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Green sea-fingers (tomentosoides)
Codium fragile subsp. fragile

Last edited: April 8th 2022

Green sea-fingers (tomentosoides) - Codium fragile subsp. fragile

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Short description of Codium fragile subsp. fragile, Green sea-fingers (tomentosoides)

A spongy green seaweed with numerous Y-shaped, branching, cylindrical fronds that have a felt-like texture due to the densely packed hairs that cover them. The thallus (plant) may reach 70 cm high, but in GB it is usually no more than 35 cm. It has a small disc-shaped holdfast formed from many fine filaments. Microscopic examination of the utricles (vesicles that form a palisade-like layer at the surface of the branches) is required to distinguish this species from other common native Codium taxa, including C. tomentosum, C. vermilara, C. adhaerens and C. fragile subsp. atlanticum. In Codium fragile subsp. fragile the utricles frequently have a broad constriction at the middle and a sharply pointed tip (mucron).

Impact summary: Codium fragile subsp. fragile, Green sea-fingers (tomentosoides)

Codium fragile subsp. fragile is considered one of the most invasive macroalgae in Europe, in terms of dispersal capability, probability of establishment, and ecological impact on the receiving community. It is an opportunistic seaweed, rapidly colonising disturbed habitats, for example in areas where other seaweeds have been harvested, and replacing them as a dominant member of the community. Once established this subspecies can inhibit the recruitment of other Codium fragile subsp. fragile is considered one of the most invasive macroalgae in Europe, in terms of dispersal capability, probability of establishment, and ecological impact on the receiving community. It is an opportunistic seaweed, rapidly colonising disturbed habitats, for example in areas where other seaweeds have been harvested, and replacing them as a dominant member of the community. Once established this subspecies can inhibit the recruitment of other habitat-forming algae such as kelps and fucoids. However, in GB it has not yet been reported in nuisance densities. Economic impacts on the aquaculture sector result from it being a fouling nuisance to shellfish beds, smothering mussels and scallops, clogging scallop dredges and interfering with harvesting. Seaweed farming can be also affected via entanglement of plants increasing harvesting costs, competition for space, and costs associated with disposal of large quantities of Codium biomass. It can also be a fouling nuisance on ropes, boats, fishing nets, wharf pilings and jetties.

Habitat summary: Codium fragile subsp. fragile, Green sea-fingers (tomentosoides)

Codium fragile subsp. fragile occurs on rock and coralline algae in pools and on open rock from the mid to lower shore. In shallow subtidal waters it can be found attached to cobbles, in seagrass beds, and on oyster reefs. It also grows on artificial structures such as ropes, seawalls, piers and pontoons. It mainly inhabits protected bays and estuaries but also occurs on semi-exposed shores.

Overview table

Environment Marine
Species status Non-Native
Native range Hokkaido, Honshu, Kyushu, Shikoku
Functional type Algae (macroalgae)
Status in England Non-Native
Status in Scotland Non-Native
Status in Wales Non-Native
Location of first record River Yealm, Devon.
Date of first record 1939

Origin

Native to the NW Pacific in waters around Japan, Korea and China (Silva, 1955; Chavanich et al., 2006).

First Record

The earliest records of Codium fragile subsp. fragile in GB are from County Donegal, N. Ireland in 1845, Ilfracombe, Devon in 1853, and Ronaldsay, Scotland in 1891 (all reported following The earliest records of Codium fragile subsp. fragile in GB are from County Donegal, N. Ireland in 1845, Ilfracombe, Devon in 1853, and Ronaldsay, Scotland in 1891 (all reported following DNA analysis of preserved herbarium specimens) (Provan et al., 2008).

Pathway and Method

The original vector of introduction to GB is unknown. The analysis of preserved herbarium samples has also thrown into question the sequence of introductions throughout Europe (Provan et al., 2008), such that it is now unclear whether the introduction to GB was directly from the native range or, as was previously thought, as a secondary introduction from Europe. Ballast water, ships’ hull fouling, and oyster imports have all been suggested as feasible pathways of introduction to Europe. This seaweed has been found on the hulls of freighters in the NW Atlantic, and its introduction into N. America and New Zealand was probably via hull fouling (Dromgoole, 1975; Carlton & Scanlon, 1985; Chapman, 1998). Subsequently, secondary spread in GB and Europe is highly likely to have occurred with oyster movements (Trowbridge & Todd, 1999). Additional potential vectors include fouling on hulls, fishing nets, and aquaculture equipment (Neil et al., 2006).

Species Status

Worldwide, this seaweed has spread throughout Europe, the Mediterranean Sea, Greenland, the Atlantic and Pacific coasts of North America, Chile, South Africa, Australia and New Zealand (Provan et al., 2008; GBIF, 2021).

Dispersal Mechanisms

This seaweed produces a variety of propagules including vegetative buds, fragments of the thallus and entire dislodged thalli, all of which can be dispersed by surface currents (Chapman, 1998; Watanabe et al., 2009). Furthermore, it releases weakly swimming ‘swarmer’ cells toward the end of the growing season (Watanabe et al., 2009). Thallus fragments are often buoyant due to the presence of trapped oxygen bubbles resulting from photosynthesis, thus facilitating longer dispersal distances (Gagnon et al., 2015). This seaweed produces a variety of propagules including vegetative buds, fragments of the thallus and entire dislodged thalli, all of which can be dispersed by surface currents (Chapman, 1998; Watanabe et al., 2009). Furthermore, it releases weakly swimming ‘swarmer’ cells toward the end of the growing season (Watanabe et al., 2009). Thallus fragments are often buoyant due to the presence of trapped oxygen bubbles resulting from photosynthesis, thus facilitating longer dispersal distances (Gagnon et al., 2015). The different propagules exhibit varying retention rates in the water column, enabling both short and long distance natural dispersal (Blanco et al., 2021). According to Trowbridge (1998), Codium fragile subsp. fragile can disperse up to 70 km per year.

Reproduction

In GB, sexual reproduction has not been reported. Codium fragile subsp. fragile reproduces asexually by parthenogenesis (an unfertilized cell develops into a new individual), and vegetatively (a new plant grows from part of the parent plant) (Trowbridge, 1998). In the parthenogenetic method, weakly swimming, ‘swarmer cells’ (gametes) are released which settle and develop into an adult thallus (Watanabe, et al., 2009), Burrows (1991) reported the production of these parthenogenetic gametes from August to December in GB. Vegetative reproduction occurs by fragmentation (through wave action or grazing), producing fragments which are dispersed then subsequently settle and can reattach to the substrate. Mature plants also produce vegetative buds which detach from the parent plant and are then capable of reattachment and growth. (Chapman, 1998; Watanabe et al., 2009). The highest growth rates occur from February to June (Chapman, 1998). In winter, when subject to cold conditions and storms, the majority of large thalli are lost each year, but can subsequently recruit from perennial holdfasts or spores (Maggs & Kelly, 2007).

Known Predators/Herbivores

The sea slugs Elysia viridis and Placida dendritica, sea urchins, and gastropods such as Littorina littorea, are all known to feed upon Codium fragile subsp. fragile (Trowbridge, 2002; Chavanich et al., 2006; Scheibling et al., 2008).

Resistant Stages

Perennial holdfasts offer some resistance against cold and storm conditions.

Habitat Occupied in GB

This seaweed occurs on rock and coralline algae in pools and on open rock from the mid to lower shore (Chapman, 1998; Maggs & Kelly, 2007). In shallow subtidal waters it can be found attached to cobbles, in seagrass beds, shells, and on oyster reefs (Neil et al., 2006). It also grows on artificial structures such as ropes, seawalls, piers and pontoons (Chavanich et al., 2006). It mainly inhabits protected bays and estuaries but also occurs on semi-exposed shores. It can tolerate temperatures from -5 C to 33 C (Chapman, 1998; Matheson et al., 2014), and salinities of 12 – 40 psu (Hanisak, 1979; Matheson et al., 2014). The thick, optically dense thallus prevents photo-inhibition in full sunlight, enabling it to grow well in exposed rockpools (Arnold & Murray, 1980).

This seaweed occurs throughout the British Isles. It is common in the Scilly Isles, along the south coast of England, west coast of Scotland, Orkney, and throughout N. Ireland. There are also scattered records from Wales, and the east coast of England (Maggs & Kelly, 2007; NBN Atlas, 2021).

Environmental Impact

Codium fragile subsp. fragile is considered one of the most invasive macroalgae in Europe, in terms of dispersal capability, probability of establishment, and ecological impact on the receiving community (Nyberg and Wallentinus, 2005). It is an opportunistic seaweed, rapidly colonising disturbed Codium fragile subsp. fragile is considered one of the most invasive macroalgae in Europe, in terms of dispersal capability, probability of establishment, and ecological impact on the receiving community (Nyberg and Wallentinus, 2005). It is an opportunistic seaweed, rapidly colonising disturbed habitats, for example in areas where other seaweeds have been harvested, and replacing them as a dominant member of the community (Chavanich et al., 2006). Once established Codium fragile subsp. fragile can inhibit the recruitment of other habitat-forming algae such as kelps and fucoids (Armitage & Sjotun, 2017). In Canada, this subspecies has displaced native seaweeds and become the dominant canopy alga in some areas, consequently altering community structure and composition, where conditions permit (Chapman, 1998). In Massachusetts in the US, it has been reported at densities of over 170 plants per sq. metre (Trowbridge, 1995). In Belgium, in the Ostende Spuikom (a brackish water body important for birdlife), Codium fragile subsp. fragile has formed dense, smothering populations on the shellfish banks (VLIZ, 2020). Most significant impacts have occurred where algal diversity in the invaded area is low. In GB algal diversity is high and Codium fragile subsp. fragile has not yet occurred in nuisance densities (Chapman, 1998).

Health and Scoial Impact

This seaweed may cause a nuisance to humans when it accumulates and rots on beaches, producing a foul smell (Fofonoff et al., 2021).

Economic Impact

Where it occurs in high densities, Codium fragile subsp. fragile can be a fouling nuisance to shellfish beds, smothering mussels and scallops, clogging scallop dredges, and interfering with harvesting (Neil et al., 2006). It also fouls boats, fishing nets, wharf pilings and jetties. Economic losses may be incurred through cleaning costs, loss of utility and reduced harvest. In Canada estimated economic loss to the aquaculture industry Where it occurs in high densities, Codium fragile subsp. fragile can be a fouling nuisance to shellfish beds, smothering mussels and scallops, clogging scallop dredges, and interfering with harvesting (Neil et al., 2006). It also fouls boats, fishing nets, wharf pilings and jetties. Economic losses may be incurred through cleaning costs, loss of utility and reduced harvest. In Canada estimated economic loss to the aquaculture industry as a result of the C. fragile subsp. fragile invasion was estimated at over $1.2 million USD per year, mainly affecting the harvesting of lobster, wild and cultivated oysters, and kelps (Colautti et al., 2006). In Chile, it has affected the farming operations of the red alga Gracilaria chilensis, through entanglement of the thalli with the G. chilensis plants, and competition for space, thus increasing labour costs for harvesting, and expenditure on trucks to dispose of tons of rotting unprofitable biomass (Neil et al., 2006).

Identification

Brodie, J., Maggs, C.A. & John, D.M. (2007) Green Seaweeds of Britain and Ireland. British Phycological Society, Dunmurry

Silva, P. C. (1955). The dichotomous species of Codium in Britain. Journal of the Marine Biological Association of the United Kingdom, 34(3), 565-577.

Biology, ecology, spread, vectors

Arnold, K. E., & Murray, S. N. (1980). Relationships between irradiance and photosynthesis for marine benthic green algae (Chlorophyta) of differing morphologies. Journal of Experimental Marine Biology and Ecology, 43(2), 183-192.

Blanco, A., Larrinaga, A. R., Neto, J. M., Troncoso, J., Mendez, G., Domínguez-Lapido, P., ... & Olabarria, C. (2021). Spotting intruders: Species distribution models for managing invasive intertidal macroalgae. Journal of Environmental Management, 281, 111861.

Burrows, E. M., Dixon, P. S., & Irvine, L. M. (1991). Seaweeds of the British Isles: Chlorophyta. Vol. 2. HM Stationery Office. Carlton, J. T., & Scanlon, J. A. (1985). Progression and dispersal of an introduced alga: Codium fragile ssp. tomentosoides (Chlorophyta) on the Atlantic coast of North America. Botanica Marina, 28, 155-165.

Chapman, A. S. (1998). From introduced species to invader: what determines variation in the success of Codium fragile ssp. tomentosoides (Chlorophyta) in the North Atlantic Ocean? Helgolander Meeresuntersuchungen, 52(3), 277-289.

Chavanich, S., Harris, L. G., Je, J. G., & Kang, R. S. (2006). Distribution pattern of the green alga Codium fragile (Suringar) Hariot, 1889 in its native range, Korea. Aquatic Invasions, 1(3), 99-108.

Dromgoole, F. I. (1975). Occurrence of Codium fragile subspecies tomentosoides in New Zealand waters, New Zealand Journal of Marine and Freshwater Research, 9:3, 257-264.

Gagnon, K., Peacock, S. J., Jin, Y., & Lewis, M. A. (2015). Modelling the spread of the invasive alga Codium fragile driven by long-distance dispersal of buoyant propagules. Ecological Modelling, 316, 111-121.

GBIF (2021). Codium fragile subsp. fragile in GBIF Secretariat. GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei Accessed via GBIF.org on 2021-07-13.

Hanisak, M. D. (1979). Growth patterns of Codium fragile ssp. tomentosoides in response to temperature, irradiance, salinity, and nitrogen source. Marine Biology, 50(4), 319-332.

Maggs, C. A., & Kelly, J. (2007) Codium. In Brodie, J., Maggs, C. A., & John, D. M. (eds) Green seaweeds of Britain and Ireland. London: British Phycological Society, pp. 189–201.

NBN Atlas (2021). NBN Atlas occurrence download of Codium fragile fragile (and synonyms). Available at: http://nbnatlas.org. Accessed on 2021-07-14.

Matheson, K., McKenzie, C. H., Sargent, P., Hurley, M., & Wells, T. (2014). Northward expansion of the invasive green algae Arnold, K. E., & Murray, S. N. (1980). Relationships between irradiance and photosynthesis for marine benthic green algae (Chlorophyta) of differing morphologies. Journal of Experimental Marine Biology and Ecology, 43(2), 183-192.

Blanco, A., Larrinaga, A. R., Neto, J. M., Troncoso, J., Mendez, G., Domínguez-Lapido, P., ... & Olabarria, C. (2021). Spotting intruders: Species distribution models for managing invasive intertidal macroalgae. Journal of Environmental Management, 281, 111861.

Burrows, E. M., Dixon, P. S., & Irvine, L. M. (1991). Seaweeds of the British Isles: Chlorophyta. Vol. 2. HM Stationery Office. Carlton, J. T., & Scanlon, J. A. (1985). Progression and dispersal of an introduced alga: Codium fragile ssp. tomentosoides (Chlorophyta) on the Atlantic coast of North America. Botanica Marina, 28, 155-165.

Chapman, A. S. (1998). From introduced species to invader: what determines variation in the success of Codium fragile ssp. tomentosoides (Chlorophyta) in the North Atlantic Ocean? Helgolander Meeresuntersuchungen, 52(3), 277-289.

Chavanich, S., Harris, L. G., Je, J. G., & Kang, R. S. (2006). Distribution pattern of the green alga Codium fragile (Suringar) Hariot, 1889 in its native range, Korea. Aquatic Invasions, 1(3), 99-108.

Dromgoole, F. I. (1975). Occurrence of Codium fragile subspecies tomentosoides in New Zealand waters, New Zealand Journal of Marine and Freshwater Research, 9:3, 257-264.

Gagnon, K., Peacock, S. J., Jin, Y., & Lewis, M. A. (2015). Modelling the spread of the invasive alga Codium fragile driven by long-distance dispersal of buoyant propagules. Ecological Modelling, 316, 111-121.

GBIF (2021). Codium fragile subsp. fragile in GBIF Secretariat. GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei Accessed via GBIF.org on 2021-07-13. Hanisak, M. D. (1979). Growth patterns of Codium fragile ssp. tomentosoides in response to temperature, irradiance, salinity, and nitrogen source. Marine Biology, 50(4), 319-332.

Maggs, C. A., & Kelly, J. (2007) Codium. In Brodie, J., Maggs, C. A., & John, D. M. (eds) Green seaweeds of Britain and Ireland. London: British Phycological Society, pp. 189–201. NBN Atlas (2021).

NBN Atlas occurrence download of Codium fragile fragile (and synonyms). Available at: http://nbnatlas.org. Accessed on 2021-07-14.

Matheson, K., McKenzie, C. H., Sargent, P., Hurley, M., & Wells, T. (2014). Northward expansion of the invasive green algae Codium fragile spp. fragile (Suringar) Hariot, 1889 into coastal waters of Newfoundland, Canada. BioInvasions Records, 3(3), 151-158.

Neill, P. E., Alcalde, O., Faugeron, S., Navarrete, S. A., & Correa, J. A. (2006). Invasion of Codium fragile ssp. tomentosoides in northern Chile: a new threat for Gracilaria farming. Aquaculture, 259(1-4), 202-210.

Provan, J., Booth, D., Todd, N. P., Beatty, G. E., & Maggs, C. A. (2008). Tracking biological invasions in space and time: elucidating the invasive history of the green alga Codium fragile using old DNA. Diversity and distributions, 14(2), 343-354.

Scheibling, R. E., Lyons, D. A., & Sumi, C. B. (2008). Grazing of the invasive alga Codium fragile ssp. tomentosoides by the common periwinkle Littorina littorea: effects of thallus size, age and condition. Journal of Experimental Marine Biology and Ecology, 355(2), 103-113.

Silva, P. C. (1955). The dichotomous species of Codium in Britain. Journal of the Marine Biological Association of the United Kingdom, 34(3), 565-577. Trowbridge, C. D. (1998). Ecology of the green macroalga Codium fragile (Suringar) Hariot 1889: Invasive and noninvasive subspecies. Oceanography and Marine Biology Annual Review 36:1–64. Trowbridge, C. D. (2002). Local elimination of Codium fragile ssp. tomentosoides: indirect evidence of sacoglossan herbivory? Journal of the Marine Biological Association of the United Kingdom, 82(6), 1029-1030.

Trowbridge, C. D., & Todd, C. D. (1999). The familiar is exotic: II. Codium fragile ssp. tomentosoides on Scottish rocky intertidal shores. Botanical Journal of Scotland, 51(2), 161-179.

Watanabe, S., Metaxas, A., & Scheibling, R. E. (2009). Dispersal potential of the invasive green alga Codium fragile ssp. fragile. Journal of Experimental Marine Biology and Ecology, 381(2), 114-125.

Management and impact

Armitage, C. S., & Sjotun, K. (2017). Can an old alien benefit from rising ocean temperatures? An experimental and field study on the growth and local distribution of Codium fragile subsp. fragile (Chlorophyta). Marine Biology, 164(6), 1-20.

Chapman, A. S. (1998). From introduced species to invader: what determines variation in the success of Codium fragile ssp. tomentosoides (Chlorophyta) in the North Atlantic Ocean? Helgolander Meeresuntersuchungen, 52(3), 277-289.

Chavanich, S., Harris, L. G., Je, J-G, & Kang, R-S. (2006). Distribution pattern of the green alga Codium fragile (Suringar) Hariot, 1889 in its native range, Korea. Aquatic Invasions, 1(3), 99-108.

Colautti, R. I., Bailey, S. A., Van Overdijk, C. D., Amundsen, K., Armitage, C. S., & Sjotun, K. (2017). Can an old alien benefit from rising ocean temperatures? An experimental and field study on the growth and local distribution of Codium fragile subsp. fragile (Chlorophyta). Marine Biology, 164(6), 1-20.

Chapman, A. S. (1998). From introduced species to invader: what determines variation in the success of Codium fragile ssp. tomentosoides (Chlorophyta) in the North Atlantic Ocean? Helgolander Meeresuntersuchungen, 52(3), 277-289.

Chavanich, S., Harris, L. G., Je, J-G, & Kang, R-S. (2006). Distribution pattern of the green alga Codium fragile (Suringar) Hariot, 1889 in its native range, Korea. Aquatic Invasions, 1(3), 99-108.

Colautti, R. I., Bailey, S. A., Van Overdijk, C. D., Amundsen, K., & MacIsaac, H. J. (2006). Characterised and projected costs of nonindigenous species in Canada. Biological invasions, 8(1), 45-59.

Fofonoff, P. W., Ruiz, G. M., Steves, B., Simkanin, C., & Carlton, J. T. (2021). Codium fragile ssp. fragile in National Exotic Marine and Estuarine Species Information System. Available at: https://invasions.si.edu/nemesis/species_summary/6897 Accessed on 2021-07-14.

Neil, P. E., Alcalde, O., Faugeron, S., Navarrete, S. A., & Correa, J.A. (2006). Invasion of Codium fragile ssp. tomentosoides in northern Chile: A new threat for Gracilaria farming. Aquaculture, 259, 202-210.

Nyberg, C. D., & Wallentinus, I. (2005). Can species traits be used to predict marine macroalgal introductions? Biological Invasions, 7, 265–279.

Trowbridge, C. D. (1995). Establishment of the green alga Codium fragile ssp. tomentosoides on New Zealand rocky shores: current distribution and invertebrate grazers. Journal of Ecology, 949-965.

Trowbridge, C. D. (2002). Local elimination of Codium fragile ssp. tomentosoides: indirect evidence of sacoglossan herbivory? Journal of the Marine Biological Association of the United Kingdom, 82, 1029-1030.

VLIZ (2020). Alien Species Consortium -Codium fragile subsp. fragile – Vertakt viltwier. Niet-inheemse soorten van het Belgisch deel van de Noordzee en aanpalende estuaria anno 2020. Vlaams Instituut voor de Zee (VLIZ). 6 pp.

General

Fofonoff, P. W., Ruiz, G. M., Steves, B., Simkanin, C., & Carlton, J. T. (2021). Codium fragile ssp. fragile in National Exotic Marine and Estuarine Species Information System. Available at: https://invasions.si.edu/nemesis/species_summary/6897 Accessed on 2021-07-14.

Silva, P.C. (1955) The dichotomous species of Codium in Britain.  Journal of the Marine Biological Association of the United Kingdom, 34, (3), 565-577.

Legislation

Green seafingers, Codium fragile tomentosoides, is listed under Schedule 9 of the Wildlife and Countryside Act 1981. Read more about Non-native species legislation.