Studies of a spring phytoplankton bloom in an enclosed experimental ecosystem. II. Changes in the component fatty acids and sterols

The spring diatom bloom in Loch Ewe (N.W. Scotland) during 1980 has already been the subject of a detailed study. As an extension of this work the component fatty acids and sterols of the diatom lipids have been analysed throughout the bloom period. The results confirm that detailed changes occur in the lipid composition of diatoms during their normal growth. In addition, the data are discussed in relation to published analyses of diatom lipids and suggestions made as to reasons for the considerable variation in reported fatty acid composition.     

The endemic faunae of Lake Baikal: their general biochemistry and detailed lipid composition

The biochemical composition of the important endemic faunal groups in Lake Baikal, Siberia, have been examined. The major biochemical components were determined and detailed analyses of the lipid fractions are presented. The lipids are characterized by high levels of long-chain omega 3 polyunsaturated fatty acids in the glyceride-esters, the presence of large amounts of triglyceride in pelagic and bathy-pelagic species with a complete absence of wax esters, and a very simple sterol composition dominated almost exclusively by cholesterol. The results are discussed in relation to present knowledge concerning both marine and freshwater lipids and the possible origin and evolution of the Baikalian fauna. Present theories concerning the likely role of long-chain polyunsaturates and wax esters in lipids are considered in the light of these present results and a link is suggested between sterol diversity and type of evolution.     

Fatty acid composition of phospholipids from rabbit and crayfish skeletal muscle sarcolemma and sarcoplasmic reticulum membranes]

A comparative analysis of fatty acid composition of lipid components from skeletal muscle sarcolemma and sarcoplasmic reticulum membranes of rabbits and crayfishes Astacus fluviatilis and A. leptodactylus has been made by means of gas-liquid chromatography of methyl esters of fatty acids. There are slight differences between external and internal membranes in fatty acids composition of lipids in the same animal. Considerable differences were found, however, when lipids in corresponding membranes of different species were compared. There are more unsaturated fatty acids in the crayfish than in the rabbit membranes. The most expressive differences in fatty acid composition between the two animals concern the content of linoleic acid type. Polyunsaturated acids in the crayfish are mostly of a 3 type and those in the rabbit of a 6 type. During biochemical evolution the following changes seem to take place, a decrease in the amount of unsaturated fatty acids as well as of polyunsaturated ones of a 3 type and an increase of those of the 6 type. These changes very probably reflect the transition from an aquatic to a terrestrial habitat.     

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.     

Comparison of sterol and fatty acid profiles of chytrids and their hosts reveals trophic upgrading of nutritionally inadequate phytoplankton by fungal parasites

Chytrids are ubiquitous fungal parasites in aquatic ecosystems, infecting representatives of all major phytoplankton groups. They repack carbon from inedible phytoplankton hosts into easily ingested chytrid propagules (zoospores), rendering this carbon accessible to zooplankton. Grazing on zoospores may circumvent bottlenecks in carbon transfer imposed by the dominance of inedible or poorly nutritious phytoplankton (mycoloop). We explored qualitative aspects of the mycoloop by analysing lipid profiles (fatty acids, sterols) of two chytrids infecting two major bloom-forming phytoplankton taxa of contrasting nutritional value: the diatom Asterionella formosa and the filamentous cyanobacterium Planktothrix agardhii. The polyunsaturated fatty acid composition of chytrids largely reflected that of their hosts, highlighting their role as conveyors of otherwise inaccessible essential lipids to higher trophic levels. We also showed that chytrids are capable of synthesizing sterols, thus providing a source of these essential nutrients for grazers even when sterols are absent in their phytoplankton hosts. Our findings reveal novel qualitative facets of the mycoloop, showing that parasitic chytrids, in addition to making carbon and essential lipids available from inedible sources, also upgrade their host's biochemical composition by producing sterols de novo, thereby enhancing carbon and energy fluxes in aquatic food webs.     

Lipid content in 19 brackish and marine microalgae: influence of growth phase, salinity and temperature

Algal lipids provide essential fatty acids for higher trophic levels in the marine food web, and understanding the fatty acid composition in phytoplankton is critical for evaluating its value as a diet. Nineteen microalgal species, mainly originating from the Baltic Sea, covering major algal classes were grown in different growth conditions. Samples were taken during both the exponential and stationary growth phases and analysed regarding their fatty acid methyl esters and free fatty acids. Our results show that across all screened species, total fatty acids increased significantly from exponential to stationary growth phase. Furthermore, it was observed that warm-water species contained more lipids and differed in their lipid profile as compared with the cold-water species. Brackish water species also showed a slightly higher lipid content than the marine species, but their lipid profile was not significantly different. Plotting changes in lipids against changes in cell nitrogen revealed a significant dependency between decrease in cell nitrogen and increase in lipids across all tested species.     

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.     

Docosahexaenoic Acid Production and Lipid-Body Formation in Schizochytrium limacinum SR21

Schizochytrium limacinum SR21, a thraustochytrid (Labyrinturomycota), is a heterotrophic marine microorganism. SR21 has attracted recent attention because of the production of docosahexaenoic acid (DHA). We obtained highly concentrated SR21 zoospores and successfully observed synchronous growth. We investigated changes of lipid content and fatty acid composition during the growth. The morphological features of the lipid bodies were also described via fluorescent and electron microscopy. The cells developed quickly after zoospore settlement. Lipid bodies developed in accordance with an increase in lipid content during the 8-h synchronous growth. The total lipid was composed mainly of triacylglycerol, sterol esters, and phosphatidylcholine. The proportion of neutral lipids (triacylglycerol and sterol esters) in the total lipid was fairly constant during growth. The fatty acid composition of neutral lipids, primary components of the lipid body, and phospholipids, primary components of the cell membranes, was nearly unchanged during the synchronous growth. However, the DHA content of the phospholipids decreased drastically after a 10-day culture. Electron micrographs prepared using a high-pressure freeze substitution technique revealed a fine structure of light- and dark-staining bands inside the lipid bodies in many stages of the cells.     

Lipids and sterols in Musca domestica L. (Diptera, Muscidae): changes after treatment with sucrose and lead

Total lipid, fatty acid and sterol composition of larvae and adults of Musca domestica was investigated before and after feeding on sucrose syrup or on the same syrup containing 1% lead nitrate. The effects of sucrose and of lead ions were found to be different. In larvae sucrose diet inhibited the fatty acid elongation and stimulated the first stages of their unsaturation. A significant increase of phytosterol concentrations was obtained. These changes increased the cell membrane permeability. The addition of lead caused a decrease of the fatty acid unsaturation, which decreased the cell membrane permeability. In adults the sucrose diet had no effect on the lipid and sterol composition, while the addition of lead decreased the cholesterol concentration. The composition of lipids and sterols also depends on the diet of larvae before pupation. The data obtained suggested that changes in lipid and sterol composition, which control the permeability of the cell membrane, might be an adaptive response of the organism to the changes of the environment.     

The lipid composition of the non-photosynthetic diatom Nitzschia alba

The lipid composition of the non-photosynthetic marine diatom, Nitzschia alba, has been quantitatively determined. Triglycerides accounted for 20% of the cell dry weight and 87% of the total lipids. Smaller amounts of 1,2- and 1,3-diglycerides, free sterol (24-methylene cholesterol), hydrocarbons and an unknown component were the remaining neutral lipids detected. Phosphatidylsulfocholine (phosphatidyl S,S-dimethylmercaptoethanol), present in amounts of 0.8% of cell dry weight (35% of total polar lipids), was the major polar lipid component. Other phospholipids were lysophosphatidylsulfocholine, phosphatidylglycerol, phosphatidylinositol and cardiolipin, but both phosphatidylcholine and phosphatidylethanolamine were completely absent. Another novel sulfolipid, deoxyceramide sulfonic acid, as well as the sulfate ester of the free sterol, were also present. Considerable amounts of the four lipids often associated with photosynthetic organisms, mono- and di-galactosyl diglycerides, sulfoquinovosyl diglyceride and phosphatidylglycerol, were identified in N. alba. However, the fatty acid components of the glycosyl diglycerides did not show the high amounts of polyunsaturated acids (18 : 2, 18 : 3) normally found in photosynthesizing organisms. All polar lipids were found to be associated with various cell membrane fractions in N. alba.     

Lipid dynamics and feeding of dominant Antarctic calanoid copepods in the eastern Weddell Sea in December

Lipid content, fatty acid composition, and feeding activity of the dominant Antarctic copepods, Calanoides acutus, Calanus propinquus, and Metridia gerlachei, were studied at a quasi-permanent station in the eastern Weddell Sea in December 2003. During 3 weeks of the spring phytoplankton development, total lipid levels of females and copepodite stages V (CVs) of C. acutus were almost doubled. Meanwhile, only a slight increase in total lipid content occurred in M. gerlachei, and no clear trend was observed in lipids of C. propinquus females. The pronounced increase of lipids in C. acutus was due to an accumulation of wax esters. The proportion of wax esters in the lipids of M. gerlachei was clearly lower, while triacylglycerols played a more important role. In C. propinquus, triacylglycerols were the only neutral lipid class. There were no pronounced changes in the feeding activity of M. gerlachei, whereas the feeding activity of C. acutus had rapidly increased with the development of the phytoplankton bloom in December, which explains its rapid lipid accumulation. The combination of gut content and fatty acid trophic marker analyses showed that C. acutus was feeding predominantly on diatoms. The typical diatom fatty acid marker, 16:1(n-7), slightly decreased and the tracer for flagellates, 18:4(n-3), increased in females and CVs of C. acutus. This shift indicates the time, when the significance of flagellates started to increase. The three copepod species exhibited different patterns of lipid accumulation in relation to their trophic niches and different duration of their active phases. The investigations filled a crucial data gap in the seasonal lipid dynamics of dominant calanoid copepods in the Weddell Sea in December and support earlier hypotheses on their energetic adaptations and life cycle strategies.     

The lipids of phosphorescent Vibrio albensis bacteria]

The lipid composition of fluorescent vibrios, V. eltor and nonagglutinating vibrios has been studied. In the fraction of polar lipids phosphatidylethanolamine, phosphatidylinositol and cardiolipin and in the fraction of neutral lipids monoglycerides, free fatty acids, diglycerides, triglycerides, sterol esters have been identified. The fatty acid composition of some classes of neutral lipids have been determined. Both similarity and differences between the strains under study in their lipid and fatty acid composition have been established.     

Effect of cobalt ions on lipid and sterol metabolism in the marine invertebrates Mytilus galloprovincialis and Actinia equina

The lipid and sterol fractions of the mussel Mytilus galloprovincialis and the anemone Actinia equina were analyzed before and after incubation with cobalt ions. There were significant changes in the lipid and sterol composition, strongly depending on the cobalt ions concentrations. The changes in the lipid composition of both invertebrates were different for neutral lipids and phospholipids. These changes concern the length of the fatty acid chains as well as their unsaturation. The cobalt ions inhibited the oxidation of sterols and their alkylation at C-24. Because of these results we can assume that some of the changes caused by cobalt ions might possess adaptive value.     

Spatial patterns of seston concentration and biochemical composition between nearshore and offshore waters of a Great Lake

1. The concentration and composition of seston were measured in the east basin of Lake Erie (U.S.A.–Canada) to determine whether the classical patterns of nearshore versus offshore zonation considered typical of large lakes have been altered by decades of change in nutrient loading and food web structure, and to test the possibility that food quality for seston consumers, as reflected in nutrient and lipid composition, may currently be diminished. Chlorophyll‐a (chl‐a), particulate organic carbon (POC), particulate P, total lipid (TL), lipid classes, fatty acids and major phytoplankton groups were compared between the nearshore (<20 m) and offshore zones in spring and early summer. 2. Particulate organic carbon, chl‐a and TL concentrations were lower nearshore than offshore, which is a reversal of the classical large lake pattern but consistent with other evidence from the Great Lakes that colonization by filter‐feeding dreissenid mussels can cause seston depletion in relatively shallow waters. 3. Terrestrial and bacterial fatty acid markers were slightly higher in the nearshore than the offshore, but there was little difference in nutrient, taxonomic or biochemical composition between zones otherwise. This shows a small differential influence of terrestrial and detrital inputs, and a slight shift away from phytoplankton dominance of seston composition in the nearshore, but little difference in potential food quality of seston. 4. Microscope counts, phytoplankton fluorescence, and fatty acid composition indicated succession from diatom dominance in May to dominance by cryptophyte and chromophyte flagellates in June and July. Depletion of dissolved P and Si, increased contribution of storage lipids, and changes in fatty acid composition suggested a mild degree of nutrient deficiency during this spring to summer transition. 5. Total lipids were dominated by classes typical of pigments and membranes with only moderate amounts of neutral (storage) lipids, polyunsaturated fatty acids (PUFA) were abundant (especially the long chain ω‐3 acids) and the POC : chl‐a and POC : particulate P ratios indicated P sufficiency or slight P‐deficiency. Despite concerns that some important consumers in the Great Lakes food web may be suffering from diminished food quality, these results point to a generally high seston food quality even with highly abundant mussels and incipient P deficiency in the east basin of Lake Erie.     

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 acid and phytoplankton compositions of different types of mucilaginous aggregates in thenorthern Adriatic

The biomarkers (fatty acid proportions and ratios characteristicof phytoplankton and bacteria) and phytoplankton species insmall (0.5–2.0 cm) and large (0.5–5 m) marine aggregateswere determined in samples collected in the northern AdriaticSea, during a mucilage event in 1997, as well as in 1993, 1994and 1998, when events were not observed. Types of aggregateswere identified according to various biomarker relationships,particularly those related to bacterial and phytoplankton activitiesand changes in the diatom species composition. Aged mucilaginousaggregates (in summer 1997) showed fatty acid proportions (16P/18P,3.9–7.7) characteristic of the highest phytoplankton activities,and also showed the highest bacterial fatty acid proportions(13.3–17.1%) and ratios (C15:br/C15:0, 4.4–6.0).They showed an different diatom community (dominated by Cylindrothecaclosterium) from that in surrounding waters. These characteristicssuggest a continuous renewal of the aggregate organic matter,supporting the hypothesis that aggregate is a ‘selfsustaining’community. In contrast, both freshly formed marine snow, dominantduring periods without mucilage events, and freshly formed mucilaginousaggregates presented biomarker proportions and ratios similarto those of suspended matter (bacterial fatty acids 3–6.7%,C15:br/C15:0 1.2–4.6, 16P/180.4–4.0), and diatomcomposition similar to that of the ambient water. This indicatesthat marine snow sinks more rapidly than large aggregates, beforesignificant changes can occur in its plankton composition. Otheraging aggregate types showed intermediate characteristics, suggestingthat their residence times in the water column were still sufficientto develop organic production–decomposition cycles thatmodified to various extents their biochemical composition.     

Seasonal changes in particulate and dissolved lipids in a eutrophic prairie lake

1. Critical periods of lipid energy transfer from phyto- to zooplankton were inferred by comparing seasonal patterns of particulate and dissolved lipid fractions in lake water with temporal changes in lipid energy reserves of the zooplankton in a hypereutrophic lake.
2. The midsummer phytoplankton community was dominated by the bloom-forming cyanobacterium Aphanizomenon flos-aquae. The collapse of the bloom was accompanied by a 2-week period of severe nitrogen deficiency after which there was a marked increase in the concentration of lipid energy reserves in the particulate (algal) fraction.
3. Areal lipid energy reserves of the dominant herbivorous zooplankton responded positively to changes in the tri-and diacylglycerol content of the particulate fraction of lake water in a species-specific manner.
4. Bacterial numbers also peaked in September concomitant with a large increase in free fatty acids in the dissolved lipid fraction probably produced by the decay of the
A. flos-aquae bloom.
5. The association between periods of nitrogen deficiency and increased energy reserve lipids in the particulate fraction supports observations made with laboratory algal cultures that periods of nutrient deficiency may intensify lipid synthesis in some algal species, thereby enhancing the rate of lipid energy transfer from phytoplankton to zooplankton.     

Fatty acid composition of particulate matter and photosynthetic products in subarctic and subtropical Pacific

The fatty acid composition of lipid materials in particulate matter and photosynthetic products was determined using ¹³C gas chromatography-mass spectrometry methodology in the subarctic and subtropical Pacific. Polyunsaturated fatty acids (PUFA) were measured as one of the major constituents of particulate and photosynthetically produced lipids in the subarctic Pacific. In the subtropical Pacific, on the other hand, a quite simple fatty acid composition was found, consisting mainly of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA); the production rate of PUFA could not be determined due to the low concentration in the subtropical area. The relationship between the fatty acid composition of particulate lipids and photosynthetically produced lipids indicated that PUFA observed in particulate lipids were mainly associated with phytoplankton. Non-living lipids, on the other hand, could be mainly constituted by SFA, due to the lability of PUFA to degradation. The difference in the contribution of phytoplankton lipids to particulate lipids is considered as an important factor affecting the difference in the fatty acid composition of particulate lipids between subarctic and subtropical Pacific.      

Palaeolimnological evidence for the independent evolution of neighbouring terminal lakes,the Murray Darling Basin,Australia

Phytoplankton composition and production are highly unpredictable within an estuary, due to the high variability of forcing factors, such as freshwater flow, salinity, nutrients and light. The Guadiana estuary has shown sharp inter-annual differences in freshwater flow, related to variable precipitation, which is expected to affect nutrient loadings, light availability and phytoplankton succession. Water retention due to dam construction will further enhance changes in river flow and ecosystem dynamics. The main goal of the present study was to describe and relate phytoplankton succession and environmental conditions, namely nutrients and light, in the Guadiana upper estuary (south-western Iberian Peninsula), a dam regulated temperate estuary. From March 2004 to October 2005, water samples were collected in three stations along a longitudinal transect covering the upper estuary. Several water variables were determined and phytoplankton composition was studied through inverted and epifluorescence microscopy. A typical freshwater phytoplankton succession was observed, from a diatom spring bloom to cyanobacteria dominance in the summer, and a second diatom bloom in the autumn. Neither nutrients nor light availability seemed to be related to the observed succession, especially the seasonal variation of diatom abundance. During summer, nutrient concentrations (especially Si) were high and non-limiting, whilst light was available in the mixing layer. However, diatoms were present in low numbers. Grazing pressure was probably responsible for the regulation of diatom seasonal succession in the Guadiana upper estuary, which should be addressed in future studies. Handling editor: K. Martens     

Analysis of lipids by gas-liquid chromatography and complementary methods in four strains of Aedes aegypti mosquitoes

Fatty acid composition of total lipids, neutral lipids and phospholipids of strains of Aedes aegypti were determined. The fatty acid composition of the strains differed quantitatively with regard to the relative percentage of commonly occurring fatty acids. Gas-liquid chromatography of fatty acid methyl esters showed 18:1 (oleic or elaidic) to be the predominant fatty acid. The fatty acid was identified as oleic by argentation thin-layer chromatography. A modified colorimetric method was used to determine tissue-free fatty acids. The lipids were predominantly triacylglycerol with lesser amounts of free fatty acids and decreasing amount of sterol ester, sterol, monoacylglycerol, diacylglycerol and hydrocarbons. The data show considerable lipid differences between the Caribbean strains (Les Cayes, Haiti, and San Juan, Puerto Rico) and the Jakarta (Indonesia) strain. The Shimba Hills (Kenya) strain was more similar to Jakarta than to the Caribbean strains. The results obtained with the different strains are discussed in relation to the established oral susceptibility to Dengue 1 and Dengue 2, yellow fever, and genetic analysis by isoenzyme studies.