Brown algae are a large group of multicellular algae comprising the class Phaeophyceae. They include many seaweeds located in colder waters of the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and polar regions. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, Macrocystis, a kelp of the order Laminariales, may reach 60 m (200 ft) in length and forms prominent underwater kelp forests that contain a high level of biodiversity. Another example is Sargassum, which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Some members of the class, such as kelps, are used by humans as food.
Platycerium is a genus of about 18 fern species in the polypod family, Polypodiaceae. Ferns in this genus are widely known as staghorn or elkhorn ferns due to their uniquely shaped fronds. This genus is epiphytic and is native to tropical and temperate areas of South America, Africa, Southeast Asia, Australia, and New Guinea.
Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of red, but some species can be purple, yellow, blue, white, or gray-green. Coralline algae play an important role in the ecology of coral reefs. Sea urchins, parrot fish, and limpets and chitons feed on coralline algae. In the temperate Mediterranean Sea, coralline algae are the main builders of a typical algal reef, the Coralligène ("coralligenous"). Many are typically encrusting and rock-like, found in marine waters all over the world. Only one species lives in freshwater. Unattached specimens may form relatively smooth compact balls to warty or fruticose thalli.
Caulerpa is a genus of seaweeds in the family Caulerpaceae. They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world.
Cladophora is a genus of reticulated filamentous green algae in the class Ulvophyceae. They may be referred to as reticulated algae, branching algae, or blanket weed. The genus has a worldwide distribution and is harvested for use as a food and medicine.
Bryopsis is a genus of marine green algae in the family Bryopsidaceae. It is frequently a pest in aquariums.
Characiosiphon is a genus of green algae in the family Characiosiphonaceae. It contains a single species, Characiosiphon rivularis.
Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.
The Pertusariales are an order of fungi in the class Lecanoromycetes, comprising 8 families, 31 genera, and over 600 species, many of which form lichens. This diverse group is characterized by complex taxonomic history and ongoing phylogenetic revisions. Originally proposed by Maurice Choisy in 1949 and later formally published by the lichenologists David L. Hawksworth and Ove Eriksson in 1986, Pertusariales has undergone significant reclassification due to molecular phylogenetics studies. The order includes well-known genera such as Pertusaria and Ochrolechia, as well as families like Megasporaceae and Icmadophilaceae.
Red algae, or Rhodophyta, make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 recognized species within over 900 genera amidst ongoing taxonomic revisions. The majority of species (6,793) are Florideophyceae, and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, no terrestrial species exist, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.
Ulva intestinalis is a green alga in the family Ulvaceae, known by the common names sea lettuce, green bait weed, gutweed, and grass kelp. Until they were reclassified by genetic work completed in the early 2000s, the tubular members of the sea lettuce genus Ulva were placed in the genus Enteromorpha.
Hildenbrandia is a genus of thalloid red alga comprising about 26 species. The slow-growing, non-mineralized thalli take a crustose form. Hildenbrandia reproduces by means of conceptacles and produces tetraspores.
Hypnea is a genus of red algae, and a well known carrageenophyte.
Dictyota is a genus of brown seaweed in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals (diterpenes) which have potential medicinal value. As at the end of 2017, some 237 different diterpenes had been identified from across the genus.
Rhodelphis is a single-celled archaeplastid that lives in aquatic environments and is the sister group to red algae and possibly Picozoa. While red algae have no flagellated stages and are generally photoautotrophic, Rhodelphis is a flagellated predator containing a non-photosynthetic plastid. This group is important to the understanding of plastid evolution because they provide insight into the morphology and biochemistry of early archaeplastids. Rhodelphis contains a remnant plastid that is not capable of photosynthesis, but may play a role in biochemical pathways in the cell like heme synthesis and iron-sulfur clustering. The plastid does not have a genome, but genes are targeted to it from the nucleus. Rhodelphis is ovoid with a tapered anterior end bearing two perpendicularly-oriented flagella.
The Pterocladiophilaceae is a small family of red algae containing 2 genera of thallus parasitic algae.
Fritschiella aquatilis is a species of freshwater green alga in the family Chaetophoraceae. It features a unique globular, hairy morphology. It was discovered in the city of Taiyuan, Shanxi province, China, and can be found in freshwater aquariums with ornamental fish. The species exhibits some differences from the closely related Fritschiella tuberosa, which is primarily found in soil environments. Molecular phylogenetic data has supported the classification of F. aquatilis as a new species within the genus Fritschiella.
Hildenbrandia rivularis is a species of freshwater red algae. It forms red, crusty thalli on stones submerged in water, typically in streams and rivers, less commonly in lakes and brackish parts of seas. It occurs in scattered locations on almost all continents. The species was formerly considered an indicator of clean or slightly polluted waters. The scientific genus name is sometimes spelled in various orthographic variants, especially as Hildenbrandtia. The life cycle of this species was described by the Polish hydrobiologist Karol Starmach.
Batrachospermum is a genus of red algae from the family Batrachospermaceae. Due to its complex biological life cycle, descriptions of the taxon typically focus on gametophytes, while sporophytes, i.e., carposporophytes, are filamentous structures growing on the gametophyte, on which they depend. Independently living sporophytes have sometimes been described as separate species within the genus Chantransia. Additionally, differences may occur in the descriptions of the genus due to variations in taxonomic approaches, as new taxonomic techniques, as with other algae, result in changes in the assignment of individual species to the genus Batrachospermum. The genus is cosmopolitan, and its representatives are found in freshwater environments, mainly rivers, and less frequently in standing waters. These plants have thalli in the form of gelatinous-coated filaments.
There are many types of algae that are commonly found in a freshwater aquarium setting. They are typically considered a nuisance and subject to removal through the use of algicides, the release of algae eaters, and implementation of algae scrubbers. However, total elimination of algae is considered unlikely in a hobby aquarium. Algae can be used as an bioindicator to inform an aquarist on water chemistry and other conditions.
