''Caulerpa taxifolia'' is a species of green seaweed, an

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

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 nuclei, making them among the biggest single cells in the world. A species in the Mediterran ...

'', native to tropical waters of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

, and

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

. The species name ''taxifolia'' arises from the resemblance of its leaf-like fronds to those of the yew (''Taxus''). A strain of the species bred for use in aquariums has established non-native populations in waters of the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

, the

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, and Australia. It is one of two species of algae listed in 100 of the World's Worst Invasive Alien Species compiled by the IUCN Invasive Species Specialist Group.

Description

''C. taxifolia'' is light green with stolons (stems) on the sea floor, from which sparsely-branched upright fronds of approximately 20–60 cm in height arise. Algae in the genus ''Caulerpa'' synthesize a mixture of toxins termed caulerpicin, believed to impart a peppery taste to the plants. The effects of the specific toxin synthesized by ''C. taxifolia'', caulerpenyne, have been studied, with extracts from ''C. taxifolia'' being found to negatively affect P-glycoprotein-ATPase in the

sea 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 th ...

''G. cydonium''. Like all members of the genus ''Caulerpa,'' ''C. taxifolia'' consists of a single

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

with many nuclei. The algae has been identified as the largest known

single-celled organism A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms an ...

. Wild-type ''C. taxifolia'' is monoecious.

Use in aquaria

''Caulerpa'' species are commonly used in aquaria for their aesthetic qualities and ability to control the growth of undesired species. ''C. taxifolia'' has been cultivated for use in aquaria in western

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

since the early 1970s. A clone of the alga that was resistant to cold was observed in the tropical aquarium at the Wilhelmina Zoo in Stuttgart and further bred by exposure to chemicals and

ultraviolet light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

. The zoo distributed the strain to other aquaria, including the

Oceanographic Museum of Monaco The Oceanographic Museum (''Musée océanographique'') is a museum of marine sciences in Monaco-Ville, Monaco. This building is part of the Institut océanographique, which is committed to sharing its knowledge of the oceans. History Th ...

. The aquarium strain is morphologically identical to native populations of the species. However, a 2008 study found that a population of the aquarium strain near

Caloundra Caloundra ( ) is a coastal town and the southernmost town in the Sunshine Coast Region in South East Queensland, Australia. Geography Caloundra is north of the Brisbane central business district. Caloundra is accessible from Landsborough ...

, Australia exhibited markedly reduced sexual reproduction, with only male plants present during some reproductive episodes. The aquarium strain can survive out of water for up to 10 days in moist conditions, with 1 cm fragments capable of producing viable plants.

Status as invasive species

Outside its native range, ''C. taxifolia'' is listed as an invasive species. It is one of two algae on the

list of the world's 100 worst invasive species 100 of the World's Worst Invasive Alien Species is a list of invasive species compiled in 2014 by the Global Invasive Species Database, a database of invasive species around the world. The database is run by the Invasive Species Specialist Group ...

compiled by the IUCN Invasive Species Specialist Group. The species is able to thrive in heavily polluted waters, possibly contributing to its spread in the Mediterranean.

Presence in the Mediterranean Sea

The presence of ''C. taxifolia'' in the Mediterranean was first reported in 1984 in an area adjacent to the Oceanographic Museum of Monaco. Alexandre Meinesz, a

marine biologist Marine biology is the scientific study of the biology of marine life, organisms in the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifi ...

, attempted to alert Moroccan and French authorities to the spread of the strain in 1989, but the governments failed to respond to his concerns. The occurrence of the strain is generally believed to be due to an accidental release by the museum, but

Monaco Monaco (; ), officially the Principality of Monaco (french: Principauté de Monaco; Ligurian: ; oc, Principat de Mónegue), is a sovereign city-state and microstate on the French Riviera a few kilometres west of the Italian region of Lig ...

rejected the attribution and instead claimed that the observed algae was a mutant strain of ''C. mexicana''. By 1999, scientists agreed that it was no longer possible to eliminate the presence of ''C. taxifolia'' in the Mediterranean. A study published in 2002 found that beds of ''

Posidonia oceanica ''Posidonia oceanica'', commonly known as Neptune grass or Mediterranean tapeweed, is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free f ...

'' in the Bay of

Menton Menton (; , written ''Menton'' in classical norm or ''Mentan'' in Mistralian norm; it, Mentone ) is a commune in the Alpes-Maritimes department in the Provence-Alpes-Côte d'Azur region on the French Riviera, close to the Italian border. Me ...

were not negatively affected eight years after colonization by ''C. taxifolia''. Other published studies have shown that fish diversity and biomass are equal or greater in Caulerpa meadows than in seagrass beds and that Caulerpa had no effect on composition or richness of fish species. Studies in 1998 and 2001 found that the strain observed in the Mediterranean was genetically identical to aquarium strains, with similarities to an additional population in Australia.

Presence in Australia

A 2007 study found that a native bivalve mollusc species was negatively affected by the presence of ''C. taxifolia'', but that the effect was not necessarily different from that of native seagrass species. A 2010 study indicated that the effect of detritus from ''C. taxifolia'' negatively impacted abundance and species richness.

Presence in California

''C. taxifolia'' was found in waters near

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United State ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

in 2000, where chlorine bleach was used in efforts to eradicate the strain. The strain was declared eradicated from Agua Hedionda Lagoon in 2006. California passed a law in 2001 forbidding the possession, sale, transport, or release of ''Caulerpa taxifolia'' within the state. The Mediterranean clone of ''C. taxifolia'' was listed as a noxious weed in 1999 by the

Animal and Plant Health Inspection Service The Animal and Plant Health Inspection Service (APHIS) is an agency of the United States Department of Agriculture (USDA) based in Riverdale, Maryland responsible for protecting animal health, animal welfare, and plant health. APHIS is the lead ...

, prohibiting interstate sale and transport of the strain without a permit under the Noxious Weed Act and Plant Protection Act.

Other negative effects

''C. taxifolia'' may become entangled in fishing gear and boat propellers.

Control methods

''C. taxifolia'' may be controlled via mechanical removal, poisoning with

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

, or application of

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

. Researchers at the

University of Nice A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

investigated possible use of a species of

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...

, '' Elysia subornata'', as a possible natural control method, but found that it was not suitable for use in the Mediterranean due to cold winter water temperatures and insufficient population density.

Gallery

File:Caulerpa taxifolia - National Museum of Nature and Science, Tokyo - DSC07620.JPG, ''C. taxifolia'' on display at the National Museum of Nature and Science in

Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and List of cities in Japan, largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, ...

, Japan. File:CaulerpaTaxifolia.jpg, A field of ''C. taxifolia'' amongst

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...

File:Lysmata amboinensis on Caulerpa taxifolia.jpg, A Pacific cleaner shrimp (''Lysmata amboinensis'') on top of a ''C. taxifolia'' specimen within a

marine aquarium A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquaria. Fish only tanks ofte ...

References

External links

*
Killer Algae
2001 BBC Documentary
In-depth article on invasions of Caulerpa taxifolia, source as escaped aquarium plant, etc.

from ''Killer Algae'' by Alexandre Meinesz

at the Center for Invasive Species Research
"Deep Sea Invasion"
'' Nova (TV series)'' broadcast April 1, 2003
Species Profile- Caulerpa, Mediterranean Clone (''Caulerpa taxifolia'')
National Invasive Species Information Center,

United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...

. Lists general information and resources for Caulerpa, Mediterranean Clone. {{Taxonbar, from=Q310961 taxifolia Species described in 1817 Algae of India Biota of the Mediterranean Sea Flora of the Indian subcontinent Invasive species Invasive species in the Mediterranean Sea