Interaction Between Macrophytobenthic Groups on the Sublittoral Belt of a Greek Island     

Aristidis  Diappoulis  Alexis  Conides Theodore  Koussouris 《Marine Ecology》1994,15(1):41-50

Abstract. The interrelationships between the main phytobenthic groups of Chlorophyceae, Phaeophyceae, and Rhodophyceae around Milos Island, Central Aegean Sea, were studied using standard ecological and mathematical methods. The analysis was based on seasonal sampling of 114 different macrophytobenthic species.
The employed ecological indices revealed that the sampling areas located on the north, south, and east side of Milos Island show similar annual fluctuations in abundance and species diversity. The resemblance was particularly high between all stations in October-February, between south and east stations during May, and between north and east stations during July.
Additionally, an annual cycle of group interaction with regard to species diversity and abundance exists between the Chlorophyceae, Rhodophyceae, and Phaeophyceae. The Rhodophyceae are the most abundant and dominant group throughout the year, showing percentages in the samples higher than 70% in all sampling areas.  相似文献   

Accumulation of plastic litter on beaches of Amchitka Island,Alaska     

Theodore R. Merrell 《Marine environmental research》1980,3(3):171-184

Between 1972 and 1974 plastic marine litter on ten 1-km beaches at Amchitka Island increased from 2,221 to 5,367 items—a 2·4 x increase in a two-year period. Most litter originated from Japanese and Soviet fishing vessels, but some items were from the Asian coast, at least 1,150 km distant. In 1974 there were 345 kg of common items of plastic litter per kilometre of beach. In 1972, an estimated 1,664 metric tons of plastic litter was lost or dumped from fishing vessels in the Bering Sea and North Pacific Ocean. Stranded plastic litter persists indefinitely but rapidly becomes buried in beach material or is blown inland and covered with vegetation. The most serious environmental impact is probably entanglement of marine mammals and birds in some types of litter. The accelerating accumulation of litter could be reduced through unilateral action by countries that regulate coastal fishing privileges if these countries make litter control a condition for permission to fish.  相似文献   

Future research problems in marine organic chemistry     

Robert B. Gagosian  Saiyed I. Ahmed  John W. Farrington  Richard F. Lee  Richard F. C. Mantoura  Kenneth H. Nealson  Theodore T. Packard  Kenneth L. Reinhart  Jr. 《Marine Chemistry》1978,6(4):375-382

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The electron density in the direction of ζ Oph     

Theodore P. Stecher  David A. Williams 《Astrophysics and Space Science》1975,32(1):211-213

It is shown that photoionization of vibrationally excited H₂ and photodissociation of the H ₂ ⁺ ions produced thereby constitute a significant electron production route in high UV flux situations. A significant fraction of the electron density in the direction of ζ Oph (?15 km s^?1 cloud) deduced from observations may be expected to arise in this way.  相似文献   

Transformation from proper time on Earth to coordinate time in solar system barycentric space-time frame of reference     

Theodore D. Moyer 《Celestial Mechanics and Dynamical Astronomy》1981,23(1):33-56

In order to obtain accurate computed values of Earth-based range and Doppler observables of a beep space probe, an expression is required for the time differencet–, wheret is coordinate time in the solar system barycentric space-time frame of reference and is proper time recorded on a fixed atomic clock on earth. This paper is part 1 of a two-part article which obtains an expression fort– which is suitable for use in obtaining computed values of observations of a spacecraft or celestial body located anywhere in the solar system. The expression can also be used in the computation of Very Long Baseline Interferometry data types. Part 1 obtains an expression fort– which is a function of position and velocity vectors of the major celestial bodies of the solar system and the atomic clock on Earth which reads . In Part 2, this expression will be transformed to a function of time and the Earth-fixed coordinates of the atomic clock.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under NASA Contract No. NAS 7-100.  相似文献   

Near-infrared spectra of the Galilean satellites: Observations and compositional implications     

James B. Pollack  Fred C. Witteborn  Edwin F. Erickson  Donald W. Strecker  Betty J. Baldwin  Theodore E. Bunch 《Icarus》1978,36(3):271-303

We have obtained reflectivity spectra of the trailing and leading sides of all four Galilean satellites with circular variable filter wheel spectrometers operating in the 0.7- to 5.5-μm spectral interval. These observations were obtained at an altitude of 41,000 ft from the Kuiper Airborne Observatory. Features seen in these data include a 2.9-μm band present in the spectra of both sides of Callisto; the well-known 1.5-μm and 2.0-μm combination bands and the previously more poorly defined 3.1-μm fundamental of water ice observed in the spectra of both sides of Europa and Ganymede; and features centered at 1.35 ± 0.1, 2.55 ± 0.1, and 4.05 ± 0.05 μm noted in the spectra of both sides of Io. In an effort to interpret these data, we have compared them with laboratory spectra as well as synthetic spectra constructed with a simple multiple-scattering theory. We attribute the 2.9-μm feature of Callisto's spectra primarily to bound water, with the product of fractional abundance of bound water and mean grain radius in micrometers equaling approximately 3.5 × 10^?1 for both sides of the satellite. The fractional amounts of water ice cover on the trailing side of Ganymede, its leading side, and the leading side of Europa were found to be 50 ± 15, 65 ± 15, and 85% or greater, respectively. The bare ground areas on Ganymede have reflectivity properties in the 0.7- to 2.5-μm spectral region comparable to those of Callisto's surface and also have significant quantities of bound water, as does Callisto. Interpretation of the spectrum for the trailing side of Europa is complicated by magnetospheric particle bombardment which causes a perceptible broadening of strong bands, but the ice cover on this side is probably comparable to that on the leading side. These irradiation effects may be responsible for much of the difference in the visual geometric albedos of the two sides of Europa. Minor, but significant, amounts of ferrous-bearing material (either ferrous salts or alkali feldspars but not olivines or pyroxenes) account for the 1.35-μm feature of Io. The two longer wavelength bands are most likely attributable to nitrate salts. Ferrous salts and nitrates can jointly also account for much of the spectral variation in Io's visible reflectivity, thereby eliminating the need to postulate large quantities of sulfur. The absence of noticeable features near 3-μm wavelength in Io's spectra leads to upper bounds of 10% on the fractional cover of water and ammonia ice and 10^?3 on the relative abundance of bound water and hydroxylated material on Io. The two sides of Io have similar compositions. We suggest that the systematic increase in fractional water ice cover from Callisto to Ganymede to Europa is bought about by variations in efficiencies of recoating the satellite's surface by interior water brought to the surface, and by the deposition of extrinsic dust. The most important component of the latter is debris, derived from the outer irregular satellites of Jupiter, which impacts the Galilean satellites at relatively low velocities. Europa has the largest water ice cover because its crust is thinnest and thus the frequency of water recoating is the greatest, and because it is farthest from the sources of low-velocity dust. While models which depict Io's surface as consisting primarily of very fine-grained ice are no longer viable, we are unable to definitively distinguish between the salt assemblage and alkali feldspar models. The salt model can better account for Io's reflectivity spectrum from 0.3 to 5 μm, but the absence of appreciable quantities of bound water and hydroxylated material may not be readily understood within the context of that model.  相似文献   

Laboratory Comparison of Polyethylene and Dialysis Membrane Diffusion Samplers   总被引：1，自引：1，他引：1  

Theodore A. Ehlke  Thomas E. Imbrigiotta  Jeffrey M. Dale 《Ground Water Monitoring & Remediation》2004,24(1):53-59

The ability of diffusion samplers constructed from regenerated cellulose dialysis membrane and low density, lay flat polyethylene tubing to collect volatile organic compounds and inorganic ions was compared in a laboratory study. Concentrations of vinyl chloride, cis -1, 2-dichloroethene, bromochloromethane, trichloroethene, bromodichloromethane, and tetrachloroethene collected by both types of diffusion samplers reached equilibrium with the concentrations of these compounds in test solution within three days. Concentrations of bromide and iron collected by the dialysis membrane diffusion samplers reached equilibrium with the concentrations of these compounds in a test solution within three to seven days. No detectable concentrations of bromide or iron were found in polyethylene diffusion samplers even after 21 days. No measurable concentrations of aluminum, arsenic, barium, cadmium, chromium, iron, mercury, manganese, nickel, and lead, or sulfide, were leached out of dialysis membrane samplers over seven days. Compared with using a gas-tight syringe to sample the diffusion sampler, clipping the bag and pouring the water sample into a sample vial resulted in only a small 6.2% average loss of volatile organic compounds. Dialysis membrane diffusion samplers offer promise for use in sampling ground water for inorganic constituents as well as volatile organic compounds.  相似文献   

Pore pressure during metamorphism of carbonate rock: effect of volumetric properties of H<Subscript>2</Subscript>O–CO<Subscript>2</Subscript> mixtures     

Theodore C. Labotka  Lawrence M. Anovitz  James G. Blencoe 《Contributions to Mineralogy and Petrology》2002,144(3):305-313

The molar volume of mixtures of CO₂ and H₂O is a strong function of the fluid composition. Both CO₂ and H₂O participate in the metamorphism of carbonate rocks, resulting in a change in the fluid composition during reaction. One of the effects of the change in composition is the increase in pore-fluid pressure with only small increases in extent of reaction, ;. Pressure calculated from the volumetric properties of CO₂-H₂O mixtures at 400 °C increases greatly with small increases of ; but drops at greater values because of the increase in pore volume as a result of (V_solid. The pore pressure increase at small values of ;, though, readily exceeds the reported tensile strength of carbonate rocks, and the rock cannot sustain significant reaction without fracturing. The result of a small amount of reaction is a fractured rock with increased permeability, which promotes fluid transport.  相似文献   

Sediments as sources of DDT and PCB     

David R. Young  Deirdre McDermott-Ehrlich  Theodore C. Heesen 《Marine pollution bulletin》1977,8(11):254-257

Despite major decreases in DDT and PCB emissions over a three year period by the dominant discharger to a coastal marine site, only minor (and very similar) decreases were observed in concentrations of these pollutants in bottom sediments and flatfish from the outfall monitoring zone. These results illustrate how persistant such chlorinated hydrocarbons can be in the marine environment once the bottom sediments have been contaminated.  相似文献   

A deterministic approach to the prediction of free field ground motion and response spectra from stick-slip earthquakes     

J. Theodore Cherry  Eldon J. Halda  Kenneth G. Hamilton 《地震工程与结构动力学》1976,4(4):315-332

Theoretical and experimental results from computational physics and non-linear rock mechanics have been merged in order to obtain a deterministic model of a stick-slip earthquake. The model has been exercised to uncover the dependence of peak ground motion and response spectra on fault length, rupture velocity and dynamic stress drop during rupture. A particular method for generating a design spectrum has been tested against results from the model. Utilization of this deterministic technique seems especially appropriate when design information is required at sites located near the epicentre.  相似文献