Effects of metals on sea urchin development: A rapid bioassay     

Harold H. Lee  C.H. Xu 《Marine pollution bulletin》1984,15(1):18-21

Embryos of sea urchins show a differential response to Cd, Cu, Cr, Ni and Zn. The responses are also stage-specific. The different morphological effects of various metals reflect the differentiation of the early embryonic cells. Since fertilization can be inhibited in the presence of metals, especially Cu, the ability of the gametes to undergo fertilization can then be used as a biological indicator for a rapid assay, 10–20 min., of marine pollutants. Since embryo-genesis up to plutei stage requires only 20 h, this duration is also short compared to other systems utilizing embryonic or larval forms.  相似文献   

Reducing Drift and Bias of a Global Ocean Model by Frequency-Dependent Nudging     

Zhongjie He  Keith R. Thompson  Harold Ritchie  Youyu Lu  Frederick Dupont 《大气与海洋》2014,52(3):242-255

Frequency-dependent nudging is applied to a coarse resolution (nominal 1°) global ocean model to suppress its drift and bias, and the impact of the nudging on the skill of the model is assessed. The nudging is applied to temperature and salinity in frequency bands centred on 0 and 1 cycles per year. As expected, the nudging significantly reduces the biases in the long-term mean and annual cycle of temperature, salinity, and sea level. By comparing the simulated (i) sea surface temperature with operational analyses based on observations, (ii) vertical profiles of temperature and salinity with observations made by Argo floats, and (iii) sea level with altimeter observations, it is shown that the skill of the model in simulating variability about the annual cycle is also improved. The potential benefit of applying frequency-dependent nudging to the ocean component of a coupled atmosphere–ocean model is discussed.  相似文献   

2014 Leonard Medal for Roger H. Hewins     

Harold C. Connolly Jr. 《Meteoritics & planetary science》2014,49(10):1978-1979

  相似文献   

Sub-annual moraine formation at an active temperate Icelandic glacier     

Benjamin M.P. Chandler  Samuel J.P. Chandler  David J.A. Evans  Marek W. Ewertowski  Harold Lovell  David H. Roberts  Martin Schaefer  Aleksandra M. Tomczyk 《地球表面变化过程与地形》2020,45(7):1622-1643

This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterized by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognize two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low-relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub-annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub-annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt-driven squeeze events and (ii) larger push moraines formed during winter re-advances. We suggest the development of this process-form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice-marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process-form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Prehistoric life on the Mississippi Floodplain. Richard W. Yerkes, 1987, the University of Chicago Press,Prehistoric Archeology and Ecology Series, 279 pp., $25.00 (clothbound), $10.00 (paperbound)     

Harold Hassen 《Geoarchaeology》1988,3(2):168-169

  相似文献   

The peruvian anchoveta and its upwelling ecosystem: Three Decades of Change. D. Pauly and I. Tsukayama,Eds., 1987, International Center for Living Aquatic Resources Management (available from International Specialized Book Services,P.O. Box 1632, Beaverton,OR 970751, 351 pp., $36.00     

Harold B. Rollins 《Geoarchaeology》1988,3(4):306-307

  相似文献   

Provenances and dispersal patterns of turbidite sand in Escanaba Trough,northeastern Pacific Ocean     

T.L. Vallier  P.J. Harold  W.A. Girdley 《Marine Geology》1973,15(2):67-87

Escanaba Trough, the median valley of Gorda Ridge, is partly filled with terrigenous sediment which was eroded mostly from rocks in the Klamath and Columbia River drainage basins and transported across the sea floor to the trough by turbidity currents. Basal or lower cores contain sand derived from the south-central metamorphic belt of the Klamath Mountains, whereas the upper cores have sand derived from the Columbia River drainage basin. Columbia River sediment reached Escanaba Trough either after a barrier at Blanco Valley had been destroyed by tectonic movement or after a gradient, sufficient to maintain turbidity current momentum, had developed between the Astoria Fan apex and the trough. Sediment in Escanaba Trough is young and most probably was deposited when sea level was lower than at present, perhaps during the Wisconsin Glacial Age.  相似文献   

The birth of El Niño: Geoarchaeological evidence and implications     

Harold B. Rollins  James B. Richardson  Daniel H. Sandweiss 《Geoarchaeology》1986,1(1):3-15

The oceanographic phenomenon known as El Niño is the subject of intensive recent study. Any hypotheses regarding physical causes and predictability of El Niño should consider its geological history. New geoarchaeological evidence suggests that the El Niño phenomenon did not exist along the northern and central coasts of Peru before about 5000 years B.P. Molluscan faunas from archaeological sites at Pampa las Salinas and Salinas de Chao permit temporal bracketing of a major structural change in the East Pacific water mass. The boundary between the warm Panamic Province and the cold Peruvian Province, which today occurs at about 5 degrees south latitude, was some 500 km further south from at least 11,000 years B.P. to about 5000 years B.P. This conclusion is corroborated by many other lines of evidence including phosphorite distribution, timing of glacial retreat, sea level change, radiolarian, diatom and fish scale distributions, and beach ridge patterns. The present day arid coastal climate of north central Peru is probably a post-5000 year B.P. development. Hunter–gatherer populations of the area would most likely have exploited more land-based seasonal resources from grasslands and forests before 5000 years B.P., and relied less upon the diminished productivity of warm water maritime resources.  相似文献