Invasion HistoryFirst Non-native North American Tidal Record: 1959
First Non-native West Coast Tidal Record: 1959
First Non-native East/Gulf Coast Tidal Record:
General Invasion History:
Watersipora arcuata was first described from San Diego Bay, California, but is apparently introduced in Southern California (Banta 1969). Banta considered that specimens of Watersipora collected in the Galapagos (Hastings 1930, cited by Banta 1969), the Gulf of California (Osburn 1952, Soule 1961, cited by Banta 1969), and Scammon's Lagoon (Soule and Soule 1964), on the Pacific side of Baja California also belonged to this species. The native region of W. arcuata is not clear, although Banta concluded that it was native to the eastern tropical Pacific. It appears to be introduced in Hawaii (in 1998, Carlton and Eldredge, 2009); New Zealand (in 1957, Gordon 1989; Gordon 1992), and Australia (in the 1940s, Allen and Wood 1950, cited by Keough and Ross 1999). Invasion history of this species is complicated by its taxonomic history- several species of Watersipora were lumped under the name W. cucullata (Banta 1969; Gordon 1967; Gordon 1992; Mackie et al. 2006). Ship fouling appears to be the primary mode of introduction, since its larval duration is very brief (Mackie et al. 2006). Observations in California and New Zealand suggest that W. arcuata may be a warm-water species which may be restricted in cooler waters, or else outcompeted by W. subtorquata and Watersipora sp. A (Gordon and Mawatari 1993; Geller et al. 2008).
North American Invasion History:
Invasion History on the West Coast:
Watersipora arcuata was collected in the Gulf of California before 1930, and in Pacific Mexico by the early 1960s (Banta 1969). It was first collected in US waters at the Southwestern Yacht Club Marina, in San Diego Harbor, its type locality (Banta 1969). In the same year, it was found in Oceanside Harbor, Alamitos Bay (Long Beach Marina), Redondo Harbor, and Marina del Rey (Banta 1969). In later sampling, it was found in additional southern California harbors, including Mission Bay (in 2003, de Rivera et al. 2005), Dana Point Harbor, Newport Bay, Huntington Harbor (in 2001, Fairey et al. 2002), Channel Islands Harbor, Port Hueneme (in 2000, Cohen et al. 2002), Ventura West Harbor (in 2003, de Rivera et al. 2005), and Santa Barbara Harbor (Geller et al. 2008). So far, it has not been reported north of Point Conception.
Invasion History in Hawaii:
Watersipora arcuata has been found in several small harbors in the Hawaiian Islands, including Kewalo Basin (in 1998, Coles et al. 1999), Alai Wai and Haleiwa Harbors, in Oahu (in 2001, Mackie et al. 2006) and Kahulului Harbor in Maui (in 2003, Coles et al. 2004; Carlton and Eldredge 2009). Mackie et al. (2006) confirmed the identity of W. arcuata by molecular means based on material from Oahu.
Invasion History Elsewhere in the World:
Watersipora arcuata was collected in New South Wales, Australia in the 1940s (Keough and Ross 1999) and is known from several sites near Sydney: Port Kemble (Moran and Grant 1993, cited by Keough and Ross 1999); Port Hacking (Vail and Wass 1981); Manly and The Spit (in 2001, Mackie et al. 2006). It was first collected in Port Phillip Bay, Victoria in 1973 (Holmes 1982, cited by Keough and Ross 1999), and subsequently found in South Australia, near Adelaide, and Western Australia, near Perth (2001, Mackie et al. 2006). In New Zealand, W. arcuata was first found in Auckland, in Waitemata Harbor in 1957 (Gordon 1967; Gordon and Mawatari 1992), and subsequently found in several other harbors on the North Island and at Nelson on the South Island (Gordon 1967). However, W. arcuata has been replaced by W. subtorquata at many locations. In 2013-2014, established populations of W. arcuata were found in a marina in Santa Margherita Ligure, in northwest Italy, the first record in European waters (Ferrario et al. 2015).
Molecular studies (Cytochrome oxidase 1 nucleotide sequences) of Watersipora arcuata showed great genetic diversity at each location, but relatively little geographical differentiation between populations in Australia, New Zealand, California, and Hawaii, suggesting multiple invasions from different source populations, or perhaps a diverse original population. Reduction in diversity due to founder effects was not seen (Mackie et al. 2006).
Watersipora arcuata is an encrusting bryozoan, but its colonies can become erect and leaf-like, with extensively overlapping calcareous crusts, often with curled edges. This bryozoan forms black crusts with red or orange growing edges. The zooids are roughly elongate or rectangular, and 680-1,110 µm X 290-600 µm in size. The frontal shield is perforated by pseudopores. The orifice is slightly wider than long, and the proximal edge is broad and slightly convex or straight. There are no oral spines, avicularia, or ovicells (description from Gordon and Mawatari 1992).
Watersipora nigra (of authors, not Canu and Bassler , 1930)
Potentially Misidentified Species
This newly identified, undescribed species is morphologically nearly identical to W. subtorquata but distinct at the molecular level (Mackie 2006; Geller et al. 2008; Mackie et al. 2012). So far, it is known only from California and South Korea.
(d'Orbigny, 1852), described from the Aegean Sea. Redescribed and redefined by Ryland et al. (2009). It has been characterized in molecular studies by Mackie et al. (2006) and Mackie et al. (2012).
(d'Orbigny, 1852), described from Brazil, Redescribed and redefined morphologically by Ryland et al. (2009). It has been characterized in molecular studies by Mackie et al. (2006) and Mackie et al. (2012).
Life History- Watersipora arcuata is an encrusting, calcified bryozoan composed of many individual zooids. The zooids feed by extending the ciliated tentacles of the lophophore as a funnel, creating a current, and driving food particles into their mouths. The food is guided along the tentacles and through the pharynx by the cilia. Larger food particles can be moved or captured by flicking or contracting the tentacles. (Barnes 1983). Larvae of W. arcuata are lecithotrophic and have a short planktonic period (less than 1 day, Mackie et al. 2006). Larvae settle on a substrate and metamorphose into the first zooid of a colony, an ancestrula (Barnes 1983).
Ecology- Watersipora arcuata is known from pilings, rocks, floats and ships' hulls (Banta 1969; Gordon and Mawatari 1992).
|General Habitat||Coarse Woody Debris||None|
|General Habitat||Marinas & Docks||None|
|Salinity Range||Polyhaline||18-30 PSU|
|Salinity Range||Euhaline||30-40 PSU|
|Tidal Range||Low Intertidal||None|
Tolerances and Life History Parameters
|Minimum Duration||1||Larval duration (Wisley 1958, cited by Mackie et al. 2006)|
|Maximum Duration||2||Larval duration (Wisley 1958, cited by Mackie et al. 2006)|
|Broad Temperature Range||None||Warm temperate-Subtropical|
|Broad Salinity Range||None||Polyhaline-Euhaline|
General ImpactsEconomic Impacts
Shipping- Watersipora arcuata is notable for its ability to settle on surfaces covered with copper-based antifouling paints, and to survive on fast moving ships (Allen 1953; Banta 1969). It has the potential to reduce the speed of ships and may provide settling surfaces for other organisms.
Competition- Watersipora arcuata 'became one of the dominant intertidal organisms at several locations' in Auckland Harbor, and spread to other harbors, but in the 1980s was largely repressed by W. subtorquata (Gordon and Mawatari 1992).
|'An important fouling species' (Gordon 1989).|
|It 'became one of the dominant intertidal organisms at several locations' in Auckland Harbor, and spread to other harbors, but in the 1980s was largely repressed by W. subtorquata.|
|It is 'now the most abundant shallow-water bryozoan on the New South Wales Coast' (Allen 1953).|
Regional Distribution Map
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|NEP-VI||Pt. Conception to Southern Baja California||1959||Def||Estab|
|P020||San Diego Bay||1967||Def||Estab|
|P023||_CDA_P023 (San Louis Rey-Escondido)||1969||Def||Estab|
|P027||_CDA_P027 (Aliso-San Onofre)||2001||Def||Estab|
|P050||San Pedro Bay||1969||Def||Estab|
|P060||Santa Monica Bay||1969||Def||Estab|
|P065||_CDA_P065 (Santa Barbara Channel)||2007||Def||Estab|
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