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M Water Depth (m + water_depth)
Selected AbstractsA novel, multi-layered methanotrophic microbial mat system growing on the sediment of the Black SeaENVIRONMENTAL MICROBIOLOGY, Issue 8 2008Martin Krüger Summary A novel microbially diverse type of 1- to 5-cm-thick mat performing anaerobic oxidation of methane (AOM) and covering several square metres of the seafloor was discovered in the Black Sea at 180 m water depth. Contrary to other AOM-mat systems of the Black Sea these floating mats are not associated to free gas and are not stabilized by authigenic carbonates. However, supply of methane is ensured by the horizontal orientation of the mats acting as a cover of methane enriched fluids ascending from the underlying sediments. Thorough investigation of their community composition by molecular microbiology and lipid biomarkers, metabolic activities and elemental composition showed that the mats provide a clearly structured system with extracellular polymeric substances (EPS) building the framework of the mats. The top black zone, showing high rates of AOM (15 ,mol gdw,1 day,1), was dominated by ANME-2, while the following equally active pink layer was dominated by ANME-1 Archaea. The lowest AOM activity (2 ,mol gdw,1 day,1) and cell numbers were found in the greyish middle part delimited towards the sediment by a second pink, ANME-1-dominated and sometimes a black outer layer (ANME-2). Our work clearly shows that the different microbial populations are established along defined chemical gradients such as methane, sulfate or sulfide. [source] AVO investigations of shallow marine sedimentsGEOPHYSICAL PROSPECTING, Issue 2 2001M. Riedel Amplitude-variation-with-offset (AVO) analysis is based on the Zoeppritz equations, which enable the computation of reflection and transmission coefficients as a function of offset or angle of incidence. High-frequency (up to 700 Hz) AVO studies, presented here, have been used to determine the physical properties of sediments in a shallow marine environment (20 m water depth). The properties that can be constrained are P- and S-wave velocities, bulk density and acoustic attenuation. The use of higher frequencies requires special analysis including careful geometry and source and receiver directivity corrections. In the past, marine sediments have been modelled as elastic materials. However, viscoelastic models which include absorption are more realistic. At angles of incidence greater than 40°, AVO functions derived from viscoelastic models differ from those with purely elastic properties in the absence of a critical angle of incidence. The influence of S-wave velocity on the reflection coefficient is small (especially for low S-wave velocities encountered at the sea-floor). Thus, it is difficult to extract the S-wave parameter from AVO trends. On the other hand, P-wave velocity and density show a considerably stronger effect. Attenuation (described by the quality factor Q) influences the reflection coefficient but could not be determined uniquely from the AVO functions. In order to measure the reflection coefficient in a seismogram, the amplitudes of the direct wave and the sea-floor reflection in a common-midpoint (CMP) gather are determined and corrected for spherical divergence as well as source and streamer directivity. At CMP locations showing the different AVO characteristics of a mud and a boulder clay, the sediment physical properties are determined by using a sequential-quadratic-programming (SQP) inversion technique. The inverted sediment physical properties for the mud are: P-wave velocity ,=1450±25 m/s, S-wave velocity ,=90±35 m/s, density ,=1220±45 kg/m3, quality factor for P-wave QP=15±200, quality factor for S-wave QS=10±30. The inverted sediment physical properties for the boulder clay are: ,=1620±45 m/s,,=360±200 m/s,,=1380±85 kg/m3,QP=790±660,QS=25±10. [source] Comparative thermal performance evaluation of an active solar distillation systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2007G. N. Tiwari Abstract In this paper, thermal models of all types of solar collector-integrated active solar stills are developed based on basic energy balance equations in terms of inner and outer glass temperatures. In this paper, hourly yield, hourly exergy efficiency, and hourly overall thermal efficiency of active solar stills are evaluated for 0.05 m water depth. All numerical computations had been performed for a typical day in the month of 07 December 2005 for the climatic conditions of New Delhi (28°35,N, 77°12,E, 216 m above MSL). The thermal model of flat-plate collector integrated with active solar still was validated using the experimental test set-up results. Total daily yield from active solar still integrated with evacuated tube collector with heat pipe is 4.24 kg m,2 day,1, maximum among all other types of active solar stills. Copyright © 2007 John Wiley & Sons, Ltd. [source] Variability in temperature and geometry of the Norwegian Current over the past 600,yr; stable isotope and grain size evidence from the Norwegian marginJOURNAL OF QUATERNARY SCIENCE, Issue 7 2003Ida Malene Berstad Abstract Core P1-003MC was retrieved from 851,m water depth on the southern Norwegian continental margin, close to the boundary between the Norwegian Current (NC) and the underlying cold Norwegian Sea Deep Water. The core chronology was established by using 210Pb measurements and 14C dates, suggesting a sampling resolution of between 2 and 9,yr. Sea-surface temperature (SST) variations in the NC are reconstructed from stable oxygen isotope measurements in two planktonic Foraminifera species, Neogloboquadrina pachyderma (d.) and Globigerina bulloides. The high temporal resolution of the SST proxy records allows direct comparison with instrumental ocean temperature measurements from Ocean Weather Ship (OWS) Mike in the Norwegian Sea and an air temperature record from the coastal island Ona, western Norway. The comparison of the instrumental and the proxy SST data suggests that N. pachyderma (d.) calcify during summer, whereas G. bulloides calcify during spring. The ,18O records of both species suggest that the past 70,yr have been the warmest throughout the past 600,yr. The spring and summer proxy temperature data suggest differences in the duration of the cold period of the Little Ice Age. The spring temperature was 1,3°C colder throughout most of the period between ca. AD 1400 and 1700, and the summer temperature was 1,2°C colder throughout most of the period between ca. AD 1400 and 1920. Fluctuations in the depth of the lower boundary of the NC have been investigated by examining grain size data and benthic foraminiferal assemblages. The data show that the transition depth of the lower boundary of the NC was deeper between ca. AD 1400 and 1650 than after ca. AD 1750 until present. Copyright © 2003 John Wiley & Sons, Ltd. [source] Microbial colonisation of artificial and deep-sea sediments in the Arctic OceanMARINE ECOLOGY, Issue 4 2009Corinna Kanzog Abstract Although environmental factors such as grain size and organic carbon content may influence the distribution of microbes in marine sediments, there has been little experimental study of the topic to date. To investigate how those sediment variables affect microbial colonisation under in situ conditions, deep-sea sediments and artificial sediments (glass beads, sands) were incubated in the Arctic deep sea at 2500 m water depth with or without chitin, one of the most important carbon polymers in marine environments. Microbial abundance, biomass, chitobiase activity and changes in community structure were monitored after 7 days and 1 year. In control sediments without chitin addition, no significant changes in microbial abundance, biomass and activity were observed after 1 year. In the presence of chitin, however, considerable increases in these parameters were recorded in all three sediment types tested. Regardless of chitin addition, natural deep-sea sediments were always associated with higher values of microbial abundance, biomass and activity compared with artificial sediments. Sediment type was always found to be the most significant factor explaining variation in enzymatic activity and bacterial community structure as compared to the effects of chitin amount, incubation time, and changes in cell number or biomass. Overall, this is the first in situ study that has addressed the effects of multiple factors and their interactions on abundance, biomass, activity and community structure of microbial communities in the deep Arctic Ocean. [source] TAXONOMY OF QUATERNARY DEEP-SEA OSTRACODS FROM THE WESTERN NORTH ATLANTIC OCEANPALAEONTOLOGY, Issue 4 2009MORIAKI YASUHARA Abstract:, Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32°47.041, N, 76°17.179, W; 1798 m water depth) were examined for deep-sea ostracod taxonomy. A total of 13 933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. [source] Biotic affinities of rocky reef fishes, invertebrates and macroalgae in different zones of the Port Davey marine protected area, south-western TasmaniaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2010Graham J. Edgar Abstract 1.Assemblages of fishes, invertebrates, and macroalgae showed strong and predictable distributional patterns within the newly declared Port Davey marine protected area (MPA) in south-western Tasmania. Biotic assemblages in the eastern estuarine section of the MPA within Bathurst Channel were extremely anomalous, both in relation to biota elsewhere in the Port Davey region and also to those present along the wider Tasmanian and Australian coasts. Much of this variation was due to the phenomenon of deepwater emergence, with species in 5,m water depth in eastern Bathurst Channel possessing a mean maximum recorded depth of 200,m, compared with<80,m for the same metric when calculated for sites studied elsewhere around Australia. Deepwater emergence in Bathurst Channel was particularly notable for sessile organisms, although also evident among fishes and mobile macro-invertebrates. 2.Quantitative baseline surveys of reef-associated species were undertaken at sites interspersed among MPA management zone types and biotic community types, thereby providing an appropriate benchmark for assessing ecological changes in different management zones within the Port Davey region through the long term. Distinctive biota present in eastern and western Bathurst Channel, and eastern Port Davey, are well protected within ,no-take' sanctuary zones; however, a bias in location of sanctuary zones towards areas with little fishery resources resulted in less protection for the western Port Davey biota, which also extends along the open coast. Although the lack of high level protection for sites with fishery resources detracts from conservation goals, the Port Davey MPA nevertheless represents a major advance in environmental protection because the ecologically unique, fully protected locations are a necessary inclusion within any comprehensive Australian MPA network. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||