Abstract
This paper shows that the location of the shoreface bank reefs along the northeastern and eastern coasts of Brazil, in a first order approximation, seem to be controlled by the deficit of sediment in the coastal system. The sediment transport pattern defined by a numerical modeling of wave refraction diagrams, representing circa 2000 km of the northeastern and eastern coasts of Brazil, permitted the regional-scale reproduction of several drift cells of net longshore sediment transport. Those drift cells can reasonably explain the coastal sections that present sediment surplus or sediment deficit, which correspond, respectively, to regions where there is deposition and erosion or little/no deposition of sand. The sediment deficit allows the exposure and maintenance of rocky substrates to be free of sediment, a favorable condition for the fixation and development of coral larvae.
Highlights
Coral larvae need a hard and stable substrate onto which they can attach themselves (Woolfe and Larcombe 1999)
Most the shoreface coral reefs from the northeastern and eastern coasts of Brazil are located in areas “under erosion or little/no deposition”
At approximately 7 ky B.P., when zero was cut for the first time (Fig. 3) during the Last Transgression, the coastal sections with sediment deficit must have permitted the exposure of the different types of rock substrates mentioned previously, assuming that, in some locations, these exposures may have been in more elevated positions than the region of the surrounding bottom
Summary
Coral larvae need a hard and stable substrate onto which they can attach themselves (Woolfe and Larcombe 1999). Input of sediments, which cover hard substrates, can be a limiting factor for recruitment (Hubbard 1986, Buddemeier and Hopley 1988, Macintyre 1988, Grigg and Dollar 1990, Rogers 1990, Potts and Jacobs 2002, Babcock and Smith 2002). In this way, the accumulation of sediment covers rocky substrates, which under other conditions, would be adequate for colonization by corals (Larcombe and Woolfe 1999). These reefs are located in depths less than 10 m (Castro and Pires 2001, Leão et al 2003), and their distribution and morphology are controlled by the underlying substrate, such as older reefs, Precambrian bedrock and lines of Quaternary beachrock (Leão et al 1985, 2003)
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