Further studies of a spring phytoplankton bloom in an enclosed experimental ecosystem

A detailed characterization is presented of the spring diatom bloom which occurred in the enclosed experimental ecosystem bags at Loch Ewe, Scotland, during March–April 1983. The nutrient condition and bacterial biomass of the water column, phytoplankton species distribution, gross biochemical composition and detailed lipid composition (lipid class, fatty acid and free sterol) of the phytoplankton are reported throughout the bloom period. The results are compared with results from previous years. The conclusions are that major changes take place in the biochemical composition of a rapidly growing diatom population which affect both the gross composition and also the more detailed lipid composition. Such changes can take place over a matter of days and appear to be very dependent upon available growth conditions. Both carbohydrate and lipids levels increase towards the end of the bloom as nitrate and silicate levels are depleted in the water. Neutral lipids are shown to be important lipid components of the phytoplankton populations and long-chain ω3 polyunsaturated fatty acids are found to be only minor components of the structural polar lipids. The fatty acid and sterol data are discussed in relation to present knowledge concerning phytoplankton lipid composition.     

Fatty acids as trophic markers of phytoplankton blooms in the Bahía Blanca estuary (Buenos Aires, Argentina) and in Trinity Bay (Newfoundland, Canada)

The fatty acid compositions of phytoplankton and major primary consumers were analyzed during the development of seasonal algal blooms in the Bahía Blanca estuary, situated on the southern coast of the province of Buenos Aires (Argentina), and Trinity Bay, at Sunnyside, on the eastern coast of Newfoundland (Canada). Primary consumers in the Bahía Blanca estuary were zooplankton dominated by the calanoid copepod Acartia tonsa. At Sunnyside, the primary consumers were the sea scallop Placopecten magellanicus, an ecological and economical important benthic bivalve. The study shows that in spite of obvious differences between the two environments and the analytical approaches employed in each case, the analyses of fatty acid biomarkers can provide relevant ecological information. The fatty acid composition of the lipids of Bahía Blanca phytoplankton (high concentrations of the fatty acids 14:0, 16:4ω1, and 20:5ω3) reflected the presence of diatoms as a major component throughout the bloom. Fatty acid markers of the post-bloom phytoplankton in Bahía Blanca indicated a decline of phytoplankton biomass, and a relatively high input of detritus and terrestrial plant materials to the particulate organic matter of the estuary. Linoleic acid (18:2ω6), a typical “terrestrial” fatty acid, was conspicuous in the lipids of the post-bloom particulate matter of the Bahía Blanca estuary; 18:2ω2 was subsequently incorporated into zooplankton lipids diatom markers were also prominent in the lipids of pre-bloom and bloom phytoplankton at Sunnyside; post-bloom phytoplankton showed higher proportions of 18:0, 18:1ω9, and 18:4ω3, characteristic and often major fatty acids of dinoflagellates. The fatty acids of the digestive gland of P. magellanicus reflected the fatty acid composition of the phytoplankton, whereas those of the adductor muscle were practically unaffected by the composition of the food. This organ-specific response of an animal to the fatty acid composition of the diet is examined in terms of different applications of the fatty acid marker concept.     

Studies of a spring phytoplankton bloom in an enclosed experimental ecosystem. I. Biochemical changes in relation to the nutrient chemistry of water

A spring bloom of diatoms which occurred in large enclosed ecosystem bags at Loch Ewe, Scotland, during 1980, has been the subject of a chemical study. Changes observed in the general biochemical composition of the diatoms during the bloom are compared with the species distribution and changes in the nutrient chemistry of the bag water. The results indicate that major changes in cell biochemistry are associated with the growth, development, and decay of a diatom bloom, particularly if one or more nutrients become limiting.     

The role of transparent exopolymer particles (TEP) in the increase in apparent particle stickiness ({alpha}) during the decline of a diatom bloom

The termination of diatom spring blooms in temperate watershas been connected with the formation and subsequent rapid sedimentationof aggregates. According to coagulation theory, the rate ofaggregate formation depends on the probability of particle collisionand on the efficiency with which two particles adhere once theyhave collided (stickiness). During this study, the variationin particle stickiness was determined over the decline of adiatom bloom using the Couette Chamber assay with low shear(G = 0.86 s^–1). A mixed diatom population, dominated bySkeletonema costatum, was sampled during the spring bloom inthe Baltic Sea and incubated in the laboratory for 18 days.Measurements of diatom species composition, transparent exopolymerparticles (TEP) and bulk particle abundance, as well as chemicaland biological variables, were conducted in order to revealthe determinants of coagulation efficiency. The investigationshowed that an increase in TEP concentration relative to conventionalparticles at the decline of the bloom significantly enhancedapparent coagulation efficiencies. High proportions of TEP ledto apparent values of stickiness >1, which indicates thatcollision rates can be substantially underestimated when thestickiness parameter     

Annual microplankton cycles in Villefranche Bay, Ligurian Sea, NW Mediterranean

Abundance and composition of microplankton were studied overa period of 2 years at two depths in Villefranche Bay (LigurianSea, NW Mediterranean Sea). Diatoms dominated the microplanktonin late spring and autumn, whereas dinoflagellates composedthe major part of the microplankton in summer. The silicoflagellateDictyocha fibula and the diatom Thalassionema frauenfeldii dominatedin winter. Ciliates showed low variability throughout the yearwith the lowest abundance in February and an increase whichcoincided with the diatom maxima during autumn in both years.In 1998, the spring bloom (in May) was mainly composed of dinoflagellatesnear the surface and of diatoms in deeper layers. Subsurfacediatom maxima were observed in August–September and November.In 1999, diatoms peaked in May both at the surface and at thedepth of 50 m. They showed a strong maximum in October. Dinoflagellatesand tintinnids showed maxima in early November. Comparisonswith previous studies reveal that (i) changes in species compositionhave not been significant, (ii) the silicoflagellate’sabundance is lower during the present study, (iii) the sequentialspring bloom is composed of a pico-nanoplankton bloom in Marchand microphytoplankton in May, whereas in other western Mediterraneanareas the spring microphytoplankton bloom is reported in Februaryand March, (iv) high water transport through the Corsica channelcoinciding with low or negative winter values of North AtlanticOscillation (NAO) index are associated with the anomalous strongdevelopment of the spring diatom blooms in the Bay of Villefranche,whereas the usual trend is the lack of or weak development ofthe spring diatom bloom. This feature may determine the natureand the fate of primary production and the interannual variabilityin the relative importance of the microbial food web versusthe microbial loop.     

Changes in the Lipid Composition of Thalassiosira pseudonana during Its Life Cycle

The lipid and fatty acid (FA) compositions of a marine diatom alga Thalassiosira pseudonana grown in culture were investigated. The relative content of separate lipid classes and their FA composition varied during of the life cycle. During the periods of active cell division and resting cell production, the proportion of polar lipids, as the structural components of cell membranes, increased. Changes in the proportion of lipid classes resulted in shifts in the FA composition of total lipids. It is suggested that the structural components of photosynthetic and cells membranes accumulate in the resting cells. Thereby, a rapid cell growth and an extensive development of the species under favorable environmental conditions is provided.     

Fatty acids of plasma and red blood cell lipids in a normal population

A detailed study of the fatty acid composition of each of the lipids present in plasma and red blood cells of 62 healthy subjects of our area (Barcelona and surrounding counties), by coupling thin-layer and gas chromatography techniques has been made. The results are presented as normative data for comparison with those found in pathological situations. No significant sex differences were found. With increasing age, there was a tendency for the proportion of linoleic acid to decrease. Correlation analyses between the fatty acid composition of different lipids suggested that the interchange of fatty acids between plasma and cells mainly affects the phosphatidylcholine of the latter.     

New oxylipins produced at the end of a diatom bloom and their effects on copepod reproductive success and gene expression levels

Diatoms are dominant photosynthetic organisms in the world's oceans and are considered essential in the transfer of energy to higher trophic levels. However, these unicellular organisms produce secondary metabolites deriving from the oxidation of fatty acids, collectively termed oxylipins, with negative effects on predators, such as copepods, that feed on them (e.g. reduction in survival, egg production and hatching success) and, indirectly, on higher trophic levels. Here, a multidisciplinary study (oxylipin measurements, copepod fitness, gene expression analyses, chlorophyll distribution, phytoplankton composition, physico-chemical characteristics) was carried out at the end of the spring diatom bloom in April 2011 in the Northern Adriatic Sea (Mediterranean Sea) in order to deeply investigate copepod–diatom interactions, chemical communication and response pathways. The results show that the transect with the lowest phytoplankton abundance had the lowest copepod egg production and hatching success, but the highest oxylipin concentrations. In addition, copepods in both the analyzed transects showed increased expression levels of key stress-related genes (e.g. heat-shock proteins, catalase, glutathione S-transferase, aldehyde dehydrogenase) compared to control laboratory conditions where copepods were fed with the dinoflagellate Prorocentrum minimum which does not produce any oxylipins. New oxylipins that have never been reported before for microalgae are described for the first time, giving new insights into the complex nature of plant–animal signaling and communication pathways at sea. This is also the first study providing insights on the copepod response during a diatom bloom at the molecular level.     

Seasonal variation in the biochemical composition of particulate material collected by sediment traps at Signy Island, Antarctica

Particulate material recovered over an 18-month period from sediment traps deployed at a shallow-water nearshore Antarctic site was analysed for photosynthetic pigments, aliphatic hydrocarbons and fatty acids. All components showed a distinct seasonal variation, with high recovery rates during the summer open-water phytoplankton bloom and low rates under winter fast ice. The amount of trapped material differed between the two summers, indicating inter-annual variability of vertical flux associated with differences in the intensity of the summer phytoplankton bloom. Particulate material trapped in summer was dominated by that which originated in diatoms. High recoveries of chlorophyll a, fucoxanthin, n-C_21:6 hydrocarbon, 20:5(n-3) fatty acid and shorter chain (C₁₅–C₂₄) aliphatic hydrocarbons all pointed to a significant summer flux of ungrazed diatoms. There were, however, also signals of zooplankton grazing activity (notably pyrophaeophorbide a), and the presence of C18:4(n-3) and C22:6(n-3) fatty acids suggested a small flux of material from flagellates and other sources. Longer chain n-alkanes (C₂₅–C₃₄) indicative of nanoplankton were detected all year, but there was no significant deposition of zooplankton material in any sample. The major recovery rate of photosynthetic pigments was in late summer (February to April), and the major grazing signal occurred after the peak of the summer diatom bloom. Most of the diatom bloom appeared to settle out from the water column without being grazed. The major seasonal contrast in the biochemistry of the trapped material was the dominance of the diatom signature in summer, and in winter the predominance (but at much lower recovery rates) of material from nanoplankton. Received: 2 March 1998 / Accepted: 12 June 1998     

Effect of lipid saturation on the topology and oligomeric state of helical membrane polypeptides

Natural liquid crystalline membranes are made up of many different lipids carrying a mixture of saturated and unsaturated fatty acyl chains. Whereas in the past considerable attention has been paid to cholesterol content, the phospholipid head groups and the membrane surface charge the detailed fatty acyl composition was often considered less important. However, recent investigations indicate that the detailed fatty acyl chain composition has pronounced effects on the oligomerization of the transmembrane helical anchoring domains of the MHC II receptor or the membrane alignment of the cationic antimicrobial peptide PGLa. In contrast the antimicrobial peptides magainin 2 and alamethicin are less susceptible to lipid saturation. Using histidine-rich LAH4 designer peptides the high energetic contributions of lipid saturation in stabilizing transmembrane helical alignments are quantitatively evaluated. These observations can have important implications for the biological regulation of membrane proteins and should be taken into considerations during biophysical or structural experiments.     

Triacylglycerol accumulation of Phaeodactylum tricornutum with different supply of inorganic carbon

The diatom Phaeodactylum tricornutum produces large quantities of lipids, especially triacylglycerols (TAGs) under nitrogen or phosphorus limitation. In this study, production of lipids and TAGs during this process was compared under conditions with different inputs of inorganic carbon. With an abundant supply of inorganic carbon, considerable accumulation of biomass, lipids, and TAGs was identified after a nitrogen/phosphorus-limiting “induction incubation.” TAGs were still synthesized and accumulated even under inorganic carbon limitation with a cessation in the production of biomass and cellular lipids. This part of accumulated TAGs could be synthesized through recycling and transformation of other lipids such as glycolipids and phospholipids. Additionally, some alterations in the fatty acid profile following TAG accumulation were found. The content of the C16:0 fatty acid increased with decreases in C16:3 and C20:5, which could have been caused by enzymatic selectivity for these fatty acids during the process of TAG synthesis. It was concluded that nitrogen and phosphorus metabolism regulates the synthesis of TAG, while carbon metabolism promotes it by providing sufficient substrates.     

Seasonal dynamics of fatty acid composition in female northern pike (Esox lucius L.)

Seasonal changes in the fatty acid composition of neutral and polar lipids were measured in the ovary, liver, white muscle, and adipopancreatic tissue of northern pike. The role of environmental and physiological factors underlying these changes was evaluated. From late summer (August–September) to winter (January–March), the weight percentage of n-3 polyunsaturated fatty acids (especially 22:6n3) declined significantly in the neutral lipids of all somatic tissues examined. However, large quantities of n-3 polyunsaturated fatty acids accumulated in the recrude cing ovaries during fall and the weight percentage of n-3 polyunsaturated fatty acids in ovary polar lipids also increased significantly. Additionally, the n-3 polyunsaturated fatty acid content of somatic polar lipids increased significantly during fall due to increases in the total polar lipid content of the somatic tissues. This suggests that during fall n-3 polyunsaturated fatty acid are diverted away from somatic neutral lipids and thereby conserved for use in ovary construction and for incorporation into tissue polar lipids. The percentage of n-3 polyunsaturated fatty acid in ovary neutral lipids also declined during fall and early winter, perhaps as an adaptation to conserve these fatty acids for storage in oocyte polar lipids and later incorporation into cellular membranes of the developing embryo. Reductions in the n-3 polyunsaturated fatty acids content of somatic and ovarian neutral lipids during fall were compensated for specifically by increases in the percentage of monounsaturated fatty acids rather than saturated fatty acids. This suggests that the ratio of saturated to unsaturated fatty acids in pike neutral lipid, is regulated physiologically, and hence may influence the physiological functioning of these lipids. During fall and early winter the percentage of saturated fatty acids declined significantly in the polar lipids of all tissues examined. This change was consistent with the known effects of cold acclimation on the fatty acid composition of cellular membranes. As the ovaries were recrudescing from September to January, liver polar lipids exhibited significant decreases in the percentage of total polyunsaturated fatty acids and n-3 polyunsaturated fatty acids and increases in monounsaturated fatty acids, and acquired a fatty acid composition very similar to that of ovary polar lipids. Therefore, seasonal changes in the percentage of polyunsaturated and monounsaturated fatty acids in liver polar lipids probably reflect the liver's role in vitellogenesis rather than the effects of temperature on membrane fatty acid composition. At all times of year, the fatty acid compositions of white muscle and adipopancreatic tissue neutral lipids were very similar, which may indicate a close metabolic relationship between these lipid compartments.Abbreviations AP adipopancreatic - BHT butylated hydroxytoluene - CI confidence interval - EFA essential fatty acids - MUFA monounsaturated fatty acids - NL neutral lipids - PL polar lipids - PUFA polyunsaturated fatty acids - SFA saturated fatty acids     

Labelling patterns of carbon-14 in net plankton during a winter-spring bloom

Weekly surface samples were collected in lower Narragansett Bay, Rhode Island, during the 1975 winter-spring bloom and fractionated by nets to nannoplankton (<20 μm) and total (< 158 μm) size fractions. Each size fraction was assayed for paniculate carbon, nitrogen, carbohydrate, protein, chlorophyll a, and cell counts. The <20 μm values were subtracted from the <158 μm values to estimate the composition of the 20 μm to 158 μm fraction (termed net plankton). As nutrients (primarily nitrogen) decreased to undetectable levels with the culmination of the diatom bloom, the ratios of protein/carbohydrate, carbohydrate/carbon, and carbon/chlorophyll a in the net plankton indicated the diatom population was increasingly nutrient-limited. Each size fraction was also incubated at a saturating light intensity with carbon-14; following filtration, the cells were extracted with solvents to obtain labelled polysaccharide and protein. The daily rates of polysaccharide and protein synthesis in the net plankton declined as the bloom entered the stationary phase. When the diatom population was at its maximum density the majority of the carbon-14 was found in the ethanol-soluble fraction; this may be due to high light intensities or nutrient effects.     

Fatty acid composition of wild Odontesthes bonariensis (Valenciennes 1835) larvae: implications on lipid metabolism and trophic relationships

The fatty acid composition of the pejerrey Odontesthes bonariensis larvae was studied to elucidate potential dietary relationships. Their principal fatty acids were characteristic for membrane lipids of aquatic organisms. The fatty acid composition varied little throughout seasons, with high proportions of 22 : 6(n‐3) (27% of total fatty acids), which is biosynthesized de novo from dietary precursor fatty acids and/or accumulated from the diet. Other major fatty acids were 16 : 0 and 18 : 0. The diatom‐typical 16 : 1(n‐7) and other dietary fatty acids (zooplankton and microplankton) are not reflected in the larvae, thus limiting the use of fatty acids as trophic markers for food web relationships of atherinopsids.     

Lipid fatty acid composition of fungi in the genus Aspergillus grown on media with various sources of nitrogen

The fatty acid composition of lipids synthesized by fungi belonging to the Aspergillus genus was studied during their growth on media containing different organic and inorganic nitrogen sources. On the average, the cultures were shown to accumulate from 7 to 30 g/L of biomass and to synthesize from 3 to 13% of lipids. The lipids were found to contain saturated and unsaturated fatty acids with the number of carbon atoms from 14 to 18. The fungi had a typical fatty acid composition of lipids which did not depend on the composition of the growth medium.     

Lipid Profile Remodeling in Response to Nitrogen Deprivation in the Microalgae Chlorella sp. (Trebouxiophyceae) and Nannochloropsis sp. (Eustigmatophyceae)

Many species of microalgae produce greatly enhanced amounts of triacylglycerides (TAGs), the key product for biodiesel production, in response to specific environmental stresses. Improvement of TAG production by microalgae through optimization of growth regimes is of great interest. This relies on understanding microalgal lipid metabolism in relation to stress response in particular the deprivation of nutrients that can induce enhanced TAG synthesis. In this study, a detailed investigation of changes in lipid composition in Chlorella sp. and Nannochloropsis sp. in response to nitrogen deprivation (N-deprivation) was performed to provide novel mechanistic insights into the lipidome during stress. As expected, an increase in TAGs and an overall decrease in polar lipids were observed. However, while most membrane lipid classes (phosphoglycerolipids and glycolipids) were found to decrease, the non-nitrogen containing phosphatidylglycerol levels increased considerably in both algae from initially low levels. Of particular significance, it was observed that the acyl composition of TAGs in Nannochloropsis sp. remain relatively constant, whereas Chlorella sp. showed greater variability following N-deprivation. In both algae the overall fatty acid profiles of the polar lipid classes were largely unaffected by N-deprivation, suggesting a specific FA profile for each compartment is maintained to enable continued function despite considerable reductions in the amount of these lipids. The changes observed in the overall fatty acid profile were due primarily to the decrease in proportion of polar lipids to TAGs. This study provides the most detailed lipidomic information on two different microalgae with utility in biodiesel production and nutraceutical industries and proposes the mechanisms for this rearrangement. This research also highlights the usefulness of the latest MS-based approaches for microalgae lipid research.     

Isolation by Time During an Arctic Phytoplankton Spring Bloom

The arctic phytoplankton spring bloom, which is often diatom‐dominated, is a key event that provides the high latitude communities with a fundamental flux of organic carbon. During a bloom, phytoplankton may increase its biomass by orders of magnitude within days. Yet, very little is known about phytoplankton bloom dynamics, including for example how blooming affects genetic composition and diversity of a population. Here, we quantified the genetic composition and temporal changes of the diatom Fragilariopsis cylindrus, which is one of the most important primary producers in the Arctic, during the spring bloom in western Greenland, using 13 novel microsatellite markers developed for this study. We found that genetic differentiation (quantified using sample‐specific F_ST) decreased between time points as the bloom progressed, with the most drastic changes in F_ST occurring at the start of the bloom; thus the genetic structure of the bloom is characterized by isolation by time. There was little temporal variation in genetic diversity throughout the bloom (mean H_E = 0.57), despite marked fluctuations in F. cylindrus cell concentrations and the temporal change in sample‐specific F_ST. On the basis of this novel pattern of genetic differentiation, we suggest that blooming behavior may promote genetic diversity of a phytoplankton population.     

The fatty acids of Trypanosoma vivax

A study was carried out to determine the lipid composition of the blood-stream form of the African trypanosome. Trypanosoma vivax. Data from thin layer chromatography showed that the major polar lipids were lysophosphatidylcholine, sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and diphosphatidylglycerol. The major neutral lipids were sterol, monoacylglycerol, diacylglycerol, free fatty acid and triacyglycerol. 16:0, 18:0, 18:1 and 18:2 constituted the major fatty acids of both the polar and neutral lipid fractions. The work constituted the first detailed study on the fatty acid composition of this African trypanosome.     

Mechanisms of the initiation of lipid peroxidation in the synaptosomes of marine teleosts

The initial rates of NAD- and NADPH-dependent enzymic and Fe+-ascorbic acid-dependent nonenzymic lipid peroxidation have been measured in synaptosomes from the brain of 4 teleost species. The rates of peroxidation were compared with lipid composition and fatty acid composition of total lipids in order to reveal factors accounting for the intensity of peroxidation in the excitable membranes from the brain of ectotherms. The data obtained indicate that the rates of enzymic lipid peroxidation do not correlate with lipid and fatty acid compositions, depending on the efficiency of production of oxygen in the active form by pyridine nucleotide-dependent enzymic systems. Activation of lipid peroxidation during adaptation of animals to the environment may be considered as one of the mechanisms which account for compensatory changes in fatty acid composition of the membrane lipids.     

Characteristics of fatty acid composition of lipids in higher plant vacuolar membranes

The fatty acid composition of vacuolar membrane lipids from plant storage tissues and their genesis have been studied. A high content of unsaturated fatty acids (up to 77%) was observed in lipids of these membranes. Linoleic acid prevailed in vacuolar lipids of carrot and red beet (54.2 and 44.2%, respectively). Linolenic acid prevailed in vacuolar lipids of garden radish and turnip (39.7 and 33.9%, respectively). Regarding saturated fatty acids, vacuolar lipids of garden radish, carrot, and red beet contained predominantly palmitic acid (up to 20-24%). Unsaturated fatty acids, petroselinic (C18: 1omega12), cis-vaccenic (C18: 1omega7), hexatrien-7,-10,-13-oic (C16:3omega3) and others, were observed in vacuolar lipids of roots. These acids are usually synthesized in chloroplasts, and their presence in vacuolar lipids can be associated either with the transport of metabolites to the vacuole, or with endocytosis during vacuolar formation in the plant cell. The specific features of fatty acid composition of tonoplast lipids apparently are closely related to the tonoplast unique fluidity and mobility required for running osmotic processes in the cell and for forming transport protein assemblies.