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21.
Jellyfish blooms have increased worldwide,and the outbreaks of jellyfish population not only affect the food web structures via voracious predation but also play an important role in the dynamics of nutrients and oxygen in planktonic food webs.However,it remains unclear whether specific carbon compounds released through j ellyfish metabolic processes have the potential to shape bacterial community composition.Therefore,in this study,we aimed to investigate the compositional succession of the bacterioplankton community in response to the dissolved organic matter(DOM)released by the live Scyphomedusae Cyanea lamarcki'i and Chrysaora hysoscella collected from Helgoland Roads of the North Sea.The bacterial community was significantly stimulated by the DOM released form live jellyfish and different dominant phylotypes were observed for these two Scyphomedusae species.Furthermore,the bacterial community structures in the different DOM sources,jellyfish-incubated media,Kabeltonne seawater,and artificial seawater(DOM-free)were significantly different,as revealed by automated ribosomal intergenic spacer analy sis fingerprints.Catalyzed reporter depo sition fluorescence in situ hybridization(CARD-FISH)revealed a rapid species-specific shift in bacterial community composition.Gammaproteobacteria dominated the community instead of the Bacteroidetes community for C.lamarckii,whereas Gammaproteobacteria and Bacteroidetes dominated the community for C.hysoscella.The significant differences in the bacterial community composition and succession indicate that the components of the DOM released by jellyfish might differ with jellyfish species. 相似文献
22.
Christian Hensen Matthias Zabel Tilmann Schwenk Natascha Riedinger Antje Boetius 《Geochimica et cosmochimica acta》2003,67(14):2631-2647
Gravity driven mass-flow deposits proven by sedimentary and digital echosounder data are indicative for prevailing dynamic sedimentary conditions along the continental margin of the western Argentine Basin. In this study we present geochemical data from a total of 23 gravity cores. Pore-water SO4 is generally depleted within a few meters below the sediment surface by anaerobic oxidation of methane (AOM). The different shapes of SO4 profiles (concave, kink- and s-type) can be consistently explained by sedimentary slides possibly in combination with changes in the CH4 flux from below, thus, mostly representing transient pore-water conditions. Since slides may keep their original sedimentary signature, a combined analysis and numerical modeling of geochemical, physical properties, and hydro acoustic data could be applied in order to reconstruct the sedimentary history. We present first order estimates of the dating of sedimentary events for an area where conventional stratigraphic methods failed to this day. The results of the investigated sites suggest that present day conditions are the result of events that occurred decades to thousands of years ago and promote a persisting mass transport from the shelf into the deep-sea, depositing high amounts of reactive compounds. The high abundance of reactive iron phases in this region maintains low hydrogen sulfide levels in the sediments by a nearly quantitative precipitation of all reduced sulfate by AOM. For the total region we estimate a SO4 (or CH4) flux of 6.6 × 1010 moles per year into the zone of AOM. Projected to the global continental slope and rise area, this may sum up to about 2.6 × 1012 moles per year. Provided that the sulfur is completely fixed in the sediments it is about twice the global value of the recent global sulfur burial in marine sediments of 1.2 × 1012 moles per year as previously estimated. Thus, AOM obviously contributes very significantly to the regulation of global sulfur reservoirs, which is hitherto not sufficiently recognized. This finding may have implications for global geochemical models, as sulfur burial is an important control factor in the development of atmospheric oxygen levels over time. 相似文献
23.
Blas L. Valero-Garcés Penélope González-Sampériz Ana Navas Javier Machín Pilar Mata Antonio Delgado-Huertas Roberto Bao Ana Moreno José S. Carrión Antje Schwalb Antonio González-Barrios 《Journal of Paleolimnology》2006,35(3):441-465
The multidisciplinary study of sediment cores from Laguna Zoñar (37°29′00′′ N, 4°41′22′′ W, 300 m a.s.l., Andalucía, Spain) provides a detailed record of environmental, climatic and anthropogenic changes in a Mediterranean watershed since Medieval times, and an opportunity to evaluate the lake restoration policies during the last decades. The paleohydrological reconstructions show fluctuating lake levels since the end of the Medieval Warm Period (ca. AD 1300) till the late 19th century and a more acute dry period during the late 19th century – early 20th century, after the end of the Little Ice Age. Human activities have played a significant role in Laguna Zoñar hydrological changes since the late 19th century, when the outlet was drained, and particularly in the mid-20th century (till 1982) when the spring waters feeding the lake were diverted for human use. Two main periods of increased human activities in the watershed are recorded in the sediments. The first started with the Christian conquest and colonization of the Guadalquivir River Valley (13th century) particularly after the fall of the Granada Kingdom (15th century). The second one corresponds to the late 19th century when more land was dedicated to olive cultivation. Intensification of soil erosion occurred in the mid-20th century, after the introduction of farm machinery. The lake was declared a protected area in the early 1980s, when some agricultural practices were restricted, and conservation measures implemented. As a consequence, the lake level increased, and some littoral zones were submerged. Pollen indicators reflect this limnological change during the last few decades. Geochemical indicators show a relative decrease in soil erosion, but not changes in the amount of chemical fertilizers reaching the lake. This study provides an opportunity to evaluate the relative significance of human vs. climatic factors in lake hydrology and watershed changes during historical times. Paleolimnological reconstructions should be taken into account by natural resources agencies to better define lake management policies, and to assess the results of restoration policies. 相似文献
24.
Francisco Javier Hern��ndez-Molina Dorrik A. V. Stow Estefan��a Llave Michele Rebesco Gemma Ercilla David Van Rooij Anxo Mena Juan-Tom��s V��zquez Antje H. L. Voelker 《Geo-Marine Letters》2011,31(5-6):285-300
Deep-water circulation is a critical part of the global conveyor belt that regulates Earth??s climate. The bottom (contour)-current component of this circulation is of key significance in shaping the deep seafloor through erosion, transport, and deposition. As a result, there exists a high variety of large-scale erosional and depositional features (drifts) that together form more complex contourite depositional systems on continental slopes and rises as well as in ocean basins, generated by different water masses flowing at different depths and at different speeds either in the same or in opposite directions. Yet, the nature of these deep-water processes and the deposited contourites is still poorly understood in detail. Their ultimate decoding will undoubtedly yield information of fundamental importance to the earth and ocean sciences. The international congress Deep-water Circulation: Processes & Products was held from 16?C18 June 2010 in Baiona, Spain, hosted by the University of Vigo. Volume 31(5/6) of Geo-Marine Letters is a special double issue containing 17 selected contributions from the congress, guest edited by F.J. Hernández-Molina, D.A.V. Stow, E. Llave, M. Rebesco, G. Ercilla, D. Van Rooij, A. Mena, J.-T. Vázquez and A.H.L. Voelker. The papers and discussions at the congress and the articles in this special issue provide a truly multidisciplinary perspective of interest to both academic and industrial participants, contributing to the advancement of knowledge on deep-water bottom circulation and related processes, as well as contourite sedimentation. The multidisciplinary contributions (including geomorphology, tectonics, stratigraphy, sedimentology, paleoceanography, physical oceanography, and deep-water ecology) have demonstrated that advances in paleoceanographic reconstructions and our understanding of the ocean??s role in the global climate system depend largely on the feedbacks among disciplines. New insights into the link between the biota of deep-water ecosystems and bottom currents confirm the need for this field to be investigated and mapped in detail. Likewise, it is confirmed that deep-water contourites are not only of academic interest but also potential resources of economic value. Cumulatively, both the congress and the present volume serve to demonstrate that the role of bottom currents in shaping the seafloor has to date been generally underestimated, and that our understanding of such systems is still in its infancy. Future research on contourites, using new and more advanced techniques, should focus on a more detailed visualization of water-mass circulation and its variability, in order to decipher the physical processes involved and the associations between drifts and other common bedforms. Moreover, contourite facies models should be better established, including their associations with other deep-water sedimentary environments both in modern and ancient submarine domains. The rapid increase in deep-water exploration and the new deep-water technologies available to the oil industry and academic institutions will undoubtedly lead to spectacular advances in contourite research in terms of processes, morphology, sediment stacking patterns, facies, and their relationships with other deep-marine depositional systems. 相似文献
25.
Subfossil remains of the Pediastrum-algae group (Fam. Hydrodictyaceae) are frequently found in lake sediments, but very few studies have used them as palaeoclimate and palaeolimnological indicators. This study explored the species composition of Pediastrum assemblages in shallow floodplain lakes in northern Germany during two transitional periods from cold to temperate climate conditions (GS-2/GI-1 and GI-1/Holocene). We identified Pediastrum taxa to subspecies level and used multivariate statistics (constrained clustering, principal component analysis and redundancy analysis) to show that shifts in taxonomic composition reflected the strong Late Glacial climate oscillations. The Pediastrum assemblages indicate that climate amelioration already begun shortly before the main GS-2/GI-1 summer-temperature transition. In contrast to previous studies that identified trophic state as the main driver of change in Pediastrum species composition, we identified climate shifts and related factors as the major drivers of community change. Water depth and trophic state probably acted as secondary factors that were responsible for differences in Pediastrum response between the first and second investigated climate transitions. During cold periods, Pediastrum algae composition was controlled mainly by environmental variables, whereas during warm periods, Pediastrum assemblages may have been influenced to a greater extent by intra- and intergeneric competition. This study contributes to knowledge about ecological niches of Pediastrum species. Size-measurements on Pediastrum coenobia reveal that one response of Pediastrum algae to climate shifts probably was size change. Coenobia of Pseudopediastrum boryanum var. boryanum were significantly smaller during cold climate periods than during temperate periods. The shifts in Pediastrum species composition and coenobium size suggest this algae group has great potential for enabling palaeoecological and palaeoclimate inferences. 相似文献
26.
Melanie Beck Jürgen Köster Bert Engelen Jan M. Holstein Antje Gittel Martin Könneke Thomas Riedel Kai Wirtz Heribert Cypionka Jürgen Rullkötter Hans-Jürgen Brumsack 《Ocean Dynamics》2009,59(2):371-383
Microbial activity in permeable tidal flat margin sediments is enhanced by two main processes. First, organic matter is supplied
by rapid sedimentation at prograding tidal flat margins. Second, surface and deep pore water advection lead to a replenishment
of the dissolved organic matter and sulfate pools. Increasing microbial activity towards the low water line is reflected in
sulfate and methane profiles as well as in total cell numbers, sulfate reduction rates, and remineralization products. The
impact of high sedimentation rates on pore water biogeochemistry is confirmed by inverse modeling reproducing the depth profiles
obtained by measurements. In central parts of the tidal flats, low sedimentation rates and pore water flow velocities limit
microbial activity despite the high availability of electron acceptors for microbial respiration such as sulfate. Therefore,
tidal flat margins with high microbial activity are of special importance for budgeting biogeochemical cycling in tidal flat
areas. 相似文献
27.
Chris?BallhausEmail author Raúl?O.?C.?Fonseca Carsten?Münker Arno?Rohrbach Thorsten?Nagel Iris?M.?Speelmanns Hassan?M.?Helmy Aurelia?Zirner Antje?K.?Vogel Alexander?Heuser 《Contributions to Mineralogy and Petrology》2017,172(8):68
The extreme depletion of the Earth’s mantle in sulfur is commonly seen as a signature of metal segregation from Earth’s mantle to Earth’s core. However, in addition to S, the mantle contains other elements as volatile as S that are hardly depleted relative to the lithophile volatility trend although they are potentially as siderophile as sulfur. We report experiments in metal-sulfide–silicate systems to show that the CI normalized abundances of S, Pb, and Sn in Earth’s mantle cannot be reproduced by element partitioning in Fe ± S–silicate systems, neither at low nor at high pressure. Much of the volatile inventory of the Earth’s mantle must have been added late in the accretion history, when metal melt segregation to the core had become largely inactive. The great depletion in S is attributed to the selective segregation of a late sulfide matte from an oxidized and largely crystalline mantle. Apparently, the volatile abundances of Earth’s mantle are not in redox equilibrium with Earth’s core. 相似文献
28.
The high permeability of sediments and strong near-bottom currents cause seawater to infiltrate the surface layers of Middle
Atlantic Bight shelf deposits. In this study, sandy sediment cores from 11 to 12 m water depth were percolated with filtered
seawater on shipboard. Sedimentary oxygen consumption (SOC) increased non-linearly with pore water flow, approaching maximum
rates of 120 mmol m−2 d−1 (May 2001) or 75 mmol m−2 d−1(July 2001). The addition of acetate to the inflowing water promptly enhanced the release of dissolved inorganic carbon (DIC)
from the cores. DIC production rates were a linear function of acetate concentration, ranging from 100 to 300 mmol m−2 d−1 without substrate addition to 572 mmol m−2 d−1 with 100 mM acetate. The sediments also hydrolyzed a glucose pseudopolymer, and the liberated glucose prompted an increase
of SOC. Our results suggest that decomposition rates of organic matter in permeable sands can exceed those of fine-grained,
organic-rich deposits, when water currents cause advective interstitial flow, supplying the subsurface microbial community
with degradable material and electron acceptors. We conclude that the highly permeable sand beds of the Middle Atlantic Bight
are responsive within minutes to hours and efficiently operate as biocatalytical filters. 相似文献
29.
Dirk?FreiEmail author Axel?Liebscher Antje?Wittenberg Cliff?S.?J.?Shaw 《Contributions to Mineralogy and Petrology》2003,146(2):192-204
We have experimentally determined the partitioning of REE (rare earth elements) between zoisite and hydrous silicate melt at 1,100 °C and 3 GPa. All REE behave moderately compatible in zoisite with respect to the melt and all
show a smooth parabolic dependence on ionic radius. The partitioning parabola peaks at Nd
, and the compatibility slightly decreases towards La
and decreases by half an order of magnitude towards Yb
. Application of the elastic strain model of Blundy and Wood (1994) to the available zoisite and allanite REE mineral/melt partitioning data and comparison with partitioning pattern calculated from a combination of structural and physical data (taken from the literature) with the elastic strain model suggest that in zoisite REE prefer the A1-site and that only La and Ce are incorporated into the A2-site in significant amounts. In contrast, in allanite, all REE are preferentially incorporated into the large and highly co-ordinated A2 site. As a result, zoisite fractionates the MREE effectively from the HREE and moderately from the LREE, while allanite fractionates the LREE very effectively from the MREE and HREE. Consequently, the presence of either zoisite or allanite during slab melting will lead to quite different REE pattern in the produced melt.Editorial responsibility: J. Hoefs 相似文献
30.
Kakuschke A Valentine-Thon E Griesel S Fonfara S Siebert U Prange A 《Marine pollution bulletin》2011,62(8):1891-1894
Environmental exposure to metals is believed to affect marine mammal health adversely including immunosuppression or acute as well as chronic inflammatory processes leading to hypersensitivities or autoimmune diseases. Metal-specific hypersensitivities were found in several pinnipeds of the North Sea. However, hypersensitivity is a complex phenomenon whose characteristics are still not completely understood; in particular, effects on health are not well established. In the present study, we compared basic hematological and biochemical parameters of seals with and without metal-specific hypersensitivities. We found altered hematological parameters and liver enzyme patterns in seals with a metal-induced hypersensitivity, including a reduction in macrophages, an increase in lymphocytes, and elevated levels of lactate dehydrogenase. These findings support the suggestion of a chronic influence of metal pollutants on the health of marine mammals of the North Sea. 相似文献