Bladder wrack (Fucus vesiculosus)

Bladder wrack buoyed up underwater by air bladders
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Bladder wrack fact file

Bladder wrack description

GenusFucus (1)

Bladder wrack is a familiar large olive-brown coloured seaweed (3), which attaches to rocky substrates by means of a small disc (4). The flattened, branching fronds, which grow up to 2m in length, have an obvious midrib, and are covered with spherical air bladders, which tend to occur in pairs on either side of the mid-rib (3). In small plants, however, air bladders may be entirely absent (3). Forked and pointed reproductive structures occur at the tips of the fronds (3). The appearance of bladder wrack varies depending on the environmental conditions in which it occurs; in more sheltered areas there are many air bladders, whereas there are fewer in more exposed conditions (3). In very exposed areas, a form of bladder wrack called Fucus vesiculosus forma linearis may arise, which completely lacks bladders (3).

Size: up to 2 m (2)

Bladder wrack biology

The air bladders keep the fronds of the wrack in illuminated waters, where it is able to photosynthesise (3). In exposed areas, it is beneficial for the wrack to lack bladders, as this decreases the potential for severe damage, and minimises the risk of it being detached and swept away (3).

Bladder wrack may live for up to three years. There are separate male and female plants, and reproduction takes place once a year (2). Sex cells are produced in structures known as 'receptacles' located at the tips of the fronds. Eggs and sperm are released simultaneously into the water; the eggs release a pheromone that attracts the sperm (4), and fertilisation occurs externally. The fertilised egg settles to the substrate where it becomes attached after just a few hours (2).

Bladder wrack provides shelter for a number of marine species, including the tubeworm Spirobis spirobis, various isopods, and snails (2). It has been harvested by humans for use as a food source, and in various health products (2).


Bladder wrack range

Occurs around the coastline of Britain, and is also known from Ireland, the Baltic Sea, Norway, the Atlantic coast of France, Spain and Morocco, as well as Greenland, and the eastern coasts of Canada and the USA (2).

You can view distribution information for this species at the National Biodiversity Network Atlas.

Bladder wrack habitat

Bladder wrack occurs intertidally on the middle-shore, where it grows attached to rocky substrates, and is often associated with knotted wrack (Acophyllum nodosum) in the zone above toothed wrack (Fucus serratus) (3). It can survive in a wide range of exposures (3).


Bladder wrack status

Common and widespread (2).


Bladder wrack threats

This seaweed is not currently threatened.


Bladder wrack conservation

No conservation action has been targeted at this species.

There may be further information about this species available via the National Biodiversity Network Atlas.

Find out more

For more on this species see the Marine Link Information Network (MarLIN) species account:



This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:


Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.


  1. National Biodiversity Network Species Dictionary (November, 2002)
  2. White, N., (2000) Fucus vesiculosus. Bladder wrack. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth:Marine Biological Association of the United Kingdom. (November, 2002)
  3. Fish, J.D. and Fish, S. (1996) A student's guide to the seashore. Second Edition. Cambridge University Press, Cambridge.
  4. The Seaweed Site. Michael D. Guiry (November, 2002)

Image credit

Bladder wrack buoyed up underwater by air bladders  
Bladder wrack buoyed up underwater by air bladders

© Nick Upton /

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