Undaria pinnatifida (Asian kelp)
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Undaria pinnatifida (Harvey) Suringar, 1873
Preferred Common Name
- Asian kelp
Other Scientific Names
- Alaria pinnatifida Harvey, 1860
- Ulopteryx pinnatifida (Harvey) Kjellman, 1885
International Common Names
- English: kelp; precious sea grass; sea mustard
- Chinese: chun dai cai; qun dai cai
Local Common Names
- Japan: wakame
- Korea, DPR: miyeouk; miyok
Summary of InvasivenessTop of page
U. pinnatifida is an annual kelp native to northeast Asia and Russia. It is the basis of a large aquaculture industry in Japan, Korea and China. Beginning in the 1970s, Undaria expanded into non-native areas, and is now found in Europe, North America, South America and Australasia. It appears that Undaria was spread over long distances primarily by hitchhiking on other aquaculture species (e.g. oysters) or attached as microscopic stages to boat hulls. The ability of microscopic stages to go dormant at high temperatures may allow this species to persist during transport. No other kelp taxa have this trait and there are no other invasive kelps. The ecological impact of Undaria is equivocal since it can be negative in some regions and neutral/positive in others.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Phaeophyta
- Class: Phaeophyceae
- Order: Laminariales
- Family: Alariaceae
- Genus: Undaria
- Species: Undaria pinnatifida
DescriptionTop of page
Sporophytes consist of a pinnately-divided blade with midrib, compressed stipe and fibrous holdfast; the length of the frond is 1 to 2 metres. When mature, undulate and folded sporophylls form on both sides of stipe. There are two forms of the plant, i.e ‘southern’ and ‘northern’. Compared to the southern form the northern has a longer stipe with sporophylls arising from the lower regions with deeply divided blade (after Ohno and Masuoka, 1993). Numerous morphologies have been described throughout both the native and introduced ranges.
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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Mediterranean and Black Sea||Present||Introduced||Boudouresque et al., 1985|
|Pacific, Northeast||Present||Native||Ohno and Matsuoka, 1993|
|Japan||Present||Present based on regional distribution.|
|-Hokkaido||Present||Native||Ohno and Matsuoka, 1993|
|-Honshu||Present||Native||Ohno and Matsuoka, 1993|
|-Kyushu||Present||Native||Ohno and Matsuoka, 1993|
|Korea, DPR||Present||Introduced||Lee and Yoon, 1998|
|Korea, Republic of||Present||Introduced||Lee and Yoon, 1998|
|Mexico||Present||Introduced||Aguilar-Rosas et al., 2004|
|USA||Present||Present based on regional distribution.|
|-California||Present||Introduced||Silva et al., 2002; Thornber et al., 2003|
|Argentina||Present||Introduced||Casas and Piriz, 1996; Casas et al., 2004; Pereyra et al., 2015|
|Belgium||Present||Introduced||Leliaert et al., 2000|
|France||Present||Introduced||Kaas and Perez, 1990; Floc'h et al., 1991; Castric-Fey et al., 1993|
|Italy||Present||Introduced||Cecere et al., 2000; Curiel et al., 2001|
|Russian Federation||Present||Selivanova et al., 2007|
|Spain||Present||Introduced||Salinas et al., 1996; DIAS, 2005|
|UK||Present||Introduced||Fletcher and Manfredi, 1995|
|Australia||Present||Present based on regional distribution.|
|-Tasmania||Present||Introduced||Sanderson, 1990; Valentine and Johnson, 2003; Valentine and Johnson, 2004; DIAS, 2005|
|-Victoria||Present||Introduced||Womersley, 2003; DIAS, 2005|
|New Zealand||Present||Introduced||Hay and Luckens, 1987; Stapleton, 1988; Hay, 1990; Hay and Villouta, 1993; Brown and Lamare, 1994|
History of Introduction and SpreadTop of page
Since 1971, U. pinnatifida has been found along the coasts of France (Castric-Fey et al., 1993), United Kingdom (Fletcher and Manfredi, 1995), New Zealand (Hay, 1990), Italy (Curiel et al., 2001), Spain (Salinas et al., 1996), Australia (Valentine and Johnson, 2004), California (Silva et al., 2002), and Mexico (Aguilar-Rosas et al., 2004); long-distance introductions were likely due to importation of aquaculture oysters from Japan (Ohno and Matsuoka, 1993); local spread of populations post-introduction occurs primarily by fouling of small boat hulls. The most recent discovery of a new introduced population was in Argentina (Casas et al., 2004)
Invasions of U. pinnatifida in California, USA have been studied to better predict when and where it may continue its invasion along the west coast of North America (Thornber et al., 2003). Recruitment of the macroscopic stage occurs following rapid drops in water temperature, although high sporophyte mortality may occur due to grazing. It was also observed that Undaria sporophytes may synchronously release zoospores when disturbed, although it is unknown whether this factor enhances its invasiveness. The dispersal of sporophytes by coastal shipping has been reported in New Zealand (Hay, 1990). Natural dispersal mechanisms have been discussed by Forrest et al. (2000), as well as the genetic signature of the dispersal mechanisms (Voisin et al., 2005).
HabitatTop of page
In its natural range, Undaria grows on rocks from the lowest inter-tidal to sub-tidal zones, to a maximum of 8-10 m depth. The alga is an annual (Saitoh et al., 1999; Yoshikawa et al., 2001; Skriptsova et al., 2004). Young fronds of Undaria appear in late October to early November, they grow rapidly from winter until early spring on the coast of Japan. Their growth is best when the seawater temperature is between 5 and 13°C. Special reproductive blades called sporophylls form at the base of the stipes in late spring or early summer. The discharge of zoospores begins from the sporangia formed on the sporophylls. Zoospores are 9 µm in length, biflagellate and motile. Zoospores germinate on the substratum and grow into dioecious gametophyte generations. Individual gametophytes are either male or female, microscopic, filamentous thalli which grow until the summer water temperature rises to about 25°C. After this, growth stops (dormancy) and does not resume until water temperatures fall below 25°C in the autumn. Gametogenesis occurs and, after fertilization, zygotes develop into the small plumules of the juvenile sporophyte; the plant then matures into the characteristic adult form (after Ohno and Masuoka, 1993). In all known populations, the macroscopic sporophyte phase lasts less than 12 months and is considered to be a true annual, and the macroscopic form disappears every summer to for a population discontinuous in time.
In its introduced range, the ecology of Undaria is similar, and in some regions summer temperatures exceed 25°C as in the native range and result in discontinuous populations (Hay and Villouta, 1993; Castric-Fey et al., 1999a, b; Stuart et al., 1999; Curiel et al., 2004). In cooler regions, however, summer water temperatures are never high enough to induce dormancy of the gametophyte phase and therefore populations have overlapping generations and are continuous in time, although individual sporophytes are still annuals and die within 12 months of recruitment.
Habitat ListTop of page
|Coastal areas||Principal habitat||Harmful (pest or invasive)|
|Coastal areas||Principal habitat||Productive/non-natural|
|Intertidal zone||Principal habitat||Harmful (pest or invasive)|
|Intertidal zone||Principal habitat||Productive/non-natural|
|Inshore marine||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Benthic zone||Principal habitat||Harmful (pest or invasive)|
|Benthic zone||Principal habitat||Productive/non-natural|
Biology and EcologyTop of page
The recent genetic studies of Voisin et al. (2005) indicate different genetic structure of Undaria in its native range vs. its introduced range, which may be due to the different mechanisms of introduction: aquaculture and maritime traffic.
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
Impact SummaryTop of page
|Fisheries / aquaculture||Negative|
Environmental ImpactTop of page
The ecological impact of invasive Undaria is spatially variable, in some locations the introduction of Undaria decreases native species diversity through competition (Valentine and Johnson, 2003, 2004; Hewitt et al., 2005; Farrell and Fletcher, 2006), in other cases Undaria has no impact (likely due to high native diversity), and in a few cases Undaria facilitates native species.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Abundant in its native range
- Highly adaptable to different environments
- Pioneering in disturbed areas
- Highly mobile locally
- Benefits from human association (i.e. it is a human commensal)
- Fast growing
- Has high reproductive potential
- Reproduces asexually
- Has high genetic variability
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Modification of natural benthic communities
- Modification of successional patterns
- Monoculture formation
- Reduced native biodiversity
- Threat to/ loss of native species
- Causes allergic responses
- Competition - monopolizing resources
- Competition - shading
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult/costly to control
ReferencesTop of page
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Casas GN; Piriz ML, 1996. Surveys of Undaria pinnatifida (Laminariales, Phaeophyta) in Golfo Nuevo, Argentina. Hydrobiologia, 327:213-215.
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Curiel D; Bellemo G; Marzocchi M; Scattolin M; Parisi G, 1998. Distribution of introduced Japanese macroalgae Undaria pinnatifida, Sargassum muticum (Phaeophyta) and Antithamnion pectinatum (Rhodophyta) in the Lagoon of Venice. Hydrobiologia, 385:17-22.
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ContributorsTop of page
31/03/05 Original text by:
Masao Ohno, Usa Marine Biological Institute, Kochi University, Japan
13/10/11 Reviewed by:
Michael Graham, Moss Landing Marine Laboratories, California, USA
Usa Marine Biological Institute, Kochi University, Usa-cho, Tosa, Kochi 781-1164, Japan
Distribution MapsTop of page
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