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Articles 181 - 210 of 2497

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Instability Of A Tidal Mixing Front In The Presence Of Realistic Tides And Mixing, K. H. Brink Jan 2013

Instability Of A Tidal Mixing Front In The Presence Of Realistic Tides And Mixing, K. H. Brink

Journal of Marine Research

Instability and lateral eddy fluxes associated with a tidal mixing front are studied using idealized primitive equation numerical model runs. The front itself develops as a result of turbulence associated with imposed tidal currents over a sloping bottom. Thus, the model includes realistic levels of turbulence and time-dependence in the base-state conditions. In all of the 21 configurations considered, the front is unstable to fluctuations that usually draw energy primarily from the potential energy pool. Scalings are developed to parameterize a) the location of the tidal mixing front; b) the eddy kinetic energy; and c) the lateral eddy coefficients. In …

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Nutrient Supply In The Southern East China Sea After Typhoon Morakot, Chin-Chang Hung, Chih-Ching Chung, Gwo-Ching Gong, Sen Jan, Yaling Tsai, Kuo-Shu Chen, Wen Chen Chou, Ming-An Lee, Yi Chang, Meng-Hsien Chen, Wen-Rong Yang, Chiung-Jung Tseng, Glen Gawarkiewicz Jan 2013

Nutrient Supply In The Southern East China Sea After Typhoon Morakot, Chin-Chang Hung, Chih-Ching Chung, Gwo-Ching Gong, Sen Jan, Yaling Tsai, Kuo-Shu Chen, Wen Chen Chou, Ming-An Lee, Yi Chang, Meng-Hsien Chen, Wen-Rong Yang, Chiung-Jung Tseng, Glen Gawarkiewicz

Journal of Marine Research

Recent studies show that typhoons have profound effects on phytoplankton assemblages along their tracks, but it is difficult to quantitatively estimate nutrient supply after a typhoon's passage due to a lack of nutrient information before and after the arrival of a typhoon. During the passage of Typhoon Morakot (July 22 to Aug. 26, 2009), we conducted pre- and post-typhoon field cruises to study nutrient supply in the Southern East China Sea (SECS). The results showed nitrate and phosphate supplies to the water column in the SECS after the typhoon's passage were 5.6 × 1011 g-N/day and 7.8 × 10 …

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Ecosystem-Scale Rainfall Manipulation In A Piñon-Juniper Forest At The Sevilleta National Wildlife Refuge, New Mexico: Volumetric Water Content (Vwc) At 5 Cm Depth Data (2006- ), William Pockman, Nathan Mcdowell Jan 2013

Ecosystem-Scale Rainfall Manipulation In A Piñon-Juniper Forest At The Sevilleta National Wildlife Refuge, New Mexico: Volumetric Water Content (Vwc) At 5 Cm Depth Data (2006- ), William Pockman, Nathan Mcdowell

Sevilleta LTER Program Data

Climate models predict that water limited regions around the world will become drier and warmer in the near future, including southwestern North America. We developed a large-scale experimental system that allows testing of the ecosystem impacts of precipitation changes. Four treatments were applied to 1600 m2 plots (40 m × 40 m), each with three replicates in a piñon pine (Pinus edulis) and juniper (Juniper monosperma) ecosystem. These species have extensive root systems, requiring large-scale manipulation to effectively alter soil water availability. Treatments consisted of: 1) irrigation plots that receive supplemental water additions, 2) drought plots that receive 55% of …

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Transition In The Fractal Geometry Of Arctic Melt Ponds, C. Hohenegger, B. Alali, K. R. Steffen, D. K. Perovich, K. M. Golden Oct 2012

Transition In The Fractal Geometry Of Arctic Melt Ponds, C. Hohenegger, B. Alali, K. R. Steffen, D. K. Perovich, K. M. Golden

Dartmouth Scholarship

During the Arctic melt season, the sea ice surface undergoes a remarkable transformation from vast expanses of snow covered ice to complex mosaics of ice and melt ponds. Sea ice albedo, a key parameter in climate modeling, is determined by the complex evolution of melt pond configurations. In fact, ice–albedo feedback has played a major role in the recent declines of the summer Arctic sea ice pack. However, understanding melt pond evolution remains a significant challenge to improving climate projections. By analyzing area–perimeter data from hundreds of thousands of melt ponds, we find here an unexpected separation of scales, where …

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A Climatological Analysis Of The Warm-Season Wind Regimes Of The Beaufort/Chukchi Seas Coasts, William J. Baule Jul 2012

A Climatological Analysis Of The Warm-Season Wind Regimes Of The Beaufort/Chukchi Seas Coasts, William J. Baule

School of Natural Resources: Dissertations, Theses, and Student Research

Climate records for wind speed, wind direction, and temperature are analyzed for the period from 1979-2009 for the Beaufort/Chukchi Seas region of the Arctic. Wind records have historically been subject to far fewer analyses than other meteorological variables, such as temperature or precipitation. This is particularly true for data sparse regions. Data were collected for a large area in the Beaufort/Chukchi Seas region, which includes portions of Russia, the United States, and Canada. Data from 250 stations were collected from a variety of networks throughout the region and uniformly quality controlled. Eight long-term stations were identified for data completeness and …

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Winter Precipitation Depths Across The North Slope Of Alaska Simulated From The Weather Research And Forcasting Model And Snowtran-3d, Sarah Jean Byam Apr 2012

Winter Precipitation Depths Across The North Slope Of Alaska Simulated From The Weather Research And Forcasting Model And Snowtran-3d, Sarah Jean Byam

Engineering

Accurately predicting snow distribution and blowing snow conditions in the Arctic is critical to the design of ice road construction and maintenance as well as for predicting water supplies and runoff during snowmelt, estimating the cost of snow removal, and forecasting tundra travel conditions. A current atmospheric model used by both the operational weather prediction and research communities is the Weather Research and Forecasting model. However, the built-in snow schemes in the model neglect redistribution of snow via wind, one of the key processes in snow pack evolution. This study will involve three parts: (1) diagnostic of the differences in …

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The Air-Sea Transformation And Residual Overturning Circulation Within The Nordic Seas, Pål Erik Isachsen, Ole Anders Nøst Jan 2012

The Air-Sea Transformation And Residual Overturning Circulation Within The Nordic Seas, Pål Erik Isachsen, Ole Anders Nøst

Journal of Marine Research

The residual diapycnal overturning circulation through interior regions of the Nordic Seas is diagnosed. The mean flow is estimated from Ekman dynamics and from the thermal wind relation with reference level velocities deduced from observations and from simplified theory. Eddy-induced transport is estimated from a GM-type parameterization which includes top and bottom boundary layers. The contributions from the Eulerian mean and eddy-induced transport are then compared to the annual-mean air – sea density transformation over the Nordic Seas. The calculations suggest that the mean flow overturning may explain up to 25% of the observed air – sea transformation in the …

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The Impact Of Ambient Stratification On Freshwater Transport In A River Plume, Yan Jia, Alexander Yankovsky Jan 2012

The Impact Of Ambient Stratification On Freshwater Transport In A River Plume, Yan Jia, Alexander Yankovsky

Journal of Marine Research

The influence of ambient stratification on the river plume dynamics is studied using the Regional Ocean Modeling System (ROMS). The shelf flow is thermally stratified and retains a 15-m deep upper mixed layer. A buoyant inflow into the model domain is systematically varied so that both surface-advected and bottom-advected buoyant plumes are formed. The resulting buoyant plumes are compared with the corresponding numerical solutions when the ambient shelf flow is not stratified. Surface-advected plumes spread on top of the thermocline and are not affected by the ambient stratification. Bottom-advected plumes on the other hand interact with the ambient stratification by …

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Deep Circulation Within The Argentine Basin, Joseph L. Reid Jan 2012

Deep Circulation Within The Argentine Basin, Joseph L. Reid

Journal of Marine Research

The total transport in the South Atlantic Ocean (Fig. 1) consists of an anticyclonic gyre that reaches from the equator to about 50°S, and south of 40°S two cyclonic turns from the Circumpolar Current and Weddell Sea, west and east of the anticyclonic gyre. This figure has been changed very slightly between 40°S and 50°S from the figure shown in Reid (1994)...

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Long-Term Patterns Of An Estuarine Pathogen Along A Salinity Gradient, David Bushek, Susan E. Ford, Iris Burt Jan 2012

Long-Term Patterns Of An Estuarine Pathogen Along A Salinity Gradient, David Bushek, Susan E. Ford, Iris Burt

Journal of Marine Research

Parasitic, disease-causing pathogens can exert strong control over marine populations yet few long-term studies exist that describe these relationships. Understanding the connections to long-term large-scale processes relative to local short-term processes should facilitate better planning for disease impacts in the management of marine resources. We describe a 21-yr dataset of dermo disease (Perkinsus marinus) in eastern oysters (Crassostrea virginica) in Delaware Bay, USA. Analyses indicated (1) a strong positive association between disease and mortality that was non-linear and defined by thresholds, (2) a clear spatial gradient of increasing disease and mortality with increasing salinity, (3) an …

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An Introduction To Ecology Of Infectious Diseases – Oysters And Estuaries, Eileen E. Hofmann, Susan E. Ford Jan 2012

An Introduction To Ecology Of Infectious Diseases – Oysters And Estuaries, Eileen E. Hofmann, Susan E. Ford

Journal of Marine Research

Infectious diseases are recognized as an important factor regulating marine ecosystems (Harvell et al., 1999, 2002, 2004; Porter et al., 2001; McCallum et al., 2004; Ward and Lafferty, 2004; Stewart et al., 2008; Bienfang et al., 2011). Many of the organisms affected by marine diseases have important ecological roles in estuarine and coastal environments and some are also commercially important. Outbreaks of infectious diseases in these environments, referred to as epizootics, can produce significant population declines and extinctions, both of which threaten biodiversity, food web interactions, and ecosystem productivity (Harvell et al., 2002, 2004)...

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Can Oysters Crassostrea Virginica Develop Resistance To Dermo Disease In The Field: The Impediment Posed By Climate Cycles, Eric N. Powell, John M. Klinck, Ximing Guo, Eileen E. Hofmann, Susan E. Ford, David Bushek Jan 2012

Can Oysters Crassostrea Virginica Develop Resistance To Dermo Disease In The Field: The Impediment Posed By Climate Cycles, Eric N. Powell, John M. Klinck, Ximing Guo, Eileen E. Hofmann, Susan E. Ford, David Bushek

Journal of Marine Research

Populations of eastern oysters, Crassostrea virginica, are commonly limited by mortality from dermo disease. Little development of resistance to Perkinsus marinus, the dermo pathogen, has occurred, despite the high mortality rates and frequency of epizootics. Can the tendency of the parasite to exhibit cyclic epizootics limit the oyster's response to the disease despite the presence of alleles apparently conferring disease resistance? We utilize a gene-based population dynamics model to simulate the development of disease resistance in Crassostrea virginica populations exposed to cyclic mortality encompassing periodicities expected of dermo disease over the geographic range at which epizootics have been …

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Circulation And Water Properties And Their Relationship To The Oyster Disease Msx In Delaware Bay, Zhiren Wang, Dale B. Haidvogel, David Bushek, Susan E. Ford, Eileen E. Hofmann, Eric N. Powell, John Wilkin Jan 2012

Circulation And Water Properties And Their Relationship To The Oyster Disease Msx In Delaware Bay, Zhiren Wang, Dale B. Haidvogel, David Bushek, Susan E. Ford, Eileen E. Hofmann, Eric N. Powell, John Wilkin

Journal of Marine Research

We apply a high-resolution hydro-dynamical model to investigate the role of physical factors influencing infection prevalence of Haplosporidium nelsoni, causative agent of MSX disease in the eastern oyster (Crassostrea virginica), in Delaware Bay, USA. Validation studies conducted for the years 2000 and 2010–2011 confirm that the model, based upon the Regional Ocean Modeling System, has significant skill in the recovery of observed water level, temperature, salinity, and velocity. Multi-year simulations are performed for periods representing temporal and spatial variations in H. nelsoni infection prevalence (1974–76, 1979–81, 1984–86, 1990–92, and 2006–09) to assess the degree to which the …

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Spatial And Temporal Variability Of Disease Refuges In An Estuary: Implications For The Development Of Resistance, Susan E. Ford, Emily Scarpa, David Bushek Jan 2012

Spatial And Temporal Variability Of Disease Refuges In An Estuary: Implications For The Development Of Resistance, Susan E. Ford, Emily Scarpa, David Bushek

Journal of Marine Research

Although the concept of genetic refuge has long been employed in ecological and paleoecological context, it has only rarely been used to identify regions where organisms are protected from diseases that affect the rest of a population. The refuges harbor individuals that have not been exposed to selective mortality and remain susceptible to the disease. They represent a reservoir of susceptibility alleles that can mix with those from resistant survivors of disease and can retard the development of resistance in the population as a whole. Two water-borne protistan parasites affect oysters along the east coast of the United States: Haplosporidium …

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Primary And New Production In The Thermocline Ridge Region Of The Southern Indian Ocean During The Summer Monsoon, Naveen Gandhi, R. Ramesh, S. Prakash, Sharon Noronha, N. Anilkumar Jan 2012

Primary And New Production In The Thermocline Ridge Region Of The Southern Indian Ocean During The Summer Monsoon, Naveen Gandhi, R. Ramesh, S. Prakash, Sharon Noronha, N. Anilkumar

Journal of Marine Research

New and primary production, measured using 15N and 13C tracers, integrated over the euphotic zone (mostly upper 80–100 m) varied from 7.5 to 14.1 mmol N m–2d–1(average 10.8 mmol N m–2d–1) and 2.7 to 17.7 mmol C m–2d–1 (average 11.3 mmol C m–2d–1), respectively, in the tropical India Ocean (TIO). Shoaling of thermocline in the thermocline ridge located in the tropical Indian Ocean (TR) influences new and total productivity by supplying nutrients to the upper layers. At the same time, N-limited conditions prevail …

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Geostrophic Ocean Currents And Freshwater Fluxes Across The Canadian Polar Shelf Via Nares Strait, Berit Rabe, Helen L. Johnson, Andreas Münchow, Humfrey Melling Jan 2012

Geostrophic Ocean Currents And Freshwater Fluxes Across The Canadian Polar Shelf Via Nares Strait, Berit Rabe, Helen L. Johnson, Andreas Münchow, Humfrey Melling

Journal of Marine Research

This study discusses geostrophic ocean currents and fluxes through Nares Strait, one of the major straits connecting the Arctic Ocean to the North Atlantic across the Canadian polar shelf. Between 2003 and 2006, instruments were installed on subsea moorings to measure conductivity, temperature, pressure and velocity at high temporal and spatial resolution across the 400-m-deep strait. Here we present estimates of the variable volume and liquid freshwater fluxes, derived by geostrophic calculation, through the fraction of the cross section measured by the array. The array of conductivity-temperature recorders spanned 30 km of a 38-km-wide section between 30- and 200-m depth. …

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Solar Warming Of Near-Bottom Water Over A Fringing Reef, Judith R. Wells, Jonathan P. Fram, Geno Pawlak Jan 2012

Solar Warming Of Near-Bottom Water Over A Fringing Reef, Judith R. Wells, Jonathan P. Fram, Geno Pawlak

Journal of Marine Research

The Kilo Nalu Observatory is located on the foreslope of a fringing reef on the south shore of Oahu, Hawaii. A cabled node at 12-m depth has enabled continuous real-time temperature observations from a thermistor chain extending from 1 to 7 m above bottom. Data from a 27-month deployment in 2007–2009 reveal repeated instances of subsurface temperature inversions. The usual diurnal pattern shows increases in temperature throughout the water column after sunrise, peaking in the early afternoon. Bottom waters typically warm faster than those at mid-depth, driving an inversion in the thermal profile. The onset and evolution of the inversions …

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Experimental Assessment Of Particle Mixing Fingerprints In The Deposit-Feeding Bivalve Abra Alba (Wood), Guillaume Bernard, Antoine Grémare, Olivier Maire, Pascal Lecroart, Filip J. R. Meysman, Aurélie Ciutat, Bruno Deflandre, Jean Claude Duchêne Jan 2012

Experimental Assessment Of Particle Mixing Fingerprints In The Deposit-Feeding Bivalve Abra Alba (Wood), Guillaume Bernard, Antoine Grémare, Olivier Maire, Pascal Lecroart, Filip J. R. Meysman, Aurélie Ciutat, Bruno Deflandre, Jean Claude Duchêne

Journal of Marine Research

Particle mixing induced by the deposit-feeding bivalve Abra alba was assessed using a new experimental approach allowing for the tracking of individual particle displacements. This approach combines the adaptation of existing image acquisition techniques with new image analysis software that tracks the position of individual particles. This led to measurements of particle mixing fingerprints, namely the frequency distributions of particle waiting times, and of the characteristics (i.e. direction and length) of their jumps. The validity of this new approach was assessed by comparing the so-measured frequency distributions of jump characteristics with the current qualitative knowledge regarding particle mixing in the …

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Eddy Viscosity And Diffusivity In The Modon-Sea Model, Timour Radko Jan 2012

Eddy Viscosity And Diffusivity In The Modon-Sea Model, Timour Radko

Journal of Marine Research

A deterministic model is developed to evaluate and explain the rate of dissipation of momentum in eddying oceanic flows. Theory is based on a classical conceptualization of mesoscale variability – Stern's modon-sea solution – which represents a closely packed array of steady compact dipolar vortices on the barotropic beta-plane. In our model, the periodic modon-sea pattern is subjected to a large-scale perturbation, weakly modulating the amplitude of the individual modons. The asymptotic multiscale analysis makes it possible to explicitly describe the interaction between the modon-sea eddies and the perturbing flow. This interaction results in a systematic weakening of the large-scale …

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Measuring Overturns With Gliders, S. A. Thorpe Jan 2012

Measuring Overturns With Gliders, S. A. Thorpe

Journal of Marine Research

The accuracy of the estimation of the vertical size of eddies in turbulent stratified shear flows in the ocean from measurements obtained by gliders is examined. It is assumed that gliders move along paths inclined at moderate angles to the horizontal. Comparison is made with measurements by probes falling or lowered vertically through billows resulting from Kelvin-Helmholtz (K-H) or Holmboe instability and through the statically unstable regions formed at early stages of convective breaking of internal waves. The probable errors involved in estimating the overturn scale of a K-H billow along the track of a glider are greatest when the …

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Glider Measurements Of Overturning In A Kelvin-Helmholtz Billow Train, W. D. Smyth, S. A. Thorpe Jan 2012

Glider Measurements Of Overturning In A Kelvin-Helmholtz Billow Train, W. D. Smyth, S. A. Thorpe

Journal of Marine Research

The prospects for glider-based measurement of turbulence statistics are assessed using direct numerical simulation data representing breaking Kelvin-Helmholtz (KH) billows in a stratified, parallel shear flow. Transects tilted upstream against the shear tend to produce overestimates of overturning; those tilted with the shear produce underestimates. Low-angle transects can produce illusory overturning as the braid between the KH billows is crossed. Statistical features of the bias in displacement scales are related to geometrical aspects of KH billows. Results are interpreted in the context of a hypothetical effort to characterize overturning in a strongly sheared current (e.g. the Equatorial Undercurrent) using nonvertical …

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Cross-Shelf Mixing And Mid-Shelf Front Dynamics In The Mid-Atlantic Bight Evaluated Using The Radium Quartet, Scott L. Stachelhaus, S. Bradley Moran, David S. Ullman, Roger P. Kelly Jan 2012

Cross-Shelf Mixing And Mid-Shelf Front Dynamics In The Mid-Atlantic Bight Evaluated Using The Radium Quartet, Scott L. Stachelhaus, S. Bradley Moran, David S. Ullman, Roger P. Kelly

Journal of Marine Research

Mid-shelf fronts (MSFs) are thought to be ubiquitous in shelf areas. However, their dynamical role in cross-shelf mixing has yet to be fully characterized. In January, February, and April of 2007, radium isotopes (223Ra, t1/2 = 11 d; 224Ra, t1/2 = 3.7 d; 226Ra, t1/2 = 1600 yr; 228Ra, t1/2 = 5.7 yr) were measured along a transect in the Mid-Atlantic Bight to constrain mixing rates at and around a MSF. Cross-shelf eddy diffusivities (Kx) were determined from 223Ra and 224Ra distributions using a variable-depth model. Two key assumptions …

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Development Of Resistance To An Introduced Marine Pathogen By A Native Host, Susan E. Ford, David Bushek Jan 2012

Development Of Resistance To An Introduced Marine Pathogen By A Native Host, Susan E. Ford, David Bushek

Journal of Marine Research

In 1957–1959, the introduced protistan parasite, Haplosporidium nelsoni, killed 90–95% of the oysters (Crassostrea virginica) in lower Delaware Bay and about half of those in the upper bay. Shortly thereafter, H. nelsoni-caused mortality in the wild population of the lower bay declined, approximating that of first-generation selectively bred oysters. For nearly three decades thereafter no further change in survival of the wild population was evident, although steady improvement was achieved by continued selective breeding. Survival of the wild population is thought to have plateaued because the great majority of oysters inhabited the upper bay where they …

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Effective Population Sizes Of Eastern Oyster Crassostrea Virginica (Gmelin) Populations In Delaware Bay, Usa, Yan He, Susan E. Ford, David Bushek, Eric N. Powell, Zhenmin Bao, Ximing Guo Jan 2012

Effective Population Sizes Of Eastern Oyster Crassostrea Virginica (Gmelin) Populations In Delaware Bay, Usa, Yan He, Susan E. Ford, David Bushek, Eric N. Powell, Zhenmin Bao, Ximing Guo

Journal of Marine Research

Effective population size (Ne) is an important concept in population genetics as it dictates the rate of genetic change caused by drift. Ne estimates for many marine populations are small relative to the census population size. Small Ne in a large population may indicate high reproductive variance or sweepstakes reproductive success (SRS). The eastern oyster (Crassostrea virginica) may be prone to SRS due to its high fecundity and high larval mortality. To examine if SRS occurs in the eastern oyster, we studied Ne and genetic variation of oyster populations in Delaware Bay. …

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Modeling The Dispersal Of Eastern Oyster (Crassostrea Virginica) Larvae In Delaware Bay, Diego A. Narváez, John M. Klinck, Eric N. Powell, Eileen E. Hofmann, John Wilkin, Dale B. Haidvogel Jan 2012

Modeling The Dispersal Of Eastern Oyster (Crassostrea Virginica) Larvae In Delaware Bay, Diego A. Narváez, John M. Klinck, Eric N. Powell, Eileen E. Hofmann, John Wilkin, Dale B. Haidvogel

Journal of Marine Research

The interactions of circulation and growth processes in determining the horizontal distribution of eastern oyster (Crassostrea virginica) larvae in the Delaware Bay estuary were investigated with a coupled circulation-individual-based larvae model that used environmental conditions from the spawning seasons (mid-June to mid-September) of 1984, 1985, 1986, 2000, and 2001. Particles, representing oyster larvae, were released at five-day intervals from areas in Delaware Bay that correspond to natural oyster reefs. The simulated larval development time was used to estimate potential larval success, determined by the percent of larvae that successfully reached settlement size (330 μm) within the planktonic larval …

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Reconciling Float-Based And Tracer-Based Estimates Of Lateral Diffusivities, Andreas Klocker, Raffaele Ferrari, Joseph H. Lacasce, Sophia T. Merrifield Jan 2012

Reconciling Float-Based And Tracer-Based Estimates Of Lateral Diffusivities, Andreas Klocker, Raffaele Ferrari, Joseph H. Lacasce, Sophia T. Merrifield

Journal of Marine Research

Lateral diffusivities are computed from synthetic particles and tracers advected by a velocity field derived from sea-surface height measurements from the South Pacific, in a region west of Drake Passage. Three different estimates are compared: (1) the tracer-based “effective diffusivity” of Nakamura (1996), (2) the growth of the second moment of a cloud of tracer and (3) the single- and two-particle Lagrangian diffusivities. The effective diffusivity measures the cross-stream component of eddy mixing, so this article focuses on the meridional diffusivities for the others, as the mean flow (the ACC) is zonally oriented in the region. After an initial transient …

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Intermittent Bioirrigation And Oxygen Dynamics In Permeable Sediments: An Experimental And Modeling Study Of Three Tellinid Bivalves, Nils Volkenborn, Christof Meile, Lubos Polerecky, Conrad A. Pilditch, Alf Norkko, Joanna Norkko, Judi E. Hewitt, Simon F. Thrush, David S. Wethey, Sarah A. Woodin Jan 2012

Intermittent Bioirrigation And Oxygen Dynamics In Permeable Sediments: An Experimental And Modeling Study Of Three Tellinid Bivalves, Nils Volkenborn, Christof Meile, Lubos Polerecky, Conrad A. Pilditch, Alf Norkko, Joanna Norkko, Judi E. Hewitt, Simon F. Thrush, David S. Wethey, Sarah A. Woodin

Journal of Marine Research

To explore the dynamic nature of geochemical conditions in bioirrigated marine permeable sediments, we studied the hydraulic activity of three tellinacean bivalve molluscs (the Pacific species Macoma nasuta and Macomona liliana, and the northern Atlantic and Pacific species Macoma balthica). We combined porewater pressure sensing, time-lapse photography and oxygen imaging to quantify the durations and frequencies of tellinid irrigation activity and the associated oxygen dynamics in the sediment. Porewater pressure records of all tellinids were dominated by intermittent porewater pressurization, induced by periodic water injection into the sediment through their excurrent siphons, which resulted in intermittent oxygen supply …

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Deep Circulation In The Eastern South Pacific Ocean, Vincent Faure, Kevin Speer Jan 2012

Deep Circulation In The Eastern South Pacific Ocean, Vincent Faure, Kevin Speer

Journal of Marine Research

We use an inverse method to compute the deep circulation in the eastern South Pacific Ocean, on isopycnal layers within the depth range of 1,000–3,000 m. The method gives probability density functions of the isopycnal and diapycnal velocities and diffusivities on a grid with a realistic eastern boundary, based on tracer fields. An oxygen consumption rate, assumed spatially constant, controls the solution effectiveness (minimum value of the model cost function) and the magnitude of the diffusivities. The isopycnal circulation is, by contrast, less dependent on the consumption rate. Direct deep float displacement data is used as a check on our …

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The Role Of Larval Dispersal In Metapopulation Gene Flow: Local Population Dynamics Matter, Daphne M. Munroe, John .. Klinck, Eileen E. Hofmann, Eric N. Powell Jan 2012

The Role Of Larval Dispersal In Metapopulation Gene Flow: Local Population Dynamics Matter, Daphne M. Munroe, John .. Klinck, Eileen E. Hofmann, Eric N. Powell

Journal of Marine Research

The degree of genetic connectivity among populations in a metapopulation has direct consequences for species evolution, development of disease resistance, and capacity of a metapopulation to adapt to climate change. This study used a metapopulation model that integrates population dynamics, dispersal, and genetics within an individual-based model framework to examine the mechanisms and dynamics of genetic connectivity within a metapopulation. The model was parameterized to simulate four populations of oysters (Crassostrea virginica) from Delaware Bay on the mid-Atlantic coast of the United States. Differences among the four populations include a strong spatial gradient in mortality, a spatial gradient …

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Oyster Food Supply In Delaware Bay: Estimation From A Hydrodynamic Model And Interaction With The Oyster Population, Eric N. Powell, Danielle A. Kreeger, Jason M. Morson, Dale B. Haidvogel, Zhiren Wang, Roger Thomas, Jennifer E. Gius Jan 2012

Oyster Food Supply In Delaware Bay: Estimation From A Hydrodynamic Model And Interaction With The Oyster Population, Eric N. Powell, Danielle A. Kreeger, Jason M. Morson, Dale B. Haidvogel, Zhiren Wang, Roger Thomas, Jennifer E. Gius

Journal of Marine Research

To evaluate oyster food supply, water samples were collected at fifteen sites in Delaware Bay nearmonthly in 2009 and 2010. Food was estimated as the sum of particulate protein, labile carbohydrate, and lipid. Delaware Bay shows a typical spring bloom, centered in March and April, with declining food supply thereafter into early fall, followed sporadically by a minor fall bloom. The geographic and temporal structure of food was more predictable in summer to early fall, and considerably less predictable in spring. Five variables each based on temperature and the spatial and temporal variability of temperature were significant contributors to a …

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