Topographic features related to recent sea level history in a sediment-starved tropical shelf: Linking the past, present and future

Hydroacoustic data were compiled in order to reveal geomorphologic evidences of sea level changes during the last 20 cal kyr BP at the Southern Pernambuco continental shelf (SPCS), Northeast Brazil. Bathymetric surveys were conducted between latitudes −8.71 and −8.98 at depths ranging from 10 to 100 m, covering the entire continental shelf and encompassing an area of 400 km2 that is presently part of a multiple use marine protected area. The bathymetric data set was composed by 102.334 points and the topography was investigated based on: (a) 7 profiles perpendicular to the coastline; (b) a surface generated from a natural neighbor interpolation; (c) contour lines at intervals of 2 m; and (d) 107 cross-sections extracted from the surface generated. This effort allowed the identification of: (a) 5 steps located between depths of 16-20, 20-23, 25-30, 35-40 and 45-50 m and (b) a shelf valley with four topographically distinct segments. These features were interpreted as effects of the sea level changes and provided insights on the evolution of the SPCS. In general, its topography appears to have undergone little changes since the last glaciation. This provides applications that go beyond, and are not restricted, to the fields of science related to the recent geologic past. The preservation of these topographic features means maintaining a heterogeneous relief and therefore the potential for increased biogeodiversity. Shelf valleys are well known fishing grounds among the artisanal fleet. Efforts directed to map the benthic habitats associated to these topographic features may reveal their distribution, fragmentation and connectivity, which could in turn improve tools for fisheries management. This geologic diversity influences processes that affect the local biodiversity, and thus the related goods and services and is very important for researches related to the past, present and future of the continental shelf of the SPCS, a shallow-water sediment-starved environment.