Developing an autonomous surface vehicle for measuring marine surfactants at the Ocean-River Interface System

The top few millimeters of the ocean, where properties are most altered relative to deeper water, are often referred to as the sea surface micro-layer (SML). This thin layer holds properties and dynamics that differ considerably from the deeper ocean, and it is where a great variety of interactions between physical, chemical, biological and photochemical phenomena take place. Due to extreme conditions at the air-sea interface, the sea surface is believed to be the place where life on planet Earth has originated. The micro-layer is involved in the heat and momentum transfer between the ocean and atmosphere and plays a vital role in the uptake of greenhouse gases by the ocean. Furthermore, knowledge of the structure and composition of the micro-layer, including their surface active materials, i.e. surfactants, that are associated to surface films, and the complex biological community that lives there, is vital to understand the role of the micro-layer in the environment and climate. Despite of an enormous difficulty to conduct in situ observations of surface films, these became indispensable to characterize the properties of the micro-layer. Chemical and/or biological analyses of the surface micro-layer are usually conducted on a punctual basis, on seagoing platforms or at the margin of water, through the sampling of thin layers of surface water utilizing traditional collectors, such as metallic plates, glass blades, nylon nets, or rotating drums. The results of using any of these methods vary in different levels of contamination, due to both sub-surface water and vessel pollutions.

The objective of this project is to develop a modular autonomous surface vehicle (ASV), having the capability to sample the SML, and consequently, perform analysis of surfactant films and the biological communities residing within the micro-layer. This will be a unique vehicle in Portugal, and one of the first control-autonomous vehicles in the world to perform micro-layer sampling procedures. The vehicle will be able to interact and sample the micro-layer simultaneously with other underwater autonomous vehicles and airborne autonomous vehicles. This proposal integrates strong technological and scientific components, from conception to validation of the sampling and navigation systems. The scientific and engineering synergy of this project provides opportunities to use the vehicle in two specific study cases: a coastal study (the Douro River plume, in the Northwest of Portugal) and an estuarine study (Ria de Aveiro lagoon). With these we intend to validate the methods and observational requirements previously defined by the scientific and engineering partnership. The long term overall objective will be  herefore to contribute to a better knowledge of surfactant films formed in the interface of riverine and coastal waters (Douro River plume), as well as to enhance our knowledge of bacteria and viruses biodiversity in the Ria Aveiro Lagoon.