Environmental Engineering Reference
In-Depth Information
Belowthelichenzonethemajorityoftheshoreisencrustedwiththeacornbarnacles
Chthamalus stel-
latus
and
C. montagui
, together with limpets. These grade into a lower zone dominated by the barnacle
Semibalanus balanoides
. In both of these zones there may be extensive common blue mussel beds within
crevices and in areas between the bedrock. Lower down the shore mussels become even more dominant
and can cover whole platforms. There are areas free of mussels, however, and in these serrated wrack
occurs together with an understorey of red seaweeds. The species found in this understorey vary depend-
ing on the distance from low water and whether sand is present on the lower shore. High on the shore
pepper dulse
Osmundea pinnatifida
occurs along with carragheen
Mastocarpus stellatus
, which has been
used from about 1830 in herbal medicine as a treatment for lung complaints. Towards the lower shore
moresand-tolerantredseaweedscanbefoundsuchastheredrosegrassweed
Rhodothamniella floridula
,
which forms distinct mats. Small hummocks of grass weed may also contain other smaller red and brown
algae and species of worm and amphipod may burrow into the mat. Where sand scour is more severe,
it may be rare or absent and ephemeral green seaweeds such as grasskelp
Enteromorpha
spp. and laver
Porphyra umbilicalis
dominate the substratum.
