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 Port Adelaide, 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, and with U. laetevirens, described from Port Phillip Bay (Hughey et al. 2020).  . 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 (Magallana gigas = Crassostrea gigas), ballast water, and hull fouling are all possibilities.

Invasion History on the East Coast:

On the East Coast, Ulva australis was first collected from the Great Bay estuary, New Hampshire in 1966 (Hofman et al. 2010, as U. pertusa. 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). It was collected in Kouchibigouac National Park, New Brunswick (Kirkendale et al. 2013, as 'U. laetivirens').  It was identified as 'U. laetivirens' in  Holmes Bay, Maine in 2009, Macroalgal Herbarium Consortium 2023; from Little Holly Pond, Stamford, Connecticut, a lagoon of Long Island Sound,  and in Jamaica Bay, Queens, New York (Lamb et al. 2018). One puzzling record, identified by the synonym 'U. laetivirens', is from 'Bay and Harbor of New York', dated 1850 (New York Botanical Garden, via Macroalgal Herbarium Consortium 2023). A DNA sample was taken from this herbarium specimen, but results are unknown.  More extensive DNA sampling would clarify the history of this species on the East Coast.  Ulva australis (identified as the synonym U. laetevirens)  is one component of algal blooms identified as 'green' tides in Jamaica Bay, although the blooms were dominated by the native U. compressa in Jamaica Bay.

 

Invasion History Elsewhere in the World:

Ulva australis was described from Port Adelaide, South Australia in 1854, by J. E. Areshoug.  He described U. laetivirens from Port Phillip, Victoria in the same year.  Kjellmann described U. pertusa from Japan in 1897.  Ulva pertusa and U. australis were both found to be widespread in the Indo=Pacific, while U. aletivirens was known from southern Austrlaia nd Bew Zealand (Kraft et al. 2010; Kirkendale et al. 2013; Guiry and Guiry 2023).  Ulva 'pertusa' was widely considered native to Japan, and introduced to Australia, Japan, and North  America (Hayden and Waaland, 2004; Kraft et al. 2010; Couceiro et al. 2011; Kirkendale et al. 2013; Hanyuda et al. 2016).  Other recorded specimens of introduced Ulva in Europe, (especially in the eastern Mediterranean )and eastern North America were identified as U. laetivirens, based on morphological and genetic observations (Sfiso et al. 2010 Wolf et al. 2012; Mao et al. 2014; Lamb et al. 2018).  DNA sequencing of type material supports the conclusion that Ulva pertusa and U.laetevirens are synonyms of Ulva australis (Hughey et al. 2020)..Given the early discovery and wide distribution of U. australis in Australia, we are presuming a wide Indo-West Pacific distribution, including mch of the Northwest and Southwest Pacific as well as the Indian Ocean (Kirkendale et al. 2013; Hanyuda et al. 2016; (Hughey et a, 2020; Guiry and Guiry 2023); In New Zealand, U. australis is widespread, both at sites with much and little human disturbance (Heesch et al. 2009). 

In European waters, Ulva 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) in Malaga, Spain in 2009 (Couceiro et al. 2011), and as U. laetevirens in Tunisia (Miladi et al. 2018); Greece (Christia et al. 2011); and Israel (Einav 2007, cited by Mao et al. 2014)). Ulva australis has slso been collected from the coast of Chile (Hanyuda et al. 2016;  Melton 2013, cited by Villaseñor-Parada et al. 2018).  Vectors include ballast water, hull fouling, and oyster transplants.


Description

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 Port Adelaide South Australia by J. E.Areshoug 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 haplotypes in Japan, supporting the synonymy of U, australis and U. pertusa and in introduced populations around the world, suggesting multiple introductions in Europe and around the world, by shipping and transfers of Pacific oysters (Magallana gigas).  Another named species, U. laetevirens, identified from Port Philip Bay by Areshoug in 1854 has also been found to be genetically identical to U. australis (Hughey et al. 2020).  These species had been previously treated as separate (Mao et al. 2017; Mathieson and Dawes 2017).


Taxonomy

Taxonomic Tree

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

Synonyms

Ulva pertusa (Kjellman, 1897)
Ulva spathulata (Pappenfuss, 1960)
Ulva laetevirens (Areshoug , 1854)

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 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)

Ecology

General:

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

PrimProd

Habitats

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

Life History

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).


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 Native 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
GAden Gulf of Aden 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 Native Estab
AUS-X None 0 Native Estab
NEA-IV None 1994 Def Estab
NZ-V None 0 Def Estab
AUS-XII None 0 Native Estab
AUS-IV None 0 Native Estab
AUS-XVIII None 0 Native Estab
AUS-VIII None 0 Native Estab
AUS-IX None 0 Native Estab
AUS-V None 0 Native Estab
MED-I None 2009 Def Estab
NWP-4b None 0 Native Estab
NZ-VI None 0 Native 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 Native Estab
MED-VIII None 2015 Def Estab
NA-ET3 Cape Cod to Cape Hatteras 2011 Def Estab
M040 Long Island Sound 2011 Def Estab
B-I None 2015 Def Estab
MED-III None 2014 Def Estab
MED-IV None 2003 Def Estab
MED-V None 2007 Def Estab
N020 Englishman/Machias Bay 2009 Def Estab
NA-S3 None 2013 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude

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