Diet predicts fatty acids of zooplankton more than environmental or geographical variables: evidence from subarctic to subtropical aquatic ecosystems

Dietary transfer of fatty acids (FA) across the plant–animal interface of aquatic ecosystems is important for zooplankton fitness and, subsequently, consumers at higher trophic levels. To date, our knowledge of trophic FA transfer is limited to aquatic ecosystems of similar climatic areas. In this field study, aquatic ecosystems ranging from subarctic to temperate and subtropical climates were selected to examine FA of seston and zooplankton. Results show that physicochemical and geographic/morphometric factors predicted only 35% of the FA variation in seston. While the overall FA composition among each zooplankton taxon differed significantly across habitats, taxon-specific FA patterns grouped cladocerans (via eicosapentaenoic acid) and pooled zooplankton (mostly copepods; via docosahexaenoic acid). Seston FA predicted up to 3 times more of the FA variation in zooplankton than physicochemical and geographic/morphometric variables, and the sum of all predictors explained up to 75% of the FA variation in cladocerans and 55% in pooled zooplankton. The FA dispersion patterns between consumers and seston indicated a strong reorganization/ bioconversion of polyunsaturated FA in zooplankton, suggesting zooplankton resilience to environmental change. Therefore, this study provides field evidence that dietary FA transfer and the concurrent ability of zooplankton to organize their FA seem to be key for their adaptation.