Fatty Acid Biomarkers Research Articles

Biogeochemistry of fatty acids in a river-dominated Mediterranean ecosystem (Rhône River prodelta, Gulf of Lions, France): Origins and diagenesis

Major rivers transfer high loads of continental particulate organic matter to deltaic environments, where the impact on the biogeochemistry and productivity of coastal sediments depends on the sources and lability of these inputs. Our aims are to provide new insights into the reactivity of riverine inputs in coastal environments and to delineate the parameters controlling their fate in these dynamic systems. Sediment cores were collected from a Mediterranean deltaic system (the Rhône prodelta and its adjacent shelf) during a period of moderate river discharge (Spring 2007) and analyzed for their fatty acid composition. Sediment properties were also described using biochemical bulk analyses (organic carbon and lipids), granulometry and profiles of redox potential. Based on the bulk compositional changes and hierarchical clustering of the fatty acid biomarkers, we determined the principal sources of organic matter and their spatial distribution. Fatty acids were primarily of continental origin in the prodelta, shifting to a higher contribution from marine sources in the shelf area. Fatty acids derived from both continental and marine sources were efficiently degraded in the sediments by microbial decay processes in the upper oxic layer. Degradation rate constants calculated from the down-core decreases in concentrations indicate that fatty acid degradation was enhanced in sediments influenced by the Rhône River. The most important parameters affecting fatty acid preservation were the inherent stability of individual molecular components and their physical association with mineral matrices, the source and freshness of the inputs, and the depositional environment (redox condition, accumulation rates).

Effects of Different Organic Manures on the Biochemical and Microbial Characteristics of Albic Paddy Soil in a Short-Term Experiment

This study aimed to evaluate the effects of chemical fertilizer (NPK), NPK with livestock manure (NPK+M), NPK with straw (NPK+S), and NPK with green manure (NPK+G) on soil enzyme activities and microbial characteristics of albic paddy soil, which is a typical soil with low productivity in China. The responses of extracellular enzyme activities and the microbial community diversity (determined by phospholipid fatty acid analysis [PLFA] and denaturing gradient gel electrophoresis [DGGE]) were measured. The results showed that NPK+M and NPK+S significantly increased rice yield, with NPK+M being approximately 24% greater than NPK. The NPK+M significantly increased soil organic carbon (SOC) and available phosphate (P) and enhanced phosphatase, β-cellobiosidase, L-leucine aminopeptidase and urease activities. The NPK+S significantly increased SOC and available potassium (K) and significantly enhanced N-acetyl-glucosamidase, β-xylosidase, urease, and phenol oxidase activities. The NPK+G significantly improved total nitrogen (N), ammonium N, available P, and N-acetyl-glucosamidase activity. The PLFA biomass was highest under NPK+S, followed by NPK+M and NPK+G treatments. Principal component analysis (PCA) of the PLFA indicated that soils with NPK+M and NPK+S contained higher proportions of unsaturated and cyclopropane fatty acids (biomarkers of fungi and gram-negative bacteria) and soil under NPK+G contained more straight chain saturated fatty acids (representing gram-positive bacteria). PCA of the DGGE patterns showed that organic amendments had a greater influence on fungal community. Cluster analysis of fungal DGGE patterns revealed that NPK+G was clearly separated. Meanwhile, the bacterial community of NPK+M treatment was the most distinct. RDA analysis revealed changes of microbial community composition mostly depended on β-xylosidase, β-cellobiosidase activities, total N and available K contents. The abundances of gram-negative bacterial and fungal PLFAs probably effective in improving fertility of low-yield albic paddy soil because of their significant influence on DGGE profile.

Trophic niche of two co-occurring ophiuroid species in impacted coastal systems, derived from fatty acid and stable isotope analyses

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 525:127-141 (2015) - DOI: https://doi.org/10.3354/meps11169 Trophic niche of two co-occurring ophiuroid species in impacted coastal systems, derived from fatty acid and stable isotope analyses Aline Blanchet-Aurigny1,*, Stanislas F. Dubois1, Claudie Quéré2, Monique Guillou3, Fabrice Pernet2 1IFREMER, Laboratoire d’Ecologie Benthique, Département Océanographie et Dynamique des Ecosystèmes, Centre de Bretagne, BP70, 29280 Plouzané, France 2IFREMER, Laboratoire de Physiologie Fonctionnelle des Organismes Marins, LEMAR UMR CNRS IRD 6539, Centre de Bretagne, BP70, 29280 Plouzané, France 3Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, LEMAR UMR CNRS IRD 6539, place Nicolas Copernic, 29280 Plouzané, France *Corresponding author: ablanche@ifremer.fr ABSTRACT: The trophic niches of 2 common co-occurring ophiuroids, Ophiocomina nigra and Ophiothrix fragilis (Echinodermata, Ophiuroidea), in 2 contrasting coastal systems of Brittany (France) were investigated. We used a combination of fatty acid biomarkers derived from neutral lipids and stable isotopic compositions to explore the contributions of oceanic versus continental inputs to the ophiuroids’ diet. We investigated 2 different systems with an inshore versus offshore comparison. We sampled potential food sources and surveyed organisms every 2 mo for 1 yr. Spatio-temporal variations in stable isotopes and fatty acid profiles of the ophiuroids were generally low compared to interspecific differences. Fatty acid markers showed that both ophiuroids relied on diatom inputs. However, a more δ15N-enriched isotopic composition as well as a more balanced plant- versus animal-derived fatty acid composition in O. nigra suggest that a broader range of food sources are being used by this species irrespective of location or sampling time. The positive correlation between the 18:1n-9/18:1n-7 fatty acid ratio and δ15N values indicates a higher trophic position for O. nigra (suggesting an omnivorous feeding mode), whereas O. fragilis appears to be more herbivorous. Moreover, the low polyunsaturated/saturated fatty acid ratio associated with elevated bacterial fatty acid markers indicates that O. nigra preferentially consumes detritus, while O. fragilis relies more on fresh phytoplankton-derived material. Both stable isotope and fatty acid analyses suggest that terrestrial inputs do not contribute significantly to the diet of these ophiuroids. However, phytodetritus derived from decomposing green macroalgae contributed to the diet of O. nigra in the Bay of Douarnenez. KEY WORDS: Echinoderm · Feeding ecology · Ophiocomina nigra · Ophiothrix fragilis · Trophic markers · Green algae Full text in pdf format Supplementary material PreviousNextCite this article as: Blanchet-Aurigny A, Dubois SF, Quéré C, Guillou M, Pernet F (2015) Trophic niche of two co-occurring ophiuroid species in impacted coastal systems, derived from fatty acid and stable isotope analyses. Mar Ecol Prog Ser 525:127-141. https://doi.org/10.3354/meps11169 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 525. Online publication date: April 09, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Serum Biomarkers of Dietary Fatty Acids are Associated with Abdominal Obesity Measures in a Large Population‐based Cohort of Men and Women.

Recent feeding trials suggest that the major saturated fatty acid (FA) Palmitic acid (PA, 16:0) and the major polyunsaturated FA linoleic acid (LA, 18:2n‐6) has diverse effects on abdominal fat accumulation, suggesting a beneficial role of LA on fat deposition.ObjectiveTo investigate associations between these FAs assessed in serum cholesterol esters (CE) and anthropometric measures of abdominal obesity.MethodsLA and PA were measured by gas chromatography in serum CE. Sagittal abdominal diameter (SAD), waist circumference (WC), and waist‐hip ratio (WHR) were assessed by anthropometry in a population‐based cross‐sectional study of 3965 (1920 men and 2045 women) 60‐year old participants living in Stockholm county, Sweden.ResultsPA was positively correlated with SAD, WC, and WHR in men (r= 0.15, 0.16, and 0.14, respectively; all p ˂0.001), whereas inverse correlations were observed for LA in both men (r= ‐0.23, ‐0.22, and ‐0.22, respectively; p ˂0.001) and women (r= ‐0.15, ‐0.18, and ‐0.18, respectively; p ˂0.001).Overall, these associations remained after adjusting for lifestyle factors.ConclusionsLinoleic Acid was consistently inversely associated with all abdominal obesity measures in both men and women. Palmitic Acid showed positive correlations in men only. These findings support recent interventional data suggesting that a higher relative intake of dietary LA from vegetable oils is associated with decreased abdominal adiposity.

Nitrogen limitation of heterotrophic biofilms in boreal streams

Summary Nutrient limitation of the biofilm is fundamental to stream ecosystem processes, as microbial activity shapes the biological availability and biogeochemical cycling of carbon and nutrients. We used nutrient‐diffusing substrata (NDS) to investigate heterotrophic nutrient limitation of microbial respiration (MR) across 20 streams draining boreal landscapes in northern Sweden. We also explored variation in microbial biomass and community structure of biofilms that developed on NDS using phospholipid fatty acid (PLFA) biomarkers. Limitation was determined as a significant response of MR and biomass production on cellulose surfaces to enrichment with nitrogen (N), phosphorus (P) or N + P, relative to controls. Microbial respiration was N‐limited, with an average 3.3‐fold increase on N‐amended NDS. Nitrogen limitation decreased, and control rates of MR increased, with greater background concentrations of inorganic N across the sites. In contrast to MR, microbial biomass was primarily N‐limited but was greatest for the N + P NDS. Accordingly, differences in respiratory versus biomass responses to nutrient addition resulted in significantly greater biomass‐specific MR on N‐amended NDS compared to all other treatments. In addition, PLFA biomarkers indicated distinct microbial communities on N and N + P NDS compared to controls and/or P NDS. Greater MR and biomass, and the development of distinct microbial communities, when supplied with inorganic N suggest that factors which alter aquatic N loading during autumn may have important implications for ecosystem processes and the biogeochemistry of boreal streams and rivers. Our findings add to a growing body of evidence that the productivity of Fennoscandian boreal landscapes is constrained by N availability.

Fatty acid biomarkers to verify cyanobacteria feeding abilities of herbivorous consumers

To search useful fatty acid biomarkers for cyanobacteria feeding abilities of control organisms, we compared fatty acid composition of six cultured algal species in four taxonomic groups (Cryptophyceae, Bacillariophyceae, Chlorophyceae, and Cyanophyceae) and evaluated several fatty acid biomarkers using data from three lakes that varied in trophic status. In addition, a laboratory feeding experiment was conducted to verify fatty acid markers for cyanobacteria using Selenastrum capricornutum (Chlorophyceae) and Microcystis aeruginosa (Cyanophyceae). Two strains of M. aeruginosa had the highest content of 18:3ω6 while Anabaena sp. had a relatively high content of 18:1ω7 among the six species. Both 18:1ω7 and 18:3ω6 (γ-linolenic acid, GLA) concentrations showed significant linear relationships with cyanobacteria biomass in natural systems. In the laboratory feeding experiment, a principal component analysis score plot indicate that fatty acid composition of Branchinella kugenumaensis fed with M. aeruginosa became similar to that of the cyanobacterial population. In S-plot of partial least square discriminant analysis, 18:3ω6 and 18:1ω7 were selected for fairy shrimps feeding on M. aeruginosa, whereas 18:3ω3 (ALA, α-linolenic acid) and 18:1ω9 were selected for those feeding on S. capricornutum. 18:3ω6 content of B. kugenumaensis fed with M. aeruginosa significantly increased after the third day and 18:1ω7 content was significantly different from the other feeding group after six days. In particular, 18:3ω6 appeared to be a useful fatty acid biomarker for M. aeruginosa in tracing trophic relations of herbivorous organisms in freshwater ecosystems.

The effects of earthworms Eisenia spp. on microbial community are habitat dependent

The effects of earthworms Eisenia spp. on microorganisms of three different habitat soil, compost, and vermiculture were studied. Microbial communities of gut and fresh faeces of earthworms and substrates, the worms were collected from, were analysed. Microbial biomass and composition of the total microbial community were examined using phospholipid fatty acid (PLFA) biomarkers. Archaeal and bacterial communities were studied by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE). The culturing methods were used for assessment of counts, species richness and growth strategy of bacteria.In comparison with the substrates, the viable microbial biomass and the group of non-ester-linked PLFAs indicative of anaerobes were higher in both the gut and faeces of all earthworm populations. The prokaryotic community evaluated using DGGE revealed that archaeal community structure in the gut and faeces of earthworms from populations differed from that in substrates, whereas the passage through the gut had less influence on the bacterial community structure, particularly in compost and vermiculture.The counts of culturable bacteria increased due to gut passage only in forest and vermiculture populations. The fast-growing bacteria increased due to gut passage only in forest soil population. Actinobacteria (Arthrobacter, Microbacterium, Lechevalieria and Nesterenkonia) and Firmicutes (Bacillus and Paenibacillus) were generally favoured in substrates and their species richness decreased with gut passage, whereas Gammaproteobacteria (Aeromonas, Enterobacter, Pseudomonas and Salmonella) dominated in gut contents. The impact of earthworm activity on the microbial community was higher in nutrient-poor forest soil than in nutrient-rich compost and vermiculture substrates.

Rapid screening of phytoremediation effluents by off-line tetramethylammonium hydroxide assisted thermochemolysis

Tetramethylammonium hydroxide-assisted thermochemolysis performed in an off-line mode proved a useful tool in determining organic compounds in the effluent from laboratory-scale phytoremediation systems. Studies were performed with artificial wastewaters contaminated with xylenols and densely rooted Juncus effuses plants. Analytes in these molecular-level based studies included xylenol substrates, an array of stable intermediates such as low molecular weight carboxylic acids and oxidative coupling products (tetramethyl biphenyldiols, tetramethyl diphenylether monools), diagnostic fatty acid biomarkers, as well as lignin-, carbohydrate-, and protein-based phenols and carboxylic acids. Lignin-based breakdown products belonged to p-hydroxyphenyl- and guaiacyl-units, with lower abundance of syringyl units and the dominance of acids over phenols. Monomeric lignin-, protein- and carbohydrate-based breakdown products could not be detected in the non-treated lyophilized effluent. The formation of diketopiperazines pointed to soluble peptides and proteins. The procedure described herein can easily be applied in every modern laboratory to characterize underlying processes in phytoremediation.

Dietary and biomarker estimates of fatty acids and risk of colorectal cancer.

The associations between intake of or circulating fatty acids and risk of colorectal cancer (CRC) are unclear. We examined prospectively the associations between dietary or biomarker fatty acids and CRC. For 41,514 men and women, aged 40-69 years, baseline (1990-94) dietary intakes of fatty acids were estimated using a food frequency questionnaire and plasma phospholipid (PPL) fatty acids were measured for 4,205 participants including 395 CRC cases, according to a case-cohort design. Hazard ratios were computed using Cox regression adjusting for education, alcohol intake, smoking status, physical activity and total energy intake; and stratified for gender, ethnicity and family history of cancer, with age as the time scale. We assessed the heterogeneity of associations with colon and rectal cancers. PPL saturated fatty acids (SFAs) were positively associated with CRC risk, while total n-3 polyunsaturated fatty acids (PUFA) and long chain marine n-3 PUFAs showed inverse associations, significant only for 22:5 n-3. No significant associations were observed for dietary fatty acid intakes but positive associations with CRC of borderline significance were seen for both dietary and PPL linoleic acid. Positive associations with dietary palmitic acid (16:0), MUFAs and n-6 PUFAs were seen for rectal but not colon cancers. PPL 22:6 n-3 was inversely associated with rectal cancer. Limiting intakes of SFAs and MUFAs could be assisted by following existing guidelines to limit red and processed meats which are important sources in the Australian diet. Our observations regarding linoleic acid should be examined further.

Identification of potential erythrocyte phospholipid fatty acid biomarkers of advanced lung adenocarcinoma, squamous cell lung carcinoma, and small cell lung cancer.

New biomarkers for lung cancer would be valuable. Our aim was to analyze the fatty acid profiles of the main phospholipid species in erythrocytes from patients with advanced squamous cell lung carcinoma (SCC), lung adenocarcinoma (ADC), and small cell lung cancer (SCLC) and benign lung diseases (chronic obstructive pulmonary disease (COPD) and asthma) to determine the fatty acids that could be use as lung cancer markers. Twenty-eight, 18, 14, 16, and 15 patients with, respectively, SCC, ADC, SCLC, asthma, and COPD and 50 healthy subjects were enrolled in the study. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by receiver operating characteristic (ROC) curve analysis. The fatty acid profiles changed significantly in the different pathologies analyzed. Based on the diagnostic yields and operating characteristics, the most significant fatty acids that might be used as biomarkers were as follows: ADC--arachidonic acid (20:4n6) in phosphatidylcholine and oleic acid (18:1n9) in phosphatidylethanolamine (PE); SCC--eicosapentaenoic acid (20:5n3) in PE and palmitic acid (16:0) in phosphatidylserine + phosphatidylinositol (PS+PI); SCLC--eicosadienoic acid (20:2n6) in PS+PI and lignoceric acid (24:0) in sphingomyelin. In conclusion, fatty acids from erythrocyte phospholipid species might serve as biomarkers in the diagnosis, and probably in other aspects related to clinical disease management, of ADC, SCC, and SCLC.

Predominance and sources of alkane and fatty acid biomarkers in the surface sediments of Chitrapuzha River (South India).

Surface sediment samples were collected from Chitrapuzha (Cochin) estuarine system to identify the natural and anthropogenic origin of organic matter. The distribution and sources of organic matter were assessed with the help of fatty acid and alkane biomarkers. Fatty acids ranging from C12 to C28 were identified and C16:0 was the most abundant fatty acid, which contributed between 23.5 % and 52.4 % to total fatty acids. The low levels of polyunsaturated fatty acids indicate the effective bacterial recycling of algal fatty acids during the whole settling and depositing process. Aliphatic hydrocarbons ranging from C12 to C33 were identified and the total concentration ranged from 7876 to 43,357 ng g(-1). The presence of unresolved complex mixtures and lower pristane to phytane ratios indicates the petroleum contamination in the study area.

The effect of oxygen on fatty acid composition of soil micromycetes

The aim of this work was to describe changes in fatty acid profiles of fungi growing under artificial conditions of oxygen depletion. In total, 133 fungal strains belonging to eight orders were isolated from cattle impacted soils and tested. The analysis of the ten most frequent fatty acids revealed significant shift in fatty acids composition as a result of decreasing oxygen level. Taxonomic- as well as aeration-dependent changes in the amounts of fungal biomarker fatty acids (18:1ω9 and 18:2ω6,9) were found. Therefore, the ratio of these two fatty acids could be considered as an indicator of anaerobic, microaerobic or aerobic conditions in soil. Moreover, fatty acid-based estimation of fungal biomass in soils should be performed as a sum of both biomarker fatty acids and with respect to the soil characteristics as well as to the composition of fungal community.

Source-age dynamics of estuarine particulate organic matter using fatty acid δ 13 C and Δ14 C composition

This study used a multiproxy approach to elucidate the source and age composition of estuarine particulate organic matter (POM) using bulk stable isotopes (δ13CPOC), fatty acid (FA) biomarkers, and compound specific isotopic analyses in surface waters along the Delaware River and Bay (Delaware Estuary, hereafter). δ13C values of FA (δ13CFA) ranged more widely (−30.9‰ to −21.8‰) than δ13CPOC (−27.5‰ to −23.5‰), providing greater insight about POM sources along the estuary. δ13C values of C16:0 phospholipid FA (primarily, aquatic sources) increased along the salinity gradient (−29.8‰ to −23.4‰), while δ13CFA values of long-chain neutral fatty acid (terrestrial sources) decreased (−28.6‰ to −30.9‰). δ13CFA values for C18's FA indicated the importance of marsh-derived organic matter within Delaware Estuary. Compound specific radiocarbon analysis showed the heterogeneous age structure of FA associated with POM (FAPOM). 14C ages of FA ranged from modern (postbomb) to 1790 BP; aged FA (120 BP to 1700 BP) derived primarily from the watershed, whereas modern FA were produced within Delaware Estuary. 14C ages of short-chain FA (aquatic sources) reflected differences in the age of dissolved inorganic carbon along the estuary and had older 14C ages at the river end-member. 14C ages of FA from terrigenous sources were older than water and sediment residence times indicating this source derived from the watershed. This study is the first to document the complex age distribution of FAPOM along the estuarine salinity gradient and shows that inorganic carbon sources, watershed inputs and autochthonous production contribute to variation in the ages of POM.

Macrophytes and periphyton carbon subsidies to bacterioplankton and zooplankton in a shallow eutrophic lake in tropical China

The subsidy of carbon derived from macrophytes and associated periphyton to bacterioplankton and zooplankton in subtropical shallow eutrophic Huizhou West Lake in China was analyzed using carbon stable isotope signatures. A restored part of the lake dominated by macrophytes was compared with an unrestored phytoplankton-dominated part. Macrophytes, periphyton, seston, and zooplankton were sampled every two months to determine natural-abundance carbon isotope ratios (δ13C). The δ13C of phytoplankton and bacterioplankton was determined from δ13C of fatty acid biomarkers. Macrophytes and associated periphyton had similar δ13C values and were the most enriched in 13C of all measured organic carbon pools. A macrophyte–periphyton carbon isotopic signal was detected in particulate organic carbon, bacterioplankton, and zooplankton in the macrophyte-dominated lake part, which was demonstrated by a significant enrichment in 13C compared with the unrestored part, while phytoplankton and dissolved organic carbon had similar δ13C values in both lake parts. A two-source (macrophytes–periphyton and phytoplankton) mixing model showed that macrophytes–periphyton potentially contributed 14–85% (average 55%) to bacterioplankton in the macrophyte-dominated lake part, depending on season. The macrophytes–periphyton contribution to zooplankton seasonally varied between 26% and 86%, with an average of 47%. The contribution of macrophytes–periphyton to bacterioplankton increased with increasing macrophyte biomass relative to phytoplankton biomass (indicated by chlorophyll a). Carbon from macrophytes with associated periphyton subsidizes bacterioplankton and zooplankton, likely enhancing the cascading effects of planktonic food webs, providing an additional explanation for the stability of a clear-water state in shallow lakes dominated by macrophytes.

Spatio-temporal variations in the composition of organic matter in surface sediments of a mangrove receiving shrimp farm effluents (New Caledonia)

In order to investigate spatio-temporal variations in the composition and origin of the benthic organic matter (OM) at the sediment surface in mangrove receiving shrimp farm effluents, fatty acid (FA) biomarkers, natural stable isotopes (δ13C and δ15N), C:N ratios and chlorophyll-a (chl-a) concentrations were determined during the active and the non-active period of the farm. Fatty acid compositions in surface sediments within the mangrove forest indicated that organic matter inputs varied along the year as a result of farm activity. Effluents were the source of fresh particulate organic matter for the mangrove, as evidenced by the unsaturated fatty acid (UFA) distribution. The anthropogenic MUFA 18:1ω9 was not only accumulated at the sediment surface in some parts of the mangrove, but was also exported to the seafront. Direct release of bacteria and enhanced in situ production of fungi, as revealed by specific FAs, stimulated mangrove litter decomposition under effluent runoff condition. Also, microalgae released from ponds contributed to maintain high benthic chl-a concentrations in mangrove sediments in winter and to a shift in microphytobenthic community assemblage. Primary production was high whether the farm released effluent or not which questioned the temporary effect of shrimp farm effluent on benthic microalgae dynamic. This study outlined that mangrove benthic organic matter was qualitatively and quantitatively affected by shrimp farm effluent release and that responses to environmental condition changes likely depended on mangrove stand characteristics.

Importance of sympagic production to Bering Sea zooplankton as revealed from fatty acid-carbon stable isotope analyses

We analyzed the fatty acid (FA) composition and carbon stable isotope ratios of indi- vidual FAs (δ 13 CFA) of 3 zooplankton species (Themisto libellula, Calanus marshallae/glacialis, and Thysanoessa raschii) sampled from the Bering Sea during winter maximum ice extent, spring ice melt, and summer ice-free conditions in 2009 and 2010. Our goal was to assess diets of these eco- logically important species and estimate the proportional contribution of pelagic and sympagic carbon sources to their diets. FA profiles showed little variation in diet within species between ice conditions or years but revealed differences in diet among species. FA biomarkers confirmed that T. libellula was predominately carnivorous and that C. marshallae/glacialis and T. raschii were primarily herbivorous. Estimates from 4 stable isotope mixing models using combinations of δ 13 CFA values of diatom FA markers (16:1n-7, 20:5n-3), and a flagellate FA marker (22:6n-3) showed that substantial, albeit highly variable, proportions of these FAs originated from organic matter originating from sea ice algae (T. libellula 36 to 72%, C. marshallae/glacialis 27 to 63%, and T. raschii 39 to 71%). Our results suggest that ice algae may be an important food source for zooplankton when water column phytoplankton are not available during critical periods in their life history. Predicted increases in water column phytoplankton production in the Bering Sea may help offset the expected reduction in ice algal production and any detrimental effects that this might have on consumers such as zooplankton.

Prospective association of fatty acids in the de novo lipogenesis pathway with risk of type 2 diabetes: the Cardiovascular Health Study

Experimental evidence suggests that hepatic de novo lipogenesis (DNL) affects insulin homeostasis via synthesis of saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs). Few prospective studies have used fatty acid biomarkers to assess associations with type 2 diabetes. We investigated associations of major circulating SFAs [palmitic acid (16:0) and stearic acid (18:0)] and MUFA [oleic acid (18:1n-9)] in the DNL pathway with metabolic risk factors and incident diabetes in community-based older U.S. adults in the Cardiovascular Health Study. We secondarily assessed other DNL fatty acid biomarkers [myristic acid (14:0), palmitoleic acid (16:1n-7), 7-hexadecenoic acid (16:1n-9), and vaccenic acid (18:1n-7)] and estimated dietary SFAs and MUFAs. In 3004 participants free of diabetes, plasma phospholipid fatty acids were measured in 1992, and incident diabetes was identified by medication use and blood glucose. Usual diets were assessed by using repeated food-frequency questionnaires. Multivariable linear and Cox regression were used to assess associations with metabolic risk factors and incident diabetes, respectively. At baseline, circulating palmitic acid and stearic acid were positively associated with adiposity, triglycerides, inflammation biomarkers, and insulin resistance (P-trend < 0.01 each), whereas oleic acid showed generally beneficial associations (P-trend < 0.001 each). During 30,763 person-years, 297 incident diabetes cases occurred. With adjustment for demographics and lifestyle, palmitic acid (extreme-quintile HR: 1.89; 95% CI: 1.27, 2.83; P-trend = 0.001) and stearic acid (HR: 1.62; 95% CI: 1.09, 2.41; P-trend = 0.006) were associated with higher diabetes risk, whereas oleic acid was not significantly associated. In secondary analyses, vaccenic acid was inversely associated with diabetes (HR: 0.56; 95% CI: 0.38, 0.83; P-trend = 0.005). Other fatty acid biomarkers and estimated dietary SFAs or MUFAs were not significantly associated with incident diabetes. In this large prospective cohort, circulating palmitic acid and stearic acid were associated with higher diabetes risk, and vaccenic acid was associated with lower diabetes risk. These results indicate a need for additional investigation of biological mechanisms linking specific fatty acids in the DNL pathway to the pathogenesis of diabetes.

Relative validation of the dietary intake of fatty acids among adults in the Swedish National Dietary Survey using plasma phospholipid fatty acid composition.

The aims of a national dietary study are several-fold. One purpose is to monitor the intake of foods and nutrients in the population and to compare intakes with dietary recommendations. It is, however, difficult to measure dietary fat intake and plasma biomarker fatty acid (FA) composition may be used as an objective measure of dietary fat intake. Thus, the relative ability of a diet record to capture habitual fat intake was validated against biomarker FA. Dietary fat intake was measured in a novel self-assisted web-based 4-d food record - the 'Riksmaten' method. Spearman rank correlations between dietary FA, certain food groups (fish-shellfish, dairy products, meat and sausages, and spreads) and the fat content of these food groups and biomarker FA were explored. Participants were 150 women and 129 men, aged 18-80 years, who took part in the Swedish National Dietary Survey, Riksmaten adults 2010-11. Blood samples were collected on average 20 d after the diet record and FA composition was measured in plasma phospholipids by GLC. Total n-3 FA (r 0·31), EPA (r 0·34) and DHA (r 0·42) were correlated between plasma and diet (all P≤0·001). Adjustment for covariates attenuated the relationships. Linoleic acid was only marginally correlated (r 0·15; P=0·06) in women. Plasma pentadecaenoic acid and heptadecaenoic acid were correlated with dairy product intake as previously reported. In conclusion, the Riksmaten method appears valid for the purpose of collecting data on dietary fat composition, at least in a healthy adult population.

Obligate hydrothermal vent fauna at East Diamante submarine volcano (Mariana Arc) exploit photosynthetic and chemosynthetic carbon sources

Two volcanic cones in the degraded caldera of East Diamante submarine volcano (Mariana Arc) were surveyed and sampled in April 2004 as part of the 'Submarine Ring of Fire 2004' expedition. The first images revealed hydrothermal venting within the photic zone and a striking overlap between chemosynthetic and photosynthetic communities. We used fatty acid biomarkers and bulk stable isotopes to determine the relative importance of chemosynthetic and photosynthetic material in the diets of invertebrates at 6 vent sites (Eastern Cone: Barnacle Beach and Black Forest; Central Cone: Floc Storm, Boulder Vent, Mid-cone, and Fe-Mn Crust) and 1 non-vent site (Central Cone: Aquarium). Principal components analysis revealed depth-related dietary differences: vent-obligate invertebrates at Barnacle Beach (~460 m) belonged to a purely chemosynthetic food web, non-vent organisms at Aquarium (179 m) had diets based on the prod- ucts of photosynthesis, and most of the invertebrates at Black Forest (349 m) and Central Cone vent sites (247�288 m) had mixed chemosynthetic/photosynthetic diets. Carbon stable isotope ratios corroborated the photosynthetic input in the diets of the vent-obligate invertebrates. Long- chain polyunsaturated fatty acids were found in overlying waters and in detritus. We suggest that photosynthetic material arrives at East Diamante in the form of marine snow. Photic zone hydro- thermal venting has now been found on several arc volcanoes in the western Pacific Ocean. Our study underscores the potential influence of benthicpelagic coupling on trophic interactions and community structure for vent-obligate species in such settings.

Bouncing back: plant-associated soil microbes respond rapidly to prairie establishment.

It is well established that soil microbial communities change in response to altered land use and land cover, but less is known about the timing of these changes. Understanding temporal patterns in recovering microbial communities is an important part of improving how we assess and manage reconstructed ecosystems. We assessed patterns of community-level microbial diversity and abundance in corn and prairie plots 2 to 4 years after establishment in agricultural fields, using phospholipid fatty acid biomarkers. Principal components analysis of the lipid biomarkers revealed differing composition between corn and prairie soil microbial communities. Despite no changes to the biomass of Gram-positive bacteria and actinomycetes, total biomass, arbuscular mycorrhizal fungi biomass, and Gram-negative bacteria biomass were significantly higher in restored prairie plots, approaching levels found in long-established prairies. These results indicate that plant-associated soil microbes in agricultural soils can shift in less than 2 years after establishment of perennial grasslands.