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ALGAE

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from

unicellular to multicellular forms. The largest and most complex marine forms are called

seaweeds. They arephotosynthetic, like plants, and "simple" because they lack the many distinct

organs found in land plants.

Algae lack the various structures that characterize land plants, such as phyllids and rhizoids innonvascular plants, or leaves,roots, and otherorgans that are found in tracheophytes. They are

distinguished fromprotozoa in that they are photosynthetic. Many arephotoautotrophic, although

some groups contain members that are mixotrophic, deriving energy both from photosynthesis

and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some

unicellularspecies rely entirely on external energy sources and have limited or no photosynthetic

apparatus.

All algae have photosynthetic machinery ultimately derived from the cyanobacteria, and so

produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as

purple and green sulfur bacteria.

Classification of algae: Algae are classified according to their rRNA sequences, structures,

pigments, and other qualities.

Eg. Hormosira banksii Corallina officinali Ulva spp. Thalassiosira sp. Karenia brevis Achyla

Colpomenia sinuosa Coralline Algae Codium fragile Phaeodactylum Protoceratium sp. Saprolegnia

Phyllospora comosa Caulerpa filiformis

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Chlamydomonas reinhardtii

Macroalgae and Microalgae

The large algae, or macroalgae, are the largest and most obvious forms of algae that we can easilysee.

However, there are the microalgae, and just hatched spores of all algae, that coat the floor of

many rockshore pools and surfaces. This forms one of the most important food sources for algae-

eating molluscs. We call these algae-eating animals herbivores.

Much microalgae also drifts around in the ocean currents as part of the plankton. This is a major

source of food for many oceanic and seashore animals and their juvenile planktonic stages.

Algae and symbioses

Some species of algae form symbiotic relationships with other organisms. In these symbioses, the

algae supply photosynthates (organic substances) to the host organism providing protection to the

algal cells. The host organism derives some or all of its energy requirements from the algae.

Examples include

lichens: a fungus is the host, usually with a green alga or a cyanobacterium as its

symbiont. Both fungal and algal species found in lichens are capable of livingindependently, although habitat requirements may be greatly different from those of the

lichen pair.

corals: Corals only live in shallow marine environments because they require clear,constantly moving water, oxic conditions, and sunlight. They are restricted to tropical

climates because the warm water facilitates the precipitation of their calcium carbonate

skeletons. These corals are called hermatypic corals, meaning that they incorporate a

symbiotic algae called zooxanthellae into their tissues. These algae live off of the carbondioxide in the water around the corals and release oxygen as a by-product, giving the

coral polyps one of the key ingredients they need for survival.

sponges: green algae live close to the surface of some sponges, for example, breadcrumbsponge (Halichondria panicea). The alga is thus protected from predators; the sponge is

provided with oxygen and sugars which can account for 50 to 80% of sponge growth in

some species.

Where algae live

Being aquatic, algae are

marine

freshwater

terrestrial

Terrestrial algae are effectively surviving in an aquatic environment on land. Soil algae survive in

a film of soil water.

The other major group of terrestrial algae are those in lichen symbioses.

http://en.wikipedia.org/wiki/Chlamydomonas_reinhardtiihttp://www.mesa.edu.au/friends/seashores/molluscs.htmlhttp://www.mesa.edu.au/friends/seashores/feeding.htmlhttp://www.mesa.edu.au/friends/seashores/glossary.html#planktonhttp://www.mesa.edu.au/friends/seashores/feeding.htmlhttp://www.mesa.edu.au/friends/seashores/feeding.htmlhttp://en.wikipedia.org/wiki/Symbiosishttp://en.wikipedia.org/wiki/Symbioseshttp://en.wikipedia.org/wiki/Lichenhttp://en.wikipedia.org/wiki/Coralhttp://en.wikipedia.org/wiki/Sea_spongehttp://en.wikipedia.org/wiki/Halichondria_paniceahttp://en.wikipedia.org/wiki/Chlamydomonas_reinhardtiihttp://www.mesa.edu.au/friends/seashores/molluscs.htmlhttp://www.mesa.edu.au/friends/seashores/feeding.htmlhttp://www.mesa.edu.au/friends/seashores/glossary.html#planktonhttp://www.mesa.edu.au/friends/seashores/feeding.htmlhttp://www.mesa.edu.au/friends/seashores/feeding.htmlhttp://en.wikipedia.org/wiki/Symbiosishttp://en.wikipedia.org/wiki/Symbioseshttp://en.wikipedia.org/wiki/Lichenhttp://en.wikipedia.org/wiki/Coralhttp://en.wikipedia.org/wiki/Sea_spongehttp://en.wikipedia.org/wiki/Halichondria_panicea

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Lichens comprise fungi and algae (or blue-greens) in partnership. The fungus provides an outer

weft of mycelia which creates a humid protected environment for the alga to live and

photosynthesise (and feed the fungus!).

Lichens are very good sensors of environmental pollution

On land, algae are often pioneer organisms, growing on bare rock (provided there is moisture).The rock weathers and crumbles, the algae die and the remains of both contribute to formation of

soil. This pioneering activity paves the way for more demanding plants to invade. A succession

such as this is precisely what would have occurred when the islands of the Caribbean first

emerged from the sea.

Within the aquatic environment, there are two broad niches;-

planktonic -floating algae.

For micro-algae these often have strange shapes which help keep them suspended and deter

predators.

benthic - attached algae. These are algae anchore to the substratum.

Life-cycle

Rhodophyta, Chlorophyta and Heterokontophyta, the three main algal Phyla, have life-cycles

which show tremendous variation with considerable complexity. In general there is an asexual

phase where the seaweed's cells are diploid, a sexual phase where the cells are haploid followed

by fusion of the male and female gametes. Asexual reproduction is advantageous in that it

permits efficient population increases, but less variation is possible. Sexual reproduction allows

more variation but is more costly because of the waste of gametes that fail to mate, among other

things. Often there is no strict alternation between the sporophyte and gametophyte phases andalso because there is often an asexual phase, which could include the fragmentation of the thallus.

A.Asexual Reproduction

For aquatic organisms such as algae, dispersal and desiccation stresses are at a minimum. The

major problem faced by algae is the transfer of gametes. Since the stable environment reduces the

requirements for variability and since gamete transfer could pose a difficulty, the algae rely

heavily on asexual reproduction. This, therefore, provides a means of increasing the number of

individuals while restricting the genetic variability. In fact, many algae never reproduce sexually.

Two methods of asexual reproduction utilized by algae will be examined. These are:

Daughter colony formation

Sporulation

i) Daughter Colony Formation

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A limited number of colonial algae produce miniature replicates of the colonies. These are termed

daughter colonies. These may be produced inside the hollow, spherical colonies or inside the

actual cells of the parent colony. Eventually, the parent colony will rupture and release the new

daughters. Examine the prepared slide ofVolvox sp. and note the daughter colonies.

Volvox sp. consists of many Chlamydomonas-like cells bound in a common spherical matrix.

Each cell in the sphere has two flagella extending outward from the surface of the colony.Synchronized beating of the flagella spin the colony through water like a globe on its axis.

Observe a demonstration of a live culture of Volvox sp. and note the characteristic movement of

the colonies.

ii) Sporulation

This is the most common form of asexual reproduction in the algae. Sporulation refers to the

process in which any cell of an organism produces one or more reproductive cells inside its cell

walls. The original cell is termed a sporangium and the new cells are termed spores. Spores are

often produced in large numbers for the rapid increase in population size. Examine the prepared

slide of Ulothrix sp. and locate developing zoospores (motile spores) located within

zoosporangia. These zoospores swim away from the parent, settle down and develop directly into

new filaments

Sporulation in Ulotrix sp.

B. Sexual Reproduction

Although most algae reproduce asexually, the proper environmental stimulus may initiate sexual

reproduction. The algae have evolved many variations in sexual reproduction such as different

types of gametes, different means of gamete transfer, and different locations of fertilization.

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The process of gamete formation is called gametogenesis. The relative form of the two fusing

gametes defines two categories of sexual reproduction -- isogamy and heterogamy.

Isogamy

Isogamy is the form of sexual reproduction in which the gametes produced are identical in shape,

size and motility. There is no structural distinction between "male" and "female" gametes. Pairs

of isogametes align themselves with their flagellar poles touching and after several seconds, the

motile gametes fuse to form a single, non-motile, diploid zygote.

Life cycle ofChlamydomonas sp.

Isogametes, less commonly, may be non-motile structures. A specific example exhibiting non-

motile isogametes is the reproductive process known as conjugation,which occurs in the

filamentous green alga, Spirogyra sp.

Isogamy inSpirogyra sp.

A. Resting filaments of alga cells.

B. Formation of conjugation tubes between two adjacent filaments.

C. Cytoplasmic contents of each cell form a compact mass, representing an

isogamete. The isogametes from one filament migrate through the conjugation

tubes into the adjacent filament.

The two isogametes unite to form a zygote. Each zygote eventually undergoesmeiosis to form four haploid cells. One haploid cell will form a new filament by

mitosis, the other three degenerate.

Heterogamy

In heterogamy, two different types of gametes are produced. The male gamete, the sperm cell, istypically very small, highly motile and is produced in very large numbers. The female gamete,

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the egg cell, is much larger and non-motile. Fewer female gametes are produced but each is

usually afforded some protection. Heterogametes are also produced by higher plants and animals.

Oedogonium sp. is a green alga that produces heterogametes. Locate a mature egg cell and thesmall male filaments, which are the site of sperm production. In the species you are examining,

the egg cells and male filaments are usually adjacent to one another on the same algal strand.

Heterogamy in Oedogonium sp.

Uses of algae

Seaweed is used as a fertilizer

Fertilizer

For centuries seaweed has been used as a fertilizer; Orwell writing in the 16th century referring to

drift weed in South Wales: "This kind of ore they often gather and lay in heaps where it heats androts, and will have a strong and loathsome smell; when being so rotten they cast it on the land, as

they do their muck, and thereof springeth good corn, especially barley" and "After spring tides or

great rigs of the sea, they fetch it in sacks on horse brackets, and carry the same three, four, or

five miles, and cast it on the lande, which doth very much better the ground for corn and grass".

Seaweed is a Multicellular Brown Alga (Laminaria)

Algae are used by humans in many ways. They are used as fertilizers, soil conditioners and are a

source of livestock feed. Because many species are aquatic and microscopic, they are cultured in

clear tanks or ponds and either harvested or used to treat effluents pumped through the ponds.Algaculture on a large scale is an important type ofaquaculture in some places.

Maerl is commonly used as a soil conditioner, it is dredged from the sea floor and crushed to

form a powder. It is still harvested around the coasts of Brittany in France and off Falmouth,

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Cornwall (also extensively in western Ireland) and is a popular fertilizer in these days of organic

gardening investigated Falmouth maerl and found that L. corallioides predominated down to 6 mandP. calcareum from 6-10 m.

Chemical analysis of maerl showed that it contained 32.1% CaCO3 and 3.1% MgCO3 (dry

weight).

Energy source

Algae can be used to makebiodiesel (see algaculture),bioethanol andbiobutanol and by

some estimates can produce vastly superior amounts ofvegetable oil, compared to

terrestrial crops grown for the same purpose.

Algae can be grown to producebiohydrogen. In 1939 a German researcher named Hans

Gaffron, while working at the University of Chicago, observed that the algae he was

studying,Chlamydomonas reinhardtii (a green-alga), would sometimes switch from the

production of oxygen to the production of hydrogen. Gaffron never discovered the causefor this change and for many years other scientists failed to repeat his findings. In the late

1990s professor Anastasios Melis, a researcher at the University of California at

Berkeley, discovered that if the algae culture medium is deprived of sulfur it will switch

from the production of oxygen (normal photosynthesis), to the production of hydrogen.

He found that the enzyme responsible for this reaction is hydrogenase, but that the

hydrogenase lost this function in the presence of oxygen. Melis found that depleting the

amount of sulfur available to the algae interrupted its internal oxygen flow, allowing the

hydrogenase an environment in which it can react, causing the algae to produce

hydrogen. Chlamydomonas moeweesi is also a good strain for the production of

hydrogen. Scientists at the U.S. Department of Energys Argonne National Laboratory

are currently trying to find a way to take the part of the hydrogenase enzyme that creates

the hydrogen gas and introduce it into the photosynthesis process. The result would be a

large amount of hydrogen gas, possibly on par with the amount of oxygen created.

Algae can be grown to produce biomass, which can be burned to produce heat and

electricity.

Algae can be used in oil production which could replace the petrol and other gas products

in the near future.

Pollution control

Algae are used in waste water treatment facilities, reducing the need for greater amounts

of toxic chemicals than are already used.

Algae can be used to capture fertilizers in runoff from farms. When subsequently

harvested, the enriched algae itself can be used as fertilizer.

Algae Bioreactors are used by some powerplants to reduce CO2emissions. The CO2 can

be pumped into a pond, or some kind of tank, on which the algae feed. Alternatively, the

bioreactor can be installed directly on top of a smokestack. This technology has been

pioneered by Massachusetts-based GreenFuelTechnologies.

Stabilizing substances

Chondrus crispus, (probably confused with Mastocarpus stellatus, common name: Irish moss), is

also used as "carrageen". The name carrageenan comes from the Irish Gaelic forChondruscrispus. It is an excellent stabiliser in milk products - it reacts with the milk protein caesin, other

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products include: petfoods, toothpaste, ice-creams and lotions etc. Alginates in creams and lotions

are absorbable through the skin.

Nutrition

There are four types of algae that are an excellent source of nutrition, Klamath Lake blue-green

algae, Spirulina, Chlorella and red marine algae.

Algae supplements provide the body with protein, carbohydrates, carotenoids, amino acids,

vitamins and trace minerals. It's especially beneficial for vegetarians or individuals suffering frommalnutrition.

Klamath Lake blue-green algae comes from the fresh-water Klamath Lake in Oregon and is a

rich source of vitamin B12 and all 22 amino acids.

Spirulina, another fresh-water blue-green algae, is about 65-71% protein and contains 8 essential

amino acids and an abundant amount of omega-3 alpha-linolenic acid.

Chlorella is close in comparison to spirulina; it has less protein, but contains twice as much

nucleic acid and chlorophyll.

Red marine algae is a rich source of vitamins, minerals, proteins, complex carbohydrates,

enzymes, essential fatty acids, fiber and trace elements.

Because Algae stimulates the immune system, increases white blood cell count and promotes thegrowth of healthy colonic flora, algae supplements are ideal for improving overall health. Algae

is also beneficial for treating anemia, infections, fatigue, obesity and toxicity.

Seaweeds are an important source of food, especially in Asia; They are excellent sources of many

vitamins including: A,B1,B2, B6, niacin and C. They are rich in iodine, potassium, iron,

magnesium and calcium.

Algae is commercially cultivated as a nutritional supplement. One of the most popular

microalgal species is Spirulina(Arthrospira platensis), which is a Cyanobacteria (known as blue-green algae), and has been hailed by some as a superfood. Other algal species cultivated for their

nutritional value include; Chlorella (a green algae), and Dunaliella (Dunaliella salina), which ishigh in beta-carotene and is used in vitamin C supplements.

Blue-green algae, known to scientists as Aphanizomenon flosaquae (AFA), is quickly becoming a

favorite form of nutrition for many. Why? Because its one of the most nutrient-dense dietarysupplements on the market. Here are some of the most common reasons people take the

supplement:

It is high in all eight essential amino acids and nutrients. It is a rich source of chlorophyll, which

helps cell regeneration and blood purification. It is high in beta-carotene. It is convenient for

people on the move. Whole green foods have just recently caught the attention of the media,

http://en.wikipedia.org/wiki/Thiaminehttp://en.wikipedia.org/wiki/Thiaminehttp://en.wikipedia.org/wiki/Thiaminehttp://en.wikipedia.org/wiki/Riboflavinhttp://en.wikipedia.org/wiki/Vitamin_B6http://en.wikipedia.org/wiki/Niacinhttp://en.wikipedia.org/wiki/Vitamin_Chttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/w/index.php?title=Microalgal&action=edit&redlink=1http://en.wikipedia.org/wiki/Spirulina_(dietary_supplement)http://en.wikipedia.org/wiki/Cyanobacteriahttp://en.wikipedia.org/wiki/Chlorellahttp://en.wikipedia.org/wiki/Dunaliellahttp://en.wikipedia.org/wiki/Beta-carotenehttp://en.wikipedia.org/wiki/Thiaminehttp://en.wikipedia.org/wiki/Riboflavinhttp://en.wikipedia.org/wiki/Vitamin_B6http://en.wikipedia.org/wiki/Niacinhttp://en.wikipedia.org/wiki/Vitamin_Chttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/w/index.php?title=Microalgal&action=edit&redlink=1http://en.wikipedia.org/wiki/Spirulina_(dietary_supplement)http://en.wikipedia.org/wiki/Cyanobacteriahttp://en.wikipedia.org/wiki/Chlorellahttp://en.wikipedia.org/wiki/Dunaliellahttp://en.wikipedia.org/wiki/Beta-carotene

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because they reportedly help many people increase mind-brain function. Others have found it

helps sustain energy levels throughout the day.

Newsweek recently reported that blue-green algae is one of the fastest growing items in

the exploding health food market. It is a perfect anabolic green food, containing all eightessential amino acids. For example, amino acids found in blue-green algae are of low

molecular weight, which means that the molecules are small enough to pass through the

blood-brain barrier, a feature of the nervous system that prevents bacteria, chemicals, andother harmful substances from entering the brain. Neuropeptides made from the amino

acids in blue-green algae pass easily through this filtering mechanism into the brain. As a

result, some of the first effects of blue-green algae reported by many people who take itare increased mental alertness, improved memory, and the ability to communicate more

clearly; for this reason, it is often called a "brain food."

In China at least 70 species of algae are eaten as is the Chinese "vegetable" known as fat choy(which is actually a cyanobacterium). Roughly 20 species of algae are used in everyday cooking

in Japan.

Certain species are edible; the best known, especially in Ireland is Palmaria palmata(Linnaeus)

O. Kuntze, also known as Rhodymenia palmata (Linnaeus) Kuntze, common name: dulse). Thisis a red alga which is dried and may be bought in the shops in Ireland. It is eaten raw, fresh or

dried, or cooked like spinach. Similarly, Durvillaea antarctica [4] is eaten in Chile, commonname: cochayuyo.

Porphyra (common name: purple laver), is also collected and used in a variety of ways (e.g."laver bread" in the British Isles). In Ireland it is collected and made into a jelly by stewing or

boiling. Preparation also involves frying with fat or converting to a pinkish jelly by heating the

fronds in a saucepan with a little water and beating with a fork. It is also collected and used by

people parts of Asia, specifically China, Korea (gim) and Japan (nori) and along most of the coast

from California to British Columbia. The Hawaiians and the Maoris ofNew Zealand also use it.

One particular use is in "instant" puddings, sauces and creams. Ulva lactuca (common name: sealettuce), is used locally in Scotland where it is added to soups or used in salads.Alaria esculenta(common name: badderlocks or dabberlocks), is used either fresh or cooked, in Greenland,Iceland,Scotland and Ireland.

The oil from some algae have high levels of unsaturated fatty acids. Arachidonic acid (a

polyunsaturated fatty acid), is very high inParietochloris incisa, (a green alga) where it reaches

up to 47% of the triglyceride pool .

Some varieties of algae are a vegetarian / vegan / plant based source of long chain essentialomega-3 fatty acids Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA) in adition to

vitamin B12. Fish oil contains the omega-3 fatty acids, but the original source is algae, which are

eaten by marine life such as copepods and passed up the food chain.

Other uses

There are also commercial uses of algae as agar.

http://en.wikipedia.org/wiki/Fat_choy_(vegetable)http://en.wikipedia.org/wiki/Cyanobacteriumhttp://en.wikipedia.org/wiki/Palmaria_palmatahttp://en.wikipedia.org/wiki/Palmaria_palmatahttp://en.wikipedia.org/wiki/Dulsehttp://en.wikipedia.org/wiki/Irelandhttp://www.algaebase.org/speciesdetail.lasso?species_id=11752&sk=0&from=results&-session=abv3:51909EC30802716127sVj3EDC9C7http://en.wikipedia.org/wiki/Porphyrahttp://en.wikipedia.org/wiki/Laver_(seaweed)http://en.wikipedia.org/wiki/Gim_(Korean_food)http://en.wikipedia.org/wiki/Norihttp://en.wikipedia.org/wiki/Californiahttp://en.wikipedia.org/wiki/British_Columbiahttp://en.wikipedia.org/wiki/New_Zealandhttp://en.wikipedia.org/wiki/Alaria_esculentahttp://en.wikipedia.org/wiki/Greenlandhttp://en.wikipedia.org/wiki/Icelandhttp://en.wikipedia.org/wiki/Scotlandhttp://en.wikipedia.org/wiki/Arachidonic_acidhttp://en.wikipedia.org/w/index.php?title=Parietochloris_incisa&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Parietochloris_incisa&action=edit&redlink=1http://en.wikipedia.org/wiki/Omega-3_fatty_acidhttp://en.wikipedia.org/wiki/Docosahexaenoic_acidhttp://en.wikipedia.org/wiki/Eicosapentaenoic_acidhttp://en.wikipedia.org/wiki/Vitamin_B12http://en.wikipedia.org/wiki/Copepodhttp://en.wikipedia.org/wiki/Fat_choy_(vegetable)http://en.wikipedia.org/wiki/Cyanobacteriumhttp://en.wikipedia.org/wiki/Palmaria_palmatahttp://en.wikipedia.org/wiki/Dulsehttp://en.wikipedia.org/wiki/Irelandhttp://www.algaebase.org/speciesdetail.lasso?species_id=11752&sk=0&from=results&-session=abv3:51909EC30802716127sVj3EDC9C7http://en.wikipedia.org/wiki/Porphyrahttp://en.wikipedia.org/wiki/Laver_(seaweed)http://en.wikipedia.org/wiki/Gim_(Korean_food)http://en.wikipedia.org/wiki/Norihttp://en.wikipedia.org/wiki/Californiahttp://en.wikipedia.org/wiki/British_Columbiahttp://en.wikipedia.org/wiki/New_Zealandhttp://en.wikipedia.org/wiki/Alaria_esculentahttp://en.wikipedia.org/wiki/Greenlandhttp://en.wikipedia.org/wiki/Icelandhttp://en.wikipedia.org/wiki/Scotlandhttp://en.wikipedia.org/wiki/Arachidonic_acidhttp://en.wikipedia.org/w/index.php?title=Parietochloris_incisa&action=edit&redlink=1http://en.wikipedia.org/wiki/Omega-3_fatty_acidhttp://en.wikipedia.org/wiki/Docosahexaenoic_acidhttp://en.wikipedia.org/wiki/Eicosapentaenoic_acidhttp://en.wikipedia.org/wiki/Vitamin_B12http://en.wikipedia.org/wiki/Copepod

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The natural pigments produced by algae can be used as an alternative to chemical dyes and

coloring agents. Many of the paper products used today are not recyclable because of the

chemical inks that they use, paper recyclers have found that inks made from algae are much

easier to break down. There is also much interest in the food industry into replacing the coloring

agents that are currently used with coloring derived from algal pigments. Algae can be used tomake pharmaceuticals. Sewage can be treated with algae as well. Some cosmetics can come from

microalgae as well. In Israel, a species of green algae is grown in water tanks, then exposed todirect sunlight and heat which causes it to become bright red in color. It is then harvested and

used as a natural pigment for foods such as Salmon.

Alginates

Between 100,000 and 170,000 wet tons ofMacrocystisare harvested annually in California foralginate extraction and abalone feed.

Red alga, Diatoms and Dinoflagellates are toxic for humans

Most red algae have delicately branched thalli and can live at greater ocean depths than other

algae. The red pigments enable red algae to absorb the blue light that penerates deepest into the

ocean. Gracilaria species, which grow in Pacific Ocean, are used by the humans for food.

However the member of this genus can produce a lethal toxin.

Diatoms, Dinoflagellates and water molds are grouped into the kingdom Chromista. Diatoms are

unicellular or filamentous algae with complex cell walls that consist of pectin and a layer ofsilica. They store energy captured through photosynthesis in the form of oil. Diatoms produced

domic acid, a toxic that cause diarrhea and memory loss. Since 1991, hundred of marine birds and

sea lions have died from the domoic acid intoxication in California.

Dinoflagellates are unicellular algae collectively called plankton or free floating organisms.

Some dinoflagellates produce neurotoxins. When fish swim through large number ofdinoflagellates Gymnodinium breve, the algae trapped in the gills of the fish release a neurotoxinthat stops the fish from breathing.

The large concentartion ofAlexandrium give the ocean a deep red color from which the red tidesoriginates. The term "red tide" (deep red colour) is also commonly used to describe harmful algal

blooms on the northern east coast of the United States, particularly in the Gulf of Maine. Seasonal

changes in nutrients, light, temperature cause fluctuations in algal populations- periodic increases

in numbers of planktonic algae are called algal bloom. This type of bloom is caused by anotherspecies of dinoflagellate known as Alexandrium fundyense. These blooms of organisms cause

severe disruptions in fisheries of these waters as the toxins in these organism cause filter-feeding

shellfish in affected waters to become poisonous for human consumption due to saxitoxin.

Saxitoxin cause paralytic shellfish poisoning.

In 1972 a red tide was caused in New England by a toxic dinoflagellate Alexandrium

(Gonyaulax) tamarense

In other areas, algal blooms are a seasonal occurrence resulting from coastal upwelling, a

natural result of the movement of certain ocean currents. The growth of marine phytoplankton is

generally limited by the availability of nitrates and phosphates, which can be abundant in

agricultural run-off as well as coastal upwelling zones. Coastal water pollution produced by

http://en.wikipedia.org/wiki/Pigmenthttp://en.wikipedia.org/wiki/Dyeshttp://en.wikipedia.org/wiki/Dyeshttp://en.wikipedia.org/wiki/Israelhttp://en.wikipedia.org/wiki/Macrocystishttp://en.wikipedia.org/wiki/Macrocystishttp://en.wikipedia.org/wiki/Macrocystishttp://en.wikipedia.org/wiki/Californiahttp://en.wikipedia.org/wiki/Dinoflagellatehttp://en.wikipedia.org/wiki/Alexandrium_fundyensehttp://en.wikipedia.org/wiki/Alexandrium_fundyensehttp://en.wikipedia.org/wiki/Fisheryhttp://en.wikipedia.org/wiki/Shellfishhttp://en.wikipedia.org/wiki/Saxitoxinhttp://en.wikipedia.org/wiki/Dinoflagellatehttp://en.wikipedia.org/wiki/Water_pollutionhttp://en.wikipedia.org/wiki/Pigmenthttp://en.wikipedia.org/wiki/Dyeshttp://en.wikipedia.org/wiki/Israelhttp://en.wikipedia.org/wiki/Macrocystishttp://en.wikipedia.org/wiki/Californiahttp://en.wikipedia.org/wiki/Dinoflagellatehttp://en.wikipedia.org/wiki/Alexandrium_fundyensehttp://en.wikipedia.org/wiki/Fisheryhttp://en.wikipedia.org/wiki/Shellfishhttp://en.wikipedia.org/wiki/Saxitoxinhttp://en.wikipedia.org/wiki/Dinoflagellatehttp://en.wikipedia.org/wiki/Water_pollution

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humans and systematic increase in sea water temperature have also been implicated as

contributing factors in red tides

http://en.wikipedia.org/wiki/Global_warminghttp://en.wikipedia.org/wiki/Global_warming