Evaluation of multiple management objectives for Northeast Atlantic flatfish stocks: sustainability vs. stability of yield   总被引：1，自引：4，他引：1  

Kell  L.T.; Pastoors  M.A.; Scott  R.D.; Smith  M.T.; Van Beek  F.A.; O'Brien  C.M.; Pilling  G.M. 《ICES Journal of Marine Science》2005,62(6):1104-1117

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Black-legged kittiwakes as indicators of environmental change in the North Sea: Evidence from long-term studies     

S. Wanless  M. Frederiksen  B.E. Scott 《Progress in Oceanography》2007,72(1):30-38

Top predators, particularly seabirds, have repeatedly been suggested as indicators of marine ecosystem status. One region currently under pressure from human fisheries and climate change is the North Sea. Standardized seabird monitoring data have been collected on the Isle of May, an important seabird colony in the northwestern North Sea, over the last 10-20 years. Over this period oceanographic conditions have varied markedly, and between 1990 and 1999 a major industrial fishery for sandlance (Ammodytes marinus), the main prey of most seabird species, was prosecuted nearby. Sandlance fishing grounds close to seabird colonies down the east coast of the UK were closed in 2000 in an attempt to improve foraging opportunities for breeding seabirds, particularly black-legged kittiwakes (Rissa tridactyla). Initially this closure seemed to be beneficial for kittiwakes with breeding success recovering to pre-fishery levels. However, despite the ban continuing, kittiwakes and many other seabird species in the North Sea suffered severe breeding failures in 2004. In this paper, we test the predictive power of four previously established correlations between kittiwake breeding success and climatic/trophic variables to explain the observed breeding success at the Isle of May in 2004. During the breeding season, kittiwakes at this colony switch from feeding on 1+ group to 0 group sandlance, and results up until 2003 indicated that availability of both age classes had a positive effect on kittiwake breeding success. The low breeding success of kittiwakes in 2004 was consistent with the late appearance and small body size of 0 group sandlance, but at odds with the two variables likely to operate via 1 group availability (lagged winter sea surface temperature and larval sandlance cohort strength in 2003). The reason for the discrepancy is currently unknown, but analysis of 1 group sandlance body composition indicated that lipid content in 2004 was extremely low, and thus fish eaten by kittiwakes during pre-breeding and early incubation were likely to be of poor quality. Monitoring of reproductive success of kittiwakes, although useful, was clearly not sufficient to tease apart the complex causation underlying the 2004 event. Monitoring programs such as this, therefore, need to be complemented by detailed research to identify the mechanisms involved, and to attribute and predict the effects of natural and human-induced environmental change.  相似文献   

Ecosystem-based management of fisheries: is science limiting?   总被引：4，自引：0，他引：4  

Frid  Chris L.J.; Paramor  Odette A.L.; Scott  Catherine L. 《ICES Journal of Marine Science》2006,63(9):1567-1572

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What causes the adiabatic lapse rate?     

Trevor J McDougall  Rainer Feistel 《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1523-1535

The adiabatic lapse rate is commonly explained as being proportional to the work done on a fluid parcel as its volume changes in response to an increase in pressure. According to this explanation the adiabatic lapse rate would increase with both pressure and the fluid's compressibility, but this is not the case. Rather, the adiabatic lapse rate is proportional to the thermal expansion coefficient and is independent of the fluid's compressibility. Here we show that the adiabatic lapse rate is independent of the increase in the internal energy that a parcel experiences when it is compressed. We explain what is missing from the traditional explanation of the adiabatic lapse rate and we explore the thermodynamic cause of the adiabatic lapse rate. In particular, we seek to explain how the adiabatic lapse rate can be negative in cool fresh water.  相似文献   

Changes in the cetacean assemblage of a coastal upwelling ecosystem during El Niño 1997–98 and La Niña 1999     

Scott R. Benson  Donald A. Croll  Baldo B. Marinovic  Francisco P. Chavez  James T. Harvey 《Progress in Oceanography》2002,54(1-4)

We report results of ecosystem studies in Monterey Bay, California, during the summer upwelling periods, 1996–99, including impacts of El Niño 1997–98 and La Niña 1999. Random-systematic line-transect surveys of marine mammals were conducted monthly from August to November 1996, and from May to November 1997–99. CTDs and zooplankton net tows were conducted opportunistically, and at 10 predetermined locations. Hydroacoustic backscatter was measured continuously while underway to estimate prevalence of zooplankton, with emphasis on euphausiids, a key trophic link between primary production and higher trophic level consumers.The occurrences of several of the California Current’s most common cetaceans varied among years. The assemblage of odontocetes became more diverse during the El Niño with a temporary influx of warm-water species. Densities of cold-temperate Dall’s porpoise, Phocoenoides dalli, were greatest before the onset of El Niño, whereas warm-temperate common dolphins, Delphinus spp., were present only during the warm-water period associated with El Niño. Rorqual densities decreased in August 1997 as euphausiid backscatter was reduced. In 1998, as euphausiid backscatter slowly increased, rorqual densities increased sharply to the greatest observed values. Euphausiid backscatter further increased in 1999, whereas rorqual densities were similar to those observed during 1998. We hypothesize that a dramatic reduction in zooplankton biomass offshore during El Niño 1997–98 led to the concentration of rorquals in the remaining productive coastal upwelling areas, including Monterey Bay. These patterns exemplify short-term responses of cetaceans to large-scale changes in oceanic conditions.  相似文献   

Mississippi-Alabama outer continental shelf topographic features formed during the late Pleistocene-Holocene transgression     

William W. Sager  William W. Schroeder  J. Scott Laswell  Kenneth S. Davis  Richard Rezak  Stephen R. Gittings 《Geo-Marine Letters》1992,12(1):41-48

A geophysical survey of the outer Missisippi-Alabama continental shelf revealed three types of topographic features: 1) reef-like mounds (RLM), 2) isobath-parallel ridges, and 3) shallow depressions. RLM appear to be bioherms. Their bases cluster in two isobath bands, 105 to 120 m and 74 to 82 m, implying the late Pleistocene-Holocene transgression was nonuniform. The deeper RLM probably formed during a slow sea level rise at the beginning of the deglaciation. An 11 ka BP C¹⁴ age was obtained from the summit of one, at a depth of 90 m. Depth relationships suggest the shallower RLM and most ridges formed about the time of the mid-deglacial Younger Dryas cooling episode.  相似文献   

Field assessment of biochemical stress indices for the sandworm Neanthes virens (Sars)     

Robert Scott Carr  Jerry M. Neff 《Marine environmental research》1984,14(1-4)

Certain biochemical stress responses have been observed in the laboratory for Neathhes virens subjected to various environmental and pollutant stressors. The purpose of the present study was to determine whether similar alterations in these biochemical parameters could be detected in a natural population of N. virens from a contaminated site as compared with animals from a nearby reference site. A site in Portland Harbor, Maine, adjacent to an oil storage facility with oil-contaminated sediments was selected as the experimental study area and the reference site was at Pine Point, approximately 15 miles south of Portland.Animals were collected from the two sites on consecutive days on a bimonthly basis at low tide within a day of the full moon from September 1981 through March 1982. Coelomic fluid samples were taken within 2 h after collection and the animals were then frozen in liquid nitrogen for transport back to the laboratory. Coelomic fluid samples were analyzed for glucose and the frozen tissues were analyzed for glycogen, lipid and free amino acid concentrations.Significant differences in these parameters were often observed between the two populations. The glycogen content of animals from the contaminated site was always less than that of animals from the reference site, whereas the lipid levels were always higher. Significant differences between the free amino acid composition of the animals from the two sites were also observed. Although distinct biochemical differences can be detected between these two populations, the considerable biological variation in these parameters may limit their usefulness for field monitoring investigations for this species.  相似文献   

Exceedance probability for wave overtopping on a fixed deck     

Daniel T. Cox  Christopher P. Scott 《Ocean Engineering》2001,28(6):977

Detailed laboratory measurements were made of the instantaneous free surface elevation in front of a fixed deck and the instantaneous free surface elevation, velocity, and overtopping rate at the leading edge of the deck. The study showed that the exceedance probabilities for the normalized maximum instantaneous overtopping rate and the normalized overtopping volume were predicted by a simple exponential curve. The measured exceedance probability seaward of the deck compared well with the nonlinear theory of Kriebel and Dawson (Kriebel D.L., Dawson T.H., 1993. Nonlinearity in wave crest statistics. In: Proceedings Ocean Wave Measurement and Analysis. American Society of Civil Engineers, pp. 61–75). Conditional sampling of the crest heights seaward of the deck gave a normalized probability distribution similar to that of the maximum water level measured on the deck for each overtopping event. However, the values used to normalize each distribution were not the same.  相似文献   

Eutrophication and the rate of net nitrification in a coastal marine ecosystem     

Veronica M. Berounsky  Scott W. Nixon 《Estuarine, Coastal and Shelf Science》1985,20(6):773-781

Rates of net nitrification were calculated for four large (13 m³) estuarine-based microcosms that had been subjected to inorganic nutrient enrichment. Calculated rates were based on two years of weekly nitrate and nitrite measurements and ranged from a maximum of 0·55 μmol NO₂₊₃⁻ produced l⁻¹ day⁻¹ in the control tank (no enrichment) to over 13 μmol NO₂₊₃⁻ produced l⁻¹ day⁻¹ in the most enriched tank (receiving 18·6 μmol NH₄ l⁻¹ day⁻¹). Almost all NO₂₊₃⁻ production was pelagic, little was benthic. Net NO₃⁻ production or net NO₂⁻ production dominated the net nitrification rates during different seasons. Good correlations were found between various oxidation rates and substrate concentrations. The calculated net nitrite production rates were 10 to 1000 times higher than previously reported rates for open ocean systems, demonstrating the potential importance of nitrification to estuarine systems.  相似文献   

Suspended sediment transport in surface waters of the California Current off southern California: 1977–78 floods     

Scott E. Thornton 《Geo-Marine Letters》1981,1(1):23-28

Floods in southern California during the rainy season of 1977–78 followed four years of severe drought when vegetative cover of drainage areas was at a minimum. LANDSAT Band 5 analyses following these floods suggest extensive transport of suspended sediment to 80 to 100 km from the coastline. Current patterns can be explained by a decaying Davidson Current situation and a large semipermanent cyclonic gyre that controls distribution of surface suspended sediment throughout the California Borderland. This gyre, and associated spinoff eddies, produce three distinct cells of suspended sediment in surface waters. These cells may control sedimentation patterns of terrigenous silt and clay.  相似文献