Tracing the Trophic Fate of Aquafeed Macronutrients With Carbon Isotope Ratios of Amino Acids

Abstract

To meet future seafood demands, ingredients derived from algae and other novel and sustainable sources are increasingly being tested and used as replacers to traditional aquafeed ingredients. Algal ingredients in particular are being promoted for their sustainability and their additional functional attributes in farmed aquatic animals. Test on algal supplemented aquafeeds typically focus on a suite of immunological and physiological indicators along with fish growth performance or muscle quality. However, to optimize the replacement of fish meal with algal derived ingredients, it is crucial to understand the metabolic fate in the algal macronutrients (carbohydrates, fats, and proteins), and their nutritional interactions with other ingredients after ingestion. Here, we assess the potential of using the emerging technology- stable carbon isotope (δ13C) analysis of single amino acids (AAs) as a nutritional biomarker in aquaculture. Applications of δ13CAA-based approaches in feeding trials show promise in closing the knowledge gap in terms of understanding how fish and other aquaculture taxa assimilate and metabolize algal derived macronutrients. Source diagnostic δ13C fingerprints among the essential AAs can trace the protein origins to broad phylogenetic groups such as red macroalgae, brown macroalgae, bacteria, and terrestrial plants. Among the non-essential AAs, δ13C patterns have the potential to inform about metabolic routing and utilization of dietary lipids and carbohydrates. Despite the potential of δ13CAA as a nutritional biomarker, the few applications to date in fish feeding trials warrant further development and implementation of δ13CAA-based approaches to improve understanding of protein origins and macronutrient metabolic routing.

Variations of microbial communities and substrate regimes in the eastern Fram Strait between summer and fall

“…To assess the protein content of the biopolymer pool, we differentiated DHAA into essential amino acids (EAA) and non‐essential amino acids (NEAA). Phytoplankton can synthesize both EAAs and NEAA depending on their nutrient limitation, while higher trophic levels rely on the acquisition of EAA through their diet and acquisition or de novo synthesis of NEAA (Arts et al ., 2009; Grosse et al ., 2019; Larsen et al ., 2022). Concentrations of EAA and NEAA decreased significantly between summer and fall (Table 2; Wilcoxon Rank Sum Test p < 0.001).…”

Autochthonous production sustains food webs in large perialpine lakes, independent of trophic status: Evidence from amino acid stable isotopes

“…However, Manlick and Newsome (2022) found that the C fingerprinting was largely conserved from diet to consumers despite of C fractionation, supporting its usefulness to discriminate between isotopically distinct organic sources at the base of food webs. More experimental studies are needed to further characterise the transfer of the C fingerprinting up through the food web. While our model assumes a uniform stoichiometry of EAAs, this might not be the case because: different primary producers and diet sources can have different AA stoichiometry (Dwyer et al, 2018), and some AAs might be preferentially assimilated by consumers (Larsen et al, 2022) or degraded by bacteria in lakes (Krempaska et al, 2021). This could be particularly the case for consumers that rely on endosymbionts.…”

“…The stable isotope analysis of specific compounds, such as AAs, also opens new ways to answer some of these questions. For instance, it provides new tools to elucidate the origin of different compounds (Larsen et al, 2022; Pilecky et al, 2021), nutrient limitation in consumers (Wang et al, 2019; Whiteman et al, 2021) or new dimensions of the consumers diet niche (Larsen et al, 2020; Ledesma et al, 2020).…”

“…3. While our model assumes a uniform stoichiometry of EAAs, this might not be the case because: different primary producers and diet sources can have different AA stoichiometry (Dwyer et al, 2018), and some AAs might be preferentially assimilated by consumers (Larsen et al, 2022) or degraded by bacteria in lakes (Krempaska et al, 2021). This could be particularly the case for consumers that rely on endosymbionts.…”

Reconstructing Hominin Diets with Stable Isotope Analysis of Amino Acids: New Perspectives and Future Directions

“…With regards to δ 13 C, the nonessential amino acids are more complex to interpret than the essential amino acids, but they do open the door for the development of a series of additional biomarker approaches to diet reconstruction, such as inferring macromolecular composition (Larsen et al. 2022 ). In the case of δ 15 N, source-trophic pairs, such as proline and lysine, or glutamic acid and lycine, may provide more consistent trophic position estimates for hominins than the commonly used glutamic acid–phenylalanine pair.…”