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61.
Gray's Reef National Marine Sanctuary (GRNMS) is an increasingly popular site for recreational fishing and diving in the South Atlantic Bight (SAB). As a result, there has been heightened concern about potential accumulation of marine debris and its consequent effects on sanctuary resources. Field surveys were conducted at GRNMS in 2004 and 2005 to provide a spatially comprehensive characterization of benthic communities and to quantify the distribution and abundance of marine debris in relation to bottom features. The spatial distribution of debris was concentrated in the center of the sanctuary and was most frequently associated with ledges rather than other bottom types. On ledges, the presence and abundance of debris was significantly related to observed boating activity and physiographic features including ledge height, ledge area, and percent cover of benthic organisms. The results from this study will aid managers in optimizing cleanup efforts and long-term monitoring of debris accumulation patterns at GRNMS and other hard bottom areas in the SAB. 相似文献
62.
Shelley M. Blackwell Mark A. Moline Andrew Schaffner Thomas Garrison Grace Chang 《Continental Shelf Research》2008
Patchiness or spatial variability is ubiquitous in marine systems. With increasing anthropogenic impacts to coastal resources and coastal systems being disproportionately large contributors to ocean productivity, identifying the spatial scales of this patchiness, particularly in coastal waters, is of critical importance to understand coastal ecosystem dynamics. The current work focuses on fine scale structure in three coastal regions. More specifically, we utilize variogram analyses to identify sub-kilometer scales of variability in biological and physical parameters measured by an autonomous underwater vehicle (AUV) in the Mid-Atlantic Bight, Monterey Bay, and in San Luis Obispo Bay between 2001 and 2004. Critical scales of variability in density, turbidity, fluorescence, and bioluminescence are examined as a function of depth and distance offshore. Furthermore, the effects of undersampling are assessed using predictive error analysis. Results indicate the presence of scales of variability ranging from 10s to 100s of meters and provide valuable insight for sampling design and resource allocation for future studies. 相似文献
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Potential climate-change impacts on the Chesapeake Bay 总被引:1,自引:0,他引:1
Raymond G. Najjar Christopher R. Pyke Mary Beth Adams Denise Breitburg Carl Hershner Michael Kemp Robert Howarth Margaret R. Mulholland Michael Paolisso David Secor Kevin Sellner Denice Wardrop Robert Wood 《Estuarine, Coastal and Shelf Science》2010
We review current understanding of the potential impact of climate change on the Chesapeake Bay. Scenarios for CO2 emissions indicate that by the end of the 21st century the Bay region will experience significant changes in climate forcings with respect to historical conditions, including increases in CO2 concentrations, sea level, and water temperature of 50–160%, 0.7–1.6 m, and 2–6 °C, respectively. Also likely are increases in precipitation amount (very likely in the winter and spring), precipitation intensity, intensity of tropical and extratropical cyclones (though their frequency may decrease), and sea-level variability. The greatest uncertainty is associated with changes in annual streamflow, though it is likely that winter and spring flows will increase. Climate change alone will cause the Bay to function very differently in the future. Likely changes include: (1) an increase in coastal flooding and submergence of estuarine wetlands; (2) an increase in salinity variability on many time scales; (3) an increase in harmful algae; (4) an increase in hypoxia; (5) a reduction of eelgrass, the dominant submerged aquatic vegetation in the Bay; and (6) altered interactions among trophic levels, with subtropical fish and shellfish species ultimately being favored in the Bay. The magnitude of these changes is sensitive to the CO2 emission trajectory, so that actions taken now to reduce CO2 emissions will reduce climate impacts on the Bay. Research needs include improved precipitation and streamflow projections for the Bay watershed and whole-system monitoring, modeling, and process studies that can capture the likely non-linear responses of the Chesapeake Bay system to climate variability, climate change, and their interaction with other anthropogenic stressors. 相似文献
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66.
Simon Allerton Bramley J. Murton Roger C. Searle Malcolm Jones 《Marine Geophysical Researches》1995,17(1):37-61
The combination of multi-beam echo-sounder swath bathymetry and high-resolution deep-towed sidescan sonar provides a powerful database from which to examine mid-ocean ridge processes. We have used such a database, gathered from the Mid-Atlantic Ridge north of the Kane Fracture Zone (the MARNOK area), to examine the relationship between tectonic, volcanic, and bathymetric segmentation. We have identified structural domains, with different fault distributions, and neovolcanic segments that are distinct from the 2nd or 3rd order bathymetric segmentation.From their mutual relationships, a model is proposed for the magmatic accretion of oceanic crust at slow spreading ridges that relates the local melt supply to the tectonic style. We suggest that these are mutually interactive, and determine whether volcanic extrusion along the ridge is continuous and slow, or episodic and rapid. 相似文献
67.
Dissolved organic carbon (DOC) is the largest organic carbon reservoir in sea water and plays an imporrant role in the marine carbon cycle and other biogeochemical processes in the ocean. Accurate and precise determinalion of the bOC concentration in sea water is thus a prerequisite for any interpretation of DOC biogeochemistry. A key factor in analytical quality control is an accurate determination of the blank. The assessment and distinction of DOC blanks are essential for the precise measurements of oceanic DOC. The total DOC blank includes instrument and water blanks in the high temperature catalytic oxidation (HTCO) method. DOC can be measured accurately using the HTCO method only when the instrument blank is correctly distinguished from the total DOC blank and corrected in the sample measurements. Low DOC blanks can be achieved by extensive conditioning of new catalysts and the whole instrument system, whereas instrument blanks can be quantified by subtracting the water blank from the total DOC blank. We have been able to produce low carbon nanopure water [≤2μmol/dm3(C)] and have a low instrumental blank [< 5-6 μmol/dm3(C)] when using the HTCO method. Results of concentrations and distributions of DOC in the Gulf of Mexico and the North Atlantic are oceanographically consistent. Results from DOC measurements on samples from the international DOC methods comparison program further confirmed our low values of both nenopure water and the instrument blank. 相似文献
68.
G. M. Purdy J. -C. Sempere H. Schouten D. L. Dubois R. Goldsmith 《Marine Geophysical Researches》1990,12(4):247-252
This paper presents a series of eleven maps of the bathymetry of a 900 km long section of the crestal region of the Mid-Atlantic
Ridge. Along with a twelfth key map, this series defines the morphology of fifteen discrete spreading segments and shows convincingly
that no transform faults exist between the Kane and Atlantis fracture zones. The publication of these multi beam bathymetry
data with a contour interval of 50 m and at a scale of 30 inches per degree of longitude is intended to allow easy access
by a broad community of marine earth scientists to this unique and powerful data set. 相似文献
69.
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The 1989 German Bight invasion of Muggiaea atlantica 总被引:4,自引:0,他引:4