Rates of Microbial Production and Oxidation of Methane in the Bottom Sediments and Water Column of the Black Sea

Rates of biogeochemical (microbial) processes of methane production and methane oxidation were determined in the bottom sediments and water column of the Black Sea. Aerobic bacterial oxidation of methane was confined to the upper 20–30 cm of Holocene bottom sediments of the shelf (0.7–259 ng C/(dm³ day)) and to oxygenated waters (0.2–45 ng C/(dm³ day)). In reduced sediments of the deep-sea zone and in the hydrogen sulfide–containing water column, considerable rates of anaerobic methane oxidation were recorded, comparable to or exceeding the rates of methane oxidation in oxygenated layers. From one-fourth to one-half of the methane formed in bottom sediments was oxidized immediately therein. The major part of the remaining methane was oxidized in the water column, and a smaller portion arrived in the atmosphere.     

Seasonal Rates of Methane Oxidation in Anoxic Marine Sediments

Methane concentrations and rates of methane oxidation were measured in intact sediment cores from an inshore marine sediment at Jutland, Denmark. The rates of methane oxidation, determined by the appearance of ¹⁴CO₂ from injected ¹⁴CH₄, varied with sediment depth and season. Most methane oxidation was anoxic, but oxygen may have contributed to methane oxidation at the sediment surface. Cumulative rates (0- to 12-cm depth) for methane oxidation at Kysing Fjord were 3.34, 3.48, 8.60, and 17.04 μmol m⁻² day⁻¹ for April (4°C), May (13°C), July (17°C), and August (21°C), respectively. If all of the methane was oxidized by sulfate, it would account for only 0.01 to 0.06% of the sulfate reduction. The data indicate that methane was produced, in addition to being oxidized, in the 0- to 18-cm sediment stratum.     

Cold Regime Interannual Variability of Primary and Secondary Producer Community Composition in the Southeastern Bering Sea

Variability of hydrographic conditions and primary and secondary productivity between cold and warm climatic regimes in the Bering Sea has been the subject of much study in recent years, while interannual variability within a single regime and across multiple trophic levels has been less well-documented. Measurements from an instrumented mooring on the southeastern shelf of the Bering Sea were analyzed for the spring-to-summer transitions within the cold regime years of 2009–2012 to investigate the interannual variability of hydrographic conditions, primary producer biomass, and acoustically-derived secondary producer and consumer abundance and community structure. Hydrographic conditions in 2012 were significantly different than in 2009, 2010, and 2011, driven largely by increased ice extent and thickness, later ice retreat, and earlier stratification of the water column. Primary producer biomass was more tightly coupled to hydrographic conditions in 2012 than in 2009 or 2011, and shallow and mid-column phytoplankton blooms tended to occur independent of one another. There was a high degree of variability in the relationships between different classes of secondary producers and hydrographic conditions, evidence of significant intra-consumer interactions, and trade-offs between different consumer size classes in each year. Phytoplankton blooms stimulated different populations of secondary producers in each year, and summer consumer populations appeared to determine dominant populations in the subsequent spring. Overall, primary producers and secondary producers were more tightly coupled to each other and to hydrographic conditions in the coldest year compared to the warmer years. The highly variable nature of the interactions between the atmospherically-driven hydrographic environment, primary and secondary producers, and within food webs underscores the need to revisit how climatic regimes within the Bering Sea are defined and predicted to function given changing climate scenarios.     

楚科奇海及白令海大型底栖生物初步研究

1999年夏季在楚科奇海、白令海采用30 cm×30 cm箱式取样器,取得16个站位大型底栖生物定量样品。经分析研究有大型底栖生物92科164种,其中多毛类、软体动物和甲壳动物种数最多,占总种数的88.41％,三者构成北极楚科奇海和白令海大型底栖生物的主要类群。优势种有独毛虫属一种(Tharyx sp.) 、齿吻沙蚕属一种(Nephtys sp.)、囊叶齿吻沙蚕(Nephtys caeca)、平滑胡桃蛤(Ennucula tenuis)、短吻状蛤(Nuculana pernula pernuloides)、拟猛钩虾属一种( sp.)、日本沙钩虾(Byblis japonicus)和萨氏真蛇尾(Ophiura sarsii)等。楚科奇海和白令海大型底栖生物平均生物量为111.83 g/m²,平均栖息密度为2538个/m²。生物量和栖息密度均以多毛类和软体动物占多数。楚科奇海和白令海大型底栖生物有5个群落类型：Ⅰ. 梯额虫(Scalibregma inflatum)-紫轮参(Polycheira rufescens)-结栉盖蛇尾(Stegophiura nodosa)群落, Ⅱ. 拟单指虫(Cossurella sp.)-平滑胡桃蛤-鳞甲钩虾(Lepidepecreum sp.)群落, Ⅲ. 缩头竹节虫(Maldane sarai)-葛氏希泊钩虾(Hippomedon gorbunovi)-萨氏真蛇尾群落, Ⅳ.齿吻沙蚕(Nephtys sp.)-平滑胡桃蛤-日本沙钩虾-戈芬星虫(Golfingia sp.)群落和白令海群落, 即索沙蚕(Lumbrineris fragilis)-户枢蛤(Asthenothaerus sp.)-太平洋方甲涟虫(Eudorella pacifica)-革囊星虫(Phascolion sp.)群落。楚科奇海的群落Ⅰ、群落Ⅱ和白令海各群落结构相对稳定;楚科奇海群落Ⅲ和群落Ⅳ出现一定扰动。     

Growth and Methane Oxidation Rates of Anaerobic Methanotrophic Archaea in a Continuous-Flow Bioreactor

Anaerobic methanotrophic archaea have recently been identified in anoxic marine sediments, but have not yet been recovered in pure culture. Physiological studies on freshly collected samples containing archaea and their sulfate-reducing syntrophic partners have been conducted, but sample availability and viability can limit the scope of these experiments. To better study microbial anaerobic methane oxidation, we developed a novel continuous-flow anaerobic methane incubation system (AMIS) that simulates the majority of in situ conditions and supports the metabolism and growth of anaerobic methanotrophic archaea. We incubated sediments collected from within and outside a methane cold seep in Monterey Canyon, Calif., for 24 weeks on the AMIS system. Anaerobic methane oxidation was measured in all sediments after incubation on AMIS, and quantitative molecular techniques verified the increases in methane-oxidizing archaeal populations in both seep and nonseep sediments. Our results demonstrate that the AMIS system stimulated the maintenance and growth of anaerobic methanotrophic archaea, and possibly their syntrophic, sulfate-reducing partners. Our data demonstrate the utility of combining physiological and molecular techniques to quantify the growth and metabolic activity of anaerobic microbial consortia. Further experiments with the AMIS system should provide a better understanding of the biological mechanisms of methane oxidation in anoxic marine environments. The AMIS may also enable the enrichment, purification, and isolation of methanotrophic archaea as pure cultures or defined syntrophic consortia.     

Carbon Dioxide Assimilation and Methane Oxidation in Various Zones of the Rainbow Hydrothermal Field

Rates of carbon dioxide assimilation and methane oxidation were determined in various zones of the Rainbow Hydrothermal Field (36°N) of the Mid-Atlantic Ridge. In the plume above the hydrothermal field, anomalously high methane content was recorded, the microbial population density (up to 10⁵ cells/ml) was an order of magnitude higher than the background values, and the CO₂ assimilation rate varied from 0.01 to 1.1 g C/(l day). Based on the data on CO₂ assimilation, the production of organic carbon due to bacterial chemosynthesis in the plume was calculated to be 930 kg/day or 340 tons/year (about 29% of the organic carbon production in the photic zone). In the black smoke above active smokers, the microbial population density was as high as 10⁶ cells/ml, the rate of CO₂ assimilation made up 5–10 g C/(l day), the methane oxidation rate varied from 0.15 to 12.7 l/(l day), and the methane concentration ranged from 1.05 to 70.6 l/l. In bottom sediments enriched with sulfides, the rate of CO₂ assimilation was at least an order of magnitude higher than in oxidized metal-bearing sediments. At the base of an active construction, whitish sediment was found, which was characterized by a high methane content (92 l/dm³) and a high rate of methane oxidation (1.7 l/(dm³ day)).     

Pelagic Food Chain of the Bering Sea

Journal of Ichthyology - The order of magnitude of biomass and production at various trophic levels in the epipelagic community has been calculated, and the main pathways for the transformation of...     

Ammonium and Nitrite Inhibition of Methane Oxidation by Methylobacter albus BG8 and Methylosinus trichosporium OB3b at Low Methane Concentrations

Methane oxidation by pure cultures of the methanotrophs Methylobacter albus BG8 and Methylosinus trichosporium OB3b was inhibited by ammonium choride and sodium nitrite relative to that in cultures assayed in either nitrate-containing or nitrate-free medium. M. albus was generally more sensitive to ammonium and nitrite than M. trichosporium. Both species produced nitrite from ammonium; the concentrations of nitrite produced increased with increasing methane concentrations in the culture headspaces. Inhibition of methane oxidation by nitrite was inversely proportional to headspace methane concentrations, with only minimal effects observed at concentrations of>500 ppm in the presence of 250 μM nitrite. Inhibition increased with increasing ammonium at methane concentrations of 100 ppm. In the presence of 500 μM ammonium, inhibition increased initially with increasing methane concentrations from 1.7 to 100 ppm; the extent of inhibition decreased with methane concentrations of > 100 ppm. The results of this study provide new insights that explain some of the previously observed interactions among ammonium, nitrite, methane, and methane oxidation in soils and aquatic systems.     

Anaerobic Methane Oxidation and Sulfate Reduction in Bacterial Mats on Coral-Like Carbonate Structures in the Black Sea

A detailed study of the processes of anaerobic methane oxidation and sulfate reduction in the bacterial mats occurring on coral-like carbonate structures in the region of methane seeps in the Black Sea, as well as of the phenotypic diversity of sulfate-reducing bacteria developing in this zone, has been performed. The use of the radioisotopic method shows the microbial mat structure to be heterogeneous. The peak activity of the two processes was revealed when a mixture of the upper (dark) and underlying (intensely pink) layers was introduced into an incubation flask, which confirms the suggestion that methanotrophic archaea and sulfate-reducing bacteria closely interact in the process of anaerobic methane oxidation. Direct correlation between the rate of anaerobic methane oxidation and the methane and electron acceptor concentrations in the medium has been experimentally demonstrated. Several enrichment and two pure cultures of sulfate-reducing bacteria have been obtained from the near-bottom water and bacterial mats. Both strains were found to completely oxidize the substrates to CO₂ and H₂S. The bacteria grow at temperatures ranging from −1 to 18 (24)°C, with an optimum in the 10–18°C range, and require the presence of 1.5–2.5% NaCl and 0.07–0.2% MgCl 2⋅6H₂O. Regarding the aggregate of their phenotypic characteristics (cell morphology, spectrum of growth substrates, the capacity for complete oxidation), the microorganisms isolated have no analogues among the psychrophilic sulfate-reducing bacteria already described. The results obtained demonstrate the wide distribution of psychrophilic sulfate-reducing bacteria in the near-bottom water and bacterial mats covering the coral-like carbonate structures occurring in the region of methane seeps in the Black Sea, as well as the considerable catabolic potential of this physiological group of psychrophilic anaerobes in deep-sea habitats__________Translated from Mikrobiologiya, Vol. 74, No. 3, 2005, pp. 420–429.Original Russian Text Copyright © 2005 by Pimenov, Ivanova.     

Subtropical migrants in the southwestern part of the Bering Sea

From 2003 to 2008, arrivals (including mass) of sea bream Brama japonica, saury Cololabis saira, and spiny dogfish Squalus acanthias, as well as some cases of catches of Japanese anchovy Engraulis japonicus, and Todarodes pacificus, and Onychoteuthis borealijaponica squids were recorded in Pacific waters of Kamchatka in the southwestern sector of the Bering Sea. The penetration of these species far to the north is related to feeding migrations as well as to the passive transfer of water by currents. Migrations of subtropical species to Pacific waters of Kamchatka and the southern part of the Bering Sea depend on thermal conditions and circulation of currents in each particular year and are determined, first of all, by the intensity of the Western Subarctic gyre, although in some years, the migration flow of B. japonica and C. saira from the northeastern part of the Pacific Ocean increases.     

Phylogenetic diversity of sediment bacteria in the northern Bering Sea

The bacterial diversity in sediments from the northern Bering Sea was investigated by culture-independent approaches. Community fingerprint analysis by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that sediment at two deep stations (DBSE and DBS1, >400 m in depth) harbored a bacterial community distinct from the sediments collected at shallow stations (<150 m in depth) on the continental shelf. Three 16S rRNA gene clone libraries for sediments collected from shallow to deep water stations (NEC5, DBSE and DBS1, respectively) were established. Sediment collected at the deepest station DBS1 showed the highest diversity index value. Sequences fell into 19 major lineages of the domain Bacteria: Alpha-, Beta-, Gamma-, Delta- and Epsilonproteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, Firmicutes, Planctomycetes, Nitrospirae, Verrucomicrobia, Chloroflexi, Chlorobi, Spirochaetes, Cyanobacteria (or chloroplasts), and candidate divisions OP8, TM6, and WS3. A small fraction of retrieved sequences (1.8%) did not fall into any taxonomic division. Deltaproteobacteria (30%) was the dominant phylum in the three libraries, followed by Gammaproteobacteria (21%) and Acidobacteria (16%). The percentages of cloned sequences with the highest similarity to reported sequences below 97 and 93% were 48.1 and 24.3%, respectively. A large number of phylotypes affiliated with bacteria that play important roles in the carbon, sulfur, and nitrogen cycles suggest an important link of bacteria to the matter cycling in these subarctic sediments.     

Feeding ecology of dominant groundfish in the northern Bering Sea

We investigated current diets of the six most abundant benthic fish in the northern Bering Sea. Our objective was to explore feeding strategies and potential competition with other top predators as ecosystem changes occur in the northern Bering Sea ecosystem. Our approach used stomach content data collected from field sampling during spring 2006 and 2007. Calanoid copepods and ampeliscid amphipods were important prey of Arctic cod (Boreogadus saida) but in different proportions depending upon fish size, feeding location, and local environmental conditions. Snailfish (Liparidae) occupied a broad niche and fed on a variety of benthic amphipods. Arctic alligatorfish (Ulcina olrikii) and Arctic staghorn sculpin (Gymnocanthus tricuspis) consumed ampeliscid amphipods predominantly. Shorthorn sculpin (Myoxocephalus scorpius) had a less-diverse diet, with snow crab (Chionoecetes opilio) most important by weight. Finally, all Bering flounder (Hippoglossoides robustus) sampled had empty stomachs. Our results indicate that ampeliscid amphipods, which have high biomass in the central region of the northern Bering Sea, are the most important prey for the dominant groundfish in the Chirikov Basin. Generally, all dominant benthic fish in the northern Bering Sea had narrow feeding niches, except snailfish. High diet overlap was found among many of the fish species, including Arctic cod and snailfish, snailfish and Arctic alligatorfish, and Arctic alligatorfish and Arctic staghorn sculpin. These findings are consistent with a relatively short food chain for benthic fish that are for the most part specialized feeders with narrow preferences for food and may be affected by changes in benthic prey distributions.     

Genetic differentiation of Pacific cod Gadus macrocephalus in the Sea of Okhotsk and in the Bering Sea

Genetic differentiation of the Pacific cod Gadus macrocephalus was studied. Samples from six regions of the Sea of Okhotsk and the Bering Sea were analyzed with two mtDNA genetic markers-gene of cytochrome 1 and the control region (D-loop). Comparative analysis showed significant genetic differentiation between the two groups of samples. The first group included samples from Tauiskaya Bay and waters of Western Kamchatka. The second group consisted of the samples collected in the waters of the Iturup Island (Sea of Okhotsk), Northern Kurile Islands, Navarin region of the Bering Sea, and Anadyr Bay.     

Environmental Predictors of Ice Seal Presence in the Bering Sea

Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20–30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season.     

Evidence for the Cooccurrence of Nitrite-Dependent Anaerobic Ammonium and Methane Oxidation Processes in a Flooded Paddy Field

Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two of the most recent discoveries in the microbial nitrogen cycle. In the present study, we provide direct evidence for the cooccurrence of the anammox and n-damo processes in a flooded paddy field in southeastern China. Stable isotope experiments showed that the potential anammox rates ranged from 5.6 to 22.7 nmol N₂ g⁻¹ (dry weight) day⁻¹ and the potential n-damo rates varied from 0.2 to 2.1 nmol CO₂ g⁻¹ (dry weight) day⁻¹ in different layers of soil cores. Quantitative PCR showed that the abundance of anammox bacteria ranged from 1.0 × 10⁵ to 2.0 × 10⁶ copies g⁻¹ (dry weight) in different layers of soil cores and the abundance of n-damo bacteria varied from 3.8 × 10⁵ to 6.1 × 10⁶ copies g⁻¹ (dry weight). Phylogenetic analyses of the recovered 16S rRNA gene sequences showed that anammox bacteria affiliated with “Candidatus Brocadia” and “Candidatus Kuenenia” and n-damo bacteria related to “Candidatus Methylomirabilis oxyfera” were present in the soil cores. It is estimated that a total loss of 50.7 g N m⁻² per year could be linked to the anammox process, which is at intermediate levels for the nitrogen flux ranges of aerobic ammonium oxidation and denitrification reported in wetland soils. In addition, it is estimated that a total of 0.14 g CH₄ m⁻² per year could be oxidized via the n-damo process, while this rate is at the lower end of the aerobic methane oxidation rates reported in wetland soils.     

Russian-American Bering Sea Relations: Research and Reciprocity

Knowledge of the peopling of the New World and of biological and cultural evolution would be enhanced by more US-USSR research exchanges and more joint field expeditions characterized by mutual scientific benefit, specific objectives, and reciprocity, on both sides of the Bering Sea. A brief review of a sample of related events between 1741 and 1981 indicates the continuity of common research problems and productive results that were multiplied by scientific cooperation.     

Oxidation and Assimilation of Atmospheric Methane by Soil Methane Oxidizers

The metabolism of atmospheric methane in a forest soil was studied by radiotracer techniques. Maximum (sup14)CH(inf4) oxidation (163.5 pmol of C cm(sup-3) h(sup-1)) and (sup14)C assimilation (50.3 pmol of C cm(sup-3) h(sup-1)) occurred at the A(inf2) horizon located 15 to 18 cm below the soil surface. At this depth, 31 to 43% of the atmospheric methane oxidized was assimilated into microbial biomass; the remaining methane was recovered as (sup14)CO(inf2). Methane-derived carbon was incorporated into all major cell macromolecules by the soil microorganisms (50% as proteins, 19% as nucleic acids and polysaccharides, and 5% as lipids). The percentage of methane assimilated (carbon conversion efficiency) remained constant at temperatures between 5 and 20(deg)C, followed by a decrease at 30(deg)C. The carbon conversion efficiency did not increase at methane concentrations between 1.7 and 1,000 ppm. In contrast, the overall methane oxidation activity increased at elevated methane concentrations, with an apparent K(infm) of 21 ppm (31 nM CH(inf4)) and a V(infmax) of 188 pmol of CH(inf4) cm(sup-3) h(sup-1). Methane oxidizers from soil depths with maximum methanotrophic activity respired approximately 1 to 3% of the assimilated methane-derived carbon per day. This apparent endogenous respiration did not change significantly in the absence of methane. Similarly, the potential for oxidation of atmospheric methane was relatively insensitive to methane starvation. Soil samples from depths above and below the zone with maximum atmospheric methane oxidation activity showed a dramatic increase in the turnover of the methane assimilated (>20 times increase). Physical disturbance such as sieving or mixing of soil samples decreased methane oxidation and assimilation by 50 to 58% but did not alter the carbon conversion efficiency. Ammonia addition (0.1 or 1.0 (mu)mol g [fresh weight](sup-1)) decreased both methane oxidation and carbon conversion efficiency. This resulted in a dramatic decrease in methane assimilation (85 to 99%). In addition, ammonia-treated soil showed up to 10 times greater turnover of the assimilated methane-derived carbon (relative to untreated soil). The results suggest a potential for microbial growth on atmospheric methane. However, growth was regulated strongly by soil parameters other than the methane concentration. The pattern observed for metabolism of atmospheric methane in soils was not consistent with the physiology of known methanotrophic bacteria.