A novel sub-nanomolar Mn(II) determination method is reported, which integrates sequential injection analysis (SIA), chemiluminescence (CL) detection, and a nitrilotriacetic acid (NTA) resin column. Using the SIA technique reduces the consumption of reagents and samples to only 600 and 100 mu L per analysis, respectively. Incorporating an NTA resin column eliminates the need for pH adjustment during the measurement process. Under optimized conditions, the detection limit of 0.17 nmol L-1 and a linear calibration between CL intensity and Mn(II) concentrations (0-100 nmol L-1) was achieved. This method was applied to the certified seawater reference material NASS-7 and real seawater samples.

Seafloor hydrothermal venting may be an important source of marine Cu and affect the biogeochemical cycling of Cu in the oceans. The distribution of Cu and its isotope compositions (delta Cu-65) can provide insight into seafloor hydrothermal processes and their role in the mass balance of global Cu. To date, there are no published Cu isotope data for hydrothermal plumes and very few reports on Cu concentration distributions. This study presents both Cu concentrations and dissolved Cu isotope (delta Cu-65) in hydrothermal plumes from back-arc volcanoes in the Northeast Lau Basin. The dissolved Cu (dCu) concentrations range from 2.14 to 5.66 nM most of which are higher than the deep seawater concentrations. However, the concentrations for some plume samples were lower than the deep seawater dCu concentrations due to adsorption onto particles in the plumes. The delta Cu-65 of hydrothermal plumes vary from 0.25 to 1.05 parts per thousand. As plumes dispersed, the Cu isotopes from high-temperature Mata Fitu and Mata Ua vents shifted towards light values. In contrast, the delta Cu-65 in plumes from low-temperature East Mata and West Mata vents show increasingly higher values with plume dispersal. Rayleigh distillation models are built based on the adsorption of dCu onto Fe particles and complexation with organic ligands to describe the dCu isotope evolution in hydrothermal plumes. The results suggest that the adsorption and organic complexation may be the likely explanations for the observed dCu isotope compositions in plumes from high- and low-temperature venting, separately, besides the mixing with background seawater. Our measured delta Cu-65 in three fluid samples (0.08, 0.09 and 0.20 parts per thousand) are lower than that of the characterized sinks (similar to 0.3 parts per thousand) in the oceans, indicating that hydrothermal fluids might be a source of light Cu isotopes. However, the delta Cu-65 (0.53 parts per thousand on average) in plume samples are higher than 0.3 parts per thousand and these seafloor hydrothermal plumes do not seem to be a source of light Cu isotope of dCu, at least near the venting sites. Our study first reveals the Cu isotope compositions and evolution in hydrothermal plumes and provides new hints about the impact of seafloor hydrothermal venting on the modern oceanic Cu isotope budget.

The ultraviolet absorption spectra of chromophoric dissolved organic matter (CDOM) can be used to trace its sources and to explore the dynamic of the CDOM pool. In previous studies, only the spectra above 240 nm can be used directly to characterize the CDOM in seawater, due to the overlapping of CDOM absorption spectra below 240 nm with inorganic chemicals such as NO3− , NO2− , Cl - and Br - . In this study, three different machine learning models, back propagation neural network (BPNN), random forest (RF) and extreme gradient boosting (XGBoost), were built to predict the CDOM ultraviolet absorption spectra between 215 and 350 nm after being trained with the raw absorption spectra of seawater. The optimal input wavelength range of the raw seawater spectra is 250-350 nm, and the optimal model parameters of machine learning algorithms were determined by using five-fold cross validation. The results show that the three models can well predict the CDOM absorption spectra. Comparatively, the XGBoost model gave the best prediction results. The reasons might be related to the fact that the XGBoost algorithm focuses on the residuals generated by the last iteration, which can reduce both variance and bias, especially for datasets with small sample sizes. Based on the predicted spectra by XGBoost algorithm, we calculated the spectra slopes of short wavelengths between 215 and 240 nm (S 215-240 ) and between 215 and 275 nm (S 215-275 ). The results show that the S 215-240 and S 215-275 are ~2 times the widely used spectra slopes between 275 and 295 nm (S 275-295 ) obtained by traditional method based on the raw spectra. Moreover, the S 215-240 and S 215-275 are more relavant with salinity for marine CDOM than S 275-295 , suggesting spectra slopes of shorter wavelengths might be the better proxies for marine CDOM than that of longer wavelengths.

Deep-sea hydrothermal venting is an important source of dissolved iron (dFe) to the oceans. Fe isotopes can be used as a potential tool to trace the dispersal of hydrothermal plumes. However, Fe isotope fractionation and its relation with Fe speciation as hydrothermal plumes disperse is still poorly constrained. In this study, we determined the Fe speciation and total and dissolved Fe isotope composition (delta 56tFe, delta 56dFe) for several hydrothermal plumes from backarc volcanoes in the Northeast Lau Basin. This combined approach provides important insights into the evolution of Fe isotopes in hydrothermal plumes. The results suggest delta(56)tFe variation in plumes is related to the loss of particulate Fe-sulfides or Fe-oxyhydroxides (FeOOH), both of which are dependant on the H2S concentrations and Fe/H2S in the source hydrothermal fluids. delta(56)dFe compositions in the hydrothermal plumes increase during plume dispersal/dilution and can be as high as 0.85 parts per thousand, demonstrating that hydrothermal plumes can export dissolved Fe with a significantly heavier delta(56)dFe than hydrothermal fluids. The reasons may be ascribed to the organic Fe complexes (FeL) and colloidal FeOOH in the dissolved phase. Another interpretation might be associated with the low pH in volcanic arc hydrothermal systems rich in magmatic CO2 and SO2, which decreases the Fe(II) oxidation rate. Further, we demonstrate for the first time that the delta(56)dFe is positively correlated with the conditional stability constants of FeL (logK'(FeL)). A Rayleigh distillation model is presented based on the mass balance of the determined FeL, and colloidal FeOOH in hydrothermal plumes, which can explain the observed Fe isotope compositions in hydrothermal plumes. Our data show how Fe isotopes are transformed within a hydrothermal plume above arc volcanoes and how these may differ from that of the original vent fluids. It adds to our understanding of the processes that have an impact on the Fe speciation and isotope composition in deep-sea hydrothermal plumes.(c) 2022 Elsevier Ltd. All rights reserved.

We investigated the speciation of Fe and distributions of Fe-binding ligands in the hydrothermal plumes over highand low-temperature vents and over diffuse venting fields above the Mariana back-arc spreading center. The concentrations of ligands ([L]) and conditional stability constants (K'FeL) of the natural Fe ligand pool were measured by a reverse titration-competitive ligand exchange-adsorption cathodic stripping voltammetry (RT-CLE-ACSV). The results showed that the buoyant and non-buoyant plume samples over the low-temperature Burke had the highest dissolved Fe/total Fe (DFe/TFe) of 82.2 + 8.8% and labile Fe/total Fe (Fe-Lab/TFe) of 43.3 + 5.6%. In contrast, in the plume samples above the high-temperature Perseverance field, TFe had the lowest proportions of DFe (48.8 +/- 12.2%) and Fe-Lab (19.4 +/- 8.8%). The linear relationships between Fe species and total Mn (TMn) in the buoyant plume over Burke suggest a simple conservative mixing with ambient seawater, which resulted in constant values of DFe/TFe. However, in the non-buoyant plume over Burke, DFe/TFe decreased with plume dilution. The plume samples sourced from the diffuse flow over newly erupted lava had the highest proportion of DFe present as Fe-Lab (74.6 +/- 4.0%). The [L] in the buoyant plumes over low-temperature Burke vent were up to 113.6 nM, and the logK'FeL decreased with increasing DFe and [L], suggesting the importance of weaker ligands in stabilizing Fe. For all the plume samples, the organically complexed Fe (FeL) constituted significant proportions of the DFe (29.0 +/- 9.3%) and Fe-Lab (57.5 +/- 15.6%) fractions. These Fe-binding ligands were likely sourced from diffuse venting fluids adjacent to the venting sites, and may be also produced by microbes within the hydrothermal plumes. (c) 2020 Elsevier Ltd. All rights reserved.

A direct, reagent-free, ultraviolet spectroscopic method for the simultaneous determination of nitrate (NO3−), nitrite (NO2−), and salinity in seawater is presented. The method is based on measuring the absorption spectra of the raw seawater range of 200–300 nm, combined with partial least squares (PLS) regression for resolving the spectral overlapping of NO3−, NO2−, and sea salt (or salinity). The interference from chromophoric dissolved organic matter (CDOM) UV absorbance was reduced according to its exponential relationship between 275 and 295 nm. The results of the cross-validation of calibration and the prediction sets were used to select the number of factors (4 for NO3−, NO2−, and salinity) and to optimize the wavelength range (215–240 nm) with a 1 nm wavelength interval. The linear relationship between the predicted and the actual values of NO3−, NO2−, salinity, and the recovery of spiked water samples suggest that the proposed PLS model can be a valuable alternative method to the wet chemical methods. Due to its simplicity and fast response, the proposed PLS model can be used as an algorithm for building nitrate and nitrite sensors. The comparison study of PLS and a classic least squares (CLS) model shows both PLS and CLS can give satisfactory results for predicting NO3− and salinity. However, for NO2− in some samples, PLS is superior to CLS, which may be due to the interference from unknown substances not included in the CLS algorithm. The proposed method was applied to the analysis of NO3−, NO2−, and salinity in the Changjiang (Yangtze River) estuary water samples and the results are comparable with that determined by the colorimetric Griess assay.

The distribution and succession of microbial communities along the dispersion path of hydrothermal plumes has not been well investigated. In this study, we collected several types of samples from the Longqi hydrothermal field located on the Southwest Indian Ridge, including hydrothermal plumes at different stages of formation, a suite of water column samples across the non-buoyant hydrothermal plumes above this field, and a background seawater column approximately 350 km away from the hydrothermal field. Using CH4 concentration anomalies, three non-buoyant plume samples between 2,535 and 2,735 m were identified within the water column. Microbial community compositions within these plumes and background seawater samples were examined based on the 16S rRNA genes and revealed significant variations and successions in community composition between different portions of the hydrothermal plumes. Near the vent orifice, representing the initial stage of plume formation, microbial populations were characterized by abundant and diverse putative vent-associated communities including (hyper)thermophiles such as Aquificaceae and Hydrogenothermaceae within the phylum Aquificae, and some epsilonproteobacterial chemolithoautotrophs such as Sulfurovum, Sulfurimonas, and Caminibacter. By contrast, in the rising buoyant plumes and adjacent seawaters, most vent-associated microbial taxa were still present but made only minor contributions to community composition. Some microbial taxa that are common in seawater columns such as alphaproteobacterial Sphingomonadaceae and SAR11 clade, deltaproteobacterial SAR324 clade, and gammaproteobacterial Pseudomonas, together with Sulfurimonas and SUP05 clade, became predominant. Members within the Sulfurimonas and SUP05 clade flourished with considerable abundance in the non-buoyant plumes, although these plumes were mainly composed of alphaproteobacterial Rhodobacteraceae, gammaproteobacterial Alteromonadaceae and Saccharospirillaceae putatively derived from the surrounding ambient seawater. We also analyzed archaeal components in the initial discharge and rising buoyant plume stages, with both primarily consisting of thaumarchaeal Nitrosopumilales and euryarchaeal Marine Group II. Our results indicated that being characteristic microbial lineages within the hydrothermal plumes of the Southwest Indian Ridge, both Sulfurimonas and SUP05 clade display a common and abundant distribution across the plume path. However, out of these clades, Sulfurimonas is more abundant and widespread.

Site F, an active cold seep situated on the northeastern continental slope of the South China Sea (SCS), has not been systematically surveyed since its first discovery in 2007. Here we report the results of a ROV transect survey of this cold seep conducted in 2018, which mapped the distribution of the substrates and quantified epifauna along parallel dive tracks. The site, measuring 180 m x 180 m, is characterized by a central part of authigenic carbonate outcrops with crevices releasing gas bubbles, which support high densities of bathymodiolin mussels Gigantidas platifrons (up to 273 individuals m(-2)) and galatheid squat lobsters Shinkaia crosnieri (up to 300 individuals m(-2)). On more condensed carbonate crusts, G. platifrons and the munidopsid squat lobsters Munidopsis spp. are present at low densities. The outskirts of the site are dominated by soft sediment, with bacterial mats and sparsely distributed G. platifrons and their shells, as well as the vestimentiferan tubeworm Paraescarpia echinospica. Sampling in various locations of the cold seep yields 10 new records of epibenthic animals as determined by watching the captured videos, morphological analysis as well as sequencing the COI and 16S rRNA gene sequences. Stable isotope analysis showed that biogenic methane is the main carbon source for most of the macrobenthos in this community. Many of these SCS cold seep macrobenthos have been reported from hydrothermal vents of the Okinawa Trough, indicating high connectivity between the two chemosynthesis-based communities in the Western Pacific.

The distribution and composition of Fe in hydrothermal plumes are crucial for understanding the contribution of hydrothermal venting to the oceanic Fe inventory. In this study, we conduct the first complete investigation of the size fractions of Fe and Fe-binding ligands in the Longqi hydrothermal plumes on the Southwest Indian Ridge, combining the approaches of the size partitioning and reverse titration-competitive ligand exchange-adsorptive cathodic stripping voltammetry. Concentrations of all the Fe fractions were very high in the plume samples, and dissolved Fe (<0.2 mu m) constituted a significant portion (48.7 7.9%) of total Fe, which might be related to the existence of colloidal Fe oxyhydroxides and sulfides, as well as organic Fe complexes. Dissolved Fe consisted of colloidal Fe (10 kDa to 0.2 mu m, similar to 70.2%) and soluble Fe (<10 kDa, similar to 29.8%). Colloidal Fe mainly contained Fe oxyhydroxides and sulfides (86.4 6.2%), while most of the soluble Fe were organic Fe complexes (65.7 5.4%). Fe speciation analyses showed that dissolved ligand concentrations were high in the hydrothermal plumes but were significantly lower than the dissolved Fe concentrations. Inferring from previous studies in the Longqi hydrothermal field, the ligands were most likely derived from the diffuse flow adjacent to the hydrothermal vents. The conditional stability constants (logK(FeL)) of dissolved FeL (20.4 +/- 0.5) were slightly higher than those of soluble FeL (19.6 +/- 0.4), although they were not statistically different. Based on the ligands' size partitioning, the soluble ligands stabilized similar to 8.8 +/- 3.8% of the hydrothermal Fe, which is over 2 times that of the colloidal ligands, similar to 4.0 +/- 1.8%.

The Longqi hydrothermal field at 49.6°E on the Southwest Indian Ridge was the first active hydrothermal field found at a bare-rock ultra-slow spreading mid-ocean ridge. Here we report the chemistry of the hydrothermal fluids, for the first time, that were collected from the S zone and the M zone of the Longqi field by gas-tight isobaric samplers by the HOV “Jiaolong” diving cruise in January 2015. According to H2, CH4 and other chemical data of the vent fluid, we suggest that the basement rock at the Longqi field is dominantly mafic. This is consistent with the observation that the host rock of the active Longqi Hydrothermal field is dominated by extensively distributed basaltic rock. It was very interesting to detect simultaneously discharging brine and vapor caused by phase separation at vents DFF6, DFF20, and DFF5 respectively, in a distance of about 400m. Based on the end-member fluid chemistry and distance between the vents, we propose that there is a single fluid source at the Longqi field. The fluid branches while rising to the seafloor, and two of the branches reach S zone and M zone and phase separate at similar conditions of about 28–30.2MPa and 400.6–408.3°C before they discharge from the vents. The end-member fluid compositions of these vents are comparable with or within the range of variation of known global seafloor hydrothermal fluid chemical data from fast, intermediate and slow spreading ridges, which confirms that the spreading rate is not the key factor that directly controls hydrothermal fluid chemistry. The composition of basement rock, water-rock interaction and phase separation are the major factors that control the composition of the vent fluids in the Longqi field.

The impact of hydrothermal activity on wider ocean geochemistry and microbial ecology remains a topic of much interest. To explore whether hydrothermal microbial signatures are exported to surrounding marine sediments or if such organisms serve as an important source of sedimentary organic matter, we determined the distributions of glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in surficial normal marine sediments, metalliferous sediments and low-temperature hydrothermal deposits at newly discovered hydrothermal fields and adjacent areas at the Southwest Indian Ridge (SWIR). The GDGTs in those samples varied significantly, evidently representing a variable influence of the hydrothermal activity. GDGT compositions of surficial background sediments in SWIR were similar to those commonly observed in marine sediments, dominated by GDGTs associated with marine planktonic archaea and especially GDGT-0 and crenarchaeol. In contrast, the GDGTs of metalliferous sediments strongly impacted by hydrothermal activity and low -temperature hydrothermal deposits were markedly different, characterized by high relative abundances of isoprenoid GDGTs (iGDGTs) bearing multiple rings (yielding a higher ring index), low relative abundances of crenarchaeol, and the presence of glycerol monoalkyl glycerol tetraether lipids (GMGTs; so called `H-tetraethers') that were absent in the normal marine sediments. Sources for these hydrothermal-specific tetraether lipids likely include methanogens and anaerobic methanotrophic archaea (GDGT-0 and GDGT-1-3, respectively), Thermoprotei and Thermoplasmatales (elevated GDGT-3 and 4), and other thermophilic archaea including Methanobacteriales (GMGTs). Deposits influenced by low -temperature hydrothermal activity also contained higher abundances of branched GDGTs (brGDGTs) typically attributed to soil bacteria. The more distal metalliferous sediments influenced by the neutrally buoyant plume did not contain putative hydrothermal GDGTs, having the same GDGT distribution as the background sediments. This suggests that the neutrally buoyant plume has a limited potential to directly influence the organic matter inputs to surrounding sediments, due to a rapidly waning chemosynthetic microbial contribution relative to normal marine contributions as the plume dispersed and was diluted. (C) 2016 Elsevier Ltd. All rights reserved.

A robust, simple and efficient gas chromatography (GC) method is presented for determining H-2 and CH4 concentrations simultaneously in water samples. The GC system consists of one detector (pulsed discharge helium ionization detectorPDHID), two columns in two ovens, respectively, and two 2-position-6-port purge valves. In this method, H-2 and CH4 in water samples were first extracted into the headspace of syringes, then injected into the GC system. Both H-2 and CH4 were detected by a PDHID. The separation of CH4 from O-2 and N-2 in seawater is achieved by switching the O-2 and N-2 out of the carrier gas flow at the appropriate time window. H-2 and CH4 concentrations in water samples collected from hydrothermal plumes at the Southwest Indian Ridge were determined successfully using this method.

回顾了近10年来完整极性脂质化合物(IPLs)在海洋微生物研究中的应用及存在的问题,并展望了IPLs应用的发展前景.作为新的热点之一,对海洋水体悬浮颗粒物中IPLs的研究,不仅推进了人们对水柱中IPLs分布和转化的了解,同时也深化了对古环境指标TEX86适用性的认识,有助于更好地开展古环境重建研究.色谱和质谱技术的发展,新型化合物的发现以及IPLs单体碳同位素分析的应用,使得IPLs在示踪海洋环境中真核生物与微生物共生作用、微生物介导的好氧和厌氧氨氧化以及甲烷厌氧氧化作用、微生物的代谢状态等方面也取得了重要研究进展.需要注意的是,由于不同的IPLs降解速率并不一致,其中部分古菌糖脂的降解周期可能远大于微生物群落的更新周期,因此可能并不适于表征活体生物量;同时,环境中氧气含量及有机质浓度也会对IPLs的降解速率造成影响;另外,在微生物不同的生长阶段,或者微生物由于生长环境条件变化产生生理响应时,IPLs组成也可能会发生变化.因此,应用IPLs指示微生物活动和反演古环境时应注意指标的适用性.

溶解态的锰和铁是海洋中重要的生物营养元素,也是探查海底热液活动及其演化的重要示踪剂.由于海底热液活动研究的迫切需求,以及AUV,ROV和HOV等水下运载支撑平台的迅速发展,20世纪80年代以来深海溶解态锰铁原位分析技术得到了快速发展.早期研发的Scanner和SUAVE,可对热液羽流中高含量的锰铁元素实现联合测定,但存在元素之间相互干扰等问题,因此针对锰、铁元素单独测量的原位分析仪应运而生.锰原位分析仪中,ZAPS虽然具有较低的检测限,但是无法在深海高压环境下进行原位校正；GAMOS系列具有原位校正功能,且能耗较低,可长期运行,但是检测限偏高,因此只能应用于热液环境中含量相对高的锰监测.铁原位分析仪中,改进的ALCHIMIST可实现热液喷口异常高含量铁和正常海域水体中低含量铁的检测,但由于能耗较高而难以应用于长期观测中；低能耗的Fe-Osmo-Analyzer和CHEMINI则在长期运行方面有着明显的优势.随着AUV/ROV/HOV等水下移动平台应用的日渐广泛以及海底观测网技术的迅速发展,发展原位分析仪进行长期的自主观测将成为一种必然趋势.

A simple and precise method was established for determination of iron complexation in lake water by cathodic stripping voltammetry(CSV) with ligand competition using the iron binding ligand 2-(2-thiazolylazo)-p-cresol(TAC).The sensitivity was improved by employing a fast(10.0 V/s) linear sweep scan waveform on a static mercury drop electrode.The optimized conditions to determine dissolved iron、iron complexation and total iron in lake water by CSV using TAC entails a TAC concentration of 10 μmol/L,a solution pH of 8.0 with 5 mmol/L 3-[4-(2-hydroxyethyl)-1-piperazinyl] propane sulfonic acid(EPPS) buffer,an adsorption potential of-0.4 V,and an adsorption time of 8 min.Under these optimized conditions the limit of detection was 0.08 nmol/L for Fe3+.The complex stability of iron complexation by TAC(Fe(TAC)2)was calibrated by ligand competition against EDTA giving a value of 260 for α,and 2.66×1012(mol/L)-2 for the conditional stability constant(β′).

Grain-size analysis is carried out for the 95surface sediment samples from the southwestern part of the South China Sea(3°56′~11°53′N,108°30′~113°47′E),where clayey silt and silty clay dominate,with sand and silty sand only occurred in the most southwestern shallow part.There shows a trend of decreasing grain-size,increasing sorting and decreasing skewness from the shallow water to deeper water.The Kriging method was employed to insert data of the grain-size parameters(mean grain-size,sorting coefficient and skewness),and then the trend analysis was carried out for the interpolated data using the GSTA program.It is revealed that the seabed topography plays a key role in the sediment transport.There is a topographic high in the area including the Guang-ya submarine plateau,the Nan-wei-tan plateau,and the Yong-shu-bei submarine plateau.To the north of the high,sediments from the western South China Sea continental shelf are transported into the Southwest Basin of South China Sea;to the south of the boundary,however,materials from the Sunda shelf and the Kalimantan Island are transported into the Nan-wei-xi and Bei-kang slope basin passing by the shelf break.The episodic sedimentary events,such as the turbidity current,also have significant impacts on the grain-size distribution pattern.The aggregation of the components8μm should not be ignored.Further researches are required for details.

The CDE hydrothermal field was first discovered during a Chinese cruise to the East Lau Basin Spreading Centre in 2007. Apart from significant amounts of loose Fe-Si-Mn (oxyhydr) oxide (referred to as oxide below) precipitates, a small Si-rich oxide chimney was also recovered on this cruise. In this study, we report on the mineralogical and geochemical analyses of this chimney and a model for its growth that has been developed. Based on the mineralogy and O isotope results, the chimney walls can be divided into four growth generations (layers) from the inner to the outer layers: amorphous opal and barite layer (precipitation temperature 68.5°C based on oxygen isotope determinations), a rod-like amorphous layer (precipitation temperature 39.6°C), a filamentous Fe-Si oxide layer, and an outer Fe-Mn oxide layer. Investigations based on SEM and EDS showed that neutrophilic Fe-oxidizing bacteria play an important role in the formation of this chimney, particularly in the outer two generations. In the first stage, the metabolic activity of the microbes results in the pervasive precipitation of the filamentous Fe-rich oxides inside a ring formed by some amorphous opal and barite; therefore, a loose porous layer forms. In the second stage, amorphous opal then precipitates inside this wall as a result of conductive cooling and gradually controls the mixing between the hydrothermal fluids and ambient seawaters. In the third stage, barite and some amorphous opal form from the higher temperature fluids at the summit of the chimney growth history. In the last stage, the chimney wall becomes thicker and denser and the exchange of hydrothermal fluids and seawater ceases. As a result, a Fe-Mn oxide layer precipitates onto the outer surface of the chimney wall as neutrophilic Fe-oxidizing bacteria reoccupy the surface of the chimney. This mineral sequence and the resultant growth generations are confirmed by the chemical characteristics of the chimney wall. Sr isotopes extracted from the Fe oxides of the four-generation wall generally show a decreasing trend of the 87Sr/86Sr ratios from the second layer to the inner layer (from 0.707008 to 0.705877) except for the outer layer (0.706502). The Sr isotope and chondrite normalized REE patterns of the corresponding bulk samples from the chimney wall also display a similar trend. Our study shows that the biogenic filament network plays a key role in the formation of the chimney in contrast to previous growth models of higher temperature chimneys, which often ignore the influence of biogenic factors.

The Southwest Indian Ridge (SWIR) is one of the world's slowest spreading ridges with a full spreading rate of ~ 14 mm a− 1. Due to its low thermal budget, high-temperature hydrothermal activity along the SWIR was once considered to be impossible. The Chinese cruise DY115-19 on board R/V Dayang Yihao successfully discovered the first SWIR active hydrothermal field at 37°47′S 49°39′E, located at a magmatically robust spreading segment. Here, the geochemical characteristics of hydrothermal plumes from the hydrothermal field are first reported, and water column anomalies of light transmission, Fe, Mn, Al, both dissolved and particulate, are discussed. The total Fe and dissolved Mn concentrations in the plumes varied from 13.7 to 277.4 nM and 0.47 to 10.41 nM, respectively. The composition of Fe-Mn-Al implied that particles in the plumes were mainly hydrothermal in origin, also included small contributions of resuspended sediments or background particles. Dissolved Fe constituted a considerable fraction of the total Fe, more than 80% in plume samples from station CTD 4. High Fe concentrations might be sustained in the dissolved phase because of the existence of organic complexes and nanoparticles. On board incubation experiments verified the Fe(II) oxidation half-lives for plumes of CTD 4 and CTD 13 were 1.8 and 1.6 h, respectively, which are much longer than the calculated value of ~ 0.5 h based on the deep water pH and oxygen concentration.

蒙特利海湾研究所（Monterey Bay Aquarium Research Institute,MBARI）作为一家私营、非赢利性的研究机构,由于其独特的办所理念和运作机制,在短短20多年的时间里即跻身于世界海洋科学与技术的领先地位。MBARI最重要的基本原则是科学家和工程师之间的平等关系,MBARI所有的研究项目必须是卓越、创新并具前瞻性的。对MBARI发展历史、研究方向及部分研究成果进行了介绍,提出了几点对我国当前海洋科学与研究现状的思考和感受。

A two-dimensional gas chromatographic instrument was established by the capillary flow technology (Deans Switch) and two columns (PoraPLOT Q and Molsieve 5A) and three detectors (pulsed discharge helium ionization detector, flame photometric detector and thermal conductivity detector). The instrument can be used to measure tracer gases simultaneously including hydrogen, methane, carbon dioxide and hydrogen sulfide. The detection limits of the hydrogen, methane, carbon dioxide and hydrogen sulfide were 0.51, 0.17, 82 and 0.08 micromol/mol, and the calibration curves presented good linear relationships in the range of 2-1030, 0.6-501, 120-10500 and 0.2- 49.1 micromol/mol, respectively. The relative standard deviations were less than 10% for the measurements of ten standard gases. By this method, the tracer gases in the sediment pore water of gas hydrate area in South China Sea had been detected. This method is simple, sensitive, and suitable for on-board detection. Compared with the usual methods for measuring tracer gases, the amount of a sample necessary is reduced greatly. It is useful for the survey of gas hydrate and hydrothermal resources below sea floor and for the research of dissolved gases in the ocean.