Bio-optical Collections in Freshwater Submerged Aquatic Vegetation in a Riverine–Deltaic Ecosystem

This study presents the first application of NASA’s EMIT hyperspectral observations for investigating submerged and emergent habitats within the rapidly evolving Atchafalaya River Delta and Estuary. Results showed that submerged aquatic vegetation (SAV) detectability was controlled primarily by vegetation canopy depth and water-column optical attenuation rather than vegetation density and species alone. Strong negative relationships were observed between canopy depth and spectral indices, including Normalized Difference Red Edge (NDRE) (=0.968) and the NIR/Green ratio (=0.954). Principal component analysis further demonstrated that dissolved organic carbon and colored dissolved organic matter substantially influenced SAV spectral attenuation and underwater light limitation, with PC2 strongly correlated with DOC (=0.968, 0.0015). Further, linear spectral unmixing resolved ecologically meaningful gradients among SAV, freshwater marsh, brackish marsh, saline marsh, and water optical classes throughout the delta system. The derived hyperspectral endmembers successfully reconstructed mixed EMIT spectra (; =0.819–0.999; RMSE = 0.008–0.115; SAM = 1.19–15.18) and distinguished dense and sparse SAV across a range of water depths, floating aquatic vegetation, wetland vegetation, and turbid-water classes in optically complex estuarine environments. SAV occupied approximately 26.6% (117.49 km2) of the 441.77 km2 study area, while high-density SAV (50% fractional abundance) represented 6.0% (26.63 km2). Beyond habitat mapping, EMIT-derived SAV fractional abundance demonstrated broader ecological and biogeochemical applications through spatially explicit methane flux scaling. Overall, this study demonstrates that spaceborne hyperspectral imaging spectroscopy provides a more detailed view of habitat-rich deltaic systems and establishes a practical framework for monitoring submerged and emergent vegetation within optically complex and rapidly evolving deltaic environments. All data, code, and scripts used for the analyses and figures are provided here.