90
Z.M.A.N. Leao and R.K.P. Kikuchi
blue-faced booby (Sula dactylatra) and brown booby (S. leucogaster), the
frigate bird (Fregata magnificens), the sooty tern (Sterna fuscata), the
brown noddy (Anous stolidus), and the red-billed tropic bird (Phaeton
aethereus) nest on the islands of Abrolhos and migrating birds are attracted to this area for resting and feeding.
6.4 Reef Types
Brazilian coral reefs display distinct forms of growth and morphology.
Although vaguely comparable to algal cup reefs of Bermuda and algal ridges in the southwestern Caribbean, the mushroom-like growth forms of
the Abrolhos coral reefs represent an unique ecological system. The
Coastal Arc (about 10-20km offshore) of Abrolhos reefs is formed by isolated coral pinnacles and different-sized bank reefs, while the Outer Arc
(about 70 km offshore) to the east of the Abrolhos Islands is formed by isolated giant coral pinnacles (Figs. 6.1A, 6.3).
6.4.1 Coastal Arc
Abrolhos reefs are coral pinnacles or "chapeiroes" (Hartt 1870) of irregular shape and laterally expanding tops. They are mushroom-shaped,
roughly circular or, less often, elongate, and with overhangs often more
pronounced at the windward side. They may vary between about 1-25m in
height and 1-50m across the top. The mushroom-like growth results from
the death of the upper part of parent corals, therefore directing new
growth towards the edge of the colony. Lateral growth is enhanced when
reef columns reach the sea level. Where closely spaced, pinnacles can fuse
at the top, forming large bank reefs (Fig. 6.3A,B). For example, the 17-kmlong Pedra Grande Reef of the Parcel das Paredes is a result of coalescence
between numerous pinnacles and filling of open spaces at the upper reef
with biogenic sediment, though narrow channels are still open at deeper
parts. In consequence, coastal reefs of Abrolhos do not form classical barrier reefs, instead they are isolated shallow bank reefs of different shapes
and sizes. Owing to patchiness, reduced dimensions, and position on the
shelf, back reef zones and fore reef slopes are absent.
The reef top, located between about 10-m depths and low water levels, is
the upper part of a pinnacle or a bank reef. Photophile forms of massive
corals (Mussism ilia braziliensis and Favia leptophylla), small colonies of
Porites, hydrocorals (i.e. Millepora), and gorgonians (i.e. Plexaurella regia)
Z.M.A.N. Leao and R.K.P. Kikuchi
blue-faced booby (Sula dactylatra) and brown booby (S. leucogaster), the
frigate bird (Fregata magnificens), the sooty tern (Sterna fuscata), the
brown noddy (Anous stolidus), and the red-billed tropic bird (Phaeton
aethereus) nest on the islands of Abrolhos and migrating birds are attracted to this area for resting and feeding.
6.4 Reef Types
Brazilian coral reefs display distinct forms of growth and morphology.
Although vaguely comparable to algal cup reefs of Bermuda and algal ridges in the southwestern Caribbean, the mushroom-like growth forms of
the Abrolhos coral reefs represent an unique ecological system. The
Coastal Arc (about 10-20km offshore) of Abrolhos reefs is formed by isolated coral pinnacles and different-sized bank reefs, while the Outer Arc
(about 70 km offshore) to the east of the Abrolhos Islands is formed by isolated giant coral pinnacles (Figs. 6.1A, 6.3).
6.4.1 Coastal Arc
Abrolhos reefs are coral pinnacles or "chapeiroes" (Hartt 1870) of irregular shape and laterally expanding tops. They are mushroom-shaped,
roughly circular or, less often, elongate, and with overhangs often more
pronounced at the windward side. They may vary between about 1-25m in
height and 1-50m across the top. The mushroom-like growth results from
the death of the upper part of parent corals, therefore directing new
growth towards the edge of the colony. Lateral growth is enhanced when
reef columns reach the sea level. Where closely spaced, pinnacles can fuse
at the top, forming large bank reefs (Fig. 6.3A,B). For example, the 17-kmlong Pedra Grande Reef of the Parcel das Paredes is a result of coalescence
between numerous pinnacles and filling of open spaces at the upper reef
with biogenic sediment, though narrow channels are still open at deeper
parts. In consequence, coastal reefs of Abrolhos do not form classical barrier reefs, instead they are isolated shallow bank reefs of different shapes
and sizes. Owing to patchiness, reduced dimensions, and position on the
shelf, back reef zones and fore reef slopes are absent.
The reef top, located between about 10-m depths and low water levels, is
the upper part of a pinnacle or a bank reef. Photophile forms of massive
corals (Mussism ilia braziliensis and Favia leptophylla), small colonies of
Porites, hydrocorals (i.e. Millepora), and gorgonians (i.e. Plexaurella regia)