Seaweed. The benefits of brown algae Names of brown algae

03.11.2020

If you notice brown mucus on the walls of the aquarium, it's time to sound the alarm - harmful algae have started up in your pond. She leaves her marks both on the bottom and on the leaves aquatic plants... If you do not fight with brown algae, it will very quickly clog the reservoir, worsening the habitat for the fish.

What is brown algae

Brown algae- These are microscopic living organisms that can exist as single-celled and take the form of colonies. They are referred to as diatoms, which means "halved".

This is their structure: 2 halves of a single whole - epithecus (upper) and hypothesis (lower). All this is exposed in a single solid shell. Through its porous walls, the metabolism of brown algae takes place.

Like any protozoan, brown algae reproduces by division. When dividing, the daughter cell gets a piece of the mother's shell. And these halves of the shell are able to recreate themselves, donning both "mother" and "daughter" in new armor.

Since the shells are impregnated with silica, they are not able to grow in size. Because of this, each subsequent generation of diatoms is smaller than their ancestors. But they also manage to leave brown deposits on any surface of the aquarium.

Among these algae there are individuals that gather in tubular colonies in the form of brown bushes. They grow very quickly, sometimes reaching 20 cm in height. But to a greater extent, they look like flat formations, which we perceive as plaque.

Brown algae prefer shaded corners of water bodies with an abundance of organic matter. This is exactly what stimulates them to actively develop. Filling the entire aquarium, this algae deprives other inhabitants of the right to a normal existence.

Reasons for the appearance of diatoms

If the reservoir is new, then the appearance of brown blotches on the walls of the aquarium or the surface of the water after a couple of weeks is considered the norm. The reason is the still uninhabited habitat - a fairly high content of carbon and organic matter in the water. Apparently, in the reservoir there are still a small number of fish and green vegetation that would absorb all this abundance.

But if the "brown junta" began to seize the space of the old aquarium, then here you should already think about where the regime was violated.

Perhaps the aquarium is not sufficiently lit - the "drillers" are very fond of partial shade.
Increased iodine content is also the cause of the appearance of brown algae.
Brown algae are also fed from silicates contained in the reservoir. Their source can be substrates containing silicon, or sand at the bottom of the reservoir.

But whatever of the reasons affecting the appearance of brown algae, it is necessary to start the fight against it immediately, as soon as the first signs of the problem are noticed.

Means of combating brown algae

To make the inhabitants of your home pond feel comfortable enough, get rid of brown algae with all available means. Don't let these "amoeba" grow in your tank.

In a young aquarium, it will be enough to do mechanical work, removing all plaque from the surfaces. To do this, you can purchase a special scraper or take a regular blade.
Brown deposits will have to be cleaned off the leaves of aquatic plants simply by hand. Never use foam or sponge to remove algae. And do your cleaning carefully so as not to damage the plants.
Do not forget about the accumulating dirt at the bottom of the reservoir - it is better to remove it with the help of the hoses intended for this.
Remove pebbles, shells, pebbles (when changing water) from the aquarium and rinse them well. Do the same with decorative elements (artificial locks, decorative snags, etc.).
Rinse should also be done under running water and filter, as well as compressor hoses.
Get a "biological weapon" in the aquarium - fish that feed on brown algae: girinoheilus, ancistrus catfish, Siamese algae eater, etc. Molluscs (neritic olive snail, horned snail) are also good cleaners.

But you should not use various chemicals to combat brown "evil spirits" - harm other inhabitants of the reservoir. However, some antibiotics (such as penicillin) can be used. And be sure to place the aquarium as close to the light as possible.

Preventive measures

So that you do not have to face such a scourge as brown algae anymore, follow the basic rules for caring for home waters.

First of all, provide adequate lighting for every corner of the aquarium. If the daylight hours are too short, use additional lighting fixtures. It is better to use lamps that give red spectral light.
Always keep the temperature in the reservoir at the optimal level (+ 22-28 0 С) - brown algae love just the opposite, cooler.
Change the water in the aquarium regularly, monitor its technical parameters (pH, iodine, nitrates, phosphates, silicates). Never use water directly from the tap - you only need purified water.
Install filters in the pond that can absorb silicates
Plant the aquarium with a large number of aquatic plants - they "take away" part of the food from the brown algae, thereby slowing down its growth.
Experienced aquarists recommend putting zinc and copper products on the bottom of the pond. These metals are capable of destroying brown algae.

Each time you change the water or clean the aquarium from brown algae, provide the inhabitants of the reservoir with round-the-clock lighting for several days.

How to get rid of brown algae:

Brown algae are common in the seas and oceans of the whole world, they live mainly in coastal shallow waters, but also far from the coast, for example, in the Sargasso Sea. They are an important component of benthos.
The brown color of the thallus is due to a mixture of different pigments: chlorophyll, carotenoids, fucoxanthin. A set of pigments enables photosynthetic processes, since chlorophyll does not capture those wavelengths of light that penetrate to depth.
In low-organized filamentous brown algae the thallus consists of one row of cells, while in highly organized cells they not only divide in different planes, but partially differentiate, as if forming "petioles", "leaves" and rhizoids, with the help of which the plant is fixed in the substrate.
The cells of brown algae are mononuclear, chromatophores are granular, numerous. Spare products are contained in them in the form of polysaccharide and oil. Pectin-cellulose walls are easily slicked, apical or intercalary growth.
Asexual reproduction (absent only in fucus) is provided by numerous biflagellated zoospores formed in unicellular, less often multicellular zoosporangia.
Asexual vegetative reproduction is carried out by parts of the thallus.
The forms of the sexual process: isogamy, heterogamy and oogamy.
All brown algae, except for fucus algae, have a pronounced change in developmental phases. Reduction division occurs in zoosporangia or sporangia, they give rise to a haploid gametophyte, which is bisexual or dioecious. A zygote without a dormant period grows into a diploid sporophyte. In some species, the sporophyte and gametophyte do not differ externally, while in others (for example, in kelp) the sporophyte is more powerful and more durable. In fucus, a reduction of the gametophyte is observed, since the gametes merge outside the mother plant, in the water. A zygote without a dormant period develops into a diploid sporophyte.

Among brown algae, there are both microscopic and macroalgae. The latter can reach gigantic sizes: for example, algae macrocystis can reach 30-50 m in length. This plant grows very quickly, giving a large amount of extracted biomass, per day the algae thallus grows by 0.5 meters. In the course of evolution, sieve tubes similar to those found in vascular plants appeared in the thallus of macrocystis. Of the types of macrocystis, a special group of substances is extracted - alginates - mucous intercellular substances. They are widely used as thickening agents or colloid stabilizers in the food, textile, cosmetics, pharmaceutical, pulp and paper industries, as well as in welding. Macrocystis can produce several harvests per year. Attempts are now being made to cultivate it on an industrial scale. In the thickets of macrocystis, hundreds of animal species find protection, food, and breeding grounds. C. Darwin compared its thickets with land rainforest: "If in any country to destroy forests, I do not think that this would kill approximately the same number of animal species as with the destruction of thickets of this algae."

Fucus Is a dichotomously branching brown alga with air bubbles at the ends of the plates. Thallus reach 0.5-1.2 m in length and 1-5 cm in width. These algae densely cover many of the rocky areas exposed at low tide. When the algae is flooded with water, air-filled bubbles carry them out into the light. The rate of photosynthesis in seaweed often exposed to air can be seven times faster in air environment than in water. Therefore, algae occupy the coastal zone. Fucus does not have an alternation of generations, but only a change in nuclear phases: the whole alga is diploid, only gametes are haploid. Reproduction by spores is absent.

Two species of the genus sargassum, which do not reproduce sexually, form huge, free-floating masses in the Atlantic Ocean, this place is called the Sargasso Sea. Sargassums swim, forming continuous thickets at the surface of the water. These thickets stretch for many kilometers. Plants are kept afloat by air bubbles in the thallus.

Laminaria ("kombu") in China and Japan are regularly used as vegetables; they are sometimes bred, but mainly taken from natural populations. The greatest economic importance is seaweed (kelp), it is prescribed for sclerosis, a violation of the thyroid gland, as a mild laxative. Previously, it was burned, the ash was washed, the solution was evaporated, in this way soda was obtained. The soda was used to make soap and glass. At the beginning of the 19th century, 100 thousand tons of dry algae were burned in Scotland per year. Since 1811, thanks to the French industrialist Bernard Courtois, iodine was obtained from kelp. In 1916, 300 tons of iodine were extracted from seaweed in Japan. Kelp is a large brown alga with a length of 0.5-6 m, consists of leaf-like plates, a stem (trunk) and a structure for attachment to the substrate (rhizoids). The meristem zone is located between the plate and the leg, which is very important for industrial use... When the fishermen cut off the regrown plates of this alga, its remaining deeper parts are regenerated. The trunk and rhizoids are perennial, and the plate changes annually. This structure is typical for a mature sporophyte. On the plate, unilocular zoosporangia are formed, in which mobile zoospores mature and grow into gametophytes. They are represented by microscopic filamentous growths consisting of several cells that carry the genitals. Thus, kelp has a heteromorphic cycle with a mandatory alternation of generations.

Department of Red Algae. general characteristics

Red algae are common in the seas of tropical and subtropical countries and partly in the area temperate climate(the coast of the Black Sea and the coast of Norway). Some species are found in fresh waters and on the ground.
The structure of the thallus of red algae is similar to the structure of the thalli of the most highly organized brown algae. Thallus has the form of bushes, composed of multicellular branching filaments, less often lamellar or leaf-shaped, up to 2 m in length.
Their color is due to such pigments as chlorophyll, phycoerythrin, phycocyan. They live in deeper waters than brown ones and require additional pigments to capture light. Due to the presence of phycoerythrin and phycocyanin, they got their name - red algae.
Chromatophores in red algae have the form of discs; there are no pyrenoids. Spare products are contained in them in the form of oil and red algae-specific purple starch, which turns red from iodine. In some species, the pectin-cellulose cell walls become mucous so much that the entire thallus acquires a slimy consistency. Therefore, some types are used to obtain agar-agar, which is widely used in the food industry for the preparation of nutrient media for the cultivation of bacteria and fungi. The cell walls of some red algae can be encrusted with calcium carbonate and magnesium carbonate, which gives them the hardness of a stone. Such algae are involved in the formation of coral reefs.
Red algae have no mobile stages in the development cycle. They are characterized by a very special structure of the organs of sexual reproduction and the form of the sexual process. Most scarlet plants are dioecious plants. Mature sperm (one immobile gamete) emerge from the antheridia into the aquatic environment and are carried by currents of water to the carpogon (female organ of sexual reproduction). The contents of the sperm penetrate into the abdomen of the carpogon and merge there with the ovum. The zygote without a dormant period divides by mitosis and grows into filamentous thalli of different lengths. Thallus is diploid. In the upper part of these filaments, sexual reproduction spores (carpospores) are formed. With asexual reproduction on the thallus, sporangia are formed, which contain one spore each - a monospore, or four each - tetraspores. Before the formation of a tetraspor, a reduction division occurs. In monosporous algae, gametangia and sporangia are formed on the same monoploid plant; only the zygote is diploid. For tetrasporous, alternation of developmental phases is characteristic: haploid tetraspores grow into a haploid gametophyte with gametangia; Diploid carpospores grow into diploid plants with sporangia (diploid sporophyte). Gametophyte and sporophyte are indistinguishable in appearance. In porphyry and porphyridium, asexual reproduction is carried out by monoploid monospores. They go through the entire developmental cycle in a haploid state; only the zygote is diploid in them (as in many algae).

The red porphyry algae feeds many people in the North Pacific and has been cultivated for centuries in Japan and China. More than 30,000 people are employed in the production of this type in Japan alone, and the resulting production is estimated at about $ 20 million annually. Salads, seasonings, soups are made from it. Eaten dried or candied. The famous dish is "nori" - rice or fish wrapped in dried seaweed. In Norway, at low tide, sheep are released on the coastal area, rich in red algae, like in a pasture. This is one of the typical representatives of purple. The leafy purple thallus of this genus is attached to the substrate with its base and reaches 0.5 m in length.

Lives in the Black Sea. Half of the agar obtained in Russia is made from this crimson.

Distribution of algae in water and on land. The value of algae in nature and economy.

Most real algae live in freshwater bodies and seas. However, there are ecological groups of terrestrial, soil algae, snow and ice algae. Algae living in water are divided into two large ecological groups: planktonic and benthic. Plankton is a collection of small, mainly microscopic organisms freely floating in the water column. The plant part of the plankton, formed by real algae, and some crimson, is phytoplankton. The importance of phytoplankton for all inhabitants of water bodies is enormous, since plankton produces the bulk of organic matter, due to which, directly or indirectly (through the food chain), the rest of the living world of water exists. Diatoms play an important role in the formation of phytoplankton.

Benthic algae include macroscopic organisms attached to the bottom of water bodies or to objects and living organisms in the water. The majority of benthic algae live at depths of up to 30–50 m. Only a few species, which are mainly crimson, reach depths of 200 m or more. Benthic algae is an important food for freshwater and saltwater fish.

Terrestrial algae are also quite abundant, but usually not seen due to their microscopic small size. However, greening of the sidewalks, powdery green deposits on the trunks of thick trees indicate accumulations of soil algae. These organisms are found in most soils climatic zones... Many of them contribute to the accumulation of organic matter in soils.

Algae of ice and snow are microscopically small and are found only when a large number of individuals accumulate. The phenomenon of the so-called "red snow" has gained the greatest popularity for a long time. The main organism causing snow reddening is one of the types of unicellular algae - snow chlamydomonas. Except free-living algae important role in nature, algae play - symbionts, which are the photosynthesizing part of lichens.

Due to its wide distribution, algae have great importance in the life of individual biocenoses and in the cycle of substances in nature. The geochemical role of algae is primarily associated with the calcium and silicon cycle. Making up the bulk of the plant and aquatic environment and participating in photosynthesis, they serve as one of the main sources of organic matter in water bodies. In the World Ocean, algae annually create about 550 billion tons (about ¼) of all organic matter on the planet. Their yield here is estimated at 1.3 - 2.0 tons of dry matter per 1 g of water surface per year. Their role is enormous in the nutrition of aquatic organisms, especially fish, as well as in the enrichment of the Earth's hydrosphere and atmosphere with oxygen.

Some algae, together with heterotrophic organisms, carry out the processes of natural self-purification of waste and polluted waters. They are especially useful in open "oxidation ponds" used in tropical and sub tropical countries... Open ponds with a depth of 1 to 1.5 m are filled with untreated sewage. During photosynthesis, algae release oxygen and provide the vital activity of other aerobic microorganisms. Many of the algae are indicators of pollution and salinization of habitats. Soil algae are actively involved in soil formation.

The economic value of algae lies in their direct use as food products or as a raw material for obtaining various substances valuable to humans. For this purpose, especially those types are used, the ash of which is rich in sodium and potassium salts. Some brown algae are used as fertilizers and for feeding pets. Algae are not very nutritious because a person does not have enzymes that allow you to break down and digest substances of cell walls, but they are rich in vitamins, iodine and bromine salts, trace elements.

Seaweed is a raw material for some industries. The most important products derived from them are agar-agar, algin and carrageenan. Agar - a polysaccharide that is obtained from red algae. It forms gels and is widely used in food, paper, pharmaceutical, textile and other industries. Agar is indispensable in microbiological practice in the cultivation of microorganisms. Capsules for vitamins and medicines are made from it, used to obtain dental prints, in cosmetics. In addition, it is introduced into the composition of bakery products so that they do not stale, in the formulations of fast-solidifying jellies and confectionery products, and also used as a temporary shell for meat and fish in tropical countries. Agar is obtained from anfelcia, mined in the White and Far Eastern seas. Algin and alginates extracted from brown algae (kelp, macrocystis) have excellent adhesive properties, are non-toxic, and form gels. They are added to food products, to tablets in the manufacture of medicines, used in leather dressing, in the production of paper and fabrics. Soluble threads used in surgery are also made from alginates. Carrageen looks like agar. Agar is preferred for stabilizing emulsions, cosmetics and dairy products. The possibilities for the practical use of algae are far from being exhausted.

Under certain conditions, algae "bloom", ie. accumulate in large quantities in water. "Blooming" is observed when there is enough warm weather when the water is observed eutrophication , i.e. a lot of nutrients ( industrial effluents, fertilizers from the fields). As a result, an explosive multiplication of the primary producers, algae, begins, and they begin to die off before they can be eaten. In turn, this causes an intensive multiplication of aerobic bacteria, and the water is completely deprived of oxygen. Fish and other animals and plants perish. Toxins formed during water bloom increase the death of animals, they can accumulate in the body of mollusks and crustaceans that feed on algae, and then, getting into the human body, cause poisoning and paralysis in him.

Algae (lat.Algae) is a group of plants united by the following characteristics:

Scientific classification of algae

Class: Brown algae (Phaeophyceae)
Order: Laminariales
Family: Laminarium
Genus: Laminaria (Laminariaceae)
Species: Sugar kelp (Laminaria saccharina)
Species: Fucus vesiculosus.

Brown algae are complex multicellular plants.
Distributed widely in the coastal zone of the seas of the Arctic Ocean, as well as in the Far East (in the coastal zone of the Pacific Ocean), the most useful in terms of the content of trace elements and vitamins, grow in the littoral zone (in the zone of high and low tide), as well as at great depths up to 200 meters.
Only eight species of brown algae have been assimilated in fresh water bodies.

Brown algae include 1500 species, which are combined into 265 genera, of which are known and used by humans:

In brown algae, the size of the thallus (thallus - trunk) ranges from 1 micron to several tens of meters (up to 40 m, for example, in Macrocystis, Nereocystis).
The shape of the thallus is varied: creeping or vertically standing threads, crusts, plates, bags, bushes.
Attachment of the thallus is carried out using the rhizoids or the sole.
To keep in an upright position in a number of brown algae, in the structure of the thallus, air bubbles filled with gas are formed.

Some brown algae: wakame, sugary kelp or seaweed, fucus are eaten.

Brown seaweed is a source of vital nutrients, vitamins, macro- and microelements.
Brown algae are many times superior to terrestrial plants in terms of the content of vitamins and microelements, and a number of biologically active substances are found only in algae:

The healing qualities of marine plants

According to scientists, incl. Dr. A.M. Titov:
for full healthy functioning, each person needs 90 vital substances (food additives), which are not formed in the human body and must be supplied with food.
This is about 60 minerals,
16 vitamins,
12 essential amino acids and proteins and
3 fatty acids.
In the absence or insufficiency of these vital substances, diseases associated with the deficiency of these substances develop.
(A.M. Titov, physician,
Corresponding Member of the International Academy of Sciences of Ecology, Human Safety and Nature).

Brown algae contain a complete balanced composition for most (70) elements of the periodic table,

The chemical composition of algae
has a similarity to the composition of human blood

The advantage of sea plants (seaweed, fucus) over synthetic vitamin and mineral complexes:
in brown algae, microelements, vitamins, polysaccharides necessary for humans are in the form of organic compounds.
This allows the human body to choose the substances it needs, which are currently lacking, after which there is a very effective assimilation of these necessary substances.
The substances present in the human body in the quantities it needs will not be absorbed by the body, but removed, excluding the possibility of an overdose.

Ecological group and habitat

The department of brown algae (Phaeophyta) has about 1500 species.

Brown algae live almost only in the seas(only a few species are found in fresh water bodies). Habitat depth is relatively shallow, for most species - 5-15 m, but some species are common to a depth of 40-100 m and even 200 m. Brown algae are included in ecological group of benthic(bottom) organisms.

The structure of brown algae

The precursors of chloroplasts of brown algae are bacteria close to Heliobacterium chlorum. The main photosynthetic pigment is chlorophyll a, the auxiliary ones are carotenoids, including brown fucoxanthin and yellow xanthophylls. The auxiliary pigments of brown algae expand the spectrum of light absorbed by them in the blue-green area.

Spare substance - starch-like soluble carbohydrate kelp.

Thallus (thallus) is only multicellular. Large, sometimes many-meter thalli of brown algae are kept afloat due to air bubbles located in the thallus. In many representatives of brown algae, tissue differentiation has been outlined. Inside the thallus pass vascular bundles that resemble the phloem of higher plants. The emergence of the vascular system is associated with the need to transport nutrients to the many-meter thallus - from the upper, photosynthetic, parts of the plant to the lower ones, in which conditions for photosynthesis are worse.

Rice. The structure of brown algae

Reproduction

In brown algae, the weight of the form of sexual reproduction is isogamy, heterogamy, and oogamy. There is an alternation of generations, usually heteromorphic. Asexual reproduction - zoospores and pieces of thallus (vegetative reproduction).

The value of brown algae

Brown algae form whole "underwater forests" at a relatively shallow depth, surrounding a solid wall of the coasts of all seas and oceans of both hemispheres. These "underwater forests" provide food, shelter and breeding grounds for a huge number of marine life, including many commercial fish. After dying off, algae form detritus, which is food for planktonic organisms.

Brown algae are ubiquitous, but the largest species are found in the seas of temperate and northern latitudes.

Rice. 1. Brown algae: a) macrocystis (Macrocystus); c) sargassum (Sargassum); c) fucus (Fucus); d) kelp (Laminaria)

Typical representatives of the department

Brown algae are widespread in the Far Eastern seas kelp (seaweed), the length of the thallus is 5-6 m. Seaweed is used as food by the peoples of Southeast Asia.

Giant brown algae found on the Pacific coast of South America macrocystis. Its huge thallus reaches a length of 50-60 m. It is interesting that it grows in just one season.

On the littoral (part of the bottom exposed at low tide) of the northern seas, it forms extensive thickets fucus(thallus length up to 2 m).

The South Atlantic (Sargasso Sea) is characterized by huge accumulations of brown algae sargassum. Sargasso means grape in Spanish, and indeed the clusters of air bubbles that keep the thallus of these algae afloat are reminiscent of bunches of grapes. Sargassum species found in the Sargasso Sea are the only brown algae that float on the surface of the water, rather than being attached to the bottom.

Economic value

The cells of brown algae are covered over the cellulose shell with a layer of a special carbohydrate - pectin, which consists of alginic acid or its salts (alginates). When mixed with water (in a ratio of 1: 300), alginates form a viscous solution.

Alginates are used extremely widely:

in the food industry (when receiving marmalades, juices, marshmallows, etc.);
in perfumery (making creams, pastes, gels, etc.);
in medicine and pharmaceutical industry (in the manufacture of ointments, pastes, soluble surgical threads);
in the chemical industry (in the production of varnishes, paints, adhesives that do not lose their qualities during freezing and thawing; plastics, plasticizers, synthetic fibers);
in book printing (to improve print quality);
alginates make natural fabrics colorless and waterproof, they are used to improve the quality of molding earth in foundry, for the manufacture of electrodes (increasing the quality of welds) and in many other sectors of the national economy.

Hexatomic alcohol is obtained from brown algae mannitol, used as a blood substitute, as a medicine in the treatment of diabetes, as well as in the light and chemical industries (in the production of paper, varnishes, paints, explosives and for the manufacture of leather).

Brown seaweed kelp (seaweed) is used for food.

Brown algae is used and how medicine: as a mild laxative, in the treatment of vascular diseases, as well as a source of iodine and trace elements in diseases of the thyroid gland. Iodine it was first obtained from brown algae, and in the past they were the main raw material for its production. Currently, the scale of this production has sharply decreased due to the emergence of more cost-effective sources of iodine production.

Brown algae can be used as indicators of gold deposits, because they are able to accumulate it in the cells of the thallus.

Brown algae are also used in agriculture - as fertilizers and for livestock feed.

Brown algae, with a few exceptions, are marine organisms predominantly of the cold waters of the Northern and Southern Hemispheres. About 1500 species are known belonging to 240 genera. A common external feature of brown algae is a yellowish-brown color of thalli, due to the presence in their cells of a large number of yellow and brown pigments - carotenoids. Brown algae are predominantly very large, complexly dissected organisms attached to the substrate. In more primitive forms, thalli are microscopic, in more advanced ones, which include most brown algae, thalli are macroscopic, often of a complex morphological and anatomical structure, sometimes reaching lengths of up to 60 m or more.

The shape of the thalli is extremely diverse and is presented in the form of threads, crusts, bubbles, plates, bushes, etc. In primitive organisms of the order of ectocarpal ( Ectocagrales) thallus often looks like bushes formed by abundantly branching single-row filaments. A number of representatives of brown algae are distinguished by uniaxial and multi-axial thallus. In the first case, one thread extends upward from the attachment organs with lateral ones growing from it. In multi-axial forms, a bundle of single-row filaments grows from the base with lateral filaments growing from them. As a result of dense interlacing and accretion of threads of uniaxial and multiaxial forms, it is often formed by a thallus of a pseudo-tissue type.

Highly organized brown algae have complexly dissected thalli with stem, leaf, and tapered parts that resemble flowering plants. Such and similar forms are attributed to the parenchymal type of body structure. The parenchymal structure of the thallus can differ in relative complexity and consist of the upper dividing layer of the cortex - the meristoderm, the inner layer of the cortex, the intermediate layer and the core with sieve tubes and tubular filaments.

All brown algae attach to soil and other hard substrates by rhizoids or basal discs. Thallus of brown algae can be ephemeral, one - and perennial. In perennial forms, either only shoots with reproductive organs, or the entire lamellar part of the thallus, or only the organs of attachment - the basal discs - can be perennial.

The cells of brown algae are varied in shape and size. The cell wall consists of an inner cellulose (algulose) layer and an outer pectin layer. The pectin layer is usually formed by protein compounds of alginic acid and its salts. Due to this structure, the cell membrane can swell strongly and turn into a mucous mass.

The cells are mononuclear. Chromatophores are usually granular or disc-shaped, mostly numerous, less often ribbon-like or lamellar. In addition to their own membrane, chromatophores are clothed with a complex system of membranes that are in direct connection with the membrane of the nucleus, that is, the cell has a "chloroplast endoplasmic reticulum." In the chromatophore matrix, three-thylakoid lamellae are located in parallel, surrounded on the periphery by one or more encircling lamellae. In chromatophores, in addition to chlorophylls but and with, large amounts of β- and ε-carotenes, as well as a number of xanthophylls (fucoxanthin, violaxanthin, antheraxanthin, etc.). Different ratios of these pigments determine the color of the thallus of brown algae from olive-yellowish to dark brown.

Pyrenoids in forms that have them protrude from the chromatophore in the form of a kidney. The genophore is annular, located under the peripheral lamellae. The products of assimilation are carbohydrates: laminarin (polysaccharide), mannitol (hexahydric alcohol), oil.

Monad cells in brown algae are zoospores and gametes. They usually have two flagella, heterocont and heteromorphic. On the membrane of the anterior, usually longer, flagellum, mastigonemes are located, consisting of a thickened basal part, a microtubular main part, and one to three terminal filaments. The posterior, usually shorter, smooth flagellum has a swelling at the base opposite the stigma. Each flagellum of ectocarpus gametes carries a long, often spirally twisted terminal appendage - an acroneme. Dictyotic spermatozoa have only one anterior flagellum.

Reproduction in brown algae is vegetative, asexual and sexual.

Vegetative reproduction is carried out by randomly torn off sections of the thallus, in a few forms - by specialized branches - "brood buds", which are easily broken off from the parent thallus and, fixed in the ground, form new thalli.

Asexual reproduction in most brown algae occurs by zoospores, which are formed in several, usually in unilocular or unicameral sporangia - spherical or ellipsoidal cells. Sporangia are formed on diploid thalli - sporophytes. The formation of biflagellate zoospores is usually preceded by meiosis. Representatives of the dictyote order ( Dictyotales) in unilocular tetrasprangia after reduction fission of the nucleus, four immobile spores are formed - tetraspores.

Haploid zoospores and tetraspores germinate with haploid gametophytes, on which gametangia develop. More primitive brown algae have an isogamous reproductive process. Isogametes develop in multi-celled, or multi-chambered, sporangia, consisting of numerous cubic cells. In each such cell, one gamete is formed.

A number of brown algae have a heterogamous sexual process. Gametangia are multi-chambered. However, some consist of a large number of small cells that produce biflagellated microgametes; others are made up of a smaller number of larger cells, which form along the biflagellated macrogamete.

The most highly organized brown algae have an oogamous sexual process. In oogonia and antheridia, usually one egg and one sperm cell develops. However, representatives of the order of Fucus ( Fucales) in oogonia, two, four or eight eggs are formed, and in antheridia - 64 spermatozoa each. In each chamber, dictyote antheridia ( Dictyotales) develops one single-flagellate spermatozoon. The oocyte is fertilized always after leaving the oogony (primitive oogamy). The zygote immediately, without a dormant period, germinates with a diploid thallus.

Most brown algae have a generation change - isomorphic or heteromorphic. The exception is representatives of the fucal order ( Fucales) that do not have asexual reproduction and that are diplants.

Almost all brown algae are found mainly in cold seas. They grow on rocks, stones, large shells, or as epiphytes on other types of algae. Large forms of representatives of the order are laminar ( Laminariales) form vast underwater forests. Brown algae reach their greatest development in the seas of temperate and polar latitudes, where the content of biogenic substances is quite high. They grow from the littoral zone to a depth of 40–100 (200) m. However, the most extensive and dense thickets are found to a depth of 6–15 m.

The importance of brown algae in nature is extremely great. They are the main source of organic matter in the coastal area. Their biomass can reach tens of kilograms per 1 m2. Thickets of brown algae are a place of shelter, feeding and breeding of many aquatic animals.

The role of brown algae in human economic activity is great. They are a valuable raw material for the production of alginates, which are widely used in food, medical, chemical and a number of other industries. Some algae (for example, kelp - "seaweed") are used by humans for food. Brown algae washed ashore, rich in nitrogen and potassium, are used as fertilizers.

Brown algae are very ancient organisms. Their fossils are known in the Silurian and Devonian strata of the Paleozoic era. Reliable fossil remains of brown algae have been found in Triassic sediments of the Mesozoic era. Brown algae probably evolved from some primary flagellates, in which brown pigments predominated. However, their connection with flagellates is more distant than in similar golden and yellow-green ones, since they do not have direct transitional forms (monadic, coccoid, trichal).

In the evolution of brown algae, there probably was a transition from intercalary growth (ectocarp, cutleria, laminaria) to apical (sphaceliaceae, dictyota, fucus). According to the second scheme of phylogenesis, the common ancestors of brown algae gave rise to three evolutionary branches, which differ in development cycles and morphological structure of thalli (classes are isogenetic, heterogeneous, and cyclosporous).

Class Isogenetic ( Isogeneratophyceae )

Brown algae belong to the class of isogenetic algae, in which the gametophyte and sporophyte exist as independent generations. Moreover, the gametophyte and the sporophyte are usually the same in shape and size.

The order of ectocarpal ( Ectocagrales ). Includes the most primitive forms, widespread in the littoral and sublittoral seas. They grow on stones, rocks, and other algae, usually in the form of brown bushes. A typical representative of the order is the genus Ectocarpus ( Ectocagrus). Gametophyte and sporophyte bushes reach a length of 30 (60) cm. They consist of filaments creeping along the substrate, from which vertical branched filaments grow. The threads are formed by one row of cells. Creeping filaments have apical growth, vertical ones - diffuse (intercalary, apical) growth. Multicellular colorless hairs are often formed at the ends of the vertical filaments. The cells contain large ribbon-like or lamellar chromatophores, vacuoles, and granules of assimilation products.

Asexual reproduction is carried out by double-flagellate zoospores, which are formed on diploid thalli (sporophytes) in unilocular sporangia. Sporangia are large terminal cells of short lateral branches. Meiosis occurs before the formation of zoospores. The formed haploid zoospores germinate with haploid thalli (gametophytes), on which biflagellate gametes are formed in the multi-nested fusiform gametangia. Mature gametes enter the water through the tops of the gametangium and copulate. A zygote without a dormant period sprouts as a diploid sporophyte. Thus, the ectocarpus has an isomorphic alternation of generations. However, there may be deviations depending on the environment. On sporophytes, in addition to single-celled sporangia, with haploid spores, multi-celled sporangia with diploid zoospores can develop, giving again diploid thalli. And gametes formed in multi-nested gametangia of gametophytes may not merge, but parthenogenetically germinate with a haploid thallus. Consequently, the correct alternation of generations does not always take place in ectocarpus.

The order is clerical ( Sphacelariales ). Genus sfacelia ( Sphacelaria). Like ectocarpus, it is widespread in the seas. Thallus is a dark brown bush up to 4 cm, attached to the substrate by a crustal plate, or stolons. The growth of thallus branches is strictly apical. In the older parts of the thallus, the cells of the vertical branches divide not only in the transverse, but also in the longitudinal direction. As a result, in the middle of the branch there is a group of large cells surrounded by small cells with numerous chromatophores. The lateral branches of the thallus are formed from the larger cells of the axial branch cortex.

As for the reproduction and development cycle, they are very similar to those of the ectocarpus. During vegetative propagation, in some species of sphacelia, special branches (brood buds) are formed.

Order of cutlerials (Cutleriales). The peculiarity of the representatives of this order is the trichothallic growth of the thallus and the heterogamous sexual process. The most famous genus is the cutleria ( Cutleria). Thallus gametophyte ( C. multifida) is an upright cutleria bushes up to 40 cm tall, attached to the substrate. Branches are ribbon-like, twice dichotomously branched, ending in parallel growing multicellular hairs. The hair cells contain numerous chromatophores. At the base of the hairs there is a growth zone. This is where cells divide. Those of them that are detached outward give rise to hairs; those that divide towards the thallus, are tightly connected by the sides, are repeatedly divided in the transverse and longitudinal directions, and form a dense parenchymal thallus. In the older parts of the thallus, there is a large-cell parenchyma in the center, and a small-cell cortex outside. The cells of the cortex contain a large number of chromatophores.

On the surface of the branches of the gametophyte, bundles of branched filaments develop. Gametangia are formed laterally on them. Female gametangia, consisting of few cells, are formed on some thalli; male - from numerous small cells, differentiate on other thalli. Female biflagellate gametes are noticeably larger than male biflagellate gametes. The female macrogamete released from the gametangium is fertilized by the male gamete after the cessation of movement. The zygote immediately sprouts as an annual or perennial cortical thallus (sporophyte), up to 10 cm in diameter. Sori of unilocular sporangia are formed on the diploid sporophyte. After reduction fission of nuclei, 4–32 zoospores develop in sporangia. Zoospores grow into a bushy haploid thallus that forms gametangia. Thus, the cutleria has an alternation of developmental forms, in which the gametophyte and sporophyte are outwardly different from each other.

Dictyotal order ( Dictyotales ). Thallus lamellar or dissected into lobes, or dichotomously branched in one plane, up to 50 cm high. Apical growth. Asexual reproduction by aplanospores (tetraspores). The sexual process is oogamous. The generation change is isomorphic. They grow in tropical and subtropical seas.

The genus of dictyot ( Dictyota). Thallus in the form of ribbons dichotomously branched in one plane, up to 20 cm long, grows from the conical sole, attached to the substrate by rhizoids. The ribbon-like branch of the thallus consists of three layers of cells. The middle layer is formed by large cells with few or no chromatophores. On one side and the other, the middle layer is surrounded by a layer of small cells with numerous chromatophores. From the outer cortical cells, bundles of colorless hairs grow, diffusely located on the surface of the ribbon-like branches.

On sporophytes, only unilocular tetrasporangia develop from superficial crustal cells, in which four flagellate tetraspores are formed each. Tetraspores germinate with gametophytes. On female gametophytes, oogonia develop in close groups (sori), on male gametophytes, multi-chamber antheridia, producing single-flagellate spermatozoa. After fertilization, the eggs germinate with sporophytes without a dormant period.

Rodin's family ( Padina). It has a fan-shaped thallus up to 20 cm high. On one side of the thallus there is a thin layer of lime. The developmental cycle is similar to the developmental cycle of dictyota, however, oogonia and antheridia develop on the same thalli.

Class Heterogeneous ( Heterogeneratophyceae )

In the development cycle of heterogeneous algae, there is a heteromorphic alternation of generations: a large sporophyte usually alternates with a microscopic gametophyte.

The order is laminar ( Laminariales ). The order unites the highest representatives of the heterogeneous class.

Kelp genus ( Laminaria). Widely distributed in the sublittoral of the northern seas. The sporophyte thallus reaches several meters in length and consists of a stem attached by rhizoids to the substrate and a plate growing from it or a plate dissected into the lobes. The stem and rhizoids are perennial; the blade grows from the stem annually. The thallus growth zone is located at the transition of the leaf blade into the stem. As a result of the activity of the intercalary meristem, the growth of the plate and the stem occurs. In the sporophytes of kelp (and other representatives), there is an outer small-cell colored bark (meristoderm), and under it, an inner large-cell colored bark, large colorless cells of the intermediate layer and a core in the form of a loose interlacing of filaments. The threads perform not only a mechanical, but also a conductive function.

Kelp reproduces asexually and sexually. During asexual reproduction, unicellular zoosporangia are formed on both sides of the leaf blade in the form of large groups (sori). The biflagellated zoospores that emerged from them grow into microscopic filamentous outgrowths. The cells of the female outgrowths turn into oogonia with one egg. On the threads of male outgrowths in the form of lateral outgrowths, unicellular antheridia with spermatozoa are formed. A mature egg comes out of the oogonia, but does not detach from its shell. After fertilization of the egg by the sperm, the zygote without a dormant period develops into a multicellular large kelp.

In the northern seas, it is very common Laminariasaccharina and Laminariadigitata... In the first, the leaf-shaped plate is whole, in the second it is finger-dissected and more dense.

Genus macrocystis ( Macrocystis). Distributed mainly in the southern hemisphere. Thallus can reach 60 m in length. It consists of a long thin branched trunk up to 1 cm thick, on which leaf-shaped 1–1.5 m plates are located in its upper part, having an air bubble at the base.

Genus nereocystis ( Nereocystis). One-year thallus, up to 50 m long, at the top a large air bubble, usually up to 15 cm, is formed. At the top of the bubble, short, dichotomously branched branches grow, which bear long leaf-shaped, up to 5 m long plates.

Rod lessonia ( Lessonia). Distributed mainly in the Southern Hemisphere. The trunk is up to 4 m long and as thick as a human's thigh. At the top it has numerous ramifications that end in lanceolate terminal branches.

Genus alaria ( Alaria). Thallus in the form of a plate up to 20 m or more, growing from the stem, attached to the substrate by rhizoids. There is a median vein on the plate. Zoosporangia soruses are formed on special leaflets (sporophylls), on the thallus stem.

Class Cyclosporous ( Cyclosporophyceae )

Brown algae, which have no alternation of generations in their life cycle. On diploid thalli, only the organs of sexual reproduction of antheridia and oogonia are formed in special spherical cavities - scaffidias, or concept dolls... Meiosis occurs before gamete formation. Fertilization of the egg and the development of the zygote occurs outside the thallus. There is no asexual reproduction.

Thallus is diverse in shape and often has a complex morphological structure. Differentiation of tissues resembles that of laminaria, however, sieve tubes are absent in cyclospores.

Fucal order ( Fucales ). The thallus is rather large, of various shapes, usually of a complex morphological and anatomical structure. Apical growth. Asexual reproduction is absent. The sexual process is oogamous. Skafidia with genitals are either dispersed diffusely throughout the thallus, or concentrated in recipes... Fertilization of the egg and the development of the zygote occurs outside the thallus.

Rod fucus ( Fucus). Widely distributed in the littoral and sublittoral of the northern seas. Thallus in the form of bushes up to 1 m. Branches are flat, belt-like, dichotomously branched, dark brown in color, with a median vein. Downward, the thallus narrows and turns into a petiole, which is firmly attached to the substrate by an expanded base - a basal disc. On the branches of the thallus of some species of the genus Fucus, on both sides of the midvein there are air cavities, or swim bladders, due to which the alga quickly takes a vertical position during high tide. The growth of the thallus is apical. Outside, the branches are covered with a multilayer multicellular cortex, under which there is a zone of elongated cells and secondary developing multicellular filaments that perform a mechanical function.

During reproduction, the ends of the branches of the thallus swell and turn into receptacles, in which scaphidia with narrow outlet openings are formed along the periphery. From the walls of the scaphidium, multicellular hairs grow inside it - paraphysis, sometimes emerging from the outlet in the form of a tuft. Between the paraphysis on the walls of the female scaphidium in the form of large oval cells with a short stalk, oogonia develop, containing 8 eggs each. Antheridia in the form of oval cells with granular contents are formed at the ends of branching filaments, similar to paraphysis. Each antheridium contains 64 sperm cells. Dissolved fucus form female and male scaphidia on different thalli. The swelling mucus of the oogonia and antheridia are pushed out, the gametes are released, the egg is fertilized by one of the spermatozoa. A zygote without a dormant period develops into a diploid fucus thallus.

The genus Ascophyllum ( Ascophyllum). Thallus branched, up to 1.5 m long, with several compressed cylindrical branches, without a median vein. Dichotomous branching, mainly in the upper parts of the thallus. Swimming bladders are often large, developing one at a time along the thallus. On the short branches of the older branches, swelling forms of recipes containing scaphidia. The structure of scaphidia is almost the same as that of fucus, only 4 oocytes are formed in oogonia.

Genus cystoseira ( Cystoseira). Found in the southern seas. The largest algae in the Black Sea. Thallus bushy, with monopodial branching, attached to the substrate by a disk, less often by rhizoids, reaching several meters in length. Air bubbles in groups in the form of a rosary develop more abundantly closer to the apex of the thallus. The ends of branches and often air bubbles near them turn into recipes.

Rod Sargassum ( Sargassum). Often grows in the sublittoral zone of warm seas. Thallus bushy, complexly dissected, attached to the substrate by a disc (sole), less often by rhizoids. The short stem branches monopodially. Leaf-like lateral branches, short twigs with spherical air bubbles and branched twigs, bearing at the ends of the recipe (conceptacula) with scaphidia, extend from it. In female scaphidia in oogonia, one egg is formed, inside male scaphidia in antheridia - 64 spermatozoa each. The gametes are pushed into the water by the swelling mucus. The egg is fertilized by the sperm. The zygote immediately develops into a diploid thallus.

Sargassum can reproduce vegetatively. Thus, for example, thalli of sargassum cut off from the substrate in the Sargasso Sea, as a result of its intensive vegetative reproduction, formed vast, powerful accumulations.

Chapter 2. Diversity flora

§ 10. Diversity of algae (continued)

Multicellular green algae

In multicellular representatives of green algae, the body (thallus) has the form of filaments or flat leaf-like formations. In flowing bodies of water, one can often see bright green accumulations of silky filaments attached to underwater rocks and driftwood. It is a multicellular filamentous green alga. ulotrix(fig. 21). Its filaments are made up of a series of short cells. In the cytoplasm of each of them there is a nucleus and a chromatophore in the form of an open ring. The cells divide and the filament grows.

In stagnant and slowly flowing waters, slippery bright green lumps often float or settle to the bottom. They look like cotton wool and are formed by clumps of filamentous algae. spirogyrs(see fig. 21). The elongated cylindrical cells of Spirogyra are covered with mucus. Inside the cells there are chromatophores in the form of spirally twisted ribbons.

Multicellular green algae also live in the waters of the seas and oceans. An example of such algae is ulwa, or sea salad, more than 30 cm long and only two cells thick (see fig. 17).

Chara algae have the most complex structure among green algae. They are often singled out as an independent department.

Brown algae

They mainly live in freshwater bodies, but they can also be found in brackish waters. These numerous green algae resemble horsetails in appearance. Charovaya algae found luu or custard is flexible, often grown in aquariums. Charovy have formations that resemble roots, stems, leaves in shape and functions, but in structure they have nothing to do with these organs of higher plants. For example, they attach to the ground using colorless branchy filamentous cells, which are called rhizoids(from the Greek. times- root and eidos- view).

Department of Brown algae, Department of Red algae, or Crimson algae, Rhizoids, Green algae, Brown algae, Red algae

Brown algae are mainly marine plants. A common external feature of these algae is the yellowish-brown coloration of the thalli. There are about 1500 species of them.

Brown algae are multicellular plants. Their length ranges from microscopic to gigantic (several tens of meters). Brown algae are attached to the ground by rhizoids or a disc-shaped overgrown base of the thallus. Some brown algae develop groups of cells that can be called tissues.

A large brown algae grows in our Far Eastern seas and the seas of the Arctic Ocean kelp, or seaweed (fig. 22). Brown algae are often found in the coastal strip of the Black Sea cystoseira.

Brown algae, like red algae, almost always live in the seas and oceans, that is, in salt waters. They are all multicellular. Among brown algae, there are the largest representatives of all algae. Mostly brown algae grow at a shallow depth (up to 20 m), although there are species that can live at a depth of up to 100 m. In the seas and oceans, they form a kind of thickets. Most brown algae live in the subpolar and temperate latitudes. However, there are also those that grow in warm waters.

Brown algae, like green algae, are capable of photosynthesis, that is, their cells contain the green pigment chlorophyll. However, they also have many other pigments with yellow, brown, orange colors. These pigments "interrupt" the green color of the plant, giving it a brownish tint.

As you know, all algae are lower plants. Their body is called the thallus, or thallus, there are no real tissues and organs. However, in a number of brown algae, the body is dismembered into the semblance of organs; different tissues can be distinguished.

Some types of brown algae have a complexly dissected thallus, which is more than 10 m long.

The vast majority of brown algae attach themselves to underwater objects. They do this with the help of rhizoids or the so-called basal discs.

Brown algae show different types of growth. Some species grow at their top, in others, all thallus cells retain the ability to divide, in others, surface cells divide, and fourths have special zones of cells in the body, the division of which leads to an increase in tissues above and below them.

The cell walls of brown algae consist of an inner cellulosic layer and an outer gelatinous layer, which includes various substances (salts, proteins, carbohydrates, etc.).

The cells have one nucleus, many small disc-shaped chloroplasts. Chloroplasts differ in structure from those of higher plants.

As a reserve nutrient, not starch is deposited in the cells of brown algae, but another polysaccharide and one of the alcohols. Cells contain vacuoles with polyphenolic compounds.

Brown algae have both sexual and asexual reproduction.

Reproduction of brown algae))

They can reproduce by fragmentation of their thallus, some species form brood buds. Asexual reproduction is also carried out by spores formed in sporangia. Most often, spores are mobile (have flagella), that is, they are zoospores. Spores give rise to a gametophyte that forms sex cells, the fusion of which gives rise to a sporophyte. Thus, the alternation of generations is observed in brown algae. However, in other species, gametes are formed by a sporophyte, that is, the haploid stage is represented only by eggs and sperm.

It is noted that brown algae emit pheromones, which stimulate the release of sperm and their movement to the eggs.

The most famous representative of brown algae is kelp, which a person eats, calling it seaweed. It has rhizoids, with which it attaches to underwater objects (stones, rocks, etc.). The kelp has a semblance of a stem (stem), this part of the plant is not flat, but cylindrical. The length of the stem is up to half a meter, from it there are similarities of flat sheet plates (several meters each).

Human brown algae are used not only for food, they are used in the food and textile industries, and some medicines are made from them.

Brown algae

Brown algae is a department of true multicellular brown algae. This group of plants includes 250 genera and about 1500 species. The most famous representatives are kelp, cystoseira, sargass.

These are mainly marine plants, only 8 species are secondary freshwater forms. Brown algae are ubiquitous in the seas of the globe, reaching a particular diversity and abundance in cold water bodies of the subpolar and temperate latitudes, where they form large thickets in the coastal strip. In the tropical zone, the largest accumulation of brown algae is noted in the Sargasso Sea; their mass development usually occurs in winter, when the water temperature drops. Vast underwater forests are formed by kelp algae off the coast of North America.

Brown algae are usually attached to hard substrates such as rocks, rocks, shellfish, and other algae thalli. In size, they can reach from several centimeters to several tens of meters. The multicellular thallus is colored from olive green to dark brown, since in the cells, in addition to chlorophyll, there is a significant amount of brown and yellow pigments.

reproduction and development cycle of brown algae

These plants have the most complex structure of all algae: in some of them, the cells are grouped in one or two rows, which resembles the tissues of higher plants. The species can be both annual and perennial.

Tall... In algae of this group, thallus can be of various shapes: creeping or vertically "hanging" filaments, plates (whole or cut) or branching bushes. The thalli are attached to a solid substrate by means of rhizoids (soles). Higher brown algae of the order laminaria and fucus are characterized by differentiation of tissue structures and the appearance of conducting systems. Unlike algae of other groups, brown algae are characterized by the presence of multicellular hairs with a basal growth zone.

Cell structure... The cover is a thick cell wall, consisting of two or three layers, which is very slimy. The structural components of the cell wall are cellulose and pectin. Each cell of brown algae contains one nucleus and vacuoles (from one to several). Chloroplasts are small, disc-shaped, brown in color due to the fact that, in addition to chlorophyll and carotene, they have a high concentration of brown pigments - xanthophylls, in particular fucoxanthin. Also in the cytoplasm of the cell are deposited reserves of nutrients: laminarin polysaccharide, polyhydric alcohol mannitol and various fats (oils).

Reproduction of brown algae... Reproduction is carried out asexually and sexually, rarely vegetatively. The organs of reproduction are sporangia, both unilocular and multi-celled. Usually there is a gametophyte and a sporophyte, and in the higher algae they alternate in a strict sequence, while in the lower algae there is no clear alternation.

Meaning... The importance of brown algae in nature and human life is great. They are the main source of organic matter in the coastal zone of the seas. In the thickets of these algae, occupying vast areas, many Marine life... Used in industry in the production of alginic acids and their salts, to obtain feed meal and powder for the manufacture of medicines containing high concentrations of iodine and a number of other microelements. In aquariums, the appearance of brown algae is associated with insufficient lighting. Some species are eaten.

Department of Brown Algae. General characteristics.

Brown algae are common in the seas and oceans of the whole world, they live mainly in coastal shallow waters, but also far from the coast, for example, in the Sargasso Sea. They are an important component of benthos.
The brown color of the thallus is due to a mixture of different pigments: chlorophyll, carotenoids, fucoxanthin. A set of pigments enables photosynthetic processes, since chlorophyll does not capture those wavelengths of light that penetrate to depth.
In low-organized filamentous brown algae the thallus consists of one row of cells, while in highly organized cells they not only divide in different planes, but partially differentiate, as if forming "petioles", "leaves" and rhizoids, with the help of which the plant is fixed in the substrate.
The cells of brown algae are mononuclear, chromatophores are granular, numerous. Spare products are contained in them in the form of polysaccharide and oil. Pectin-cellulose walls are easily slicked, apical or intercalary growth.
Asexual reproduction (absent only in fucus) is provided by numerous biflagellated zoospores formed in unicellular, less often multicellular zoosporangia.
Asexual vegetative reproduction is carried out by parts of the thallus.
The forms of the sexual process: isogamy, heterogamy and oogamy.
All brown algae, except for fucus algae, have a pronounced change in developmental phases. Reduction division occurs in zoosporangia or sporangia, they give rise to a haploid gametophyte, which is bisexual or dioecious. A zygote without a dormant period grows into a diploid sporophyte. In some species, the sporophyte and gametophyte do not differ externally, while in others (for example, in kelp) the sporophyte is more powerful and more durable.

Brown algae - structure and reproduction, features and causes

In fucus, a reduction of the gametophyte is observed, since the gametes merge outside the mother plant, in the water. A zygote without a dormant period develops into a diploid sporophyte.

Among brown algae, there are both microscopic and macroalgae. The latter can reach gigantic sizes: for example, algae macrocystis can reach 30-50 m in length. This plant grows very quickly, giving a large amount of extracted biomass, per day the algae thallus grows by 0.5 meters. In the course of evolution, sieve tubes similar to those found in vascular plants appeared in the thallus of macrocystis. Of the types of macrocystis, a special group of substances is extracted - alginates - mucous intercellular substances. They are widely used as thickening agents or colloid stabilizers in the food, textile, cosmetics, pharmaceutical, pulp and paper industries, as well as in welding. Macrocystis can produce several harvests per year. Attempts are now being made to cultivate it on an industrial scale. In the thickets of macrocystis, hundreds of animal species find protection, food, and breeding grounds. Charles Darwin compared its thickets with terrestrial tropical forests: "If in any country to destroy forests, I do not think that approximately such a number of animal species would die, as with the destruction of thickets of this algae."

Fucus Is a dichotomously branching brown alga with air bubbles at the ends of the plates. Thallus reach 0.5-1.2 m in length and 1-5 cm in width. These algae densely cover many of the rocky areas exposed at low tide. When the algae is flooded with water, air-filled bubbles carry them out into the light. The rate of photosynthesis in seaweed often exposed to air can be up to seven times faster in air than in water. Therefore, algae occupy the coastal zone. Fucus does not have an alternation of generations, but only a change in nuclear phases: the whole alga is diploid, only gametes are haploid. Reproduction by spores is absent.

Laminaria ("kombu") in China and Japan are regularly used as vegetables; they are sometimes bred, but mainly taken from natural populations. The greatest economic importance is seaweed (kelp), it is prescribed for sclerosis, a violation of the thyroid gland, as a mild laxative. Previously, it was burned, the ash was washed, the solution was evaporated, in this way soda was obtained. The soda was used to make soap and glass. At the beginning of the 19th century, 100 thousand tons of dry algae were burned in Scotland per year. Since 1811, thanks to the French industrialist Bernard Courtois, iodine was obtained from kelp. In 1916, 300 tons of iodine were extracted from seaweed in Japan. Kelp is a large brown alga with a length of 0.5-6 m, consists of leaf-like plates, a stem (trunk) and a structure for attachment to the substrate (rhizoids). The meristem zone is located between the plate and the stem, which is very important for industrial use. When the fishermen cut off the regrown plates of this alga, its remaining deeper parts are regenerated. The trunk and rhizoids are perennial, and the plate changes annually. This structure is typical for a mature sporophyte. On the plate, unilocular zoosporangia are formed, in which mobile zoospores mature and grow into gametophytes. They are represented by microscopic filamentous growths consisting of several cells that carry the genitals. Thus, kelp has a heteromorphic cycle with a mandatory alternation of generations.

Department of Red Algae. general characteristics

Red algae are common in the seas of tropical and subtropical countries and partly in the temperate climate (the Black Sea coast and the coast of Norway). Some species are found in freshwater and soil.
The structure of the thallus of red algae is similar to the structure of the thalli of the most highly organized brown algae. Thallus has the form of bushes, composed of multicellular branching filaments, less often lamellar or leaf-shaped, up to 2 m in length.
Their color is due to such pigments as chlorophyll, phycoerythrin, phycocyan. They live in deeper waters than brown ones and require additional pigments to capture light. Due to the presence of phycoerythrin and phycocyanin, they got their name - red algae.
Chromatophores in red algae have the form of discs; there are no pyrenoids. Spare products are contained in them in the form of oil and red algae-specific purple starch, which turns red from iodine. In some species, the pectin-cellulose cell walls become mucous so much that the entire thallus acquires a slimy consistency. Therefore, some types are used to obtain agar-agar, which is widely used in the food industry for the preparation of nutrient media for the cultivation of bacteria and fungi. The cell walls of some red algae can be encrusted with calcium carbonate and magnesium carbonate, which gives them the hardness of a stone. Such algae are involved in the formation of coral reefs.
Red algae have no mobile stages in the development cycle. They are characterized by a very special structure of the organs of sexual reproduction and the form of the sexual process. Most scarlet plants are dioecious plants. Mature sperm (one immobile gamete) emerge from the antheridia into the aquatic environment and are carried by currents of water to the carpogon (female organ of sexual reproduction). The contents of the sperm penetrate into the abdomen of the carpogon and merge there with the ovum. The zygote without a dormant period divides by mitosis and grows into filamentous thalli of different lengths. Thallus is diploid. In the upper part of these filaments, sexual reproduction spores (carpospores) are formed. With asexual reproduction on the thallus, sporangia are formed, which contain one spore each - a monospore, or four each - tetraspores. Before the formation of a tetraspor, a reduction division occurs. In monosporous algae, gametangia and sporangia are formed on the same monoploid plant; only the zygote is diploid. For tetrasporous, alternation of developmental phases is characteristic: haploid tetraspores grow into a haploid gametophyte with gametangia; Diploid carpospores grow into diploid plants with sporangia (diploid sporophyte). Gametophyte and sporophyte are indistinguishable in appearance. In porphyry and porphyridium, asexual reproduction is carried out by monoploid monospores. They go through the entire developmental cycle in a haploid state; only the zygote is diploid in them (as in many algae).

Lives in the Black Sea. Half of the agar obtained in Russia is made from this crimson.

Distribution of algae in water and on land. The value of algae in nature and economy.

Terrestrial algae are also quite abundant, but usually not seen due to their microscopic small size. However, greening of the sidewalks, powdery green deposits on the trunks of thick trees indicate accumulations of soil algae. These organisms are found in the soils of most climatic zones. Many of them contribute to the accumulation of organic matter in soils.

Algae of ice and snow are microscopically small and are found only when a large number of individuals accumulate. The phenomenon of the so-called "red snow" has gained the greatest popularity for a long time. The main organism causing snow reddening is one of the types of unicellular algae - snow chlamydomonas. In addition to free-living algae, an important role in nature is played by algae - symbionts, which are the photosynthetic part of lichens.

Due to its wide distribution, algae are of great importance in the life of individual biocenoses and in the cycle of substances in nature. The geochemical role of algae is primarily associated with the calcium and silicon cycle. Making up the bulk of the plant and aquatic environment and participating in photosynthesis, they serve as one of the main sources of organic matter in water bodies. In the World Ocean, algae annually create about 550 billion tons (about ¼) of all organic matter on the planet. Their yield here is estimated at 1.3 - 2.0 tons of dry matter per 1 g of water surface per year. Their role is enormous in the nutrition of aquatic organisms, especially fish, as well as in the enrichment of the Earth's hydrosphere and atmosphere with oxygen.

Some algae, together with heterotrophic organisms, carry out the processes of natural self-purification of waste and polluted waters. They are especially useful in open "oxidation ponds" used in tropical and subtropical countries. Open ponds with a depth of 1 to 1.5 m are filled with untreated sewage. During photosynthesis, algae release oxygen and provide the vital activity of other aerobic microorganisms. Many of the algae are indicators of pollution and salinization of habitats. Soil algae are actively involved in soil formation.

The economic value of algae lies in their direct use as food products or as raw materials for obtaining various substances valuable to humans. For this purpose, especially those types are used, the ash of which is rich in sodium and potassium salts. Some brown algae are used as fertilizers and for feeding pets. Algae are not very nutritious because a person does not have enzymes that allow you to break down and digest substances of cell walls, but they are rich in vitamins, iodine and bromine salts, trace elements.

Under certain conditions, algae "bloom", ie. accumulate in large quantities in water. "Blooming" is observed in warm enough weather, when the water is observed eutrophication , i.e. a lot of nutrients (industrial effluents, fertilizers from the fields). As a result, an explosive multiplication of the primary producers, algae, begins, and they begin to die off before they can be eaten. In turn, this causes an intensive multiplication of aerobic bacteria, and the water is completely deprived of oxygen. Fish and other animals and plants perish. Toxins formed during water bloom increase the death of animals, they can accumulate in the body of mollusks and crustaceans that feed on algae, and then, getting into the human body, cause poisoning and paralysis in him.

the value of brown algae

Brown algae are one of the main sources of organic matter in the coastal zone, especially in the seas of the temperate and circumpolar zones, where their biomass can reach tens of kilograms per square meter. Thickets of brown algae serve as a shelter, breeding and feeding place for many coastal animals, in addition, they create conditions for the settlement of other microscopic and macroscopic algae. The role of brown algae in the life of coastal waters is seen in the example of Macrocystis, about whose thickets off the coast of South America Charles Darwin wrote: “These huge underwater forests of the southern hemisphere I can only compare with terrestrial forests of tropical regions. And yet, if a forest were to be destroyed in some country, I don’t think that at least approximately as many animal species would die as with the destruction of this algae. "

The role of brown algae in human economic activity is also great. Together with other organisms, they participate in the fouling of ships and buoys, impairing their performance.

Reproduction and development cycle of brown algae

But brown algae are of much greater importance as a raw material for obtaining various kinds of substances.

First, brown algae is the only source of alginates - alginic acid soda. Depending on which metals are involved in the formation of alginates, they can be water-soluble (monovalent metal salts) or insoluble (polyvalent metal salts other than magnesium). The most widely used is sodium alginate, which has all the properties of water-soluble alginates. It is capable of absorbing up to 300 weight units of water to form viscous solutions. Therefore, it is widely used to stabilize a variety of solutions and suspensions. The addition of a small amount of sodium alginate improves the quality of food (canned food, ice cream, fruit juices, etc.), a variety of dyes and adhesives. Solutions with the addition of alginates do not lose their qualities during freezing and thawing. The use of alginates improves the quality of printing books, makes natural fabrics colorfast and waterproof. Alginates are used in the manufacture of plastics, synthetic fibers and plasticizers, to obtain weather-resistant paints and varnishes and building materials... They are used to produce high-quality lubricants for machines, soluble surgical sutures, ointments and pastes in the pharmaceutical and perfume industries. IN foundry alginates improve the quality of the molding earth. Alginates are used in fuel briquetting, in the production of electrodes for electric welding, allowing for higher quality welds. It is difficult to name a branch of the national economy where alginates are not used.

Another important substance obtained from brown algae is the hexahedral alcohol mannitol. It is used in the pharmaceutical industry for the manufacture of tablets, in the preparation of diabetic foodstuffs, in the production of synthetic resins, paints, paper, explosives, and in the manufacture of leather. More and more mannitol is used in surgical operations.

Brown algae contain a large amount of iodine and other trace elements. Therefore, they go to the preparation of feed flour, which is used as an additive to feed for farm animals. Due to this, the mortality of livestock is reduced, its productivity increases, in a number of agricultural products (eggs, milk) the iodine content increases, which is important for areas where the population suffers from its lack.

Once brown algae were processed in large quantities to obtain iodine, but now only waste from the algal industry is used for this purpose: due to the emergence of other, more cost-effective sources of iodine production, it has become more profitable to process brown algae into other substances.

Fresh and processed brown algae are used as fertilizers.

Brown algae have long been used in medicine. Now all new directions of their use are being identified, for example, for the manufacture of blood substitutes, for the production of drugs that prevent blood clotting, and substances that contribute to the removal of radioactive substances from the body.

Since ancient times, brown algae have been eaten, especially by the peoples of Southeast Asia. Of the greatest importance in this regard are representatives of the kelp order, of which they prepare the largest number of a wide variety of dishes.