Page 241 - (DK) Ocean - The Definitive Visual Guide

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CROFTER’S WIG

In very sheltered bays and sea
lochs, detached pieces of “normal”
Knotted Wrack will continue to
grow, lying loose on the sea bed.
In situations where the fronds are
alternately covered by salt and
fresh water, they divide repeatedly
to form a dense ball that has
no bladders or reproductive
structures. This unattached form,
which is known as Crofter’s
Wig, appears very different to
the attached form, even though
it is genetically identical.

Knotted Wrack belongs to a group a series of bladders. The bladders hold
PHYLUM OCHROPHYTA
of tough brown seaweeds that often the fronds up in the water so that they
Knotted Wrack dominate rocky seashores in cooler gain maximum light, which is an
climates. It is firmly attached to the advantage in the often turbid waters
rocks by a disc-shaped holdfast, from where Knotted Wrack grows. This
Ascophyllum nodosum
LENGTH Up to 3m (10ft) which arise several narrow fronds that also makes it harder for grazing snails
often grow to 1m (3ft) in length, and to reach the fronds when the tide is in.
HABITAT Sheltered
seashores exceptionally to 3m (9ft) in very The dark brown fronds may be
sheltered situations. Single oval bleached almost to yellow in summer.
WATER TEMPERATURE
0–18˚C (32–64˚F) bladders grow at intervals down the Reproductive structures that look like
frond. The fronds produces about one swollen sultanas are borne on short
DISTRIBUTION Coasts of northwestern Europe, bladder a year, so the seaweed’s age side-branches, and orange eggs can
eastern North America, and north Atlantic islands can be roughly estimated by counting sometimes be seen oozing from them.
PHYLUM OCHROPHYTA Neptune’s Necklace is one of the
many brown seaweeds endemic
Neptune’s Necklace (unique) to New Zealand and the
cooler waters around Australia. Its
Hormosira banksii distinctive fronds, which look like
LENGTH Up to 30cm a string of brown beads, are made up
(12in) of chains of ovoid, hollow segments
HABITAT Lower shore joined by thin constrictions in the
and subtidal rocks stalk. Small reproductive structures
WATER TEMPERATURE are scattered over each “bead”.
10–20˚C (50–68˚F) Dense mats composed almost
DISTRIBUTION Coasts of southern and eastern entirely of this one species can be
Australia and New Zealand found on seashore rocks. The fronds
are attached to the
rock by a thin,
disc-shaped holdfast.
Neptune’s Necklace
also lives unattached
among mangrove
roots. The shape of
its segments varies
according to habitat. PHYLUM OCHROPHYTA Japweed can reproduce all year round
They are spherical and forms dense stands in quiet waters.
and about 2cm (/4 in) Japweed Native to Japan (hence its common
3
wide in fronds name), it was accidentally introduced
growing on sheltered Sargassum muticum to western North America and
rocks, mussel beds on LENGTH 2–10m Europe, and is steadily expanding its
tidal flats, or in (6–33ft) range in these areas. It outcompetes
mangrove swamps. HABITAT Intertidal and other seaweeds and in these regions
Fronds growing on subtidal rocks and stones is regarded as an invasive species. This
subtidal rocks on WATER TEMPERATURE long, bushy seaweed has numerous OCEAN LIFE
moderately exposed 5–26˚C (41–79˚F) side-branches, which have many
coasts have smaller DISTRIBUTION Coasts of Japan, introduced in leaflike fronds up to 10cm (4in) long.
segments that are just western Europe and western North America The fronds bear small, gas-filled
6mm (/4 in) long. bladders, either singly or in clusters.
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