[151] Fucus vesiculosus, Bladder Wrack – and other Brown Algae
Introduction
Fucus vesiculosus, Bladder Wrack or (Bladder-wrack), is a very common seaweed. To be more precise it is a species of Brown Algae and I will consider other Brown Algae in this blog.
Taxonomy
Kingdom – Chromists
Superphylum – Heterokonts/ Straminopiles (or Stramenopiles)
Phylum – Ochrophyta (Mostly photosynthetic heterokonts with red-algal plastids)
Class – Phaeophyceae (Brown Algae)
Subclass – Fucophycidae
Order – Fucales
Family – Fucaceae
Genus – Fucus
Scientific Name – Fucus vesiculosus
See text for other species.
Name
Wrack is cognate with wreck and used to mean anything washed ashore from a seawreck, and hence, anything washed ashore such as seaweed.
The Latin fucus meaning lichen or a red dye comes from Ancient Greek phukos meaning seaweed. Vesicula is a diminutive from the Latin vesica meaning bladder.
Brown Algae
I have to say something about Brown Algae. The ones we see are common types of seaweed and most people would normally think of them as plants – but the taxonomy is complex, as you may remember from [079] Carrageen, which considered Red Algae.
Of the three types of Algae that we normally consider as seaweed, Red Algae and [352] Green Algae just creep into the edges of what are normally considered to be plants but Brown Algae comes outside. Don’t ask me why.
Brown Algae form a Class, Phaeophyceae. I will not attempt to explain Heterokonts or any of the taxonomic levels above and below Phaeophyceae but will just say a little about a few species, with some pictures.
[As you may have guessed, one reason for not trying to explain is that I really don’t understand myself.]
All of my Brown Algae pictures come from the intertidal areas of the Isle of Wight coast. The first four species listed below are the most common forms of seaweed found on the British coasts.
(1) Fucus vesiculosus, Bladder Wrack
Fucus vesiculosus has other names including Dyer’s Fucus and Red Fucus. It was the original source of Iodine, discovered in 1811 and has been used to treat diseases related to iodine deficiency.
It is between dark brown and olive brown and has long, flat fronds, with almost spherical air bubbles that give it its name.
Bladder Wrack is the most common seaweed found all around the shores of the UK. It can also be found on the coasts of the North Sea, the Baltic Sea and the northern coasts of the Atlantic Ocean.
It is only found between high tide and low tide levels. I found a large quantity of it on the rocky shore just below Osborne House on the Isle of Wight.
(2) Fucus spiralis, Spiral Wrack, comes from the same Genus.
It has the same area of natural distribution and its fronds are similar in colour but it doesn’t have the air bladders of Fucus vesiculosus.
(3) Fucus serratus, Serrated Wrack (or Toothed Wrack), also from the same Genus.
This species is similar to Fucus spiralis but its fronds have serrated edges.
(4) Ascophyllum nodosum, Egg Wrack, from the same family, Fucaceae.
This genus only has one species. It is very similar to Bladder Wrack but the air bladders are more egg-shaped than spherical.
(5) Halidrys siliquosa, from the same Order, Fucales,Family Sargassaceae. (No common name.)
This another very common seaweed with long fronds, somewhat thinner than the first three. It has some air bladders and is native to just the coasts of the British Isles.
(6) Dictyopteris Polypoioides, from another Subclass, Dictyophycidae,Order Dictyotales, Family Dictyotaceae.
This seaweed is flatter and thinner and is found on the southwestern coasts of the UK and elsewhere.
There are many other species of brown algae that are difficult to identify without expert knowledge and microscopic examination. I have decided not to show any pictures because of uncertainty about identification.
See Also
As noted above, Green Algae will come a lot later.
The Species of Britain 