24 Cruise Report, RV ATAIR, Cruise 067I033-1, Bremerhaven – Thybor?n – Aberdeen, 23 Jul – 15 Aug 2024 During cruise 067I033-1, water samples were taken at daylight stations with the purpose to determine the phytoplankton content in the surface layer of the North Sea, see Figure 5.9. The stations selected were consistent with those for Secchi depth observations and water sampling for chlorophyll-a analysis. For phytoplankton, 1 L of seawater was taken from the Niskin bottles closed at 5 m and placed in a glass bottle after rinsing the bottle three times with seawater. 200 mL of this sample was transferred to a smaller glass bottle using a graduated cylinder. Using a pipette, 2 mL of acidic Lugol’s solution was added to the water sample in order to fix and preserve the phytoplankton samples during the field work. The glass jar was then sealed using a flexible parafilm and stored in the dark In total, phytoplankton samples from 14 stations (GN007A, GN008S, GN018A, GN019S, GN021, GN022A, GN023, GN024, GN025, GN027, GN037, GN043, GN044, GN045) were evaluated as part of the EnsAD project to validate satellite data from hyperspectral sensors. Samples were selected based on the availability of useful remote sensing information at the time of the sampling. Figure 5.9. Distribution of stations carried out during cruise 067I033-1 with phytoplankton sampling (red dots).