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111.
Menhaden are one of the most abundant components of fish communities in Gulf and Atlantic estuaries. Juvenile menhaden have been reported to have zooplankton, phytoplankton, andSpartina-derived detritus in their guts. However, there has been disagreement over the importance of the detritus as a food source. We show, using physiological and stable isotope evidence, that detritus can be used by juvenile Gulf menhaden. Their diet is very roughly 30% detritus- and 70% plankton-based. 相似文献
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Some of the factors that affect the preferred positions of cations in ionic-solid solutions were investigated utilizing vibrational spectroscopy. Solid solutions of the sulfate and chromate ions codoped with La3+ and Ca2+ in a KBr host lattice were examined as a function of the polyvalent-cation concentration. The cation—anion pairing process was found to be random for Ca2+ whereas the formation of La3+SO42? ion-pairs with a C2v bonding geometry is highly preferential to any type of La3+CrO42? ion-pair formation. The relative populations of ion-pair site configurations are discussed in terms of an energy—entropy competition which can be applied to the partition of trace elements during magmatic processes. 相似文献
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Chlorophyll a of total and particles retained on 30 μm mesh plankton net were both determined in surface waters along two cruise tracks
ranging from the Subtropical water to the marginal ice zone in the Pacific sector of the Southern Ocean in austral summer.
Total surface chlorophyll a in the study area was mostly less than 1 μg chl a 1−1, and showed distributions with no obvious trend associated with different waters masses of the Antarctic and the Subantarctic,
although total chlorophyll a concentrations changed greatly within each water mass. Particularly low concentrations of chlorophyll a were detected in the marginal ice zone. Chlorophyll a contained in 30 μm netplankton made up 5∼60% of total chlorophyll a: large near the marginal ice zone and becoming small with travel towards the north. High percentage shares of netplankton
chlorophyll a were confirmed even in low total chlorophyll a concentrations in summer in the Southern Ocean. A positive relation was observed between the percentage of 30 μm netplankton
and the “average total chlorophyll a”, although there was great scatter.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Bryan W. Stiles Scott Hensley David M. Bates Alex Hayes Ralph D. Lorenz Philip S. Callahan William T.K. Johnson Jonathan I. Lunine Michael Janssen Richard D. West the Cassini RADAR Team 《Icarus》2009,202(2):584-598
A technique, referred to as SARTopo, has been developed for obtaining surface height estimates with 10 km horizontal resolution and 75 m vertical resolution of the surface of Titan along each Cassini Synthetic Aperture Radar (SAR) swath. We describe the technique and present maps of the co-located data sets. A global map and regional maps of Xanadu and the northern hemisphere hydrocarbon lakes district are included in the results. A strength of the technique is that it provides topographic information co-located with SAR imagery. Having a topographic context vastly improves the interpretability of the SAR imagery and is essential for understanding Titan.SARTopo is capable of estimating surface heights for most of the SAR-imaged surface of Titan. Currently nearly 30% of the surface is within 100 km of a SARTopo height profile. Other competing techniques provide orders of magnitude less coverage.We validate the SARTopo technique through comparison with known geomorphological features such as mountain ranges and craters, and by comparison with co-located nadir altimetry, including a 3000 km strip that had been observed by SAR a month earlier. In this area, the SARTopo and nadir altimetry data sets are co-located tightly (within 5-10 km for one 500 km section), have similar resolution, and as expected agree closely in surface height. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and precision of both techniques. 相似文献
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