B. Ecological Parameters Influencing the
Distribution of Present-Day Coralline Algal
Encrusting coralline algae are predominantly restricted to
marine waters. Only a few species can live in waters with low or
high salinity, respectively.
The single species are mostly stenohaline,
which means that they show low tolerance for variation in salinity
Light / Depth
Due to their red pigments, coralline algae use the
light spectrum for photosynthesis. Therefore, they can live in
deeper waters than most other algae and are abundant in shallow water
Coralline algae are known from intertidal pools
down to 258 m water depths! But the typical limits in tropical
environments are ca. 80 m and in colder environments ca. 20 - 40 m.
Many species can occur in a wide depth range, but several species show
restricted depth (i. e., light) distributions.
Obviously, it is not the depth as such that influences the distribution
of algae. Those species which prefer low-light conditions can occur in
greater depths - but they can also occur in cryptic shallow-water
environments, such as reef caves. Finally, the water turbidity influences
the penetration of light and therefore influences the depth distribution
Read more about photosynthesis
at the Smithonian
Climate / Temperature
Coralline algae occur in a wide
temperature range. They are known from tropical to arctic/antarctic
environments and tolerate temperatures down to >0°!
Some trends seem to be recognizable. For example, the
genus Phymatolithon is most prominent in non-tropical environments
and some say that Sporolithon is more typical for warm waters (see
the list of taxa for informations on
One of the great competitional advances of coralline algae
is that they can occur in very low to extremely high
They cannot occur in stagnant waters, because a certain
hydrodynamic energy is required for the delivery of nutrients and the
removal of photosynthetic products.
Due to calcified cell walls and heavy cementation to hard
substrate, they can live in extremly high energetic environments, such as
reef crests. The great advantage is that the high energy keeps away other
macroalgae and grazing animals, such as gastropods.
Hydrodynamic energy is also responsible for the turning of
rhodoliths (but: see below), which is crucial for the growth into all
directions, as well as for the formation of maerl. However, if the energy
is too high, the algal thalli are obviously fragmented and destroyed.
Studies on relations between water
motion and rhodolith movement are studied at the Moss
Landing Phycology Lab.
Several studies showed that turning
of rhodoliths is not only caused by hydrodynamic energy, but
frequently by the activities of food searching animals, such as fishes.
Another aspect of biotic interactions is
competition. Fleshy macroalgae, such as brown algae, can grow much
faster than calcified coralline algae and therefore should have a
particular advantage with respect to space competition. However, coralline
algae can deal with this problem in several ways. On the one hand,
corallines can occur in high energetic environments which are not suitable
for fleshy macroalgae (see above); on the other, the grazing activities of
animals removes the fleshy algae, but hardly affect the coralline algae,
which are protected from grazing by calcified cell walls. Moreover,
corallines can live under low light conditions. This implies that they may
receive sufficient light for photosynthesis even when they are shaded by
overgrowing fleshy algae.
Read more about space
competition within corallines and about grazing
effects at the homepage
of Derek Keats.
Or read about sea
urchins in rhodolith beds and kelp
canopy shading (Moss
Landing Phycology Lab)
Coralline algae occur on hard and soft substrates.
On hard substrate they can
form simple crusts and reef-type buildups.
Stable soft substrate, such
as sand, causes partial encrustations of clasts, such as coral or mollusc
fragments and frequently uni-directional coralline algal growth. This is
because the encrusted bioclasts are stabilized and are not turning in
order to allow rhodolith formation. The Mediterranean Coralligene de
Plateau frequently forms on stable soft substrate.
Instable soft substrate
enables the formation of rhodoliths, because the corallines can grow into
all directions. It also enables the formation of maerl.
Muddy substrate is highly
unfavorable for coralline algae, except there are bioclasts to be
encrusted. In contrast to some peyssonneliacena red algae, coralline algae
seem unable to grow directly on mud.