Work

Differentiating phytoplankton taxa in lakes using hyperspectral in situ reflectance and imaging microscopy

Year: 2025

Type: article

Abstract: Phytoplankton play a central role in aquatic ecosystems, influencing biogeochemical cycles, food web dynamics, and overall water quality. Monitoring their composition is essential for assessing water ecosystem health and detecting environmental changes. Chlorophyll- a concentration is widely used as a proxy for phytoplankton abundance in inland waters. Together with colored dissolved organic matter and total suspended matter, these parameters can be retrieved from remote sensing reflectance data. However, identifying the detailed taxonomic composition of phytoplankton in lakes remains a major challenge. Spectral matching algorithms offer promising solutions to overcome this limitation. In this study, we investigated the potential of retrieving phytoplankton taxa composition from high-resolution in situ spectroscopy measurements by applying radiative transfer inversion and validating the results against phytoplankton abundance data obtained from an imaging microscope. First, we assessed the performance of our approach in retrieving four phytoplankton taxa under cloud-free conditions. Then, we extended the analysis to two seasons, covering multiple consecutive blooms using data acquired independently of cloudiness. The high agreement between the imaging microscopy results and those obtained from in situ spectroscopy indicates that remote sensing with radiative transfer inversions can track the evolution of phytoplankton blooms. The results suggest that low phytoplankton concentrations and the lack of unique spectral features for some taxa may prevent the accurate identification of phytoplankton composition through spectroscopy. In addition, the natural variability in cell size, along with physiological changes such as fluctuations in intracellular chlorophyll- a content, impacts the empirical conversion from cell cross section to intracellular chlorophyll- a content. • Radiative transfer model inversion to retrieve phytoplankton taxonomic composition. • Phytoplankton blooms in inland waters could be reliably tracked. • Underwater imaging microscopy shows potential to validate remote sensing data. • Our approach allows validating products from upcoming imaging spectroscopy missions. • Conversion from cell cross section to intracellular chlorophyll- a content.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2025.180718

Authors: Loé Maire, Peter Gege, Alexander Damm, Daniel Odermatt

Institutions: University of Zurich, Swiss Federal Institute of Aquatic Science and Technology, Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Language: English

Topic: Aquatic Ecosystems and Phytoplankton Dynamics

Subfield: Environmental Chemistry

Field: Environmental Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,250

Funder: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung