Trophic transfer of polyunsaturated fatty acids across the aquatic–terrestrial interface: An experimental tritrophic food chain approach

Abstract

Aquatic and their adjacent terrestrial ecosystems are linked via the flux of organic and inorganic matter. Emergent aquatic insects are recognized as high-quality food for terrestrial predators, because they provide more physiologically relevant long-chain polyunsaturated fatty acids (PUFA) than terrestrial insects. The effects of dietary PUFA on terrestrial predators have been explored mainly in feeding trials conducted under controlled laboratory conditions, hampering the assessment of the ecological relevance of dietary PUFA deficiencies under field conditions. We assessed the PUFA transfer across the aquatic-terrestrial interface and the consequences for terrestrial riparian predators in two outdoor microcosm experiments. We established simplified tritrophic food chains, consisting of one of four basic food sources, an intermediary collector gatherer (Chironomus riparius, Chironomidae), and a riparian web-building spider (Tetragnatha sp.). The four basic food sources (algae, conditioned leaves, oatmeal, and fish food) differed in PUFA profiles and were used to track the trophic transfer of single PUFA along the food chain and to assess their potential effects on spiders, that is, on fresh weight, body condition (size-controlled measurement of nutritional status), and immune response. The PUFA profiles of the basic food sources, C. riparius and spiders differed between treatments, except for spiders in the second experiment. The PUFA α-linolenic acid (ALA, 18:3n-3) and ɣ-linolenic acid (GLA, 18:3n-6) were major contributors to the differences between treatments. PUFA profiles of the basic food sources influenced the fresh weight and body condition of spiders in the first experiment, but not in the second experiment, and did not affect the immune response, growth rate, and dry weight in both experiments. Furthermore, our results indicate that the examined responses are dependent on temperature. Future studies including anthropogenic stressors would deepen our understanding of the transfer and role of PUFA in ecosystems.

Subsidy Quality Affects Common Riparian Web‐Building Spiders: Consequences of Aquatic Contamination and Food Resource

“…In line with our hypothesis, food quality explained most of the variation in the FA profile of chironomids. In fact, the differences between Spirulina and TetraMin, which served as food, were partially reflected in the FA profile of adult chironomids, while also suggesting that chironomids have the capacity to modify dietary FA (Goedkoop et al, 2007; Ohler, Schreiner, Martin‐Creuzburg, & Schäfer, et al, 2023; Strandberg et al, 2020). The capability to modify or preferentially retain certain dietary FAs was stronger when chironomids were fed with Spirulina, which could be explained by a greater discrepancy between chironomids' physiological demands and supply of this basal resource (Goedkoop et al, 2007).…”

“…Changes in the energy transfer can be further amplified by the nutritional quality of (basal) resources. Similar to chironomids, spiders of the genus Tetragnatha have the capacity to modify dietary FAs (Mathieu‐Resuge et al, 2021; Ohler, Schreiner, Martin‐Creuzburg, & Schäfer, 2023), as indicated by the lower relative importance of the FA profile of the basal resource for the FA profile of spiders (Figure 4). However, the extent to which spiders use this ability depends largely on the dietary availability of certain physiologically important FAs because the modification of FAs is considered more energetically costly relative to their dietary uptake (Parrish, 2009).…”

Interactive effects of bismuth exposure (water and diet) and temperature on snail fatty acid composition, antioxidant enzymes and lipid peroxidation

“…Fatty acids are important biomolecules transferred through aquatic and terrestrial food webs (Torres-Ruiz et al, 2007;Guo et al, 2017;Ohler et al, 2023). Consequently, the FA compositions of living organisms are inherently connected (Guo et al, 2016).…”