多通道化学传感器及其在热液喷口探测中的应用

热液喷口附近的羽状流中存在明显的化学及浊度异常，通过探测这些异常可判断是否存在热液喷口及确定喷口的具体位置。本文研制了一款可用于探测热液喷口的多通道化学传感器，该传感器具有体积小、精度高的特点，且可在4000米深海中进行工作。该化学传感器共配备五个全固态电极，一个为参比电极，其余四个为离子选择性电极，并且可根据所测量的化学离子进行更换。本文基于该化学传感器共进行了两组实验。在第一组浅海试验中，化学传感器集成了pH，Eh，CO₃^2-和SO₄^2-电极，在浅海海域中测量对应化学量，结果表明该化学传感器可在实际应用中获得高精度、稳定的测量数据。第二组实验为深海热液探测，装配了pH，Eh，CO₃^2-和H₂S电极的化学传感器在西南印度洋中脊区域的29次测线中投入使用，共获得有效数据27组。通过对测量所得到的化学量进行分析，本文提出了一种确定热液喷口的化学异常探测方法，若某时间段内Eh和H₂S的电势降低，而pH和CO₃^2-的电势上升则可判定存在化学异常。利用该方法对27组有效数据进行分析，共发现5个潜在的热液喷口。实验结果表明，该化学传感器可有效地探测由热液引起的化学异常，适用于实际热液探测中。     

Microbial Diversity of Deep-sea Sediments from Three Newly Discovered Hydrothermal Vent Fields in the Central Indian Ridge

Since the discovery of hydrothermal vents in the late 1970s, deep-sea hydrothermal vent fields have attracted great attention as biological hotspots. However, compared with other ocean ridges, the structure and function of microbial communities inhabiting vent fields in the Central Indian ridge (CIR) remain understudied. Here, we provide for the first time 16S rRNA gene-based comparative metagenomic analysis of the sediment-associated microbial communities from three newly discovered vent fields in the CIR. Sediment samples collected in the Invent B, Invent E and Onnuri vent fields varied in geochemical properties, elemental concentrations and associated microbial communities. Proteobacteria (Gammaproteobacteria) was the dominant phylum in Invent B and Onnuri vent fields. In contrast, Invent E mainly consisted of Chloroflexi and Euryarchaeota. Predicted functional profiling revealed that the microbial communities in the three vents are dominated by chemoheterotrophic functions. In addition, microbial communities capable of respiration of sulfur compounds, nitrification, nitrite oxidation, methylotrophy, and methanotropy were found to be the main chemolithoautotrophs. Compared to other vent fields, Invent E showed a predominance of archaeal methanogens suggesting it exhibits slightly different geochemistry. Multivariate analysis indicated that the biogeochemical and trace metal differences are reflected in the sediment microbial compositions of the three vent fields. This study expands our current understanding of the microbial community structure and potential ecological functions of the newly discovered hydrothermal vent fields in the CIR.

     

Spatial distribution, diversity and composition of bacterial communities in sub-seafloor fluids at a deep-sea hydrothermal field of the Suiyo Seamount

Spatial distribution, diversity, and composition of bacterial communities within the shallow sub-seafloor at the deep-sea hydrothermal field of the Suiyo Seamount, Izu-Bonin Arc, Western Pacific Ocean, were investigated. Fluids were sampled from four boreholes in this area. Each borehole was located near or away from active vents, the distance ranging 2–40 m from active vents. In addition, fluids discharging from a natural vent and ambient seawater were sampled in this area. We extracted DNA from each sample, amplified bacterial 16S rRNA genes by PCR, cloned the PCR products and sequenced. The total number of clones analyzed was 348. Most of the detected phylotypes were affiliated with the phylum Proteobacteria, of which the detection frequency in each clone library ranged from 84.6% to 100%. The bacterial community diversity and composition were different between hydrothermal fluids and seawater, between fluids from the boreholes and the vent, and even among fluids from each borehole. The relative abundances of the phylotypes related to Thiomicrospira, Methylobacterium and Sphingomonas were significantly different among fluids from each borehole. The phylotypes related to Thiomicrospira and Alcanivorax were detected in all of the boreholes and vent samples. Our findings provide insights into bacterial communities in the shallow sub-seafloor environments at active deep-sea hydrothermal vent fields.     

Use of voltammetric solid-state (micro)electrodes for studying biogeochemical processes: Laboratory measurements to real time measurements with an in situ electrochemical analyzer (ISEA)

Solid-state voltammetric (micro)electrodes have been used in a variety of environments to study biogeochemical processes. Here we show the wealth of information that has been obtained in the study of sediments, microbial mats, cultures and the water column including hydrothermal vents. Voltammetric analyzers have been developed to function with operator guidance and in unattended mode for temporal studies with an in situ electrochemical analyzer (ISEA). The electrodes can detect the presence (or absence) of a host of redox species and trace metals simultaneously. The multi-species capacity of the voltammetric electrode can be used to examine complex heterogeneous environments such as the root zone of salt marsh sediments. The data obtained with these systems clearly show that O₂ and Mn²⁺ profiles in marine sedimentary porewaters and in microbial biofilms on metal surfaces rarely overlap indicating that O₂ is not a direct oxidant for Mn²⁺. This lack of overlap was suggested originally by Joris Gieskes' group. In waters emanating from hydrothermal vents, Fe²⁺, H₂S and soluble molecular FeS clusters (FeS_aq) are detected indicating that the reactants for the pyrite formation reaction are H₂S and soluble molecular FeS clusters. Using the ISEA with electrodes at fixed positions, data collected continuously over three days near a Riftia pachyptila tubeworm field generally show that O₂ and H₂S anti-correlate and that H₂S and temperature generally correlate. Unlike sedimentary environments, the data clearly show that Riftia live in areas where both O₂ and H₂S co-exist so that its endosymbiont bacteria can perform chemosynthesis. However, physical mixing of diffuse flow vent waters with oceanic bottom waters above or to the side of the tubeworm field can dampen these correlations or even reverse them. Voltammetry is a powerful technique because it provides chemical speciation data (e.g.; oxidation state and different elemental compounds/ions) as well as quantitative data. Because (micro)organisms occupy environmental niches due to the system's chemistry, it is necessary to know chemical speciation. Voltammetric methods allow us to study how chemistry drives biology and how biology can affect chemistry for its own benefit.     

Geochemical features of heavy metal bioaccumulation in the Guaymas Basin of the Gulf of California

Atomic absorption spectroscopy (flame and graphite furnace techniques) and instrumental neutron activation analysis were used for determining the Fe, Mn, Zn, Cu, Pb, Cd, Ag, Co, Cr, As, Se, Sb, Ba, Au, and Hg contents in 25 samples of different tissues and whole organisms inhabiting the southern trough in the Guaymas Basin (Gulf of California) and in several samples of its bottom waters. It is shown that the habitat environment of this hydrothermal field with high primary production of both photosynthetic and bacterial chemosynthetic origin influences the Fe and Mn ratios in the waters of the microbiotopes and the distribution patterns of the metals in the external and internal organs of the benthic animals. In the dominant specialized taxa, the maximal bioaccumulation of metals is registered both in the organs related to bacterial chemosynthesis such as the trophosome of Vestimentifera Riftia pachyptila and the gills of the vesicomyid clam Archivestica gigas and in other organs. The other organisms such as the mollusks Nuculana grasslei, actinias Paraphelliactis pabista, Actinaria, and Spongia and the crabs Munidopsis alvisca demonstrate high bioaccumulation properties as well. The metal concentration coefficient is highly variable ranging from 10 to 10⁴. The changes in the molar Fe/Mn ratio values imply the partitioning of these two metals in the following migration succession: microbiotope water-external organs-internal organs.     

Spatial structures of hydrothermal vents and vent-associated megafauna in the back-arc basin system of the Okinawa Trough,western Pacific

Spatial patterns and morphology of hydrothermal vents and the occurrence of vent-associated megafauna were investigated in the back-arc basin system of the Okinawa Trough, western Pacific. Amongst hydrothermal vent fields located on the rising slopes to the NE and S of the basin, the Iheya North area has been subjected to a series of intensive diving surveys. Hydrothermal vents demonstrated concentrated patterns of distribution on different spatial scales. In Iheya North, the majority of vents occurred in lines parallel to the NE to W/SW alignment of the spreading axis, within a radius of ca. 200 m around the most active sulphide structure with the highest recorded fluid temperature of over 300°C. The morphology of hydrothermal vents varied greatly from an incipient flat rock with crevices to a 20- to 30-m-tall, multi-flanged structure with concomitant variation in the distribution and abundance of vent-associated megafauna, particularly a galatheid Shinkaia crosnieri and Bathymodiolus mussels. Comparison of active and inactive vents revealed that the spatial extent of Shinkaia ‘aggregation’ (a group of individuals with short nearest-neighbour distances) effectively defined a habitat unit of this species, and active hydrothermal chimneys contained more of these units, leading to greater spatial occupancy by Shinkaia. Given the temporally unstable nature of vent structures as recognised by repeated surveys, vent assemblages are thought to be closely dictated by the spatio-temporal dynamics of vents in the Okinawa Trough back-arc system.     

Experimental evidence of habitat provision by aggregations of Riftia pachyptila at hydrothermal vents on the East Pacific Rise

Habitat created or modified by the physical architecture of large or spatially dominant species plays an important role in structuring communities in a variety of terrestrial, aquatic, and marine habitats. At hydrothermal vents, the giant tubeworm Riftia pachyptila forms large and dense aggregations in a spatially and temporally variable environment. The density and diversity of smaller invertebrates is higher in association with aggregations of R. pachyptila than on the surrounding basalt rock seafloor. Artificial substrata designed to mimic R. pachyptila aggregations were deployed along a gradient of productivity to test the hypothesis that high local species diversity is maintained by the provision of complex physical structure in areas of diffuse hydrothermal flow. After 1 year, species assemblages were compared among artificial aggregations in low‐, intermediate‐, and high‐productivity zones and compared to natural aggregations of R. pachyptila from the same site. Hydrothermal vent fauna colonized every artificial aggregation, and both epifaunal density and species richness were highest in areas of high chemosynthetic primary production. The species richness was also similar between natural aggregations of R. pachyptila and artificial aggregations in intermediate‐ and high‐productivity zones, suggesting that complex physical structure alone can support local species diversity in areas of chemosynthetic primary production. Differences in the community composition between natural and artificial aggregations reflect the variability in microhabitat conditions and biological interactions associated with hydrothermal fluid flux at low‐temperature hydrothermal vents. Moreover, these local ecological factors may further contribute to the maintenance of regional species diversity in hydrothermal vent communities on the East Pacific Rise.     

Bottom fauna associated with <Emphasis Type="Italic">Bathymodiolus azoricus</Emphasis> (Mytilidae) mussel beds in the hydrothermal fields of the Mid-Atlantic Ridge

The structure of the assemblages associated with the mussel aggregations of Bathymodiolus azoricus was investigated. The mussel beds were found on the hydrothermal vent fields on the Mid-Atlantic Ridge (the Menez Gwen, Lucky Strike, and Rainbow areas) at the depths of 850–2400 m. The community structure of the mussel bed assemblages varied between the studied areas. Large number of species was unique to Menez Gwen mussel beds; the most observed taxa were not specialized hydrothermal species. All the other, nonunique species were found for the Lucky Strike region. The lowest mussel assemblage structure evenness was observed in the shallowest area, the Menez Gwen area (850 m depth). We assume that two types of mussel assemblages—nematode-dominated and copepod-dominated ones—exist in the Lucky Strike field. The assemblages of B. azoricus differ significantly from the assemblages of B. thermophilus inhabiting the Pacific hydrothermal vents.     

Ecological aspects of hydrothermal vent animals in captivity at atmospheric pressure

Hydrothermal vent animals were kept and displayed at atmospheric pressure with an artificial hydrothermal vent system in Enoshima Aquarium, Fujisawa, Kanagawa, Japan. The artificial hydrothermal vent system was composed of a main rearing tank, a heating tank, a hot water outlet with added Na₂S as the source of H₂S, and added CO₂ for chemosynthetic bacteria and pH regulation. When the need arises, a dissolved oxygen control unit and submersible heaters can be attached. We are now rearing hydrothermal vent crabs (Austinograea yunohana), hydrothermal vent galatheid crabs (Shinkaia crosnieri), vestimentiferan tubeworms (Lamellibrachia satsuma), hydrothermal vent shrimp (Opaepele spp.), hydrothermal vent barnacles (Ashinkailepas seepiophilia and Neoverruca sp.), and tonguefish (Symphurus sp.). In the artificial hydrothermal vent tank, shrimp and crabs have been observed to cluster close to the artificial hydrothermal vent. In particular, large (adult) crabs needed a heat source to live in the aquarium over a long term. Additionally, some species (A. yunohana, S. crosnieri, Opaepele sp. and Symphurus sp.) have spawned and hatched in captivity. It is likely higher water temperatures are needed for egg and larval development compared with temperatures for adult requirements.     

Influence of the hydrothermal vents on the distribution of benthic foraminifera from the Guaymas Basin,Mexico

The distribution and composition of four benthic foraminifera assemblages from the Guaymas Basin are depicted through Q- and R-mode Factor Analysis. One of these assemblages is distributed near hydrothermal vents,* another developed away from the influence of the vents, and the other two assemblages are found in the subbottom sediments.Biostratigraphic analysis of five cores collected within the hydrothermal region suggest that the foraminiferal remains have been affected by aselective dissolution process. Only small species, such asBulimina spinosa andBolivina sp 2, have been preserved in the subbottom sediments which have been influenced by the hydrothermal activity.     

Different thermal preferences for brooding and larval dispersal of two neighboring shrimps in deep‐sea hydrothermal vent fields

Temperature is an important factor affecting the distributions and life‐history traits of marine animals. Deep‐sea hydrothermal vents are suitable environments to examine ecologic differences related to temperature, due to the steep temperature gradients around the vents. Rearing experiments under various temperature conditions (5–30 °C) at atmospheric pressure demonstrated a difference in thermal effects on egg hatching and larva in two co‐occurring, vent‐associated alvinocaridid shrimps – the peripherally distributed Alvinocaris longirostris and the centrally distributed Shinkaicaris leurokolos. The duration before hatching became shorter as temperature increased, while the maximum hatching rate occurred at higher temperatures in S. leurokolos (10–20 °C) than in A. longirostris (10 °C). Hatched larvae of both species were negatively buoyant, and larva with normal abdominal length could actively swim and stay suspended in the mid‐ or surface water layers of the culture plates under our experimental conditions. However, no larvae settled or metamorphosed into juveniles under the rearing conditions used in this study. Larvae with shortened abdomens occurred under most of the experimental conditions, although they were less frequent at 10 °C in A. longirostris and 20 °C in S. leurokolos. The maximum survival periods at these temperatures were 88 days in A. longirostris and 30 days in S. leurokolos. These characteristics may cause differences in the distributional ranges of the two species. The present results indicate that temperature is an important factor controlling life‐history traits of vent shrimps.     

条斑紫菜外生细菌的遗传多样性

为研究藻际微生物多样性与紫菜健康养殖的关系,从江苏南通(养殖)、山东青岛(野生)、浙江温州(养殖)三地的条斑紫菜叶状体和江苏东台条斑紫菜贝壳丝状体及其周围的海水样品中分离了条斑紫菜外生细菌。根据菌落特征和菌体形态将获得的63株细菌分为21种表型。16SrDNA-V3片段DGGE分析结合序列测序比对结果表明:这些菌株与假交替单孢菌(Pseudoalteromonas)、嗜冷单胞菌(Psychrobacter)和芽孢杆菌(Bacillus)等10属相应菌株具有较高的同源性。通过对条斑紫菜外生细菌区系多样性分析得出:条斑紫菜藻体外生细菌组成与生活环境相关,但不同于周围海水细菌群落;不同来源(地点)、不同生理状况(健康与病烂)和不同生长阶段(叶状体和丝状体)的条斑紫菜外生菌种群组成差异较大。许多外生细菌对常见测试菌、海水养殖动物致病菌和人致病菌具有抑菌活性,其抑菌特点与紫菜生理性状相关。从健康条斑紫菜样品分离的外生菌中假交替单孢菌占优势,病烂紫菜未分离到假交替单孢菌,提示假交替单孢菌可能与紫菜健康生长有密切关系。     

实验室海月水母大规模解体的初步研究

本实验针对两次突发的饲养海月水母(Aureliaaurita)大规模烂洞解体状况,通过对病灶处进行细菌培养,从其中每次发病水母中均各分离到2种优势病原菌菌株,利用PCR扩增和DNA测序技术,获得优势菌株16SrRNA基因序列,通过生物信息比对分析显示,导致两次海月水母发病的病原菌菌株分别为2种嗜冷杆菌(Psychrobacter sp.)和2种弧菌(Vibrio splendidusVibrio neptunius)。通过利用福林酚法进行此四种优势菌株的细菌发酵培养液蛋白酶活性的测定,结果显示,此4种细菌均具有较强的蛋白酶活性。根据实验结果推测,分离所得的2种嗜冷杆菌菌株(Paa1Paa2)和2种弧菌菌株(Vaa1Vaa2)作为此次发病海月水母的病原菌,有可能均是通过分泌胞外蛋白酶侵蚀水母伞体,从而导致伞体烂洞解体。通过本次实验分析,推测自然条件下水母暴发后的快速消亡是由水母自身免疫下降与细菌侵染的共同作用导致。     

Patterns of growth in cold-seep vestimenferans including Seepiophila jonesi: a second species of long-lived tubeworm

Seepiophila jonesi is a vestimentiferan tubeworm (Siboglinidae: Polychaeta) inhabiting the cold seeps of the upper slope of the Gulf of Mexico. It commonly co‐occurs with Lamellibrachia luymesi, which is among the most long‐lived non‐clonal animals known. The growth pattern of S. jonesi is best described by a model including a size‐specific probability of growth and an average growth rate that does not vary with individual size. This model, based on growth data from in situ staining and collection approximately 1 year later, predicts that S. jonesi is very slow growing and may attain ages comparable with L. luymesi. The efficacy of this model in describing L. luymesi growth rate was assessed, but the previously employed model of declining growth rate with individual size provided the better fit to the empirical data. Comparisons of both S. jonesi and L. luymesi growth rates among sites and among aggregations within a site indicate that there is some degree of habitat variability contributing to differences in growth rates. However, position of the anterior end of the worm within an aggregation did not have a significant effect on growth rate in comparisons among groups of L. luymesi from different distances from the center of an aggregation. The evolution of longevity in these species of vestimentiferans was favored by the relative stability of the seep habitat and sulfide sources, in contrast to the hydrothermal vent environment inhabited by relatively short‐lived and fast‐growing vestimentiferan species.     

Microbial Diversity in Nankai Trough Sediments at a Depth of 3,843 m

Dense populations of bivalves, primarily Calyptogena sp., were observed at cold seeps of the Nankai Trough. Bacterial input to the sediment was estimated through determination of phospholipid ester-linked fatty acid (PLFA) and DNA profiles. Results indicated a bacterial biomass of 10⁹ cells (g dry wt)^-1 while individual fatty acid profiles revealed a predominance of monounsaturated fatty acids, mainly 18:1 isomers. The presence of these fatty acids can be interpreted to reflect a response to low temperature and a predominance of psychrophilic bacteria. DNA fragments encoding bacterial ribosomal RNA small-subunit sequences (16S rDNA) were amplified by the polymerase chain reaction method using DNA extracted directly from the sediment samples. From the sequencing results, at least 19 kinds of bacterial 16S rDNAs related to mostly the Proteobacteria and a few gram-positive bacteria were identified. These results suggest that the bacterial community in the Nankai Trough sediments consists of mainly bacteria belonging to the Proteobacteria , , and subdivisions. Bacteria belonging to the and subdivisions, which are known to include epibiont and sulfate reducing bacteria, respectively, were mostly detected in the sediment obtained from inside the area of the Calyptogena community, and the -Proteobacteria may function to supply reduced sulfur to bacterial endosymbionts of Calyptogena.     

Molecular diversity of Thermococcales isolated from Guaymas Basin hydrothermal vents

Members of Thermococcales are organoheterotrophic hyperthermophilic anaerobes consisting of three genera, Thermococcus, Pyrococcus, and Palaeococcus, among which Thermococcus are the most frequently isolated. In this study, a variety of Thermococcales strains were isolated from the Guaymas Basin hydrothermal vents under different temperatures and pressures. Based on their 16S rRNA gene sequences, all the strains isolated from 85 C or 95 C enrichment cultures at ambient pressure were classified as Thermococcus, while strains isolated from 108 C-30 MPa enrichment cultures belonged to Pyrococcus. The combination of high pressure and high temperature for enrichment was shown to be an efficient method for isolating Pyrococcus strains. Through selecting and analyzing with multiple molecular phylogenetic markers, the isolated Thermococcales strains were found quite diversified including several putative novel species. This demonstrates a vast genetic reservoir of Thermoccoccales in the deep-sea hydrothermal vents, and a fast evolving of the Thermococcales species adapting to the fast changing environment.     

The discovery of a natural whale fall in the Antarctic deep sea

Large cetacean carcasses at the deep-sea floor, known as ‘whale falls’, provide a resource for generalist-scavenging species, chemosynthetic fauna related to those from hydrothermal vents and cold seeps, and remarkable bone-specialist species such as Osedax worms. Here we report the serendipitous discovery of a late-stage natural whale fall at a depth of 1444 m in the South Sandwich Arc. This discovery represents the first natural whale fall to be encountered in the Southern Ocean, where cetaceans are abundant. The skeleton was situated within a seafloor caldera, in close proximity (<250 m) to active hydrothermal vents. We used a DNA barcoding approach to identify the skeleton as that of an Antarctic minke whale (Balaenoptera bonaerensis). The carcass was in an advanced state of decomposition, and its exposed bones were occupied by a diverse assemblage of fauna including nine undescribed species. These bone fauna included an undescribed species of Lepetodrilus limpet that was also present at the nearby hydrothermal vents, suggesting the use of whale-fall habitats as stepping stones between chemosynthetic ecosystems. Using Remotely Operated Vehicle (ROV) videography, we have quantified the composition and abundance of fauna on the whale bones, and tested a hypothesis that varying concentrations of lipids in the bones of whales may influence the microdistribution of sulfophilic whale-fall fauna. Our data supported the hypothesis that more lipid-rich bones support a greater abundance of sulfophilic bacterial mats, which are also correlated with the abundance of grazing limpets (Pyropelta sp.). The abundance of Osedax sp. on bones however, showed a negative correlation with the bacterial-mat percentage cover, and hence greatest abundance on bones predicted to have lowest lipid content.     

针胞藻海洋卡盾藻(Chattonella marina)和硅藻中肋骨条藻(Skeletonema costatum)藻际细菌的分离、鉴定及影响研究

对实验室培养的两株海洋微藻海洋卡盾藻和中肋骨条藻的可培养细菌进行了分离鉴定，分别在海洋卡盾藻和硅藻中肋骨条藻不同生长时期分离得到48株和34株可培养细菌，去除重复序列后得到12株不同的菌株。这些菌株分属α-变形杆菌纲、γ-变形杆菌纲、拟杆菌和放线菌。α-变形杆菌纲在两种藻的藻际环境中占据优势，其中红杆菌科是最为常见的科，中肋骨条藻的藻际细菌比海洋卡盾藻更为多样化。海洋卡盾藻生长后期细菌密度大幅度上升，可能导致了藻细胞的衰亡。中肋骨条藻相关细菌中有一株对旋链角毛藻的生长具有明显抑制作用，而大部分海洋卡盾藻相关细菌对角毛藻的生长具有抑制作用。本研究结果说明海洋卡盾藻的藻际细菌也许对其与硅藻的种间竞争中具有一定作用。