Nutritional analysis of freshwater and marine amphipods from the Strait of Gibraltar and potential aquaculture applications

Four gammarid and four caprellid amphipod species from the Strait of Gibraltar were analyzed to study their nutritional contents: Caprella dilatata, Caprella equilibra, Caprella grandimana, Caprella penantis, Elasmopus rapax, Hyale perieri and Jassa sp. from marine water habitats and Echinogammarus sp. from freshwater habitats. Lipids, proteins, carbohydrates, ash and water contents were measured. Proteins and ash were the most abundant components in all the species, ranging between 37.9 and 44.6% and 29.3 and 39.7% dry weight, respectively. The lipid and carbohydrate contents showed lower levels (5.1–9.6% and 3.1–9.1% dry weight, respectively). No significant differences in general biochemical composition were found between gammarid and caprellid species. The most abundant fatty acids were the polyunsaturated ones (38.3%) with high levels of EPA (20:5(n-3)) with 8.5 to 17.7%, DHA (22:6(n-3)) with 0.9 to 13.6% and ARA (20:4(n-6)) with 1.7 to 5.8%. Caprellid species were characterized by a higher percentage of polyunsaturated fatty acids, while the freshwater gammarid species showed the lowest levels. According to lipid classes, caprellids had higher phospholipids levels and lower triacylglycerol levels, as well as a higher content of polar lipids than the gammarids, being more suitable for their use in aquaculture. Differences in the general biochemical composition between species can be related to habitat characteristics, diets and environmental conditions. Advantages and disadvantages of the use of these organisms in aquaculture are discussed.     

High levels of n−3 polyunsaturated fatty acids in Euphausia pacifica and its role as a source of docosahexaenoic and icosapentaenoic acids for higher trophic levels

In Euphausia pacifica specimens, phospholipids (PL, 44.1–81.2%) such as phosphatidylethanolamine (PE, mean±standard error, 26.1±2.1%) and phosphatidylcholine (PC, 29.0±2.3%) were found to be the dominant lipids. Compared to many other marine organisms, the level of PL was markedly high. The major fatty acids in the TAG of E. pacifica were saturated fatty acids (SFA, 14:0 and 16:0), monounsaturated fatty acids (MUFA, 16:1 and 18:1), and polyunsaturated fatty acids (PUFA, 18:4 n−3 and 20:5 n−3, icosapentaenoic acid: EPA). The only fatty acids found in the tissue PL were SFA (16:0), MUFA (18:1), and PUFA (20:4 n−6, arachidonic acid: AA, EPA, and 22:6 n−3, docosahexaenoic acids: DHA). The comparatively high levels of 14:0, 16:0, 16:1 n−7, 16:2 n−4, 16:4 n−1, 18:1 n−7, 18:1 n−9, 18:4 n−3, and EPA in the TAG may be affected by the lipid composition of its phytoplankton prey, such as diatoms, which generally contain high amounts of these fatty acids. The levels of short chain 14:0, 16:1 n−7, 16:2 n−4, 16:4 n−1, 18:1 n−9, and 18:4 n−3 decreased in PL, while AA, EPA, and DHA increased. In particular, the levels of n−3 PUFA in PL were markedly high in all specimens. The mean proportion of EPA plus DHA accounted for more than 45% (55.0% in PE and 47.7% in PC) of the total fatty acids. These results suggest that E. pacifica, which contains markedly high levels of EPA and DHA, may biosynthesize these PUFA by carbon chain elongation and desaturation or selectively accumulate n−3 PUFA. In addition, their lipids may be an important source of n−3 PUFA for higher marine animals, such as the pelagic marine fishes (sardines, anchovies, and other small fishes), which mainly prey on these euphausiids. Marine fish accumulate high levels of these n−3 PUFA because they are unable to synthesize DHA.     

The relationship between fatty acid distributions and bacterial respiratory types in contemporary marine sediments

Bacterial communities of different respiratory types were isolated from a marine sediment in a multiple chemostat system in an attempt to obtain bacterial cultures representative of the sediment. The fatty acid distribution of a mixed culture of sulphate-reducing bacteria isolated from this system showed a good correlation with the lipid distribution of the zone of maximum sulphate-reduction activity within the sediment. Both distributions had significant concentrations of C14 : 0, iso and anteiso C15 : 0, C16 : 0, C16 : 1ω7 and C18 : 1ω7. This was in contrast to the lipid profile of Desulfovibrio desulfuricans obtained by batch enrichment, which was dominated by iso C17 : 1ω7 fatty acids and correlated poorly with the sediment. The bacterial community cultured from the sediment was further differentiated according to respiratory types (aerobic, facultative aerobic and facultative anaerobic) by growth in a chemostat under defined conditions. The fatty acid distributions of these communities were sufficiently different to enable the various respiratory types to be recognized by their particular fatty acid composition. Cyclopropyl fatty acids (?17 and ?19) were present in significant levels only in the aerobic bacteria, while the facultative aerobes had significantly higher C18 : 1ω7 than the other cultures and the facultative anaerobic community was the only culture to have significant amounts of C12 : 0. The fatty acid distribution of Loch Eil sediment over the range C12-19 seemed to be predominantly of bacterial origin and were relatively abundant to a depth of 6 cm. The concentration of cyclopropyl fatty acids was highest in the oxidized surface sediments and decreased with depth as anaerobic conditions began to dominate, indicating that these fatty acids may only be indicative of aerobic sedimentary bacteria. In contrast to the fatty acids characteristic of bacteria, those fatty acids in the range C20-30 attributed to a terrestrial input were found in relatively constant concentrations over the whole 0–12 cm depth profile.     

闽南及闽中近海常见鲨鳐类肝油的脂肪酸组成

闽南及闽中近海鲨鳐类肝油的脂肪酸组成相似,主要的脂肪酸包括16:0(14.9%～23.7%),18:0(5.3%～10.4%),18:1ω9(8.6%～16.9%),16:1(3.4%～7.5%),20:4ω6(3.8%～14.7%)和22:6ω3(10.7%～36.9%).22:6ω3在分析的所有种类(基齿鲨Hypoprion sp除外)均是含量最高的脂肪酸成分.可见,闽南及闽中近海鲨鳐类肝油是22:6ω3良好的来源.底层生活习性种类肝油ω6PUFA的含量高于中上层种类,而中上层生活习性种类肝油22:6ω3的含量以及ω3PUFA与ω6PUFA的比值则相对地高于底层种类,这种现象可能与它们各自的摄食习性有关.     

Biomarkers derived from heterolytic and homolytic cleavage of allylic hydroperoxides resulting from alkenone autoxidation

Laboratory incubation of alkenone mixtures with tert-butyl hydroperoxide and di-tert-butyl nitroxide (radical initiator) in hexane, as a means to simulate alkenone autoxidation processes, rapidly led to the formation of allylic hydroperoxides, whose presence was recently demonstrated in Emiliania huxleyi cells. After incubation in seawater and subsequent reduction with NaBH₄ (to reduce residual hydroperoxides before analysis), these reaction products quickly disappeared and were replaced by complex mixtures of n-alcohols, fatty acids, alkyldiols and hydroxyacids. Methyl alkenones produced saturated n-alkan-1-ols and fatty acids ranging from C₁₃ to C₁₆ and two series of C₁₃−C₁₆ (ω-1)-hydroxyacids and (1,ω-1)-diols. Ethyl alkenones also afforded C₁₃−C₁₆ saturated n-alkan-1-ols and fatty acids, accompanied by the production of C₁₄−C₁₇ (ω-2)-hydroxyacids and (1,ω-2)-diols. Deuterium labelling allowed us to show that most of the n-alkan-1-ols, hydroxyacids and alkyldiols resulted from the reduction during the NaBH₄ treatment of the corresponding aldehydes, ketoxyacids and ketoxyaldehydes formed from heterolytic or homolytic cleavages of allylic hydroperoxyl groups resulting from the oxidation of the double bonds of di- and triunsaturated alkenones. Amongst these products, the (ω-1)- and (ω-2)-hydroxyacids formed after NaBH₄ reduction of the (ω-1)- and (ω-2)-ketoxyacids were selected as potential biomarkers for alkenone autoxidation. Re-examination of lipid extracts of post-bloom seawater particulate matter samples from the DYFAMED station in the Ligurian Sea (where strong autoxidative alteration of the lipid distributions had previously been detected) showed the presence of significant amounts of 12-hydroxytetradecanoic, 13-hydroxytetradecanoic, 14-hydroxyhexadecanoic and 15-hydroxyhexadecanoic acids thus providing good evidence that these autoxidative processes occur in natural samples.     

褐菖鲉(Sebastiscus marmoratus)受精卵以及仔鱼期氨基酸与脂肪酸变化研究

为研究褐菖鲉(Sebastiscus marmoratus)发育早期氨基酸和脂肪酸的组成及变化规律,采用GC/MS法等方法分析了褐菖鲉的受精卵、初产仔鱼、前仔鱼期和后仔鱼期四个阶段的氨基酸和脂肪酸组成特点及其含量变化。结果表明:(1)总氨基酸含量从受精卵至初产仔鱼显著下降、前仔鱼期又显著回升、至后仔鱼期再次呈显著下降(P0.05);(2)总游离氨基酸量以初产仔鱼最高,是受精卵的10倍,各期的游离氨基酸占总氨基酸比值为1.4%—20.0%;(3)受精卵中以DHA、C16:0两者实际含量最高,分别为104.88 mg/g和68.74 mg/g,C18:1n-9和EPA次之,分别为41.23 mg/g和27.23 mg/g;(4)褐菖鲉内源性营养阶段被选择性消耗的主要脂肪酸依次为C16:0C18:1EPADHAARA,就脂肪酸的利用率而言MUFASFAPUFA;(5)褐菖鲉仔鱼在开口后的外源营养阶段对脂肪酸的利用率为PUFASFAMUFA,其中DHA相对EPA和ARA被选择性消耗。研究表明,褐菖鲉受精卵的游离氨基酸/总氨基酸比值符合海水鱼类沉性卵的特征,褐菖鲉在早期发育不同阶段对脂肪酸消耗具有不同的选择性,C16:1、C16:0、C18:0和C18:1是褐菖鲉早期发育的主要能源物质,在褐菖鲉开口饵料中添加一定水平的异亮氨酸、亮氨酸、酪氨酸等氨基酸及高度不饱和脂肪酸DHA等是十分必要的。     

Fish community structure of the St Lucia Estuarine System under prolonged drought conditions and its potential for recovery after mouth breaching

The St Lucia Estuarine System, South Africa, has been under pressure due to recent drought conditions, which have led to closure of the mouth, extremely low lake levels and hypersaline conditions. The estuary mouth closed in June 2002 and remained so for almost 5 years before being breached by Cyclone Gamede in May 2007. After mouth closure in August 2007, salinities in South and North Lake gradually increased to reach highs of 68 at the end of 2008, while salinities in the Narrows gradually declined during the study. Fish were sampled biannually during 2006–2008 with seine and gill-nets at six sites throughout the system. A total of 20,422 fish from 72 species were recorded, with the number of species and CPUE gradually decreasing from the Narrows throughout the system to Hells Gate in the upper parts of the system. The fish community was dominated by the freshwater species Oreochromis mossambicus, and two estuarine species, Ambassis ambassis and Hyporamphus capensis. The fish community was dominated in terms of species numbers by marine spawning species, but in terms of fish abundance by freshwater and estuarine breeding species. Recruitment of post-larvae of 20 marine species into the system occurred following opening of the mouth in March 2007, highlighting the importance of the system as a nursery area for marine species. The fish community was structured by spatial differences between sampling areas and between the three main compartments of the system, and not by temporal changes during the study period.     

Impact of estuary barrage construction on fish assemblages in the lower part of a river and the role of fishways as a passage

The construction of an estuary barrage, an instream structure in the lower reaches of a river, causes significant physical changes in water flow patterns and river morphology, and results in altered environmental conditions. Here, we examined the impact of the Geum River estuary barrage, completed in 1990, on fish assemblages by using a literature search and fresh surveys of fishways in the barrage. We found that fish assemblages upstream and downstream of the barrage were altered following its completion. After construction, more species were found in the freshwater area, with a particularly great increase in freshwater species. Conversely, estuarine and marine species were only consistently caught in the downstream salt-water area, although the number of species increased. In total, 15,829 fish from 47 species and 20 families were identified at the three types (pool and weir, rubble type, and boat passage) of fishways in the barrage. The dominant species were Chelon haematocheilus, an estuarine species, Coilia nasus, a diadromous species, and Erythroculter erythropterus, a freshwater species. The mean total length of fish (101.9 ± 76.0 mm) in the boat passage fishway was approximately 100 mm lesser than those in the pool and weir (207.2 ± 112.8 mm) and rubble type (205.8 ± 112.7 mm) fishways. The boat passage fishway was the most efficient for fish movements. The current fishway system is not sufficient for fish migration, and thus additional ways are required to improve the system such as the boat passage. Few estuarine or diadromous species were found in both freshwater and salt-water areas, but freshwater fishes that accidently moved to salt-water area actively used fishways. Therefore, fishway management in the Geum River estuary barrage has to focus on freshwater fish; however, this may need to change to a focus on migratory fishes depending on ecological life cycles of migratory fish.     

Lipids of Antarctic Ocean amphipods: food chain interactions and the occurrence of novel biomarkers

Antarctic hyperiid (Themisto gaudichaudi, Hyperia macrocephalus, and Primno macropa) and gammarid amphipods (Eusirus perdentatus and Orchomene rossi) were collected near Elephant Island, located in the South Shetland Islands, during January and February 1997 and 1998. Polar lipid (PL) was the major lipid class in all amphipods (58–88% of total lipid), except for T. gaudichaudi in which triacylglycerol (TAG) was dominant (62%). Cholesterol was the major sterol in the gammarid amphipods (89–91% of total sterols), and the hyperiid P. macropa (70%). The hyperiids T. gaudichaudi and H. macrocephalus had a more diverse sterol composition including trans-dehydrocholesterol, desmosterol, 24-nordehydrocholesterol, 24-methylcholest-5,22E-dien-3β-ol, 24-methylenecholesterol, and stanols (mostly cholestanol). Eicosapentaenoic acid [EPA, 20:5(n−3)] and docosahexaenoic acid [DHA, 22:6(n−3)] were the major polyunsaturated fatty acids (PUFA) in all amphipods. The PUFA octadecapentaenoic acid [18:5(n−3)] was not detected in 1997 samples, but comprised 0.3–1.2% in all 1998 samples. The PUFA 18:4(n−3) comprised 0.2–4.2% in all samples from both years. Very long chain PUFA (VLC-PUFA) (C₂₄ and C₂₆) were not detected in the one 1997 sample but comprised 0.6–2.8% of total fatty acids in almost all 1998 amphipods. Monounsaturated fatty acids included 18:1(n−9)c, 18:1(n−7)c, and 16:1(n−7)c. Principal saturated fatty acids in all amphipods were 16:0, 14:0, and 18:0. Examination of biomarker lipids has helped clarify trophic interactions for these Antarctic amphipods, and revealed annual differences in their food sources.     

Sources and transport of organic carbon to shelf,slope, and basin surface sediments of the Arctic Ocean

Lipids in surface sediment transects across the Arctic Ocean were identified to define the sources of organic carbon and the transport of material in the ocean basin. Sterols representing diatoms (24-methylcholesta-5,24(28)-dien-3β-ol, 24-methylcholesta-5,22-dien-3β-ol) and dinoflagellates (4α,23,24-trimethylcholest-22-en-3β-ol) together with algal polyunsaturated fatty acids (20:5, 22:6) demonstrated the importance of primary production to organic matter inputs on the Chukchi Shelf. The presence of terrestrial biomarkers including long-chain n-alkanes and mono- and dicarboxylic acids in shelf sediments indicated that while the fraction of terrestrial biomarkers was small compared to marine material, the transport of allochthonous material impacts carbon cycling on the shelf. Algal biomarkers were found in all surficial sediments from the central Arctic basins, demonstrating that some fraction of primary production reached bottom sediments despite ice cover and light limitation. Marine markers represented a small fraction of the total lipids in central basin sediments. This implies that the basins are less productive than shallow waters, significant degradation occurs before the organic matter reaches the sediment–water interface, and substantial amounts of vascular plant material are exported to the central Arctic. Circulation and topographical features, such as the Transpolar Drift and the Lomonosov Ridge, appear to have an important influence on the transport and focusing of terrestrial material in the Arctic Ocean basins.     

Fatty acid profiles indicate the habitat of mud snails Hydrobia ulvae within the same estuary: Mudflats vs. seagrass meadows

Mud snails Hydrobia ulvae occupy different habitats in complex estuarine ecosystems. In order to determine if fatty acid profiles displayed by mud snails can be used to identify the habitat that they occupy within the same estuary, fatty acids of H. ulvae from one mudflat and one seagrass meadow in the Ria de Aveiro (Portugal) were analyzed and compared to those displayed by microphytobenthos (MPB), the green leaves (epiphyte-free) of Zostera noltii, as well as those exhibited by the epiphytic community colonizing this seagrass. MPB and epiphytic diatom-dominated samples displayed characteristic fatty acids, such as 16:1n-7 and 20:5n-3, while 18:2n-6 and 18:3n-3 were the dominant fatty acids in the green leaves of Z. noltii. Significant differences between the fatty acid profiles of H. ulvae specimens sampled in the mudflat and the seagrass meadow could be identified, with those from the mudflat displaying higher levels of fatty acids known to be characteristic of MPB. This result points towards the well known existence of grazing activity on MPB by mud snails. The fatty acid profiles displayed by H. ulvae inhabiting the seagrass meadows show no evidence of direct bioaccumulation of the two most abundant polyunsaturated fatty acids of Z. noltii (18:2n-6 and 18:3n-3) in the mud snails, which probably indicates that either these compounds can be metabolized to produce energy, used as precursors for the synthesis of essential fatty acids, or that the snails do not consume seagrass leaves at all. Moreover, the fatty acid profiles of mud snails inhabiting the seagrass meadows revealed the existence of substantial inputs from microalgae, suggesting that the epiphytic community colonizing the leaves of Z. noltii displays an important role on the diet of these organisms. This assumption is supported by the high levels of 20:5n-3 and 22:6n-3 recorded in mud snails sampled from seagrass meadows. In conclusion, fatty acid analyses of H. ulvae can be successfully used to identify the habitat occupied by these organisms within the same estuary (e.g. mudflats and seagrass meadows) and reveal the existence of contrasting dietary regimes.     

神狐海域Site4B表层沉积物中脂肪酸组成及其碳同位素分布特征

通过对神狐海域表层5个沉积物样品进行脂肪酸组成及其碳同位素分布特征测试和研究,结果表明总脂肪酸含量分布为5.14~8.99 μg/g,碳数分布范围从C₁₂到C₃₂,类型包括正构饱和脂肪酸、支链脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸和类异戊二烯酸等计48种;样品中饱和的短链脂肪酸主要来自细菌与浮游生物,而长链饱和脂肪酸来自陆源高等植物,其比例表明研究海域中海洋细菌与浮游生物输入量远远大于陆源高等植物的输入。支链脂肪酸10me16:0与单不饱和脂肪酸18:1ω9、16:1ω9主要来自硫酸盐还原菌,而单不饱和脂肪酸16:1ω7很大可能来源于硫氧化菌,比较相对含量得出神狐海域表层沉积物为还原环境。样品中检测出8种类异戊二烯酸,主要是植烷酸和17,21-ββ二升藿烷酸,及少量的姥鲛酸,推测为叶绿素a和细菌微生物的共同贡献。     

Geochemical and biological marker assessment of depositional environments using Brazilian offshore oils

A combined geochemical and molecular characterization of a wide selection of oils from the major Brazilian offshore basins has been undertaken. The elemental (sulphur, nickel and vanadium) and bulk (^oAPI and δ¹³C) properties of each sample been considered, together with its molecular composition determined using liquid and gas chromatography, and quantitative biological marker investigations using gas chromatography-mass spectrometry for alkanes.The results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups. The distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils. Each group is correlated tentatively with source rocks laid down in a specific depositional regime, namely lacustrine freshwater, lacustrine saline water, marine evaporitic, marine carbonate or marine deltaic. The diagnostic features that allow this classification are: the relative abundance and carbon number distributions of n-alkanes; pristane/phytane ratios; sulphur, nickel and vanadium contents; carbon isotope data; the absolute concentrations of hopanes and steranes, and their abundance relative to 4-methylsteranes and, also the occurrence and abundance of several specific biological markers, including 18α(H)-oleanane, gammacerane, β-carotane, tricyclic terpanes, higher acyclic isoprenoids, 28, 30-bisnorhopane and 25, 28, 30-trisnorhopane. This investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils.     

The application of isotopic and biogeochemical markers to the study of the biochemistry of organic matter in a macrotidal estuary, the Loire, France

The biogeochemistry of organic matter in a macrotidal estuary, the Loire, France, has been studied for two years during different seasons. Both particulate matter and sediment have been sampled in the riverine zone, in the maximum turbidity zone and in the ocean near the river mouth. Two techniques have been used: carbon isotopic ratio determination and analysis of lipid-marker signatures in the n-alkane, n-alkene and fatty acid series. For the period corresponding to the output of the maximum turbidity zone in the ocean, the complete change of organic matter, continental in nature in the inner estuary, pure marine in the outer estuary is well illustrated by the decrease of δ¹³C values and of carbon preference index of n-alkanes. Input sources of organic matter by continental plants, plankton and micro-organisms are discussed from biogeochemical-marker analyses data along with the processes of accumulation of particles and their evolution with the season. Some criteria for evidencing the nature of various organic-matter pools are assessed and compared in different chemical-marker series as follows: high molecular weight n-alkanes and fatty acids, perylene for continental imprints, polyunsaturated 18-, 20- and 22-carbon fatty acids, n-C₁₇, n-alkenes and squalene for algae imprints, branched iso and anteiso fatty acids, Δ11-C_18:1 for microbial imprints.     

Estuarine production of resident and nursery fish species: Conditioning by drought events?

The production of resident (Pomatoschistus minutus and Pomatoschistus microps) and marine juvenile fish species using the Mondego estuary (central Portugal) as nursery grounds (Dicentrarchus labrax, Platichthys flesus, Solea solea), was assessed in order to: (1) understand the potential of the estuary for fish production; (2) know the production of nursery fish species likely to be exported to the coastal stocks; and (3) how anthropogenic and natural stress could influence the estimated production. Sampling occurred from June 2003 to May 2006 and together the 5 species in study comprised around 70% of the whole fish community numbers and biomass. Increasing drought conditions were observed, starting with a normal hydrological year in 2003 until attaining a severe drought in 2005, which resulted in low river discharges (1/3 of the mean river discharges in 2003). Additionally, high water temperatures were observed in 2003 and 2005 (24 and 26 °C, night temperatures). The secondary production was estimated using the increment summation method, after recognition of the cohorts. Production was in general lower in the Mondego estuary when compared to other systems, which was associated to the estuary's small area (only 3.4 km², less than 1/4 of area compared to other studied systems). Dicentrarchus labrax was among the most productive species. Production decreased in the drought year for all species, especially evident for D. labrax, P. minutus and P. flesus. No direct effects could be attributable to the salinity and temperature variations and to the low freshwater discharges (resulting from the drought and high temperatures), yet these were pointed as probable major reasons for the decreased production. A significant reduction (15–45% reduction in the estuarine production) was also concluded for the potential production to be exported for coastal areas by the nursery species in the drought conditions.     

Thermal effects on the growth and fatty acid composition of four harmful algal bloom species: Possible implications for ichthyotoxicity

Little is known regarding how harmful algal bloom species respond to different temperatures in terms of fatty acid production. This study examined the effects of temperature on the growth rates, cell volumes, and fatty acid concentrations and compositions of four harmful algal bloom species (HABs), Akashiwo sanguinea, Alexandrium tamarense, Chattonella ovata, and Prorocentrum minimum. The HABs species were cultured at 15, 20, 25, and 30°C in a nutrient-enriched medium. Three of the species maintained optimal growth rates over a wide range of temperatures, but A. tamarense did not. The cell volumes of each species showed little change over the temperature range. The total fatty acid concentrations in A. sanguinea, A. tamarense and C. ovata decreased as the temperature increased, but P. minimum showed no trend in this respect. Polyunsaturated fatty acids (PUFAs), the key biochemical components that maintain cell membrane fluidity and which are associated with toxicity, decreased in both concentration and proportion of total fatty acids as temperature increased, except in A. sanguinea, in which the proportion of PUFAs to the total fatty acids increased. These reductions in PUFA concentration and proportion could reduce cell membrane fluidity and toxicity in HABs; however, enhanced growth and/or ruptured cells, which are considered more toxic than intact cells, could compensate for the reduced per-cell toxicity. This phenomenon might impact on the marine ecosystem and aquaculture industry.     

Isotopic composition of fatty acids of extremely piezophilic bacteria from the Mariana Trench at 11,000 m

Two extremely piezophilic bacteria, DB21MT-2 and DB21MT-5, isolated from sediments of the Mariana Trench at 11,000 m, were grown in the laboratory under low-temperature (10 °C) and high-pressure (70 MPa) conditions. Phospholipid ester-linked fatty acids (PLFA) were analyzed by gas chromatography/mass spectrometry (GC/MS) and isotopic compositions of individual fatty acids were determined by gas chromatography isotope ratio mass spectrometry (GC-IRMS) in order to determine isotopic fractionation effects during biosynthesis. The piezophiles are characterized by fatty acids with carbon chains ranging from 14 to 22 carbons in length and by the presence of abundant polyunsaturated fatty acids (PUFA). Fatty acids from each culture exhibit a wide range of isotopic compositions (δ¹³C vs. Pee Dee Belemnite (PDB)). With two exceptions (C15:0 and C17:1 from DB21MT-2), all fatty acids are depleted in ¹³C relative to that of bulk carbon in the bacterial growth substrate. In addition, strain DB21MT-2 shows systematically higher (less negative) δ¹³C values than strain DB21MT-5. The implications for isotope fractionation in fatty acid biosynthesis and the interpretation of isotopic composition of sedimentary fatty acids are discussed. It is suggested that the same type of microorganisms could have rather different δ¹³C under the same growth conditions, and that sedimentary fatty acids with distinct δ¹³C values do not necessarily have to originate from different organisms. Interpretation of δ¹³C values of sedimentary biomarkers may be complicated by such large variations in δ¹³C of fatty acids given that they are biosynthesized by the same type of microorganisms grown under identical conditions.     

Lipid characteristics of a seep clam,Mesolinga soliditesta: Comparison with those of two coastal clams,Meretrix lamarckii and Ruditapes philippinarum

The lipids and fatty acids of two coastal clams, Meretrix lamarckii and Ruditapes philippinarum, collected at 5 and 1 m of depth, and a seep clam, Mesolinga soliditesta, collected at 331 m of depth, were examined to assess their lipid physiology and trophic relationship with their diets. The major fatty acids of lipids in Mer. lamarckii and R. philippinarum were 14:0, 16:0, 18:0, 16:1n-7, 18:1n-9, 18:1n-7, 20:4n-6, 20:5n-3, and 22:6n-3, while those of Mes. soliditesta were 16:0, 18:0, 16:1n-7, 18:1n-7, 20:1n-7, 20:1n-13, 20:2n-7, 15 (Δ5,13-20:2), and 22:2n-7,15 (Δ7,15-22:2). The major polyunsaturated fatty acids (PUFAs) in the Mer. lamarckii and R. philippinarum lipids consisted of various n-3 and n-6 long-chain (LC) PUFAs, such as 20:4n-6, 22:4n-6, 20:5n-3, 22:5n-3, and 22:6n-3, while those in Mes. soliditesta muscle and viscera included various n-4 family PUFAs (18:3n-7, 18:4n-4, 20:2n-7, and 20:3n-7) with limited kinds of n-3 and n-6 PUFAs (20:4n-6 and 20:5n-3). These findings indicate that, like other common shallow-water clams, Mer. lamarckii and R. philippinarum ingest phytoplanktonic n-3 and n-6 LC-PUFAs, whereas Mes. soliditesta utilizes limited kinds of n-3 and n-6 LC-PUFAs. In contrast to the other two bivalves species, Mes. soliditesta yielded various n-4 and n-7 (n-4/n-7) PUFAs, which were assimilated from the chemosynthetic symbionts. The high diversity of PUFAs contained in the Mes. soliditesta lipids (n-3, n-4 family, and n-6 PUFAs) suggests that this species mixotrophically utilized both photosynthetic products and vent chemosynthetic nutrition derived from geothermal energy.     

Geochemistry and charge history of oils from the Yuqi area of Tarim Basin,NW China

The geochemistry, origin and charge history of oils from the Yuqi area of Tarim Basin have been investigated, through GC, GC-MS and fluid inclusion microthermometry analysis. The Yuqi oils accumulated mainly in three intervals: (1) in the Lower-Middle Ordovician Yingshan Formation (O_1-2y) carbonate reservoirs; (2) in the overlying Upper Triassic Halahatang Formation (T₃h); and (3) in the Lower Cretaceous Yageliemu Formation (K₁y) sandstones. Oils from different reservoirs have distinct physical properties, varying from extra-heavy (O_1-2y), heavy (T₃h), to light oils (T₃h and K₁y). However, their geochemical compositions show a high degree of similarity, which indicates that they derive from the same source rock. Abundant tricyclic terpanes, gammacerane, dibenzothiophene and C₂₁C₂₂steranes, together with a low level of diasteranes, indicate an anoxic marine source rock for oils in the Yuqi area. Oil-oil correlation shows that Yuqi oils derive from the same source bed as Tahe oils. The co-occurrence of intact n-alkanes and 25-norhopanes in all the samples supports the proposition that there is a mixture of an early filled severely biodegraded oil and a late filled fresh oil.In this study, charge history is examined on the basis of integration of fluid inclusion homogenization temperature data with 1D burial-thermal history models. Two episodes of oil charging are identified in the O_1-2y reservoir (well YQX1-1) at around 436-420 Ma (Middle-Late Silurian) and 10-3 Ma (Miocene to Pliocene), respectively. For the samples from the T₃h and K₁y intervals, only one episode of oil charge is indicated by the homogenization temperatures of coexisting aqueous inclusions with an inferred timing around 10-3 Ma. The T₃h heavy oil reservoir is assumed to be a secondary hydrocarbon pool, which accumulated by re-migration and re-distribution of hydrocarbons from O_1-2y hydrocarbon pools. The few early biodegraded oils in the K₁y light oils were probably picked up along the migration pathway during the late fresh oil charging.     

Fatty acids dynamics during embryonic development in genus Uca (Brachyura: Ocypodidae), from the mangroves of Inhaca Island,Mozambique

Variations in egg volume and fatty acid (FA) content through embryogenesis were evaluated in Uca species from Inhaca island, Mozambique. Egg volume increased 96.1%, 93.3%, 84.2%, 92.9%, 96.3%, respectively, in Uca annulipes, Uca inversa, Uca urvillei, Uca chlorophthalmus and Uca vocans (p < 0.05). Fatty acid content decreased through embryogenesis, showing its importance as fuel during embryonic development. Major fatty acids were 16:0, 18:0, 16:1n-7, 18:1n-9, 18:1n-7, 18:2n-6, 20:5n-3 and 20:4n-3. Unsaturated fatty acids (UFA) and saturated fatty acids (SFA) were used up at a similar rate for U. annulipes and U. inversa contrarily to the other three species. Within the UFA, MUFA were more consumed than PUFA for all species except U. chlorophthalmus. The high values detected for fatty acid trophic markers (essential C₁₈ and C₂₀ PUFAs) and odd-numbered fatty acid suggest that Uca species occupy medium trophic level, primarily omnivores and scavengers/detritivores consuming algae common in the intertidal habitats. The fatty acid consumption pattern during embryonic development was essentially similar between species with some variation as expected, as FA content varies within species mainly due to female feeding ecology, nutritional and physiological conditions, differential demands on resource allocation and geographic and seasonal variations in embryonic development.