Refining P nuclear magnetic resonance spectroscopy for marine particulate samples: Storage conditions and extraction recovery     

Barbara J. Cade-Menun  Claudia R. Benitez-Nelson  Perry Pellechia  Adina Paytan 《Marine Chemistry》2005,97(3-4):293-306

Solution ³¹P nuclear magnetic resonance (NMR) spectroscopy has recently been used to characterize phosphorus species within marine particles. However, the effects of sample collection, storage and preparation have not been thoroughly examined. In this study, samples of settling particulates collected from a 1200-m sediment trap located in Monterey Bay, California, were subjected to various storage options (i.e., no storage, refrigeration, freezing, and oven-drying and grinding) prior to extraction for solution ³¹P-NMR spectroscopy. Freezing, refrigerating and drying samples for periods of up to 6 months prior to extraction with 0.25 M NaOH + 0.05 M Na₂EDTA increased the concentration of extracted P by an average of 16% relative to samples extracted without storage. Pre-extraction storage also introduced some minor changes in P speciation, by increasing the percentage of orthophosphate by up to 15% and decreasing the percentage of pyrophosphate by up to 5%, relative to the abundances of these P species in samples extracted without storage. Drying caused the biggest changes in speciation, specifically decreasing more extensively the relative percentage of pyrophosphate compared to other treatments. Nevertheless, observed changes in speciation due to sample storage within a specific sample were small relative to differences observed among samples collected sequentially in the same area, or reported differences among samples collected at different locations. Samples were also analyzed by solid-state ³¹P-NMR spectroscopy before and after extraction, to examine extraction-related changes in P speciation. Comparison of solution with solid-state ³¹P NMR indicates that extraction with NaOH–EDTA removes the majority of organic esters, but only a variable portion of phosphonates (39–67%). In addition, there was preferential extraction of Ca-associated phosphate over Mg-, Fe- and Al-associated phosphate. Solution ³¹P NMR enables much higher resolution of P species within samples, particularly when it is important to speciate orthophosphate monoesters and diesters, or if polyphosphates are present. However, combining solid-state ³¹P NMR with solution ³¹P NMR spectroscopy for marine particles should be conducted when examining inorganic P speciation and the abundance of phosphonates.  相似文献   

Life-history strategies of calanoid congeners under two different climate regimes: a comparison   总被引：5，自引：0，他引：5  

Halsband-Lenk  Claudia; Carlotti  Francois; Greve  Wulf 《ICES Journal of Marine Science》2004,61(4):709-720

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Reproductive success of Calanus pacificus during diatom blooms in Dabob Bay, Washington   总被引：1，自引：4，他引：1  

James J. Pierson  Claudia Halsband-Lenk  Andrew W. Leising 《Progress in Oceanography》2005,67(3-4):314

While numerous laboratory studies in the last decade have shown that diatoms can induce reproductive failure in copepods, field evidence for a negative diatom effect is equivocal. To unambiguously elucidate the effects diatoms have on copepod reproduction in situ, we undertook a study of the abundance, distribution, grazing rates, and reproductive success of Calanus pacificus in Dabob Bay, Washington, USA, during two spring bloom periods. We simultaneously measured the phytoplankton composition, abundance, and distribution. Here we present results for the reproductive success of C. pacificus using four measurements: egg production rate, clutch size, egg hatching success, and naupliar survival (to the first feeding stage). Egg production rate was positively correlated with chlorophyll a concentration, and egg hatching success and naupliar survival were usually greater than 80%. However, in February 2002 and 2003 – during blooms of diatoms of the genus Thalassiosira – either egg hatching success, naupliar survival, or both were significantly depressed compared to other times in spring and summer. These effects, combined with evidence that C. pacificus was grazing aldehyde-producing Thalassiosira at the time of their blooms, indicate that diatoms can negatively affect copepod reproduction in the field, albeit only under specific circumstances and for brief periods.  相似文献   

Paleontology,sedimentology and paleoenvironment of a new fossiliferous locality of the Jurassic Cañadón Asfalto Formation,Chubut Province,Argentina     

Oscar F. Gallego  Nora G. Cabaleri  Claudia Armella  Wolfgang Volkheimer  Sara C. Ballent  Sergio Martínez  Mateo D. Monferran  Diego G. Silva Nieto  Manuel A. Páez 《Journal of South American Earth Sciences》2011,31(1):54-68

A new Late Jurassic assemblage of “conchostracans”, ostracods, bivalves and caddisfly cases from the locality “Estancia La Sin Rumbo”, Chubut Province (Patagonia, Argentina) is recorded. The fossils occur in the upper part of an outcropping 45 m thick volcaniclastic lacustrine sequence of yellowish tuffs and tuffites of the Puesto Almada Member, which is the upper member of the Cañadón Asfalto Formation with U/Pb age of 161 ± 3 Ma. The sequence represents one sedimentary cycle composed of a (lower) hemicycle of expansion and a (higher) hemicycle of contraction of the water body. The invertebrates lived in small freshwater bodies during the periods of expansion of the lake. The occurrence of a great number of small spinicaudatans, associated with mud-cracks, is evidence of dry climatic conditions and suggests several local mortality events. The spinicaudatan record of the fushunograptid–orthestheriid (component of the Eosestheriopsis dianzhongensis fauna) and the presence of Congestheriella rauhuti Gallego and Shen, suggest a Late Jurassic (Oxfordian to Tithonian) age. Caddisfly cases are recorded for the first time in the Cañadón Asfalto Basin.  相似文献   

Export stoichiometry and migrant-mediated flux of phosphorus in the North Pacific Subtropical Gyre     

Cecelia C.S. Hannides  Michael R. Landry  Claudia R. Benitez-Nelson  Renée M. Styles  Joseph P. Montoya  David M. Karl 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):73-88

Export processes play a major role in regulating global marine primary production by reducing the efficiency of nutrient cycling and turnover in surface waters. Most studies of euphotic zone export focus on passive fluxes, that is, sinking particles. However, active transport, the vertical transfer of material by migrating zooplankton, can also be an important component of carbon (C) and nitrogen (N) removal from the surface ocean. Here we demonstrate that active transport is an especially important mechanism for phosphorus (P) removal from the euphotic zone at Station ALOHA (Hawaii Ocean Time-series program; 22°45′N, 158°W), a P-stressed site in the North Pacific Subtropical Gyre. Migrant excretions in this region are P-rich (C₅₁:N₁₂:P₁) relative to sinking particles (C₂₅₀:N₃₁:P₁), and migrant-mediated P fluxes are almost equal in magnitude (82%) to P fluxes from sediment traps. Migrant zooplankton biomass and therefore the importance of this P removal pathway relative to sinking fluxes has increased significantly over the past 12 years, suggesting that active transport may be a major driving force for enhanced P-limitation of biological production in the NPSG. We further assess the C:N:P composition of zooplankton size fractions at Station ALOHA (C₈₈:N₁₈:P₁, on average) and discuss migrant-mediated P export in light of the balance between zooplankton and suspended particle stoichiometries. We conclude that, because active transport is such a large component of the total P flux and significantly impacts ecosystem stoichiometry, export processes involving migrant zooplankton must be included in large-scale efforts to understand biogeochemical cycles.  相似文献   

Deconstructing the concept of shared responsibility for disaster resilience: a Sunshine Coast case study,Australia     

Lila Singh-Peterson  Paul Salmon  Claudia Baldwin  Natassia Goode 《Natural Hazards》2015,79(2):755-774

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Microvertebrates from the Rhaetian basal bone bed of Saltford,near Bath,SW England     

Matthieu Moreau  Christopher J. Duffin  Claudia Hildebrandt  Deborah Hutchinson  Adam Parker  Simon Carpenter  Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(2):174-187

The famous Rhaetian bone bed (Late Triassic, 205 Ma) is well known because it marks a major switch in depositional environment from terrestrial red beds to fully marine conditions throughout the UK and much of Europe. The bone bed is generally cemented and less than 10 cm thick. However, we report here an unusual case from Saltford, near Bath, S.W. England where the bone bed is unconsolidated and up to nearly 1 m thick. The exposure of the basal beds of the Westbury Formation, Penarth Group includes a bone bed containing a diverse Rhaetian marine microvertebrate fauna dominated by sharks, actinopterygian fishes and reptiles. Despite the unusual sedimentary character of the bone bed, we find similar proportions of taxa as in other basal Rhaetian bone beds (55–59 % Lissodus teeth, 13–16 % Rhomphaiodon teeth, 12–14 % Severnichthys teeth, 6–9% Gyrolepis teeth, 3–4% undetermined sharks’ teeth, 1–3% undetermined bony fish teeth, and < 1% of each of Hybodus, Parascylloides, and Sargodon), the only differences being in the proportions of Rhomphaiodon teeth, which can represent 30–40 % of specimens elsewhere. This suggests that taphonomic bias of varying Rhaetian bone beds may be comparable despite different sedimentary settings, and that the proportions of taxa say something about their original proportions in the ecosystem.  相似文献   

Development of mirrors made of chemically tempered glass foils for future X-ray telescopes     

Bianca Salmaso  Marta Civitani  Claudia Brizzolari  Stefano Basso  Mauro Ghigo  Giovanni Pareschi  Daniele Spiga  Laura Proserpio  Yves Suppiger 《Experimental Astronomy》2015,39(3):527-545

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The first detection of propane on Saturn     

Thomas K. Greathouse  John H. Lacy  Bruno Bézard  Matthew J. Richter  Claudia Knez 《Icarus》2006,181(1):266-271

We report the first detection of propane, C₃H₈, in Saturn's stratosphere. Observations taken on September 8, 2002 UT at NASA's IRTF using TEXES, show multiple emission lines due to the 748 cm⁻¹ν₂₁ band of C₃H₈. Using a line-by-line radiative transfer code, we are able to fit the data by scaling the propane vertical mixing ratio profile from the photochemical model of Moses et al. [2000. Icarus 143, 244-298]. Multiplicative factors of 0.7 and 0.65 are required to fit the −20° and −80° planetocentric latitude spectra. The resultant profiles are characterized by a 5 mbar mixing ratio of 2.7±0.8×¹⁰⁻⁸ at −20° and at −80° latitude. These results suggest that the time scale for meridional circulation lies between the net photochemical lifetimes of C₂H₂ and C₃H₈, ≈30-600 years.  相似文献   

东洞庭湿地植被格局变化及其影响因素   总被引：4，自引：0，他引：4  

雷璇  杨波  蒋卫国  杨一鹏  Claudia Kuenzer  陈强 《地理研究》2012,31(3):461-470

东洞庭湖(也称东洞庭)湿地植被格局的变化特征及其影响因素的分析是该地区湿地植被保护与恢复策略制定的基础。基于美国陆地资源卫星Landsat TM/ETM+数据,应用决策树分类法分别提取东洞庭湖1999年、2002年、2006年三个时期湿地景观信息,通过转移矩阵法和质心迁移法对植被的时空演变分析。结果表明:(1)1993～2002年东洞庭湖芦苇、林地、苔草滩地面积均有所增加,芦苇增长速度最快,年均增长面积为28.93km²;2002～2006年林地面积迅速增加,年均增长面积为29.655km²,苔草面积有所减少,芦苇面积保持基本稳定;(2)东洞庭湖湿地植被质心呈现从林地—芦苇—苔草逐层靠近湖心的分布特点,1993～2006年三种植被类型的质心均不断向湖心迁移,其中以林地与芦苇的变迁更为显著。  相似文献