted waters. While no toxic tides have been reported in Raritan and Sandy Hook

Bays, there are enough pollutants in the waters to make people sick if they eat

contaminated shellfish. However, since the two bays routinely experience brown tides,

officials are concerned about the possibility some day of a toxic tide.



The best way to avoid contaminated seafood is to avoid local waters and only buy at

reputable seafood stores or supermarkets, and to dine out at established restaurants.

Hopefully, their suppliers are on guard against contaminated seafood, and are cooperating

with government agencies that monitor water quality and toxin levels. Most suppliers





-8-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





want to detect any problems at the wholesale level because if contaminated food reaches

consumers, the entire industry will suffer from lost sales.



Not all marine creatures are affected by toxic blooms tides. Many don’t absorb the toxins

as readily shellfish. Red tide does not pose a risk to people who eat lobsters or finned

fish, nor swimmers. Scallops also are not affected because people don't eat the part that

absorbs the poison. However, we prefer to emphasize caution on your part. Play it safe.

Don’t swim in waters experiencing plankton blooms (it’s yucky anyway), don’t take any

fish or shellfish where blooms occur, and never buy seafood off the back of someone’s

truck.



Algae blooms also occur in fresh water drinking supplies. Unfortunately, any toxins from

such a bloom can survive standard water purifying treatments. To solve this problem,

researchers at Florida International University in Miami are experimenting with using

640-kilohertz ultrasound waves that create micropressure zones as hot as 6,700° F

(3,700° C). This breaks some water molecules into reactive fragments that can kill algae.



Economic impact of red tides

According to NOAA,4 a preliminary and highly conservative nationwide estimate of the

average annual costs of HABs is approximately $50 million:

 Public health is the largest component, representing nearly $20 million annually

or about 42 percent of the nationwide average cost;

 Commercial fisheries lose on average $18 million annually;

 Recreation and tourism loses about $7 million, and

 Monitoring and management costs $2 million..



These numbers are low, due to a lack of information about the overall effect of many

HAB events and a difficulty in assigning a dollar cost to those events that we do

understand.



Some specific red tide events can be measured, especially when assessing the damages to

a specific industry. In June, 2005, a bloom extended from central Maine to south of Cape

Cod, closing shellfish beds that provided 35 percent of the nation’s clam harvest. Many

local restaurants, counting on clams for summertime tourists, had to import clams and

mussels from Canada and other areas of the U.S. State officials said the red tide cost the

shellfish industry about $3 million per week, but even then the total cost estimates ranged

from $12 to 24 million for Massachusetts alone, with additional losses in New Hampshire

and Maine.



Another example is the 1997 outbreak of fish kills in Maryland due to the dinoflagellate

Pfiesteria piscicida. The direct cost to watermen, boat charters, seafood dealers, and

seafood restaurants was at least $43 million dollars, based solely on the decline in

seafood sales. This estimate doesn’t factor in losses to tourism and recreational fisheries,



4

Science Education Resource Center (SERC), Carleton College, search for ―red tides‖ in the ―Microbial

Life section at http://serc.carleton.edu/index.html.





-9-

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





the costs of health care and emergency services, and the increased costs of monitoring

and analyzing HAB outbreaks. In addition, even though the waters subsequently were

declared safe, consumers for a long time were wary of buying local seafood, another cost

that was hard to estimate.



In Alaska, continual PSP blooms is one factor blamed for hampering the development of

a commercial, wild shellfish industry, which could be worth $6 million annually. In

Long Island Bay area of New York, huge blooms of the brown tide organism

Aureococcus anophagefferens – not a toxic phytoplankton but often a HAB --devastated

the bay scallop industry, estimated to be worth $2 million annually.



Nationally, some estimates have placed HABs costs in the U.S. alone at more than $1

billion in economic losses, due to closures of shellfish beds and coastal fisheries, reduced

tourism and other service industry revenues, and the treatment of public illnesses.



Worldwide? We haven’t a clue. One example of the potential economic losses is

Australia, which have been estimated between A$180 million and A$240 million per

year, the equivalent to about $150-200 million in U.S. 2002 dollars.



Life cycle of an algae bloom









5

The rapid growth of a phytoplankton.







5

Used with permission of the Delaware Department of Natural Resources, Tidewater Ecosystem

Assessment Division. Also see http://www.dnr.state.md.us/bay/hab/brown_tide.html .





- 10 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





Contaminated seafood a threat to humans

The most significant public health problems caused by harmful algae are:

 Neurotoxic shellfish poisoning (NSP) caused by Karenia brevis, which

we’ve noted produces the toxin brevetoxins.

 Amnesic shellfish poisoning (ASP) caused by Pseudo-nitzschia sp., which

produces the toxin domoic acid. This disease, which has been found along the

eastern Canadian coast, is caused by domoic acid-roducing planktonic and

benthic algae, including Pseudo-nitzschia pungens forma, Pseudo-nitzschia

multiseries and Amphora coffaeformis. It can also be found in soft shell clams

and blue mussels infected by Pseudo-nitzschia delicatissima. Gastric and

neurological symptoms include dizziness, disorientation and memory loss.

 Ciguatera fish poisoning (CFP) caused by Gambierdiscus toxicus,

Prorocentrum spp., Ostreopsis spp., Coolia monotis, cadinium kofoidii spp.,

and Amphidinium carterae, which produce the toxin ciguatoxin/maitotoxin;

 Diarrhetic shellfish poisoning (DSP) caused by Dinophysis sp., which

produces the toxin okadaic acid. DSP generally occurs in Japan and Europe,

but it has also been found in other countries such as Canada, the U.S., Chile,

New Zealand, and Thailand. Symptoms of DSP include diarrhea, nausea,

vomiting, abdominal pain, and cramps. DSP is generally not lethal.

 Paralytic shellfish poisoning (PSP) caused by Alexandrium spp.,

Gymnodinium catenatum, and Pyrodinium bahamensecaused, which produce

the toxon saxitoxins. PSP is common along the Atlantic and Pacific coasts in

the U.S. and Canada. Poisoning occurs when someone eats shellfish

contaminated with PSP toxins, which disrupts the nerve function and causes

paralysis. Extreme cases may result in death by asphyxiation by respiratory

paralysis.



Each of these syndromes is caused by different species of toxic algae, which occur in

various coastal waters of the United States and throughout the world. With the

increase in interstate and international transport of seafood, as well as international

travel by seafood consumers, virtually no human population is free of risk.









- 11 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc









This advanced, very high resolution radiometer (AVHRR) photo shows a blue filament of

Gulf Stream water (24-25°C) near Cape Lookout, North Carolina, that transported toxic

Karenia brevis cells from the Gulf Stream (deep blue), into the colder (yellow) coastal waters.



Since 1978, illnesses in the U.S. due to natural algae toxins have included PSP, NSP,

CFP, and ASP. Although records are incomplete because reporting to the Centers for

Disease Control (CDC) is voluntary, evidence indicates that CFP was responsible for

about half of all seafood intoxications. ASP appears to be on the increase and that

DSP may shortly make its debut in the United States, since the algae that causes them

occurs throughout the temperate coastal waters of the United States.



Is the HABs problem getting worse?

Most U.S. coastal waters are affected by toxic HABs. Native American stories from

the 1500s seem to describe red tide blooms, while Florida's first officially reported

bloom was in 1844. About a hundred years later, Woods Hole Oceanographic

Institution pinpointed the relationship between red tide and scratchy throats. The New

England states have recurring PSP problems. Fish kills in the Middle-Atlantic states

have recently been linked to a newly discovered organism called Pfiesteria. Florida

and other Gulf Coast states have fish kills and NSP from Gymnodinium brev. red

tides. The West Coast, including Alaska, has a continuing PSP problem and, recently,

domoic acid (ASP) problems have been discovered in the region. Even the tropics of

the Florida Keys, Hawaii, and Puerto Rico have reported CFP.









- 12 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc









Satellite image of plankton growth in the Pacific Ocean, as indicated by the presence of chlorophyll.

BCC/Red tides-Pacific map



Evidence suggests that HABs are increasing around the globe. Maps of the expansion

of HABs in the US since 1972 indicate the scale of the problem now as compared to

25 years ago. Some believe that humans may have contributed to spreading the

problem by transporting toxic species in ship ballast water, but this theory has yet to

be proven.



Is pollution the problem?

We know we have more known toxic algae species, more algae toxins, more affected

areas, more affected fisheries resources, and higher economic losses than we have

experienced in the past. Initially, everyone pointed to pollution or other human

activities as the causes. However, studies show many of the "new" or expanded HAB

problems in the U.S. occurred in waters where pollution was not an obvious factor. In

fact, the organisms responsible for HABs have been on Earth for a long time, so new

incidents may simply reflect increased awareness, better detection methods, and more

observers, rather than new species or an expanding problem.



In 2005, a massive red tide some 2,000-square miles in area occurred in the Gulf of

Mexico waters off the Florida coast, centering on St. Petersburg, which was devoid of

oxygen and marine life. What started in January with a fisherman's report of an algae

bloom off St. Petersburg spread south to Naples and up to Pensacola. The algae,

Karenia brevis, the toxic dinoflagellate locally known in the state as ―Florida red

tide,‖ is a naturally occurring algae in the Gulf that has appeared there since at least

the 1800's.



A 1987 NSP bloom originated in Florida and was carried by the Gulf Stream to North

Carolina waters -- a totally natural phenomenon with no proven links to human

causes. A massive 1972 red tide was responsible for introducing dormant cysts of the







- 13 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





PSP-producing species Alexandrium tamarense to southern New England waters,

where it has persisted to this day.









Woods Hole/USGS

Alexandrium tamarense



Those coastal waters have seen an increase in pollution over the years, but the actual

introduction and colonization of the species is believed to be the result of natural

currents and environmental forces, including a hurricane that occurred immediately

prior to the 1972 bloom. It may be that subsequent blooms of this species could be

aided by pollution, but this has not yet been proven.



The dinoflagellate Noctiluca scintillans sometimes blooms along the Texas coast,

turning the water a red-orange color. The species itself is nontoxic but can result in

localized fish kills by accumulating and emitting toxic levels of ammonia. Like some

other phytoplankton, it also is bioluminescent and can cause the water to glow

beautifully at night.









Texas Parks and Wildlife

The dinoflagellate Noctiluca scintillans.

BCC/Red-tides-Noctiluca-scintillans



Is aquaculture the problem?

Another suspected but unproven cause is the dramatic increase in aquaculture.

Increased monitoring of product quality and safety has revealed indigenous toxic

algae that probably were always there. Pollution may bear some responsibility,

however, as increased nutrients in our coastal waters stimulate "background"

populations of microscopic and macroscopic algae (seaweeds), as well as harmful or

toxic species. Some scientists argue that the nutrients we discharge into our coastal





- 14 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





waters are exceeding natural levels. Some algae species can adapt to the excessive

nutrients, including some HAB species. One example where nutrient discharges have

been linked to harmful blooms is with the ambush predator dinoflagellate Pfiesteria.

That organism and many closely related fish-killing species seem to thrive in polluted

waters.



Is the problem bigger than we thought?

One way to view the expanding HAB blooms in the U.S. is that we are getting better

at defining the extent of the problem.









NOAA plots phytoplankton growth and blooms using satellite surveillance as well as a cadre

of trained volunteers who report phytoplankton blooms.

BCC/Marine life-plankton map



The other side of the coin is that the problem is much larger than we previously

thought. HABs have always existed, and they may be expanding somewhat due to

pollution or other global changes, such as global warming and possible changes in

ocean currents. As we identify new toxins and new toxic species, we should better

understand the true nature and extent of the problem, whether the problem is

expanding, and how we could contain it. Whatever the causes, the national and global

HAB problem is serious. If it is growing due to human activities, we should be even

more concerned.



Maps showing the change in HAB events since 1972 are useful, but they give no

information about the frequency of the events. A single outbreak will look the same







- 15 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





as an annually recurrent bloom. A series of maps has been generated which depict the

frequency of specific HAB problems along the U.S. coast roughly from 1990 to 2000.

As these maps continue to be updated, they will create a time line of events that

should give us a better understanding of these algae blooms.









A snapshot of red tides or HAB-related occurrences in the U.S.6



Synopsis of this tutorial

There are about 85 phytoplankton or algae species that can create toxicity problems

when they over-produce or bloom in an area. They can kill marine wildlife and even

humans who consume tainted seafood. Also called harmful algae blooms (HABs) or

red tides, these population explosions are impossible to distinguish from non-toxic

brown tides. Most blooms are thought to be natural occurrences, but we can’t rule out

the possibility that human activity and pollution contribute to them. Tainted seafood

can only be detected by analysis by health officials, as there are no identifiable colors





6

Used with permission of the Delaware Department of Natural Resources, Tidewater Ecosystem

Assessment Division.





- 16 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





or smells. Cooking tainted seafood doesn’t kill the toxicity. Only buy seafood from

reputable establishments.



Care to take a quiz?

This quiz is designed as a review to reinforce what you’ve read. Try it, we won’t keep

score.



1. What causes a red tide or a brown tide?

 A discoloration of the water after heavy rains

 A marked increase of phytoplankton or algae

 A shift in tidal action that stirs up nutrients on the bottom of the bay

Answer: An increase in phytoplankton



2. How many species of algae exist?

 1,000 to 1,500

 2,700 or more

 3,600 or more

 4,400 or more

Answer: 4,400 or more



3. How many species of algae are toxic?

 10 to 15

 50 to 60

 80 to 85

Answer: 80 to 85



4. How would you best describe a ―red tide‖?

 A profuse concentration of algae that smother other plants and non-mobile marine

life

 A profuse concentration of algae whose toxicity is absorbed by marine life that

consume them

 A profuse concentration of algae that stain the water red

Answer: A profuse concentration of algae whose toxicity is absorbed by other marine

life that consume them



5. What is a HAB?

 A harbor auxiliary buoy

 A harmful algae bloom

 A nickname for a temporary fish tank

Answer: A harmful algae bloom



6. Are all phytoplankton blooms harmful?

 Yes

 No







- 17 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





Answer: No. All toxic red tides are described as harmful, but non-toxic brown tides

are categorized as harmful only of their blooms harm marine life by reducing

dissolved oxygen in the water, by blocking sunlight to marine plants, or by altering

the local habitat in any other way that would stress local marine life.



7. Are phytoplankton blooms caused by pollution?

 Yes

 No

 Maybe

Answer: The answer probably is ―No,‖ since blooms are natural events and many

blooms occur in areas that don’t have pollution problems. However, this doesn’t

preclude excessive nutrients from fertilizer runoff or sewage from adding to the

severity of some blooms. The jury is still out on this question.



8. Can we tell the difference between a red tide and a brown tide by the color of the

water?

 Yes

 No

Answer: No. The only way to determine if the algae are toxic is to identify the

specific algae.



9. Will cooking clams, shellfish or fish kill algae toxins?

 Yes

 No

 Maybe

Answer: No. Cooking won’t kill any toxins.



10. How can we avoid toxic seafood?

 If you see questionable discoloration in the water, call your municipal health

office

 Only buy sea food products from reputable, established merchants and

restaurants

 Avoid buying sea food off the back of someone’s truck

 If there have been toxicity scares in your area, order the chicken

Answer: All of the above.



Care to know more?

Have you read our tutorial on brown tides? You also might want to check our

tutorials on other marine issues and explanations.



Here are a couple of websites that you might want to visit (You will be leaving our

website when you click on these websites.)

 Everyone should read the Pew Ocean Commission’s nine-page Executive

Summary and its complete 166-page report, America's Living Oceans, on the

deplorable state of our less-than-healthy oceans.







- 18 -

7f5ad155-c47f-4593-9a0c-9a7927cca341.doc





 Woods Hole Oceanographic Institute (WHOI) has a harmful algae web page.

 The Public Health Fact Sheet by the Massachusetts Department of Public Health

has more information about red tides.









- 19 -