| Reële kans op vestiging? |
Ja |
|
| Betrouwbaarheid beoordeling |
Grote mate van zekerheid (meerdere bronnen) |
|
| Vestigingsstatus |
Gevestigd |
|
| Zeldzaamheid |
Lokaal |
|
| Invasiviteit |
Potentieel invasief |
|
| Invasiviteit (toelichting) |
The origin of G. franciscana is unknown (cryptogenic). It was first collected and described from California in 1901. It has a discontinuous global distribution and occurs in Europe, the Black and Azov Seas, West Africa, India, Australia, California, Atlantic coast of North America, Gulf of Mexico, Panama, and South America (Fofonoff 2003). There are several factors for its invasiveness. It is a fast growing, adaptable species, which grows in a wide range of estuarine environments. It has a broad salinity range (oligohaline-polyhaline) and lives in marine as well as in in brackish waters (in the Netherlands mainly restricted to the latter). It has a broad temperature range (cold temperate-tropical) and can tolerate temperatures as high as 37.5°C in thermal effluents (Nauman & Cory 1969), but survives - by remaining dormant in the winter - in estuaries in Northern Europe, where temperatures occasionally approach 0°C, (Crowell and Darnell 1955, Calder 1992, Vervoort 1964). Colonies grow slowly, but after fertilization of the eggs produce ciliated non-feeding planula larvae, able to travel with currents and probably in ballastwater of ships. |
|
| Type introductie |
Niet opzettelijk |
|
| Jaar van eerste introductie |
1920 |
|
| Jaar van eerste melding |
1936 |
|
| Natuurlijke verspreiding |
Onbekend |
|
| Verspreiding in Nederland |
Groningen |
|
Noord-Holland |
|
Zuid-Holland |
|
Zeeland |
|
| Verspreiding in Nederland (toelichting) |
The first record of this species in the Netherlands is of 1920, when it was discovered in the former brackish Zuiderzee, before it was converted to a freshwater lake (Wagenaar Hummelinck 1936, Vervoort 1964, Den Hartog 1959). It later became known from several brackish localities, a.o. Hollands Diep, Haringvliet, Lauwersoog, eastern part of the Western Scheldt and - recently - the North Sea Canal-area. Especially in the latter, the species is spreading and locally has become rather abundant. |
|
| Habitats |
Mariene habitats |
|
Estuaria en brakwatergebieden |
|
| Wijze van introductie |
Aangroei op scheepsrompen |
|
Onderling verbonden waterwegen/bassins/zeeën |
|
| Impact |
Concurrentie |
|
| Ecologische impact (toelichting) |
G. franciscana is an abundant and sometimes dominant part of the fouling community in many estuaries and brackish water habitats. Its ecological impacts however, are largely unknown. In general the species is able to compete with and even overgrow many other organisms (Fofonov, 2003) and form rather large 'woods' on the bottom and other (usually solid) substrata. In this way it may alter the ecosystem, but it also provides cover for numerous organisms (amphipods, crabs, fish). The species itself is preyed upon by several species, especially nudibranchs. For instance in the Dutch North Sea Canal Tenellia adspera and Eubranchus rupium (De Bruyne et al. 2013). |
|
| Economische impact (toelichting) |
G. franciscana can be a fouling species in waterpipes of power plants and other industrial water systems and in this way have a negative economic impact (Fofonoff 2002). In the Netherlands especially in the brackish North Sea Canal, where the species is spreading since 2010, G. franciscana might become one of the fouling species. As yet there are no data of a negative economic impact in the Netherlands. |
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