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The structuring and organizing effects of apex predators on ecosystems are becoming increasingly well documented. The enhancement of kelp forests via sea otter predation on herbivorous sea urchins is among the earliest and best known examples. This study provides evidence for direct and indirect trophic interactions among sea otters, predatory sea stars, and filter-feeding mussels (Mytilus trossulus) and barnacles (Semibalanus cariosis). In western Massacre Bay at Attu Island (173°E, 53°N), subtidal transects showed sea star body size and biomass density declined markedly between 1983 and 1994 as sea otters reinhabited this area. Mussels and barnacles translocated from the rocky intertidal zone to shallow subtidal habitats to assess loss rates from sea star predation showed lower mortality rates after the arrival of sea otters. Prey mortality rates in subtidal caged controls were consistently low and similar to those of intertidal controls in both years. These findings elucidate a trophic pathway by which sea otters can influence ecosystems separate from the well-known sea otter/sea urchin/macroalgae cascade. 相似文献
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Hari Eswaran Diana Escalona-Vargas Elijah H. Bolin James D. Wilson Curtis L. Lowery 《黑龙江环境通报》2017,37(2):193-196
Fetal magnetocardiography provides the requisite precision for diagnostic measurement of electrophysiological events in the fetal heart. Despite its significant benefits, this technique with current cryogenic based sensors has been limited to few centers, due to high cost of maintenance. In this study, we show that a less expensive non-cryogenic alternative, optically pumped magnetometers, can provide similar electrophysiological and quantitative characteristics when subjected to direct comparison with the current technology. Further research can potentially increase its clinical use for fetal magnetocardiography. © 2016 John Wiley & Sons, Ltd. 相似文献
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Abstract: Because ambient temperature strongly influences reproduction in frogs, the seasonal timing of frog calling provides a sensitive index of biotic response to climate change. Over the last century, daily temperatures increased during 5 of the 8 months key to gametogenesis in frogs and toads near Ithaca, New York ( U.S.A.). Earliest dates of calling frogs recorded by Albert Hazen Wright between 1900 and 1912 near Ithaca were compared to those from the New York State Amphibian and Reptile Atlas Project for 1990–1999 for the three counties surrounding Ithaca. Four species are now calling 10–13 days earlier, two are unchanged, and none is calling later. The data suggest that climate has warmed in central New York State during this century and has resulted in earlier breeding in some amphibians—a possible first indication of biotic response to climate change in eastern North America. 相似文献
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