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Adriana Giangrande 《Marine Ecology》2013,34(2):255-256
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During the 2003-2004 winter season, the U.S. Office of Naval Research (ONR, Arlington, VA), sponsored a detailed in situ study of the mine burial process resulting from wave-seafloor-mine interaction at Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). In total, 16 mine shapes were deployed. Six were the Forschungsanstalt der Bundeswehr fur Wasserschall und Geophysik (FWG, Kiel, Germany) burial registration mines using optical sensors, four others were equipped with acoustical sensors, and six were simple shapes. Repeated acoustic surveys and detailed sediment sampling were conducted to characterize the site and the burial status of all objects. This paper focuses on data from three recovered optical systems. The records show three roll events at all three registration mines, which are necessary for scour burial. Two systems experienced a fourth roll event. Results from earlier experiments suggest only three (four) stages of progressively increasing burial despite frequent successive burial and exposure cycles (some as short as 1 h). During these burial-exposure cycles changes of buried mine volume reached up to 80%. The only reasonable explanation is a change of sediment height of up to 40 cm relative to the stably lying mines. This requires new concepts. Cyclic burial changes that were observed simultaneously at different positions cannot be explained with existing models. The least difficult explanation is ldquounderwater sand stormsrdquo which are characterized by a high sediment suspension. 相似文献
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Anne M. Slaughter Stephen M. Bollens Gretchen Rollwagen Bollens 《Deep Sea Research Part II: Topical Studies in Oceanography》2006,53(25-26):3099
Mesozooplankton (>200 μm) grazing impact (% phytoplankton standing crop consumed d−1) was determined by the gut fluorescence method during three springs (2000, 2001 and 2002) and two winters (2002 and 2003) in a coastal upwelling region off northern California. Wind events, in terms of both magnitude and duration, varied inter-annually and seasonally and included both upwelling-favorable and relaxation events. Grazing impact of mesozooplankton also varied inter-annually and seasonally, and was highest during June 2000 (mean=129% of standing crop d−1), a prolonged period of wind “relaxation” and phytoplankton bloom. In contrast, mean grazing impact was lower during periods of stronger, more persistent winds, more active upwelling, greater cross-shelf transport, and lower chlorophyll concentration (25% and 38% in May–June 2001 and 2002, respectively). Wintertime conditions (January 2002 and 2003) were characterized by weakly upwelling or downwelling-favorable winds, low chlorophyll concentration, and lower mean mesozooplankton grazing impact (13% and 12%, respectively). The larger (>500 μm) size class contributed proportionally more to total mesozooplankton (>200 μm) grazing impact than the smaller (200–500 μm) size class during all sampling periods except spring 2002. These results suggest that mesozooplankton grazing impact is higher in spring than in winter, and that during the spring upwelling season, grazing is higher during periods of wind relaxation (weak upwelling) than during periods of stronger upwelling. Further, these results suggest an important role of mesozooplankton grazers on phytoplankton dynamics in the upwelling region off northern California. 相似文献