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81.
Philip W. Stevens Marin F. D. Greenwood Charles F. Idelberger David A. Blewett 《Estuaries and Coasts》2010,33(5):1216-1224
Research strategies for investigating the freshwater-inflow requirements of estuarine fishes often integrate life-history
information and correlative analyses of inflow and fish abundance. In tidal rivers, however, some fish have affinities for
embayments, oxbows, and smaller tributaries, often referred to collectively as river “backwaters”. The objective of this study
was to determine whether freshwater and estuarine fish assemblages differed between backwaters and the mainstem of the tidal
Caloosahatchee River, a highly managed river system located in an urban setting in southwest Florida. Nonmetric multidimensional
scaling of 21.3-m seine data revealed that fish assemblages did indeed differ between the backwater and mainstem habitats
in each of three river sections. Univariate analyses identified species that differed in abundance between the habitats, which
included ecologically and economically important fishes in the region. For example, striped mullet Mugil cephalus and pinfish Lagodon rhomboides were more abundant along the river's mainstem; common snook Centropomus undecimalis and bluegill Lepomis macrochirus were more abundant in the river's backwaters. For those species that were more abundant along the mainstem of the river or
showed no difference, studies that measure changes in the distribution and abundance of these species with varying inflow
along the mainstem of the river are justified. However, for species that were more abundant in backwater areas, geomorphological
features should be considered in the design of studies that assess factors affecting fish use. 相似文献
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J.?MajzlanEmail author R.?Stevens J.?Boerio-Goates B. F.?Woodfield A.?Navrotsky P. C.?Burns M. K.?Crawford T. G.?Amos 《Physics and Chemistry of Minerals》2004,31(8):518-531
Crystals of hydronium jarosite were synthesized by hydrothermal treatment of Fe(III)–SO4 solutions. Single-crystal XRD refinement with R1=0.0232 for the unique observed reflections (|Fo| > 4F) and wR2=0.0451 for all data gave a=7.3559(8) Å, c=17.019(3) Å, Vo=160.11(4) cm3, and fractional positions for all atoms except the H in the H3O groups. The chemical composition of this sample is described by the formula (H3O)0.91Fe2.91(SO4)2[(OH)5.64(H2O)0.18]. The enthalpy of formation (Hof) is –3694.5 ± 4.6 kJ mol–1, calculated from acid (5.0 N HCl) solution calorimetry data for hydronium jarosite, -FeOOH, MgO, H2O, and -MgSO4. The entropy at standard temperature and pressure (So) is 438.9±0.7 J mol–1 K–1, calculated from adiabatic and semi-adiabatic calorimetry data. The heat capacity (Cp) data between 273 and 400 K were fitted to a Maier-Kelley polynomial Cp(T in K)=280.6 + 0.6149T–3199700T–2. The Gibbs free energy of formation is –3162.2 ± 4.6 kJ mol–1. Speciation and activity calculations for Fe(III)–SO4 solutions show that these new thermodynamic data reproduce the results of solubility experiments with hydronium jarosite. A spin-glass freezing transition was manifested as a broad anomaly in the Cp data, and as a broad maximum in the zero-field-cooled magnetic susceptibility data at 16.5 K. Another anomaly in Cp, below 0.7 K, has been tentatively attributed to spin cluster tunneling. A set of thermodynamic values for an ideal composition end member (H3O)Fe3(SO4)2(OH)6 was estimated: Gof= –3226.4 ± 4.6 kJ mol–1, Hof=–3770.2 ± 4.6 kJ mol–1, So=448.2 ± 0.7 J mol–1 K–1, Cp (T in K)=287.2 + 0.6281T–3286000T–2 (between 273 and 400 K). 相似文献
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Relationships between mineral/silicate melt partition coefficients and melt structure have been examined by combining Ca and Mn olivine/melt partitioning data with available melt structure information. Compositions were chosen so that melts with olivine on their liquidii range in degree of polymerization, NBO/T, from ∼0.5 to ∼2.5 under near isothermal conditions (1350-1400°C). Olivine/melt Ca-Mn exchange coefficients, Ca(olivine)/CaO(melt)/MnO(olivine)/MnO(melt) (KD Ca-Mnolivine/melt), as a function of melt NBO/T have a parabolic shape with a minimum KD Ca-Mnolivine/melt-value at NBO/T near 1. Notably, published KD Fe2+-Mgolivine/melt versus NBO/T functions are also parabolic with a maximum in KD Fe2+-Mgolivine/melt near 1 (Kushiro and Mysen, 2002).The olivine/melt partitioning data are modeled in terms of structural units (Qn-species) in the melt. The NBO/T-value corresponding to the minimum KD Ca-Mnolivine/melt is near that where the abundance ratio of Qn-species, XQ3/XQ2, has its largest value. Therefore, the activity coefficient ratio in the melt, γCa2+(melt)/γMn2+(melt), attains a minimum where the abundance ratio of XQ3/XQ2 is at maximum. It is inferred from this relationship that Ca2+ in the melts is dominantly bonded to nonbridging oxygen (Ca-NBO) in Q3-species, whereas Mn2+ is bonded to nonbridging oxygen (Mn-NBO) in less polymerized Qn-species such as Q2. 相似文献
87.
Partitioning of Ca, Mn, Mg, and Fe2+ between olivine and melt has been used to examine the influence of energetically nonequivalent nonbridging oxygen in silicate melts. Partitioning experiments were conducted at ambient pressure in air and 1400°C with melts in equilibrium with forsterite-rich olivine (Fo >95 mol%). The main compositional variables of the melts were NBO/T and Na/(Na+Ca). In all melts, the main structural units were of Q4, Q3, and Q2 type with nonbridging oxygen, therefore, in the Q3 and Q2 units.For melts with high Q3/Q2-abundance ratio (corresponding to NBO/T near 1), increasing Na/(Na+Ca) [and Na/(Na+Ca+Mn+Mg+Fe2+)] results in a systematic decrease of the partition coefficients, KCaol/melt, KMnol/melt, KMgol/melt, and KFe2+ol/melt, because of ordering of the network-modifying Ca, Mn, Mg, and Fe2+ among nonbridging oxygen in Q3 and Q2 structural units. This decrease is more pronounced the smaller the ionic radius of the cation. With decreasing Q3/Q2 abundance ratio (less-polymerized melts) this effect becomes less pronounced.Activity-composition relations among network-modifying cations in silicate melts are, therefore, governed by availability of energetically nonequivalent nonbridging oxygen in individual Qn-species in the melt. As a result, any composition change that enhances abundance of highly depolymerized Qn-species will cause partition coefficients to decrease. 相似文献
88.
Foy Lake in northwestern Montana provides a record of annual-to-decadal-scale landscape change. Sedimentary charcoal and pollen analyses were used to document fire and vegetation changes over the last 3800 years, which were then compared to similar records from AD 1880 to 2000. The long-term record at Foy Lake suggests shifts between forest and steppe as well as changes in fire regime that are likely the result of climate change. Fire activity (inferred from the frequency of charcoal peaks) averaged 18 fire episodes/1000 years from 3800 to 2125 cal year BP, and increased from 16 fire episodes/1000 years at 2125 cal year BP to 22 episodes/1000 years at 750 cal year BP, a period when the pollen data suggest that steppe vegetation yielded to increasing patches of forest cover. Between 2125 and 750 cal year BP, increased forest cover produced more background charcoal than before and after this period, when vegetation was dominated by steppe. Between 750 and 75 cal year BP steppe has expanded and fire episode frequency averaged 33 episodes/1000 years, increasing to a maximum of 40 episodes/1000 years at ca. 300 cal year BP and then decreasing to present levels. Since AD 1880, the pollen record indicates an increase in shrubs and grasses from AD 1895 to 1960 as a result of vegetation changes associated with timber harvesting and livestock grazing. No fires have been documented in the Foy Lake watershed since AD 1880. Charcoal from the extralocal fires of AD 1910, burning over 4,111,249 ha in Idaho, Montana, and Wyoming, however, is present in Foy Lake. Between AD 1970 and 2000, increased arboreal pollen in the record is consistent with observations that the forest has become more closed. The activities of Euro–Americans have led to a decline in forest cover between AD 1880 and 1970, followed by a recent increase as trees are now growing in areas previously occupied by steppe. Euro–Americans are likely the cause of a reduction in fire activity in watershed since AD 1880. 相似文献
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Craig Stevens Gregory Lawrence Paul Hamblin Eddy Carmack 《Dynamics of Atmospheres and Oceans》1996,24(1-4)
A vertically integrated approach to the analysis of thermistor chain and wind data from a long, narrow, stratified lake indicates that forcing events are short relative to the response time. Correlations between forcing and isotherm tilts clearly indicate stratification response times dependent on internal wave speed. In addition, it is possible to infer basin-scale internal wave damping where over 80% of the potential energy in the internal wave setup is lost in one internal wave period. 相似文献