The Abrolhos Reefs of Brazil
87
variability within this species cannot be entirely explained by environmental parameters (Amaral1994).
Among hydrocorals, two of the three species of millepores (Millepora
braziliensis, M. nitida) are considered endemics (Verrill 1868; Laborel
1969a; Amaral1997) while Millepora alcicornis occurs along the entire tropical coast of Brazil and in the Caribbean. Millepores exhibit branching
and encrusting growth forms. Encrusting forms are found on reef tops or
in the axes of gorgonians. Delicate, finger-like branched forms (i.e. Millepora nitida) are characteristics of low energy environments and thick,
massive branched forms (i.e. Millepora braziliensis) of high energy zones.
A small hydrocoral, Sty laster roseus, forms colonies a few centimeters high
with a thick base covered by small pointed branches among branches of
Millepora (Castro 1994). A rare hydrozoan, Solanderia gracilis, thrives in
the deeper and shaded zones of the Abrolhos reefs (Belem et al. 1982).
The 11 octocorals (Phyllogorgia dilatata, Plexaurella grandiflora,
Plauxaurella regia, Muriceopsis sulphurea, Muricea flamma, Neospongodes
atlantica, Lophogorgia punicea, Carijoa risei, Heterogorgia uatumani, Ellisella barbadensis, Ellisella elongata) are among the best-known class of
organisms in the Abrolhos reefs (Castro 1989, 1990a,b). Several species are
considered endemic to Brazil (Phyllogorgia dilatata, Plexaurella grandiflora, Plauxaurella regia, Muricea flam rna, Neospongodes atlantica, Lophogorgia punicea), while Carijoa risei, Heterogorgia uatumani, Ellisella barbadensis and Ellisella elongata also occur on reefs in the North Atlantic.
The abundant Brazilian blade sea fan (Phyllogorgia dilatata) and Plexaurella grandiflora are common in shallow reef areas, characteristically yellow colonies of Muriceopsis sulphurea are frequent among concentrations
of soft algae, Neospongodes atlantica occurs on soft bottoms at the reef
base, and Lophogorgia punicea grows on the walls of Abrolhos reefs. The
four antipatharians (Antipathes three species, Cirripathes one species;
Castro 1994) form flat, fan-shaped colonies, with branches arranged like
brush bristles (Antipathes), or constitute branched colonies up to several
meters long (the wire coral Cirripathes).
6.3.2 Algae
Unicellular symbiont zooxanthellae are found in shallow well-illuminated
waters and an abundant algal flora covers reef bottoms and grows on different reef structures. The abundant calcareous green alga Halimeda is an
important producer of inter-reef sediments, with up to 20% of the coarse
sand fraction around coastal reefs and about 70% of the sediment around
fringing reefs of the Abrolhos Archipelago (Leao 1982). Udotea and Peni-
87
variability within this species cannot be entirely explained by environmental parameters (Amaral1994).
Among hydrocorals, two of the three species of millepores (Millepora
braziliensis, M. nitida) are considered endemics (Verrill 1868; Laborel
1969a; Amaral1997) while Millepora alcicornis occurs along the entire tropical coast of Brazil and in the Caribbean. Millepores exhibit branching
and encrusting growth forms. Encrusting forms are found on reef tops or
in the axes of gorgonians. Delicate, finger-like branched forms (i.e. Millepora nitida) are characteristics of low energy environments and thick,
massive branched forms (i.e. Millepora braziliensis) of high energy zones.
A small hydrocoral, Sty laster roseus, forms colonies a few centimeters high
with a thick base covered by small pointed branches among branches of
Millepora (Castro 1994). A rare hydrozoan, Solanderia gracilis, thrives in
the deeper and shaded zones of the Abrolhos reefs (Belem et al. 1982).
The 11 octocorals (Phyllogorgia dilatata, Plexaurella grandiflora,
Plauxaurella regia, Muriceopsis sulphurea, Muricea flamma, Neospongodes
atlantica, Lophogorgia punicea, Carijoa risei, Heterogorgia uatumani, Ellisella barbadensis, Ellisella elongata) are among the best-known class of
organisms in the Abrolhos reefs (Castro 1989, 1990a,b). Several species are
considered endemic to Brazil (Phyllogorgia dilatata, Plexaurella grandiflora, Plauxaurella regia, Muricea flam rna, Neospongodes atlantica, Lophogorgia punicea), while Carijoa risei, Heterogorgia uatumani, Ellisella barbadensis and Ellisella elongata also occur on reefs in the North Atlantic.
The abundant Brazilian blade sea fan (Phyllogorgia dilatata) and Plexaurella grandiflora are common in shallow reef areas, characteristically yellow colonies of Muriceopsis sulphurea are frequent among concentrations
of soft algae, Neospongodes atlantica occurs on soft bottoms at the reef
base, and Lophogorgia punicea grows on the walls of Abrolhos reefs. The
four antipatharians (Antipathes three species, Cirripathes one species;
Castro 1994) form flat, fan-shaped colonies, with branches arranged like
brush bristles (Antipathes), or constitute branched colonies up to several
meters long (the wire coral Cirripathes).
6.3.2 Algae
Unicellular symbiont zooxanthellae are found in shallow well-illuminated
waters and an abundant algal flora covers reef bottoms and grows on different reef structures. The abundant calcareous green alga Halimeda is an
important producer of inter-reef sediments, with up to 20% of the coarse
sand fraction around coastal reefs and about 70% of the sediment around
fringing reefs of the Abrolhos Archipelago (Leao 1982). Udotea and Peni-