The rosette‐based glass plate sampler: A cost‐effective technique for high‐volume, low‐thickness sea surface microlayer collection

The sea surface microlayer (SML) is the interface at the ocean surface that can modulate air–sea gas and particle exchange. Its unique position at the interface presents distinct challenges for sampling and study. Here, we introduce a new SML sampler, the rosette‐based glass plate (RGP) sampler, designed to collect large volumes of SML while maintaining thin SML samples throughout the collection. The RGP sampler consists of three borosilicate glass plates mounted on a CTD rosette frame deployable from the A‐frame of a research vessel. We deployed the RGP sampler during three intensive campaigns across four hydrographic regions in the North Atlantic Ocean. The sampler consistently collected SML samples with an average thickness of 13.8 ± 3.23 μ m and total volumes > 1.5 L in less than 2 h, enabling multiparametric analyses from a single deployment. Here, we show that while dissolved organic carbon (DOC) concentrations in both the SML and subsurface water decrease with distance from the coast, enrichment of DOC, chromophoric dissolved organic matter (CDOM), and fluorescent DOM (FDOM) is dependent on the sampling location. These results support the need for further characterization of DOM and surfactants in diverse hydrographic settings. Notably, we demonstrate that the high volume samples collected using the RGP sampler enable in‐depth physico‐ and biogeochemical analyses (CDOM, FDOM, high resolution mass spectrometry [MS], liquid chromatography‐MS lipidomics, microbial 16S and 18S DNA sequencing, tensiometry, and DOC and surfactant quantification) that can link surfactant properties to oceanographic conditions that will facilitate a greater understanding of processes at the air–sea interface.