Article & Photos by Gavin W. Maneveldt
DEPARTMENT OF BIODIVERSITY AND CONSERVATION BIOLOGY
UNIVERSITY OF THE WESTERN CAPE
T
he word seaweed is so
commonly used, yet to refer to these marine algae
as ‘weeds’ is very far from
the truth. Together with microscopic algae called phytoplankton
and other photosynthetic organisms, seaweeds are responsible for
all primary production in the
oceans and therefore form the basis of the food chain in the sea.
Although we often cannot smell or
taste them, many ingredients in
our foods and household products
come from the sea and from seaweeds. They are therefore both
directly and indirectly valuable to
humans. Seaweeds assimilate minerals directly from the sea and are
thought to be the single most nutritious foods that you can eat.
Rich in trace elements and vitamins, many of them may frequently contain more protein than meat
and more calcium than milk.
Green Seaweeds
Sea lettuce (Ulva species) as a
whole plant has long been eaten in
the Far East as a green vegetable in
salads and soups. Rich in carotenoids (an antioxidant) of which
beta-carotene is the most popular,
green seaweeds are now known to
help in preventing cancer, heart
disease, and stroke. Recent research efforts have even suggested
that diets high in carotenoids may
Ulva intestinalis (green sea intestines) is a common
green seaweed within the intertidal zone.
be associated with a decreased risk
of breast cancer in women. As
such, beta-carotene is being referred to as the age-fighting antioxidant. Beta carotene, as a natural pigment derived from green
seaweeds, is often also used as a
yellow-orange food colorant in
cheese, coffee creamers, egg substitute, margarine, mayonnaise,
multivitamins, salad dressing, and
many more.
Brown Seaweeds
A characteristic feature of brown
seaweed is that their cell walls are
made of cellulose strengthened by
calcium alginate. Whole brown
seaweeds (not granulated) such as
The brown seaweeds Splachnidium rugosum (dead
man’s fingers) and Aeodes orbitosa (slippery orbits)
are common along the South African west and southern west coasts.