Brown algae

Sägetang (Fucus serratus)

The brown algae ( Phaeophyceae, Syn: Phaeophyta ) form a distinct group within the Stramenopilen ( Stramenopila ), a subgroup of Chromalveolata. It is usually navy, often brown algae with alternation of generations.

A hallmark of this ply or sheet-like, definitely multicellular algae are the brown fucoxanthin dyes, which mask the green chlorophyll, so cover.

• 6.1 Notes and references

Features

The brown algae are a very rich form group. The habit ranges from small, branched hyphae, Fadenthalli, thalli pseudoparenchymatischen to complex, multi-layered, multiple meter Protoctista with tissue and organ differentiation. The bodies of these Tange remember sheet axis and root of the plant body and are called in analogy Phylloid, Cauloid and rhizoid. Protozoa are absent in the brown algae.

Plastids

The brown algae possess as any heterosexual accounts algae complex plastids (also called chromatophores ) without Nukleomorph caused by secondary endosymbiosis. Photosynthesis pigments are those of the hetero accounts: chlorophyll a, c1 and c2. As accessory pigments are β -carotene, fucoxanthin and to a lesser extent Diadinoxanthin and Diatoxanthin (both as xanthophylls fucoxanthin ). Usually only one chromatophore per cell is present, rarely more. The DNA is arranged in a Genophor from the ring type. The Reservepolysaccharid is Chrysolaminarin.

Scourge

The single-celled dreamer of brown algae ( zoospores and gametes) have the typical for the Stramenopilen two differently shaped flagella ( " heterokont "). The base of the trailing flagellum is swollen and perhaps serves as a photoreceptor. It is located in the vicinity of the eye spot, a red-brown spot in the chromatophore. The trailing flagellum always has a thin hair extension at the end, the Zuggeißel sometimes. This feature occurs only here and in the Xanthophyceae.

Cell wall

The cell walls of the brown algae containing alginates as in addition to the cellulose structure giving main components. The cellulose forms the fibrillar component that ensures the strength of the cell walls. The fibrils are embedded in an amorphous mucoid substance, which is composed of a colloidal solution in water alginates. An additional gain is made by insoluble alginate gels. This specific for the brown algae cell wall structure allows simultaneous strength and flexibility to withstand the mechanical loads due to tidal currents and wave movements.

Propagation

The brown algae undergo a generational change. The meiospores are formed in uniloculären ( unilocular ) sporocysts, the gametes in pluriloculären ( vielkammerigen ) gametangia. The generational change is heterophasic, that is, It haploid and diploid alternate generation. Within the brown algae, there is a line of development of gleichartigem ( isomorphic ) generation in a reduction of the haploid gametophyte: heteromorphic ( different multiform ) generation. In the Fucales the haploid generation is almost completely degenerated, so that they are almost pure diploid.

When the gametes there is a line of development of identical design gametes ( isogamy ) of various sizes, flagellated gametes ( Anisogamie ) to unbegeißelten female ova ( oogamy ).

Occurrence

The vast majority of species live in the sea. There are only five species known as freshwater residents. The greatest variety they develop in the temperate and cold latitudes of the oceans. They live as part of the benthos and are sessile as Lithophytes to rocks, stones and the like. Some are exposed at low water, or grow as epiphytes on other algae. In some areas, such as on the American Pacific coast, they form large underwater forests ( Tangwälder ). Here grow the giant Tange Lessonia, Macrocystis and Nereocystis. Smaller forms grow on stones, barnacles, snails and algae. Some species grow even larger in endophytic algae.

System

The brown algae are a group of Stramenopilen. Their sister group is likely to be a clade consisting of Xanthophyceae, Pinguiochrysidales and Phaeothamniophyceae.

The class Phaeophyceae was erected in 1891 by FRKjellman ( in: The natural plant families, Part 1, Division 2 ( Engler, A. & Prantl, K. Eds ), pp. 176-181 Engelmann, Leipzig.). The internal system is very often based on a classification according to the life cycle. Through gene sequence information, the system is currently in transition, the following classification of the orders is therefore only temporary. It follows the taxonomy of Adl et al. (2005) and Guiry in AlgaeBase (2012 ). The Phaeophyceae are currently divided into 17 orders and comprise about 1800 species.

• Ascoseirales Petrov, with the only kind Ascoseira mirabilis Skottsberg
• Asterocladales T.Silberfeld, M. F.Racault, RLFletcher, AFPeters, F.Rousseau & B.de coalfield, with the only genus Asterocladon DGMüller, ERParodi & AFPeters, with 3 types
• Cutleriales Bessey, with 3 genera and 11 species: Cutleria Greville, with 9 species
• Microzonia J.Agardh, with the only kind Microzonia velutina ( Harvey ) J.Agardh
• Zanardinia Nardo ex Zanardini, with the only kind Zanardinia typus ( Nardo ) PCSilva

• Stacheltang ( Desmarestia aculeata )

• Trichteralge ( Padina pavonica )

• Knotted ( Ascophyllum nodosum )
• Fucus L., with 15 species, including: Sägetang (Fucus serratus)
• Spiraltang (Fucus spiralis )
• Bladderwrack (Fucus vesiculosus)

• Kelp ( Laminaria digitata )
• Palmentang ( Laminaria hyperborea )
• Giant kelp ( Macrocystis pyrifera )
• Japanese kelp ( Saccharina japonica)
• Sugar kelp ( Saccharina latissima )

• Onslowia Searles, with 2 types
• Verosphacela E.C.Henry, with 2 types

• Saccorhiza polyschides ( Lightfoot ) Batters

Some frequent Northeast Atlantic species are:

• Flügeltang ( Alaria esculenta )
• Knotted ( Ascophyllum nodosum )
• Gabelzweigtang ( Bifurcaria bifurcata )
• Stacheltang ( Desmarestia aculeata )
• Sägetang (Fucus serratus)
• Spiraltang (Fucus spiralis )
• Bladderwrack (Fucus vesiculosus)
• Schotentang ( Halidrys siliquosa )
• Riementang ( Himanthalia elongata )
• Kelp ( Laminaria digitata )
• Palmentang ( Laminaria hyperborea )
• Rinnentang ( Pelvetia canaliculata )
• Sugar kelp ( Saccharina latissima )

For occurring in the German Bight brown algae also see the list of marine algae of Heligoland.

Use

From brown algae alginates are obtained, which are used as gelling agents use. Alginates are a by-product in the recovery of iodine from seaweed in the wet process. Due to the various application possibilities Alginates are extracted directly for use in the food and pharmaceutical and cosmetic industry from the brown algae. Brown algae of the genera Macrocystis, Laminaria, Ascophyllum, Sargassum, Ecklonia, Lessonia and Durvillea be for harvested with trawlers.

Some species are also eaten, as kombu ( Saccharina japonica and other Saccharina species), wakame ( Undaria pinnatifida ) and Cochayuyo ( Durvillaea antarctica).

The burning of seaweed to calcium, iodine and alkali - rich ash (English: kelp, not to be confused with the sometimes referred to as kelp in the German giant Tangen ) for the manufacture of glass and soap industry, was founded in the 17th century in France 1719 and introduced by James Fea on Orkney. The shallow coastal waters and coastline make the Northern Isles of Orkney, Sanday and Stronsay especially to ideal places. The Tang was cut at low tide from the rocks or found after storms ashore. Situated on the peak of production, produced Orkney annually more than 3,000 tons. The Kelp boom lasted only 50 years, from 1780 to 1830. As in the 1840s, iodine was asked the kelp industry woke up again at a lower level.