- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Water Tolerances
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Social Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Ulva pertusa Kjellman, 1897
International Common Names
- English: sea lettuce
Local Common Names
- Japan: ana-awosa
- Netherlands: zeesla
Summary of InvasivenessTop of page
U. pertusa is a macroscopic green seaweed widely distributed in the Indo-Pacific Ocean. It has delicate but tough glossy bright to dark green blades up to 20 cm long. The blade is rounded when young but becomes lobed and more or less basally perforated when old. U. pertusa is found growing in the lower littoral and upper subtidal zones of a wide variety of habitats: on rocks, in pools, on other marine organisms, or even on man-made substrates. It is an opportunistic species recently introduced in Europe (Atlantic and Mediterranean Sea) and, reputedly, in Pacific North America (Baja California, Mexico). Its introduction is probably attributable mainly to the shellfish translocations.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Chlorophyta
- Class: Chlorophyceae
- Order: Ulvales
- Family: Ulvaceae
- Genus: Ulva
- Species: Ulva pertusa
Notes on Taxonomy and NomenclatureTop of page
Ulva pertusa was originally described from Japan (Kjellman, 1897) and is very similar to the northern species Ulva fenestrata Postels & Ruprecht (1840) described from the Kamchatka Peninsula. The latter species has a more delicate and regularly perforated blade (Nagai, 1940); further investigations are required to confirm these separate taxonomic identities. Ulva spathulata Papenfuss (1960), described from South Australia could also be a taxonomic synonym (see Heesch et al., 2007). A sterile mutant of U. pertusa was described by Migita (1985) in Omura Bay (Japan).
DescriptionTop of page
Thallus forms a distromatic blade, 5–20 (-40) cm long, irregularly orbicular, lobed, thick and tough when small, but oval and more delicate towards the margins when large. Blade bright to dark green, glossy, without marginal teeth, and generally with perforations of variable size and irregular shape. Perforations are present in young individuals, but become larger and more abundant with age and towards the base, where they may be confluent and eventually divide the blade longitudinally and contribute to the spathulate appearance of some thalli. Basal part of the blade cuneate and thick (up to 500 µm), without central cavity and with characteristic concentric wrinkles around the holdfast. The thickness of the blade declines gradually from the base upwards, from 125–200 µm in the rhizoidal zone, through 100–150 µm in the upper basal zone, and 60–80 µm in the medial zone, to only 40–60 µm in the apical and marginal zones. In surface view, cells lack regular ordering or are regularly ordered only in small groups; isodiametric to elongate, with rounded corners, rarely slightly polygonal and between 10–25 x 8-20 µm. Internally, they contain a parietal chloroplast with (1-) 2 (-3) pyrenoids. In transverse section, the cells of the lower zones are markedly larger and clearly oblong, 30–45 x 10-20 µm, often two times higher than broad and with apex rounded, never acuminate. Towards the base, these cells become intermingled with rhizoidal cells, with similar morphology but darker and with prolongations towards the centre of the blade. In the medial zones, cells are larger, 25–30 x 15–20 µm, and somewhat more oblong; while in the apical and marginal zones of the blade they have rounded, squarish or somewhat oblong outline, measuring 20–25 x 15–20 µm, and very narrow intercellular spaces. Fertile individuals show very evident sporangial or gametangial sori appearing as a thick marginal band clearly delimited by its olive green or yellowish color and contains up to 16 tetraflagellate zoospores or 32 biflagelate gametes (Kjellman, 1897; Yabu and Tokida, 1960; Kamiya et al., 1993; Verlaque,et al., 2002; Baamonde et al., 2007; Heesch et al., 2007; Aguilar-Rosas et al., 2008). This species was originally described from Japan (Hakodate, Enoshima and Yokohama).
Plant TypeTop of page
DistributionTop of page
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 10 Jan 2020
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Indonesia||Present||Present based on regional distribution.|
|-Lesser Sunda Islands||Present||Native|
|South Korea||Present, Widespread||Native|
|Sri Lanka||Present||Native||As Ulva fenestrata Postels & Ruprecht (see Jaasund, 1977)|
|Russia||Present||Present based on regional distribution.|
|-Eastern Siberia||Present||Native||Sakhalin Island|
|-Russian Far East||Present||Native|
|Spain||Present, Widespread||Introduced||1990||Widespread in the northwest Iberian Peninsula|
|Mexico||Present||1978||Baja California. Although Aguiar-Rosas et al. (2007) consider U. pertusa as an alien it might be a native species|
|United States||Present||Present based on regional distribution.|
|Australia||Present||Present based on regional distribution.|
|-South Australia||Present||Native||Misidentified as U. rigida and U. spathulata|
|New Zealand||Present, Widespread||Native||One of the most frequent species of Ulva in both Islands|
|Atlantic - Northeast||Present||Introduced|
|Indian Ocean - Eastern||Present||Native|
|Indian Ocean - Western||Present|
|Mediterranean and Black Sea||Present||Introduced||1984||Mediterranean Sea (Thau Lagoon)|
|Pacific - Eastern Central||Present|
|Pacific - Northwest||Present||Native|
|Pacific - Southwest||Present||Native|
|Pacific - Western Central||Present||Native|
History of Introduction and SpreadTop of page
The first reliable record of U. pertusa outside of its native area was in 1984 from Mediterranean Sea (Thau Lagoon, France), where it could have been introduced as early as 1971-1977 along with massive official importations of Japanese oysters from the Pacific (Verlaque, 2001; Verlaque et al., 2002). Later, this species was also reported from the European Atlantic coasts. The oldest individual from these coasts was recollected in 1990 at A Coruña Bay (Galicia, Spain) (Baamonde et al., 2007) followed by other specimens collected in 1994 from French Brittany (Coat et al., 1998, misidentified as Ulva rotundata; see also Shimada et al., 2003 and Hayden and Waaland, 2004); it also occurs in The Netherlands at least since 1995 (Verlaque et al., 2002; Stegenga et al., 2007). The well-known high potential to disperse of Ulva species, the difficulty in species-level identification in the field, and the current patchy distribution are all factors that suggest that the actual range of U. pertusa along European Atlantic shores may even be considerably wider and more continuous (Baamonde et al., 2007). However, U. pertusa was not found in a recent morphological and molecular investigation of distromatic Ulva species from Ireland and southern Britain (Loughnane et al., 2008).
Risk of IntroductionTop of page
U. pertusa is an opportunistic, highly competitive seaweed with high rates of nutrient assimilation and propagule production. Moreover, it tolerates a wide range of environmental conditions. For these reasons, this species has a high potential for further spread to new territories. As a common component of marine fouling, it can be easily introduced, accidentally by this pathway, mainly through marine traffic or careless shellfish translocations for aquaculture purposes.
HabitatTop of page
This species is mainly found growing in the intertidal zone on a wide variety of habitats: on rocks, in pools, or from the lower littoral to the upper subtidal zone as epiphytes on other seaweeds or seagrasses, epizootics on barnacles and shells, or on a great variety of artificial floating or fixed man-made substrates. It also frequents in coastal lagoons. Although it can live in places ranging from sheltered to moderately exposed to wave action, it is a common and dominant species especially under sheltered conditions such as where protected by breakwaters. In Asia (Japan, Korea, Philippines, Indonesia) it is considered one of the most common species growing in the intertidal and subtidal zones (up to 27 m depth; Weber van Bosse, 1913) on rocky localities. As a member of the Ulvales, U. pertusa is an opportunistic species that becomes dominant in habitats well-lit and rich in nutrients. Wave action often frees them; as free-floating, they continue to grow and they are able to form green tides (Shimada et al., 2003; Hiraoka et al., 2004).
Habitat ListTop of page
|Littoral||Mud flats||Secondary/tolerated habitat||Natural|
|Littoral||Mud flats||Secondary/tolerated habitat||Productive/non-natural|
|Littoral||Intertidal zone||Principal habitat||Natural|
|Littoral||Intertidal zone||Principal habitat||Productive/non-natural|
|Marine||Inshore marine||Principal habitat||Natural|
|Marine||Inshore marine||Principal habitat||Productive/non-natural|
|Marine||Benthic zone||Principal habitat||Natural|
|Marine||Benthic zone||Principal habitat||Productive/non-natural|
Biology and EcologyTop of page
Water TolerancesTop of page
|Parameter||Minimum Value||Maximum Value||Typical Value||Status||Life Stage||Notes|
|Salinity (part per thousand)||35||Optimum||17-35 tolerated|
|Water temperature (ºC temperature)||15||Optimum||0-31 tolerated. Survives after 24 h freezing at -15 (Terumoto, 1960)|
Notes on Natural EnemiesTop of page
A high number of species prey upon Ulva species, e.g. gastropod molluscs, crustaceans (hapacticoid copepods, amphipods), echinoderms (sea urchins) and fish. Myrionema strangulans is a microscopic brown algae widespread in temperate seas very common and abundant as epiphyte on Ulva blades. Other than predation and epiphytism, there are no other known natural enemies that could pose a risk to Ulva populations.
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
Economic ImpactTop of page
The economic impact of U. pertusa is more positive than negative as it is used for human and animal consumption (Chapman and Chapman, 1980; Trono, 1999; Alcantara and Noro, 2006) and it can also be employed as environmental biofilter due to its efficiency in removing nitrogenous compounds from seawater (Dongyan et al., 2004; Tarutani et al., 2004).
Environmental ImpactTop of page
Impact on Habitats
Social ImpactTop of page
U. pertusa can be the main component of ‘‘green tides’’ (Sidharthan et al., 2004). However, despite the negative social effects of these blooms (impacts on tourism, shell fishing, etc.), they cannot reasonably be considered a negative social impact of this species in particular but has a negative consequence of eutrophication.
Risk and Impact FactorsTop of page
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Pioneering in disturbed areas
- Tolerant of shade
- Fast growing
- Has high reproductive potential
- Reproduces asexually
- Modification of natural benthic communities
- Competition - monopolizing resources
- Competition - shading
- Rapid growth
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
- Difficult/costly to control
UsesTop of page
Uses ListTop of page
Animal feed, fodder, forage
- Invertebrate food
- Miscellaneous fuels
- Research model
Human food and beverage
- Food additive
- Green manure
DiagnosisTop of page
Apart the careful observations of morphological and cytological characters described previously, the best way to confirm the taxonomic identity of U. pertusa remain the analysis of rbcL and ITS sequence information.
Similarities to Other Species/ConditionsTop of page
Species-level identification in the cosmopolitan genus Ulva is typically difficult due to a combination of few diagnostic morphological and anatomical characters and high intraspecific variability (Bliding, 1968; Hoeksema and van den Hoek, 1983; Koeman, 1985). Also, many of these characters change with age and environmental conditions (Steffensen, 1976; Mshigeni and Kajumulo, 1979; Tanner, 1986). Therefore it is often recommended to use supplementary tools such as molecular techniques (Woolcott and King, 1993; Malta et al., 1999; Shimada et al., 2003). All these reasons suggest U. pertusa to be a cryptic alien that can go unnoticed countless times by misidentification as local species of the genera (Verlaque et al., 2002; Baamonde et al., 2007; Aguilar-Rosas et al., 2008). However, the precise combination of morphological, anatomical, and reproductive characters of U. pertusa, if are carefully considered and observed should allow a readily discrimination from other congeners found in the same area. Macroscopically, the most stable and distinctive feature is the presence of numerous perforations concentrated around the base of the blade, leaving narrow bands of tissue between them that act as wires that attach the blade to the holdfast. These perforations are very different from those found in other likewise perforated species because, in the latter, they usually are more homogeneous, small in size, and usually scattered all over the lamina. Also highly characteristic are the notorious concentric wrinkles at the base of the blade. The wide fertile margin of the blade is very evident in reproductive individuals and the larger number of spores / gametes per cell (16 / 32, respectively) contrast with the (4) 8 / 16 produced by other Ulva species (Yabu and Tokida, 1960). Microscopically, the blade of this species lacks marginal teeth and mostly has cells with two pyrenoids each.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
ReferencesTop of page
Baamonde López S; Baspino Fernández I; Barreiro Lozano R; Cremades Ugarte J, 2007. Is the cryptic alien seaweed Ulva pertusa (Ulvales, Chlorophyta) widely distributed along European Atlantic coasts? Botanica Marina, 50(5/6):267-274. http://www.atypon-link.com/WDG/doi/pdf/10.1515/BOT.2007.030
Carlton JT, 1985. Transoceanic and interoceanic dispersal of coastal marine organisms: the biology of ballast water. Oceanography and Marine Biology. Oceanography and Marine Biology. An Annual Review, 23:313-371.
Coat G; Dion P; Noailles M-C; Reviers Bde; Fontaine J-M; Berger-Perrot Y; Loiseaux-De Goër S, 1998. Ulva armoricana (Ulvales, Chlorophyta) from the coasts of Brittany (France). Nuclear rDNA ITS sequence analysis. European Journal of Phycology, 33(1):81-86.
Coppejans E; Prud'homme Reine WFvan, 1992. The oceanographic Snellius-II Expedition. Botanical results. List of stations and collected plants. Bulletin des Séances de l'Académie Royale des Sciences d'Outre-Mer, 37:153-194.
Dongyan L; Pickering A; Jun S, 2004. Preliminary study on the responses of three marine algae, Ulva pertusa (Chlorophyta), Gelidium amansii (Rhodophyta) and Sargassum enerve (Phaeophyta) to nitrogen source and its availability. Journal of Ocean University of China, 3:75-79.
Floreto EAT; Hirata H; ; So; Yamasaki S, 1993. Effects of temperature, light intensity and source of nitrogen on the growth, total lipid and fatty acid composition of Ulva pertusa Kjellamn (Chlorophyta). Botanica Marina, 36:149-158.
Gruet Y; Héral M; Robert J-M, 1976. [English title not available]. (Premières observations sur l'introduction de la faune associée au naissain d'huîtres japonaises Crassostrea gigas (Thunberg), importé sur la côte atlantique française) Cahiers de Biologie Marine, 17:173-184.
Han Taejun; Han YoungSeok; Kim KwangYoung; Kim JeongHa; Shin HyunWoong; Kain JM; Callow JA; Callow ME, 2003. Influences of light and UV-B on growth and sporulation of the green alga Ulva pertusa Kjellman. Journal of Experimental Marine Biology and Ecology, 290(1):115-131. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T8F-4846S6J-3&_user=10&_handle=W-WA-A-A-AU-MsSAYZW-UUW-AUZWWWCCZV-WUYUWCDZW-AU-U&_fmt=summary&_coverDate=05%2F27%2F2003&_rdoc=7&_orig=browse&_srch=%23toc%235085%232003%23997099998%23420990!&_cdi=5085&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c7ca7561ae64b14b09f0b011705f06b8
Heesch S; Broom JES; Neill KF; Farr TJ; Dalen JL; Nelson WA, 2009. Ulva, Umbraulva and Gemina: genetic survey of New Zealand taxa reveals diversity and introduced species. European Journal of Phycology, 44(2):143-154.
Hewitt CL; Campbell ML; Schaffelke B, 2007. Introductions of seaweeds: accidental transfer pathways and mechanisms. Botanica Marina, 50(5/6):326-337. http://www.atypon-link.com/WDG/doi/pdf/10.1515/BOT.2007.038
Liu JingWen; Dong ShuangLin, 2001. Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta). I. Nitrogen storage under nitrogen enrichment and starvation. Journal of Environmental Sciences, 13(3):318-322.
Loughnane CJ; McIvor LM; Rindi F; Stengel DB; Guiry MD, 2008. Morphology, rbcL phylogeny and distribution of distromatic Ulva (Ulvophyceae, Chlorophyta) in Ireland and Southern Britain. Phycologia, 47(4):416-429.
Malta EJ; Draisma SGA; Kamermans P, 1999. Free-floating Ulva in the southwest Netherlands: species or morphotypes? A morphological, molecular and ecological comparison. European Journal of Phycology, 34:443-454.
Nelson TA; Lee DJ; Smith BC, 2003. Are "green tides" harmful algal blooms? Toxic properties of water-soluble extracts from two bloom-forming macroalgae, Ulva fenestrata and Ulvaria obscura (Ulvophyceae). Journal of Phycology, 39(5):874-879.
Neori A; Chopin T; Troell M; Buschmann AH; Kraemer GP; Halling C; Shpigel M; Yarish C, 2004. Integrated aquaculture: rationale, evolution and state of the art emphasizing seaweed biofiltration in modern mariculture. Aquaculture, 231(1/4):361-391.
Okuda T, 1975. Reproduction of ulvaceous algae with special reference to the periodic fruiting. Fruiting of Ulva pertusa during neap tides in Okayama. Journal of the Faculty of Agriculture, Kyushu University, 19:149-157.
Sawada T, 1972. Periodic fruiting of Ulva pertusa at three localities in Japan. In: Proceedings of the Seventh International Seaweed Symposium, Sapporo, Japan, August 8-12, 1971 [ed. by Nisizawa K] New York, : Wiley, 229-230.
Shimada S; Hiraoka M; Nabata S; Lima M; Masuda M, 2003. Molecular phylogenetic analyses of the Japanese Ulva and Enteromorpha (Ulvales, Ulvophyceae), with special reference to the free-floating Ulva. Phycological Research, 51:99-108.
Sidharthan M; Shin HyunWoung; Joo JH, 2004. Fouling coverage of a green tide alga, Ulva pertusa, on some antifouling test surfaces exposed to Ayagin harbor waters, east coast of South Korea. Journal of Environmental Biology, 25(1):39-43.
Uchida M; Nakata K; Maeda M, 1997. Conversion of Ulva fronds to a hatchery diet for Artemia nauplii utilizing the degrading and attaching abilities of Pseudoalteromonas espejiana. Journal of Applied Phycology, 9(6):541-549.
Uchida M; Numaguchi K, 1996. Formation of protoplasmatic detritus with characteristics favourable as food for secondary animals during microbial decomposition of Ulva pertusa (Chlorophyta) frond. Journal of Marine Biotechnology, 4:200-206.
Verlaque M; Belsher T; Deslous-Paoli JM, 2002. Morphology and reproduction of Asiatic Ulva pertusa (Ulvales, Chlorophyta) in Thau Lagoon (France, Mediterranean Sea). Cryptogamie, Algologie, 23(4):301-310.
Yokohama Y, 1972. Photosynthesis-temperature relationships in several benthic marine algae. In: Proceedings of the Seventh International Seaweed Symposium, Sapporo, August 8-12, 1971 [ed. by Nisizawa K, Arasaki S, Chihara M, Hirose H, Nakamura Y, Tsuchiya Y]: University of Tokyo Press, 286-291.
Yu PengZhan; Li Ning; Liu XiGuang; Zhou GeFei; Zhang QuanBin; Li PengCheng, 2003. Antihyperlipidemic effects of different molecular weight sulphated polysaccharides from Ulva pertusa (Chlorophyta). Pharmacological Research, 48:543-549.
Yu PengZhan; Zhang QuanBin; Li Ning; Xu ZuHong; Wang YanMei; Li Zhi'en, 2003. Polysaccharides from Ulva pertusa (Chlorophyta) and preliminary studies on their antihyperlipidemia activity. Journal of Applied Phycology, 15(1):21-27.
Baamonde López S, Baspino Fernández I, Barreiro Lozano R, Cremades Ugarte J, 2007. Is the cryptic alien seaweed Ulva pertusa (Ulvales, Chlorophyta) widely distributed along European Atlantic coasts? Botanica Marina. 50 (5/6), 267-274. http://www.atypon-link.com/WDG/doi/pdf/10.1515/BOT.2007.030 DOI:10.1515/BOT.2007.030
CABI, Undated. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI
CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
Coat G, Dion P, Noailles M-C, Reviers B de, Fontaine J-M, Berger-Perrot Y, Loiseaux-De Goër S, 1998. Ulva armoricana (Ulvales, Chlorophyta) from the coasts of Brittany (France). Nuclear rDNA ITS sequence analysis. European Journal of Phycology. 33 (1), 81-86.
Coppejans E, Prud'homme van Reine W F, 1992. The oceanographic Snellius-II Expedition. Botanical results. List of stations and collected plants. Bulletin des Séances de l'Académie Royale des Sciences d'Outre-Mer. 153-194.
Han Taejun, Han YoungSeok, Kim KwangYoung, Kim JeongHa, Shin HyunWoong, Kain J M, Callow J A, Callow M E, 2003. Influences of light and UV-B on growth and sporulation of the green alga Ulva pertusa Kjellman. Journal of Experimental Marine Biology and Ecology. 290 (1), 115-131. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T8F-4846S6J-3&_user=10&_handle=W-WA-A-A-AU-MsSAYZW-UUW-AUZWWWCCZV-WUYUWCDZW-AU-U&_fmt=summary&_coverDate=05%2F27%2F2003&_rdoc=7&_orig=browse&_srch=%23toc%235085%232003%23997099998%23420990!&_cdi=5085&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c7ca7561ae64b14b09f0b011705f06b8 DOI:10.1016/S0022-0981(03)00068-6
Heesch S, Broom J E S, Neill K F, Farr T J, Dalen J L, Nelson W A, 2009. Ulva, Umbraulva and Gemina: genetic survey of New Zealand taxa reveals diversity and introduced species. European Journal of Phycology. 44 (2), 143-154.
Shimada S, Hiraoka M, Nabata S, Lima M, Masuda M, 2003. Molecular phylogenetic analyses of the Japanese Ulva and Enteromorpha (Ulvales, Ulvophyceae), with special reference to the free-floating Ulva. Phycological Research. 99-108.
Verlaque M, Belsher T, Deslous-Paoli J M, 2002. Morphology and reproduction of Asiatic Ulva pertusa (Ulvales, Chlorophyta) in Thau Lagoon (France, Mediterranean Sea). Cryptogamie, Algologie. 23 (4), 301-310.
ContributorsTop of page
09/06/09 Original text by:
Javier Cremades Ugarte, Departamento de Biología, Animal, Biología Vegetal y Ecología, Facultad de Ciencias, Universidad de A Coruña, Campus de la Zapateira, Spain
Distribution MapsTop of page
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