Page 240 - (DK) Ocean - The Definitive Visual Guide

238 CHROMISTS

PHYLUM OCHROPHYTA Padina is the only genus of brown PHYLUM OCHROPHYTA Kelp normally grows at a depth of
seaweeds to have calcified fronds, 10–30m (30–100ft), but it can grow
Limey Petticoat hence this species’ common name of Giant Kelp much deeper in very clear water. The
Limey Petticoat. The reflective chalk huge branched holdfast, which is about
Padina gymnospora shows as bright white concentric Macrocystis pyrifera 60cm (24in) high and wide after three
HEIGHT Up to 10cm (4in) bands on the upper surface of the LENGTH 45m (150ft) years, is firmly attached to the sea bed.
fan-shaped fronds. The fronds are only From it, a number of stalks (or stipes)
HABITAT Rock pools and HABITAT Rocky sea
shallow subtidal rocks 4–9 cells thick and curled inwards. beds, occasionally sand stretch towards the surface, bearing
Older fronds may become split into many strap-like fronds, each buoyed
WATER TEMPERATURE WATER TEMPERATURE
20–30˚C (68–86˚F) wedge-shaped sections. This species 5–20˚C (41–68˚F) by a gas-filled bladder. The stem and
is widespread in tropical seas, often fronds continue to grow on reaching
DISTRIBUTION Coasts in tropical and subtropical growing in masses on shallow subtidal DISTRIBUTION Temperate waters of southern the surface, floating as a dense canopy.
areas worldwide rocks, and on old coral and shells. hemisphere and northeastern Pacific Giant Kelp has a two-phase life cycle.
Fronds (sporophylls) at the base of
Giant Kelp (pictured on pp.240–41) the kelp produce spores that develop
is the largest seaweed on Earth. It can into tiny creeping filaments. The
grow at the rate of 60cm (24in) per day filaments produce eggs and sperm,
in ideal conditions, and reaches lengths which combine to produce
of over 30m (100ft) in a year. Giant embryonic kelp plants.

which is not fixed to the sea bed, and
PHYLUM OCHROPHYTA
they may both be carried away by the
Oyster Thief tide. This seaweed has a thin wall with
only a few layers of cells. The outer
layer is made of small, angular cells
Colpomenia peregrina
DIAMETER Up to 10cm which contain the photosynthetic
(4in) pigments that give the Oyster Thief
HABITAT Intertidal and its brown colour.
subtidal rocks and shells
WATER TEMPERATURE
6–28˚C (49–83˚F)
DISTRIBUTION Coasts of western North America,
Japan, and Australasia; introduced in Atlantic

The Oyster Thief gets its unusual
name from its habit of growing on
shells, including commercially grown
oysters. The frond is initially spherical
and solid, but as it grows, it becomes
irregularly lobed and hollow and fills
with gas. Sometimes, this can make it
sufficiently buoyant to lift the oyster,

PHYLUM OCHROPHYTA PHYLUM OCHROPHYTA
Landlady’s Wig Sea Palm

Desmarestia aculeata Postelsia palmaeformis
LENGTH Up to 1.8m (6ft) LENGTH Up to 60cm
(24in)
HABITAT Subtidal rocks,
and kelp forests HABITAT Wave-exposed
shores
WATER TEMPERATURE
0–18˚C (32–64˚F) WATER TEMPERATURE
8–18˚C (46–64˚F)
DISTRIBUTION Near coasts in temperate, cold, and DISTRIBUTION West Coast of North America
polar regions
Sea Palms are kelps, which are large
This large seaweed has narrow brown brown seaweeds that belong to the
fronds with many side-branches. Its order Laminariales, as does Giant Kelp
bushy appearance is the reason for its (above). Unusually for a kelp, Sea Palm
common name of Landlady’s Wig. The grows on the midshore, where it
smallest branches are short and spine- forms dense stands on wave-exposed
like, hence the species name aculeata, coasts. It has a branched holdfast,
which means “prickled”. In summer, and a stout, hollow stalk, which
the whole plant is covered with stands erect when the tide is low.
delicate branched hairs. This species The top of the stalk is divided into
is particularly abundant on boulders many short, cylindrical branches,
and in kelp forests disturbed by waves. each of which bears a single frond
up to 25cm (10in) long, with
toothed margins and deep grooves
OCEAN LIFE the frond tips onto the holdfasts and
running down both faces. Spores are
released into the grooves and drip off
nearby rocks at low tide, so that the
developing seaweeds grow as dense
clumps. Some Sea Palms attach to
mussels and are later ripped off
during storms, making more rock
available for other Sea Palms to grow.