Beaked whales, including northern bottlenose whales (Hyperoodon ampullatus), are widely considered deep-diving squid specialists. In Canada, where northern bottlenose whales are of conservation concern following historical depletion, resolving diet composition is critical for understanding differences in population recovery and evaluating risks from overlap with regional fisheries. Here, we analyse stable isotopes (delta 13C, delta 15N; Bayesian mixing models) from skin (n = 141 samples) and fatty acids from blubber (quantitative fatty acid signature analysis, QFASA; n = 96 samples) from northern bottlenose whales, alongside a large library of potential prey (19 species) collected across the western North Atlantic (42-74 degrees N). Stable isotope data suggested that females in both Arctic and Scotian Shelf populations exhibited broader ecological niches than males. However, diet composition differed between regions, mirroring known genetic structure. In Arctic whales, squids' contribution was low, while diets were predominantly fish-based, with contributions from grenadiers (family Macrouridae), redfish (Sebastes spp.), and Greenland halibut (Reinhardtius hippoglossoides). Scotian Shelf whales consumed both demersal fish (redfish) and squid (Gonatus fabricii). Both biomarkers indicate substantial reliance on demersal fish, consistent with flexible foraging strategies and suggesting a broader diet than the obligate squid specialist view. These findings underscore the need to consider diverse prey fields and potential fisheries interactions in conservation and recovery efforts.

With the increasing interest in the commercialization of microalgal fermentation-based products, sustainable and efficient oil extraction methods have been developed for manufacturing and analytical testing. Due to the variability and resilience of micro-algae cell walls, traditional lipid extraction methods such as Folch and Bligh and Dyer are not always efficient, leading to the development of enzymatic treatments to assist in lipid recovery. In this study, we used enzymatic treatment prior to a modified Folch extraction to maximize the extraction efficiency for the purpose of lipid profile analysis. The literature provides little evidence on whether nonspecific proteases degrade amide linkages in lipid structures like sphingolipids; therefore a normal phase HPLC method coupled with an Evaporative Light Scattering Detector (ELSD) was developed to determine changes in lipid class concentrations due to enzymatic treatment. We used lipid standards to compare the effects of enzymatic treatment and to determine the recoveries of each lipid class. Our lipid extraction model suggested that tridocosahexaenoylglycerol (TG-DHA) undergoes significant oxidation induced by heat treatment during the extraction process, rather than by enzymatic activity.

The essential fatty acids (EFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are required for the maintenance of good health in humans. In the marine environment, they are primarily synthesized by phytoplankton and their production is predicted to decrease with warming seawater temperatures. With reduced production, it becomes critical to understand the efficiency with which these EFA are transferred through trophic systems. To do this, captive Atlantic pollock (Pollachius virens) were fed one of two test diets for 83 days; both contained 11% total lipids, with one having half the absolute concentration of both EPA and DHA. Fish were hand-fed to satiation so a mass balance approach, monitoring intake and accumulation of EFA and energy, could be used to determine the FA-specific net growth efficiency (NGE). At the conclusion of the feeding study, NGE for EPA and DHA were determined at 56 and 52%, respectively, in fish fed diets that were rich in these EFA. However, in fish that received reduced dietary proportions of EPA and DHA, lower NGE, at 36 and 25%, respectively, were found, indicating that a limited ability to retain essential nutrients may exist when dietary supply is reduced. NGE for EFA in both diets, relative to energy, were 1.4–2 fold higher, offering a starting point for the development of trophic models evaluating transfer of these essential nutrients, rather than energy.

IntroductionQuantitative fatty acid signature analysis (QFASA) can provide species level diet estimates integrated over weeks to months, which are valuable for assessing health, ecological roles, and disturbance vulnerability. However, the approach has seen limited use in cetaceans. Calibration coefficients (CCs) have mainly been derived from non-cetacean mammals, best-fit QFASA model parameters are undefined, and the temporal integration of blubber fatty acids (FAs) remains poorly resolved.MethodWe used bottlenose dolphins (Tursiops truncatus, n = 3, hereafter "dolphin") under professional care with known, varied diets to develop and evaluate species- and blubber layer-specific CCs and explore model performance under different parameter combinations. For each dolphin, we calculated CCs for the inner and outer blubber, compared these to published non-dolphin CCs, and evaluated QFASA-estimated diets across different FA sets, distance measures, CC sources (dolphin and non-dolphin), and FA integration periods. Model performance was assessed using prey distinctiveness, the percentage of predator FAs that fell outside prey ranges [predator-beyond-prey (PBP) values], and weighted error between estimates and the dolphins’ known diets.ResultsDolphin CCs differed between the inner and outer blubber and from non-dolphin CCs for many FAs. Dolphin-specific, layer-matched CCs produced lower-error estimates and identified key prey species more accurately than non-dolphin CCs. Inner and outer blubber estimates were consistent with prey consumption integrated over weeks to months, supporting QFASA’s long-term nature. However, model performance was sensitive to FA set, distance measure, CC source, and dolphin diet complexity. In some parameter combinations, the augmented FA contributed a large portion of the model signal, reducing interpretability. This highlights the need for cautious parameter selection.DiscussionThese results provide the first layer-specific CCs for bottlenose dolphins and illustrate the utility and limitations of QFASA for cetacean diet estimation. We recommend that investigators use species- and layer-specific CCs where possible and consider prey distinctiveness, PBP values, and the augmented FA’s contribution when selecting model parameters. We also caution against over-interpreting best-fit parameter sets and diet estimates derived from small calibration datasets. To yield the most complete understanding of free-ranging cetacean diet, QFASA is best applied as one of several complementary methods rather than as a standalone approach.

This study explores the potential of Cucumaria frondosa (C. frondosa) viscera as a natural source of omega-3 FAs using supercritical carbon dioxide (scCO2) extraction. The extraction conditions were optimized using a response surface design, and the optimal parameters were identified as 75 °C and 45 MPa, with a 20 min static and a 30 min dynamic extraction, and a 2:1 ethanol to feedstock mass ratio. Under these conditions, the scCO2 extraction yielded higher FAs than the solvent-based Bligh and Dyer method. The comparative analysis demonstrated that scCO2 extraction (16.30 g of FAs/100 g of dried samples) yielded more fatty acids than the conventional Bligh and Dyer method (9.02 g, or 13.59 g of FAs/100 g of dried samples with ultrasonic assistance), indicating that scCO2 extraction is a viable, green alternative to traditional solvent-based techniques for recovering fatty acids. The pre-treatment effects, including drying methods and ethanol-soaking, were investigated. Freeze-drying significantly enhanced FA yields to almost 100% recovery, while ethanol-soaked viscera tripled the FA yields compared to fresh samples, achieving similar EPA and DHA levels to hot-air-dried samples. These findings highlight the potential of sea cucumber viscera as an efficient source of omega-3 FA extraction and offer an alternative to traditional extraction procedures.

The application of fatty acid (FA) isotopic analysis has great potential in elucidating food web structure, but it has not experienced the same wide-spread use as amino acid isotopic analyses. The failure to adopt FA isotopic methods is almost certainly linked to a lack of reliable information on trophic fractionation of FA, particularly in higher predators. In this work, we attempt to address this shortfall, through comparison of FA δ 13 C values in captive Atlantic pollock ( Pollachius virens ) liver and their known diets. Since catabolism is likely the main cause of fractionation and it may vary with dietary fat content, we investigated the impact of dietary fat concentration on isotopic discrimination in FA. We fed Atlantic pollock three formulated diets with similar FA isotopic compositions but different fat concentrations (5–9% of diet), representative of the range found in natural prey, for 20 weeks. At the conclusion of the study, δ 13 C values of liver FA were very similar to the FA within the corresponding diets, with most discrimination factors < 1. For all FA except 22:6n-3, dietary fat had no effect on discrimination factors. Only for 22:6n-3 did fish fed the highest fat diet have lower δ 13 C values than the diet consumed. Thus, these FA-specific discrimination factors can be applied to evaluate diets in marine fish consuming natural diets and will serve as additional and valuable biomarkers in fish feeding ecology.

The potential of a native digestate microbial community for 1,4-dioxane (DX) biodegradation was evaluated under low dissolved oxygen (DO) concentrations (1–3 mg/L) under different conditions in terms of electron acceptors, co-substrates, co-contaminants and temperature. Complete DX biodegradation (detection limit of 0.01 mg/L) of initial 25 mg/L was achieved in 119 days under low DO concentrations, while complete biodegradation happened faster at 91 and 77 days, respectively in nitrate-amended and aerated conditions. In addition, conducting biodegradation at 30 ˚C showed that the time required for complete DX biodegradation in unamended flasks reduced from 119 days in ambient condition (20–25 °C) to 84 days. Oxalic acid, which is a common metabolite of DX biodegradation was identified in the flasks under different treatments including unamended, nitrate-amended and aerated conditions. Furthermore, transition of the microbial community was monitored during the DX biodegradation period. While the overall richness and diversity of the microbial community decreased, several families of known DX-degrading bacteria such as Pseudonocardiaceae, Xanthobacteraceae and Chitinophagaceae were able to maintain and grow in different electron-accepting conditions. The results suggested that DX biodegradation under low DO concentrations, where no external aeration was provided, is possible by the digestate microbial community, which can be helpful to the ongoing research for DX bioremediation and natural attenuation.

The survival of juvenile marine fishes, which support commercial fisheries and provide a prey resource, is often dependent on conditions in protective and nearshore habitats. We examined the trophic interactions of several juvenile fishes in the nearshore Gulf of Alaska (GOA) including Pacific cod (Gadus microcephalus), saffron cod (Eleginus gracillis), walleye pollock (Gadus chalcogrammus), Pacific sand lance (Ammodytes hexapterus), Pacific herring (Clupea pallasii), rockfish (Sebastes spp.) and greenlings (Hexagrammos spp.). We used fatty acid (FA) and stable isotope (SI) markers to evaluate foraging ecology and the potential for competition among age-0 fish species in broad east (134°W – 136°W) and west (149°W – 153°W) regions of the GOA. Sampling efforts were greater in the west GOA, so many of our findings were focused in that region. In the west GOA, FA and SI markers indicated that Pacific cod and saffron cod usually shared similar diets, potentially leading to competition for resources. Also in the west GOA, we found evidence that Pacific cod and walleye pollock both relied to similar extents on calanoid copepods during summer. Juvenile sand lance and herring were much smaller than the other species and had diets that contrasted with all other species. In both the east and west GOA, rockfish were present in two distinct size classes with the smaller size feeding at a lower trophic level than all other fish species in the study. The smaller rockfish likely consumed mainly calanoid copepods. Throughout the east and west GOA, greenling and rockfish typically consumed prey with a very different lipid source than the other juvenile fish. In addition, we noted few consistencies in FA and SI markers between the east and west, except in rockfish diets. Overall, we found a complex relationship within the nearshore fish communities in the east and west GOA that showed substantial variation across bays, seasons and subareas.

Odontocetes possess specialized fat bodies in and around the mandibles for sound reception which have complex topographical distributions of unique endogenous lipids (triacylglycerols and wax esters [WE]). Although there is diversity across species in the fatty acid (FA) and fatty alcohol (FAlc) components of WE, little is understood about the composition and placement of the intact molecules, which will likely impact acoustic function. We aimed to determine the composition and distribution of intact waxes in the jaw fats from five species representative of three odontocete families: delphinids, kogiids, and ziphiids. Total lipid content was similar in all groups, but the WE content of that lipid (21.3%-53.3% of total lipid) and the identity of intact WE molecules showed a high degree of variation, especially in the short-chain fatty acid components. In contrast, the FAlc elements were surprisingly well conserved. There were 26 intact WE that were common to all species but the delphinids had 12 additional WE with short-chain fatty acids (i-5:0 specifically) not found in the other animals examined here. Our study suggests that this highly specialized tissue has evolved several different biochemical pathways, and that there may be multiple strategies for building acoustic fat bodies.

The presence of unintended chemicals in food products and supplements may impact consumers’ health negatively. Mineral oil hydrocarbons (MOHs) in particular are gaining research attention and have been detected and quantified in food products and supplements in the past. The aim of this study was to analyze encapsulated, and bulk minimally processed marine oils for MOHs and to evaluate the probable sources of these compounds. Hydrocarbons in supplement oils were extracted via saponification and analyzed by gas chromatography with both flame ionization and mass spectral detection. While no mineral oil aromatic hydrocarbons (MOAH) were detected in any sample, the analysis revealed the presence of mineral oil saturated hydrocarbons (MOSH) in 9 out of 10 minimally processed encapsulated oils. The MOSH appeared on the chromatograms as an unresolved complex mixture (UCM) with concentrations ranging from 376 ± 49 to 3831 ± 414 mg kg-1. These values are well below the maximum allowable limits for MOH in encapsulated products set by the United States Food and Drug Administration. Therefore, all the tested products are compliant with the US regulations. Moreso, the bulk oil samples did not contain detectable levels of MOH. This study suggests that MOH accumulation in encapsulated products is likely due to the use of lubricants during encapsulation, rather than environmental sources such as oil spills since MOAH that are characteristic of weathered petroleum products were not identified in the UCM.

Cannabinoids biosynthesis in phytoplankton has attracted much attention due to the rapid development of genetic tools and the optimization of genetic transformation methods in microalgae. To monitor the biosynthesis process, proper sample preparation and practical instrumental methods are needed to measure the various precursors, intermediates, cannabinoids, and their degradation products. The objective of this study was to develop a sample preparation procedure for the quantification of olivetolic acid (OA), cannabigerolic acid (CBGA), cannabidiolic acid (CBDA), tetrahydrocannabinolic acid (THCA), olivetol (OL), cannabidiol (CBD), and tetrahydrocannabinol (THC) using single-quadrupole gas chromatography-mass spectrometry (GC-MS). Isochrysis galbana was used as the model matrix. After methanol extraction, samples were purified using solid phase extraction (SPE), silylated with N-methyl-N-(trimethylsilyl)trifluoroacetamide, and analyzed using GC-MS in electron ionization mode. A strong anion-exchange SPE efficiently recovered OA, CBGA, CBDA, and THCA. A graphitized carbon black SPE was necessary to purify OL, CBD, and THC. Both columns removed amino acids, sugars, polyols, and pigments from the algae extract and prepared samples that are suitable for silylation and GC-MS analysis. The total protocol, including solvent extraction, SPE, silylation, and GC-MS analysis, was validated in accordance with the ICH guidelines. Performance characteristics of our method are superior to existing protocols with similar complexity in the literature.

Highlights• 1,4-dioxane was degraded by anaerobic microbial communities with or without electron acceptors• Biodegradation rate was increased in nitrate-amended and aerated conditions• Trichloroethylene and temperature affected 1,4-dioxane biodegradation rate• Richness and diversity of microbial community decreased during the experiments• Pseudonocardiales , Rhizobiales , Bdellovibrionales, and Xanthobacteraceae were the dominant orders

The sea cucumber, Cucumaria frondosa, is harvested primarily for its muscular bands and body wall. Development of a nutraceutical product based on lipid recovered from its viscera would give commercial value to the entire organism; however, such development requires knowledge of the lipid and fatty acid (FA) profiles of the viscera. Here, we describe the lipid and FA composition of viscera recovered from C. frondosa harvested in coastal waters in the northwest Atlantic, taking into account variation due to harvest season. We found highest lipid content at ~29% in winter, with diacylglyceryl ethers (DAGE) comprising ~55% of the total lipid mass and triacylglycerols (TAG), phospholipids (PL) and monoacylglycerol ethers (MAGE) at 5–25% each. The branched chain FA, 12-methyltetradecanoic acid (12-MTA), represented 42% of total FA mass in DAGE. In summer, lipid content was lower at 24% and TAG was the dominate lipid, with proportions more than double that found in winter (45% vs. 20%); DAGE in summer dropped to ~30% of total lipids. In TAG, 12-MTA was much lower than found in DAGE in winter, at only 10% but eicosapentaenoic acid (EPA) content was ~20%, which brought the total EPA% to 28% of total FA—the highest among all three seasons. There was little effect of season on MAGE or PL proportions. These data can help harvesters maximize catch efforts in terms of lipid yield and profile.

Background: Molecular stable isotope ratios are a novel type of dietary biomarker with high sensitivity and specificity for certain foods. Among these, fatty acid carbon isotope ratios (CIRs) have strong potential but have not been investigated as dietary biomarkers. Objectives: We evaluated whether fatty acid CIRs and mass proportions were associated with meat, fish, and sugar-sweetened beverage (SSB) intake. Methods: Thirty-two men laged 46.2 +/- 10.5 y; BMI (kg/m(2)): 27.2 +/- 4.01 underwent a 12-wk inpatient dietary intervention at the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona. Men were randomly assigned to 1 of 8 dietary treatments varying the presence/absence of dietary meat, fish, and SSBs in all combinations. Fatty acid CIRs and mass proportions were measured in fasting blood samples and adipose tissue biopsies that were collected pre-and postintervention. Dietary effects were analyzed using multivariable regression and receiver operating characteristic AUCs were calculated using logistic regression. Results: CIRs of the several abundant SFAs, MUFAs and arachidonic acid (20:4n-6) in plasma were strongly associated with meat, as were a subset of these fatty acids in RBCs. Effect sizes in plasma ranged from 1.01 parts per thousand to 1.93 parts per thousand and were similar but attenuated in RBCs. Mass proportions of those fatty acids were not associated with diet. CIRs of plasma dihomo-gamma-linolenic acid (20:3n-6) and adipose palmitic acid (16:0) were weakly associated with SSBs. Mass proportions of plasma odd-chain fatty acids were associated with meat, and mass proportions of plasma EPA and DHA (20:5n-3 and 22:6n-3) were associated with fish. Conclusions: CIRs of plasma and RBC fatty acids show promise as sensitive and specific measures of dietary meat. These provide different information from that provided by fatty acid mass proportions, and are informative where mass proportion is not.

Climate change can have cascading impacts on biochemical reactions in aquatic ecosystems. Aquatic ectotherms can adapt to surrounding temperatures by using long-chain polyunsaturated fatty acids (LC-PUFAs) to maintain cell membrane fluidity. In a warming scenario, less LC-PUFA is needed to maintain fluidity. Our objective was to determine the impact of low dietary LC-PUFA and warm water temperature on growth, fatty acid (FA) storage, and expression of lipid metabolism–related transcripts in Atlantic salmon. Salmon (141 g) were fed two diets (high or low LC-PUFA) at either 12 °C or 16 °C for 16 weeks. Salmon weighed more and consumed more food at 16 °C and when fed the low-LC-PUFA diet. Liver and muscle FA mostly depended on diet rather than temperature. DHA in muscle was higher at 16 °C and in salmon fed the high-LC-PUFA diet. Levels of FA desaturation transcripts were more highly expressed at 16 °C and in salmon fed the low-LC-PUFA diet, which suggests synthesis of LC-PUFA. Overall, with slow, chronic temperature increases, salmon may adapt to low dietary LC-PUFA by synthesizing more when required.

Accurate information on diet composition is central to understanding and conserving carnivore populations. Quantitative fatty acid signature analysis (QFASA) has emerged as a powerful tool for estimating the diets of predators, but ambiguities remain about the timeframe of QFASA estimates and the need to account for species-specific patterns of metabolism. We conducted a series of feeding experiments with four juvenile male brown bears (Ursus arctos) to (1) track the timing of changes in adipose tissue composition and QFASA diet estimates in response to a change in diet and (2) quantify the relationship between consumer and diet FA composition (i.e., determine “calibration coefficients”). Bears were fed three compositionally distinct diets for 90–120 days each. Two marine-based diets were intended to approximate the lipid content and composition of the wild diet of polar bears (U. maritimus). Bear adipose tissue composition changed quickly in the direction of the diet and showed evidence of stabilization after 60 days. During hibernation, FA profiles were initially stable but diet estimates after 10 weeks were sensitive to calibration coefficients. Calibration coefficients derived from the marine-based diets were broadly similar to each other and to published values from marine-fed mink (Mustela vison), which have been used as a model for free-ranging polar bears. For growing bears on a high-fat diet, the temporal window for QFASA estimates was 30–90 days. Although our results reinforce the importance of accurate calibration, the similarities across taxa and diets suggest it may be feasible to develop a generalized QFASA approach for mammalian carnivores.

Young-of-the-year (YOY) striped bass (Morone saxatilis) suffer significant mortality during their first winter. While causes of this mortality are unclear, lipids may play role in adapting to winter stresses, including thermal change and food scarcity. To address this, YOY striped bass were placed in mesh cages in freshwater ponds in the fall (November) and were held until the end of winter, in March. Liver and white muscle tissue were sampled at the beginning and end of the study to compare concentrations of specific lipid classes and fatty acid composition. Muscle-tissue total lipid and triacylglycerol (TAG) was higher in March (late winter) samples. Additionally, concentrations of phosphatidylethanolamine (PE) were higher in the white muscle of striped bass sampled in March; this was accompanied by a decrease in proportions of 18:0 and 22:6n-3 in PE (from ~11 to 7% and 36 to 28%, respectively) and 18:1n-9 and 22:6n-3 in phosphatidylcholine (from ~15 to 10% and 24 to 18%, respectively). This suggests that these fish were not utilizing energy reserves in previously described ways and appear to rely more on other lipid classes or body tissues for overwinter survival than those analyzed in this study.

American Oil Chemists’ Society (AOCS)’s Official Method Cd 18-90 for p-Anisidine Value (pAV) is commonly used to evaluate secondary oxidation in fish oils. Flavoring agents in fish oil products may interfere with pAV and lead to inaccurate results. The Global Organization for EPA and DHA (GOED) recommends a protocol for calculating pAV of flavored fish oils, based on the assumption that flavors’ contribution to the pAV does not change over the course of oxidation. The objective of this study was to test this assumption. All fourteen flavors evaluated increased the pAV when added to fresh fish oil; chocolate-vanilla and lemon flavors generated the largest increase. Under accelerated oxidation conditions, both chocolate-vanilla and lemon flavors had a similar effect; oxidized flavored fish oils had lower pAV than oxidized fish oils with newly added flavors. This was due to either an antioxidant effect of the flavor or degradation of the flavor during oxidation. Following the GOED recommendation, we would have underestimated the oxidation in the flavored oils. For this reason, pAV of flavored fish oils should be considered with caution and used in combination with other secondary oxidation markers when possible.

Fatty acids are commonly used as biomarkers for making inferences about trophic relationships in aquatic and soil food webs. However, researchers are often unaware of the physiological constraints within organisms on the trophic transfer and modification of dietary biomarkers in consumers. Fatty acids are bioactive molecules, which have diverse structures and functions that both complicate and enhance their value as trophic tracers. For instance, consumers may synthesize confounding non-dietary sourced markers from precursor molecules, and environmental conditions also affect fatty acid composition. There is a vital need for more research on the uptake and transfer of trophic biomarkers in individual organisms in order to advance the field and make meaningful use of these tools at the scale of populations or ecosystems. This special issue is focused on controlled feeding experiments on a diverse taxonomic breadth of model consumers from freshwater, marine and soil ecosystems with a goal of creating a more integrated understanding of the connection between consumer physiology and trophic ecology. This article is part of the theme issue ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids'.

Marine water diatom Phaeodactylum tricornutum is a photosynthetic organism that is known to respond to the changing light environment and adapt to different temperatures to prevent photoinhibition and maintain its metabolic functions. The objective of the present study was to test whether light shift variations in different growth phases impact the growth and lipid metabolism of P. tricornutum. Thus, we investigated R exposure in different growth phases to find the most effective light shift condition. The results showed that substituting white light (W) by red light (R) under autotrophic conditions, a condition called red shift (RS), increased biomass and lipid content compared to levels found under continuous W or R exposure alone. We observed an increase by 2-fold biomass and 2.3-fold lipid content in RS as compared to W. No significant change was observed in the morphology of lipid droplets, but the fatty acid (FA) composition was altered. Specifically, polyunsaturated FAs were increased, whereas monounsaturated FAs decreased in P. tricornutum grown in RS compared to W control. Therefore, we propose that a light shift during the beginning of the stationary phase is a low-cost cultivation strategy to boost the total biomass and lipids in P. tricornutum.