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Z.M.A.N. Leao and R.K.P. Kikuchi
6.3 Reef Organisms
6.3.1 Corals
The Brazilian coral fauna displays low diversity, lacks branching acroporids common to most Atlantic reefs, and major reef builders are endemics
and evolved from an isolated coral fauna of the Tertiary (Leao 1982). This
situation may have been caused either by the west and northward flow of
the Equatorial Current, which impedes the dispersion of the planula larval
stage of many modern Caribbean coral species, or by the environmental
characteristics of Brazilian reef areas. Despite optimal temperature, salinity and water depth for a diverse coral fauna in Abrolhos reefs, a stressful
light regime, owing to high water turbidity in winter, and deposition of siliciclastic sediments may have deterred the establishment of most Caribbean coral species but not the growth of endemic reef-building species.
While all ahermatypic Abrolhos reef corals are related to Caribbean species, most hermatypic frame-building corals tend to be endemic species
(Verrill1868; Laborel1969a,b; Castro 1994). Of the 17 stony corals (scleractinians) in Abrolhos (18 Brazilian species), the common Mussismilia hispida, Mussismilia braziliensis, Mussismilia harttii, Favia leptophylla, Favia
gravida and Siderastrea stellata are endemics. Mussismilia braziliensis is
restricted to the coast of Bahia State and Mussismilia hispida occurs between 3° S and 30° S. Several species have large corallites, like Mussismilia
braziliensis, M. harttii, M. hispida, Favia leptophylla and Montastrea
cavernosa, the first two being important Abrolhos reef framebuilders.
Owing to self-cleaning mechanisms, corals with large polyps generally
tend to be more resistant to sedimentation and stressful light (Fishelson
1973; Dodge et al. 1974; Rogers 1990), and thus may favor development of
hermatypic corals and the growth and calcification of the reef under these
conditions. Cosmopolitan species (Porites astreoides, Porites branneri,
Agaricia agaricites, Agaricia fragilis, Montastrea cavernosa, Madracis
decactis) play a secondary role in the construction of Abrolhos reefs and
several small and rare corals (Scolymia welsii, Phyllangia americana,
Astrangia braziliensis, Stephanocoenia michelini) are insignificant reef
builders. Most frame-building corals from Brazilian reefs have massive and
encrusting forms. Branching forms, which are dominant on reef crests and
fore reef slopes of most North Atlantic reefs, are absent from Abrolhos
reefs, though Mussismilia harttii exhibits dichotomous groups of corallites. The shallow water forms of Montastrea cavernosa tend to be hemispheric, becoming fringed forms at depths greater than 5 m, and eventually flattened and encrusting in even deeper waters. However, morphological
Z.M.A.N. Leao and R.K.P. Kikuchi
6.3 Reef Organisms
6.3.1 Corals
The Brazilian coral fauna displays low diversity, lacks branching acroporids common to most Atlantic reefs, and major reef builders are endemics
and evolved from an isolated coral fauna of the Tertiary (Leao 1982). This
situation may have been caused either by the west and northward flow of
the Equatorial Current, which impedes the dispersion of the planula larval
stage of many modern Caribbean coral species, or by the environmental
characteristics of Brazilian reef areas. Despite optimal temperature, salinity and water depth for a diverse coral fauna in Abrolhos reefs, a stressful
light regime, owing to high water turbidity in winter, and deposition of siliciclastic sediments may have deterred the establishment of most Caribbean coral species but not the growth of endemic reef-building species.
While all ahermatypic Abrolhos reef corals are related to Caribbean species, most hermatypic frame-building corals tend to be endemic species
(Verrill1868; Laborel1969a,b; Castro 1994). Of the 17 stony corals (scleractinians) in Abrolhos (18 Brazilian species), the common Mussismilia hispida, Mussismilia braziliensis, Mussismilia harttii, Favia leptophylla, Favia
gravida and Siderastrea stellata are endemics. Mussismilia braziliensis is
restricted to the coast of Bahia State and Mussismilia hispida occurs between 3° S and 30° S. Several species have large corallites, like Mussismilia
braziliensis, M. harttii, M. hispida, Favia leptophylla and Montastrea
cavernosa, the first two being important Abrolhos reef framebuilders.
Owing to self-cleaning mechanisms, corals with large polyps generally
tend to be more resistant to sedimentation and stressful light (Fishelson
1973; Dodge et al. 1974; Rogers 1990), and thus may favor development of
hermatypic corals and the growth and calcification of the reef under these
conditions. Cosmopolitan species (Porites astreoides, Porites branneri,
Agaricia agaricites, Agaricia fragilis, Montastrea cavernosa, Madracis
decactis) play a secondary role in the construction of Abrolhos reefs and
several small and rare corals (Scolymia welsii, Phyllangia americana,
Astrangia braziliensis, Stephanocoenia michelini) are insignificant reef
builders. Most frame-building corals from Brazilian reefs have massive and
encrusting forms. Branching forms, which are dominant on reef crests and
fore reef slopes of most North Atlantic reefs, are absent from Abrolhos
reefs, though Mussismilia harttii exhibits dichotomous groups of corallites. The shallow water forms of Montastrea cavernosa tend to be hemispheric, becoming fringed forms at depths greater than 5 m, and eventually flattened and encrusting in even deeper waters. However, morphological