Spatiotemporal distribution of long-chain polyunsaturated fatty acids (LC-PUFA) in gill filterable fish food webs of European freshwater lakes and ponds: a systematic review

Abstract

Temperate European lakes and fishponds offer an untapped source of land-locked long-chain polyunsaturated fatty acids (LC-PUFAs), including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA). This article systematically compiles data from 48 peer-reviewed studies (2000–2024) to assess their spatiotemporal availability in gill-filterable (> 100 µm) planktonic and benthic fish food webs. Spatial analysis reveals that zooplankton DHA content increases with latitude, while EPA and ARA levels peak in lowland waterbodies. Zoobenthos exhibit stable ARA and EPA concentrations across latitudes but lower DHA levels than zooplankton. Temporal trends indicate a decline in DHA and EPA in highland zooplankton over recent decades, likely influenced by climate change, while eutrophication-driven shifts contribute to seasonal DHA reductions in lowland lakes. Fatty acid stoichiometries (SFA: PUFA, n-6: n-3 PUFA) suggest metabolic adaptations to climate, with PUFA sparing effects increasing with latitude. Ecological correlations indicate dissolved organic carbon (DOC) positively influences EPA and DHA in zooplankton, whereas total phosphorus shows negative correlations, suggesting eutrophication could reduce n-3 LC-PUFA availability. Generalized additive modeling highlights an optimum organic carbon load (8–10 mg DOC L⁻¹) and reduced phosphorus–driven eutrophication (< 20 µg TP L⁻¹) for maximized EPA (> 20 µg g⁻¹ dry matter, DM) and DHA (> 10 µg g⁻¹ DM) concentrations. Zooplankton-benthos provide 600–1050 mg EPA + DHA 100 g⁻¹ DM (zooplankton > zoobenthos), and out of it, freshwater fish likely accumulate 150–525 mg EPA + DHA 100 g⁻¹ biomass. High-latitude, pelagic niche, lowland waterbodies during spring are identified as omega-3 LC-PUFA “hotspots” but progressively deteriorating over the last decades due to global change.