Brown Algae: Definition, Types, and Examples

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Brown Algae: All You Need To Know

Brown algae are multicellular algal species with a brown or greenish brown hue and a brown or greenish brown tint. In addition to the green pigments, the hue is attributable to the preponderance of brown pigments, such as fucoxanthin (chlorophyll a and c).

Many of them are macro in nature. Kelps, in reality, are huge brown seaweeds that grow in shallow waters and create a kelp forest. Another macroscopic brown algal species is Fucus. They flourish in rocky seaside intertidal zones.

They are collected, dried, and processed into commercial soap, glass, and other products. Fertilizers are also made from them. Phaeophyta, Phaeophyceae, and Fucophyceae are synonyms.

Brown Algae Classification

There are five primary kingdoms in the previous categorization method. The kingdom of Protista is one of them (protists). There are three types of protozoa in this group: animal-like protozoa, plant-like algae, and fungus-like slime moulds and water moulds.

The various phyla of algae are Euglenophyta, Chrysophyta (diatoms), Pyrrophyta (dinoflagellates), Chlorophyta (green algae), Phaeophyta, and Rhodophyta. Recent research and results, on the other hand, may lead to modifications in taxonomic ranks and the development of new categorization systems.

The phylum Phaeophyta, for example, is no longer relevant. It used to be a phylum that included creatures known as brown algae. Brown algae belong to the Phaeophyceae family, which is one of the taxonomic groupings within the new phylum Ochrophyta.

The Phaeophyceae family of algae is distinguished by the presence of brown pigments such as fucoxanthin, which give them a brown or greenish-brown hue. Other phyla, however, have some brownish-colored algal species in addition to this class. Dinoflagellata (dinoflagellates) and Bacillariophyta are the two phyla (diatoms).

However, members of the Phaeophyceae family are more commonly referred to as brown algae. In contrast to the two phyla with single-celled members, Phaeophyceae contains multicellular algae species.

Brown Algae Sub-groups

The taxonomic orders that make up Phaophyceae are as follows: Ascoseirales, Asterocladales, Chordales, Desmarestiales, Dictyotales, Discosporangiales, Ectocarpales, Fucales, Ishigeales, Laminariales, Nemodermatales, Onslowiales, Phaeophyceae ordo incertae sedis, Phaeosiphoniellales, Ralfsiales, Scyto

Brown Algae Characteristics

Kelp is a brown algal species that contributes to the formation of the kelp forest. A Kelp forest provides a home for aquatic life. Giant kelp is the world’s longest algae species. It might grow to be more than 50 metres long.

Phaeophyceae is a group of multicellular algae that range in colour from olive green to brown. The size of the kelp can range from a small tuft of a few millimetres to a massive 50-meter-long kelp. Macrocystis pyrifera (giant kelp) is the biggest algae on the planet.

Fucoxanthin is responsible for their distinctive greenish-brown hue, which is dependent on the amount of fucoxanthin present. Chlorophyll a and c2 are also present, in addition to this pigment.

Laminarin (1-3 glucose polymer) is their carbohydrate reserve. Brown algae, like other algal species, undergo alternating generations. The sporophyte is the form that is most noticeable. Except for the Fucales, most brown algae reproduce sexually by sporic meiosis. Those with the ability to reproduce asexually use motile zoospores to replicate.

Unlike tracheophytes, Phaeophyceae have no circulatory tissues in their bodies (thallus). Brown algae lack real roots, stalks, and leaves as a result.

The holdfast is the name of the brown algae’s root-like structure. The holdfast acts as an anchor, similar to a real root, keeping the algal thallus from being carried away by the stream. The true root, on the other hand, is the main organ for water absorption.

The stipe is the stem-like component of the algal thallus. The stipe is made up of three layers in highly differentiated brown algae like Fucus: the outside epidermis, the intermediate cortex, and the inner core pith.

A core of phloem-like cells may be present in the pith. The pith of other species may be hollow and gas-filled, and therefore related to algal buoyancy. When the leaf-like structure is single and not divided, it is called a blade; when it is divided, it is called a frond; and when it is divided, it is called a lamina (when flattened).

Pneumatocysts are the air bladders in the thallus. They improve the buoyancy of algae. Brown algae are usually macroscopic and found in the sea. They fluorish in cold ocean waters, in particular.

Brown Algae Evolution and Phylogeny

Brown algae, which feature four-membraned chloroplasts, are thought to have developed through a symbiotic interaction between a basal eukaryote and another eukaryote. They are genetically more closely linked to yellow-green algae.

Biological importance of Brown Algae

Many aquatic creatures depend on these organisms for food and habitat. Kelps form a kelp forest, which provides a home for tiny aquatic creatures. Additional brown algal species, sargassum, create a floating mat that serves as another home for a variety of species.

Ascophyllum nodosum is a carbon-fixing plant. Brown algae incorporate alginate in their cell walls. It’s taken out to be used as a food thickener. For example, fungus species are collected for use in soap and glass production. They’re also used as agricultural fertilisers. Humans can eat a variety of other creatures.

Brown Algae Citations
  • Plasmodesmata of brown algae. J Plant Res . 2015 Jan;128(1):7-15.
  • Phenolic Content of Brown Algae (Pheophyceae) Species: Extraction, Identification, and Quantification. Biomolecules . 2019 Jun 22;9(6):244.
  • Antidiabetic Potential of Marine Brown Algae-a Mini Review. J Diabetes Res . 2020 Apr 25;2020:1230218.
  • Ectocarpus: an evo-devo model for the brown algae. Evodevo . 2020 Aug 31;11:19.
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