“…However, FA trophic markers are not taxonomic indicators at the phytoplankton species level because some FAs indicate multiple algae classes (e.g., EPA in diatoms and (dino-) flagellates, Dalsgaard et al., 2003). Lately, stable carbon isotope analysis (δ 13 C) of individual essential compounds has been used as an accurate tool to reconstruct phototrophic sources of FAs and AAs in food webs (Kohlbach et al, 2016;Larsen et al, 2013;McMahon, Fogel, Elsdon, & Thorrold, 2010;Nielsen, Clare, Hayden, Brett, & Kratina, 2018) and thus can complement studies on FA trophic markers. in the Baltic Sea, can still be synthesized de novo by zooplankton (Kattner & Hagen, 1998;Peters et al, 2006).…”