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Evaluating a multispectral miniaturised fluorometer with three excitation channels for predicting phytoplankton community structure indices from BGC-Argo float observations
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DOI:10.5194/bg-23-4561-2026.png)
Abstract
En 中文
Abstract. Phytoplankton community composition is a key determinant of ocean biogeochemical cycles; yet its observation from autonomous platforms remains challenging. In this study; we assessed the potential of in situ multispectral excitation fluorescence (MXF) to predict phytoplankton community structure indices in the Northwestern Mediterranean Sea. With a view toward applications on Biogeochemical-Argo (BGC-Argo) profiling floats; we evaluated a miniaturised; three-excitation-channel fluorometer. Laboratory measurements on ten phytoplankton strains confirmed that MXF ratios at 440; 470; and 532 nm provide taxon-specific signatures; especially for picocyanobacteria and green algae. Field observations of phytoplankton pigments were clustered into four ecologically distinct phytoplankton communities across the seasonal cycle; which defined the targeted phytoplankton community structure indices. A machine learning model was then trained to classify these clusters using MXF and additional bio-optical indices. Results show that existing BGC-Argo configurations (single-wavelength fluorescence; particulate backscattering; and beam attenuation coefficients) reliably distinguish broad community structures; such as pico- versus microphytoplankton dominance; but resolving finer pigment-based differences requires the additional spectral information provided by MXF. The different excitation channels contributed unequally: 440 and 470 nm provided robust pigment sensitivity across communities; while 532 nm was particularly informative for detecting phycoerythrin-rich taxa. Overall; combining MXF with bio-optical proxies improved classification performance by integrating pigment-specific and size-structure information; demonstrating the potential of MXF to enhance autonomous monitoring of phytoplankton community dynamics and their role in ocean biogeochemical cycles.
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