Underwater hyperspectral imagery for Posidonia oceanica mapping: challenges and preliminary results from the POSEIDON Project

Abstract. Posidonia oceanica (PO) meadows are important ecosystems in the Mediterranean, supporting biodiversity and ecosystem services, yet they face increasing threats due to anthropogenic pressures and climate change. To address these challenges, the POSEIDON project aims to develop ultra-high-resolution (UHR) and beyond ultra-high-resolution (BUHR) mapping methods for PO monitoring. This study focuses on underwater hyperspectral imagery (UHI) as a tool to complement and support the standard monitoring protocols established by ISPRA. Data were collected along the northern coast of Sardinia, with hyperspectral acquisitions performed both underwater, at depths of 5–15 meters, and out of the water, over collected samples, using a Senop Rikola hyperspectral camera. The study faced several challenges, including image blurring due to the movement of seagrass and light absorption by water, which limits the effectiveness of infrared bands. Despite these difficulties, the preliminary tests provided valuable insights into the system's limitations and suggested improvements for future data acquisition. This paper outlines the methodology, presents initial results, and discusses strategies to enhance underwater hyperspectral data quality for future monitoring efforts.