Bugulina stolonifera -

Bugulina stolonifera is native to the Northwest Atlantic ^[2].

First observation in Belgium

In 1976, the first report of B. stolonifera came from the Sluice Dock of Ostend ^{[3, 4]}. Until the late 1990s, the species was misidentified as Bugula avicularia (now Bugulina avicularia) instead of Bugula stolonifera (now Bugulina stolonifera) ^[4]. As a result, the species was (again) observed in 1997 for the first time on a buoy in the Port of Ostend ^[5].

Spreading in Belgium

B. stolonifera is a common species in the Port of Ostend. It can be found attached to ships and other floating objects or on walls of docks and other structures that are continuously submerged. The species is also found, although less common, in the Port of Zeebrugge ^{[5, 6]}. Outside ports, this species is present on groynes in Koksijde ^[4]. Today, the species seems to be less abundant than it was at the turn of the century. This is possibly due to competition for space with new alien species such as Tricellaria inopinata and sea squirt colonies ^[7].

Spreading in neighbouring countries

This bryozoan occurs on both sides of the Atlantic Ocean and the Mediterranean Sea. Around 1960, the species was observed for the first time with certainty in western Europe, more specifically in Great Britain ^[8].

In the Netherlands, as in Belgium, this species has been misidentified in the past; earlier reports of colonies of Bugulina avicularia probably referred to Bugulina stolonifera. Most likely, in 1885, B. stolonifera was already observed in the former Zuiderzee as B. avicularia ^[9]. Because of the lack of confirmation, the first official observation in Europe dates from 1960. The first Dutch reports, under the correct scientific name, date from 1993, from the docks of the port of the Royal Netherlands Institute for Sea Research (NIOZ) in Texel ^[10]. Now, the species is common in the Dutch ports on the North Sea side of the ‘Brouwersdam’ and the channels and enclosed waters of Zeeland ^{[9, 11]}.

In the early 1970s, the species was also reported in France, in an inventory of the Boulonnais ^[12]. Today, the species occurs along the entire (English) Channel and in many ports, including Dunkirk, Boulogne, Calais and Le Havre ^{[5, 13]}. B. stolonifera is also present along the south coast of England, including the Port of Plymouth ^[14].

In more northern regions, B. stolonifera occurs in Helgoland, an island off the German coast ^[15]. Along the Atlantic coast of Spain, the species is present in Galicia ^[16].

Due to the high number of observations in port areas, it is assumed that B. stolonifera was introduced to our region via shipping ^{[10, 17]}. An alternative is an introduction via oyster transport ^[7]. In some cases, their primary introduction and further spread (secondary dispersal) is a combination of both mechanisms. Transport with the ballast water of ships might offer another way of dispersal for this bryozoan. In this case, adults attach themselves to the inside of the ballast tank ^[7].

The success of these bryozoans can be explained by the fact that they tolerate both low and fluctuating salinities and pollution, conditions characteristic of ports ^[4]. In addition, the species is a typical biofouling species. This implies that it can be transported quickly over large distances by attaching to ships ^[5].

B. stolonifera grows on submerged surfaces, ship hulls, floating objects and other structures in ports ^[5].

This species often attaches itself to ships, ports, buoys and other hard substrates along our coasts. The removal of this fauna is very expensive. The hulls of boats are removed from the water and cleaned under high. Afterwards, they are treated with antifouling paint ^[18].

Little is known about the ecological impact of this species. Biodiversity-related impacts are likely to be related to spatial competition ^[7].

B. stolonifera belongs to the moss animals (Bryozoa). Bryozoans live in colonies consisting of a group of individuals – zooids – which are connected. The colony size can vary from ten to millions of individuals. Each zooid has a protective shell or cystid containing the body or polypide. Each individual consists of a bundle of nerves, a muscular system, a stomach with a supply channel and a “crown” of tentacles surrounding the mouth (Figure 1). The polypide can partly leave its shell through an opening in the cystid to feed by using its tentacles. The tentacles contain tiny vibrating cilia that create a water current, causing suspended particles to flow to the mouth ^{[4, 19]}.

B. stolonifera has a bush-like appearance, similar to other Bugulina species. Although B. stolonifera is present throughout the year, the colonies are tallest (up to four centimetres) in summer ^[5]. During this period, larvae are released into the water column. These larvae only have a couple of hours to find and settle on a suitable substrate, otherwise, they die. After the summer, most of the old colonies die. The newly settled colonies grow minimally at first, making them difficult to observe ^{[4, 7]}.

A microscope is required to study bryozoans. The Dutch common name ‘vogelkopmosdiertje’ (Literal English translation: ‘bird head moss animal’) is inspired by the bird-like appearance of the avicularium typical of the Bugulina species. The avicularia are the zooids responsible for the protection of the colony. They are equipped with a lid or operculum with which they can perform a ‘bite movement’. Another characteristic of B. stolonifera is the two rows of zooids on each branch, which may cause confusion with B. avicularia. The latter has branches that are spirally wound around the main axis, which is not the case in B. stolonifera. Furthermore, the avicularia of B. stolonifera are smaller and their zooids have two spines on the outer edge. B. avicularia is also less often found in harbours, and more frequently present in the intertidal or permanently submerged zones ^{[4, 20]}.

[1]          World Register of Marine Species (WoRMS) (2024). Bugulina stolonifera (Ryland, 1960). [http://www.marinespecies.org/aphia.php?p=taxdetails&id=834018] (2024-10-18).

[2]         McCann, L. (2019). Bryozoa (Cheilostomata, Ctenostomata, and Cyclostomata) in Galapagos Island fouling communities. Aquat. Invasions 14(1): 85-131. [https://www.vliz.be/nl/imis?module=ref&refid=396080] 

[3]          Polk, P. (1976). Inventarisatie plankton: fauna en flora, in: Nihoul, J.C.J. et al. Projekt Zee eindverslag: 7. Inventaris van de fauna en flora. Projekt Zee eindverslag = Projet Mer rapport final, 7. Diensten van de Eerste Minister. Programmatie van het Wetenschapsbeleid: Brussel: pp. 233-311. [http://www.vliz.be/en/imis?module=ref&refid=6097]

[4]          De Blauwe, H. (2009). Mosdiertjes van de Zuidelijke bocht van de Noordzee: Determinatiewerk voor België en Nederland. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISBN 978-90-812-9003-6. 445 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=138282]

[5]          Kerckhof, F. (2000). Waarnemingen van de mosdiertjes Cryptosula pallasiana (Moll, 1803), Bugula stolonifera Ryland, 1960 en Bugula neritina (Linnaeus, 1758) nieuw voor de Belgische fauna. De Strandvlo 20(3): 114-126. [www.vliz.be/en/imis?module=ref&refid=19322]

[6]          De Blauwe, H.; Dumoulin, E. (2009). De zeefauna en -flora uit de jachthaven van Zeebrugge, in het bijzonder de fouling-organismen van drijvende pontons. De Strandvlo 29(2): 41-63. [http://www.vliz.be/imis/imis.php?module=ref&refid=139489]

[7]          De Blauwe, H. (2019). Persoonlijke mededeling

[8]          Ryland, J.S. (1960). The Britisch species of Bugula (Polyzoa). Proc. Zool. Soc. Lond. 134: 65-105. [http://www.vliz.be/en/imis?module=ref&refid=120943]

[9]          Faasse, M.; De Blauwe, H. (2004). Faunistisch overzicht van de mariene mosdiertjes van Nederland (Bryozoa: Stenolaemata, Gymnolaemata). Ned. Faunist. Meded. 21: 17-54. [http://www.vliz.be/en/imis?module=ref&refid=72808]

[10]        d'Hondt, J.L.; Cadée, G.C. (1994). Bugula stolonifera nieuw voor Nederland en enkele andere Bryozoën van Texel. Het Zeepaard 54: 33-37. [http://www.vliz.be/en/imis?module=ref&refid=120938]

[11]        Faasse, M. (1998). Vindplaatsen van het mosdiertje Bugula stolonifera, Ryland 1960 in Nederland. Het Zeepaard 58: 48-51. [http://www.vliz.be/en/imis?module=ref&refid=120941]

[12]        Glaçon, R. (1971). Faune et flore du littoral Boulonnais. Editions de l’institut de biologie maritime et régionale de Wimereux. Université des sciences et techniques de Lille: Wimereux. 41 pp. [http://www.vliz.be/en/imis?module=ref&refid=140099]

[13]        Wolff, W.J. (2005). Non-indigenous marine and estuarine species in the Netherlands. Zool. Meded. 79(1): 3-116. [http://www.vliz.be/en/imis?module=ref&refid=101200]

[14]        Ryland, J.S.; Bishop, J.D.D.; De Blauwe, H.; El Nagar, E.; Minchin, D.; Wood, C.A.; Yunnie, A.L.E. (2011). Alien species of Bugula (Bryozoa) along the Atlantic coasts of Europe. Aquat. Invasions 6(1): 17-31. [http://www.vliz.be/en/imis?module=ref&refid=206248]

[15]        Harms, J. (1993). Check list of species (algae, invertebrates and vertebrates) found in the vicinity of the island of Helgoland (North Sea, German Bight): a review of recent records. Helgol. Meeresunters. 47: 1-34. [http://www.vliz.be/en/imis?module=ref&refid=32304]

[16]        Fernández Pulpeiro, E. (1983). Aportaciones al conocimiento de los Briozoos marinos ibericos: Queilostomados = Contribution to the knowledge of Iberian marine Bryozoa. Cah. Biol. Mar. 24(4): 469-487. [http://www.vliz.be/en/imis?module=ref&refid=63648]

[17]        Kerckhof, F.; Haelters, J.; Gollasch, S. (2007). Alien species in the marine and brackish ecosystem: the situation in Belgian waters. Aquat. Invasions 2(3): 243-257. [http://www.vliz.be/en/imis?module=ref&refid=114365]

[18]        Hedgepeth, J.W. (Ed.) (1952). Marine fouling and its prevention. Contributions of the Woods Hole Oceanographic Institution, U.S. Naval Institute: Annapolis, Maryland. ISBN: 978-1124111988. 388 pp. [http://www.vliz.be/en/imis?module=ref&refid=140668]

[19]        Ruppert, E.E.; Barnes, R.D. (1994). Invertebrate zoology. 6th edition. Saunders College Publishing: Orlando. ISBN 0-03-026668-8. 1056 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=9414]

[20]        Ryland, J.S.; Hayward, P.J. (1977). British anascan bryozoans. Cheilostomata: Anasca: keys and notes for the identification of the species. Synopses of the British Fauna, N.S. 10, 10. Academic Press: London. ISBN 0-12-605250-6. 118 pp. [http://www.vliz.be/en/imis?module=ref&refid=29452]

VLIZ Alien Species Consortium (2024). Bugulina stolonifera. Introduced alien species of the Belgian part of the North Sea and adjacent estuaries anno 2024. Flanders Marine Institute (VLIZ). 5 pp.