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31.
George G. Waldbusser Erin P. Voigt Heather Bergschneider Mark A. Green Roger I. E. Newell 《Estuaries and Coasts》2011,34(2):221-231
Anthropogenic carbon dioxide (CO2) emissions reduce pH of marine waters due to the absorption of atmospheric CO2 and formation of carbonic acid. Estuarine waters are more susceptible to acidification because they are subject to multiple
acid sources and are less buffered than marine waters. Consequently, estuarine shell forming species may experience acidification
sooner than marine species although the tolerance of estuarine calcifiers to pH changes is poorly understood. We analyzed
23 years of Chesapeake Bay water quality monitoring data and found that daytime average pH significantly decreased across
polyhaline waters although pH has not significantly changed across mesohaline waters. In some tributaries that once supported
large oyster populations, pH is increasing. Current average conditions within some tributaries however correspond to values
that we found in laboratory studies to reduce oyster biocalcification rates or resulted in net shell dissolution. Calcification
rates of juvenile eastern oysters, Crassostrea virginica, were measured in laboratory studies in a three-way factorial design with 3 pH levels, two salinities, and two temperatures.
Biocalcification declined significantly with a reduction of ∼0.5 pH units and higher temperature and salinity mitigated the
decrease in biocalcification. 相似文献
32.
33.
We describe for the first time the generation and measurement of capillary waves in a water surface in a wind tunnel running with air at pressures of 15-1000 mbar. These experiments suggest a stronger dependence of wave generation on atmospheric density than the simple proportionality that might be expected from energy transfer arguments. Additionally, airflow over a nonaqueous fluid (kerosene) was found to produce waves of higher amplitude than for water under the same conditions. These preliminary results may indicate different efficiencies of wave generation on other planets, for which empirical terrestrial relations therefore do not apply, and thus may have a bearing on the lack of strong shoreline features on Mars and the possibility of specular glints from hydrocarbon lakes on Titan. 相似文献
34.
W.A. Martin S.L. Larson D.R. Felt J. Wright C.S. Griggs M. Thompson J.L. Conca C.C. Nestler 《Applied Geochemistry》2008
Training activities at firing ranges, both civilian and military, deliver large quantities of Pb bullets into range soils where the physical and geochemical properties of the soil can influence Pb transport. Some best management practices (BMPs) developed for range managers include the addition of phosphate amendments, such as apatite, to immobilize Pb and other metals associated with firing ranges. In this study, the effect of the organic matter content of apatite II™ on its metal sorption properties was investigated. Batch and column experiments were conducted using mechanically, enzymatically, and thermally-treated forms of Apatite II™ to sorb soluble Pb. In batch experiments, mechanically and enzymatically-treated Apatite II™ reduced soluble Pb concentrations from 29% to 96%, depending on the age of the Apatite source. Thermally-treated Apatite II™ consistently reduced soluble Pb concentrations in solution by more than 90%, regardless of aging. The mechanically and enzymatically-treated Apatite II™ produced significantly higher dissolved organic carbon (DOC) and biochemical oxygen demand (BOD) concentrations while undergoing aging. This contrasts with the thermally-treated Apatite II™ that produced very low to non-detectable levels of DOC and BOD while aging. To determine the effects of thermal treatment on performance efficiencies, studies were performed using 500 mg L−1 Pb solutions in columns packed with Apatite II™ that had been preheated at various temperatures for 2 h. The column study showed Pb loading of the Apatite II™ at different thermal treatments that ranged from 10.5% to 16.8% Pb by weight of substrate. The Pb loading capacity (by weight of substrate) increased as the treatment temperature of the Apatite II™ increased. 相似文献
35.
Species‐specific photosynthetic responses of symbiotic zoanthids to thermal stress and ocean acidification
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Increasing sea‐surface temperatures and ocean acidification (OA) are impacting physiologic processes in a variety of marine organisms. Many sea anemones, corals and jellies in the phylum Cnidaria form endosymbiotic relationships with Symbiodinium spp. (phylum Dinoflagellata) supply the hosts with fixed carbon from photosynthesis. Much work has focused on the generally negative effects of rising temperature and OA on calcification in Symbiodinium‐coral symbioses, but has not directly measured symbiont photosynthesis in hospite or fixed carbon translocation from symbiont to host. Symbiodinium species or types vary in their environmental tolerance and photosynthetic capacity; therefore, primary production in symbiotic associations can vary with symbiont type. However, symbiont type has not been identified in a large portion of Symbiodinium?cnidarian studies. Future climate conditions and OA may favor non‐calcifying, soft‐bodied cnidarians, including zoanthids. Here we show that two zoanthid species, Palythoa sp. and Zoanthus sp., harboring different symbiont types (C1 and A4), had very different responses to increased temperature and increased partial pressure of CO2 (pCO2), or dissolved CO2, and low pH. Thermal stress did not affect carbon fixation or fixed carbon translocation in the Zoanthus sp./A4 association, and high pCO2/low pH increased carbon fixation. In contrast, both thermal stress and high pCO2/low pH greatly inhibited carbon fixation in the Palythoa sp./C1 association. However, the combined treatment of high temperature and high pCO2 increased carbon fixation relative to the treatment of high temperature alone. Our observations support the growing body of evidence that demonstrates that the response of symbiotic cnidarians to thermal stress and OA must be considered on a host‐specific and symbiont‐specific basis. In addition, we show that the effects of increased temperature and pCO2 on photosynthesis may change when these two stressors are combined. Understanding how carbon fixation and translocation varies among different host?symbiont combinations is critical to predicting which Symbiodinium associations may persist in warm, acidified oceans. 相似文献
36.
The objectives of this study were to determine the distribution and abundance of Zostera marina (eelgrass) in relation to the distribution of the mat forming bacteria Beggiatoa spp., and the levels of sulfide and organic material (wood waste) in the sediment. Underwater videography and intertidal surveys were used to map the distribution and abundance of Z. marina beds and Beggiatoa in the nearshore area of Commencement Bay, WA (USA), a location that has a long history of sawmill activity. Zostera marina occurred from the intertidal to ?6 m mean lower low water (MLLW) on sandy substrates in areas with low levels of sulfide (<50 μm ) and organic material (<5 % total volatile solids). Areas with high sulfide levels (>200 μm ) occurred where there were significant amounts of organic material in the sediments, which was found to be wood waste that had been discarded from sawmills. Zostera marina was absent from the intertidal and occurred at lower densities in areas with high sulfide levels. In contrast, mats of Beggiatoa were only found in areas where the sulfide levels were >1000 μm and there were significant deposits of wood. Thus, the negative correlation between the distribution and abundance of Z. marina and Beggiatoa suggests that the presence of Beggiatoa mats could be used as a biological indicator of inhibiting levels of hydrogen sulfide in the marine environment. 相似文献
37.
Erin F. Owen Alan D. Wanamaker Jr. Bernd R. Schöne 《Geochimica et cosmochimica acta》2008,72(19):4687-4698
The relationship between stable isotope composition (δ13C and δ18O) in seawater and in larval shell aragonite of the sea scallop, Placopecten magellanicus, was investigated in a controlled experiment to determine whether isotopes in larval shell aragonite can be used as a reliable proxy for environmental conditions. The linear relationship between δ13CDIC and δ13Caragonite (r2 = 0.97, p < 0.0001, RMSE = 0.18) was:
δ13CDIC=1.15(±0.05)∗δ13Caragonite-0.85(±0.04) 相似文献
38.
Chromophoric dissolved organic matter (CDOM) spectral absorption, dissolved organic carbon (DOC) concentration, and the particulate fraction of inorganic (PIM) and organic matter (POM) were measured in Louisiana coastal waters at Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi River locations, in 2007-2008. The range of CDOM was 0.092 m−1 at Barataria in June 2008 to 11.225 m−1 at Mississippi in February 2008. An indicator of organic matter quality was predicted by the spectral slope of absorption coefficients from 350 to 412 nm which was between 0.0087 m−1 at Mississippi in May 2008 and 0.0261 m−1 at Barataria in June 2008. CDOM was the dominant component of light attenuation at Terrebonne and Barataria. Detritus and CDOM were the primary components of light attenuation at Vermilion, Atchafalaya, and Mississippi. DOC ranged between 65 and 1235 μM. PIM ranged between 1.1 and 426.3 mg L−1 and POM was between 0.3 and 49.6 mg L−1. 相似文献
39.
Deconvolving the pre-Himalayan Indian margin-Tales of crustal growth and destruction 总被引:1,自引:0,他引:1
Christopher J.Spencer Brendan Dyck Catherine M.Mottram Nick M.W.Roberts Wei-Hua Yao Erin L.Martin 《地学前缘(英文版)》2019,10(3):863-872
The metamorphic core of the Himalaya is composed of Indian cratonic rocks with two distinct crustal affinities that are defined by radiogenic isotopic geochemistry and detrital zircon age spectra. One is derived predominantly from the Paleoproterozoic and Archean rocks of the Indian cratonic interior and is either represented as metamorphosed sedimentary rocks of the Lesser Himalayan Sequence(LHS) or as slices of the distal cratonic margin. The other is the Greater Himalayan Sequence(GHS) whose provenance is less clear and has an enigmatic affinity. Here we present new detrital zircon Hf analyses from LHS and GHS samples spanning over 1000 km along the orogen that respectively show a striking similarity in age spectra and Hf isotope ratios. Within the GHS, the zircon age populations at 2800-2500 Ma,1800 Ma, 1000 Ma and 500 Ma can be ascribed to various Gondwanan source regions; however, a pervasive and dominant Tonianage population(~860-800 Ma) with a variably enriched radiogenic Hf isotope signature(eHf = 10 to-20) has not been identified from Gondwana or peripheral accreted terranes. We suggest this detrital zircon age population was derived from a crustal province that was subsequently removed by tectonic erosion. Substantial geologic evidence exists from previous studies across the Himalaya supporting the Cambro-Ordovician Kurgiakh Orogeny. We propose the tectonic removal of Tonian lithosphere occurred prior to or during this Cambro-Ordovician episode of orogenesis in a similar scenario as is seen in the modern Andean and Indonesian orogenies, wherein tectonic processes have removed significant portions of the continental lithosphere in a relatively short amount of time. This model described herein of the pre-Himalayan northern margin of Greater India highlights the paucity of the geologic record associated with the growth of continental crust. Although the continental crust is the archive of Earth history, it is vital to recognize the ways in which preservation bias and destruction of continental crust informs geologic models. 相似文献
40.
Michael M. McGlue Aguinaldo Silva Hiran Zani Fabrício A. Corradini Mauro Parolin Erin J. Abel Andrew S. Cohen Mario L. Assine Geoffrey S. Ellis Mark A. Trees Sidney Kuerten Frederico dos Santos Gradella Giliane Gessica Rasbold 《Quaternary Research》2012,78(2):285-294
The Pantanal is the world's largest tropical wetland and a biodiversity hotspot, yet its response to Quaternary environmental change is unclear. To address this problem, sediment cores from shallow lakes connected to the Upper Paraguay River (PR) were analyzed and radiocarbon dated to track changes in sedimentary environments. Stratal relations, detrital particle size, multiple biogeochemical indicators, and sponge spicules suggest fluctuating lake-level lowstand conditions between ~ 11,000 and 5300 cal yr BP, punctuated by sporadic and in some cases erosive flood flows. A hiatus has been recorded from ~ 5300 to 2600 cal yr BP, spurred by confinement of the PR within its channel during an episode of profound regional drought. Sustained PR flooding caused a transgression after ~ 2600 cal yr BP, with lake-level highstand conditions appearing during the Little Ice Age. Holocene PR flood pulse dynamics are best explained by variability in effective precipitation, likely driven by insolation and tropical sea-surface temperature gradients. Our results provide novel support for hypotheses on: (1) stratigraphic discontinuity of floodplain sedimentary archives; (2) late Holocene methane flux from Southern Hemisphere wetlands; and (3) pre-colonial indigenous ceramics traditions in western Brazil. 相似文献