Origin of light volatile hydrocarbon gases in mud volcano fluids, Gulf of Cadiz — Evidence for multiple sources and transport mechanisms in active sedimentary wedges

Widespread mud volcanism across the thick (≤ 14 km) seismically active sedimentary prism of the Gulf of Cadiz is driven by tectonic activity along extensive strike–slip faults and thrusts associated with the accommodation of the Africa–Eurasia convergence and building of the Arc of Gibraltar, respectively. An investigation of eleven active sites located on the Moroccan Margin and in deeper waters across the wedge showed that light volatile hydrocarbon gases vented at the mud volcanoes (MVs) have distinct, mainly thermogenic, origins. Gases of higher and lower thermal maturities are mixed at Ginsburg and Mercator MVs on the Moroccan Margin, probably because high maturity gases that are trapped beneath evaporite deposits are transported upwards at the MVs and mixed with shallower, less mature, thermogenic gases during migration. At all other sites except for the westernmost Porto MV, δ¹³C–CH₄ and δ²H–CH₄ values of ~ − 50‰ and − 200‰, respectively, suggest a common origin for methane; however, the ratio of CH₄/(C₂H₆ + C₃H₈) varies from ~ 10 to > 7000 between sites. Mixing of shallow biogenic and deep thermogenic gases cannot account for the observed compositions which instead result mainly from extensive migration of thermogenic gases in the deeply-buried sediments, possibly associated with biodegradation of C₂₊ homologues and secondary methane production at Captain Arutyunov and Carlos Ribeiro MVs. At the deep-water Bonjardim, Olenin and Carlos Ribeiro MVs, generation of C₂₊-enriched gases is probably promoted by high heat flux anomalies which have been measured in the western area of the wedge. At Porto MV, gases are highly enriched in CH₄ having δ¹³C–CH₄ ~ − 50‰, as at most sites, but markedly lower δ²H–CH₄ values < − 250‰, suggesting that it is not generated by thermal cracking of n-alkanes but rather that it has a deep Archaeal origin. The presence of petroleum-type hydrocarbons is consistent with a thermogenic origin, and at sites where CH₄ is predominant support the suggestion that gases have experienced extensive transport during which they mobilized oil from sediments ~ 2–4 km deep. These fluids then migrate into shallower, thermally immature muds, driving their mobilization and extrusion at the seafloor. At Porto MV, the limited presence of petroleum in mud breccia sediments further supports the hypothesis of a predominantly deep microbial origin of CH₄.     

Adaptation of the antioxidant defence system in hydrothermal-vent mussels (Bathymodiolus azoricus) transplanted between two Mid-Atlantic Ridge sites

The vent mussel Bathymodiolus azoricus is the dominant member of the Northern Mid‐Atlantic Ridge (MAR) hydrothermal megafauna, and lives in an environment characterized by temporal and spatial variations in the levels of heavy metals, methane and hydrogen sulphide, substances which are known to increase reactive oxygen species levels in the tissues of exposed organisms. To evaluate the effects of two contrasting hydrothermal environments on the antioxidant defence system of this vent mussel species, a 2‐week transplant experiment was carried out involving mussels collected from the relatively deep (2300 m), and chemical rich, Rainbow vent field. These were transplanted to the shallower (1700 m), and relatively less toxic, Lucky Strike vent field. To achieve this objective, levels of superoxide dismutase, catalase (CAT), total glutathione peroxidase (GPx), selenium‐dependent glutathione peroxidase and lipid peroxidation (LPO) were measured in the gills and mantle tissues of resident and transplant mussels before and after the transplant experiment. With the exception of CAT, the gills of the transplanted mussels had significantly higher antioxidant enzyme activity compared with the basal levels in the donor (Rainbow) and recipient (Lucky Strike) populations; whereas the antioxidant enzyme levels in the mantle tissues of the transplants reflected the baseline levels of activity in the native Lucky Strike mussels after 2 weeks. In contrast, LPO levels were significantly higher in both tissue types in the transplants than in either the source or the recipient populations, which suggested a response to hydrostatic pressure change (note, the transplant animals were brought to the surface for transportation between the two vent fields). The fact that the Rainbow mussels survived the transplant experience indicates that B. azoricus has a very robust constitution, which enables it to cope behaviourally, physiologically and genetically with the extreme conditions found in its naturally contaminated deep‐sea environment.     

外源脱落酸对低温胁迫下圆柏属植物幼苗生理特性的影响

以3 a生圆柏和祁连圆柏幼苗为材料, 采用不同浓度脱落酸(ABA)预处理两种圆柏属幼苗, 测定-4℃低温胁迫处理第9 d叶片相对含水量(RWC)、相对电导率(REC)、丙二醛(MDA)、可溶性糖(SS)、可溶性蛋白(SP)、脯氨酸(Pro)和类胡萝卜素(Car)含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸氧化酶(APX)和谷胱甘肽还原酶(GR)活性, 分析外源ABA对低温胁迫下圆柏属植物叶片膜脂过氧化和渗透调节物质的影响, 为培育较多品种的抗冷冻常绿植物提供理论依据. 结果表明: 低温胁迫下, 一定浓度的ABA预处理能有效保护幼苗叶片膜系统的稳定性、增加渗透调节物质含量和提高抗氧化酶活性, 其中30 mg·L^-1ABA预处理对提高圆柏抗寒性效果最好, 40 mg·L^-1ABA预处理对提高祁连圆柏抗寒性效果最好, 且在外源ABA预处理下, 祁连圆柏的抗寒性比圆柏的强. 因此, 施用适合浓度的ABA在提高圆柏属植物抗寒性方面具有较好的应用价值.     

Biogeochemistry of sterols in plankton, settling particles and recent sediments in a cold ocean ecosystem (Trinity Bay, Newfoundland)

In the context of a multidisciplinary study to determine current and past ecosystem health and the relative contributions of sources of organic matter (marine vs. terrestrial and natural vs. anthropogenic input), sterols were determined in plankton, settling particles and sediments from Trinity Bay, Newfoundland, a sub-polar Atlantic Ocean ecosystem. The centric diatoms Chaetoceros spp., Thalassiosira spp. and Leptocylindrus danicus were all prominent in the plankton samples, and centric diatoms predominated in the settling particles. Plankton samples contained 0.4±0.4 mg/g dw (1995) or 1.4±1.3 mg/g dw (1996) total sterols, with cholesta-5,24-dien-3β-ol (mean 26% of total sterols), cholest-5-en-3β-ol (24%) and cholesta-5,22(E)-dien-3β-ol (13%) chief among these, denoting diatom and zooplankton sources. In settling particles, the prominence of cholesta-5,24-dien-3β-ol (24%), cholest-5-en-3β-ol (24%), cholesta-5,22(E)-dien-3β-ol (13%) and 24-methylcholesta-5,22(E)-dien-3β-ol (9%) again suggested mainly marine sources. The sterol composition of plankton and settling particles from different sampling periods showed a high degree of consistency. Higher plant C₂₉ sterols (notably 24-ethylcholest-5-en-3β-ol, 9–26%) were prominent in sediments from both inshore and offshore sites. No decreasing trend in total or individual sterols was observed down the 30-cm sediment cores, suggesting good overall preservation. No 5β-stanols such as 5β-cholestan-3β-ol (coprostanol) were detected in offshore sediments, plankton or settling particles, with only low levels (5β-cholestan-3β-ol max. 4.4%, 5β-cholestan-3α-ol max. 5.1%) in certain inshore sediments. This suggests that raw sewage discharges in rural Newfoundland are being efficiently degraded or dispersed, or that inputs are highly localized. Source apportionation of organic matter in the sediment samples based on sterol composition was attempted. This highlighted the large terrestrial contribution to the sterols in marine sediments (up to 58% of sterols inshore, 24% offshore) and suggests either degradation or effective recycling of marine sterols.     

Application of pyrolysis–GC/MS for the characterisation of suspended particulate organic matter in the Mediterranean Sea: a comparison with the Black Sea

Suspended particulate organic matter (SPOM) both from the oligotrophic Mediterranean and from the more productive Black Sea has been analysed by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) and by such conventional techniques as elemental analysis and fluorometry. The data achieved by the two approaches generally confirmed and complemented each other. The relative concentrations of pyrolysis products (termed markers) characteristic of chlorophyll (CHL), lipid, carbohydrate (CBH), and protein (PROT) components of SPOM have been determined. The vertical distribution of lipid markers was more uniform in the Mediterranean surface waters. Their relative abundance increased rapidly in the oxycline of the Black Sea, reaching their highest levels in the suboxic zone, where the protein composition of the SPOM changed significantly. In both seas, the relative concentrations of CHL markers increased consistently within the CHL maximum zone where the CBH markers were less abundant. No lignin markers from terrestrial vegetation were detected at significant levels in the pyrograms.     

溶藻弧菌对三疣梭子蟹抗氧化酶系统的影响

从患乳化病的养殖三疣梭子蟹(Portunus trituberculatus)体组织内分离出痛原菌--溶藻弧菌(Vibrioalginglyticus),通过肌肉注射的方式对三疣梭子蟹进行感染实验,对照组注射等量的生理盐水,在感染后O、24、48和72 h分别采集不同处理组三疣梭子蟹的血淋巴、肌肉和肝胰腺组织,测定溶藻弧菌对其各组织抗氧化相关酶活的影响.结果表明:注射生理盐水的对照组三疣梭子蟹体组织中抗氧化酶和MDA含量在不同的采样时间变化不显著(P>0.05).与对照组比较,三疣梭子蟹感染溶藻弧菌后血淋巴、肌肉和肝胰腺组织中SOD活性随着感染时间的延长显著降低(P<0.05).在感染溶藻弧菌24 h时血淋巴和肝胰腺组织中GSH-px活性有增强的趋势(P>0.05),随后在感染48 h后GSH-px活性显著降低(P<0.05);感染组各体组织中的MDA含量均随着感染时间的延长而显著上升(P<0.05).结果显示梭子蟹感染溶藻弧菌后机体消除氧化过程自由基的抗氧化酶活降低,脂质过氧化物水平升高,使得抗氧化防御能力下降.     

多氯联苯(PCB1254)对栉孔扇贝消化盲囊和鳃丝抗氧化系统及脂质过氧化水平的影响

本实验研究了浓度梯度为0.5,1.0,和10.0μg/L的多氯联苯化舍物(PCB1254)处理30d栉孔扇贝消化盲囊和鳃丝SOD,CAT和GPx活性和脂质过氧化水平的变化.研究结果表明:低浓度组(0.5μg/L和1.0μg/L)的抗氧化酶活力能够被PCB1254显著的诱导,但是在高浓度组,抗氧化酶快速被诱导升高然后随着...     

岩藻聚糖硫酸酯体外抗氧化特性的研究

采用化学发光分析法研究岩藻聚糖硫酸酯清除超氧阴离子自由基 (O· -2 )及羟基自由基(· OH)的作用 ,并以高效液相色谱法研究对卵磷脂 (PC)过氧化的抑制能力。结果显示 :(1)三种岩藻聚糖硫酸酯组分均有清除活性氧自由基的能力 ,但清除超氧阴离子自由基的能力高于清除羟基自由基的能力。其中糖醛酸含量高和硫酸酯含量低的组分 清除自由基的能力最强 ,它对 O· -2 的IC50 为 0 .0 4 4 mg/m L,对· OH的 IC50 为 0 .0 6 2 mg/m L。 (2 )岩藻聚糖硫酯具有抑制 PC过氧化的能力。岩藻聚糖硫酸酯组分受活性氧损伤后 ,它们的抗氧化能力均降低。研究表明 ,岩藻聚糖硫酸酯具有较强的体外抗氧化的功能。     

Effects of water-borne copper on metallothionein and lipid peroxidation in the marine amphipod gammarus locusta

The aim of the current work was to determine over 10 days the effects of water-borne exposure of the marine amphipod Gammarus locusta to 4 μgCu l⁻¹ on the metallothionein (MT; measured by differential pulse polarography) protection system and lipid peroxidation (LP; thiobarbituric acid-reactive malondialdehyde equivalents) as a measure of oxidative damage. MT levels in exposed animals increased significantly at day 2 (36% > control; P<0.001) and remained high at days 6 and 10 (55 and 38%, respectively, P<0.001). The maximum level of MT at day 6 coincided with the highest Cu body-burden. LP increased within 1 day of exposure, indicative of Cu as an oxidative stressor. However, in contrast to MT, the highest LP level was seen at day 4 (68% > control, P<0.001) before returning to control values by day 6, indicating a protective role of MT against the pro-oxidant effects of Cu.