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621.
Takashi Kamiyama 《Journal of Oceanography》2018,74(1):53-63
Blooms of the moon jellyfish, Aurelia coerulea, often occur in eutrophic embayments where microzooplankton are abundant. Hence, microzooplankton may play a role in A. coerulea population dynamics. In this study, feeding and growth responses of the ephyra and metephyra stages of A. coerulea were examined on a diet of planktonic ciliates, the main components of microzooplankton. Laboratory experiments indicated that ephyrae actively fed on ciliates and that the central disc diameter increased over the 5-day incubation period. Carbon-specific growth rates estimated from daily increases of central disc diameter increased with carbon-specific prey consumption rates until about 4 µg C ind day?1 and then became saturated. By fitting these results to rectangular hyperbolic equations, the maximum specific growth rates were estimated to be 0.32 day?1 for ciliate prey. However, the central disc diameter of the metephyrae did not increase on a diet of ciliates during the 5-day incubation, even though consumption of prey ciliates was observed. These results suggest that planktonic ciliates serve as a food source for growth at the ephyra stage of A. coerulea and then the contribution to growth decreases at and after the metephyra stage. This prey switch-dependency on the development stage of A. coerulea may be associated with the frequent occurrence of jellyfish blooms in eutrophic embayments. 相似文献
622.
Hayao Morinaga Hiroo Inokuchi Hideki Yamashita Akira Ono Takashi Inada 《Geoarchaeology》1999,14(5):377-399
We present a methodological approach to detect heated soil on ancient sites, using magnetic measurements. The method is based on changes in magnetic signals of soil by heating. The following three types of soil were used for testing the method: silty soil (SS), weathered volcanic ash (WVA, = loam) and fairly fresh volcanic ash (VA) called Odori tephra. On heating above 250–600°C, the magnetic susceptibility and remanent magnetization intensity increased for the SS and WVA samples, reflecting chemical alteration of magnetic minerals (from goethites to magnetites through hematites). The VA sample showed no susceptibility change suggesting the absence of goethites within it. On heating below 250°C, only the intensities of all the samples increased. This is possibly due to acquisition of thermal remanent magnetization. The largest change of the magnetic signals was identified for the SS sample and the smallest one was seen for the VA sample. Therefore, the in situ susceptibility measurement, which is the nondestructive and indirect method, seems to be effective to detect heated soil for sites of aqueous deposits as the SS. On the other hand, for sites of aeolian deposits as the WVA (loam) and VA, the intensity measurement of collected soils seems to be the most reliable method to detect evidence of heating. The degree of the magnetic stability (coercivity) against progressive alternating-field demagnetization was also an important parameter, indicating whether the investigated soils were heated or unheated. © 1999 John Wiley & Sons, Inc. 相似文献