The algae are similar
to the plants in that they can also photosynthesise but are usually single-celled
organisms, or grow at best in small colonies, as a chain of cells (filament)
or simple structures (thallus). They have life cycles as well as cell
wall structures, carbohydrate reserves and pigments that are unlike those
of the plants. Indeed, some have no cell walls. Only the larger species
(macroalgae) will be treated here.
Brown algae are an almost exclusively marine group. They are multicellular,
often with complex anatomy and morphology. The photosynthetic pigments
include chlorophylls a and c, xanthophylls and carotenes. Most occur
in cooler regions.
sp. (Class Phaeophyceae, Family Dictyotaceae) are found
in most of the larger and less disturbed mangrove areas locally. The
thallus consists of flattened dichotomously branching structures which
often overlap each other. At the mid intertidal zone, on mangrove
tree roots. Rare.
Thallus of Dictyota sp.
Close-up of thallus
of Dictyota sp.
Green algae possess the photosynthetic pigments chlorophylls a and
b, alpha-, beta- or gamma-carotenes and xanthophylls. For storage,
starch is the main product. Members have very similar metabolism to
the plants and are considered by most to be their ancestors.
gracilis (Class Chlorophyceae, Family Cladophoraceae)
France, Mediterranean, Jamaica. Locally, in most areas. Forms loose
balls of filaments on mangrove roots, on mud or as a surface on mud
balls, dirty dark green when wet and bright grass green when dry;
the multi-nucleate cells are cylindrical, joined together as filaments
which bear no rhizoids (root-hair like cells); cell walls are glass-like.
No known economic value. Common. Previously known as Lola gracilis.
filaments of Chaetomorpha gracilis, resembling green glass
Green algae forms
a lawn-like surface
Red algae usually consist of filamentous forms but unlike the other
algae, never possess flagella (a tiny, whip-like organelle for locomotion)
at any stage of their life cycle. Their red colour is due to the pigment
phycoerythrin, but they may be brown, black or purple owing to another
A common species, Catenella
sp. (Class Rhodophyceae, Family Rhabdoniaceae), has a dark
reddish branching thallus which is constricted into segments (resembling
a prickly pear cactus). It grows on muddy substrates and is sometimes
eaten in the Orient, e.g. C. impudica in Myanmar.
Thallus of Catenelia sp.
Habitat of Catenelia sp.