Polyunsaturated fatty acids (PUFA), especially long-chain (i.e., ≥20 carbons) polyunsaturated fatty acids (LC-PUFA), are fundamental to the health and survival of marine and terrestrial organisms. Therefore, it is imperative that we gain a better understanding of their origin, abundance, and transfer between and within these ecosystems. We evaluated the natural variation in PUFA distribution and abundance that exists between and within these ecosystems by amassing and analyzing, using multivariate and analysis of variance (ANOVA) methods, >3000 fatty acid (FA) profiles from marine and terrestrial organisms. There was a clear dichotomy in LC-PUFA abundance between organisms in marine and terrestrial ecosystems, mainly driven by the C18 PUFA in terrestrial organisms and omega-3 (n-3) LC-PUFA in marine organisms. The PUFA content of an organism depended on both its biome (marine vs terrestrial) and taxonomic group. Within the marine biome, the PUFA content varied among taxonomic groups. PUFA content of marine organisms was dependent on both geographic zone (i.e., latitude, and thus broadly related to temperature) and trophic level (a function of diet). The contents of n-3 LC-PUFA were higher in polar and temperate marine organisms than those from the tropics. Therefore, we conclude that, on a per capita basis, high latitude marine organisms provide a disproportionately large global share of these essential nutrients to consumers, including terrestrial predators. Our analysis also hints at how climate change, and other anthropogenic stressors, might act to negatively impact the global distribution and abundance of n-3 LC-PUFA within marine ecosystems and on the terrestrial consumers that depend on these subsidies.

DHA (22:6n-3) may be derived from two dietary sources, preformed dietary DHA or through synthesis from α-linolenic acid (ALA; 18:3n-3). However, conventional methods cannot distinguish between DHA derived from either source without the use of costly labeled tracers. In the present study, we demonstrate the proof-of-concept that compound-specific isotope analysis (CSIA) by GC-isotope ratio mass spectrometry (IRMS) can differentiate between sources of brain DHA based on differences in natural C enrichment. Mice were fed diets containing either purified ALA or DHA as the sole n-3 PUFA. Extracted lipids were analyzed by CSIA for natural abundanceC enrichment. Brain DHA from DHA-fed mice was significantly more enriched (-23.32‰ to -21.92‰) compared with mice on the ALA diet (-28.25‰ to -27.49‰). The measured C enrichment of brain DHA closely resembled the dietary n-3 PUFA source, -21.86‰ and -28.22‰ for DHA and ALA, respectively. The dietary effect on DHAC enrichment was similar in liver and blood fractions. Our results demonstrate the effectiveness of CSIA, at natural C enrichment, to differentiate between the incorporation of preformed or synthesized DHA into the brain and other tissues without the need for tracers.

Docosahexaenoic acid (DHA) is an essential, omega-3, long-chain polyunsaturated fatty acid that is a key component of cell membranes and plays a vital role in vertebrate brain function. The capacity to synthesize DHA is limited in mammals, despite its critical role in neurological development and health. For humans, DHA is most commonly obtained by eating fish. Global warming is predicted to reduce the de novo synthesis of DHA by algae, at the base of aquatic food chains, and which is expected to reduce DHA transferred to fish. We estimated the global quantity of DHA (total and per capita) currently available from commercial (wild caught and aquaculture) and recreational fisheries. The potential decrease in the amount of DHA available from fish for human consumption was modeled using the predicted effect of established global warming scenarios on algal DHA production and ensuing transfer to fish. We conclude that an increase in water temperature could result, depending on the climate scenario and location, in a * 10 to 58% loss of globally available DHA by 2100, potentially limiting the availability of this critical nutrient to humans. Inland waters show the greatest potential for climate-warminginduced decreases in DHA available for human consumption. The projected decrease in DHA availability as a result of global warming would disproportionately affect vulnerable populations (e.g., fetuses, infants), especially in inland Africa (due to low reported per capita DHA availability). We estimated, in the worst-case scenario, that DHA availability could decline to levels where 96% of the global population may not have access to sufficient DHA. Keywords Aquaculture Á Climate change Á Docosahexaenoic acid (DHA) Á Fisheries Á Global warming Stefanie M. Colombo and Timothy F. M. Rodgers contributed equally to this project.

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It is commonly assumed that the most accurate data on fatty acid (FA) contents are obtained when samples are analyzed immediately after collection. For logistical reasons, however, this is not always feasible and samples are often kept on ice or frozen at various temperatures and for diverse time periods. We quantified temporal changes of selected FA (μg FAME per mg tissue dry weight) from 6 fish species subjected to 2 handling and 3 storage methods and compared them to FA contents from muscle tissue samples that were processed immediately. The following species were investigated: Common Carp (Cyprinus carpio), Freshwater Drum (Aplodinotus grunniens), Channel Catfish (Ictalurus punctatus), Antarctic Eelpout (Pachycara brachycephalum), Rainbow Trout (Oncorhynchus mykiss) and Arctic Charr (Salvelinus alpinus). The impact of storage method and duration of storage on FA contents were species-specific, but not FA-specific. There was no advantage in using nitrogen gas for tissue samples held on ice for 1 week; however, holding tissue samples on ice for 1 week resulted in a loss of FA in Charr. In addition, most FA in Trout and Charr decreased in quantity after being stored between 3 and 6 hours on ice. Freezer storage temperature (-80 or -20°C) also had a significant effect on FA contents in some species. Generally, we recommend that species with high total lipid content (e.g. Charr and Trout) should be treated with extra caution to avoid changes in FA contents, with time on ice and time spent in a freezer emerging as significant factors that changed FA contents.

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Effect of early introduction of microencapsulated diet to larvalAbstract An experimental microdiet prepared using an internal gelation method was used to partially replace the traditional live feed (Artemia) for larval Atlantic halibut, Hippoglossus hippoglossus L. Three trials were conducted with microdiet introduced at 20, 32, and 43 days post first feeding and larvae were sampled at approximately 2, 13, 23, and 33 days after microdiet introduction in each trial. The success of feeding was assessed by morphometrics and histological analysis of gut contents. Microdiet particles were readily consumed after a period of adaptation and provided an adequate source of nutrients with no significant increase in mortality in the microdiet-fed group compared to the control group. However, growth was limited and there was an increased incidence of malpigmentation of the eye and skin. Subtle changes in underlying digestive and developmental physiology were revealed by microarray analysis of RNA from control and experimental fish given microdiet from day20 post first feeding. Fifty-eight genes were differentially expressed over the four sampling times in the course of the trial and the 28 genes with annotated functions fell into five major categories: metabolism and biosynthesis, cell division and proliferation, protein trafficking, cell structure, and stress. Interestingly, several of these genes were involved in pigmentation and eye development, in agreement with the phenotypic abnormalities seen in the larvae.

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