Bottom Plant Associations
151
The most opportunistic among them appeared to be the crustose red alga
Peyssonnelia. The reef flat of frin-ging reefs near Lizard I., being subjected
to wave stress, is covered mostly by periphytonic turfs, composed of minithallomic macrophytes, and with coralline algae (Table 4.15). Among the
dominating macrophyte taxa here were Halimeda opunta, Caulerpa,
Laurencia, Amphiroa. At the leeward side of the reef flat algae were
dominating which prefer calm waters, such as Halimeda cavernosa, Boodlea,
Dictyosphaeria. The domination of seagrasses and thallomic macrophytes in
calm lagoonal biotopes and the key role of red corallines in turbulent zones
of reef crest and outer slope could also be seen from data on the relative
projective cover of the bottom surface by main groups of benthic plants
(Tables 4.15, 4.16).
Another example of zonal distribution of benthic algae could be seen at
the cross section through the reef zones of the Diego Garcia stoll in the
Indian Ocean (Rhyne 1971). On the sand bottom of the littoral zone of the
lagoon, with an admixture of rubble and dead corals, the phytocoene
included the macrophytes Enteromorpha, Giffordia, Dictyota, Pocockiella,
Hypnea, and Halimeda. The rubble stripes and ridges were occupied
by Microcoleus and Padina. At the coastal patch reefs Cladophora,
Cryptonemia, Valonia, Botriocladia, Caulerpa, Bryopsis, Codium and
Galaxaura were the most numerous, while at the lagoonal patch reefs
Valonia, Dictiosphaeria, Caulerpa, Acetabularia, and Cymodocea. On
thalloms of Cymodocea the epiphytes Sphacelaria furcigera, Amphiroa
fragillissima, Jania ten ella and Campia parvula were abundant. The sandy
bottom in the central part of the lagoon was dominated by Halimeda. The
coral heads, the tridacna shells and large pieces of rubble were colonized by
Sargassum, Turbinaria, Padina, Jania, Galaxaura, Dictyota. The reef flat,
powdered with sand, was covered with dense algal turf, composed of
filamentous blue-green and green algae, the mini-thallomic macrophytes
Dictiosphaeria, Boodlea, Gelidiella, Laurencia, and Heterosiphonia, and of
the coralline alga Jania. On the rocky surfaces of the reef flat blackish-green
hillocks were numerous. They were formed by the blue-green algae
Rivularia, Microcoleus and Shizotrix. The trenches in the surface of the flat
were occupied by Halimeda. On the windward edge of the reef flat, stressed
by surf, crustose corallime algae were dominating. Among them were
Porolithon, Neogoniolithon, Sporolithon, Lithophyllum, and Hydrolithon.
The above-listed Corallinaceae are a basic element of phytocoenes in the
surf zones of reefs. Their crustose colonies sustain a severe wave-stress. But
even among them there are species with definite ecological adaptations
which occupy their own niches, where they are dominating. The most
opportunistic species of crustose corallines is Porolithon oncoides, which
endures direct sunlight, long exposure and over-heating (Fig. 4.4). This
species forms firm thick hill-shaped colonies which are subjected to a most
powerful surf. Inhabiting the surf zone this alga escapes grazing by fish
(Adey 1975). This species usually dominates among the crustose corallines
151
The most opportunistic among them appeared to be the crustose red alga
Peyssonnelia. The reef flat of frin-ging reefs near Lizard I., being subjected
to wave stress, is covered mostly by periphytonic turfs, composed of minithallomic macrophytes, and with coralline algae (Table 4.15). Among the
dominating macrophyte taxa here were Halimeda opunta, Caulerpa,
Laurencia, Amphiroa. At the leeward side of the reef flat algae were
dominating which prefer calm waters, such as Halimeda cavernosa, Boodlea,
Dictyosphaeria. The domination of seagrasses and thallomic macrophytes in
calm lagoonal biotopes and the key role of red corallines in turbulent zones
of reef crest and outer slope could also be seen from data on the relative
projective cover of the bottom surface by main groups of benthic plants
(Tables 4.15, 4.16).
Another example of zonal distribution of benthic algae could be seen at
the cross section through the reef zones of the Diego Garcia stoll in the
Indian Ocean (Rhyne 1971). On the sand bottom of the littoral zone of the
lagoon, with an admixture of rubble and dead corals, the phytocoene
included the macrophytes Enteromorpha, Giffordia, Dictyota, Pocockiella,
Hypnea, and Halimeda. The rubble stripes and ridges were occupied
by Microcoleus and Padina. At the coastal patch reefs Cladophora,
Cryptonemia, Valonia, Botriocladia, Caulerpa, Bryopsis, Codium and
Galaxaura were the most numerous, while at the lagoonal patch reefs
Valonia, Dictiosphaeria, Caulerpa, Acetabularia, and Cymodocea. On
thalloms of Cymodocea the epiphytes Sphacelaria furcigera, Amphiroa
fragillissima, Jania ten ella and Campia parvula were abundant. The sandy
bottom in the central part of the lagoon was dominated by Halimeda. The
coral heads, the tridacna shells and large pieces of rubble were colonized by
Sargassum, Turbinaria, Padina, Jania, Galaxaura, Dictyota. The reef flat,
powdered with sand, was covered with dense algal turf, composed of
filamentous blue-green and green algae, the mini-thallomic macrophytes
Dictiosphaeria, Boodlea, Gelidiella, Laurencia, and Heterosiphonia, and of
the coralline alga Jania. On the rocky surfaces of the reef flat blackish-green
hillocks were numerous. They were formed by the blue-green algae
Rivularia, Microcoleus and Shizotrix. The trenches in the surface of the flat
were occupied by Halimeda. On the windward edge of the reef flat, stressed
by surf, crustose corallime algae were dominating. Among them were
Porolithon, Neogoniolithon, Sporolithon, Lithophyllum, and Hydrolithon.
The above-listed Corallinaceae are a basic element of phytocoenes in the
surf zones of reefs. Their crustose colonies sustain a severe wave-stress. But
even among them there are species with definite ecological adaptations
which occupy their own niches, where they are dominating. The most
opportunistic species of crustose corallines is Porolithon oncoides, which
endures direct sunlight, long exposure and over-heating (Fig. 4.4). This
species forms firm thick hill-shaped colonies which are subjected to a most
powerful surf. Inhabiting the surf zone this alga escapes grazing by fish
(Adey 1975). This species usually dominates among the crustose corallines