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Variations in the quantity and composition of seston from an estuary in southern Chile on different temporal scales 总被引：1，自引：0，他引：1
O.R. Chaparro C.J. Segura Y.A. Montiel R.J. Thompson J.M. Navarro 《Estuarine, Coastal and Shelf Science》2008,76(4):845-860
Estuaries are characterised by highly variable environmental conditions largely driven by tidal and atmospheric forces. This study investigates variation in the physical environment and the composition of the seston on various temporal scales in the Quempillén estuary, southern Chile. The water column was sampled throughout the tidal cycle at various times of the year. Total particulate matter, particulate inorganic matter, particulate organic matter, particle numbers, total particle volume, proximate biochemical composition and energy content of the seston, chlorophyll a and chloropigments were routinely measured. In each of the months in which sampling took place, two or three tidal cycles were examined. The information not only helps to explain the dynamics of the estuary, but is essential for an understanding of the physiology and ecology of the suspension-feeders which exploit the seston as a food source, the most dominant being the gastropod Crepipatella dilatata. Temperature and salinity were generally highest during summer, but seston quality, defined by energy content and biochemical composition (lipid, protein and carbohydrate) was higher at the end of winter and during spring. Chlorophyll a values were greatest in late spring (November). Many of the variables studied changed frequently according to the phase of the tidal cycle, and in several cases significant differences were observed among tidal cycles from the same month of the same year. In general the variables measured did not exhibit consistent patterns linked to the tidal cycle, possibly because any such patterns were masked by atmospheric conditions (wind and rain) that dominate the region and greatly influence the estuary. The quantity and quality of the seston available to suspension-feeders is largely determined by these atmospheric forces, which cause an influx of terrigenous material from adjacent areas and also resuspend bottom sediment. These effects are magnified by the shallowness of the estuary (<2 m depth). The food supply for C. dilatata and other suspension-feeders therefore varies on temporal scales varying from hourly (tidal cycle) to daily/weekly (atmospheric forces) to monthly (seasonal influences), but inhibition of feeding by low salinity sometimes limits the ability of C. dilatata to exploit fully the available organic matter. 相似文献
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Rita Pez Gilia Ruiz Rmulo Mrquez Luz Marina Soto Marynes Montiel Carlos Lpez 《Limnologica》2001,31(2)
Limnological features of Tulé Reservoir, a large and shallow reservoir in western Venezuela were studied from May 1992 to December 1993. This reservoir is polymictic, with a low water transparency. Levels of nitrogen were high and phytoplankton productivity was low. The phytoplankton productivity values may be explained by the low concentrations of orthophosphate during the larger part of the sampling period and the frequent mixing and resuspension of sediments. Heterotrophic bacteria were between 1651.67 and 4365.00 Colony-forming Units/ml. Species composition of the crustacean zooplankton community was similar to other neotropical eutrophic reservoirs. 相似文献
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O.R. Chaparro Y.A. Montiel C.J. Segura V.M. Cubillos R.J. Thompson J.M. Navarro 《Estuarine, Coastal and Shelf Science》2008,76(4):861-868
The suspension-feeding gastropod Crepipatella dilatata occurs in estuaries in southern Chile that experience considerable fluctuations in salinity, driven by tidal and atmospheric forces. In the Quempillén estuary salinities as low as 9 psu may occur after severe rainstorms, and persist for several hours. In this study salinity was the major factor influencing the clearance rate of C. dilatata. At salinities below 20 psu, filtration ceased, whereas at high salinities (>22 psu) mean clearance rate was 0.24 l h−1 standard animal−1 (S.D. 0.18) for actively filtering individuals. This was confirmed by laboratory experiments under controlled conditions. Endoscopic observations were consistent with measurements of clearance rate, and showed that at salinity 25–30 psu the rate of transport along the gill filaments of particulate material embedded in mucus was 759 μm s−1 (S.D. 480), but particle transport ceased at and below salinity 20 psu. Complete or partial isolation of the mantle cavity from the environment may be a mechanism to protect soft tissues and/or incubated egg capsules from osmotic stress. 相似文献
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Photosynthetic responses of selected Antarctic plants to solar radiation in the southern maritime Antarctic 总被引：1，自引：0，他引：1
The effects of UV-B exclusion and enhancement of solar radiation on photosynthesis of the two phanerogams which occur in the maritime Antarctic, Deschampsia antarctica and Colobanthus quitensis , and the moss Sanionia uncinats were investigated. Data on air temperature and solar radiation illustrate a drastic seasonal variation. Daily O3 column mean values and UV-B measured at ground level document the occurrence of the O3 "hole" in the spring of 1997, with a concomitant increase in UV-B. The grass, D. antarctica , exhibited a broad temperature optimum for photosynthesis between 10–25°C while photosynthesis did not saturate even at high irradiance. The high water use efficiencies measured in the grass may be one of the features explaining the presence of this species in the maritime Antarctic. The net photosynthesis response to intercellular CO2 (A/ci ) for D. antarctica was typical of a C3 plant. Exposure to a biologically effective UV-B irradiance of 0.74 W M-2 did not result in any significant change in either the maximum rate of photosynthesis at saturating CO2 and light, or in the initial carboxylation efficiency of Rubisco. (Vc,max ). Furthermore while ambient (or enhanced) solar UV-B did not affect photochemical yield, measured in the field, of C. quitensis and D. antarctica , UV-B enhancement did affect negatively photochemical yield in S. uncinata . In D. antarctica plants, exposure to UV-B at low irradiances elicited increased flavonoid synthesis. The observed effects of UV-B enhancement on the moss (decreased photochemical yield) and the grass (increase in flavonoids) require further, separate investigation. 相似文献
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José Luis Montiel‐Escobar Víctor Alcaraz‐González Hugo Oscar Méndez‐Acosta Victor González‐Álvarez 《洁净——土壤、空气、水》2012,40(9):933-940
A robust state estimation scheme is proposed for anaerobic digestion (AD) processes to estimate key variables under the most uncertain scenarios (namely, uncertainties on the process inputs and unknown reaction and specific growth rates). This scheme combines the use of the IWA Anaerobic Digestion Model No. 1 (ADM1), the interval observer theory and a minimum number of measurements to reconstruct the unmeasured process variables within guaranteed lower and upper bounds in which they evolve. The performance of this robust estimation scheme is evaluated via numerical simulations that are carried out under actual operating conditions. It is shown that under some structural and operational conditions, the proposed robust interval observer (RIO) has the property of remaining stable in the face of uncertain process inputs, badly known kinetics and load disturbances. It is also shown that the RIO is indeed a powerful tool for the estimation of biomass (composed of seven different species) from a minimum number of measurements in a system with a total of 32 variables from which 24 correspond to state variables. 相似文献
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