py-forming organisms and quite
often more than 60% of the total
kelp biomass in a typical kelp community is made up by the surfacereaching plants. These canopyforming plants are the ones that
utilise much of the available sunlight that strikes the water’s surface. The remaining percentage of
kelp, as well as a huge diversity of
other macroscopic algae, comprises
the sub-canopy or understorey and
the ground-dwellers. These latter
algae survive in a dim world overshadowed by the canopy, very
much like that which exists in a typical terrestrial forest. In addition, a
host of epiphytic algae also exist in
the kelp community. Depending on
where these epiphytes are found (in
the canopy, along the stipes of canopy- or sub-canopy-forming plants,
in the understorey), they in turn
receive as much light as that which
reaches their particular locations.
More than 0.5 hectares
0.5 hectares is equivalent to 0.005
km2, or 5000 m2. In its most practical sense, this would equate to an
area 50 m in width by 100 m in
length. This really is not large at all.
Among other factors, kelp plants
are limited by available rocky substrate to which they can attach.
This means that should the environment be conducive and enough
rocky shore environments exist, kelp
beds can stretch for several kilometres alongshore, and several hundreds of metres out to sea.
much reduced, secondary blades
elongate and these then form the
bulk of the apical mass.
South African kelp species
Due to its unique geographic location (both longitudinal and latitudinal), and the presence of two interacting ocean currents (the cold Benguela Current on the west and
warm Agulhas Current to the east),
South Africa is the only country that
is home to all three (Ecklonia, Laminaria, Macrocystis) of the major
kelp genera (of which 30 are currently recognized). Within these
genera, four species of kelp are represented in South Africa.
While Ecklonia maxima is the dominant kelp along inshore waters of
the West Coast, this species becomes progressively replaced by the
Split-fan Kelp (Laminaria pallida
also known as Waaierkelp and
Waaier Seebamboes) in deeper waters and also further north up the
West Coast and into Namibia. The
species has a similar distribution to
E. maxima and is similarly large,
attaining lengths to 10m. In L. pallida the stipe can be solid or hollow, but without a bulb at its distal
end. Due to the absence of a gasfilled bulb and mostly solid-stiped
plants around the Cape Peninsula,
this species is generally a subtidal
(subcanopy) species and so is seldom observed along the low shore
intertidal zone. This kelp has a single broad, fan-shaped blade that
becomes dissected into many regular longitudinal tears (or splits) giving the false impression of being
multiple-bladed; hence its common
name. Adult plants of L. pallida also
differ from those of E. maxima in
that they have warty stipes as opposed to the smooth stipes of E.
maxima.
Sea Bamboo or Seebamboes
(Ecklonia maxima) is the most
abundant of the four species and
occurs along the cold temperate
west and southern west coasts,
dominating the inshore waters of
the west coast. The species is the
largest of the local kelps attaining
lengths up to 15 m. This kelp plant
possesses a massive holdfast that
extends into a long, hollow, gasfilled stipe that ends in a gas-filled
bulb (float) at its apex. The bulb
further extends into a single flat,
solid primary blade from which secondary blades emerge. In juvenile
kelp, the primary blade is very elongated and bears only short secondary blades. As the plants mature,
the primary blade becomes very
Macrocystis pyrifera generally occurs in sheltered,
shallower water, inshore of E. maxima and L. pallida
beds.
Generally found in shallow, somewhat sheltered water inshore of E.
Laminaria pallida dominates in deeper waters and
also further north up the West Coast and into Namibia.