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ABSTRACT.The study area is located off the southern coast of Pernambuco state, northeastern Brazil. The morphology of the inner continental shelf was investigated by means of twenty bathymetric profiles obtained with an echosounder GARMIN GPSMAP 185 Sounder. The surveyed area is an Environmental Protection Area (APA) called Coral Coast that is characterized by the occurrence of submerged beachrocks found at 16, 20 and 22 m depth, and a paleochannel with an N-S orientation.These morphological features are related with the coastal evolution of the southern Pernambuco continental shelf during Holocene sea-level variations and their description and location will be useful in future works concerning ancient conditions of sea-level stability. Mapping of submerged beachrocks contributes, as well, to the biodiversity conservation initiatives and the national and global coral reef monitoring programs.

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The Northeastern Brazil Continental Shelf (NEBCS) is one of the largest shelves off the Brazilian coast, and it is strongly influenced by volcanic and tectonic processes. It can be divided in three portions: Inner shelf (limited by 20 m isobaths), Mid-shelf (from 20 to 40 m depth), and Outer shelf (beyond 40 m depth). Pernambuco is one of the nine States from the Northeast region of Brazil, comprising a coast line of 187 Km (from 07°37.71'S to 08°54.34'S) and an average width of 33.28 Km. The littoral zone is strongly influenced by urban development, with extreme pollution in some areas, particularly near the capital Recife and the metropolitan region. Nevertheless, there are two Marine Protected Area (MPA) included in the Pernambuco EEZ, namely "Fernando de Noronha Archipelago" and "APA Costa dos Corais". However, there have been no habitat mapping studies within this region of the continental shelf, and only a small number along Brazilian coast. Based on the limited information available, the present work aimed to initiate the compilation of existing seafloor data sets on the Pernambuco region. The main objective was to map the physiography and relate it with the classes of sediment, providing a map of the geodiversity from the coast of Pernambuco (from inner to outer shelf). To achieve the objectives of the study, abiotic data available in a public database, and results of technical-scientific surveys from the area were explored. Specifically, topography, slope, and sedimentary texture data were integrated. The topography was based on Gorini (1996). The map curvature was generated on ArcMap 10.1 software. Folks' classes were used to classify the sediment and stations were interpolated by natural neighbor. To improve the information for the locality, data from the Brazilian National Oceanographic Data Bank (BNDO) was added. Thus, a total of 314 samples were accomplished for the analyses. Multidimensional and PCA analyses were conducted using PRIMER 6. Results of bathymetric analysis suggested some considerations: Inner and Outer shelf are narrow in the south and broaden northward along the shelf. On the other hand, the Mid-shelf is a broad southward and narrow at North portion. The slope is variable, being possible to observe several long portions with low degree (0.8-1°) of steepness along the Inner shelf. The presence of steps toward Mid-shelf could be observed as well. A flat portion is registered at the southern part of the shelf. Irregular areas are shown toward North. Pernambuco's platform presents its edge between 55-65 m, revealing an extended stability of the continental shelf, in terms of tectonic and sedimentary processes. The abrupt gradient variation of the shelf edge is clearly marked, as well as the strong steepness on superior slope. Additionally, the MDS and PCA analyses reflect the influence of terrigenous sediment, coming from continental region for the Inner shelf, and the presence of calcareous algae plus organogenic fragments (from beach-rocks and corals) on the mid and outer shelf. The sediment composition is highly relevant to the benthos distribution. Based on our results a texture map was constructed showing the general pattern for the sediment distribution along the shelf of Pernambuco.

The Eastern Brazilian Continental Shelf (EBCS) is narrow, shallow and predominantly covered by biogenic sediments. Bathymetric surveys have revealed the common occurrence of submerged channels, related to the largest watersheds in the region and probably carved during periods of marine regression. With its break located between 40 and 80 metres deep, the EBCS was subjected to sub-aerial erosion for long periods, which justifies the occurrence of these erosive features related to continental drainage. Based on a DEM with spatial resolution of 10 metres, the slope values of a section of the continental shelf of the state of Pernambuco were extracted. This initiative indicated an average slope value of 0.38°, consistent with that expected for a continental shelf. However, along the edges of three submerged channels the slope is more pronounced, with values generally between 3 and 45°. Therefore, in order to verify the characteristics of these steep reliefs, 03 video-transects were performed in two sectors of the Zieta Channel with a GoPRO 3 Black. Video-transects I and II were situated about 18 kilometres off the coast, while video-transect III was about 30 kilometres. The data analysis involved the integration of the three parameters: substrate, geomorphology, and biota. The seascapes in each video-transect were defined such as: predominant, secondary or occasional. The record of combinations of substrate characteristics, geomorphology and biota occurrences also contributed to the definition of an associative pattern between the physical characteristics and the biological assemblages recorded. Extreme values of slope (20-45°) are related to seascapes dominated by large rocky outcrops, cut by small channels and with relative structural complexity, as well as fish, sponges, algae and corals. On the other hand, values of slopes between 3 and 8°, composed seascapes dominated by small rocky outcrops, with irregular surface, usually covered by algae, and seascapes dominated by sub-outcrops, associated with rocky bottoms, sponges and corals. The flat reliefs (0-3°), related to the thalweg, harboured seascapes dominated by unconsolidated substrates, with bioturbation and occurrence of dense spots of algae of the genus Halimeda. From these preliminary results, it can be suggested that the slope presented potential to be considered a surrogate for seascapes dominated by consolidated substrates and associated reef environments. This potential should be better investigated through new video surveys, contributing greatly to the consolidation of this relationship between slope, seascapes and benthic habitats, which, in turn, may guide the most appropriate design of Marine Protected Areas, as well as management measures of their fishing resources.