Invasion of the magnificent bryozoan (Pectinatella magnifica) in Finland

Hi everyone!  Below you can find a brief description of my (Katri’s) current postdoc-research project.  I will make new posts about the project as it progress. In short,  I will be studying the invasion patterns of this magnificent bryozoan moss animal  in Finland.

Ecology of Pectinatella magnifica

The magnificent bryozoan (Pectinatella magnifica (Leidy 1851)) is a freshwater bryozoan moss animal belonging to the class Phylactolaemata. This sessile animal forms colonies that attach to various substrates, such as macrophytes, submerged trees and stones, in both lotic and lentic waters (e.g. Choi et al. 2015). The colonies are characterized by a gelatinous matrix, where individual animals (zooids) live as a thin layer on the matrix´s surface (Pennak, 1989). The size of these colonies can range from 10 cm to as big as 200 cm in width, and the fresh weight of the colonies can reach 70 kg (Balounová et al. 2011). Previous studies on the ecology of P. magnifica suggest that the species is able to form colonies in environments with a wide range of environmental parameters, and the colonized water bodies can range from oligotrophic to eutrophic in character (Musil et al. 2018) although more nutrient-rich waters are favored. However, water temperature has further been demonstrated to be one of the important factors that affect the seasonal dynamics of the colonies (Balounová et al. 2011). Also the availability of suitable substrates at a site seems to have its effect on the success of the colonies (Hübschman, 1969, Balounová et al. 2011).

The life cycle of P. magnifica is that of typical for bryozoan species in general. When the conditions are favorable it can reproduce sexually. However, asexual reproduction by simple bulking is also possible and common. P. magnifica also produces resistant statoblasts that enable the species to survive during unfavorable conditions, such as freezing or drought (Wood and Okamura 2005). These statoblasts have hooks around their margins (Ruppert & Barnes 1993). With these hooks, the statoblasts can attach themselves to the plumage of waterbirds and disperse between waterbodies. The statoblast can also be eaten by birds and fish (e.g. Charalambidou et al. 2003). Along with zoochory, P. magnifica can spread through human activities. With the hooks, the statoblast can attach e.g. to ships and fishing equipment (Seo, 1998). For longer distances, the statoblasts can also spread with ships ballasts waters (e.g. Nehring 2005).

p. magnifica_marikasarkkinen
Pectinatella magnifica colony. Photo by Marika Sarkkinen
p. magnifica_kristiinavuorio
Statoblast of P. magnifica. Photo by Kristiina Vuorio


The P. magnifica is native to freshwaters in North America from east of the Mississippi River from Ontario to Florida in USA. However, in the past decade it has expanded its range and has been invading new areas not only in the Northern America but also in many countries in East Asia and Europe with an accelerating rate (e.g. Wood 2010, Vuorio et. al 2018).  This is worrying because the ecological effects of its invasion to new waterbodies are poorly understood.

Ecological effects of Pectinatella magnifica

Although P. magnifica does not pose a direct threat to humans, the mass occurrences of this biofouler can e.g. clog water pipes, filters and drains as well as damage irrigation systems and fishing gear (Nakano & Strayer, 2014). It can also cause aesthetic harm on shores as the decaying colonies have an unpleasant smell (Wood 2010).  Because the species is a filter feeder, it has also been described how the feeding activity of the colonizing zooids can increase the transparency of water by removing small particles from the waterbody. This in turn could have effects on the primary productivity of the waters by changing algal productivity. Also, species´ competitive interactions with other aquatic species for food and space might alter food webs in the ecosystems (Wang et al .2017). The gelatinous matrix of the species has also its interesting properties. The matrix is rich in nutrients and can support different phytoplankton and bacterial communities inside the matrix than outside of it (Šetlíková et al. 2013). So much so, that it has been suggested that the filamentous cyanobacteria living associated with the P. magnifica could bring significant doses of cyanotoxins to (produced by them) environment especially during decomposition of the P. magnifica colonies (Kollar et al. 2016).  Invasion of P. magnifica can further pose a significant risk to local fish populations, as the species can act as a host for the myxozoan endoparasite, Tetracapsuloides bryosalmonae, that cause lethal Proliferative Kidney Disease (PKD) in salmonid fish (Sterud & al. 2007).

Pectinatella magnifica in Finland

In the past, Finnish inland waters has been thought be somewhat “buffered” against invasions by non-indigenous species because of low water temperatures and low nutrient concentrations (Pienimäki and Leppäkoski 2004). However, the situation might change due to climate warming and increasing nutrient enrichment. World is also getting smaller, and increasing international shipping provide new opportunities for species to invade novel areas. These could be the reasons behind the recent invasion of P. magnifica to Finland. The first records of P. magnifica in our country, comes from Saimaa waterway about 15 years ago. Since then the species has expanded its range and can now be found from several locations along the Vuoksi watercourse. During the past few years, reliable sightings have also been observed from waterbodies outside the Vuoksi watercourse. These new sightings suggest that the species is invading new areas in Finland.

p. magnificaanttikanninen
P. magnifica colony attached to reed. Photo by Antti Kanninen

My postdoc research project

In my new project, I will focus to explore the on-going invasion of the Pectinatella magnifica in Finland.  The project will use novel, DNA-based, methods to estimate the invasion patterns and vectors the species use to invade new areas. During this project, it will also be investigated what kind environmental conditions the species prefer. The research will further provide information about the possible risks related to the PKD parasite.  Overall, the aim is that the results from this project will help environmental authorities in monitoring and managing the invasion of P. magnifica in Finland.

Some of the main study questions will be:

  1. Is the introduction of P. magnifica to Finland still an ongoing process or is statoblast bank the source of reintroduction in waterbodies
  2. What kind of sites are especially at risk for invasion of P. magnifica in Finland?
  3. What are the secondary vectors P. magnifica uses for its spread?
  4. Does P. magnifica found in Finland act as a host for the myxozoan parasite T. bryosalmonae that causes the salmonid fish disease PKD?

Good research results from good collaboration. I am extremely lucky that I have the change to implement this study in collaboration with a great group of professionals and scientists. This project will be carried out during years 2019-2020 at the Finnish Environment Institute (SYKE) in collaboration with Dr. Kristiina Vuorio (SYKE), as well as with other experts from the regional Centres for Economic Development, Transport and Environment. Close collaboration will also be implemented with Dr. Hanna Hartikainen from the Swiss Federal Institute of Aquatic Science and Technology and with PhD student Ilkka Nousiainen from the Estonian University of Life Sciences.

The project got funding for years 2019-2020 from the Maj and Tor Nessling foundation ( This foundation supports scientific research and communication aiming to solve environmental challenges.

–  K  –


Balounová Z., Rajchard J., Švehla J. & Šmahel L. (2011). The onset of invasion of bryozoan Pectinatella magnifica in South Bohemia (Czech Republic). Biologia, 66: 1091–1096. DOI: 10.2478/s11756-011-0118-y

Charalambidou I., Santamaria L., Figuerola J. (2003) How far can thefreshwater bryozoan Cristatella mucedo disperse in duck guts? Archiv für Hydrobiologie, 157: 547–554. DOI: 10.1127/0003-9136/2003/0157-054

Choi J.Y., Joo G.j., , Kim S.K., Hong D.G., & Jo H. (2015). Importance of substrate material for sustaining the bryozoan Pectinatella magnifica following summer rainfall in lotic freshwater ecosystems. South Korea.Journal of Ecology and Environment, 38: 375-381. DOI: 10.5141/ecoenv.2015.039

Hübschman JH (1970) Substrate discrimination in Pectinatella magnifica Leidy (Bryozoa). Journal of Experimental Biology, 52: 603–607.

Kollar P, Šmejkal K, Salmonová H, Vlková E, Lepšová-Skácelová O, Balounová Z, Rajchard J, Cvačka J, Jaša L,Babica P, Pazourek . (2016) Assessment of chemical impact of invasive Bryozoan Pectinatella magnifica on the environment: b cytotoxicity and antimicrobial activity of P. magnifica extracts molecules. Molecules. 21, pii: E1476. DOI: 10.3390/molecules21111476

Musil M, Rajchard J, Novotná K , Balounová Z  &  Ježková E (2018)The relationship between occurrence of invasive bryozoan Pectinatella magnifica (Leidy 1851) and parameters of the aquatic environment in the Biosphere Reserve Třeboňsko (Czech Republic). Wetlands Ecology and Management, 26: 977-983.  DOI 10.1007/s11273-018-9624-9

Nakano D., & Strayer D. L (2014) Biofouling animals in fresh water: biology, impacts, and ecosystem engineering. Frontiers in Ecology and the Environment, 12: 167-175.  DOI: 10.1890/130071

Nehring S (2005) International shipping – a risk for aquatic biodiversity in Germany. In: Nentwig, W. et al. (Eds.): Biological Invasions – From Ecology to Control. NEOBIOTA 6 (2005): 125-143

Pennak R. W. 1989. Freshwater invertebrates of the United States. John Wiley and Sons, New York, p. 628.

Pienimäki M. & Leppäkoski E. ( 2004). Invasion Pressure on the Finnish Lake District: Invasion corridors and barriers. Biological Invasion, 6: 331-346. DOI: 10.1023/B:BINV.0000034607.00490.95

Ruppert E.E. & Barnes R.D. 1993. Invertebrate Zoology. Saunders College Publishing, Fort Worth, 1056 pp. ISBN-10:0030266688, ISBN-13: 9780030266683

Seo J. E. (1998). Taxonomy of the freshwater bryozoans from Korea. Korean Journal of Systematic Zoology,  14: 371-378.

Šetlíková I., Skácelová O., Šinko J., Rajchard J. & Balounová Z. (2013) Ecology of Pectinatella magnifica and associated algae and cyanobacteria. Biologia, 68: 1136–1141. DOI: 10.2478/s11756-013-0262-7

Sterud E., Forseth T., Ugedal O., Poppe T.T.,  Jørgensen A., Bruheim T., Fjeldstad H-P., Mo T.A. (2007) Severe mortality in wild Atlantic salmon Salmo salar due to proliferative kidney disease (PKD) caused by Tetracapsuloides bryosalmonae (Myxozoa). Diseases of Aquatic Organisms, 77: 191-198.  DOI: 10.3354/dao01846

Vuorio K., Kanninen A., Mitikka S., Sarkkinen M. & Hämäläinen H. (2018) Management of Biological Invasions, 9: 1–10. DOI:

Wang B, Wang H, Cui Y. (2017) Pectinatella magnifica (Leidy, 1851) (Bryozoa, Phylactolaemata), a biofouling bryozoan recently introduced to China. Chinese Journal of Oceanology and Limnology, 35: 815–820. DOI: 10.1007/s00343-017-6052-2

Wood T. S. 2010. Bryozoans. ‒ In: Thorp J. H., A. P. Covich (eds.): Ecology and Classification of North American freshwater invertebrates, Academic Press Inc., San Diego, CA, 437-454.

Wood TS, Okamura B (2005) A new key to the freshwater bryozoans of Britain, Ireland, and continental Europe, with notes on their ecology. Freshwater Biology Association, Ambleside







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