Invasion History

First Non-native North American Tidal Record: 1966
First Non-native West Coast Tidal Record: 1978
First Non-native East/Gulf Coast Tidal Record: 1966

General Invasion History:

Ulva australis was first described from South Australia in 1854. However, genetic studies support the conclusion that it is synonymous with U. pertusa Kjellmann 1879, described from several locations in Japan. Genetic analyses indicate that the greatest genetic diversity of this alga is in the Northwest Pacific (Japan and South Korea), and that populations in Australia, New Zealand, California, Chile, and Europe were derived by multiple introductions (Hayden and Waaland 2004; Kraft et al. 2010; Couceiro et al. 2011; Kirkendale et al. 2013; Hanyuda et al. 2016). Some records from tropical regions (Malaysia, Philippines, India, Oman, Kenya) (Guiry and Guiry 2016) based on morphology, have not been confirmed by molecular methods, and may be misidentifications (Hanyuda et al. 2016). In North America, U. australis has been collected in British Columbia (Saunders and Kucera 2010; Wolf et al. 2012), Oregon, (Hansen, in Chapman et al. 2011), Southern California (Hayden and Waaland 2004), and Mexico (Aguilar-Rosas et al. 2008). It is likely that many of these introductions occurred long before the plants were identified by molecular methods. Ulva species are numerous, highly variable, and have few morphological features. They also have many features that make them prone to human transport, including the ability to grow unattached and drifting, attaching to or entangling with ships and artificial structures, and growing rapidly in eutrophic areas (Lopez et al. 2007).

North American Invasion History:

Invasion History on the West Coast:

Ulva australis was first collected on the West Coast of North America in 1978, near La Bufadora, Ensenada, Baja California, Mexico, and later identified as herbarium specimens. In 2006, additional specimens were found at four locations in Baja California and identified as U. pertusa (= australis) by molecular methods (Aguilar-Rosas et al. 2008). In 1999, specimens of U. australis were found in Bamfield and Nanaimo, on the east and west sides of Vancouver Island, British Columbia (Saunders and Kucera 2010). Ulva australis was also collected and identified in Coos Bay, Oregon in 2010 (Hansen, in Chapman et al. 2011). Specimens from British Columbia and Southern California all share haplotype H5, found on the Northeastern coast of Honshu, Japan (Hanyuda et al. 2016). Given the cryptic nature of this alga, its present range, actual date of introduction, and vector of introduction are all unknown. Plantings of Pacific Oysters (Crassostrea gigas), ballast water, and hull fouling are all possibilities.

Invasion History on the East Coast:

On the East Coast, Ulva australis is known only from the Great Bay estuary, New Hampshire, but may be more widespread. A herbarium specimen, collected in 1966, was identified as this species. In 2008, U. australis was found at 4 of 11 sites sampled in the estuary, three rocky sites near the mouth of the estuary and one near marshes in the interior (Hofmann et al. 2010). As on the West Coast, this alga could be present and unrecognized in many East Coast estuaries.

Invasion History Elsewhere in the World:

Based on its earliest description, Ulva australis was introduced to Port Adelaide, South Australia before 1854, and is now widespread on the subtropical and temperate coasts of the continent, including Queensland. New South Wales, Victoria, South Australia, and Western Australia (Kraft et al. 2010; Kirkendale et al. 2012). In New Zealand, U. australis is widespread, both at sites with much and little human disturbance (Heesch et al. 2009). The date of introduction is unknown. In both Australia and New Zealand, the most common haplotype (H5) is one found on the Northeastern coast of Honshu, Japan (Hanyuda et al. 2016). This haplotype was also found in U. australis collected from the coast of central Chile (Hanyuda et al. 2016).

In European waters, U. australis was discovered at several scattered locations in the 1990s and early 2000s, often at locations associated with oyster culture. In 1993, it was found in the Delta region of the Netherlands, and in 2002 in the Dutch Wadden Sea (Gittenberger et al. 2010). A specimen was found floating off Brittany in 1994, but was initially misidentified as U. rotundatum (Coat et al. 1998; Shimada et al. 2003; Couceiro et al. 2011). Ulva australis was found in many locations on the Iberian Peninsula, from the Bay of Biscay to Portugal in 2003-2009 (Lopez et al. 2007; Couceiro et al. 2011; Chainho et al. 2015). In 1994, U. australis was found in the Thau Lagoon, on the French Mediterranean coast (Verlaque et al. 2002). Other Mediterranean records are from the Venice Lagoon in 2011 (Wolf et al. 2012) and Malaga, Spain in 2009 (Couceiro et al. 2011).


Green algae of the genus Ulva grow as a single flat blade, two cells thick, often divided into irregular wavy and crinkled lobes with holes in the blades ('Sea Lettuce'), or as a hollow tube (formerly placed in the genus Enteromorpha). Ulva spp. are usually bright green and often trap numerous air/oxygen bubbles. Ulva plants are often irregular and variable in shape, and are easily torn by waves, rocks, and grazers. They are often associated with sites of nutrient discharge and variable salinity. Many species of Ulva are recognized, and their taxonomy and biogeography are still being worked out. Molecular methods are needed for definite identification. For example, four species, including U. australis were identified from the Great Bay estuary, New Hampshire (Hofmann et al. 2010) in a molecular survey, while at least 12 species were found in a survey of the West Coast (Alaska-Mexico, Hayden and Waaland 2004).

General characteristics of Ulva australis include blades divided into 1-7 irregular leaf-like lobes with smooth margins and frequent perforations. The base of the blade is wedge-shaped and thick, with concentric wrinkles around the base. When not free-floating, the plants are attached to a substrate by numerous rhizomes. Plants range from 30 to 235 mm in size (occasionally up to 300 mm) and are dark green to yellow-green in color. Compared to U. lactuca, U. australis appears more irregular, and much more extensively perforated. Reproductive tissue forms a yellowish band on the edge of the blade. This description is based on: Woolcott and King 1999, Verlaque et al. 2002, Aguilar-Rosas et al. 2008, Hofmann et al. 2010, Kraft et al. 2010, and Couceiro et al. 2011.

Ulva australis was described from South Australia in 1854. Genetic studies support the conclusion that it is the senior synonym of U. pertusa Kjellman 1879, described from several locations in Japan (Couceiro et al. 2011; Guiry and Guiry 2016). However, the name U. pertusa is still used in some recent papers (e.g. Hanyuda et al. 2016; Hanyuda et al. 2018). Sauriau et al. (2021) found a variety of haplotyoes in Japan, upporting the synonymyof U., and in introduced populations around the world, suggesting multiple introductions in Europe and aorund the world, by shipping and tranfers of Pacific oysters (Magallana gigas).


Taxonomic Tree

Kingdom:   Plantae
Phylum:   Chlorophycota
Class:   Chlorophyceae
Order:   Ulotrichales
Family:   Ulvaceae
Genus:   Ulva
Species:   australis


Ulva pertusa (Kjellman, 1897)

Potentially Misidentified Species

Ulva compressa
British Columbia to Baja California, New Brunswick to New Hampshire (Guiry and Guiry 2016)

Ulva lactuca
Widespread, East and West coasts (Guiry and Guiry 2016)

Ulva laetevirens
Introduced to New Brunswick and Long Island (Mao et al. 2013

Ulva linza
Widespread, East and West coasts (Guiry and Guiry 2016)

Ulva lobata
Widespread, West Coast (Guiry and Guiry 2016)

Ulva ohnoi
Introduced to Gulf Coast and Atlantic Florida (Melton et al. 2016)

Ulva rigida
Widespread, East and West coasts (Guiry and Guiry 2016)



Algae of the genus Ulva have two reproductive phases, which are morphologically similar, and produce either asexual, diploid zoospores with four flagella, or haploid gametes with two flagella (Bold and Wynne 1978). Spores are produced in a yellowish band around the edge of the thallus. The timing of spawning is variable, ranging from a 14-day to a 6-day cycle. A population in Kyushu, Japan spawns for several days before and after a neap tide (Okuda and Yamasaki 1987). Populations in Mediterranean France were fertile from May through October. Fertile cells in the reproductive band contain up to 32 biflagellated gametes (Verlaque et al. 2002). Ulva plants produce large numbers of propagules, which can swim and remain viable for 2-8 days (Santelices 1990; Lopez et al. 2007). When a pair of gametes unite, the flagellae disintegrate and the zygote secretes an adhesive substance (Bold and Wynne 1978). Under suitable conditions, fronds can grow very rapidly, up to 776% per week (Ohno 1977, cited by Verlaque 2002).

Ulva australis grows in a variety of coastal habitats, over a very wide geographical range, from cold-temperate to subtropical conditions. Occurrences in tropical locations need to be confirmed (Hanyuda et al. 2016; Guiry and Guiry 2016). Under experimental conditions, U. australis grew at 5 to 40 PSU, but optimal growth was at 20 PSU (Choi et al. 2011). Ulva australis is known from open rocky coasts, salt marshes, estuaries with seagrass beds, mudflats, and oyster and mussel-beds (Verlaque et al. 2002; Aguilar-Rosas et al. 2008; Heesch et al. 2009; Yamochi 2013; Zhang et al. 2014). Ulva spp. is eaten by a wide variety of herbivores, although its rapid growth rates can often match grazing rates (Guidone et al. 2015).

Trophic Status:

Primary Producer



General HabitatRockyNone
General HabitatUnstructured BottomNone
General HabitatGrass BedNone
General HabitatMarinas & DocksNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Maximum Temperature (ºC)33Zanolai et al.(2019), 7 day survival
Minimum Salinity (‰)5Lowest tested (Choi et al. 2011)
Maximum Salinity (‰)40Highest tested. Optimum growth at 20 PSU (Choi et al. 2011)
Maximum Length (mm)300Woolcott and King 1999; Verlaque et al. 2003; Aguilar-Rosas et al. 2008; Kraft et al. 2010; Couceiro et al. 2011), more typically 200 mm, Mathieson and Dawson 2017
Broad Temperature RangeNoneCold Temperate-Tropical
Broad Salinity RangeNoneMesohaline-Polyhaline

General Impacts

Specific impacts for U. australis in invaded waters have not been reported. However, blooms of Ulva spp. are widely recognized as signs of eutrophication and often attributed to U. lactuca, without formal identification (e.g. Gosner 1978; Van Patten 2006). In Japanese and Chinese waters, U. australis is responsible for 'green tides' in lagoons, producing bad odors and large die-offs with accumulations of dead algae contributing to the decline of seagrass beds (Zostera japonica) (Choi et al. 2011; Yamochi 2013; Zhang et al. 2014). Web of Science references indicate that U. australis (as U. pertusa) has been extensively studied as food for aquaculture organisms and for absorption of excess nutrients in culture systems.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NA-ET2 Bay of Fundy to Cape Cod 1966 Def Estab
N130 Great Bay 1966 Def Estab
NZ-IV None 2007 Def Estab
NEA-V None 2003 Def Estab
NEA-II None 1993 Def Estab
NWP-4a None 0 Native Estab
NEP-VI Pt. Conception to Southern Baja California 1978 Def Estab
P040 Newport Bay 1999 Def Estab
P030 Mission Bay 1999 Def Estab
P022 _CDA_P022 (San Diego) 1999 Def Estab
NWP-3b None 0 Native Estab
NWP-3a None 0 Native Estab
EAS-III None 0 Native Estab
EAS-VI None 0 Native Estab
EA-III None 0 Native Estab
CIO-II None 0 Native Estab
GA None 0 Native Estab
MED-II None 1994 Def Estab
MED-VII None 2011 Def Estab
NEP-III Alaskan panhandle to N. of Puget Sound 2010 Def Estab
NEP-IV Puget Sound to Northern California 2010 Def Estab
P170 Coos Bay 0 Def Estab
AUS-VII None 1854 Def Estab
AUS-X None 0 Def Estab
NEA-IV None 1994 Def Estab
NZ-V None 0 Def Estab
AUS-XII None 0 Def Estab
AUS-IV None 0 Def Estab
AUS-XVIII None 0 Def Estab
AUS-VIII None 0 Def Estab
AUS-IX None 0 Def Estab
AUS-V None 0 Def Estab
MED-I None 2009 Def Estab
NWP-4b None 0 Native Estab
NZ-VI None 0 Def Estab
SEP-C None 2013 Def Estab
P080 Monterey Bay 2011 Def Estab
P110 Tomales Bay 2011 Def Estab
NEP-V Northern California to Mid Channel Islands 2011 Def Estab
SEP-B None 2013 Def Estab
AUS-VI None 0 Def Estab
MED-VIII None 2015 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Aguilar-Rosas, Luis Ernesto; Pedroche, Francisco Flores; Zertuche-González, José Antonio (2014) [Aquatic Invasive Species in Mexico], Comisión Nacional para el Conocimiento y Uso de la Biodiversidad, <missing place>. Pp. 211-222

Aguilar-Rosas, Raúl; Aguilar-Rosas, Luis E.; Shimada, Satoshi (2008) First record of Ulva pertusa Kjellman (Ulvales, Chlorophyta) in the Pacific Coast of Mexico, Algae 23(3): 201-207

Bold, Harold C.; Wynne, Michael J. (1978) Introduction to the Algae: Structure and Reproduction, Prentice-Hall, Englewood Cliffs, NJ. Pp. <missing location>

Chainho, Paula and 20 additional authors (2015) Non-indigenous species in Portuguese coastal areas, lagoons, estuaries, and islands, Estuarine, Coastal and Shelf Science <missing volume>: <missing location>

Chairi, Hicham; González-Ortegón, Enrique (2022) Additional records of the blue crab Callinectes sapidus Rathbun, 1896 in the Moroccan Sea, Africa, None 11(BioInvasions Re): Published online

Chapman, John W.; Therriault, Thomas; Harris, Leslie; Breitenstein, Ralph (2011) <missing title>, Oregon State University, Hatfield Marine Center, Newport OR. Pp. 48

Choi, Tae Seob; Kang, Eun Ju; Kim, Ju-hyoung; Kim, Kwang Young (2011) Effect of salinity on growth and nutrient uptake of Ulva pertusa (Chlorophyta) from an eelgrass bed, Algae 25(1): 17-26

Cinar, Melih Ertan and 7 authors (2021) Current status (as of end of 2020) of marine alien species in Turkey, PLOS ONE 16: Published online

Coat, G.; Dion, P.; Noailles, M.- C.; De Reviers, B.; Fontaine, J.- M.; Berger-Perrot, Y.; Loiseaux-de Goe, S. (1998) Ulva armoricana (Ulvales, Chlorophyta) from the coasts of Brittany (France). II. Nuclear rDNA ITS sequence analysis, European Journal of Phycology 33: 81-86

Couceiro, Lucia; Cremades, Javier; Barreiro, Rodolfo (2011) Evidence for multiple introductions of the Pacific green alga Ulva australis Areschoug (Ulvales, Chlorophyta) to the Iberian Peninsula, Botanica Marina 54: 391-402

Fernandez-Alvarez, Fernando Angel Machordom, Annie (2012) DNA barcoding reveals a cryptic nemertean invasion in Atlantic and Mediterranean waters, Helgoland Marine Research 67: 599-605

Gittenberger, Adriaan; Rensing, Marjolein; Stegenga, Herre; Hoeksema, Bert (2010) Native and non-native species of hard substrata in the Dutch Wadden Sea, Nederlandse Faunistiche Mededelingen 33: 20-76

Gosner, Kenneth L. (1978) A field guide to the Atlantic seashore., In: (Eds.) . , Boston. Pp. <missing location>

Guidone, Michele; Thornber. Carol S.; Van Alstyne, Kathryn L. (2015) Herbivore impacts on two morphologically similar bloom-forming Ulva species in a eutrophic bay, Hydrobiolgia 753: 175-188

2004-2021 AlgaeBase. National University of Ireland Galway--

Hanyuda, Takeaki; Heesch, Svenja; Nelson, Wendy; Sutherland, Judy ; Arai, Shogo; Boo, Sung Min; Kawai, Hiroshi (2016) Genetic diversity and biogeography of native and introduced populations of Ulva pertusa (Ulvales, Chlorophyta), Phycological Research 64: 102-109

Harris, Courtney E.; K. Vogelbein, Wolfgang (2006) Parasites of Mummichogs, Fundulus heteroclitus, from the York River, Virginia, U.S.A., with a Checklist of Parasites of Atlantic Coast Fundulus spp., Comparative Parasitology 73(1): 72-110

Hayden, Hillary S.; Waaland, J. Robert (2004) A molecular systematic study of Ulva (Ulvaceae, Ulvales) from the northeast Pacific, Phycologia 43(4): 364-382

Heesch, Svenja and 5 authors (2009) Ulva, Umbraulva and Gemina: genetic survey of New Zealand taxa reveals diversity and introduced species, European Journal of Phycology 44(2): 143-154

Hofmann, Laurie C.; Nettleton, Jeremy C.;Neefus, Christopher D.; Mathieson, Arthur C. (2010) Cryptic diversity of Ulva (Ulvales, Chlorophyta) in the Great Bay estuarine system (Atlantic USA): introduced and indigenous distromatic species, European Journal of Phycology 45(3): 230-239

Hughey, Jeffery R. (2013) Noteworthy collection: California, Madroño 60(1): 57-59

ICES Advisory Committee on the Marine Environment (2012) <missing title>, International Council for the Exploration of the Seas, Copenhagen. Pp. <missing location>

Kirkendale, Lisa; Saunders, Gary W.; Winberg, Pia (2013) A molecular survey of Ulva (Chlorophyta) in temperate Australia reveals enhanced levels of cosmopolitanism, Journal of Phycology 49: 69-81

Kraft, Lesleigh G. K.; Kraft, Gerald T.; Waller, Ross F. (2010) Investigations into southern Australian Ulva (Ulvophyceae, Chlorophyta) taxonomy and molecular phylogeny indicate both cosmopolitanism and endemic cryptic species1, Journal of Phycology 46: 1257-1277

Lopez, Sergio Baamonde; Fernandez, Irene Baspino; Lozano , Rodolfo Barreiro; Ugarte, Javier Cremades (2007) Is the cryptic alien seaweed Ulva pertusa (Ulvales, Chlorophyta) widely distributed along European Atlantic coasts?, Botanica Marina 50: 267-274

Mao, Yunxiang; Kim, Jang Kyun; Wilson, Roderick; Yarish, Charles (2014) The appearance of Ulva laetevirens (Ulvophyceae, Chlorophyta) in the northeast Coast of the United States of America, Journal of the Ocean University of China 13: 865-870

Melton, James T. III, Collado-Vides, Ligia; Lopez-Bautista, Juan M. (2016) Molecular identification and nutrient analysis of the green tide species Ulva ohnoi M. Hiraoka & S. Shimada, 2004 (Ulvophyceae, Chlorophyta), a new report and likely nonnative species in the Gulf of Mexico and Atlantic Florida, USA, Aquatic Invasions 11: In press

Okuda, Takeo; Yamasaki, Makoto (1987) Reproduction of ulvaceous algae with special reference to the periodic fruiting to the periodic fruiting IV. fruiting on successive days and growth rate of Ulva pertusa, Journal of the Faculty of Agriculture of Kyushu University 32(1-2): 69-77

Oliveira, Otto M. P. and 24 authors (2016) Census of Cnidaria (Medusozoa) and Ctenophora rom South American marine waters, Zootaxa 4194: 1-256

Park, Sang Rul; Kang, Yun Hee; Lee, Hyuk Je; Koa, Young Wook; Kim, Jeong Ha (2014) The importance of substratum and elevation in recruitment and persistence of ulvoid algal blooms on rocky intertidal shores of the southern Korean coast, Botanica Marina 57(1): 55-66

Rao, Dhana; Webb,Jeremy S.; Holmstrom, Carola; Case,Rebecca; Low,Adrian; Steinberg, Peter; Kjelleberg, Staffan (2007) Low densities of epiphytic bacteria from the marine alga Ulva australis inhibit settlement of fouling organisms, Applied and Environmental Microbiology 73(24): 7844-7852

Ruiz, Gregory M.; Geller, Jonathan (2018) Spatial and temporal analysis of marine invasions in California, Part II: Humboldt Bay, Marina del Re, Port Hueneme, ,and San Francisco Bay, Smithsonian Environmental Research Center & Moss Landing Laboratories, Edgewater MD, Moss Landing CA. Pp. <missing location>

Santelices, Bernabe (1990) Patterns of reproduction dispersal and recruitment in seaweeds., Oceanography and Marine Biology, an Annual Review 28: 177-276

Saunders, Gary W. Kucera, Hana (2010) An evaluation of rbcL, tufA, UPA, LSU and ITS as DNA barcode markers for the marine green macroalgae, Cryptogamie, Algologie 31(4): 487-528

Shimada, Satoshi; Hiraoka,Masanori; Nabata,Shinichi; Iima, Masafumi; Masuda, Michio (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

Tenney, Wilton R.; Woolcott, William S. (1962) First report of the bryozoan, Lophopodella carteri (Hyatt), in Virginia, American Midland Naturalist 68(1): 247-248

Van Patten, Margaret Stewart (2006) <missing title>, Connecticut Sea Grant, Groton. Pp. <missing location>

Verlaque, Marc (2001) Checklist of the macroalgae of Thau Lagoon (Herault, France), a hot spot of marine species introduction in Europe, Oceanologia Acta 24(1): 29-49

Verlaque, Marc; Belsher,Thomas; Deslous-Paoli, Jean Marc (2002) Morphology and reproduction of Asiatic Ulva pertusa (Ulvales, Chlorophyta) in Thau Lagoon (France, Mediterranean Sea), Cryptogamie - Algologie 23(4): 301-310

Wolf, Marion A.; Sciuto, Katia; Andreoli, Carlo; Moro, Isabella (2012) Ulva (Chlorophyta, Ulvales) biodiversity in the north Adriatic Sea (Mediterranean, Italy): Cryptic species and new introductions, Journal of Phycology 48: 1510-1521

Woolcott, Geoffrey W.; King, Robert J. (1999) Ulva and Enteromorpha (Ulvales, Ulvophyceae, Chlorophyta) in Eastern Australia: Comparison of Morphological Features and Analyses of Nuclear rDNA Sequence Data, Australian Systematic Botany 12: 709-725

Yamochi, Susumu (2013) Effects of desiccation and salinity on the outbreak of a green tide of Ulva pertusa in a created salt marsh along the coast of Osaka Bay, Japan, Estuarine, Coastal and Shelf Science 116: 21-28

Zhang, Xiaomei; Zhou, Yi; Liu, Peng; Wang, Feng; Liu, Bingjian; Liu, Xujia; Xu, Qiang; Yang, Hongsheng (2014) Temporal pattern in the bloom-forming macroalgae Chaetomorpha linum and Ulva pertusa in seagrass beds, Swan Lake lagoon, North China, Marine Pollution Bulletin 89: 229-238