Fatty acid composition of consumers in boreal lakes – variation across species, space and time

Abstract

Summary 1. Fatty acids (FAs) have been widely applied as trophic biomarkers in aquatic food web studies. However, current knowledge of inter‐ and intraspecific variation in consumer FA compositions across spatial and temporal scales is constrained to a few pelagic taxa. 2. We analysed the FAs of 22 taxa of benthic macroinvertebrates, zooplankton and fish collected from the littoral, pelagic and profundal habitats of nine boreal oligotrophic lakes over spring, summer and autumn. We quantified and compared the FA variance partitions contributed by species identity (i.e. an integrative effect of phylogenetic origin, life history and functional feeding guild of individual taxa), site and season using partial redundancy analysis both on all consumers and on benthic arthropods alone. 3. Species identity alone contributed 84.4 and 72.8% of explained FA variation of all consumers and benthic arthropods, respectively. Influences of site, season and all joint effects accounted for 0–11.3% only. Fatty acid profiles of primary consumers differentiated below class level, but those of predators were distinguishable only when they became more taxonomically distinct (i.e. among classes or higher). 4. Pelagic and profundal consumers showed stronger reliance on autochthonous resources than did their littoral counterparts as reflected by their higher ω3 to ω6 FA ratios. Polyunsaturated FAs (PUFAs) were increasingly retained with trophic levels, and saturated FAs (e.g. FA 16 : 0) gradually reduced. Ecologically, this trade‐off enhances the trophic transfer efficiency and confirms the importance of PUFA‐rich autotrophs in aquatic food webs. 5. Our findings indicate strong interspecific differences in FA requirements and assimilation among aquatic consumers from a wide range of taxonomic levels, habitats and lakes. Consumers were able to maintain homoeostasis in FA compositions across spatial and temporal changes in resource FAs, but consumer homoeostasis did not limit the effectiveness of FAs as trophic biomarkers.

Comparison of fatty acids profile and antioxidant enzyme level of cladoceran Moina brachiata (jurine, 1820) from freshwater bodies of Chennai

“…The earlier results are in concord with results found by [25]. Lau et al [6] also described the Adult Daphnia magna showed the lower level of MUFA, but rather high level of PUFA. Although, the Cladoceran M. brachiata diet with Scenedesmus sp., showed increasing amount of EPA and decreasing amount of AlA and LIN at Kolavoi Lake.…”

“…The accumulation of PUFA in aquatic invertebrates depends on an ordinal of environmental factors, such as water temperature [2] food type [4] and pollution [5]. In addition to such factors, phylogeny is a key determinant of the FA composition of animals [6]. For instance, two of the most significant large taxa of planktonic freshwater invertebrates, Cladocera and Copepoda, vary significantly in EPA and DHA percentages [7].…”

Selective transfer of polyunsaturated fatty acids from phytoplankton to planktivorous fish in large boreal lakes

“…Taxon-specific differences in fatty acid (FA) composition are much larger than intraspecific variation due to differences in the diet composition and/or environmental conditions . Variation in phytoplankton and zooplankton community composition according to physical characteristics of lakes, allochthonous organic matter content and trophic state (Kortelainen, 1993;Lepistö and Rosenström, 1998) suggest that the FA in the pelagic food web of large lakes may differ from the more intensively studied smaller and shallower lakes (Müller-Navarra et al, 2004;Lau et al, 2012).…”

“…Although the ecological and hydrological processes of large lakes have been extensively studied (Nõges, 2008), research on the trophic transfer of polyunsaturated fatty acids (PUFA) through food webs of large lakes (surface area N 100 km 2 ) is very limited (Smyntek et al, 2008). Current knowledge on the composition and trophic dynamics of PUFA in freshwater lakes is almost entirely based on small or moderately sized lakes (Ahlgren et al, 1996;Kainz et al, 2004;Müller-Navarra et al, 2004;Ravet et al, 2010;Lau et al, 2012). In aquatic ecology, PUFA are attracting increasing attention because studies indicate that PUFA from the n-3 family (PUFAn-3) may limit consumer production (Müller-Navarra et al, 2004).…”

Photocatalytic properties of titanium dioxide nanoparticles affect habitat selection of and food quality for a key species in the leaf litter decomposition process

“…Furthermore, decreased contents of essential factors in the nutrition of benthic macroinvertebrates (microbial decomposers and lipids; cf. B€ arlocher, 1985;Lau et al, 2012) have been reported for leaf-litter exposed to solar UV-B irradiation (Day et al, 2007), indicating a lowered quality of the offered food. Gammarids as highly selective consumers (cf.…”