Differential response of fatty acid composition in the different lipid classes from particulate matter in a high arctic fjord (Kongsfjorden, Svalbard)

Lipid classes and the respective fatty acid composition of natural particulate matter were studied on a seasonal basis in the Arctic fjord Kongsfjorden (Svalbard) during the early summer of 2006 and the spring, summer of 2007. Polar lipids were the major lipid class most of the times in 2006 and at all times in 2007. Among neutral lipids triglycerides were dominant. Polar lipids were divided into glycolipids (chloroplast membranes) and phospholipids (live cell membranes). Glycolipids were further divided into monogalactosyldiglycerides (MGDG), the major glycolipid, followed by digalactosyldiglycerides (DGDG) and Sulfoquinovosyldiglycerides (SQDG). In 2007, changes in both polar lipid constituents showed similar increasing trend from May to mid June but subsequently showed opposite trends from July to September. The seasonal pattern of particulate glycolipids was one of the low concentrations of MGDG in June followed by an increase between late June and September. SQDG exhibited a similar trend while DGDG displayed an opposing trend. In 2007, fatty acid composition of phospholipids, glycolipids and neutral lipids was dominated by saturated acids at all times followed by mono unsaturated acids and polyunsaturated acids with docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3) and 18:5n-3 as major contributors. Glycolipid fatty acid pattern differed from that of phospholipids, showing a more important contribution of 18:5n-3. Neutral lipid composition differed from the other two classes by a larger contribution of 16:1n-5 and percentages of EPA, DHA, 18:5 and 18:4n-3 lower than in the two structural classes. Factorial correspondence analysis (FCA) of the fatty acid composition of all classes illustrated a seasonal transition in species composition and/or physiological states for the phospholipids and the different processes of chloroplast membrane adaptation in relation to taxonomic changes for the glycolipids. Neutral lipid changes were more complex because of the combined influence of growth rates, nutrient limitations and community shifts. The differential response of the different lipid classes is discussed in relation with the complex interactions between community structure, environmental adaptation and metabolic processes. (C) 2013 Published by Elsevier B.V

Polar and neutral lipid composition in the pelagic tunicate Pyrosoma atlanticum

Structure and functioning of colonial pyrosomes are largely undescribed and their lipid characteristics have received limited attention. The aim of this paper is to fill this gap on one of the dominant species Pyrosoma atlanticum. Lipid content is tightly coupled to size and weight. Lipid composition shows a large dominance of structural polar lipids. Neutral lipids were dominated by sterols with low levels of acylglycerols and free fatty acids. Phospholipids show a dominance of PC with intermediate percentages of PE and DPG. Other constituents (PS, PI, LPC, sphingolipids) were present at lower levels. Fatty acid composition of DAG and TAG showed a dominance of saturated acids (16:0, 14:0), DHA and intermediate levels of MUFA. Phospholipids were dominated by DHA with values exceeding 30% of total FA in all categories except for PI, where lower percentages occurred. Saturated acids were second in abundance with MUFA showing intermediate concentrations. Sterols were dominated by 24-methylcholesta-5,22E-dien-3 beta-ol with more than 22% of the total sterol. Cholesterol (cholest-5-en-3 beta-ol) represented only 12 % of the total while 24-methylcholesta-5,24(28)E-dien-3 beta-ol accounted for 11% of the total sterols. The low levels of triacylglycerols and free fatty acids, coupled with high concentrations of glycolipids and phytoplankton-derived degraded chloropigments, is evidence of a direct link with the digestive activity and substantiate the idea of a high physiological turnover as an alternative to large lipid accumulation. The fatty acid and sterol profiles are consistent with a diverse phytoplankton diet, and a strong contribution of phospholipid classes to energy needs, including locomotion

Fatty acid composition of Mediterranean fin whale Balaenoptera physalus blubber with respect to body heterogeneity and trophic interaction

International audienceBlubber blocks were collected from both a recently killed (dead whale complete samples; DWCS) and several live (living whale partial samples; WPS) Mediterranean fin whales Balaenoptera physalus and analyzed for their lipid and fatty acid (FA) composition. Mean lipid content for the different body parts of DWCS samples ranged from 33 to 69% of the wet weight and triacylglycerols (TG) represented 80 to 86% of the total lipids; 36 FAs were observed in all blubber layers in greater than trace amounts (>0.2%). Multivariate correspondence analysis showed that the major variation in FAs structure was related to body position (dorsal versus ventral and lateral) and to a lesser extent to the blubber stratification. Dorsal blubber TG could be distinguished from the other locations by the relative levels of 20:0 and 20:1 FA, whereas polyunsaturated fatty acids (PUFA) were the main descriptors of the lateral and ventral blubber. Stratification resulted in a slight increase in monoenoic fatty acid (MUFA) content from the inner to the outer layers and a decreasing PUFA content. The 6 biopsies from living whales showed a similar FA composition and displayed FA profiles similar to those of the dorsal outer blubber blocks. Comparison of blubber FA structure with fin whales from the North Atlantic showed major differences, with a far lower percentage of 22:1 FA for the Mediterranean individuals and smaller differences in long chain MUFA between the inner and outer layer. Fin whales feed on the euphausiid Meganyctiphanes norvegica. Ligurian Sea M. norvegica appeared to have lower percentages of 20:1 and 22:1 FAs than their North Atlantic counterparts. Hence, the lower percentages of 20:1 and 22:1 FAs in the inner layer could reflect the structure of the prey assimilated. The slightly higher values in the outer layer could reflect the previous fall and winter feeding periods in Atlantic waters. The relative homogeneity of the blubber throughout the body suggested that sampling live animals to describe trophic interactions may be more realistic in the Mediterranean Sea than in the Atlantic

Lipid composition of stomach oil in a procellariiform seabird Puffinus tenuirostris: implications for food web studies

International audienceSome procellariiform seabirds use a dual strategy for provisioning their chicks by alternating between short and long foraging trips (LT). Trophic relationships of adult birds are unknown when they feed for themselves during LT because digestion processes preclude direct prey determination. Since stomach contents collected after LT contain oil of dietary origin, we tested the use of oil lipids as prey trophic markers using the Tasmanian short-tailed shearwater Puffinus tenuirostris as a model seabird. The intra-specific variability of stomach oils was investigated through lipid class composition, and their fatty acid and fatty alcohol profiles. Oils mainly consisted of wax esters (WE) and triacylglycerols (TAG) (49 to 86 and 7 to 41%, respectively). Major fatty acids of TAG were in a decreasing order 18:1n-9, 16:0, 16:1n-7, 14:0, 20:5n-3 and 22:6n-3. The WE-fatty acid profiles were dominated by 18:1n-9 and 16:1n-7 while fatty alcohol profiles were dominated by 16:0. Fatty alcohol and fatty acid patterns were tested as possible descriptors of ingested prey (derived from literature data) through multivariate discriminant analyses. Comparisons of the WE fatty alcohol patterns showed a close association with the alcohol structure of 3 myctophid fish species namely Krefftichthys anderssoni, Gymnoscopelus braueri and Electrona antarctica; these results were corroborated by WE fatty acid analysis. Comparison of TAG fatty acid patterns showed the highest similarity between oils and the digestive gland of the myctophid-eater squid Moroteuthis ingens in association with the myctophid Electrona carlsbergi. Hence, biochemical analysis of both WE and TAG strongly suggested that adult short-tailed shearwaters mainly prey upon Antarctic/sub- Antarctic myctophids when they feed for themselves, thus emphasizing the role of these oceanic mesopelagic fish in the marine ecosystem of the Southern Ocean

Lipid characterization of Pleuragramma antarcticum (Nothoteniidae) larvae off East Antarctica (139 degrees E-145.10 degrees E) during summer

International audiencePleuragramma antarcticum (Antarctic silverfish) larvae are a key component of the neritic assemblages in the Antarctic coastal waters and can be considered as an indicator of the future changes that may occur in this area. Lipid class and fatty acid composition was studied to assess the nutritional status and evaluate the type of dominant trophic interactions of P. antarcticum larvae collected between Terre Ad,lie and the Mertz Glacier Tongue (139A degrees E-145.10A degrees E) during summer 2007. P. antarcticum larvae exhibit moderate lipid levels (11.9-15.0% dry weight). Lipid class analyses showed a similar pattern over the study area consisting mainly of polar lipids (61-75% of total lipids). During their first summer, larvae started to accumulate small amount of lipid reserves in the form of triacylglycerols (10-16% of total lipids). Polar lipids were dominated by phosphatidylcholine (55-59%) followed by phosphatidylethanolamine (19-21%). Fatty acid signature of triacylglycerols indicates (1) a dominance of copepod of the Oithona type in the trophic pattern of P. antarcticum larvae and (2) a significant contribution of phytoplankton. In the same way, the analysis of gut content shows that 70% of larvae fed on various assemblages of phytoplankton and zooplankton (mainly copepods) and 30% of larvae fed exclusively on phytoplankton. Although a carnivorous diet is commonly described, our results suggest that P. antarcticum larvae showed an opportunistic feeding strategy (i.e. high degree of omnivory) and that dietary energy seems to be mainly directed towards fast growth rather than energy storage for periods of starvation

Lipid dynamics and trophic patterns in Pleuragramma antarctica life stages

The aim of this study was to clarify the trophic patterns of the key species Pleuragramma antarctica in the Dumont d'Urville Sea, through its development and possible changes according to sampling locations. Variability in diet composition of larvae, juvenile and adult P. antarctica was analysed using fatty acid markers. Analysis of lipid class in P. antarctica reflected lipid accumulation with increasing size at all sampling stations. The fatty acid composition of triacylglycerol highlighted ontogenetic changes in the diet. Phytoplankton markers, such as C16PUFA:C16 and EPA:DHA ratios >1, and carnivorous markers in larvae suggested an omnivorous diet. Comparison between the fatty acid signature of P. antarctica older stages (juveniles and adults) and zooplankton species using OPLS-discriminant analysis indicated that juveniles fed mainly on euphausiid larvae and to a minor extent on copepods, and confirmed that non-herbivorous copepods were the main prey for adults. Our results suggest that different feeding patterns and a generalist strategy in P. antarctica with juveniles feeding on bigger prey than adults, probably as a result of prey availability according to their vertical segregation pattern

Differential distribution of lipids in epidermis, gastrodermis and hosted Symbiodinium in the sea anemone Anemonia viridis

International audienceCnidarian-dinoflagellate symbiosis mainly relies on nutrient recycling, thus providing both partners with a competitive advantage in nutrient-poor waters. Essential processes related to lipid metabolism can be influenced by various factors, including hyperthermal stress. This can affect the lipid content and distribution in both partners, while contributing to symbiosis disruption and bleaching. In order to gain further insight into the role and distribution of lipids in the cnidarian metabolism, we investigated the lipid composition of the sea anemone Anemonia viridis and its photosynthetic dinoflagellate endosymbionts (Symbiodinium). We compared the lipid content and fatty acid profiles of the host cellular layers, non-symbiotic epidermal and symbiont-containing gastrodermal cells, and those of Symbiodinium, in a mass spectrometry-based assessment. Lipids were more concentrated in Symbiodinium cells, and the lipid class distribution was dominated by polar lipids in all tissues. The fatty acid distribution between host cell layers and Symbiodinium cells suggested potential lipid transfers between the partners. The lipid composition and distribution was modified during short-term hyperthermal stress, mainly in Symbiodinium cells and gastrodermis. Exposure to elevated temperature rapidly caused a decrease in polar lipid C18 unsaturated fatty acids and a strong and rapid decrease in the abundance of polar lipid fatty acids relative to sterols. These lipid indicators could therefore be used as sensitive biomarkers to assess the physiology of symbiotic cnidarians, especially the effect of thermal stress at the onset of cnidarian bleaching. Overall, the findings of this study provide some insight on key lipids that may regulate maintenance of the symbiotic interaction

Mesoscale distribution of zooplankton biomass in the northeast Atlantic Ocean determined with an Optical Plankton Counter: Relationships with environmental structures

We examined the mesoscale distribution of zooplankton populations using a continuous recording system: the optical plankton counter (OPC). Data were collected in the mid-latitude northeast Atlantic inter-gyre region in April and September 2001 during the POMME 2 and POMME 3 cruises. This sector of the North Atlantic system is characterized by subduction phenomena and mesoscale eddies. Estimated mean biomass was 2.88 DW g m(-2) in April and 1.64DW g m(-2) in September with populations dominated by small copepods of the genera, Clausocalanus, Paracalanus and Oithona. Day-night changes in vertical distribution appeared to be seasonally variable. During April, absolute concentrations within the upper layer above 50 m were higher at night. During September, vertical profiles of relative biomass were quite similar for day and night. Highest depth-integrated biomasses were located mainly on the periphery of anticyclonic eddies, with maxima related to the increase in depth range of vertical distribution. This pattern suggested that maximum biomass was associated with the most dynamic parts of the frontal features. Other zones of high zooplankton biomass were associated with the centers of cyclonic eddies and high fluorescence values. Using a 3D view, we found that zooplankton distribution showed a more complex pattern than in a 2D view with variable vertical distribution. Hence, proper description of the distribution of zooplankton underlines the need to describe this submesoscale with an order of magnitude around 10 nautical miles. (C) 2009 Elsevier Ltd. All rights reserved

Lipid dynamics in early life stages of the icefish <i>Chionodraco hamatus</i> in the Dumont d’Urville Sea (East Antarctica)

International audienceLipids play a crucial role in polar regions and are of particular importance in early life stages of Antarctic fish. This work presents the significance of lipids and fatty acids (FAs) in the early life stages of the icefish Chionodraco hamatus. Analysis of lipid classes (polar lipids, PL; cholesterol, Chol; and triacylglycerol, TAG) suggested different energy allocation strategies in preflexion (25 mm). Structural PL dominated lipid dynamics for preflexion larvae, indicating that small individuals allocate the majority of energy toward somatic growth. Conversely, postflexion larvae appear able to switch between growth (contribution of PL) and energy storage (contribution of TAG) strategies. The condition index ratio TAG/Chol varied from 0.2 to <2 with no differences between the two larval stages. Further, FA composition of the TAG and PL fractions suggests that both developmental stages share the same carnivorous diet and that C. hamatus relies on a few key prey items