| Reële kans op vestiging? |
Ja |
|
| Betrouwbaarheid beoordeling |
Grote mate van zekerheid (meerdere bronnen) |
|
| Vestigingsstatus |
Gevestigd |
|
| Zeldzaamheid |
Algemeen |
|
| Invasiviteit |
Potentieel invasief |
|
| Invasiviteit (toelichting) |
There is debate whether this is an invasive species. The origin might be the North East Atlantic Ocean (Wolff 2005). Some authors (for instance Hayward & Ryland 1995) consider the American M. manhattensis a different species from the European one, the latter being named either Molgula tubifera (Örstedt 1844) or Molgula socialis Alder, 1863. In that case M. manhattensis is to be excluded as European invasive species. Wolff (2005) followed Monniot (1969) who did not find differences. Recent genetic research in Belgium revealed that at least the species living in Zeebrugge is the 'real' M. manhattensis. In the Dutch Wadden Sea however, both M. manhattensis and M. socialis were recorded (Gittenberger et al. 2009). The data in this sheet are of te 'European M. manhattensis'. There are several factors for its invasiveness. It is a fast growing, highly adaptable species. It lives in a great number of marine and brackish water habitats. It is hermafroditic and capable of self-fertilization, it is euryhaline, tolerates lower and higher temperatures and is not limited by them in dispersion, it is tolerant of eutrophication and industrial pollution (Cohen & Carlton 1995, VLIZ 2011). [N.B.: The description of an Ascidian by Baster (1762) is considered by some to be of M manhattensis, making the earliest record 1762 (see: Wolff 2005). |
|
| Type introductie |
Niet opzettelijk |
|
| Jaar van eerste melding |
1934 |
|
| Natuurlijke verspreiding |
Noord-Amerika |
|
Noordelijke Atlantische Oceaan |
|
| Verspreiding in Nederland |
Friesland |
|
Groningen |
|
Noord-Holland |
|
Zuid-Holland |
|
Zeeland |
|
| Verspreiding in Nederland (toelichting) |
This species may have lived in the Netherlands since at least 1762. Apart from this, the earliest records are probably those from 1922 from the former Zuiderzee (Sluiter in Redeke et al. 1922) where it was rather common. In 1956 the species was considered common and locally even abundant, in the Wadden Sea and in the provice of Zeeland. This is still the case, although it probably reflects at least 2 species (M. manhattensis and M. socialis, the latter may be indiginous to the Northern Atlantic). |
|
| Habitats |
Mariene habitats |
|
Estuaria en brakwatergebieden |
|
| Wijze van introductie |
Aquacultuur |
|
Aangroei op scheepsrompen |
|
Onderling verbonden waterwegen/bassins/zeeën |
|
| Impact |
Concurrentie |
|
| Ecologische impact (toelichting) |
M. manhattensis is at least a competitor for space. It grows on hard substrates, but also on sand. It might also change the habitat, foulling other species and limit them in coverage and growth. In the Netherlands there are no specific data of negative impact on the ecosystem, but there are some - compettition - in Belgium (Leloup & Polk 1967). |
|
| Economische impact (toelichting) |
This may be a fouling species on bivalves like oysters and mussels, limitting them in coverage and thus it is responsible for a lower growth rate, in the wild as well as in aquacultures. It is a fouling species on hulls of ships and other solid structures. In the Netherlands however, there are as yet no specific data of negative economic impact. |
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