Mapping of benthic habitats of the Abrolhos Bank

Abstract

The Abrolhos Bank, located on the Eastern Brazilian coast, shelters one of the highest marine biodiversities of the South Atlantic Ocean. It is home to an endemic hermatypic coral fauna, serving also as a breeding ground for humpback whales. Conservation and sustainable management issues are in the agenda since land use by homeowners, industry and agriculture is rapidly increasing. The present proposal aims to map the seafloor of the Abrolhos Bank on two distinct scales: regional and local. This proposal is within the framework of the project "Productivity, sustainability and utilization of the Abrolhos Bank Ecosystem" (PROABROLHOS - CNPq/Institutos do Milênio). PROABROLHOS will support ship and air fare costs, as well as the acquisition of a remotely operated vehicle (ROV). ROV video transects will be used to map seabed features and track benthic organisms. During the mesoscale study, samples will be collected in 18 stations on board R.V. Prof. W. Besnard of the Oceanographic Institute of the University of São Paulo. The stations form an equally spaced grid over the bank, approximately 20 nautical miles apart from each other. Small scale samples will be collected using a small trawling boat in two different reefs (one coastal and another with oceanic characteristics, farther from coastal influence). On each reef 12 stations will be sampled in 4 transects positioned in four different points around the reef. Otter trawl samples will be taken right after video transects in order to collect the megafauna. These animals will be compared with the fauna present in video transect to validate identification. Extra video transects will be conducted outside the bank and on the seamount chains where depths do not exceed 150 meters (ROV maximum operation depth). The regional mapping will also be assessed by satellite image digital processing over the study area. IKONOS high spatial resolution and Landsat medium spatial resolution images, respectively, will be georeferenced, segmented and classified at the Earth Observation Coordination (OBT), National Space Research Institute (INPE). The thematic classification obtained will be statistically compared with in situ data. The satellite images and the thematic maps will compose a geographic data bank in a Geographical Information System (GIS) environment. Additionally, a whale fall experiment will be carried out, since whale fall habitats are likely to be common in the area and may play an important role in the Abrolhos Bank ecosystem. Whale carcass and bones will be obtained in collaboration with the Humpback Whale Institute located at Caravelas, Bahia. The current proposal will also benefit from oceanographic and satellite data collected quasi-simultaneously by several researchers from IOUSP and other state and federal institutions. This research will probably provide the best picture of the structure and functioning of the Abrolhos Bank ecosystem ever produced. (AU)