Red ripple bryozoan
Watersipora subatra

Short description of Watersipora subatra, Red ripple bryozoan

A bryozoan forming inflexible encrusting colonies, up to several cm across, of similar 1 mm individuals (zooids) arranged as a continuous sheet, often forming rounded lobes, sometimes with erect portions formed by back-to-back growth. Colonies are bright orange-red, especially at the growing edges, or sometimes dark sepia, blackish or deep purple (usually when growing in intertidal habitats). Individuals are elongate, each with a rounded, blackish spot (the operculum) at the far end.

Impact summary: Watersipora subatra, Red ripple bryozoan

Capable of forming very large colonies that are likely to have a considerable effect on pre-existing sessile communities through space occupancy and overgrowth interactions. This species is copper-tolerant, so the sheet-like growths can form a barrier over copper-based antifouling treatments, allowing less tolerant species to colonize hulls etc. In some localities, it grows extensively on mussel shells, but the potential impact on mussel aquaculture is unknown.

Habitat summary: Watersipora subatra, Red ripple bryozoan

In GB Watersipora subatra has, until recently, predominantly been found attached to solid surfaces in harbours and marinas: pontoon floats, wave screens, pilings, ropes, buoys, hulls, mussels etc. As an early successional species, it is particularly efficient at colonizing the novel habitats provided by artificial structures. However, it is now also frequently being recorded on natural shores, from the lower intertidal and shallow subtidal areas, where it grows on a wide range of substrates including bedrock, boulders, plastic debris, shells, kelps and other seaweeds, and other bryozoans. Elsewhere, it has also been found on offshore structures and offshore natural reefs. It is known to inhabit salinities of 25-37 psu, temperatures of 12-27 C, and depths to 32 m. (Cohen, 2011; Wood et al., 2017; Viola et al., 2018; Zabin et al., 2018; Reverter-Gil & Souto, 2019; Taylor et al., 2020.)

Overview table

Environment	Marine
Species status	Non-Native
Native range
Functional type	Filter-feeder
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	Plymouth
Date of first record	2008

Origin

Although it was originally described from Japan, the native range of Watersipora subatra has not been determined although it probably originates from somewhere in the NW Pacific or the Central Indo-Pacific (JTMD, 2020). Although it was originally described from Japan, the native range of W. subatra has not been determined although it probably originates from somewhere in the NW Pacific or the Central Indo-Pacific (JTMD, 2020).

Species of the genus Watersipora are notoriously difficult to distinguish, so globally specimens have frequently been misassigned (W. subatra most frequently as W. subtorquata), this in conjunction with the recent re-description of several member species, means the biogeography of W. subatra is unclear (Viera et al., 2014).

It is likely that its introduction into GB was as a result of spread from non-native populations in France, possibly via recreational vessels or cross-channel ferries (Bishop et al., 2015b).

First Record

First detected in 2008 in marinas in Plymouth, Devon and Poole, Dorset (Ryland et al., 2009, as Watersipora subtorquata).

Pathway and Method

Introduction into Europe (France) has been attributed to commercial imports of the Pacific oyster, Magallana gigas in the 1960s and 70s. Transport to GB is likely to have been by leisure craft or cross-channel ferries, since the first occurrences were noted in marinas close to ferry ports. The secondary spread within GB may be by recreational vessels, commercial shipping, or drifting seaweeds and plastics. (Ryland et al., 2009; Kuhlenkamp & Kind, 2013; Bishop et al., 2015b; Reverter-Gil & Souto, 2019.)

Species Status

Watersipora subatra is a bryozoan that was first recorded in GB in 2008. It is currently known from the S coast of England between Newlyn and Eastbourne, Milford Haven in Wales, and Stromness in Orkney (Bishop et al., 2015b; Wood et al., 2015; ICES, 2020; NBN Atlas, 2020).

Elsewhere in Europe, it is long established in northern and western France (from c. 1970); was first recorded in Guernsey in 2007; Dublin, Ireland in 2011; Ardglass, N Ireland in 2012; on drifting seaweed at Helgoland, southern North Sea in 2012; and along the Iberian Atlantic coast from the Bay of Biscay to S Portugal (earliest verified record 2004) (Ryland et al., 2009; Kelso & Wyse Jackson, 2012; Kuhlenkamp & Kind, 2013; Porter et al., 2017; Reverter-Gil & Souto, 2019).

Globally, W. subatra is also present in Japan, Indonesia, USA (California), Australia and New Zealand (summarized by Vieira et al., 2014). It is possible that it is much more widely distributed in cool-temperate regions such as the NW Pacific than stated; however, this will require further checking following the recent taxonomic revisions.

Dispersal Mechanisms

The adult phase is sessile, and the non-feeding larvae are brooded prior to release, hence they have only a brief motile phase of less than 24 hours, limiting natural dispersal. However rafting on seaweeds is another potential natural vector, The adult phase is sessile, and the non-feeding larvae are brooded prior to release, hence they have only a brief motile phase of less than 24 hours, limiting natural dispersal. However rafting on seaweeds is another potential natural vector, for example Kuhlenkamp & Kind (2013) reported finding this species on drift Himanthalia, thought to originate from the English Channel over 800 km away. In addition, large foliose colonies have been observed to survive detachment from substrates; these ‘bryoliths’ can roll along the seafloor like tumbleweeds, possibly dispersing living fragments and larvae some distance from their original attachment point (Aiken, 2014).

Anthropogenic dispersal on hulls, with commercial movements of bivalves, and on floating plastic debris are also possible vectors.

Reproduction

Hermaphroditic (and thus potentially capable of self-fertilizing), fertilization is internal, and the embryos are brooded internally. The ciliated larvae are non-feeding, usually settling within a few hours, and always within 24 hours, to metamorphose into the founding zooid of a new colony (Cohen et al., 2011). In Plymouth this species was noted as reproductive from June to December (CW, pers. obs., 2014 & 2016).

Watersipora subatra colonies grow by the zooids at the edge of the colony budding further zooids; but colonies can fragment to form multiple colonies (Cohen, 2011).

Known Predators/Herbivores

Although not strictly by predation, crabs can reduce the abundance of Watersipora subatra by damaging the colonies when foraging for food, particularly during early settlement and growth (Jenkins, 2018).

Resistant Stages

No resistant or resting stage in the life cycle, although a state of apparent dormancy has been noted in colonies in toxic conditions, with subsequent recovery if the environment improves. Regrowth from apparently dead grey-black colony regions sometimes occurs by local production of active orange-red zooids which overgrow the moribund earlier layer (JB & CW, pers. obs).

Habitat Occupied in GB

At present known in GB primarily from harbours and marinas, attached to solid surfaces in shallow water: pontoon floats, wave screens, pilings, ropes, buoys, hulls, mussels etc. However, it is now also frequently being recorded on natural shores, from the lower intertidal and shallow subtidal areas, where it grows on a wide range of substrates including bedrock, boulders, plastic debris, shells, kelp, and other bryozoans. (Bishop et al., 2015a; Wood et al., 2017; Taylor et al., 2020.)

It is presently known only from the S coast of England between Newlyn and Eastbourne, from Milford Haven in S. Wales, and Stromness in Orkney (Bishop et al., 2015b; Wood et al., 2015; ICES, 2020; NBN Atlas, 2020).

Environmental Impact

Capable of forming very large colonies, and likely to have considerable effect on pre-existing sessile communities through space occupancy and overgrowth interactions. Can dominate fouling communities and influence their composition; its presence can modify the taxonomic composition and increase the species richness and diversity of motile animals within epifauna, an effect probably related to increased structural complexity and sediment retention. (Sellheim et al., 2010; Sams & Keough, 2012; Needles & Wendt, 2013.)

Health and Social Impact

None known or anticipated.

Economic Impact

Relatively resistant to copper-based antifouling treatments, and able to settle on the latest ‘slick’ hull coatings, so may enable colonisation of hulls etc. by other, less resistant species, potentially exacerbating general fouling and promoting the spread of other non-natives. Often loosely encrusts mussels, with apparent potential to affect mussel aquaculture. (Floerl et al., 2004; Piola & Johnston, 2006; Culver et al., 2019.)

Identification

Ryland, J. S., De Blauwe, H., Lord, R. & Mackie, J. A. (2009). Recent discoveries of alien Watersipora (Bryozoa) in western Europe, with redescriptions of species. Zootaxa, 2093, 43-59. (W. subatra reported as W. subtorquata.)

Vieira, L.M., Spencer Jones, M., Taylor, P.D. (2014). The identity of the invasive fouling bryozoan Watersipora subtorquata (d’Orbigny) and some other congeneric species. Zootaxa, 3857, 151-182.

Biology, ecology, spread, vectors

Aiken, E. (2014). Underwater tumbleweeds: an exclusive look at an invasive bryozoan (Watersipora subtorquata) in Monterey Harbor. Senior thesis, California State University Monterey Bay.

Bishop, J. D., Wood, C. A., Yunnie, A. L., & Griffiths, C. A. (2015a). Unheralded arrivals: non-native sessile invertebrates in marinas on the English coast. Aquatic Invasions, 10(3).

Bishop, J. D., Wood, C. A., Lévêque, L., Yunnie, A. L., & Viard, F. (2015b). Repeated rapid assessment surveys reveal contrasting trends in occupancy of marinas by non-indigenous species on opposite sides of the western English Channel. Marine Pollution Bulletin, 95(2), 699-706.

Cohen, A. N. (2011). The Exotics Guide: Non-native Marine Species of the North American Pacific Coast. Center for Research on Aquatic Bioinvasions, Richmond, CA, and San Francisco Estuary Institute, Oakland, CA. Available from: http://www.exoticsguide.org/species_pages/w_subtorquata.html [Accessed 2020-08-06].

Floerl, O., Pool, T. K. & Inglis, G. J. (2004). Positive interactions between nonindigenous species facilitate transport by human vectors. Ecological Applications 14, 1724-1736.

Jenkins, M. F. (2018). Indirect food web interactions: sea otter predation linked to invasion success in a marine fouling community. Thesis, Faculty of California Polytechnic State University, San Luis Obispo. Available from: https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=3332&context=theses [Accessed 2020-08-06].

JTMD. (2020). Japanese Tsunami Marine Debris species database. Watersipora subatra. Smithsonian Environmental Research Centre. Available from: https://invasions.si.edu/nemesis/jtmd/SpeciesSummary.jsp?taxon=Watersipora%20subatra . [Accessed 2020-08-06].

ICES. (2020). National Reports of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO): Presented at the 46th meeting of the ICES Working Group on Introductions and Transfers of Marine Organisms, held in Gdynia, Poland from 4 to 6 March 2020. (UK 104-118). (Available from: https://www.ices.dk/community/Documents/Expert%20Groups/WGITMO/ WGITMO%202019%20National%20Reports.pdf [Accessed 2020-08-10].

Kelso, A., Wyse Jackson, P. N. (2012). Invasive bryozoans in Ireland: first record of Watersipora subtorquata (d'Orbigny, 1852) and an extension of the range of Tricellaria inopinata d’Hondt and Occhipinti Ambrogi, 1985. BioInvasions Records, 1, 209-214.

Kuhlenkamp, R. & Kind, B. (2013). Arrival of the invasive Watersipora subtorquata (Bryozoa) at Helgoland (Germany, North Sea) on floating macroalgae (Himanthalia). Marine Biodiversity Records, 6, 6 pp.

NBN Atlas. (2020). NBN Atlas occurrence download of Watersipora subatra at http://nbnatlas.org. [Accessed 2020-08-06].

Porter, J. S., Nunn, J. D., Ryland, J. S., Minchin, D., & Spencer Jones, M. E. (2017). The status of non-native bryozoans on the north coast of Ireland. BioInvasions Records, 6(4), 321-330.

Reverter-Gil, O. & Souto, J. (2019). Watersiporidae (Bryozoa) in Iberian waters: an update on alien and native species. Marine Biodiversity, 49(6), 2735-2752.

Ryland, J. S., De Blauwe, H., Lord, R. & Mackie, J. A. (2009). Recent discoveries of alien Watersipora (Bryozoa) in western Europe, with redescriptions of species. Zootaxa 2093, 43-59.

Taylor, J., Bishop, J. D. D., Wood, C. A. (2020). Mapping Invasive Alien Species in intertidal habitats within Natura 2000 sites in the Solent. Report to EMFF on grant no. ENG_2578. 64 pp.

Vieira, L. M., Spencer Jones, M., Taylor, P. D. (2014). The identity of the invasive fouling bryozoan Watersipora subtorquata (d’Orbigny) and some other congeneric species. Zootaxa, 3857, 151-182

Viola, S. M., Page, H. M., Zaleski, S. F., Miller, R. J., Doheny, B., Dugan, J. E., ... & Schroeter, S. C. (2018). Anthropogenic disturbance facilitates a non‐native species on offshore oil platforms. Journal of Applied Ecology, 55(4), 1583-1593.

Wood, C. A., Bishop, J. D. D., Yunnie, A. L. E. (2015). Plotting the current distribution of NNS in English marinas. Report to Natural England and the Bromley Trust. 37pp. Available from: http://www.thebromleytrust.org.uk/files/NNS2014_public.pdf [Accessed 2020-08-03].

Wood, C. A., Yunnie, A. L. E., Vance, T., Brown, S. (2017). Tamar Estuaries. Marine biosecurity plan 2017-2020. Species guide [online]. Available from: http://www.plymouth-mpa.uk/wp-content/uploads/2018/06/170807-Tamar-Estuary-Non-Native-Species-Guide-FINAL.docx.pdf [Accessed 2020-08-06].

Zabin, C. J., Marraffini, M., Lonhart, S. I., McCann, L., Ceballos, L., King, C., ... & Ruiz, G. M. (2018). Non-native species colonization of highly diverse, wave swept outer coast habitats in Central California. Marine Biology, 165(2), 31.

Management and impact

Culver, C. S., Ginther, S. C., Daft, D., Johnson, L. T., & Brooks, A. J. (2019). An integrated pest management tactic for quagga mussels: site‐specific application of fish biological control agents. North American Journal of Fisheries Management.

Floerl, O., Pool, T. K. &Inglis, G. J. (2004). Positive interactions between nonindigenous species facilitate transport by human vectors. Ecological Applications 14, 1724-1736.

Hopkins, G. A., Forrest, B. M., Piola, R. F., Gardner, J. P. A. (2011). Factors affecting survivorship of defouled communities and the effect of fragmentation on establishment success. Journal of Experimental Marine Biology and Ecology 396, 233-243.

Needles, L. A., Wendt, D. E. (2013). Big changes to a small bay: introduced species and long-term compositional shifts to the fouling community of Morro Bay (CA). Biological Invasions 15, 1231-1251.

McKenzie, L. A., Brooks, R. C., Johnston, E. L. (2012). A widespread contaminant enhances invasion success of a marine invader. Journal of Applied Ecology 49, 767-773.

Piola, R. F., Johnston, E. L. (2006). Differential resistance to extended copper exposure in four introduced bryozoans. Marine Ecology Progress Series 311, 103–114.

Sams, M. A., Keough, M. J. (2012). Contrasting effects of variable species recruitment on marine sessile communities. Ecology 93, 1153-1163.

Sellheim, K., Stachowicz, J. J., Coates, R. C. (2010). Effects of a nonnative habitat-forming species on mobile and sessile epifaunal communities. Marine Ecology Progress Series 398, 69-80.

Viola, S. M., Page, H. M., Zaleski, S. F., Miller, R. J., Doheny, B., Dugan, J. E., ... & Schroeter, S. C. (2018). Anthropogenic disturbance facilitates a non‐native species on offshore oil platforms. Journal of Applied Ecology, 55(4), 1583-1593.

General

Cohen, A. N. (2011). The Exotics Guide: Non-native Marine Species of the North American Pacific Coast. Center for Research on Aquatic Bioinvasions, Richmond, CA, and San Francisco Estuary Institute, Oakland, CA. Available from: http://www.exoticsguide.org/species_pages/w_subtorquata.html [Accessed 2020-08-06].

GISD. (2015). Global Invasive Species Database Species profile Watersipora subtorquata. Available from: http://www.iucngisd.org/gisd/species.php?sc=1384 [Accessed 2020-08-03].

JTMD. (2020). Japanese Tsunami Marine Debris species database. Watersipora subatra. Smithsonian Environmental Research Centre. Available from: https://invasions.si.edu/nemesis/jtmd/SpeciesSummary.jsp?taxon=Watersipora%20subatra [Accessed 2020-08-06].

WoRMS. (2020). Word Register of Marine Species. Available from: http://www.marinespecies.org/aphia.php?p=taxdetails&id=816025 [Accessed 2020-08-10].