Physiological responses of a bloom-forming green macroalga to short-term change in salinity,nutrients, and light help explain its ecological success   总被引：1，自引：0，他引：1  

Risa?A.?CohenEmail author  Peggy?Fong 《Estuaries and Coasts》2004,27(2):209-216

Enteromorpha intestinalis is a bloom-forming species of macroalgae associated with eutrophication. The objective of this study was to investigate how this alga performs osmoregulation and nutrient uptake in order to proliferate under environmental conditions that covary with eutrophication. We quantified the response ofE. intestinalis to salinity, light, and nutrients. We performed two short-term (48 h) laboratory experiments (salinity alone and salinity × nutrients × light) to examine the algal responses of tissue water, potassium (K⁺), and nutrient (NO ₃ ⁻ and total N) content. Tissue water content decreased with increasing salinity, and although K⁺ concentration decreased from the initial concentration, it decreased less with increased salinity treatment demonstrating two mechanisms to withstand short-term salinity fluctuation. The salinity × nutrient × light experiment showed that, in the short term, light had an interaction with tissue K⁺. Total tissue N content was positively related to N treatment level, and light did not affect total nutrient concentration. The effect of light was present whether the nutrients were present in the tissue as inorganic or organic forms. With reduced light, we hypothe size that the assimilation of inorganic to organic N was energy limited. The ability of this alga to take up available nutrients rapidly for growth and short-term osmoregulation, even under low light and salinity levels, helps to explain the bloom potential ofE. intestinalis.  相似文献   

On the Behavior of the Stable Boundary Layer and the Role of Initial Conditions     

Xingzhong Shi  Richard T. McNider  M. P. Singh  David E. England  Mark J. Friedman  William M. Lapenta  William B. Norris 《Pure and Applied Geophysics》2005,162(10):1811-1829

Previous studies of the stable atmospheric boundary layer using techniques of nonlinear dynamical systems (MCNIDER et al., 1995) have shown that the equations support multiple solutions in certain parameter spaces. When geostrophic speed is used as a bifurcation parameter, two stable equilibria are found—a warm solution corresponding to the high-wind regime where the surface layer of the atmosphere stays coupled to the outer layer, and a cold solution corresponding to the low-wind, decoupled case. Between the stable equilibria is an unstable region where multiple solutions exist. The bifurcation diagram is a classic S shape with the foldback region showing the multiple solutions. These studies were carried out using a simple two-layer model of the atmosphere with a fairly complete surface energy budget. This allowed the dynamical analysis to be carried out on a coupled set of four ordinary differential equations. The present paper extends this work by examining additional bifurcation parameters and, more importantly, analyzing a set of partial differential equations with full vertical dependence. Simple mathematical representations of classical problems in dynamical analysis often exhibit interesting behavior, such as multiple solutions, that is not retained in the behavior of more complete representations. In the present case the S-shaped bifurcation diagram remains with only slight variations from the two-layer model. For the parameter space in the foldback region, the evolution of the boundary layer may be dramatically affected by the initial conditions at sunset. An eigenvalue analysis carried out to determine whether the system might support pure limit-cycle behavior showed that purely complex eigenvalues are not found. Thus, any cyclic behavior is likely to be transient.  相似文献   

Editorial     

Mel Friedman 《Tectonophysics》1984,101(3-4)

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Solar soft X-ray flare spectra from OSO-4     

J. F. Meekins  G. A. Doschek  H. Friedman  T. A. Chubb  R. W. Kreplin 《Solar physics》1970,13(1):198-212

Solar flare spectral data, covering the wavelength range 0.7–8.5 Å, are derived from the NRL Bragg crystal spectrometers aboard OSO-4. A detailed analysis of the soft X-ray spectra for the 3b flare of 16 November 1967 (2140 UT) is presented, and it is found that electron temperatures derived from continua and emission lines are compatible with a two or more component plasma, differing in temperature by 6–10 × 10⁶K.  相似文献   

Collisional excitation of metastable oxygen O(D) atoms through the B∑_u channel of O₂     

M. J. Jamieson  M. Finch  R. S. Friedman  A. Dalgarno 《Planetary and Space Science》1992,40(12):1719-1721

Pectroscopic data on the shifts and widths of the energy levels of molecular oxygen have been used in the empirical construction of a diabatic potential matrix that characterizes the interactions of the B³∑⁻_u state with the ⁵Π_u, 2³∑⁺_u, ³Π_u and ¹Π_u states. The diabatic potential matrix is u theory formulation to calculate the cross-sections for the excitation of O(¹D) atoms in collisions of two O(³P) atoms. Total cross-sections are obtained by adding the excitation from the ³Π_g, channel. The rate coefficient for quenching of O(¹D) by O(³P) is evaluated as a function of temperature. The values conflict with a recent analysis of the emission of the oxygen red line in the upper atmosphere.  相似文献   

Comment on the ‘loss due to imperfect fringe rotation in VLBI correlators’ revisited     

P. A. Friedman 《Astrophysics and Space Science》1987,137(1):189-189

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Galaxy halo occupation at high redshift     

James S. Bullock  Risa H. Wechsler  Rachel S. Somerville 《Monthly notices of the Royal Astronomical Society》2002,329(1):246-256

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The Cosmic Origins Spectrograph: on-orbit instrument performance     

S. Osterman  J. Green  C. Froning  S. B��land  E. Burgh  K. France  S. Penton  T. Delker  D. Ebbets  D. Sahnow  J. Bacinski  R. Kimble  J. Andrews  E. Wilkinson  J. McPhate  O. Siegmund  T. Ake  A. Aloisi  C. Biagetti  R. Diaz  W. Dixon  S. Friedman  P. Ghavamian  P. Goudfrooij  G. Hartig  C. Keyes  D. Lennon  D. Massa  S. Niemi  C. Oliveira  R. Osten  C. Proffitt  T. Smith  D. Soderblom 《Astrophysics and Space Science》2011,335(1):257-265

The Cosmic Origins Spectrograph (COS) was installed in the Hubble Space Telescope in May, 2009 as part of Servicing Mission 4 to provide high sensitivity, medium and low resolution spectroscopy at far- and near-ultraviolet wavelengths (FUV, NUV). COS is the most sensitive FUV/NUV spectrograph flown to date, spanning the wavelength range from 900 Å to 3200 Å with peak effective area approaching 3000 cm². This paper describes instrument design, the results of the Servicing Mission Orbital Verification (SMOV), and the ongoing performance monitoring program.  相似文献   

Spatial modelling of road network development,population pressure and biophysical properties of upland crop and forest conversions in Lop Buri province,Thailand, 1989–2006     

Risa Patarasuk  Timothy J. Fik 《Singapore journal of tropical geography》2013,34(1):120-136

Over the past few decades, land use and land cover change has become a global concern. In the Lop Buri province of Thailand, rapid land cover change, specifically conversion of forests to agriculture, has occurred. The purpose of the study is to identify the predictors of land cover change in Lop Buri province for land that has been converted to upland crops or has undergone deforestation between 1989 and 2006. Four logistic regression models were constructed using spatially explicit biophysical and geo‐social data, to account for changes to upland crops and forest loss from1989–98 and 1998–2006. Across the four models, slope, distance to forest edge, distance to towns, distance to roads, population size, and population density in various stand‐alone and interactive forms were found to be the most consistent predictors of land cover change.  相似文献   

SOCIAL SPACE AND SOCIAL PLACE*     

Douglas Caruso  Risa Palm 《The Professional geographer》1973,25(3):221-225

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