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941.
942.
Valeria A. Guinder Juan Carlos Molinero Celeste M. López Abbate Anabela A. Berasategui Cecilia A. Popovich Carla V. Spetter Jorge E. Marcovecchio Rubén H. Freije 《Estuaries and Coasts》2017,40(1):95-104
Understanding phytoplankton species-specific responses to multiple biotic and abiotic stressors is fundamental to assess phenological and structural shifts at the community level. Here, we present the case of Thalassiosira curviseriata, a winter-blooming diatom in the Bahía Blanca Estuary, Argentina, which displayed a noticeable decrease in the past decade along with conspicuous changes in phenology. We compiled interannual field data to assess compound effects of environmental variations and grazing by the invasive copepod Eurytemora americana. The two species displayed opposite trends over the period examined. The diatom decreased toward the last years, mainly during the winters, and remained relatively constant over the other seasons, while the copepod increased toward the last years, with an occurrence restricted to winter and early spring. A quantitative assessment by structural equation modeling unveiled that the observed long-term trend of T. curviseriata resulted from the synergistic effects of environmental changes driven by water temperature, salinity, and grazing. These results suggest that the shift in the abundance distribution of T. curviseriata toward higher annual ranges of temperature and salinity—as displayed by habitat association curves—constitutes a functional response to avoid seasonal overlapping with its predator in late winters. The observed changes in the timing and abundance of the blooming species resulted in conspicuous shifts in primary production pulses. Our results provide insights on mechanistic processes shaping the phenology and structure of phytoplankton blooms. 相似文献
943.
Bomina Kim Ayeon Choi Kun-Seop Lee Chang-Keun Kang Jung-Ho Hyun 《Estuaries and Coasts》2017,40(5):1346-1357
To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r 2 = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r 2 = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe(oxal) + 1.8180, r 2 = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day?1) was 2.5 times lower than that at the Z. marina bed (0.33 day?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments. 相似文献
944.
On CO<Subscript>2</Subscript> fluid flow and heat transfer behavior in the subsurface,following leakage from a geologic storage reservoir 总被引:1,自引:0,他引:1
Karsten Pruess 《Environmental Geology》2008,54(8):1677-1686
Geologic storage of CO2 is expected to produce plumes of large areal extent, and some leakage may occur along fractures, fault zones, or improperly
plugged pre-existing wellbores. A review of physical and chemical processes accompanying leakage suggests a potential for
self-enhancement. The numerical simulations presented here confirm this expectation, but reveal self-limiting features as
well. It seems unlikely that CO2 leakage could trigger a high-energy run-away discharge, a so-called “pneumatic eruption,” but present understanding is insufficient
to rule out this possibility. The most promising avenue for increasing understanding of CO2 leakage behavior is the study of natural analogues. 相似文献
945.
We present the software program THERIA_G, which allows for numerical simulation of garnet growth in a given volume of rock
along any pressure–temperature–time (P–T–t) path. THERIA_G assumes thermodynamic equilibrium between the garnet rim and the rock matrix during growth and accounts for
component fractionation associated with garnet formation as well as for intracrystalline diffusion within garnet. In addition,
THERIA_G keeps track of changes in the equilibrium phase relations, which occur during garnet growth along the specified P–T–t trajectory. This is accomplished by the combination of two major modules: a Gibbs free energy minimization routine is used
to calculate equilibrium phase relations including the volume and composition of successive garnet growth increments as P and T and the effective bulk rock composition change. With the second module intragranular multi-component diffusion is modelled
for spherical garnet geometry. THERIA_G allows to simulate the formation of an entire garnet population, the nucleation and
growth history of which is specified via the garnet crystal size frequency distribution. Garnet growth simulations with THERIA_G
produce compositional profiles for the garnet porphyroblasts of each size class of a population and full information on equilibrium
phase assemblages for any point along the specified P–T–t trajectory. The results of garnet growth simulation can be used to infer the P–T–t path of metamorphism from the chemical zoning of garnet porphyroblasts. With a hypothetical example of garnet growth in a
pelitic rock we demonstrate that it is essential for the interpretation of the chemical zoning of garnet to account for the
combined effects of the thermodynamic conditions of garnet growth, the nucleation history and intracrystalline diffusion.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
F. GaidiesEmail: |
946.
Jong-Sun Kim Moon Son Byoung-Hoon Hwang Ki-Cheol Shin Hyeongseong Cho Young Kwan Sohn 《Mineralogy and Petrology》2014,108(2):207-229
Petrographic and geochemical features of the Cretaceous Yucheon granites and their mafic microgranular/magmatic enclaves (MMEs), SE Korea, reveal that the MMEs originated from magma mixing. Mesoscopic and microscopic features indicate that mechanical mixing operated heterogeneously to produce the MMEs with a wide range of sizes and textures. Chemical compositions of amphibole, biotite, and plagioclase rims of both the MMEs and host granites are almost identical, indicating that chemical homogenization took place to some extent after the mechanical mixing. Plagioclase cores, however, have various compositions depending on the host rocks and/or sampling locations, suggesting their sluggish re-equilibration. The MMEs are divided into Type A (low TiO2, very fine-grained, chilled margins) and Type B (high TiO2, fine- to medium-grained, no chilled margins). The lower TiO2 MMEs cooled more rapidly and interacted with granitic magma for a shorter period of time than the higher TiO2 MMEs. Additionally, the former are less enriched in HREEs than the latter. Zoned plagioclase has two zones of increased An content. These features are indicative of double injection events of mafic magma. A previous model explains the magma mixing as resulting from the generation of a slab window due to Kula-Pacific ridge subduction. The model cannot, however, explain the eastward younging of the granites in Korea, necessitating a new, more elaborate model of Cretaceous geodynamics and magmatism in East Asia. 相似文献
947.
The Samborombon Bay wetland is located on the west margin of the Rio de la Plata estuary, in the Province of Buenos Aires,
Argentina. This paper analyses the geological, geomorphologic, soil and vegetation characteristics of the southernmost sector
of this wetland and their influence on surface water and groundwater. The study area presents three hydrologic units: coastal
dunes, sand sheets and coastal plain. Coastal dunes and sand sheets are recharge zones of high permeability with well-drained,
non-saline soils, and a few surface water flows. Changes in the water table are related to rainfall. Groundwater in coastal
dunes is Ca–Mg–HCO3 to Na–HCO3, and of low salinity (590 mg/l). Groundwater in sand sheets is mainly Na–HCO3 with a salinity of about 1,020 mg/l. The coastal plain exhibits medium to low permeability sediments, with submerged saline
soils poorly drained. Groundwater is Na–Cl with a mean salinity of 16,502 mg/l. A surface hydrological network develops in
the coastal plain. Surface water levels near the shoreline are affected by tidal fluctuations; far from the shoreline water
accumulates because of poor drainage. Both sectors have Na–Cl water, but the former is more saline. Human intervention and
sea level rise may affect the wetland severely. 相似文献
948.
Bivalved arthropods are very important elements in Mid-Cambrian Kaili Biota.Three genera,Alicaris,Pseudoarctolepis,and Forfexicaris,are herein recorded for the first time,including three new species:Alicaris kailiensis sp.nov.,Forfexicaris reticulata sp.nov.,and Pseudoarctolepis semicircularis sp.nov.,of which Alicaris kailiensis sp.nov.could be assigned to crustaceomorphs;the other two forms are grouped as proschizoramians.These forms provide important information about the distribution and species dive... 相似文献
949.
Quantitative modeling of groundwater in Satluj River basin of Rupnagar district of Punjab using remote sensing and geographic information system 总被引:2,自引:1,他引:2
Chander Kumar Singh Satyanarayan Shashtri Amit Singh Saumitra Mukherjee 《Environmental Earth Sciences》2011,62(4):871-881
Water is a fluctuating resource making it difficult to measure in time and in space. To demonstrate the efficiency of the
geographic information system (GIS) for groundwater studies, information on the parameters controlling groundwater such as
lithology, geomorphology and lineament analysis were analyzed. LISS-III and Landsat satellite image of the area was used to
infer information on the geologic lineaments and geomorphology. To delineate linear features enhancement and direction, filtering
was performed on single bands of Landsat images. Thematic maps for geology, slope, geomorphology and lineament were prepared
and integrated in GIS by assigning the weights and ranking to various parameters controlling the occurrence of groundwater
to generate the groundwater potential map for the study area. The results indicate that the floodplain of river and its adjoining
areas have very good groundwater potential, whereas the steeply sloping area in the northern part having high relief and slope
possesses poor groundwater potential. 相似文献
950.