黄河三角洲滨海湿地不同盐分质量浓度下土壤微生物死亡残体的差异

利用微生物生物标识物（氨基糖）,探讨盐分对黄河三角洲滨海湿地土壤微生物残体以及微生物残体对土壤有机碳（SOC）库贡献的影响。在滨海湿地生态系统中,随着土壤盐分增加,微生物死亡残体及其对SOC的贡献显著降低,表明高盐滨海湿地不利于土壤微生物死亡残体的积累及其对SOC的贡献。增加的盐分降低了土壤真菌死亡残体与细菌死亡残体的比值。线性回归分析指出土壤含水量、SOC、总氮（N）、交换性钙离子以及真菌死亡残体/细菌死亡残体与微生物死亡残体对SOC的贡献显著正相关。在低盐滨海湿地,良好的土壤条件（如高的水分、SOC和N）通过增加微生物死亡残体的积累和稳定性,促进了SOC的存储;而在高盐滨海湿地,低的可利用碳抑制了微生物死亡残体对SOC的贡献。另外,从低盐到高盐滨海湿地,真菌死亡残体对SOC的贡献逐渐下降,而细菌死亡残体对SOC的贡献没有变化,表明真菌死亡残体的积累对SOC的存储具有较大的影响。     

Simulations of accidental coal immersion

Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups – a laboratory seawater canal called “polludrome” is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L⁻¹), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 μg L⁻¹. Fortunately, the results show that the environmental impact of this type of accident would remain limited.     

Fluxes and seasonal changes in composition of organic matter in the English Channel

Dissolved and particulate organic matter (DOM and POM) have been investigated along a transect between Cherbourg and the Isle of Wight. In addition, the relative contribution of different sources of POM have been assessed by the use of lipid biomarkers (e.g. fatty acids). Seawater samples were collected at two depths (subsurface and above the bottom) at five stations located on the transect during five cruises (from September 1994 to July 1995). Particulate organic carbon (POC) and dissolved organic carbon (DOC) concentrations vary between 30–530 μg l⁻¹ and 0.5–2.7 mg l⁻¹, respectively, for all the cruises. Fluxes of POM and DOM have been estimated at 0.6×10¹² g yr⁻¹ and 6.5×10¹² g yr⁻¹ of carbon, respectively. General fluxes of water and therefore of DOC and POC are oriented eastward. However, around the Isle of Wight a westward oriented flux exists due to a gyre located in the area. The major DOC and POC fluxes occur in the central part of the Channel where the water column is deepest. Seasonal variations of different sources of POM (algal, bacterial and terrigenous) have been examined for the five cruises. The fresh algal organic fraction is relatively important in September in coastal waters with a predominance of diatom species on the English side, whereas it has a low or undetectable contribution during winter months. The bacterial fraction generally varies in concert with the algal component. It is low during the winter period and more important in bloom or post-bloom conditions, as for example in May. Terrestrial organic matter is restricted to coastal areas in September, and is present at low levels in May and July. Nevertheless, in November and February, terrigenous inputs have been clearly identified for the whole transect even in central waters.     

Simultaneous analyses and applications of multiple fluorobenzoate and halide tracers in hydrologic studies

An analytical method that employs ion chromatography has been developed to exploit the use of fluorobenzoic acids (FBAs) and halides more fully as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g. nitrate and sulphate). The usefulness of this analytical method is demonstrated in both field and laboratory tracer experiments. The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the USA—mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need—reveal several insights about tracer transport behaviour: (1) bromide and FBAs are not always transported conservatively; (2) the delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy; (3) use of iodine as a hydrologic tracer should take into account the different sorption behaviours of iodide and iodate and the possible conversion of iodine's initial chemical form; (4) the transport behaviour of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large‐scale field tracer experiments. Copyright © 2005 John Wiley & Sons, Ltd.     

The effects of Martian near surface conditions on the photochemistry of amino acids

In order to understand the complex multi-parameter system of destruction of organic material on the surface of Mars, step-by-step laboratory simulations of processes occurring on the surface of Mars are necessary. This paper describes the measured effects of two parameters, a CO₂ atmosphere and low temperature, on the destruction rate of amino acids when irradiated with Mars-like ultraviolet light (UV). The results show that the presence of a 7 mbar CO₂ atmosphere does not affect the destruction rate of glycine, and that cooling the sample to 210 K (average Mars temperature) lowers the destruction rate by a factor of 7. The decrease in the destruction rate of glycine by cooling the sample is thought to be predominantly caused by the slower reaction kinetics. When these results are scaled to Martian lighting conditions, cold thin films of glycine are assumed to have half-lives of 250 h under noontime peak illumination. It has been hypothesised that the absence of detectable native organic material in the Martian regolith points to the presence of oxidising agents. Some of these agents might form via the interaction of UV with compounds in the atmosphere. Water, although a trace component of Mars’ atmosphere, is suggested to be a significant source of oxidising species. However, gaseous CO₂ or adsorbed H₂O layers do not influence the photodestruction of amino acids significantly in the absence of reactive soil. Other mechanisms such as chemical processes in the Martian regolith need to be effective for rapid organic destruction.     

Chemical characterization of humic substances isolated from mangrove swamp sediments: The Qinglan area of Hainan Island,China

In order to improve the understanding of structural and reactive features of sediment organic matter from mangrove swamp as well as evaluate the relationship between such features and the impact from different sources (marine and terrestrial), humic and fulvic acids were isolated from two mangrove swamp sediments located in the Qinglan harbors on Hainan Island, China. One is a forest surface sediment site (WWM2), and the other is an estuary subaqueous sediment site (BMW). The humic and fulvic acids were characterized and compared using chemical and spectroscopic methods, including elemental analysis, thermogravimetric analysis (TGA), Fourier Transformed Infrared Spectroscopy (FTIR), ¹³C nuclear magnetic resonance (¹³C NMR) and potentiometric titrations. The results indicated that there were less aliphatic compounds but more aromatic compounds and oxygen-containing functional groups in fulvic acids. Humic acids contained more long-chain hydrocarbons and nitrogen compounds. Comparison of the C/N ratios and δ¹³C values for the humic substances at both sites indicated a larger marine and/or microbial contribution to the BMW site. Humic substances at the WWM2 site have more acidic functional groups than those of the BMW site. Compared to the literature, more phenolic groups existed in the samples of both sites, which may be due to the autochthonous contribution of mangrove plants.     

Seasonal biochemical changes in composition of body wall tissues of sea cucumber Apostichopus japonicus

Seasonal variation in proximate,amino acid and fatty acid composition of the body wall of sea cucumber Apostichopus japonicus was evaluated.The proximate composition,except for ash content,changed significantly among seasons(P,0.05).Alanine,glycine,glutamic acid and asparagic acid were the most abundant amino acids.Total amino acid and essential amino acid contents both varied clearly with seasons(P,0.05).16:0 and 16:1n7 were the primary saturated fatty acid(SFA) and monounsaturated fatty acid(MUFA) respect...     

Abundance and distribution of fatty acids within the walls of an active deep-sea sulfide chimney

Abundance and distribution of total fatty acids (TFAs) were examined along the physicochemical gradient within an active hydrothermal chimney collected from the Main Endeavour segment of Juan de Fuca Ridge. Approximately 27 fatty acids are identified with a chain-length ranging from C12 to C22. From the exterior to the interior of the chimney walls, the total concentrations of TFAs (∑ TFAs) show a trend of evident decrease. The observed compositions of TFAs are rich in bacterial biomarkers especially monounsaturated fatty acids (MUFAs) and minor branched and cyclopropyl FAs. On the basis of the species-specific FAs and bacterial 16SrRNA gene analysis (Li et al., unpublished data), sulfur-based metabolism appears to be the essential metabolic process in the chimney. Furthermore, the sulfur oxidizing bacteria (SOB) are identified as a basic component of microbial communities at the exterior of the hydrothermal chimney, and its proportion shows an inward decrease while the sulfate reducing bacteria (SRB) have an inverse distribution.     

硅限制对三角褐指藻叶绿素a、叶黄素含量和脂肪酸组成的影响

为研究硅限制对三角褐指藻脂肪酸组成的影响,用不含硅的f/2人工海水培养基对处于生长指数末期的三角褐指藻进行了0、6、12、24、48h的硅限制并测定了其叶绿素a、叶黄素含量和脂肪酸组成。结果表明,硅限制对三角褐指藻叶绿素a和叶黄素含量无影响,对脂肪酸组成影响显著。硅限制显著增加了C14∶0、C16∶0、C16∶1、C16∶2、C20∶5(EPA)百分含量,但各脂肪酸响应硅限制的时间不同。C14∶0在硅限制24、48h显著增加,分别是对照组的1.33倍、1.41倍。C16∶0在硅限制6、48h显著增加,分别是对照组的1.12倍、1.19倍;C16∶1在硅限制48h显著增加,是对照组的1.16倍;C16∶2在硅限制24h显著高于对照组,是对照组的1.27倍;EPA在硅限制24h百分含量达到最大值21.86%,分别是0h和对照组的1.11倍、1.18倍。研究结果表明,一定时间的硅限制能显著提高三角褐指藻EPA百分含量,以期为工业化生产EPA提供理论参考。     

Trophic ecology of the sea urchin Spatangus purpureus elucidated from gonad fatty acids composition analysis

Irregular sea urchins such as the spatangoid Spatangus purpureus are important bioturbators that contribute to natural biogenic disturbance and the functioning of biogeochemical cycles in soft sediments. In the coastal waters of the Balearic Islands S. purpureus occurs in soft red algal beds, and can reach high densities. The diet of S. purpureus is unknown and it is particularly difficult to analyze the stomach contents of this group; therefore, we analyzed the fatty acid (FA) composition of the gonads and potential food resources in order to assess the trophic relationships of this species. The FA profiles of the gonads of S. purpureus agree well with the FA composition of the potential trophic resources (algae and sediment) and reveals changes between localities with different available resources. Three polyunsaturated FAs mainly contributes in the composition in the S. purpureus gonads: eicosapentaenoic acid (C20:5n-3) and arachidonic acid (C20:4n-6), both abundant in the macroalgal material, and palmitoleic acid (C16:1n-7), which is characteristic of sediment samples. Trophic markers of bacterial input and carnivorous feeding were significantly more abundant in sea urchins caught on bottoms with less vegetation. The current study demonstrates that the FA content of S. purpureus gonads is a useful marker of diet, as differences in the profiles reflected the variations in detritus composition. The results of this study show that this species has omnivorous feeding behavior; however, viewed in conjunction with available abundance data the results suggest that phytodetritus found within algal beds is an important carbon source for this species.