Methylmercury biomagnification in aquatic food webs of Poyang Lake, China: Insights from amino acid signatures

Trophic Transfer of Halogenated Organic Pollutants in a Wetland Food Web: Insights from Compound-Specific Nitrogen Isotope of Amino Acids and Food Source Analysis

“…These phenomena demonstrate the accuracy of the TP simmr model in quantifying the TP of primary consumers. Furthermore, the significant negative correlation observed between TP AAs and ΔTP (simmr‑AAs) (ΔTP (simmr‑AAs) = TP simmr – TP AAs ) was consistent with past research (Figure S1­(b)), − suggesting that organisms in higher TPs are less affected by β Glu/Phe variation . However, the TP simmr of the top predators (kingfishers, 2.80; amphibians (frogs), 2.06) was not significantly higher than that of their diet (paradisefish, 2.71; insects, 1.81) (Figure (a)).…”

“…The TP AAs (1.04) of the emerged plants, which were also vascular plants, were similar to those of the emerged plants (TP AAs = 0.94) reported by Yan et al These phenomena demonstrate the accuracy of the TP AAs model for quantifying the TP of primary producers. Furthermore, a significant positive correlation between TP bulk and ΔTP (bulk‑AAs) (ΔTP (bulk‑AAs) = TP bulk – TP AAs ) was observed, which has been reported in past studies, − , supporting that δ 15 N baseline variation may have a greater impact on TP bulk quantification of organisms at higher TPs (Figure S1­(a)). The TP AAs of kingfishers (2.11) were significantly lower than those of their prey (paradisefishes, 3.50) (Tables S2 and S4), which may be related to the fact that kingfishers take in some terrestrial food sources (moths) indirectly through the process of food web delivery, making it inappropriate to use β Glu/Phe (3.4‰) to estimate the TP AAs of kingfishers.…”

“…The similarity of δ 13 C bulk between grasshoppers and terrestrial C4 plants may be coincidental, resulting from the contribution of multiple food sources, rather than indicating the real feeding relationship. , Inaccurate δ 15 N baseline leading to misestimation of TP bulk or even prey TP bulk being greater than predator TP bulk has been found in past studies. − In general, the span of TP bulk in food chains ranges from 1 to 5.5, while δ 15 N baseline variation may lead to a bias of TP bulk > 3, suggesting that the TP bulk model could cause significant misestimation of TP bulk of organisms in complex food webs and food chain inversions. Furthermore, the TP bulk model, used to study contaminant biomagnification, assumes that all organisms are in a single food chain. , However, natural food webs consist of multiple primary producers with distinct stable carbon isotope signatures (e.g., C3 and C4 plants). − For example, the organisms in this study can be divided into four food chains represented by primary producers according to the Δδ 13 C bulk ≤ ±1‰ (Tables S2 and S3). The results showed that the TP bulk model struggled to represent the true structure of the food web.…”

Meta‐analysis of primary producer amino acid δ15N values and their influence on trophic position estimation

“…Freshwater non‐vascular primary producers are woefully understudied within the CSIA‐AA literature (3.8% of analysed taxa; Table 1), with only four studies reporting AA δ 15 N data (Fogel & Tuross, 1999; Ishikawa et al., 2014; Ohkouchi et al, 2015; Zhang et al, 2019, 2021). Freshwater eukaryotic microalgae β Glx‐Phe values (+4.2 ± 0.7‰, n = 5) were similar to those of their marine counterparts (+3.9 ± 1.6‰, n = 22, p > 0.05; Figure 3).…”

“…Multiple molecular tools are available for use in tandem with mixing models to estimate the relative contribution of vascular and non‐vascular primary producers to consumer food webs, such as bulk tissue δ 13 C and δ 15 N values (e.g. Choi et al., 2017; Zhang et al., 2019, 2021), AA δ 13 C ‘fingerprinting’ (e.g. Bowes et al., 2020; Chua et al., 2020), fatty acid analysis (Hebert et al., 2016) and Δ Met‐Phe (δ 15 N Met – δ 15 N Phe ; Ishikawa et al, 2018).…”