Monitoring the Growth of Coastal Algae Blooms in Harsh Weather Conditions using a Wave-Propelled ASV: Challenges and Lessons Learned

This article presents the experience gathered on a 19-day-long field campaign with the wave-propelled, solar-powered, autonomous surface vehicle AutoNaut. The operation was conducted in Frohavet, a semienclosed sea along the Atlantic coast of Central Norway, as part of a larger field exercise. The objective of the exercise was to observe and quantify the growth and development of algae blooms in the area. The main scientific objective assigned to the autonomous surface vehicle was to monitor in situ the levels of chlorophyll-a fluorescence and solar radiation on the sea surface. Several challenges, mainly caused by the harsh weather conditions, are described and discussed. A risk assessment and safety procedures for the crew and the equipment involved are listed so as to provide a starting point for future operations of this kind. The operations in Frohavet lasted for 19 days until a system failure led to the grounding of the vehicle. Although a bloom was not observed during the period of deployment, valuable experience on how to enhance the in situ situational awareness and how to improve the navigation capabilities of the vehicle was gathered. The material presented aims to serve as guidance for future operations, helping the operators to avoid committing the same (or similar) mistakes and further improving the autonomy of the vehicle by establishing a standard operational procedure, thereby improving the vehicle's ability to carry out such missions in the future.