Fatty Acid Composition of Algae from Habitats with Varying Amounts of Illumination

The fatty acid (FA) composition of algae Ulva fenestrata (Chlorophyta), Costaria costata (Phaeophyta), and Grateloupia turuturu (Rhodophyta) differed in their illumination habitats (shaded grotto and bright light). It was found that the light intensity affect the lipid content and fatty acid (FA) ratios in the algae. In the shaded places, the content of polyunsaturated FAs of the (n-3) series in U. fenestrate and of the (n-3) and (n-6) series, except 18 : 2, in C. costata are higher than at bright light, whereas in G. turuturu, the content of 20 : 5n-3 acids in that instance was lower. The lipid content was 2.5–3.6 times higher in the algae at low light intensity. The content variation of algal lipid components apparently was related to adaptive response of these plants to illumination condition.     

Fatty acid profiles of algae mark the development and composition of harpacticoid copepods

1. The value of algal fatty acids (FA) as diet biomarkers for benthic harpacticoid copepods was investigated. A high proportion of 18:1ω9 and 18:2ω6 FA was observed in the lipid reserve fraction of copepods fed with cyanobacteria. In contrast, a high proportion of 16:1ω7 and ω3 FA (including eicosapentaenoic) was present in the lipid reserve fraction of copepods grown on diatoms. 2. Copepods that were grown on cyanobacteria showed reduced survival and took 26% more time to develop from the first copepodid stage to adult than copepods that were grown on diatoms. Copepods feeding on the cyanobacteria showed reduced FA content when compared with animals fed with diatoms. This reduction in FA content was more pronounced in the apolar lipid fraction (mainly reserve lipids) than in the polar (mainly structural) lipid fraction. 3. The FA profiles of algae were used to calculate a function discriminating between diatoms and cyanobacteria. This function was applied to the FA profiles in the reserve lipid fraction of copepods and correctly classified copepod diet. 16:1ω7, 18:2ω6 and 20:5ω3 were the most important FA in the discriminant function. The suitability of this chemometric method to infer copepod diet was further tested by using algal class FA data from literature to derive the discriminant functions. The correct classification of the diet when the functions were applied to FA composition of the copepod reserve lipids suggests that this method may be employed in trophic web studies. 18:3ω3, 18:1ω9 and 16:1ω7 were the most important FA in the functions discriminating diatoms, cyanobacteria and green algae. The identification and quantification of the whole suit of 16:1ω7, 18:1ω9, 18:2ω6, 18:3ω3 and 20:5ω3 in trophic web studies is therefore of paramount importance to infer diet origin of aquatic herbivores. 4. The FA profile of copepod polar lipids did not reflect that of the diet. The presence of long chain polyunsaturated FAs in the polar lipid fraction of copepods feeding on the cyanobacterium suggests that C18 FAs from the diet may be elongated and desaturated by the copepod. The ability to elongate and desaturated FAs may reduce the importance of some FAs as diet biomarkers while it may turn the copepods into valuable trophic intermediaries in transferring organic matter from microorganisms to higher trophic levels.     

Variabilités verticale et temporelle des acides gras d'un phytoplancton lacustre au cours d'un cycle nycthéméral

Vertical and temporal variability in the content and composition of fatty acids in the lake phytoplankton were studied during a diel cycle (48 h). There is temporal variability in total fatty acid (FA) content per biomass unit but it is not strictly diurnal. In contrast, polyunsaturated FA with 20–22 C chains and unsaturated FA/ saturated FA ratio are higher during the day than during the night.The temporal variability was not as great as the variability is between sampling depths characterized by different phytoplankton assemblages. Phytoplankton composition and physiological state were the principal factors affecting FA composition. Thus, a C16:1w7/C18:1w9 ratio distinguishes between diatoms, with a high level of C16 unsaturated FA, and dinoflagellates with C18 unsaturated FA. This ratio was different at the surface and at 20 m depth, where the phytoplankton had the same taxonomic composition but a different physiological activity.

     

Fatty acid production by heterotrophic Chlorella saccharophila

The fatty acid composition of the alga Chlorella saccharophila was investigated under different growth conditions. Using glucose as the sole carbon source, heterotrophically-grown Chlorella saccharophila produced a greater proportion of the polyunsaturated fatty acids (C18: 2 and C18: 3) than photosynthetic cultures, with linoleic acid (C18: 2) predominating. An unexpected discovery was the observation that at the lowest glucose concentration (2.5 gl^–1) the lipid content of the algae increased to between 36–47% of the cell weight, depending on the temperature. At glucose concentrations of 5 g l^–1 or more, the lipid content fell to 10–12% of the cell, although total fatty acid yield was higher due to higher biomass concentrations. Aeration of heterotrophic cultures promoted the production of unsaturated fatty acids compared to non-aerated cultures.     

The effect of cadmium on lipid and fatty acid biosynthesis in tomato leaves

This research aims to examine the effect of cadmium uptake on lipid composition and fatty acid biosynthesis, in young leaves of tomato treated seedlings (Lycopersicon esculentum cv. Ibiza F1). Results in membrane lipids investigations revealed that high cadmium concentrations affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the unsaturated fatty acid content, resulting in a lower degree of fatty acid unsaturation. The level of lipid peroxides was significantly enhanced at high Cd concentrations. Studies of the lipid metabolism using radioactive labelling with [1-¹⁴C]acetate as a major precursor of lipid biosynthesis, showed that levels of radioactivity incorporation in total lipids as well as in all lipid classes were lowered by Cd doses. In total lipid fatty acids, [1-¹⁴C]acetate incorporation was reduced in tri-unsaturated fatty acids (C16:3 and C18:3); While it was enhanced in the palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0) and linoleic (C18:2) acids. [1-¹⁴C]acetate incorporation into C16:3 and C18:3 of galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] and some phospholipids [phosphatidylcholine (PC) and phosphatidylglycerol (PG)] was inhibited by Cd stress. Our results showed that in tomato plants, cadmium stress provoked an inhibition of polar lipid biosynthesis and reduced fatty acid desaturation process.     

FATTY ACID CONTENT AND CHEMICAL COMPOSITION OF FRESHWATER MICROALGAE1

Fatty acid (FA), total lipid, protein, amino acid, carbon, nitrogen, and phosphorus content was analyzed in 24 samples of freshwater microalgae. The samples originated from batch, continuous, or mass cultures in various growth phases and from net samples from lakewater. FA were analyzed quantitatively by using an internal standard in a GLC system and expressed as mg·g^?1 dry weight (DW). The FA of one group of blue-greens (e.g. Oscillatoria and Microcystis) were similar to those of the greens with higher amounts of 18C acids of the ω3 type compared to the ω6 type, whereas the other group (e.g. Anabaena and Spirulina) contained mostly ω6 acids. The flagellates, a taxonomically diverse group, were characterized by high amounts of long-chained (20–22 C) polyunsaturated FA (PUFA), particularly of the ω3 type. The ω3/ω6 ratio appears to be highest in algae in the exponential growth phase. The increased lipid content in stressed algae was mostly due to increased saturated fatty acids and ω6 acids, whereas the valuable ω3 acids were unchanged or even decreased. Amino acid composition (% of total amino acids) did not vary much betaken species, but when analyzed quantitatively (mg-g^?1 DW), varied considerably between species and within species in different growth phases. The nitrogen and phosphorus contents were variable in all three algal groups. The relationship between PUFA and phosphorus content differed among the algal groups. The data suggest that PUFA in the phospholipids consist mostly ω3 acids.     

Changes in fatty acid composition of lipids in chloroplast membranes of tobacco plants during cold hardening

Changes in fatty acid composition of chloroplast membrane lipids were investigated using tobacco (Nicotiana tabacum L., cv. Samsun) plants subjected to cold hardening for 6 days at 8°C. Under optimal growing temperature (22°C), the lipids of thylakoid membranes were characterized by elevated content of 16:3n-3 and 18:3n-3 fatty acids (FA). Compared to the lipids of chloroplast envelope membranes, the thylakoid lipids were less rich in the content of saturated, mono- and diunsaturated FA. The relative content of unsaturated FA in chloroplast membranes increased substantially during cold hardening, which was mainly due to the accumulation of 18:3n-3 FA. It is concluded that the observed changes in FA composition of chloroplast lipids during cold hardening adjust the fluidity of these membranes to the level sufficient for functioning of tobacco photosynthetic apparatus, which is a prerequisite for accumulation of assimilates and allows the hardened tobacco plants to survive under conditions of hypothermia.     

Fatty acid content during reconstitution of the photosynthetic apparatus in the air-dried leaves of Xerophyta scabrida after rehydration

Desiccation of Xerophyta scabrida caused considerable damage of chloroplast ultrastructure together with a complete loss of chlorophyll. Upon rehydration, the relative water content of the pale-green leaves almost reached that of the dark-green ones, however, the Chl content and photosynthetic activity remained lower. The process of reconstitution of the photosynthetic apparatus in the re-greening leaves was accompanied by changes in fatty acid (FA) content. The amount of the FA methyl esters was more than 2-fold higher in the green leaves as compared to the dry ones and slightly increased after rehydration in the pale-green leaves. Among the three main fatty acids in the leaves, oleic, palmitic and linoleic acid, the latter increased more than 3-fold during rehydration. This acid is concentrated mainly in the glycolipids and this was an indirect indication for the restoration of the photosynthetic apparatus. Our results showed that rehydration of X. scabrida led to a decrease of the saturated FA in parallel with an increase of the unsaturated FA, thus indicating increased membrane permeability. The observed changes in the lipid content can be considered as a characteristic feature of X. scabrida and most probably of other poikilochlorophyllous species.     

Hydrogen isotopic fractionations during desaturation and elongation associated with polyunsaturated fatty acid biosynthesis in marine macroalgae

Compound-specific hydrogen isotopic compositions (deltaD) of saturated, monounsaturated and polyunsaturated fatty acids have been determined for natural marine macroalgae including two brown algae (Heterokontophyta) and two red algae (Rhodophyta). deltaD values of individual fatty acids from four macroalgae exhibit a wide variation ranging from -189% to +48%. Generally, stearic (18:0), arachidic (20:0) and behenic acids (22:0) are much more enriched in D by up to approximately 180% relative to myristic (14:0), palmitic (16:0), octatetraenoic [18:4(n-3)] and eicosapentaenoic acids [20:5(n-3)]. Other fatty acids such as oleic [18:1(n-9)], lenoleic [18:2(n-6)] and linolenic acids [18:3(n - 3)] fall isotopically between these fatty acids. This wide deltaD variation of fatty acids is probably explained by the hydrogen isotopic fractionation during desaturation being much larger than that during elongation in the network of polyunsaturated fatty acid biosynthesis. A large hydrogen isotopic fractionation during desaturation may cause D-enrichment in the remaining hydrogen of the residual fatty acids, which could be controlled by the relative flux into their desaturates.     

A Temperature Dependence of the Intra- and Extracellular Fatty-Acid Composition of Green Algae and Cyanobacterium

The effect of ambient temperature on the composition of intracellular fatty acids and the release of free fatty acids (FFA) into a medium by cyanobacterium Spirulina platensis and eukaryotic microalgae, Chlorella vulgaris and Botryococcus braunii, was studied using their batch cultures. It was found that all the species studied, regardless of their taxonomic status, responded to the temperature regime by similar changes in their intracellular fatty acid composition: the relative content of more unsaturated fatty acids decreased with the elevation of temperature. At the same time, in the prokaryote, this temperature shift blocked, first of all, the elongation of 16:0 to 18:0 and then their further desaturation. In eukaryotes, the change in the desaturation of dienoic to trienoic fatty acids was the most pronounced process. The ratio of dienoic to trienoic fatty acids remained almost unchanged in S. platensis. The relative content of extracellular unsaturated FFA increased in the prokaryotic organism S. platensis at a higher temperature. But no significant changes in the composition of extracellular unsaturated FFA were detected in eukaryotic algae upon temperature elevation.     

Changes in the content and composition of lipid fatty acids in tobacco leaves and roots at low-temperature hardening

Changes in the fatty acid (FA) composition of leaf and root lipids of heat-loving tobacco (Nicotiana tabacum L., cv. Samsun) plants during low-temperature hardening (8°C for 6 days) were studied. Hardening could improve leaf but not root cold tolerance. As this took place, the relative content of polyunsaturated (18:2n-6 and 18:3n-3) FAs increased and the proportion of saturated and monounsaturated FAs decreased. In contrast, in the roots hardening slightly increased the concentration of saturated FAs (16:0 and 18:0) and reduced the level of unsaturated FAs (18:1n-9, 18:2n-6, and 18:3n-3). At the same time, root lipids contained much C_20–24 FAs, and their content increased during hardening. It was suggested that an increased FA saturation and elevated proportion of C_20–24 FAs in the root lipids resulting in the lower membrane fluidity could be a reason for incapability of heat-loving tobacco plant roots of hardening and plant death at the lowtemperature stress.     

Effects of fatty acid and phosphorus content of food on the growth, survival and reproduction ofDaphnia

1. Mixtures of microencapsulated lipids and Scenedesmus quadricauda grown at different degrees of P limitation were used as food for Daphnia galeata in two growth experiments. Thereby, food quality in terms of ω3-fatty acid (ω3-FA) or phosphorus (P) content could be assessed without interference from other factors.
2. ω3-highly unsaturated fatty acids (ω3-HUFA), given to Daphnia as fish oil or eicosapentaenoic acid (EPA) together with non P-limited algae, decreased the time to first reproduction. When fed fish oil, somatic growth and survival were also enhanced. Linolenic acid also decreased the time to first reproduction but to a lesser extent than EPA.
3. Food quality depended to a large extent on the degree of P limitation of Scenedesmus , which is consistent with P limitation of Daphnia. The overall impact of P was always larger than the effect of ω3-FA. Growth, survival and reproduction were elevated when Daphnia were fed non P-limited Scenedesmus compared to treatments with P-limited algae.
4. The relative importance of ω3-HUFA and P content in the food changed over a C : P gradient, with stronger effects of ω3-HUFA at low C : P ratios.     

Temperature responses of growth, photosynthesis, fatty acid and nitrate reductase in Antarctic and temperate Stichococcus

Stichococcus, a genus of green algae, distributes in ice-free areas throughout Antarctica. To understand adaptive strategies of Stichococcus to permanently cold environments, the physiological responses to temperature of two psychrotolerants, S. bacillaris NJ-10 and S. minutus NJ-17, isolated from rock surfaces in Antarctica were compared with that of one temperate S. bacillaris FACHB753. Two Antarctic Stichococcus strains grew at temperature from 4 to 25°C, while the temperate strain could grow above 30°C but could not survive at 4°C. The photosynthetic activity of FACHB753 at lower than 10°C was less than that of Antarctic algae. Nitrate reductase in NJ-10 and NJ-17 had its optimal temperature at 20°C, in comparison, the maximal activity of nitrate reductase in FACHB753 was found at 25°C. When cultured at 4–15°C a large portion of unsaturated fatty acids in the two Antarctic species was detected and the regulation of the degree of unsaturation of fatty acids by temperature was observed only above 15°C, though the content of the major unsaturated fatty acid αC18:3 in FACHB753 decreased with the temperatures elevated from 10 to 25°C. Elevated nitrate reductase activity and photosynthetic rates at low temperatures together with the high proportion of unsaturated fatty acids contribute to the ability of the Antarctic Stichococcus to thrive.     

RISING WATER TEMPERATURES ALTER LIPID DYNAMICS AND REDUCE N‐3 ESSENTIAL FATTY ACID CONCENTRATIONS IN SCENEDESMUS OBLIQUUS (CHLOROPHYTA)1

The biosynthesis of nutritionally important polyunsaturated fatty acids (PUFAs) in phytoplankton is influenced by environmental temperature. We investigated the potential of climate warming to alter lipid dynamics of Scenedesmus obliquus (Turpin) Kütz. by comparing lipid and fatty acid (FA) profiles as well as FA metabolism (using [1‐¹⁴C] acetate) at 20°C and 28°C. We documented an overall decline (53%–37%) in the proportion of n‐3 PUFA (in particular, of α‐linolenic acid [ALA; 18:3n‐3]), and a concomitant increase in saturated fatty acids (SAFAs) in total lipids (TLs) at 28°C, consistent with enhanced incorporation of radioactivity from [1‐¹⁴C] acetate into total 16:0, 18:1, and decreased incorporation into 18:2 and 18:3 FA (from 36% to 22% of the total) at 28°C. Glycerophospholipids were also affected by warming; ALA and stearidonic acids (SDAs; 18:4n‐3) both decreased (by 13% and 15%, respectively) in phosphatidylcholine (PC) and (by 24% and 20%, respectively) in phosphatidylethanolamine (PE). The characteristic FA in phosphatidylglycerol (PG; 16:1n‐13t) increased (by 22%) at 28°C. The activities of desaturases, which add double bonds to FA moieties, comprised the major suite of reactions affected by the temperature increase in TL and polar lipid (PL) classes. Climate modelers predict an increase in the number of extreme heat days in summer at temperate latitudes, with parallel projected increases in water temperatures of shallow water bodies. Our results suggest that the overall decrease in the essential n‐3 FA ALA in S. obliquus at higher water temperatures may lower food quality for higher tropic levels, adding another climate‐warming stress.     

Effects of the season and growth stage on the contents of lipids and photosynthetic pigments in brown alga <Emphasis Type="Italic">Undaria pinnatifida</Emphasis>

Seasonal changes in the contents of lipids and photosynthetic pigments (PSP) in the brown alga Undaria pinnatifida (Harvey) Suringar (Phaeophyceae, Alariaceae) on different stages of its growth were studied. Lipids of all plant growth group comprised glyceroglycolipids (GL), phospholipids, and neutral lipids (NL). The ratio between these lipid groups and the content of particular lipids depended on the season and algal growth stage: NL predominated in seedlings; juvenile algae comprised approximately similar amounts of NL and GL; and in adult algae, GL predominated. In winter and spring, algal tissues contained relatively more free sterols than in summer. Total lipid content in seedlings and juvenile algae was higher then in adult plants. Lipid fatty acid (FA) composition was similar on all growth stages, but the content of major components differed; this is mainly related to 18:4 n-3, 20:4 n-6, and 20:5 n-3 acids. The predominant FAs in seedling lipids were saturated FAs, whereas in the lipids of juvenile and adult algae, polyunsaturated FAs predominated.     

Using lipidomics to reveal details of lipid accumulation in developing Siberian apricot (Prunus sibirica L.) seed kernels

Siberian apricot seed kernel (SASK) contains a high of 50% oil with suitable fuel properties conformed to biodiesel standard. To date, Prunus sibirica is a novel non‐crop feedstock for biodiesel production in China. Here, oil contents and fatty acid (FA) compositions were identified in developing SASK from AS‐80 and AS‐84, at intervals of 1 week from 3 weeks after anthesis (WAA) to 9 weeks. The major differences in oil content between C18:1 and C18:2 levels were greater among the AS‐80 (32.69/15.48 g/100 g) than among the AS‐84 (25.78/13.15 g/100 g). Subsequently, the SASKs from 4, 6, and 8 WAA, respectively, representing early, middle, and late phases of oil accumulation, were selected as optimal samples for lipidomics analysis. It was notable that 18:1/18:1/18:2, 18:1/18:1/18:3, and 18:2/18:2/18:2 were the prominent compositions in triacylglycerol (TAG), and their higher content found among the AS‐80 was consistent with FA results. Although phosphatidic acid (PA) is directly connected with diacylglycerol (DAG) in Kennedy pathway, we found significant difference between PA and DAG compositions. The resulting molecular species differ in acyl composition depending on whether they were generated via phosphatidylcholine (PC) or Kennedy pathway. By qRT‐PCR analysis, the expression levels of FAD3, PDCT, and DAG‐CPT related to the biosynthesis of polyunsaturated fatty acids (PUFAs) showed a gradual decrease with SASK mature, explaining the drastic change of DAG‐18:3/18:3 content. Additionally, the lipidomics data coupled with qRT‐PCR analysis suggested that phospholipid:DAG acyltransferase may play a critical role in incorporation of PUFAs into sn‐3 of TAG. Our data contribute significantly to understand the underlying mechanisms of lipid accumulation in P. sibirica, and may also present strategies for engineering oil accumulation in oilseed plants.     

CHEMICAL PROFILE OF SELECTED SPECIES OF MICROALGAE WITH EMPHASIS ON LIPIDS1

The lipid profile of seven species of unicellular eukaryotic microalgae grown under controlled conditions was studied with emphasis on the hydrocarbons and the fatty acids as part of a search for oil-producing algae. Green, slow-growing colonies of Botryococcus braunii Kutz contained the highest lipid content of 45% based on the organic weight, with an increase to 55% under nitrogen deficiency and with no effect of sodium chloride stress. Ankistrodesmus sp. Thomas, Dunaliella spp., Isochrysis sp., Nannochloris sp. Thomas, and Nitzschia sp. Chapman contained an average of 25% lipids under nitrogen sufficient conditions. Nitrogen deficiency resulted in significant increase in the lipid content in all species but Dunaliella spp., which produced a higher content of carbohydrates. Significant low amounts of acyclic hydrocarbons were detected only in Botryococcus braunii Kutz and not in the other algae. The major hydrocarbon fractions in nitrogen deficient Botryococcus braunii Kutz, Dunaliella salina Thomas, Isochrysis spp. and Nannochloris sp. Thomas were cyclic and branched polyunsaturated components which were identified as various isoprenoid derivatives. The polar lipid composition of glycolipids and phospholipids of all species investigated was fairly typical of photosynthetic eukaryotic algae. Fatty acid composition was species specific, with changes occurring in the relative amounts of individual acids of cells cultivated under different conditions and growth phases. All species synthesized C14:0, C16.0, C18:1, C18:2 and C18:3 fatty acids; C 16:4 in Ankistrodesmus sp. Thomas; C18:4 and C 22.6 in Isochrysis sp.; C16:2, C16:3 and C20:5 in Nannochloris sp. Thomas; C16:2, C16:3 and C20:5 in Nitzschia sp. Chapman. Nitrogen deficiency and salt stress induced accumulation of C18:1 in all treated species and to a lesser extent in Botryococcus braunii Kutz. The low production of hydrocarbons under optimal growth conditions and the high production of hydrocarbons under limited growth conditions cannot support the notion that microalgae can be utilized as biosolar energy converters for the production of liquid fuel, but point to the availability of a variety of neutral and polar lipid products.     

Characterization of fatty acid composition in healthy and bleached corals from Okinawa, Japan

Under bleaching conditions, corals lose their symbiotic zooxanthellae, and thus, the ability to synthesize fatty acids (FAs) from photosynthetically derived carbon. This study investigated the lipid content and FA composition in healthy and bleached corals from the Odo reef flat in Okinawa, southern Japan, following a bleaching event. It was hypothesized that the FA composition and abundance would change as algae are lost or die, and possibly microbial abundance would increase in corals as a consequence of bleaching. The lipid content and FA composition of three healthy coral species (Pavona frondifera, Acropora pulchra, and Goniastrea aspera) and of partially bleached and completely bleached colonies of P. frondifera were examined. The FA composition did not differ among healthy corals, but differed significantly among healthy, partially bleached, and completely bleached specimens of P. frondifera. Completely bleached corals contained significantly lower lipid and total FA content, as well as lower relative amounts of polyunsaturated FAs and higher relative amounts of saturated FAs, than healthy and partially bleached corals. Furthermore, there was a significantly higher relative concentration of monounsaturated FAs and odd-numbered branched FAs in completely bleached corals, indicating an increase in bacterial colonization in the bleached corals.     

Feeding spectra of <Emphasis Type="Italic">Arctodiaptomus salinus</Emphasis> (Calanoida,Copepoda) using fatty acid trophic markers in seston food in two salt lakes in South Siberia (Khakasia,Russia)

During two vegetation seasons (2004–2005), we compared feeding spectra of Arctodiaptomus salinus (Calanoida, Copepoda) populations inhabiting two neighboring salt lakes, Shira and Shunet, Khakasia, Russia, using fatty acid (FA) trophic markers. Sestonic FA composition in two lakes moderately differed, whereas levels of diatom FA markers were higher in Lake Shunet and of Cyanobacteria and green algae markers in Lake Shira. In general, markers in storage lipids—triacylglycerols (TAG) of A. salinus—reflected the differences in sestonic composition of the two lakes. Nevertheless, TAG fraction was also enriched by FA trophic markers of the minor components of seston, which were selectively ingested by the animals. In Lake Shira, A. salinus had significantly higher concentrations of bacterial FA markers in TAG. In Lake Shunet, TAG of A. salinus contained significantly higher relative amounts of 18:4ω3, 18:5ω3 and C22 polyunsaturated fatty acids (PUFA), which indicated marked contribution of cryptophytes or (and) flagellates into the diet. Laboratory experiments showed feeding on Cryptomonas and sulfur purple bacteria in Lake Shunet and ciliates and colonial picoplankton in both lakes, and generally confirmed the differences in FA trophic markers in A. salinus between the lakes. The two populations of A. salinus markedly differed in levels of essential long-chain PUFA, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, although the levels of these FA in seston were quite similar between the two lakes. The higher levels of the essential ω3 PUFA in A. salinus in Lake Shunet may be an adaptive response of the animals to a vertical stratification of physico-chemical conditions and significantly higher salinity levels at the boundary of adjacent bottom layer in this lake.     

Modulation of polyunsaturated fatty acids in mixotrophic Karlodinium veneficum (Dinophyceae) and its prey,Storeatula major (Cryptophyceae)1

We examined whether fatty acid (FA) composition changed when Karlodinium veneficum (D. Ballantine) J. Larsen (Dinophyceae) was grown phototrophically or mixotrophically on Storeatula major Butcher ex D. R. A. Hill (Cryptophyceae). We hypothesized that the FA composition of mixotrophic K. veneficum would not change relative to the FA composition of phototrophic K. veneficum. As in other phototrophic dinoflagellates, octadecapentaenoic acid (18:5n3) represented 9% to 20% of total FA in K. veneficum and was enriched within chloroplast‐associated galactolipid classes. The 18:5n3 content showed a highly significant positive correlation (r² = 0.95) with chl a content and a highly significant negative correlation with growth rate (r² = 0.88). A previously undescribed chloroplast galactolipid molecular species, digalactosyldiacylglycerol (DGDG; 18:5n3/18:5n3), was a dominant structural lipid in K. veneficum. Docosahexaenoic acid (22:6n3) represented 14% to 19% of total K. veneficum FA and was enriched within phospholipids. In the prey S. major, 18:5n3 was not present, but octadecatetraenoic acid (18:4n3) and α‐linolenic acid (18:3n3) represented approximately 50% of total FA and were enriched within chloroplast‐associated galactolipid classes. Eicosapentaenoic acid (20:5n3) and 22:6n3 represented approximately 18% of total FA in S. major and were enriched within phospholipids. The FA profile of mixotrophic K. veneficum, compared to phototrophic K. veneficum, showed elevated levels of 18:3n3, 18:4n3, and 20:5n3, and lower but persistent levels of 18:5n3. Production to ingestion (P:I) ratios >1 for major polyunsaturated fatty acids (PUFAs) indicated that direct assimilation from prey under balanced growth could not support rates of PUFA production in mixotrophic K. veneficum. These data suggest that the plastid plays a continuing and essential role in lipid metabolism during mixotrophic growth.