Invasion History

First Non-native North American Tidal Record: 2000
First Non-native West Coast Tidal Record: 2000
First Non-native East/Gulf Coast Tidal Record: None

General Invasion History:

Schizoporella variabilis was first described from Rhode Island by Joseph Leidy in 1855.   a warmer waters (Hayward and Ryland 1999; Hayward and McKinney 2002). As an encrusting organism it is readily transported in fouling. In British waters, it occurs sporadically on ships (Hayward and Ryland 1999). Its worldwide range and its occurrences in the Pacific are poorly documented because of confusion with many similar Schizoporella species, and also found in New Jersey.  This speciesnbds from the Gulf of Maine to Cape Hatters (Winston and Hayward 2012).

The identity of the widely introduced Pacific forms of Schizoporella has been uncertain (Judith Winston, pers. comm.). Global morphological and molecular surveys will be required to determine the identity of apparently introduced Schizoporella species. Currently, Smithsonian Environmental Research Center consulting taxonomists (Matthew Dick; Judith Winston) have definitely identified S. variabilis from plates in San Francisco Bay, but not from other West coast localities. (Winsotn and HaywARD 2012).

North American Invasion History:

Invasion History on the West Coast:

he invasion of Schizoporella japonica, identified then as S. unicornis, was widely reported with Puget Sound, in 1927, reaching San Francisco Bay in 1963, with many  reports (Powell 1970; Carlton 1979; Banta 1963, cited by Cohen and Carlton 1995). However, the occurrence of a second species, possibly S. errata in southern California had been suspected (Powell 1979; Carlton 1979; Cohen and Carlton 1995). Taxonomists working with the SERC invasion group (Judith Winston, Matthew Dick) think that one type of Schizoporella in San Francisco Bay matched European type specimens sufficiently well to be identified as S.errata'. "S. errata' was identified from San Francisco Bay, at least as early as 2000 (Ruiz et al. unpublished data). In 2006, unusual spherical, tube-like and foliaceous structures were found on muddy substrates in the Central and South Bays. These structures were, formed of bryozoan colonies cemented with sand and mud (bryoliths). The bryozoans forming these structures were originally identified as S. errata, based on morphology and molecular comparison of cytochrome oxidase subunit I (COI). Further examination of the bryozoans by Linda McCann and Judith Winston have re-identified them as the closely related species S. variabilis from the Northwest Atlantic. This bryozoan was also found in Mission Bay in 2011, Humboldt Bay (2015), and Bodega and/or Tomales Bay (California Department of Fish and Wildlife 2014; Ruiz and Geller 2018; Ruiz and Geller 2021). However, establishment in these bays is uncertain.

Invasion History in Hawaii:

One or more species of Schizoporella have been introduced to the Hawaiian Islands, variously identified as either S. variabilis or S. unicornis. Hawaiian material requires re-examination before names can be applied (Carlton and Eldredge 2009). 

Invasion History Elsewhere in the World:

In the Pacific, Schizoporella variabilis has been found at Pago Pago Harbor, American Samoa (Coles et al. 2003). In New Zealand, it was reported to occur sporadically, first found in Auckland Harbor in 1960, and occurring on the hull of a yacht in the Bay of Islands in 1988 (Gordon and Mawatari 1992), but recently occurring in surveys of several New Zealand harbors (Inglis et al. 2005b). Its date of first occurrence in Australia is unknown, owing to confusion with S. unicornis, but it is known from Sydney Harbor (Piola and Johnston 2006; Glasby et al. 2007), Port Phillip Bay (Hewitt et al. 2004), and Geraldton and Shark Bay, Western Australia (Wyatt et al. 2005;


Schizoporella variabilis is a heavily calcified encrusting bryozoan, sometimes rising as a double layer with knobs or tubular extensions and growing from rigid or flexible surfaces such as worm tubes and algae. The thickness of a colony is dependent upon its age. Many-layered encrustations of 1 cm thick are common. Its color varies from pink, to orange to brick red. The young zooecia are hexagonal, with older ones being quadrilateral or irregularly polygonal. The frontal wall is opaque and covered with circular pits, each containing a round pore. The orifice is roughly semi-circular, with a central U-shaped sinus on the proximal, roughly straight, edge . It is often not centered and is closer to one side of the zooid. The sinus is surrounded by several tab-like condyles. There are single or paired avicularia on the right or left side of the sinus. The zooecia lack spines and the ovicells are globular, with a radiating pattern or pores and a rough textureIts calcification thickens and the pores deepen with later development. The ancestrula is oval, without pores, and with a large, semicircular orifice, surrounded by four pairs of spines (description from: Leidy 1855; Verrill and Smith 1873; Winston and Hayward 2012).

In California, S. variabilis tends to be rather pale, with dark spotty pigment blotches, whereas S. japonica is bright orange in color. The former can also have adventitious, large, frontal avicularia, though they may be rare. Schizoporella variabilis is often rare on panels, but quite abundant in San Francisco Bay as bryoliths (unattached, living colony masses) (Zabin et al. ,2010) whereas S. japonica is very abundant on panels, but has never been seen to form bryoliths (Linda McCann, personal communication 2009)..

Schizoporella variabilis is closely related to the warm-water Mediterranean and East Atlantic S. errata and was formerly identified as this species (Ryland et al. 2014). . However, it differs in shape of the ovicell, and in the shape andnumber of avicularia. Schizoporella variabilis' avicularia have more incurved rostrum and a broader palate. Schizoporella variabilis is associated with colder water than S. errata (Winston and Hayward 2012).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Bryozoa
Class:   Gymnolaemata
Order:   Cheilostomata
Suborder:   Ascophora
Family:   Schizoporellidae
Genus:   Schizoporella
Species:   variabilis


Escharina variabilis (Leidy, 1855)
Hippothoa variabilis (Verrill, 1875)
Schizoporella unicornis (Osburn, 1912)
Schizopodrella unicornis (Osburn, 1932)
Schizoporella varaibilis (Waters, 1878)

Potentially Misidentified Species

Schizoporella floridana
(Osburn, 1914) A Northwest Atlantic form, formerly considered conspecific with S. errata (Hayward and Ryland 1999).

Schizoporella errata
(Waters 1878) Described from Naples, and appears to be native to the Mediterranean, but is now widespread in the world's warmer waters (Hayward and Ryland 1999;

Schizoporella japonica
(Ortmann 1890) A Northwest Pacific species, formerly considered conspecific with S. unicornis (Dick et al. 2005).

Schizoporella pseudoerrata
(Soule, Soule, and Chaney 1995). 'This very similar species, newly described by Soule et al in 2005, is known from California fouling communities, and may be a redescription of a form of a previously described Schizoporella. It is not likely to be a native species.' (James T. Carlton, personal communication, 2013).

Schizoporella unicornis
(Johnston 1874) A northeast Atlantic species, described from England. Its present range is uncertain, due to the presence of related cryptic species, such as S. japonica (Tompsett et al. 2009).



Life History- Schizoporella variabilis is an encrusting, calcified bryozoan composed of many individual zooids. Zooids can reproduce asexually through diviision. Zooids are herrmophroditic, and also reproduce sexually, to produce larvae which are brooded and then released. Larvae of S. errata are lecithotrophic, and have a short planktonic period (less than 1 day, Hayward and Ryland 1999). 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 settle on a substrate and metamorphose into the first zooid of a colony, an ancestrula (Barnes 1983).

Ecology- Schizoporella variabilis is known from eelgrass beds, oyster beds, pilings, shells, rocks,, floats and ship hulls (Verrill and Smith 1873; Ryland 1965; Winston 1986; Hayward and Ryland 1999)..In San Francisco Bay, S. variabilis fomed solid globular, tubular, and foliaceous structures on mudflats (Zabin et al. 201). It is tolerant of brackish water (Verill and Smith 1873, though the lower limit of its tolerance is not known.


Phytoplankton, detritus

Trophic Status:

Suspension Feeder



General HabitatRockyNone
General HabitatCoarse Woody DebrisNone
General HabitatOyster ReefNone
General HabitatMarinas & DocksNone
General HabitatGrass BedNone
General HabitatUnstructured BottomNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Vertical HabitatEpibenthicNone

Life History

Tolerances and Life History Parameters

Maximum Temperature (ºC)26.6Field, US East & West Coast marinas (Lord et al. 2015)
Maximum Salinity (‰)35Typcial marine salinity
Broad Temperature RangeNoneWarm temperate-Tropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Economic Impacts- Schizoporella spp. are common fouling organisms on ship hulls, docks, and other hard surfaces (Woods Hole Oceanographic Institution 1952; Ryland 1965; Hayward and McKinney 2002). Ryland (1971) suggests that the calcareous layers produced by the bryozoans may actually protect pilings and docks from borers.

Ecological Impacts- Schizoporella spp. frequently dominates the fouling community on man-made structures and on rocks, shells, and algae (Ryland 1965; Powell 1970; Sutherland 1981; Hayward and McKinney 2002).

Regional Impacts

NEP-VNorthern California to Mid Channel IslandsEcological ImpactHabitat Change
Schizoporella errata forms bryoliths (large, rounded, mulilaminar, unattached nodules), creating hard reef-like structures, colonized by at least 34 species, 25 of them non-indigenous (Zabin et al. 2010).
P090San Francisco BayEcological ImpactHabitat Change
Schizoporella variabilis, initially identified as S. errata, created a variety of solid structures on mudflats. These were colonized by a wide variety of native, introduced, and cryptogenic invertebtates (Zabin et al. 2010).
CACaliforniaEcological ImpactHabitat Change
Schizoporella errata forms bryoliths (large, rounded, mulilaminar, unattached nodules), creating hard reef-like structures, colonized by at least 34 species, 25 of them non-indigenous (Zabin et al. 2010)., Schizoporella variabilis, initially identified as S. errata, created a variety of solid structures on mudflats. These were colonized by a wide variety of native, introduced, and cryptogenic invertebtates (Zabin et al. 2010).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-V Northern California to Mid Channel Islands 2000 Def Estab
P090 San Francisco Bay 2000 Def Estab
P112 _CDA_P112 (Bodega Bay) 2014 Def Estab
NA-ET3 Cape Cod to Cape Hatteras 1855 Native Estab
P030 Mission Bay 2011 Def Unk
NEP-VI Pt. Conception to Southern Baja California 2011 Def Unk
NEP-IV Puget Sound to Northern California 2015 Def Estab
P130 Humboldt Bay 2015 Def Estab
M020 Narragansett Bay 1855 Native Estab
M076 _CDA_M076 (Great Egg Harbor) 0 Native Estab
M040 Long Island Sound 0 Native Estab
M010 Buzzards Bay 0 Native Unk
M132 _CDA_M132 (Eastern Lower Delmarva) 0 Def Estab
M130 Chesapeake Bay 0 Native Estab
NA-ET2 Bay of Fundy to Cape Cod 1932 Native Estab
N036 _CDA_N036 (Maine Coastal) 1932 Native Estab
N170 Massachusetts Bay 0 Native Estab
N195 _CDA_N195 (Cape Cod) 0 Native Estab
N193 _CDA_N193 (Cape Cod) 0 Prb Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


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Ignacio, Barbara L.; Julio, Luciana M.; Junqueira, Andrea O. R; Ferreira-Silva, Maria A. G. (2010) Bioinvasion in a Brazilian Bay: filling gaps in the knowledge of southwestern Atlantic biota, PLOS ONE 5(9): <missing location>

Inglis, Graeme and 6 authors (2006e) Whangarei Harbour (Whangarei Port and Marsden Point: Baseline survey for non-indigenous species, Biosecurity New Zealand Technical Paper 2005(16): 1-52

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Kaminas, Alexandros; Shokouros-Oskarsson. Maria; Minasidis, Vasileios; Langeneck, Joachim; Kleitou, Periklis; Tiralongo; Crocetta, Fabio (2033) Filling gaps via citizen science: Phyllorhiza punctata von Lendenfeld, 1884 (Cnidaria: Scyphozoa: Mastigiidae) in Cyprus (eastern Mediterranean Sea), Bioinvasion Records 11(In press): In press

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Zabin, Chela J.; Obernolte, Rena; Mackie, Joshua A.; Gentry, Jackson, Harris, Leslie; Geller, Jonathan (2010) A non-native bryozoan creates novel substrate on the mudflats in San Francisco Bay, Marine Ecology Progress Series 412: 129-139