Short description of Amphibalanus improvisus, Bay barnacle

This sessile barnacle has a smooth conical shell composed of six smooth, white-grey plates, up to 17 mm in diameter and 10 mm high.  The shell opening is diamond shaped, narrow and slightly toothed.  A characteristic feature is the calcareous base with radial pattern.

Impact summary: Amphibalanus improvisus, Bay barnacle

May dominate and outcompete native species, especially for available habitat. The bay barnacle can also occupy the uppermost reaches of estuaries where it avoids competition.  It is a common nuisance through fouling of ships’ hulls, water inlet pipes, aquaculture products and equipment, and other submerged structures. 

Habitat summary: Amphibalanus improvisus, Bay barnacle

Most commonly found subtidally or on the lower shore in estuaries on stony, rocky and hard bottom substrates, to depths of around 50 metres.  This species exhibits wide salinity and temperature tolerances and often attaches to other surfaces including other animals, algae and ships’ hulls.

Overview table

Environment	Marine
Species status	Non-Native
Native range	Northern America
Functional type	Filter-feeder
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	Woolwich (Thames)
Date of first record	1854

Origin

The origin is unclear; some authors consider this an ‘Old World’ species – originating from Africa, western Asia and Europe – while others suggest it is native to the Atlantic coast of America.  It was known to Darwin from both sides of the Atlantic and from the Pacific in tropical South America. 

First Record

Darwin described the bay barnacle from GB and the eastern Atlantic in 1854.

Pathway and Method

Introduction pathways are most likely associated with fouling of ships’ hulls; the occurrence of successful populations in GB’s largest estuaries would seem to support this theory.   Larval transport within ballast water may also occur, and the species is thought to have been transported on oyster shells. 

Species Status

Very widespread around the Atlantic, this estuarine barnacle has been dispersed by shipping and now has a wide geographical distribution around the world including Northeast, Northwest and South Pacific, Mediterranean, Baltic, Caribbean and Red Seas. Invasions in Australia and New Zealand were reported to be unsuccessful.  It tolerates temperatures approaching freezing in Canada and the Baltic, and high summer temperatures in the Red Sea and the Caribbean, exhibiting a temperature range of over 30 °C.  It also tolerates a wide range of salinity, occurring from fully marine conditions to areas of very low salinity. 

Dispersal Mechanisms

Larvae are pelagic for 14-27 days and may be transported by water currents during this time. The success of larval dispersal depends on prevailing water currents and distance between suitable habitats.  Natural dispersal occurs when attached to mobile objects such as floating algae, hard-shelled animals and flotsam.  Dispersal may also take place when barnacles attach to man made objects such as boats, fishing gear and litter.

Reproduction

The bay barnacle is hermaphroditic (both sexes on one individual), as are all sessile barnacles. If cross fertilization is unsuccessful or impossible, the bay barnacle will resort to self-fertilisation.    Eggs develop in the mantle cavity before free swimming larvae are released, developing through seven phases, the last of which settles on a suitable substrate. Maturity is reached at a length of six to eight mm and individuals are reported to produce several broods each year under optimal conditions (>10 °C, 3-15 psu salinity).

Known Predators/Herbivores

 Worms, whelks, fish, birds, crabs, some sea slugs and starfish are amongst the wide range of animals to prey upon acorn barnacles.

Resistant Stages

None known.

Habitat Occupied in GB

The bay barnacle seems to be restricted to areas of constantly low salinity or estuaries where wide fluctuations of salinity occur.  Although tolerant of full salinities this species doesn’t appear to occupy regions between estuaries, perhaps due to competition.  In Britain it is found mostly in the larger estuaries on hard substrata, on the lower shore or subtidally. It may be found in the uppermost reaches of estuaries where it avoids competition.

Native range unclear; it is known from Africa, western Asia, both sides of the Atlantic and the Pacific coast of South America.  In GB it is common in larger estuaries, but with limited distribution in the north.

Environmental Impact

The bay barnacle may dominate and outcompete native species, particularly for space.  This could lead to changes in trophic interactions within food webs. 

Health and Social Impact

Sharp shells may cause injuries to tourists using the beach.

Economic Impact

A notorious fouling organism, the bay barnacle rapidly colonises most submerged manmade structures.  Fouling of ships’ hulls, industrial water inlet pipes and other surfaces can incur cleaning costs and cause technical problems leading to further economic losses.  The application of antifouling paints may alleviate these problems, but often causes significant damage to the environment.  The bay barnacle is also known to foul mussels, oysters and the equipment associated with aquaculture activities.

Identification

NIMPIS (2010) Balanus improvisus reproduction and habitat. National Introduced Marine Pest Information System. [online] Available from: http://www.marinepests.gov.au/nimpis

Olenin, S. (2006) Delivering Alien Invasive Species Inventories for Europe: Balanus improvisus. [online] Available from: http://www.europe-aliens.org/speciesFactsheet.do?speciesId=50128

Biology, ecology, spread, vectors

Davenport, J. (1976) A comparative study of the behavior of some balanomorph barnacles exposed to fluctuating seawater concentrations. Journal of the Marine Biological Association of the United Kingdom, 56, (4), 889-907.

Furman, E.R., Yule, A.B. & Crisp, D.J. (1989)  Gene flow between populations of Balanus improvises Darwin (Cirripedia) in British estuaries. Scientia Marina, 53, (2-3), 465-472.

Furman, E.R. (1990) Geographical variation of Balanus improvisus in biochemical and morphometric characters. Journal of the Marine Biological Association of the United Kingdom, 70, (4), 721-740.

Furman, E.R. & Yule, A.B. (1991)  Balanus improvises in British estuaries: gene flow and recolonisation. In: Elliott, M. & Ducrotoy, J.P. (Editors). Estuaries and coasts: spatial and temporal intercomparisons. ECSA19 Symposium, University of Caen, France. P273-276. Fredensborg: Olsen and Olsen.

Kawahara, T. (1963) Invasion into Japanese waters by the European barnacle Balanus improvises Darwin. Nature, 198, 301.

Kerckhof, F. (2002) Barnacles (Cirripedia, Balanomorpha) in Belgian waters, an overview of the species and recent evolutions, with emphasis on exotic species.  Bulletin De L’Institut Royal Des Sciences Naturelles De Belgique. Biologie, 72 (Supplement), 93-104.

Schram, F.R. & Vaupelklein, J.C. Von, (Editors) (1999) Crustaceans and the biodiversity crisis. Proceedings of the fourth international crustacean congress, Amsterdam, The Netherlands, July 20-24, 1998, 1, 1021p. Leiden, The Netherlands: Koninklijke Brill

Management and impact

De Rivera, C.E., Steves, B.P., Ruiz, G.M., Fofonoff, P. & Hines, A.H. (2006)  Northward spread of marine nonindigenous species along western North America: forecasting risk of colonization in Alaskan waters using environmental niche modeling. Report submitted to Prince William Sound Regional Citizens’ Advisory Council & U.S. Fish and Wildlife Service. [online] Available from: http://www.pwsrcac.org/docs/d0041100.pdf

Olenin, S. (2006) Delivering Alien Invasive Species Inventories for Europe: Balanus improvises. [online] Available from: http://www.europe-aliens.org/speciesFactsheet.do?speciesId=50128

General

Olenin, S. (2006) Delivering Alien Invasive Species Inventories for Europe: Balanus improvises. [online] Available from: http://www.europe-aliens.org/speciesFactsheet.do?speciesId=50128