Page 246 - (DK) Ocean - The Definitive Visual Guide

244 RED SEAWEEDS

Red Seaweeds Habitats and
Distribution

On the shore, red seaweeds
RED SEAWEEDS are attractive
DOMAIN Eucarya mostly live at the lowest levels
marine plants and are found where they are less likely to
KINGDOM Plantae
in shallow seas around dry out. In deeper water their
DIVISION Rhodophyta additional pigments allow them
the world. Their red color
CLASSES 2 or more to flourish in the dim blue light
comes from the extra
SPECIES 6,394 that remains and they extend
pigments they have in deeper than brown and green
seaweeds. Red (and brown)
addition to green chlorophyll. While they appear
seaweeds are less abundant in
to be plants, they differ in some cellular details and tropical waters, an exception BARBED COLONIZER
metabolism. Many scientists do not consider them being the red oralline encrusting This red seaweed has barbed branches
enabling detached fragments to hook onto
to be true plants, but there is as yet no full consensus. seaweeds, which play a very other organisms and even ships’ hulls.
important role in cementing It disperses in this way and has been
coral reefs. transported outside its native range.
Anatomy DULSE

The shape and form of red seaweeds is highly diverse but in general Red seaweeds rely on moving water to bring
them nutrients and oxygen. The fingerlike
they are relatively small and delicate. Like green and brown seaweeds
fronds of this dulse increase its surface
most have a holdfast, stipes (stems) and fronds that absorb water, area while preventing it from tearing
nutrients, and sunlight. Coralline seaweeds have a heavily calcified in rough conditions.
frond, which is too hard for most grazers to eat. They look more
like pink crusts or small corals than plants. Maerl
forms unattached nodules that resemble twiggy
coral lying on the seabed. Some red
seaweeds have two phases, growing as a
tiny long-lived crust and as an annual
bushy frond. These look so
different they were first
described as separate species.

midrib

frond

PERENNIAL SPECIES
stipe
This beautiful red seaweed
is called sea beech. It
grows new fronds each
year from a perennial stipe,
holdfast and reproduces from spores
in winter.

DIVISION RHODOPHYTA grazed by seashore animals such as
limpets. Ongoing work on molecular
Small Jelly Weed sequencing is gradually resolving
some of these problems, and Gelidium
Gelidium foliaceum foliaceum is one species that has recently
LENGTH been reclassified. It has a flattened,
2 in (5 cm) much lobed and curled frond, which
HABITAT grows in dense clumps on rocky
Intertidal rocks seashores. The fronds are tough and
WATER TEMPERATURE cartilaginous, and the seaweed is
OCEAN LIFE There are many species of Gelidium from a creeping stem, or stolon. This
attached to the rock at frequent intervals
50–68˚F (10–20˚C)
by small hairlike structures, or rhizoids,
DISTRIBUTION Coasts of southern Africa and
southern Japan
creeping habit is probably the main
method of spreading, but some species
of Gelidium also reproduce sexually.
worldwide, and they are difficult to
Some Gelidium species are a source
identify because the plants can look
of the gelatinous substance agar, which
very different depending on their
habitat and whether they have been
is used in cooking and microbiology.