Wracks
Although very common and therefore ideal to get to know, the wracks can be tricky.
Found across lots of different intertidal environments, they can look different in their need to adapt to those. Keeping that in mind, however, they can be fairly straightforward if you look in particular for certain features.
You will see what they look like in different situations and understand how to separate them from each other.
The species in focus are:
bladder wrack/gwymon codog mân (Fucus vesiculosus)
spiral wrack/gwymon troellog (Fucus spiralis)
channel wrack/gwymon rhychog (Pelvetia canaliculata)
serrated wrack/gwymon danheddog (Fucus serratus)
egg wrack/gwymon codog bras (Ascophyllum nodosum)
Once you’ve gone through the information, you will then be tested.
Wrack recap
bladder wrack/gwymon codog mân (Fucus vesiculosus)
© Clare and Charlie Welsh
- likes midshore and into lowshore
- large brown algae with flat wide frond (the leaf-type area on algae)
- has two, small, rounded bladders
- situated together somewhere along frond (nb sometimes doesn’t make bladders – especially in exposed areas)
- has a midrib
- beware hybridisation/confusion with spiral wrack (see section below)
spiral wrack/gwymon troellog (Fucus spiralis)
©Molly Jones
- likes highshore
- large brown algae with flat wide frond
- frond twists as it grows looking like a spiral
- has a midrib
- beware hybridisation/confusion with bladder wrack (see confusions section below)
- the receptacles (breeding bubbles) grow at the end and have a flat rim edging to them.
channel wrack/gwymon rhychog (Pelvetia canaliculata)
©Charlie and Clare Welsh
- short-growing algae
- likes highshore
- thin frond
- frond is rounded making it look like a half pipe (hollow back facing rocks, usually)
- green-brown
- the breeding receptacles, when growing, are long and thin on the ends
serrated wrack/gwymon danheddog (Fucus serratus)
© The Leasks
- a low shore wrack
- has a midrib
- fronds about 2cm wide,
- fronds splitting into two, repeatedly
- yellow-brown
- has patches of tiny white hairs on frond
- serrated edges to the fronds
- fronds can lie on top of each other, layering
- also called toothed wrack and saw wrack
egg wrack/gwymon codog bras (Ascophyllum nodosum)
© North Wales Wildlife Trust
- large (long) algae
- like Midshore (can be very common on sheltered shores)
- thin frond
- single, egg-shaped bladder takes up the entire width of frond
- often covered in fluffy red, short-growing seaweed called Polysiphonia lanosa
- also called knotted wrack
After that introduction to five of our wrack seaweeds, you will be pleased to know that for three of them there are few other wrack species you can confuse them with, once you’ve found the features mentioned. However, for one, the problem isn’t just comparison between two species, it’s hybridisation.
Bladder wrack can easily be confused with spiral wrack, another seaweed with a wide frond and midrib. A major problem comes with the fact that these two species can hybridise, but that’s another story. In the meantime on semi-exposed shores bladder wrack can grow without bladders, so look for these differences to attempt ID to species:
- Breeding “receptacles” (look like bladders at the end of frond at certain times of year, bladder wrack doesn’t have a rim encircling the receptacles)
- Spiral wrack generally lies below channel wrack (a short-growing high shore species) and above bladder wrack on the shore.
Alternative factoids
More fascinating fucoid facts (for a start, Fucoid is the word which is used when grouping the wracks). This section will not appear in the quiz as questions.
The word wrack is thought to have come from old German “wrek-a” indicating “something driven”. The zone this algae group tends to live on is intertidal rocks just where ships find the “wrecking zone” a place where ships are driven out of the sea.
Egg wrack can live for a lot longer than the other wracks (3-5 years), especially in sheltered locations (up to 15 years).
Wracks with bladders use them to keep the fronds raised when the tide is in to help them acquire the light they need to photosynthesise.
Egg wrack age can be estimated by find the holdfast and the longest front and counting the number of bladders along it. This gives a general idea of the number of years of growth (1 bladder = 1 year).
All species of wrack (except spiral wrack) have male and female plants. Ripe male plants of serrated wrack can be spotted due to their orange colouration.
The next section is NOT the quiz, it’s a very shallow look at the green and red algae. You will be tested on both wracks and the other seaweeds after going through that section.