''Caulerpa brachypus'' is a species of seaweed in the ''

Caulerpaceae Caulerpaceae is a family of green algae in the order Bryopsidales Bryopsidales is an order of green algae, in the class Ulvophyceae. Characteristics The thallus is filamentous and much branched and may be packed into a mass. It is coenocytic ...

'' family. It was first described in 1860 by the Irish botanist William Henry Harvey, having been collected during the North Pacific Exploring and Surveying Expedition of 1853 to 1856. It is native to the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region and has spread elsewhere. It is regarded as an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

in the United States,

Martinique Martinique ( , ; gcf, label=Martinican Creole, Matinik or ; Kalinago: or ) is an island and an overseas department/region and single territorial collectivity of France. An integral part of the French Republic, Martinique is located in th ...

and New Zealand.

Description

''Caulerpa brachypus'' is a green

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

with a horizontal creeping

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

which sends up blade-like fronds on short rhizoids at intervals. These

thalli Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...

are tongue-like or strap-like in shape, up to long and mainly green, sometimes with yellowish margins. Where they occur together, it is difficult to distinguish this species from other members of the genus '' Caulerpa'', especially as there is considerable variation between different populations of ''Caulerpa brachypus'' growing in different habitats. Where conditions suit it, it can become very profuse and form dense stands.

Distribution

''Caulerpa brachypus'' is native to the tropical and subtropical

region. Its range includes East Africa, India, southeastern and eastern Asia, the Pacific Islands and Western Australia. It is found along the Western Australia coast scattered over a large area in the

Pilbara The Pilbara () is a large, dry, thinly populated region in the north of Western Australia. It is known for its Aboriginal peoples; its ancient landscapes; the red earth; and its vast mineral deposits, in particular iron ore. It is also a glo ...

region between

Exmouth Exmouth is a harbor, port town, civil parishes in England, civil parish and seaside resort, sited on the east bank of the mouth of the River Exe and southeast of Exeter. In 2011 it had a population of 34,432, making Exmouth the List of town ...

and Port Hedland. It was first detected in the United States, in

Martin County, Florida Martin County ( es, Condado de Martín, link=) is a county located in the Treasure Coast region of the state of Florida, in the United States. As of the 2020 census, the population was 158,431. Its county seat is Stuart. Martin County is in t ...

, in 1999 and had spread to the

Indian River Lagoon The Indian River Lagoon is a grouping of three lagoons: the Mosquito Lagoon, the Banana River, and the Indian River, on the Atlantic Coast of Florida; one of the most biodiverse estuaries in the Northern Hemisphere and is home to more than 4,300 ...

by 2003. It was found at Great Barrier Island in New Zealand in 2021. It is considered an

in the United States,

(in the Caribbean) and New Zealand.

Ecology

It is probable that sexual reproduction in this species is similar to other members of the genus. However a much more common means of dispersal involves

asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

, with fragments of the plant breaking off and re-establishing themselves elsewhere. In its native surroundings, this seaweed is kept in check by herbivorous fish but in Florida, few if any fish feed on it and it can flourish on off-shore reefs, reducing

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

. It is intolerant of bright light, growing best in shaded positions, being mostly found in the depth range where there is less light than at the surface. Where the water is

turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...

, it flourishes in shallower habitats.

Invasiveness

In Florida, this seaweed has been dubbed the "killer algae". First recorded in the state in 1999, by 2003 it had shown explosive growth and spread widely, with some near shore reefs in Palm Beach County becoming so overwhelmed that fish and lobsters were no longer present. During hurricanes in 2004, it was scoured from the rocky reefs and disappeared, but over the next few years, it became re-established, once more forming dense stands. It is thought to become so abundant on Florida's coast because of the

sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residenc ...

outflows which result in extra nutrients being present in the water. Such extensive algal cover is likely to kill

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s and other

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

invertebrates, and force more mobile organisms to move elsewhere.

References

{{Taxonbar, from=Q41804864 brachypus Protists described in 1860 Taxa named by William Henry Harvey Chlorophyta species