''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. It is a diverse group of mostly marine macroalgae. Characteristics The thallus is filamentous, highly branch ...

'' family. It was first described in 1860 by the Irish botanist

William Henry Harvey William Henry Harvey, FRS FLS (5 February 1811 – 15 May 1866) was an Irish botanist and phycologist who specialised in algae. Biography Harvey was born at Summerville near Limerick, Ireland, in 1811, the youngest of 11 children. His father ...

, having been collected during the

North Pacific Exploring and Surveying Expedition The North Pacific Exploring and Surveying Expedition, also known as the Rodgers-Ringgold Expedition was a United States scientific and exploring project from 1853 to 1856. Commander Cadwalader Ringgold (1802–1867) led the expedition until ...

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 is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

in the United States,

Martinique Martinique ( ; or ; Kalinago language, Kalinago: or ) is an island in the Lesser Antilles of the West Indies, in the eastern Caribbean Sea. It was previously known as Iguanacaera which translates to iguana island in Carib language, Kariʼn ...

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, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...

which sends up blade-like fronds on short

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be un ...

s at intervals. These

thalli Thallus (: 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. A thallus usually names the entir ...

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 ''Caulerpa'' is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many cell nucleus, nuclei, making them among the biggest single cells in the world. Referring to ...

'', 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, sparsely populated regions of Western Australia, region in the north of Western Australia. It is known for its Indigenous Australians, Aboriginal people; wealth disparity; its ancient landscapes; the prevailing r ...

region between

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

and

Port Hedland A port is a maritime law, maritime facility comprising one or more wharves or loading areas, where ships load and discharge Affreightment, cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inla ...

. It was first detected in the United States, in

Martin County, Florida Martin County is a County (United States), county located in the southeastern part of the U.S. state, state of Florida, in the United States. As of the 2020 United States census, 2020 census, the population was 158,431. Its county seat is Stua ...

, 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, ...

by 2003. It was found at

Great Barrier Island Great Barrier Island () lies in the outer Hauraki Gulf, New Zealand, north-east of central Auckland. With an area of it is the sixth-largest List of islands of New Zealand, island of New Zealand. Its highest point, Mount Hobson, Great Barrier ...

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 f ...

, with fragments of the plant breaking off and re-establishing themselves elsewhere. In its native surroundings, this seaweed is kept in check by

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

fish but in Florida, few if any fish feed on it and it can flourish on off-shore reefs, reducing

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

. 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 both water clarity and wate ...

, 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 Palm Beach County is a county in the southeastern part of Florida, located in the Miami metropolitan area. It is Florida's third-most populous county after Miami-Dade County and Broward County and the 24th-most populous in the United States, wi ...

becoming so overwhelmed that fish and lobsters were no longer present. During

hurricanes A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...

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 sewerage, sewer system. Sewage consists of wastewater discharged fro ...

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

coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...

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