Spatial Differences in East Scotia Ridge Hydrothermal Vent Food Webs: Influences of Chemistry,Microbiology and Predation on Trophodynamics

The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. δ¹³C of dissolved inorganic carbon from vent fluids ranged from −4.6‰ to 0.8‰ at E2 and from −4.4‰ to 1.5‰ at E9. The lowest macroconsumer δ¹³C was observed in peltospiroid gastropods (−30.0‰ to −31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest δ¹³C occurred in Kiwa sp. (−19.0‰ to −10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. δ¹³C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the δ¹³C and δ³⁴S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites.     

Comparison of a New Thiomicrospira Strain from the Mid-Atlantic Ridge with Known Hydrothermal Vent Isolates

A new autotrophic Thiomicrospira strain, MA-3, was isolated from the surface of a polymetal sulfide deposit collected at a Mid-Atlantic Ridge hydrothermal vent site. The DNA homology among three vent isolates, Thiomicrospira crunogena, Thiomicrospira sp. strain L-12, and Thiomicrospira sp. strain MA-3, was 99.3% or higher, grouping them as the same species, T. crunogena (type strain, ATCC 35932). The fact that T. crunogena and Thiomicrospira sp. strain L-12 were isolated from Pacific vent sites demonstrates a cosmopolitan distribution of this species.     

Evidence for Methylotrophic Symbionts in a Hydrothermal Vent Mussel (Bivalvia: Mytilidae) from the Mid-Atlantic Ridge

Symbioses between chemolithoautotrophic bacteria and the major macrofaunal species found at hydrothermal vents have been reported for numerous sites in the Pacific Ocean. We present microscopical and enzymatic evidence that methylotrophic bacteria occur as intracellular symbionts in a new species of mytilid mussel discovered at the Mid-Atlantic Ridge hydrothermal vents. Two distinct ultrastructural types of gram-negative procaryotic symbionts were observed within gill epithelial cells by transmission electron microscopy: small coccoid or rod-shaped cells and larger coccoid cells with stacked intracytoplasmic membranes typical of methane-utilizing bacteria. Methanol dehydrogenase, an enzyme diagnostic of methylotrophs, was detected in the mytilid gills, while tests for ribulose-1,5-bisphosphate carboxylase, the enzyme diagnostic of autotrophy via the Calvin cycle, were negative. Stable carbon isotope values (δ¹³C) of mytilid tissue (−32.7 and −32.5% for gill and foot tissues, respectively) fall within the range of values reported for Pacific vent symbioses but do not preclude the use of vent-derived methane reported to be isotopically heavy relative to biogenically produced methane.     

Diversity and Abundance of Ammonia-Oxidizing Archaea in Hydrothermal Vent Chimneys of the Juan de Fuca Ridge

The abundance and diversity of archaeal ammonia monooxygenase subunit A (amoA) genes from hydrothermal vent chimneys at the Juan de Fuca Ridge were investigated. The majority of the retrieved archaeal amoA sequences exhibited identities of less than 95% to those in the GenBank database. Novel ammonia-oxidizing archaea may exist in the hydrothermal vent environments.Ammonia-oxidizing archaea (AOA) may play important roles in carbon and nitrogen cycles in various temperate environments (5, 7, 10, 12, 16). The frequent detection (23, 24) and successful enrichment (2, 6) of thermophilic AOA from terrestrial hot springs suggested a wide distribution of thermophilic AOA in geothermal environments. High concentrations of NH₄⁺ (1, 9, 11) and high rates of ammonia oxidation (9, 22) have been observed at the Juan de Fuca Ridge. However, the presence of AOA in this deep-sea hydrothermal system has not been reported. Here, the abundance and diversity of AOA in three hydrothermal vent chimneys in the Endeavor segment of the Juan de Fuca Ridge were investigated by targeting the conserved amoA genes. This is also the first report on AOA from deep-sea hydrothermal vent chimneys.These vent chimneys were sulfide structures obtained in the fall of 2005 using the submersible Alvin on board the research vessel Atlantis (dive numbers 4143, 4136, and 4148). Chimney 4148 was an active black smoker venting at around 310°C in the Main Endeavor field (47°56.876′N, 129°5.915′W; depth, 2,192 m). Chimney 4143-1 was an active black smoker venting at 316°C in the Mothra field (47°55.424′N, 129°6.533′W; depth, 2,267 m). The outer layers (samples 4148-1A and 4143-1A) of these chimneys were used in this study. The sample from chimney 4136-1 was from a diffusive field (Clambed field) (47°57.909′N, 129°5.443′W; depth, 2,200 m), where the in situ temperature was measured as 29.2°C. The chimney samples were stored at −20°C on board, transported to the home laboratory on dry ice, and stored at −80°C until analyses were performed.Chimney samples were frozen in liquid nitrogen and milled upon thawing. This procedure was repeated three times to break down the solid sample into small particles, which were then mixed with DNA extraction buffer for DNA isolation as described before (25). The obtained crude DNA was purified by an E-Z N.A. Cycle-Pure kit (Omega Bio-Tek Inc., Norcross, GA). PCR amplifications for the archaeal 16S rRNA gene, the crenarchaeal marine group I (MGI) 16S rRNA gene, the archaeal amoA gene, and the bacterial amoA gene followed procedures previously described (Table ​(Table1)1) (3, 5, 10, 14). Quantitative PCR (Q-PCR) was performed using a model 7500 real-time system (Applied Biosystems, United Kingdom) and a 20-μl reaction mixture that consisted of 1 μl (1 to 10 ng) of DNA as the template, a 0.15 μM concentration of each primer, and 10 μl of Power SYBR green PCR master mix (Applied Biosystems, United Kingdom) with ROX and SYBR green I. The inserted PCR fragments of clones 4143-1A-71 (from the amoA gene library) and 4136-1-4 (from the archaeal 16S rRNA gene library) were amplified and purified to generate standard DNAs for amoA or archaeal 16S rRNA gene quantification. A serial dilution of standard DNAs was performed to generate calibration curves for sample quantification. A melting curve analysis was performed after amplification, and the cycle threshold was set automatically using system 7500 software, version 1.3.

TABLE 1.

PCR primers and procedures used in this study

Bacterial Community Associated with Organs of Shallow Hydrothermal Vent Crab Xenograpsus testudinatus near Kuishan Island,Taiwan

Shallow-water hydrothermal vents off Kueishan Island (northeastern Taiwan) provide a unique, sulfur-rich, highly acidic (pH 1.75–4.6) and variable-temperature environment. In this species-poor habitat, the crab Xenograpsus testudinatus is dominant, as it mainly feeds on zooplankton killed by sulfurous plumes. In this study, 16S ribosomal RNA gene amplicon pyrosequencing was used to investigate diversity and composition of bacteria residing in digestive gland, gill, stomach, heart, and mid-gut of X. testudinatus, as well as in surrounding seawater. Dominant bacteria were Gamma- and Epsilonproteobacteria that might be capable of autotrophic growth by oxidizing reduced sulfur compounds and are usually resident in deep-sea hydrothermal systems. Dominant bacterial OTUs in X. testudinatus had both host and potential organ specificities, consistent with a potential trophic symbiotic relationship (nutrient transfer between host and bacteria). We inferred that versatile ways to obtain nutrients may provide an adaptive advantage for X. testudinatus in this demanding environment. To our knowledge, this is the first study of bacterial communities in various organs/tissues of a crustacean in a shallow-water hydrothermal system, and as such, may be a convenient animal model for studying these systems.     

High Connectivity of Animal Populations in Deep-Sea Hydrothermal Vent Fields in the Central Indian Ridge Relevant to Its Geological Setting

Dispersal ability plays a key role in the maintenance of species in spatially and temporally discrete niches of deep-sea hydrothermal vent environments. On the basis of population genetic analyses in the eastern Pacific vent fields, dispersal of animals in the mid-oceanic ridge systems generally appears to be constrained by geographical barriers such as trenches, transform faults, and microplates. Four hydrothermal vent fields (the Kairei and Edmond fields near the Rodriguez Triple Junction, and the Dodo and Solitaire fields in the Central Indian Ridge) have been discovered in the mid-oceanic ridge system of the Indian Ocean. In the present study, we monitored the dispersal of four representative animals, Austinograea rodriguezensis, Rimicaris kairei, Alviniconcha and the scaly-foot gastropods, among these vent fields by using indirect methods, i.e., phylogenetic and population genetic analyses. For all four investigated species, we estimated potentially high connectivity, i.e., no genetic difference among the populations present in vent fields located several thousands of kilometers apart; however, the direction of migration appeared to differ among the species, probably because of different dispersal strategies. Comparison of the intermediate-spreading Central Indian Ridge with the fast-spreading East Pacific Rise and slow-spreading Mid-Atlantic Ridge revealed the presence of relatively high connectivity in the intermediate- and slow-spreading ridge systems. We propose that geological background, such as spreading rate which determines distance among vent fields, is related to the larval dispersal and population establishment of vent-endemic animal species, and may play an important role in controlling connectivity among populations within a biogeographical province.     

环柄菇属东亚一新记录种———锥鳞环柄菇

报道东亚环柄菇属的一个新记录种———锥鳞环柄菇Lepiota jacobi Vellinga & Knudsen, 标本采自中国云南。该种的鉴别特征是菌盖密被灰色至暗褐色的锥状鳞片; 担孢子椭圆形, 腹部近平直, 极小; 囊状体缺如。     

Dinoflagellate cysts from sediment traps deployed in the Bellingshausen,Weddell and Scotia seas,Antarctica

Dinoflagellate cysts have been recovered from six long-term (1–2 yr) sediment trap moorings deployed in the Bellingshausen, Weddell and Scotia seas, Antarctica. These traps, mostly moored near the sea bed to sample the nepheloid layer, were located both within and to the north of the maximum sea-ice limit. The numbers of cysts, together with the composition of the assemblages, reinforce the importance of the maximum sea-ice limit as a modern biogeographic boundary for the distribution of dinoflagellate cysts. Cysts derived from heterotrophic dinoflagellates make up the highest proportions within the assemblages recovered from the traps. One trap sampled the export production, revealing little difference in cyst flux over those sampling the nepheloid layer. Cyst flux appears to be highest in areas closest to the Antarctic Convergence, north of the maximum sea-ice limit, and to high nutrient availability. There are, however, differences between the sediment trap assemblages and those recovered from core-top samples at the same or nearby sites. These differences, in the greater number of cysts, and in the higher numbers of round, brown Protoperidinium cysts in the traps, may reflect annual differences in the primary productivity and/or cyst production in the area. In some areas the sediment record may preserve little information about local surface water productivity because of the activity of bottom water currents, for example those arising from the Antarctic Circumpolar Current.     

Phylogenetic Diversity of Nitrogenase (nifH) Genes in Deep-Sea and Hydrothermal Vent Environments of the Juan de Fuca Ridge

The subseafloor microbial habitat associated with typical unsedimented mid-ocean-ridge hydrothermal vent ecosystems may be limited by the availability of fixed nitrogen, inferred by the low ammonium and nitrate concentrations measured in diffuse hydrothermal fluid. Dissolved N₂ gas, the largest reservoir of nitrogen in the ocean, is abundant in deep-sea and hydrothermal vent fluid. In order to test the hypothesis that biological nitrogen fixation plays an important role in nitrogen cycling in the subseafloor associated with unsedimented hydrothermal vents, degenerate PCR primers were designed to amplify the nitrogenase iron protein gene nifH from hydrothermal vent fluid. A total of 120 nifH sequences were obtained from four samples: a nitrogen-poor diffuse vent named marker 33 on Axial Volcano, sampled twice over a period of 1 year as its temperature decreased; a nitrogen-rich diffuse vent near Puffer on Endeavour Segment; and deep seawater with no detectable hydrothermal plume signal. Subseafloor nifH genes from marker 33 and Puffer are related to anaerobic clostridia and sulfate reducers. Other nifH genes unique to the vent samples include proteobacteria and divergent Archaea. All of the nifH genes from the deep-seawater sample are most closely related to the thermophilic, anaerobic archaeon Methanococcus thermolithotrophicus (77 to 83% amino acid similarity). These results provide the first genetic evidence of potential nitrogen fixers in hydrothermal vent environments and indicate that at least two sources contribute to the diverse assemblage of nifH genes detected in hydrothermal vent fluid: nifH genes from an anaerobic, hot subseafloor and nifH genes from cold, oxygenated deep seawater.     

Host-Symbiont Relationships in Hydrothermal Vent Gastropods of the Genus Alviniconcha from the Southwest Pacific

Hydrothermal vent gastropods of the genus Alviniconcha are unique among metazoans in their ability to derive their nutrition from chemoautotrophic γ- and -proteobacterial endosymbionts. Although host-symbiont relationships in Alviniconcha gastropods from the Central Indian Ridge in the Indian Ocean and the Mariana Trough in the Western Pacific have been studied extensively, host-symbiont relationships in Alviniconcha gastropods from the Southwest Pacific remain largely unknown. Phylogenetic analysis using mitochondrial cytochrome c oxidase subunit I gene sequences of host gastropods from the Manus, North Fiji, and Lau Back-Arc Basins in the Southwest Pacific has revealed a new host lineage in a Alviniconcha gastropod from the Lau Basin and the occurrence of the host lineage Alviniconcha sp. type 2 in the Manus Basin. Based on 16S rRNA gene sequences of bacterial endosymbionts, two γ-proteobacterial lineages and one -proteobacterial lineage were identified in the present study. The carbon isotopic compositions of the biomass and fatty acids of the gastropod tissues suggest that the γ- and -proteobacterial endosymbionts mediate the Calvin-Benson cycle and the reductive tricarboxylic acid cycle, respectively, for their chemoautotrophic growth. Coupling of the host and symbiont lineages from the three Southwest Pacific basins revealed that each of the Alviniconcha lineages harbors different bacterial endosymbionts belonging to either the γ- or -Proteobacteria. The host specificity exhibited in symbiont selection provides support for the recognition of each of the host lineages as a distinct species. The results from the present study also suggest the possibility that Alviniconcha sp. types 1 and 2 separately inhabit hydrothermal vent sites approximately 120 m apart in the North Fiji Basin and 500 m apart in the Manus Basin.     

Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica)

In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (E_h) were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition (⁸⁷Sr/⁸⁶Sr  = 0.708776 at core base) compared with modern seawater (⁸⁷Sr/⁸⁶Sr ≈0.70918), indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column E_h anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in E_h, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota.     

Life history strategies of the Scotia Sea icefish, <Emphasis Type="Italic">Chaenocephalus aceratus</Emphasis>, along the Southern Scotia Ridge

Reproductive capacity can influence distribution and abundance over large spatial scales through larval dispersal, even when adult stages remain isolated following settlement. We examined size distribution, reproductive traits and age structure in Scotia Sea icefish, Chaenocephalus aceratus, an abundant benthic species with a long larval pelagic phase found on continental shelves along the Southern Scotia Ridge. In particular, we compared life history strategies between fish caught during surveys undertaken off the South Orkney Islands (SOI) and South Shetland Islands (SSI). Results corroborated regional separation after settlement and suggested distinct life history strategies, in which fish from SOI invested much less in reproduction, and somewhat more in somatic growth earlier in their life history. Compared to SSI, body weight increased faster with length and absolute fecundity was 46 % lower and increased more slowly with size for SOI population. In addition, the proportion of spawning cohorts and L _∞ was lower and k higher for SOI. The differences appeared to be a phenotypic response to environmental conditions related to regional hydrography. Lower reproductive capacity around the SOI, and strong eastward flow in the large-scale circulation, suggests that the SSI may be more important in influencing distributions and abundance of icefish along the Southern Scotia Ridge.     

Heterologous Expression and Biochemical Characterization of a New Chloroperoxidase Isolated from the Deep-Sea Hydrothermal Vent Black Yeast Hortaea werneckii UBOCC-A-208029

Marine Biotechnology - The initiation of this study relies on a targeted genome-mining approach to highlight the presence of a putative vanadium-dependent haloperoxidase-encoding gene in the...     

Characterization of a Novel Spirochete Associated with the Hydrothermal Vent Polychaete Annelid, Alvinella pompejana

A highly integrated, morphologically diverse bacterial community is associated with the dorsal surface of Alvinella pompejana, a polychaetous annelid that inhabits active high-temperature deep-sea hydrothermal vent sites along the East Pacific Rise (EPR). Analysis of a previously prepared bacterial 16S ribosomal DNA (rDNA) library identified a spirochete most closely related to an endosymbiont of the oligochete Olavius loisae. This spirochete phylotype (spirochete A) comprised only 2.2% of the 16S rDNA clone library but appeared to be much more dominant when the same sample was analyzed by denaturing gradient gel electrophoresis (DGGE) and the terminal restriction fragment length polymorphism procedure (12 to 18%). PCR amplification of the community with spirochete-specific primers used in conjunction with DGGE analysis identified two spirochete phylotypes. The first spirochete was identical to spirochete A but was present in only one A. pompejana specimen. The second spirochete (spirochete B) was 84.5% similar to spirochete A and, more interestingly, was present in the epibiont communities of all of the A. pompejana specimens sampled throughout the geographic range of the worm (13°N to 32°S along the EPR). The sequence variation of the spirochete B phylotype was less than 3% for the range of A. pompejana specimens tested, suggesting that a single spirochete species was present in the A. pompejana epibiotic community. Additional analysis of the environments surrounding the worm revealed that spirochetes are a ubiquitous component of high-temperature vents and may play an important role in this unique ecosystem.     

Debris accumulation on oceanic island shores of the Scotia Arc, Antarctica

The oceanic islands in the Southern Ocean can be considered amongst the remotest shores as, not only are they uninhabited (except for small research stations) and geographically isolated, but they are also enclosed by the oceanographic barrier of the Polar Frontal Zone. We survey island shores in the Scotia Arc mountain chain linking Antarctica to South America, including South Georgia, the South Sandwich archipelago and Adelaide Island off the west coast of the Antarctic Peninsula, and compare our findings to literature reports from two other Scotia Arc island groups (South Orkney and South Shetland archipelagos). The presence of marine pollution (in the form of beached debris) in this region is significant, both as a measure of man's influence on this isolated environment, and due to direct dangers posed to the fauna. This paper reports the results of surveys of beached marine debris at various times in the last decade for each island group. The majority (>70%) of the items recovered were anthropogenic in origin and most of these were synthetic (plastic or polystyrene). Debris densities varied from zero to 0.3 items m^-1 but were typically lower than those reported from other regions of the globe. At some localities (South Georgia), marine-debris data showed a close relationship with local fishery activity, whilst at others (South Sandwich Islands) debris appeared to have a more distant origin. Unlike oceanic debris in warm (non-polar) water localities, there was no evidence of any colonisation by biota. Debris accumulation may provide a useful indirect measure of local fishery activity and compliance with CCAMLR regulations, as well as monitoring the state of the oceans and island shores.     

Distribution of Microorganisms in the Subsurface of the Manus Basin Hydrothermal Vent Field in Papua New Guinea

The distribution of microorganisms in the subsurfaces of hydrothermal vents was investigated by using subvent rock core samples. Microbial cells and ATP were detected from cores taken at depths of less than 99.4 and 44.8 m below the seafloor (mbsf), respectively. Cores from various depths were incubated anaerobically with a heterotrophic medium. Growth at 60 and 90°C was ascribed to a Geobacillus sp. in the 448.6- to 99.4-mbsf cores and a Deinococcus sp. in the 64.8- to 128.9-mbsf cores, respectively, based on the 16S ribosomal DNA analysis.     

Novel Forms of Structural Integration between Microbes and a Hydrothermal Vent Gastropod from the Indian Ocean

Here we describe novel forms of structural integration between endo- and episymbiotic microbes and an unusual new species of snail from hydrothermal vents in the Indian Ocean. The snail houses a dense population of γ-proteobacteria within the cells of its greatly enlarged esophageal gland. This tissue setting differs from that of all other vent mollusks, which harbor sulfur-oxidizing endosymbionts in their gills. The significantly reduced digestive tract, the isotopic signatures of the snail tissues, and the presence of internal bacteria suggest a dependence on chemoautotrophy for nutrition. Most notably, this snail is unique in having a dense coat of mineralized scales covering the sides of its foot, a feature seen in no other living metazoan. The scales are coated with iron sulfides (pyrite and greigite) and heavily colonized by - and δ-proteobacteria, likely participating in mineralization of the sclerites. This novel metazoan-microbial collaboration illustrates the great potential of organismal adaptation in chemically and physically challenging deep-sea environments.     

环柄菇属东亚一新记录种——锥鳞环柄菇

报道东亚环柄菇属的—个新记录种——锥鳞环柄菇Lepota jacobi Vellinga ＆ Knudsen,标本采自中国云南。该种的鉴别特征是菌盖密被灰色至暗褐色的锥状鳞片;担孢子椭圆形,腹部近平直,极小;囊状体缺如。