Monday 21 January 2013

Common seaweeds of the shore -Wracks (Part 2)


Below are images of brown seaweeds, other than fucoids that come under the generic term 'wracks'. There are more species than shown here, as only those for which I have photos are shown.

Thong weed (Himanthalia elongata) is  olive brown with long strap like dichotomous branching fronds. Himanthalia elongata occurs at the low water mark and into the shallow subtidal.

Thong weed (Himanthalia elongata)  fully submerged.

Early growth stages of Thong weed (Himanthalia elongata) from which the long fronds grow.  


Bifurcaria bifurcata is a brown seaweed with cylindrical dichotomous branching fronds. Bifurcaria bifurcata occurs in rock pools of the lower shore.


Sargassum muticum is a brown bushy weed with small spherical air bladders. It occurs in rock pools of the lower shore and shallow sublittoral. Sargassum muticum is an invasive species that often out competes other seaweeds and can block out the sun from rock pools.
Bifurcaria bifurcata  and Sargassum muticum can dominate lower shore pools.
Rainbow wrack (Cystoseira tamariscifolia)  is an iridescent bushy weed found in pools of the lower shore. There are a number of 'bushy' wracks belonging to the genus Cystoseira in the UK.
Sea Oak (Halidrys siliquosa) has alternate branching with oblong air bladders. It occurs in pools of the lower shore and shallow sublittoral.


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