Amphibalanus amphitrite - Striped barnacle

The striped barnacle is a cosmopolitan barnacle that occurs naturally in almost all tropical and subtropical seas. For example, in the Mediterranean Sea, this barnacle has been a common species since time immemorial ^{[2, 3]}. Populations of the species occur along the Iberian Peninsula and the French Atlantic Coast if environmental parameters (e.g. temperature) are favourable ^[4]. It is not easy to determine its natural northern distribution limit, but it is probably located on the French-Atlantic coast ^[5].

First observation in Belgium

Since February 1995, the striped barnacle has been regularly found on our coast, both on objects washed ashore and in local populations. In September 1995, the first Belgian population was observed on a breakwater in Koksijde ^[6].

However, when reviewing the collection of the Royal Belgian Institute of Natural Sciences, it became clear that the first specimen of the species had already been discovered in 1952. At the time, this specimen, which was found in an oyster farm in the port of Ostend, was incorrectly identified as the sea tulip Megabalanus tintinnabulum ^[3].

Spreading in Belgium

The population of striped barnacles on one of the breakwaters of Koksijde wasn’t found anymore after September 1995. However, the population observed in 1996 in the Mercator marina at Ostend appeared to be permanent. Even after the severe winters of 1995-96 and 1996-97 live specimens were found here, against all expectations. In the summers of 1996 and 1997, the striped barnacle managed to reproduce in our coastal area. In 1997, two spawns were recorded ^{[5, 6]}.

In the harbour of Ostend, the species is present in all docks on hard constructions, but also attached to the hull (hull fouling) of pleasure boats ^[3]. Striped barnacles have also been observed occasionally in the sluice-dock of Ostend ^[7]. In Nieuwpoort, the species is only found on the hulls of yachts. In the ports of Zeebrugge and Blankenberge, the species has not yet been observed. The striped barnacle can also be found on various navigation buoys in the open sea ^[3].

Remarkably, this barnacle species has managed to survive in places that – in contrast to earlier English and Dutch observations – are not in the vicinity of power stations with a heated water outlet. This may be due to some warm summers since 1990, which allowed good reproduction ^[6].

Spreading in neighbouring countries

No one less than Charles Darwin, who first described this species in 1854, reported the striped barnacle in the Mediterranean and along the Portuguese coast ^[8]. Archaeological and geological studies show that the species has been present in the Mediterranean for a long time ^[9]. Along the Atlantic coast of France, this barnacle was first observed in 1914, in La Rochelle ^[10]. In 1928, individuals were also found in Le Havre (the English Channel). Today, the species is common in the port of Dunkirk ^{[11, 12]}. In England, the first population was discovered in 1937, at Shoreham ^[13].

In the Netherlands, this species has been observed since 1962 ^[14]. Before, the striped barnacle was mainly found in the vicinity of cooling water installations of power stations, where an artificially higher water temperature prevails, such as in the cooling water channel of the Provincial Electricity Company of Zeeland (PZEM) near Vlissingen. The temperature in 1974 varied between 12.4 °C (January) and 36.9 °C (July). In the 1970s, this species of barnacle expanded rapidly in Lake Veerse, although the water here is not artificially heated ^{[5, 15]}. It is not certain whether Amphibalanus amphitrite still occurs in the Netherlands today ^[16].

This barnacle is a typical biofouling species. By adhering to ship hulls, it can be widely distributed ^[5]. This barnacle often has dense populations in the vicinity of ports, even within its natural range.

The striped barnacle is found both high up in the tidal zone as well as permanently submerged. The species can tolerate varying levels of salinity. However, the barnacle prefers warmer water temperatures, which promotes reproduction and considerably increases the survival rate of the larvae. When conditions at the Belgian coast are favourable - as they were during the summers of 1995 and 1996 - a lot of larvae can survive, settle down and grow into adults ^[5].

The species is regularly present in areas with certain physical stress or degree of pollution ^[3]. In the heavily polluted Visserijdok, a dock in the port of Ostend, the striped barnacle is commonly found ^[6].

Originally it was assumed that the striped barnacle would not survive the cold winters in our regions. After the harsh winter of 1997 – when even the Mercator dock in Ostend froze – it appeared that sexually mature individuals were still present on several yacht hulls ^[6]. In the summer of 1997, experimental panels were set up to check whether the present individuals were indeed reproducing. After some time, several recently-settled juveniles were found on all panels. Apart from these permanent populations, our coast probably has an irregular and accidental influx of larvae from elsewhere, via ballast water ^[6].

The striped barnacle belongs to the permanent fouling community of ships, harbours, buoys and other hard substrates along our coast. Biofouling of barnacles on ships causes extra drag and thus extra fuel consumption, but removal is very costly. A common technique to avoid barnacle fouling on ships' hulls is to clean the hull under high pressure in a dry dock and then treat it with antifouling, pesticide-containing paint ^[6]. When barnacles become established in industrial cooling water systems, chlorination is a commonly-used method of removing them ^[17]. Recent research suggests that biofouling can be prevented by vibrating the hull at an ultrasonic frequency, which would prevent barnacles and other organisms from adhering to the hull ^[18].

The striped barnacle occurs – together with the New Zealand barnacle Austrominius modestus – in the upper tidal zone where the acorn barnacle Semibalanus balanoides is also found ^{[6, 19]}. The wrinkled barnacle Balanus crenatus occurs lower down in the tidal zone. In harbours, the striped barnacle appears to compete for space with the bay barnacle Amphibalanus improvisus, as well as with numerous other fouling organisms such as bryozoans, tube-dwelling amphipods, tube worms and sea squirts. These fouling organisms can overgrow the striped barnacle and – in combination with silt deposition – cause a decay process that results in the death of the underlying barnacles.

The striped barnacle is – as its name suggests – easily recognisable by the purple stripes on the surface of its shell. This is particularly striking in recent, well-developed individuals, but due to weathering processes, the stripe pattern may disappear in older specimens. An overview of the detailed characteristics for a correct determination of this species can be found in the literature ^{[5, 20]}.

Per brood, the striped barnacle can produce 1,000 to 10,000 eggs. Fertilisation is internal ^[21] and the floating larvae get carried away by the prevailing sea currents. The number of larvae produced increases with higher water temperatures (at least between 20 and 30 °C) ^[22].

These barnacles grab edible particles from the water using a protruding cirral fan ^[23], which is more or less reminiscent of a sieve with which they strike through the water. Food particles present in the water column adhere to the cirral fan and are taken to the mouth and ingested.

[1]         World Register of Marine Species (WoRMS) (2020). Amphibalanus amphitrite (Darwin, 1854). [http://www.marinespecies.org/aphia.php?p=taxdetails&id=421137] (2020-11-17).

[2]         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]

[3]         Kerckhof, F.; Cattrijsse, A. (2001). Exotic Cirripedia (Balanomorpha) from buoys off the Belgian coast. Senckenb. Marit. 31(2): 245-254. [http://www.vliz.be/en/imis?module=ref&refid=25318]

[4]         Fischer-Piette, E.; Prenant, M. (1956). Distribution des cirripèdes intercotideaux d’Espagne septentrionale. Bull. Cent. Etud. Rech. Sci. Biarritz 1(1): 7-19. [http://www.vliz.be/en/imis?module=ref&refid=121050]

[5]         Kerckhof, F. (1996). Balanus amphitrite (Darwin, 1854): een nieuwe zeepok voor onze fauna? De Strandvlo 16(3): 100-109. [http://www.vliz.be/en/imis?module=ref&refid=19169]

[6]         Kerckhof, F. (1998). Het voorkomen van Balanus amphitrite langs de kust, in 1996 en 1997. De Strandvlo 18(4): 170-179. [http://www.vliz.be/en/imis?module=ref&refid=19225]

[7]         Kerckhof, F. (2019). Persoonlijke mededeling

[8]         Darwin, C. (1854). A monograph of the subclass Cirripedia, with figures of all the species. The Ray Society: London, UK. 684, 30 plates pp. [http://www.vliz.be/en/imis?module=ref&refid=121051]

[9]         Wirtz, P.; Araujo, R.; Southward, A.J. (2006). Cirripedia of Madeira. Helgol. Mar. Res. 60(3): 207-212. [http://www.vliz.be/en/imis?module=ref&refid=120706]

[10]       Prenant, M. (1929). Balanus amphitrite (Darwin) sur les côtes atlantiques françaises. Bull. Soc. Zool. Fr 49(3-5): 212-213. [http://www.vliz.be/en/imis?module=ref&refid=121052]

[11]       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]

[12]       Davoult, D.; Dewarumez, J.-M.; Glaçon, R. (1993). Nouvelles signalisations d'espèces macrobenthiques sur les côtes françaises de la Manche orientale et de la Mer du Nord: 4. Groupes divers. Cah. Biol. Mar. 34(1): 55-64. [www.vliz.be/en/imis?module=ref&refid=35748]

[13]       Bishop, M.W.H. (1950). Distribution of Balanus amphitrite Darwin var. denticulata Broch. Nature (Lond.) 165(4193): 409-410. [http://www.vliz.be/en/imis?module=ref&refid=121055]

[14]       Borghouts-Biersteker, C.H. (1969). Balanus amphitrite Darwin in Nederland (Crustacea, Cirripedia). Zoologische Bijdragen 2: 4-7. [http://www.vliz.be/en/imis?module=ref&refid=37805]

[15]       Vaas, K.F. (1975). Immigrants among the animals of the Delta-Area of the SW Netherlands. Hydrobiol. Bull. 9(3): 114-119. [http://www.vliz.be/en/imis?module=ref&refid=14656]

[16]       Huwae, P.; Kerckhof, F. (2011). Checklist van de in Nederland en België aangetroffen rankpotigen (Crustacea, Cirripedia), met gegevens over de vindplaatsen van de genoemde soorten. Het Zeepaard 71(1): 15-30. [http://www.vliz.be/en/imis?module=ref&refid=203109]

[17]       Khalanski, M.; Borderet, F. (1981). Impact de chlorination sur la qualité de l'eau et le plancton. Bilan des études réalisées sur le site de Gravelines de 1979 à 1983. Report EDF DER HE/31-85.09. [S.n.]: [s.l.].  pp. [http://www.vliz.be/en/imis?module=ref&refid=120919]

[18]       Seth, N.; Chakravarty, P.; Khandeparker, L.; Anil, A.C.; Pandit, A.B. (2015). Quantification of the energy required for the destruction of Balanus Amphitrite larva by ultrasonic treatment. J. Mar. Biol. Ass. U.K. 90(7): 1475-1482. [http://www.vliz.be/nl/catalogus?module=ref&refid=299125]

[19]       Kerckhof, F. (2002). Barnacles (Cirripedia, Balanomorpha) in Belgian waters, an overview of the species and recent evolutions, with emphasis on exotic species. Bull. Kon. Belg. Inst. Natuurwet. Biologie 72(Suppl.): 93-104. [http://www.vliz.be/en/imis?module=ref&refid=66768]

[20]       Southward, A.J. (2008). Barnacles: keys and notes for the identification of British species. Synopses of the British Fauna, N.S. 57. Field Studies Council: Shrewsbury. ISBN 978-1-85153-270-4. viii, 140 pp. [http://www.vliz.be/en/imis?module=ref&refid=119980]

[21]       El-Komi, M.; Kajihara, T. (1991). Breeding and moulting of barnacles under rearing conditions. Mar. Biol. 108(1): 83-89. [http://www.vliz.be/en/imis?module=ref&refid=121058]

[22]       Desai, D.; Anil, A.; Krishnamurthy, V. (2006). Reproduction in Balanus amphitrite Darwin (Cirripedia: Thoracica): influence of temperature and food concentration. Mar. Biol. (Berl.) 149(6): 1431-1441. [http://www.vliz.be/nl/catalogus?module=ref&refid=260022]

[23]       Labarbera, M. (1984). Feeding currents and particle capture mechanisms in suspension feeding animals. Am. Zool. 24: 71-84. [http://www.vliz.be/en/imis?module=ref&refid=120624]

VLIZ Alien Species Consortium (2020). Amphibalanus amphitrite – Striped barnacle. Non-native species of the Belgian part of the North Sea and adjacent estuaries anno 2020. Flemish Institute for the Sea (VLIZ). 6 pp.