Spectral radiance measurements during a Nodularia spumigena bloom event on Lake Bante in Wilhelmshaven, Germany

Hyperspectral radiance observations were made from a small electric motor powered boat on Lake Bante in Wilhelmshaven, Germany during a Nodularia spumigena bloom event. The observations were completed on 25 August 2022 using a Spectral Evolution (SEV) SR-3501 spectroradiometer covering the wavelength range 280 nm to 2500 nm. SEV was operated in calibrated radiance mode with an 8° field-of-view lens fitted. Each measurement was generated as the mean of 20 scans. At each station, a series of 3 calibrated radiance measurements were done over the unique optical active targets (i) a 20 × 20 cm SphereOptics Zenith Polymer® SG3120 ≈ 99 % full material PTFE diffuse standard panel = Ed, (ii) lake water surface = Lsfc and then (iii) sky = Lsky at a ~45° viewing angle from nadir. The series of observations at each station was repeated at most 6 times. The measurements were completed at an azimuthal angle from sensor heading to the sun within the range 90 - 135° to avoid surface reflectanced (Garaba and Zielinski, 2013). Quality control step managed to obtain a set of at least 3-6 pseudo replicate measurements for the sampled stations as some measurements were affected by drift and rotation of the boat that resulted in non-optimal viewing geometry or presence of surface reflected glint.