InterSeA: An Unmanned Surface Vehicle (USV) for Monitoring the Marine Surface Microlayer (SML) in Coastal Areas

The sea surface microlayer (SML) is a critical biogeochemical boundary, playing a key role in air–sea exchange processes, yet its sampling remains challenging due to potential dilution from subsurface water layers, susceptibility to contamination and labor- and time-consuming procedures. The design, development and operational verification of a research unmanned surface vehicle (USV), equipped with samplers for collecting both sea surface microlayer and subsurface water samples (SSW), are described in this study. The InterSeA autonomous vessel is of the catamaran type, equipped with an SML sampler consisting of rotating glass discs and a peristaltic pump for collecting SSW samples. Verification analysis with traditional manual sampling techniques (glass plate and mesh screen) revealed that the InterSeA achieved comparable results in terms of reproducibility and contamination control for both the inorganic and organic analytes examined. The results obtained highlight the effectiveness of autonomous platforms in achieving reliable, low-contamination SML sampling, emphasizing their suitability for broader use in marine biogeochemical research demanding high resolution and minimally disturbed interface measurements. InterSeA is one of the smallest and lightest USVs using rotating glass discs for SML sampling.