Thin layer detection by an autonomous underwater vehicle in a coastal ecosystem: the ECOAUV Project

Abstract

Thin layers are oceanographic features comprised by aggregations of suspended particulate matter and plankton retained in dense concentrations within a small vertical thickness (usually < 3 m). Such structures are characterized as hot spots of biogeochemical activity in stratified oceans, but there are no studies on their occurrence and persistence in coastal ecosystems of the southern hemisphere. Thin layers are difficult to detect using traditional sampling techniques. In the present project, last-generation sensors will be used to evaluate physical, chemical and bio-optical properties relevant for thin layer detection. Oceanographic sensors will be embedded into the AUV Pirajuba, which is an autonomous underwater vehicle, developed by the Unmanned Vehicles Laboratory in the Mechatronics Engineering department of the University of São Paulo. Monthly, the AUV will perform pre-programmed manoeuvres in the north coast of São Paulo (Ubatuba). It will perform transversal paths to the coast, oscillating in the dive plane between the surface and a distance close to the sea bed. The AUV speed will be set so that the sensors can capture the water oceanographic properties at the required resolution for the thin layer study. A special structure, attached to the AUV, will carry a holographic camera for the detection of microorganisms. This project will have a significant effect on the knowledge about these types of oceanographic features, that have little knowledge worldwide. However, they are very important for the understanding of coastal biochemical processes. (AU)