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2002

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Oceanography and Atmospheric Sciences and Meteorology

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Articles 1 - 30 of 190

Full-Text Articles in Physical Sciences and Mathematics

On The Effect Of Random Errors In Gridded Bathymetric Compilations, Martin Jakobsson, Brian R. Calder, Larry A. Mayer Dec 2002

On The Effect Of Random Errors In Gridded Bathymetric Compilations, Martin Jakobsson, Brian R. Calder, Larry A. Mayer

Center for Coastal and Ocean Mapping

We address the problem of compiling bathymetric data sets with heterogeneous coverage and a range of data measurement accuracies. To generate a regularly spaced grid, we are obliged to interpolate sparse data; our objective here is to augment this product with an estimate of confidence in the interpolated bathymetry based on our knowledge of the component of random error in the bathymetric source data. Using a direct simulation Monte Carlo method, we utilize data from the International Bathymetric Chart of the Arctic Ocean database to develop a suitable methodology for assessment of the standard deviations of depths in the interpolated …

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A Simulation Study Of Space-Based Observations Of Gravity Waves In The Airglow Using Observed Aloha-93 Wave Parameters, Michael P. Hickey Ph.D., J. S. Brown Dec 2002

A Simulation Study Of Space-Based Observations Of Gravity Waves In The Airglow Using Observed Aloha-93 Wave Parameters, Michael P. Hickey Ph.D., J. S. Brown

Publications

We use gravity wave parameters derived from the ALOHA-93 campaign to model four gravity waves in airglow emissions as observed from the ground to numerically predict whether these waves could have been observed from space. In spite of encountering critical levels, some waves may still be observed in the airglow provided the critical level lies within the airglow emission region. One of the four waves experiences a critical level in the lower region of an airglow layer such that the disturbance to the volume emission rate would be effectively limited to a short distance along a satellite line of sight. …

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Arctic Ocean Physiography, Martin Jakobsson, Arthur Grantz, Yngue Kristoffersen, Ron Macnab Dec 2002

Arctic Ocean Physiography, Martin Jakobsson, Arthur Grantz, Yngue Kristoffersen, Ron Macnab

Center for Coastal and Ocean Mapping

The first order physiographic provinces of the Arctic Ocean has been defined using the recently updated International Bathymetric Chart of the Arctic Ocean (IBCAO) grid model as the main database and a semi-quantitative approach. The first step in our classification of physiographic provinces is an evaluation of seafloor gradients contained in a slope model that was derived from the IBCAO grid. The slope information reveals certain seafloor process-related features, which add to the bathymetric information. Using interactive 3D-visualization, the slope and bathymetric information were simultaneously analyzed and certain slope intervals of the Arctic Ocean seafloor were found to generally characterize …

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Multi-Scale Visualization Of Remote Sensing And Topographic Data Of The Amazon Rain Forest, Luciano E. Fonseca, F P. Miranda, C Beisl, J Souza-Fonseca Dec 2002

Multi-Scale Visualization Of Remote Sensing And Topographic Data Of The Amazon Rain Forest, Luciano E. Fonseca, F P. Miranda, C Beisl, J Souza-Fonseca

Center for Coastal and Ocean Mapping

PETROBRAS (the Brazilian national oil company) built a pipeline to transport crude oil from the Urucu River region to a terminal in the vicinities of Coari, a city located in the right margin of the Solimoes River. The oil is then shipped by tankers to another terminal in Manaus, capital city of the Amazonas state. At the city of Coari, changes in water level between dry and wet seasons reach up to 14 meters. This strong seasonal character of the Amazonian climate gives rise to four distinct scenarios in the annual hydrological cycle: low water, high water, receding water, and …

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Lake Tahoe Bottom Characteristics Extracted From Shoals Lidar Waveform Data And Compared To Backscatter Data From A Multibeam Echo Sounder, G. Elston, James V. Gardner Dec 2002

Lake Tahoe Bottom Characteristics Extracted From Shoals Lidar Waveform Data And Compared To Backscatter Data From A Multibeam Echo Sounder, G. Elston, James V. Gardner

Center for Coastal and Ocean Mapping

The waveforms recorded by airborne lidar bathymetry (ALB) systems are currently processed only for depth information. In addition to bathymetry, multibeam echo sounder (MBES) systems provide backscatter data in which regions of different acoustic properties are distinguishable. These regions can often be correlated to different bottom types. Initial attempts to extract equivalent data from the ALB waveforms have confirmed the expectation that such information is encoded in those waveforms. Water clarity, bathymetry, and bottom type control the detailed shapes of ALB waveforms in different ways. Specific features of a bottom-reflected signal can be identified, for example its rise-time and amplitude, …

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Resolving The Ripples (And A Mine): High-Resolution Multibeam Survey Of Martha's Vineyard Onr Mine Burial Program Field Area, Larry A. Mayer, Richard Raymond, Gerd Glang, Lloyd C. Huff Dec 2002

Resolving The Ripples (And A Mine): High-Resolution Multibeam Survey Of Martha's Vineyard Onr Mine Burial Program Field Area, Larry A. Mayer, Richard Raymond, Gerd Glang, Lloyd C. Huff

Center for Coastal and Ocean Mapping

In an effort to better understand the coastal processes responsible for the burial and exposure of small objects on the seafloor, the Office of Naval Research is sponsoring the Mine Burial Program. Among the field areas chosen for this program is the site of the Martha's Vineyard Coastal Observatory (MVCO), a permanent instrumented node in 12 m of water about 500 m off the southern shore of Martha?s Vineyard. In support of the ONR program, several site surveys of the MVCO area have been conducted (see Goff et al); here we report the result of the most recent of these …

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Historical Changes In Mid-Water Stands Of Common Reed In The Winnebago Pool Lakes, Wisconsin, Anthony O. Gabriel, Leo R. Bodensteiner Dec 2002

Historical Changes In Mid-Water Stands Of Common Reed In The Winnebago Pool Lakes, Wisconsin, Anthony O. Gabriel, Leo R. Bodensteiner

All Faculty Scholarship for the College of the Sciences

Despite the tolerance of common reed grass to environmental extremes, mid-water stands in the Winnebago pool lakes of central Wisconsin appear to be diminishing. Formerly occupying shoreline locations, water level manipulations subsequent to dam construction beginning in the 1850's have isolated reed stands off shore. These stands have persisted but casual observations indicate that stand size has been declining. To address this perception we obtained an approximately decadal series of aerial photographs dating back to 1937 for four stands in Lake Poygan. Annual records were available for 1986–94. Using image analysis software, we determined shape and size metrics. Changes in …

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Report On The Oregon Ballast Water Management Program In 2002, Jordan Vinograd, Mark Sytsma Dec 2002

Report On The Oregon Ballast Water Management Program In 2002, Jordan Vinograd, Mark Sytsma

Center for Lakes and Reservoirs Publications and Presentations

This report documents the efficacy of the first ten months of the Oregon Ballast Water Management Program, which was established by SB 895 during the 2001 legislative session. The Oregon Ballast Water Management Program was initiated to address the introduction of aquatic nuisance species via discharge of ballast water from ships. The Program reflects the Oregon Legislature’s recognition of the potential for aquatic nuisance species to cause economic and environmental damage to the State. Oregon Laws 2001, Chapter 722 (Appendix A), required that owners and operators of certain vessels entering Oregon waters must report the time and place ballast water …

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Seafloor Characterization From Spatial Variation Of Multibeam Backscatter Vs."Best Estimated" Grazing Angle, Tianhang Hou, Larry A. Mayer, Christian De Moustier, Barbara J. Kraft Dec 2002

Seafloor Characterization From Spatial Variation Of Multibeam Backscatter Vs."Best Estimated" Grazing Angle, Tianhang Hou, Larry A. Mayer, Christian De Moustier, Barbara J. Kraft

Center for Coastal and Ocean Mapping

Backscatter vs. grazing angle, which can be extracted from multibeam backscatter data, depends on characteristics of the multibeam system and the angular responses of backscatter that are characteristic of different seafloor properties, such as sediment hardness and roughness. Changes in backscatter vs. grazing angle that are contributed by the multibeam system normally remain fixed over both space and time. Therefore, they can readily be determined and removed from backscatter data. The component of backscatter vs. grazing angle due to the properties of sediments varies from location to location, as the sediment changes. The sediment component of variability can be inferred …

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Automatic Estimation Of The Seafloor Geomorphology Of The Santos Basin, Brazil, Brian R. Calder, Luciano E. Fonseca, Joao B. Francolin Dec 2002

Automatic Estimation Of The Seafloor Geomorphology Of The Santos Basin, Brazil, Brian R. Calder, Luciano E. Fonseca, Joao B. Francolin

Center for Coastal and Ocean Mapping

The bathymetry and acoustic backscatter of Santos Basin, Brazil were mapped using a SeaBeam 2112 (12 kHz, 151 beam) Multibeam Echosounder (MBES) aboard the R/V Falcon Explorer. This MBES data was acquired from January-November, 2000, during a high-resolution multi-channel 3D seismic survey, resulting in 380 parallel lines of 90 km length, spaced 250 m apart. The final survey mapped an area of 5,000 km${}^2$ in water depths of 900--2000 m. These closely spaced multibeam tracks resulted in an average overlap between swaths of 1000%, thereby ensonifying most areas of the seafloor at least ten times. Traditional (hand) processing of a …

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An Integrated Bathymetric And Topographic Digital Terrain Model Of The Canadian Arctic Archipelago, Goran Alm, Ron Macnab, Martin Jakobsson, Johan Kleman, Mark Mccracken Dec 2002

An Integrated Bathymetric And Topographic Digital Terrain Model Of The Canadian Arctic Archipelago, Goran Alm, Ron Macnab, Martin Jakobsson, Johan Kleman, Mark Mccracken

Center for Coastal and Ocean Mapping

No abstract provided.

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The Effect Of Temperature On The Development, Growth And Survival Of Atlantic Cod (Gadus Morhua) During Early Life-Histories, Adrian Jordaan Dec 2002

The Effect Of Temperature On The Development, Growth And Survival Of Atlantic Cod (Gadus Morhua) During Early Life-Histories, Adrian Jordaan

Electronic Theses and Dissertations

For poikilothennic animals, and in particular those that inhabit aquatic habitats, temperature has a significant effect on all life processes. The purpose of this research was to investigate the contribution of temperature on embryonic development and survival and its effect on vital rates. Of particular interest was what aspect(s) of egg and larval life-histories are most affected by temperature and what consequence temperature effects may have on cumulative mortality. Three batches of Atlantic cod (Gadus morhua) eggs were acquired from a Newfoundland source of adult broodstock held at 4555°C. The eggs were divided andacclimated to four constant temperature regimes at …

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Evaluation Of Three Potential Methods For Preventing The Spread Of The Salmon Louse, Lepeophtheirus Salmonis (Kreyer, 1837), Micheal Pietrak Dec 2002

Evaluation Of Three Potential Methods For Preventing The Spread Of The Salmon Louse, Lepeophtheirus Salmonis (Kreyer, 1837), Micheal Pietrak

Electronic Theses and Dissertations

Lepeophtheirus salmonis or salmon lice infections are one of the most prevalent parasitic infections in the salmon aquaculture industry. Salmon lice cause an estimated loss of 3% of the production of Maine's salmon industry annually. Within the State of Maine only a portion of the farm sites experience salmon lice infections on an annual basis, while some sites have never had infections of Lepeophtheirus salmonis. Because of the potential impact that salmon lice infections could mean to those areas that to date have been fiee of L. salmonis infections, there has been concern both on the part of the State …

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A New Apex Predator In The Gulf Of Maine? Large, Mobile Crabs (Cancer Borealis) Control Benthic Community Structure, Amanda V. Leland Dec 2002

A New Apex Predator In The Gulf Of Maine? Large, Mobile Crabs (Cancer Borealis) Control Benthic Community Structure, Amanda V. Leland

Electronic Theses and Dissertations

Apex predators can control community structure by preying on strongly interacting species at lower trophic levels. Fishing of apex predators in the marine realm often results in herbivore dominated systems. In the Gulf of Maine, coastal subtidal communities became dominated by grazing green sea urchins (Strongylocentrotus droehachiensis) following the extirpation of large, predatory groundfish from coastal zones. Subsequent depletion of sea urchins since the late 1980s functionally eliminated this dominant herbivore from vast regions. Sea urchin recruitment is low or nonexistent in communities dominated by fleshy algae that have developed since the decline of sea urchin populations. We hypothesized that …

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Modeling The Role Of No-Take Marine Reserves In Fisheries Management, Deidre F. Gilbert Dec 2002

Modeling The Role Of No-Take Marine Reserves In Fisheries Management, Deidre F. Gilbert

Electronic Theses and Dissertations

In recent years there has been increasing interest in the potential of no-take marine reserves to benefit fisheries management. Scientific reviews have shown that reserves often lead to substantial increases in the density, biomass, size and diversity of marine fishes inside their boundaries. However, little empirical work has been done to determine the effect of reserves on the fisheries outside their boundaries, such as potential changes in yield, size of fleet, or variability in catch. In order to explore the interaction between the biological growth and dispersion processes of the harvested stock and the changing economic incentives of harvesters created …

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Biogeochemical Fate Of Sediment-Associated Pah: Effect Of Animal Processing, Anders Michael Bernth Giessing Dec 2002

Biogeochemical Fate Of Sediment-Associated Pah: Effect Of Animal Processing, Anders Michael Bernth Giessing

Electronic Theses and Dissertations

Biotransformation and fate of polycyclic aromatic hydrocarbons (PAHs) in marine invertebrates and sediment have been studied. Invertebrates can accumulate and metabolize sediment-associated PAHs to polar and aqueous PAH-derived compounds. The objectives of this study are to identify metabolites of PAHs in species of depositfeeding polychaetes and to examine biogeochemical fate and microbial degradation of the identified metabolites. Two metabolites, 1-hydroxypyrene and 1-hydroxypyrene glucuronide, were identified as the primary phase I and phase II metabolites of the tetracyclic PAH pyrene in Nereis diversicolor. Identification was performed using high pressure liquid chromatography with diode array and fluorescence detection (HPLC/DAD/F) and an ion-trap …

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Satellite-Measured Chlorophyll Variability Within The Upwelling Zone Near Heceta Bank, Oregon, Jennifer Bosch Dec 2002

Satellite-Measured Chlorophyll Variability Within The Upwelling Zone Near Heceta Bank, Oregon, Jennifer Bosch

Electronic Theses and Dissertations

Heceta Bank, a unique shallow bank on the southern Oregon shelf, is located within the California Current upwelling system. Four years (1998-2001) of 1-km resolution SeaWiFS ocean color satellite data of the Oregon coast are used to provide the first systematic description, and quantification of seasonal and interannual surface chlorophyll variability in the Heceta Bank region of coastal Oregon. The variability over the bank is examined with respect to wind forcing and surface temperature, and compared to the variability observed in topographically simpler shelf regions north and south of the bank. A seasonal cycle with lowest concentrations in the fall …

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Systematics Of The Cumacea (Crustacea), Pilar A. Haye Dec 2002

Systematics Of The Cumacea (Crustacea), Pilar A. Haye

Electronic Theses and Dissertations

Cumaceans are small benthic crustaceans. They have a marine cosmopolitan distribution with diversity increasing with depth. There are approximately 1,400 described species of cumaceans. Despite the fact that they offer a good model for the study of morphological evolution and biogeography, the studies on the Order Cumacea are almost restricted to work at the alpha taxonomy level. This thesis contributes to the systematics of Cumacea. The phylogenetic relationships within the Cumacea were studied using newly obtained partial amino acid sequences from the mitochondria1 gene Cytochrome Oxidase I. Among other findings, phylogenetic analyses revealed that the families Bodotriidae, Leuconidae, and Nannastacidae, …

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A 700-Year Record Of Atmospheric Circulation Developed From The Law Dome Ice Core, East Antarctica, Joseph M. Souney Jr, Paul A. Mayewski, Ian D. Goodwin, David Meeker, Vin Morgan, Mark Aj Curran, Tas D. Van Ommen, Anne S. Palmer Nov 2002

A 700-Year Record Of Atmospheric Circulation Developed From The Law Dome Ice Core, East Antarctica, Joseph M. Souney Jr, Paul A. Mayewski, Ian D. Goodwin, David Meeker, Vin Morgan, Mark Aj Curran, Tas D. Van Ommen, Anne S. Palmer

Earth Systems Research Center

A 700-year, high-resolution, multivariate ice core record from Dome Summit South (DSS) (66°46′S, 112°48′E; 1370 m), Law Dome, is used to investigate sea level pressure (SLP) variability in the region of East Antarctica. Empirical orthogonal function (EOF) analysis reveals that the first EOF (LDEOF1) of the combined glaciochemical, oxygen isotope ratio, and accumulation rate record from DSS represents most of the variability in sea salt seen in the record. LDEOF1 is positively correlated (at least 95% confidence level) to instrumental June mean SLP across most of East Antarctica. Over the last 700 years, LDEOF1 levels at Law Dome were the …

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Nitrogen Loading Into An Urban Estuary: Lake Pontchartrain (Louisiana, U.S.A.), R. Eugene Turner, Q. Dortch, Dubravko Justic, Erick M. Swenson Nov 2002

Nitrogen Loading Into An Urban Estuary: Lake Pontchartrain (Louisiana, U.S.A.), R. Eugene Turner, Q. Dortch, Dubravko Justic, Erick M. Swenson

Faculty Publications

We constructed a nitrogen loading budget for the Lake Pontchartrain watershed located north of New Orleans, Louisiana (U.S.A.). Water quality measurements, discharge estimates, and literature values were used to establish the annual and seasonal variations in loading rates for total nitrogen and nitrate. The relatively stable annual loadings (million kg N) are about 10× that of the pre-settlement nitrogen loading, and come from atmosphere (1.3), the watershed (7.8), pumped urban runoff from New Orleans (1.0), and leakage through the Bonnet Carré flood control structure (0.5–0.9). Relatively minor additional amounts come from nitrogen fixation in the Lake. Occasional openings of the …

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Measurements Of Pernitric Acid At The South Pole During Iscat 2000, D Slusher, L Gregory Huey, D Tanner, G Chen, D D. Davis, Martin Buhr, J Nowak, Fred Eisele, E Kosciuch, R L. Mauldin, Barry Lefer, R E. Shetter, Jack E. Dibb Nov 2002

Measurements Of Pernitric Acid At The South Pole During Iscat 2000, D Slusher, L Gregory Huey, D Tanner, G Chen, D D. Davis, Martin Buhr, J Nowak, Fred Eisele, E Kosciuch, R L. Mauldin, Barry Lefer, R E. Shetter, Jack E. Dibb

Earth Sciences

The first measurements of pernitric acid at the South Pole were performed during the second Investigation of Sulfur Chemistry in the Antarctic Troposphere (ISCAT 2000). Observed HO2NO2 concentrations averaged 25 pptv. Simple steady-state calculations constrained by measurements show that the lifetime of pernitric acid was largely controlled by dry deposition, with thermal decomposition becoming increasingly important at warmer temperatures. We determined that the pernitric acid equilibrium constant is less uncertain than indicated in the literature. One consequence of pernitric acid deposition to the snow surface is that it is an important sink for both NOx and HOx. Another is that …

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An Observation Of A Fast External Atmospheric Acoustic-Gravity Wave, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., R. J. Rudy, A. Z. Liu Oct 2002

An Observation Of A Fast External Atmospheric Acoustic-Gravity Wave, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., R. J. Rudy, A. Z. Liu

Publications

In November 1999 a new near-IR airglow imaging system was deployed at the Starfire Optical Range outside of Albuquerque, New Mexico. This system allowed wide angle images of the airglow to be collected, with high signal to noise, every 3 seconds with a one second integration time. At approximately 1000 UT on November 17, 1999, a fast wavelike disturbance was seen propagating through the OH Meinel airglow layer. This wave had an observed period of ≈215 seconds, an observed phase velocity of ≈160 m/s and a horizontal wavelength of ≈35 km. This phase velocity is among the fastest yet reported …

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Further Investigations Of A Mesospheric Inversion Layer Observed In The Aloha-93 Campaign, Tai-Yin Huang, Michael P. Hickey Ph.D., Tai-Fu Tuan Oct 2002

Further Investigations Of A Mesospheric Inversion Layer Observed In The Aloha-93 Campaign, Tai-Yin Huang, Michael P. Hickey Ph.D., Tai-Fu Tuan

Publications

Temperature and wind data obtained from a Na wind/temperature lidar operated by the University of Illinois group during the Airborne Lidar and Observations of the Hawaiian Airglow (ALOHA-93) Campaign, previously analyzed by Huang et al. [1998] using an isothermal Brunt-Va¨isa¨la¨ frequency, have been reexamined to include temperature gradients in the calculation of the Richardson number. In the previous analysis using the isothermal Brunt-Va¨isa¨la¨ frequency the existence of convective instability could not be assessed. New analysis shows that the nonisothermal Richardson number preserves some features found previously, with some striking differences noticable at times between 0900 and 1030 UT. The nonisothermal …

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Sensor-Assisted Video Mapping Of The Seafloor, Yuri Rzhanov, Lloyd C. Huff, Randy G. Cutter Jr., Larry A. Mayer Oct 2002

Sensor-Assisted Video Mapping Of The Seafloor, Yuri Rzhanov, Lloyd C. Huff, Randy G. Cutter Jr., Larry A. Mayer

Center for Coastal and Ocean Mapping

In recent years video surveys have become an increasingly important ground-truthing of acousticseafloor characterization and benthic habitat mapping studies. However, the ground-truthing and detailed characterization provided by video are still typically done using sparse sample imagery supplemented by physical samples. Combining single video frames in a seamless mosaic can provide a tool by which imagery has significant areal coverage, while at the same time showing small fauna and biological features at mm resolution. The generation of such a mosaic is a challenging task due to height variations of the imaged terrain and decimeter scale knowledge of camera position. This paper …

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Chromium Tolerant Microbial Communities From The Chesapeake Bay Watershed, Kristine L. Lowe, Ruth E. Fliflet, Tony Ly, Brenda J. Little, Joanne Jones-Meehan Oct 2002

Chromium Tolerant Microbial Communities From The Chesapeake Bay Watershed, Kristine L. Lowe, Ruth E. Fliflet, Tony Ly, Brenda J. Little, Joanne Jones-Meehan

Virginia Journal of Science

Chromium tolerant bacteria were enumerated from portions of the Chesapeake Bay watershed and examined for their potential to reduce Cr(VI). Water and sediment samples were collected from various locations in Baltimore Harbor and Bear Creek, as well as Sandy Point State Park in Maryland and the Anacostia River in Washington, DC. Samples were spread onto agar plates with CrO42- (5 ppm) as the sole terminal electron acceptor. Plates were incubated anaerobically and colony forming units (CFU) enumerated. CFU arising on minimal-CrO42- medium ranged from 103-104 mL-1 or g-1 and community estimates …

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Fall 2002, Nsu Oceanographic Center Oct 2002

Fall 2002, Nsu Oceanographic Center

Currents

No abstract provided.

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Near Bottom Sediment Characterization Offshore Sw San Clemente Island, Daniel D. Sternlicht, Christian De Moustier Oct 2002

Near Bottom Sediment Characterization Offshore Sw San Clemente Island, Daniel D. Sternlicht, Christian De Moustier

Center for Coastal and Ocean Mapping

Normal incidence, 23.5 kHz seafloor acoustic backscatter data and bottom video were measured with the Deep Tow instrument package of the Scripps Institution of Oceanography in 100 meter water depth south of San Clemente Island, CA. The collected data were processed using an echo envelopesediment characterization method, to derive geoacoustic parameters such as particle mean grain size and the strength of the power law characterizing the roughness energy density spectrum of thesediment-water interface. Two regions, sand and silt, were selected based on available ground truth, perceived along-track sediment homogeneity, data quality and tow fish stability. Distinction between sand and fine …

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A Prototype 1:6 Million Map, Martin Jakobsson Oct 2002

A Prototype 1:6 Million Map, Martin Jakobsson

Center for Coastal and Ocean Mapping

No abstract provided.

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3-D Visualization Of Ibcao, Martin Jakobsson, Ron Macnab Oct 2002

3-D Visualization Of Ibcao, Martin Jakobsson, Ron Macnab

Center for Coastal and Ocean Mapping

No abstract provided.

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Characteristics Of Shark Bycatch Observed On Pelagic Longlines Off The Southeastern United States, 1992-2000, Lawrence R. Beerkircher, Enric Cortes, Mahmood S. Shivji Oct 2002

Characteristics Of Shark Bycatch Observed On Pelagic Longlines Off The Southeastern United States, 1992-2000, Lawrence R. Beerkircher, Enric Cortes, Mahmood S. Shivji

Marine & Environmental Sciences Faculty Articles

Data collected by fisheries observers aboard U.S. pelagic longline vessels were examined to quantify and describe elasmobranch bycatch off the southeastern U.S. coast (lat. 22°-35°N, long. 71°-82°W). From 1992 to 2000, 961 individual longline hauls were observed, during which 4,612 elasmobranchs (15% of the total catch) were documented. Of the 22 elasmobranch species observed, silky sharks, Carcharhinus falciformis, were numerically dominant (31.4% of the elasmobranch catch). The catch status of the animals (alive or dead) when the gear was retrieved varied widely depending on the species, with high mortalities seen for the commonly caught silky and night, C. signatus …

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