1,721,063 research outputs found
Factors controlling the summer Emiliania huxleyi bloom in the Black Sea: a modeling study
No full textA one-dimensional coupled physical–ecosystem model identifies factors causing blooms of the coccolithophore Emilania huxleyi in the Black Sea, regularly observed during the early summer periods. The model specifically applies for a more idealized ecosystem of the interior basin, away from the coastal zone. It is represented in the form of four groups of phytoplankton (diatoms, dinoflagellates, E. huxleyi, a small phytoplankton group), and two groups of zooplankton further accompanied by simplified nitrogen and phosphorus cycles. The simulations show that the internal trophodynamic conditions in the Black Sea support E. huxleyi bloom development during May–July period as a part of the seasonal phytoplankton succession. They start flourishing after the diatom and dinoflagellate blooms under nitrogen depleted and moderate light conditions. They make use of regenerated nutrients available in the surface mixed layer and grow concomitantly with picophytoplankton community in the subsurface levels. <br/
Is there any relationship between phytoplankton seasonal dynamics and the carbonate system?
No full textProduction of calcium carbonate by marine calcifying organisms has been shown to decrease under increasing CO2. This effect appears to be driven by a decrease in [CO32?]. The modelling study here described aims at investigating whether the success of a marine calcifying phytoplankton species, the coccolithophore Emiliania huxleyi, may be tied to [CO32?]. The work highlights the complex interactions between the carbonate system variables and spring blooms, and the possibility of a link to the competition between calcifying vs. non-calcifying species on the Bering Sea shelf. We find that the strong seasonal cycle in [CO32?] is driven primarily by carbon drawdown during spring blooms. The interesting outcome of this work is the fact that E. huxleyi bloom timings always coincide with periods of high [CO32?], which is consistent with studies showing coccoliths malformations and a slowdown in calcification at low [CO32?]. Whether the condition of high [CO32?] can be considered a crucial ecological factor for the success of E. huxleyi, however, remains an open and important question needing further investigation
ANALYTICAL PROFILE ESTIMATION IN DATABASE-SYSTEMS
No full textMost parameters which constitute the statistical profile are related to the record selectivity. To estimate record selectivity factors, the nonparametric are better than parametric methods in that they make no a priori assumptions concerning the data distribution and generally provide accurate results. Nonparametric methods are classified into the usual scale-based methods, which function by the scaling of attribute ranges, and analytic methods discussed in this paper, which are scale independent. Our analytic method is based on the computation of a set of parameters, the so-called Canonical Coefficients, which enable the multivariate distribution of the data to be well known. Based on the canonical coefficients, the main parameters of database statistical profiles can be easily defined and efficiently calculated (in terms of computation time and estimation accuracy). In addition, some important applications, which are of peculiar interest to statistical database systems can be developed. Experimental results on real databases are presented which demonstrate the versatility and reliability of the analytic approach
Analysis of satellite imagery for Emiliania huxleyi blooms in the Bering Sea before 1997
No full textThe presence of blooms of the coccolithophore Emiliania huxleyi in the Bering Sea shelf has been studied using satellite imagery in order to ascertain whether its first reported appearance in 1997 is really a new phenomenon for the area. Examination for Emiliania huxleyi blooms in Coastal Zone Color Scanner (CZCS) and Advanced Very High Resolution Radiometer (AVHRR) imagery dating from 1978 to 1996 was performed and the relationship between the presence of Emiliania huxleyi and the Pacific Decadal Oscillation and the El Niño Southern Oscillation was investigated. No evidence of the presence of this species was found in CZCS or AVHRR imagery between 1978 and 1995. AVHRR images reveal that a small coccolithophore bloom was present in summer 1996. Although the blooms of 1997 were unprecedented in extension and intensity, it appears that the Bering Sea ecosystem did not respond as abruptly to atmospheric anomalies as initially reported
Effects of ketamine-enantiomers anesthesia on local cerebral glucose utilization in the rat
No full textAnesthesiology 91:772A, 199
Effects of serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine, paroxetine, and sertraline on regional cerebral glucose metabolism (rCMRglc) in rats: a (14C)-deoxyglucose study
No full textSociety for Neuroscience Abstracts 25, Part 2:2048, 1999
Effects of acute and chronic treatment with fluoxetine on regional glucose cerebral metabolism in rats: implications for clinical therapeutics.
No full textBRAIN RES
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