Fatty acid composition of zooplankton species from Fram Strait during POLARSTERN cruise PS100, PS107, and PS121

A combination of fatty acid and stable isotope biomarker analyses was utilized to investigate the dietary composition and trophic levels of key zooplankton species across Fram Strait, including Arctic and boreal-Atlantic sister species of Calanus, Paraeuchaeta, and Themisto. Samples were collected during three RV Polarstern expeditions (PS100, PS107, and PS121) using either a multiple opening and closing net equipped with five nets for stratified vertical hauls (Hydrobios Multinet Midi, mouth opening 0.25 m², mesh size 150 µm, hauling speed 0.5 m s⁻¹) or a bongo net (mesh size 200–500 µm, towing speed 1–2 knots). Vertical hauls with the Multinet typically sampled the entire water column, from above the seafloor or a maximum depth of 1,500 m to the surface. Immediately after the haul, individuals were sorted by species and developmental stage in a temperature-controlled lab and stored in Eppendorf tubes at -80°C for subsequent fatty acid and stable isotope analyses.