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401.
Scott D. Woodruff Henry F. Diaz Steven J. Worley Richard W. Reynolds Sandra J. Lubker 《Climatic change》2005,73(1-2):169-194
Many surface marine meteorological observations (∼125 million) from ships' logbooks have been assembled in the International
Comprehensive Ocean-Atmosphere Data Set (ICOADS) back to the late 18th century. We describe the makeup of the available data
before 1950, and a recent update for that period incorporating a variety of US and international sources – focusing on the
background, digitization, and processing of the US Maury Collection, which provides the earliest data (mainly 1830–1860) currently
blended into ICOADS. We also describe planned data and metadata additions to early ICOADS. Among these, the new Climatological
Database for the World's Oceans (CLIWOC) will extend and enhance coverage for 1750–1854. Prospects for data improvements and
homogeneity enhancements to further benefit climate research are also discussed. 相似文献
402.
Maria Li. Calleja Cristina Barrón Jason A. Hale Thomas K. Frazer Carlos M. Duarte 《Estuaries and Coasts》2006,29(6):1255-1264
The effects of light reduction on community metabolism and sediment sulfate reduction rates (SRR) were assessed experimentally
in a shallow (<2.0 m) seagrass (Thalassia testudinum) meadow along Florida's north-central Gulf coast. Nine experimental plots (1.5 m×1.5 m) were shaded differentially to achieve
a 0–90% gradient in light reduction within the seagrass meadow. Gross primary production and net community production (NCP),
estimated with in situ benthic chamber incubations, decreased with increasing light reduction. The compensation irradiance
for community metabolism, i.e., the shading level at which NCP shifted from net autotrophic to net heterotrophic, was determined
to be 52.5% of the incoming irradiance at canopy height in the seagrass bed (308.7 μE m−2 s−1 PAR at noon). Sediment SRR, determined with the use of a35S−SO4
2− radiotracer technique, increased quickly (within 5 d) and markedly with increased shade, i.e., simulated light reduction.
SRR increased 50-fold when shading exceeded the light compensation point for the seagrass community, rendering the community
net heterotrophic. Five days after restoring ambient light conditions, SRR had decreased sharply for all shading treatments.
The observed decrease in NCP, coincident with the increase in the SRR with light reduction, suggests that light reduction
has an indirect influence on sediment SRR mediated through its effect on seagrass metabolism. 相似文献
403.
Cristina Barrón Carlos M. Duarte Michel Frankignoulle Alberto Vieira Borges 《Estuaries and Coasts》2006,29(3):417-426
We measured monthly dissolved oxygen (DO) changes in situ benthic incubations from March 2001 to October 2002 in aPosidonia oceanica meadow and unvegetated sediments of Magalluf Bay (Mallorca Island, Spain) to determine gross primary production (GPP), community
respiration (R), and net community production (NCP). From June 2001 to October 2002, we also measured fluxes of dissolved
inorganic carbon (DIC) and total alkalinity (TAlk). The yearly integrated metabolic rates based on DO changes show that theP. oceanica communities are net autotrophic while the metabolic rates in the unvegetated benthic communities are nearly balanced. Higher
calcium carbonate (CaCO3) cycling, both in terms of production and dissolution, was observed inP. oceanica communities than in unvegetated benthic communities. In theP. oceanica meadow, the annual release of CO2 from net CaCO3 production corresponds to almost half of the CO2 uptake by NCP based on DIC incubations. In unvegetated benthic communities, the annual uptake of CO2 from net CaCO3 dissolution almost fully compensates the CO2 release by NCP based on DIC incubations. CaCO3 dynamics is potentially a major factor in CO2 benthic fluxes in seagrass and carbonate-rich temperate coastal ecosystems. 相似文献
404.
Peter Sjövall Volker Thiel Sandra Siljeström Christine Heim Tomas Hode Jukka Lausmaa 《Geostandards and Geoanalytical Research》2008,32(3):267-277
Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is a powerful method for the chemical analysis of solid surfaces. In this paper, the capabilities and limitations of this technique and the potential for its use in geochemical research are outlined. Using ToF‐SIMS, the chemical composition of sample structures down to 10–100 μm can be determined, without the need for pre‐selection or labelling of the analysed substances. In addition, the lateral distribution of organic and inorganic compounds can be mapped in geochemical samples at a resolution in the micrometre range. The capabilities of the technique in geochemistry are illustrated by two examples. In the first example, it is shown that ToF‐SIMS can be used to detect biomarkers in oil samples, making it a promising method for the analysis of biomarkers in fluid inclusions. In the second example, a number of specific lipid biomarkers were identified and mapped on the surface of a microbial mat cryosection surface. Post‐measurement optical microscopy correlated the localisation of the lipids with the presence of methanotrophic archaea in the microbial mat. 相似文献
405.
Berlaine Ortega-Flores Michelangelo Martini Luigi Solari Vanessa Colás Sandra Guerrero-Moreno Elena Centeno-Garcia 《International Geology Review》2020,62(4):421-427
ABSTRACTThe origin of the Oligocene turbidites from the Cerro Pelón area in south Gulf Mexico proposed by Ortega-Flores et al. (2018) is in disagree with the interpretations made by Molina-Garza et al. (2019), which main criticism is based on U-Pb ages of detrital zircons from the matrix of a conglomerate unit, which they refer to as ‘Nanchital Conglomerate’, as well as on the presence of limestone, gabbros, and mafic protolith-derived clasts. Molina-Garza et al. (2019) basically interpret the Nanchital Conglomerate as Miocene in age, which was sourced mainly from metamorphic complexes including their sedimentary covers located to the west and south of the Cerro Pelón area. For some reason, Molina-Garza et al. (2019) suppose that the Nanchital Conglomerate should have the same provenance sources that the Oligocene turbidites from Cerro Pelón area, reported by Ortega-Flores et al. (2018). Based on the foregoing, we strongly disagree with Molina-Garza et al. (2019) considering that, from the beginning, they intend to compare two units of different age. Additionally, the scarce data reported from both the matrix and the clasts of the Nanchital Conglomerate are not determinant for interpreting the provenance of this conglomeratic unit and subsequently, to consider the same rock sources from the Oligocene through Miocene time. 相似文献
406.
Settlement and colonization of epi‐endobenthic communities on calcareous substrata in an underwater archaeological site
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Edoardo Casoli Sandra Ricci Andrea Belluscio Maria Flavia Gravina Giandomenico Ardizzone 《Marine Ecology》2015,36(4):1060-1074
Underwater archaeological sites represent assets of great value that are subjected to physical and biological stresses. The study of biological settlement on calcareous substrata is the first step to understanding the biodeterioration processes that take place on man‐made structures (marble, statues, columns and other architectonic elements) in marine environments. To accomplish this objective, calcareous panels (30 × 30 × 2 cm) were immersed for 3, 6, 9 and 12 months along a north?south transect in marine protected areas of Baia (Naples). Both epilithic and endolithic assemblages were analysed: the latter was observed by scanning electron microscope after the cast‐embedding technique had been used. After 1 year the epilithic community was still changing, with algae and pioneer species overgrown by encrusting organisms, and the endolithic assemblage dominated by cyanobacteria/chlorophyte traces. Changes of epilithics lead changes on endolithics. The initial phototrophic borers were replaced by more sciophilous and competitive species; moreover, the first macroboring organisms arrived after the settlement of grazers. After 12 months of immersion, the rate of bioerosion was high, the material was deeply bored and all of the limestone surface was heavily covered. 相似文献
407.
Sandra K. Richard Romain Chesnaux Alain Rouleau Roger Morin Julien Walter Silvain Rafini 《Hydrogeology Journal》2014,22(8):1889-1904
Field evidence of hydraulic connections between a bedrock aquifer and an overlying granular aquifer in the Canadian Shield (Grenville Province) is presented. This issue is rarely considered and investigated despite its important hydraulic and chemical consequences and its widespread occurrence worldwide. The methodology employed is based on complementary field tests conducted at specific experimental sites instrumented both in the rock and in the overlying deposits. One of the bedrock sites revealed a natural hydraulic connection with the overlying granular aquifer caused by the weathered surface of the uppermost bedrock. Another site revealed an artificial hydraulic connection between the bedrock and the granular aquifer created by an improperly sealed casing. A regional study showed that hydraulic connections yield an erroneous interpretation of the true hydraulic properties of the tested aquifer. The detection of hydraulic connections is therefore essential to properly define well-capture areas and contamination conditions. It is recommended to practitioners that pumping tests be performed as well as hydrochemical comparisons of each existing aquifer unit. Falling-head permeability tests are also helpful in verifying the quality of the seal at the bedrock–casing contact. More effective procedural controls and better well-construction practices are necessary to reduce the risks of cross-contamination induced by defective seals. 相似文献
408.
Mariela A. Yevenes Estrella Bello Sandra Sanhueza-Guevara Laura Farías 《Estuaries and Coasts》2017,40(3):807-821
Fjords and estuaries exchange large amounts of solutes, gases, and particulates between fluvial and marine systems. These exchanges and their relative distributions of compounds/particles are partially controlled by stratification and water circulation. The spatial and vertical distributions of N2O, an important greenhouse gas, along with other oceanographic variables, are analyzed from the Reloncaví estuary (RE) (~41° 30′ S) to the gulf of Corcovado in the interior sea of Chiloé (43° 45′ S) during the austral winter. Freshwater runoff into the estuary regulated salinity and stratification of the water column, clearly demarking the surface (<5 m depth) and subsurface layer (>5 m depth) and also separating estuarine and marine influenced areas. N2O levels varied between 8.3 and 21 nM (corresponding to 80 and 170 % saturation, respectively), being significantly lower (11.8 ± 1.70) at the surface than in subsurface waters in the Reloncaví estuary (14.5 ± 1.73). Low salinity and NO3 ?, NO2 ?, and PO4 3? levels, as well as high Si(OH)4 values were associated with low surface N2O levels. Remarkably, an accumulation of N2O was observed in the subsurface waters of the Reloncaví sound, associated with a relatively high consumption of O2. The sound is exposed to increasing anthropogenic impacts from aquaculture and urban discharge, occurring simultaneously with an internal recirculation, which leads to potential signals of early eutrophication. In contrast, within the interior sea of Chiloé (ISC), most of water column was quasi homohaline and occupied by modified subantarctic water (MSAAW), which was relatively rich in N2O (12.6 ± 2.36 nM) and NO3 ? (18.3 ± 1.63 μM). The relationship between salinity, nutrients, and N2O revealed that water from the open ocean, entering into ISC (the Gulf of Corcovado) through the Guafo mouth, was the main source of N2O (up to 21 nM), as it gradually mixed with estuarine water. In addition, significant relationships between N2O excess vs. AOU and N2O excess vs. NO3 ? suggest that part of N2O is also produced by nitrification. Our results show that the estuarine and marine waters can act as light source or sink of N2O to the atmosphere (air–sea N2O fluxes ranged from ?1.57 to 5.75 μmol m?2 day?1), respectively; influxes seem to be associated to brackish water depleted in N2O that also caused a strong stratification, creating a barrier to gas exchange. 相似文献