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Articles 121 - 150 of 157
Full-Text Articles in Life Sciences
Eutrophication-Induced Phosphorus Limitation In The Mississippi River Plume: Evidence From Fast Repetition Rate Fluorometry, Jb Sylvan, A Quigg, S Tozzi, Jw Ammerman
Eutrophication-Induced Phosphorus Limitation In The Mississippi River Plume: Evidence From Fast Repetition Rate Fluorometry, Jb Sylvan, A Quigg, S Tozzi, Jw Ammerman
VIMS Articles
We assessed nutrient limitation in the Mississippi River plurne and Louisiana continental shelf during the summer of 2002 (04-08 July). We measured nutrient concentrations, alkaline phosphatase (AP) activities, chlorophyll a (Chl a) concentrations, and four fast repetition rate fluorescence (FRRF) parameters: the maximum quantum yield of photochemistry in photosystem II (PSII), F-v:F-m; the functional absorption cross section for PSII, sigma(psII); the time for photosynthetic electron transport on the acceptor side of PSII, tau(Qa); and the connectivity factor, p, in 24-h-long nutrient addition bioassays near the Mississippi River delta. Low phosphorus (P) concentrations, elevated inorganic nitrogen-to-phosphorus ratios, high AP activities, and …
Phytoplankton Carbon Fixation Gene (Rubisco) Transcripts And Air-Sea Co2 Flux In The Mississippi River Plume, De John, Zha Wang, Xw Liu, Rh Byrne, Je Corredor, Da Bronk, Et Al.
Phytoplankton Carbon Fixation Gene (Rubisco) Transcripts And Air-Sea Co2 Flux In The Mississippi River Plume, De John, Zha Wang, Xw Liu, Rh Byrne, Je Corredor, Da Bronk, Et Al.
VIMS Articles
River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO2 drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO2 dynamics, we evaluated rbcL mRNA abundance using novel quantitative PCR assays, phytoplankton cell analyses, photophysiological parameters, and pCO2 in and around the Mississippi River plume (MRP) in the Gulf of Mexico. Lower salinity (30-32) stations were dominated by rbcL mRNA concentrations from heterokonts, such as diatoms and pelagophytes, which were at least an order of magnitude greater than haptophytes, a-Synechococcus or high-light Prochlorococcus. …
Susceptibility Of Salt Marshes To Nutrient Enrichment And Predator Removal, La Deegan, Jl Bowen, D Drake, Jw Fleeger, Carl T. Friedrichs, Et Al.
Susceptibility Of Salt Marshes To Nutrient Enrichment And Predator Removal, La Deegan, Jl Bowen, D Drake, Jw Fleeger, Carl T. Friedrichs, Et Al.
VIMS Articles
Salt marsh ecosystems have been considered not susceptible to nitrogen overloading because early studies suggested that salt marshes adsorbed excess nutrients in plant growth. However, the possible effect of nutrient loading on species composition, and the combined effects of nutrients and altered species composition on structure and function, was largely ignored. Failure to understand interactions between nutrient loading and species composition may lead to severe underestimates of the impacts of stresses. We altered whole salt marsh ecosystems (similar to 60 000 m(2)/treatment) by addition of nutrients in flooding waters and by reduction of a key predatory fish, the mummichog. We …
Calculating Shoreline Erosion Potential Using Nearshore Stratigraphy And Sediment Volume: Outer Banks, North Carolina, Jennifer L. Miselis, Jesse E. Mcninch
Calculating Shoreline Erosion Potential Using Nearshore Stratigraphy And Sediment Volume: Outer Banks, North Carolina, Jennifer L. Miselis, Jesse E. Mcninch
VIMS Articles
[1] Despite the acknowledged influence of coastal geological framework on the behavior of beaches and barrier islands and a wealth of geological and bathymetric observations from the inner shelf, quantitatively connecting those observations to shoreline behavior has been difficult. Nearshore geologic and morphologic variability described by recent research is not well represented by conventional geologic parameters, such as mean grain size and shoreface slope, used in most shoreline change models. We propose that total nearshore sediment volume, as calculated to a continuous seismic reflection surface, provides a flexible and robust metric for use in the prediction of shoreline change. This …
Plankton Development And Trophic Transfer In Seawater Enclosures With Nutrients And Phaeocystis Pouchetii Added, J. C. Nejstgaard, M. E. Frischer, P. G. Verity, J. T. Anderson, A. Jacobson, Mj Zirbel, A. Larsen, J. Mrtinez-Martinez, Af. Sazhin, T. Walters, Da Bronk, Sj. Whipple, Sr. Borrett, Bc Patten, Jd Long
Plankton Development And Trophic Transfer In Seawater Enclosures With Nutrients And Phaeocystis Pouchetii Added, J. C. Nejstgaard, M. E. Frischer, P. G. Verity, J. T. Anderson, A. Jacobson, Mj Zirbel, A. Larsen, J. Mrtinez-Martinez, Af. Sazhin, T. Walters, Da Bronk, Sj. Whipple, Sr. Borrett, Bc Patten, Jd Long
VIMS Articles
In high latitude planktonic ecosystems where the prymnesiophyte alga Phaeocystis pouchetii is often the dominant primary producer, its importance in structuring planktonic food webs is well known. In this study we investigated how the base of the planktonic food web responds to a P. pouchetii colony bloom in controlled mesocosm systems with natural water enclosed in situ in a West Norwegian fjord. Similar large (11 m(3)) mesocosm studies were conducted in 2 successive years and the dynamics of various components of the planktonic food web from viruses to mesozooplankton investigated. In 2002 (4 to 24 March), 3 mesocosms comprising a …
Effects Of Sunlight On Decomposition Of Estuarine Dissolved Organic C, N And P And Bacterial Metabolism, Sl Mccallister, Je Bauer, J Kelly, Hw Ducklow
Effects Of Sunlight On Decomposition Of Estuarine Dissolved Organic C, N And P And Bacterial Metabolism, Sl Mccallister, Je Bauer, J Kelly, Hw Ducklow
VIMS Articles
The effects of natural sunlight and microbial decomposition on DOC, DON, and DOP were investigated along the salinity gradient of a temperate coastal plain estuary. The impact of sunlight-irradiated DOM on bacterial properties (bacterial abundance, production, bacterial growth efficiency [BGE]) was also followed. Surface-water light levels resulted in no detectable abiotic production of NH4+ or PO43- or loss of DOC. Bacterial decomposition of DOC was enhanced by 27 to 200 % in irradiated relative to dark treatments. There was, however, no corresponding enhancement in DON and DOP remineralization. Significant differences in bacterial decomposition of light-exposed DOC were frequently observed following …
Flood Dispersal And Deposition By Near-Bed Gravitational Sediment Flows And Oceanographic Transport: A Numerical Modeling Study Of The Eel River Shelf, Northern California, Courtney K. Harris, Peter A. Traykovski, W. Rockwell Geyer
Flood Dispersal And Deposition By Near-Bed Gravitational Sediment Flows And Oceanographic Transport: A Numerical Modeling Study Of The Eel River Shelf, Northern California, Courtney K. Harris, Peter A. Traykovski, W. Rockwell Geyer
VIMS Articles
[1] A large flood of the Eel River, northern California, created a thick sediment deposit between water depths of 50 and 70 m in January 1997. The freshwater plume, however, confined sediment delivery to water depths shallower than 30 m. Mechanisms proposed to explain the apparent cross-shelf transport include dispersal by oceanographic currents, resuspension by energetic waves, and gravitationally forced transport of a thin layer of fluidized mud. Field observations indicate that these processes were all active but cannot determine their relative significance or whether these mechanisms alone explain the location, size, and timing of deposition. Approximately 30% of the …
Calculating Highly Fluctuated Suspended Sediment Fluxes From Mountainous Rivers In Taiwan, Shuh-Ji Kao, Tsung-Yu Lee, J. D. Milliman
Calculating Highly Fluctuated Suspended Sediment Fluxes From Mountainous Rivers In Taiwan, Shuh-Ji Kao, Tsung-Yu Lee, J. D. Milliman
VIMS Articles
Small drainage basins, highly fractured rock, high relief, and steep gradients make Taiwan watersheds particularly sensitive to episodic events such as typhoons and earthquakes, and to various types of anthropogenic disturbance. Here we analyze the characteristics of a long-term hydrological dataset from Taiwan and re-evaluate methods used to calculate sediment loads for Taiwan's event-driven rivers. We suggest using the rating curve method stratified down to seasonal levels to reflect the rapid changes in the relationship between water discharge and suspended sediment load. A program is developed to determine the optimal time-interval for constructing rating curves, and is used to calculate …
Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Mr Mulholland, Da Bronk, Dg Capone
Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Mr Mulholland, Da Bronk, Dg Capone
VIMS Articles
Two methods used to measure dinitrogen (N-2) fixation (acetylene reduction and N-15(2) uptake) often result in different N-2 fixation rates. Part of the discrepancy may arise from the observation that Trichodesmium can release a fraction of their recently fixed N-2 as dissolved organic nitrogen (DON) and/or ammonium (NH4+). To resolve outstanding issues regarding N-2 fixation and the production of dissolved combined nitrogen (N) by Trichodesmium, we conducted a comprehensive analysis of N-2 fixation and the production of DON and NH4+ in cultures of Trichodesmium IMS101. We performed N-15(2) uptake experiments in parallel with acetylene (C2H2) reduction assays, and measured production …
Linking Watershed Loading And Basin-Level Carrying Capacity Models To Evaluate The Effects Of Land Use On Primary Production And Shellfish Aquaculture, Mark Luckenbach, Harry V. Wang
Linking Watershed Loading And Basin-Level Carrying Capacity Models To Evaluate The Effects Of Land Use On Primary Production And Shellfish Aquaculture, Mark Luckenbach, Harry V. Wang
VIMS Articles
Aquaculture production of hard clams, Mercenaria mercenaria, in the lower Chesapeake Bay, Virginia, U.S.A., has increased dramatically within the last decade. In recent years concern has been raised that some growing areas may be approaching the exploitation carrying capacity for clam production. Preliminary calculations indicate that large-scale intensive clam aquaculture may be controlling nutrient and phytoplankton dynamics in this system. To date, carrying capacity models have not been applied to this system, but we are in the process of building models for that purpose. Moreover changing land use in the watersheds surrounding the clam-producing areas raises the need for an …
Examination Of Reference Concentration Under Waves And Currents On The Inner Shelf, Guan-Hong Lee, W. Brian Dade, Carl T. Friedrichs, Chris E. Vincent
Examination Of Reference Concentration Under Waves And Currents On The Inner Shelf, Guan-Hong Lee, W. Brian Dade, Carl T. Friedrichs, Chris E. Vincent
VIMS Articles
[ 1] We examine reference concentration using three different data sets of near-bed suspended sediment concentration observed under combined waves and currents. The data include observations made at 15 and 20 m depth off Dounreay, Scotland, UK, and observations obtained at 13 m depth off Duck, North Carolina, USA. These data accommodate different dynamic conditions ( from wave-dominated conditions at Dounreay to wind-driven, current-dominated conditions at Duck) and sediment properties ( median size of bed sediment ranging from 120 to 350 mm). Near-bed concentration profiles to elevations of about 80 cm were obtained using acoustic backscatter sensors with 1 cm …
Observations On The Distribution Of Meroplankton During An Upwelling Event, Al Shanks, J Largier, J Brubaker
Observations On The Distribution Of Meroplankton During An Upwelling Event, Al Shanks, J Largier, J Brubaker
VIMS Articles
The distribution of the larvae of benthic invertebrates was investigated relative to hydrographic structures as a test of the hypothesi's that larvae behave as if they are passive particles. Observations of larval and oceanographic distributions were made off Duck, North Carolina, USA in August 1994. Conditions were characterized by wind-driven coastal upwelling;flow was generally offshore near the surface and onshore below the pycnocline. Within 5 km of the shore the pycnocline was bent upward by the upwelling and it intersected the surface along most of the transects. In zooplankton samples, 20 taxa of larvae were counted (10 bivalve veligers, nine …
Dissolved Organic Nitrogen: A Dynamic Participant In Aquatic Ecosystems, T Berman, Da Bronk
Dissolved Organic Nitrogen: A Dynamic Participant In Aquatic Ecosystems, T Berman, Da Bronk
VIMS Articles
In both marine and freshwaters, the concentration of dissolved organic nitrogen (DON) frequently exceeds that of dissolved inorganic nitrogen (DIN), including ammonium, nitrate, and nitrite. Recent evidence indicates that many organic N compounds are released into the DON pool and taken up from this pool by planktonic microbiota on timescales of hours to days. This observation suggests that many components of the DON pool can play an active role in supplying N nutrition directly or indirectly to phytoplankton and bacteria and, in so doing, may affect the species composition of the ambient microbial assemblage. Here we present an overview of …
Numerical Modeling Of Gravity-Driven Sediment Transport And Deposition On An Energetic Continental Shelf: Eel River, Northern California, M. Scully, Carl T. Friedrichs, L. D. Wright
Numerical Modeling Of Gravity-Driven Sediment Transport And Deposition On An Energetic Continental Shelf: Eel River, Northern California, M. Scully, Carl T. Friedrichs, L. D. Wright
VIMS Articles
A two-dimensional numerical model was applied to predict large-scale deposition by wave-supported sediment gravity flows on the Eel River continental shelf for four consecutive flood seasons using measured bathymetry, waves and river forcing. The model assumes that sediment-induced stratification maintains the near-bed Richardson number at its critical value, which determines the sediment carrying capacity of the wave boundary layer. Deposition is predicted when the gravity-driven flux of sediment exceeds the carrying capacity. The model predicted 26% of fine sediment discharged by the Eel River to be deposited on the midshelf with a magnitude and distribution largely consistent with field observations. …
Spectral Estimates Of Bed Shear Stress Using Suspended-Sediment Concentrations In A Wave-Current Boundary Layer, Guan-Hong Lee, W. Brian Dade, Carl T. Friedrichs, Chris E. Vincent
Spectral Estimates Of Bed Shear Stress Using Suspended-Sediment Concentrations In A Wave-Current Boundary Layer, Guan-Hong Lee, W. Brian Dade, Carl T. Friedrichs, Chris E. Vincent
VIMS Articles
High-resolution time series of suspended-sediment profiles have been obtained using an acoustic backscatter system at an inner shelf site (North Carolina) where flows are dominated by wind-driven currents and waves. We analyzed the spatial and temporal structure of near-bed turbulence in particle-transporting flows and scalar-like fluctuations of suspended-sediment concentrations. An important element of our analysis is a new inertial dissipation method for passive tracers to estimate the shear stress acting on the seabed, using the spectral properties of suspended sediment concentrations observed by acoustic backscatter sensors. In flows that provide adequate separation of the scales of turbulence production and dissipation, …
Observations On The Distribution Of Meroplankton During A Downwelling Event And Associated Intrusion Of The Chesapeake Bay Estuarine Plume, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff
Observations On The Distribution Of Meroplankton During A Downwelling Event And Associated Intrusion Of The Chesapeake Bay Estuarine Plume, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff
VIMS Articles
We investigated the dispersal of larvae of benthic invertebrates and tested the hypothesis that larvae behaved as if they were passive particles. Observations were made off Duck, North Carolina, USA diving a period of wind driven downwelling at the coast and an intrusion of estuarine water from the Chesapeake Bay. The plume of estuarine water (salinity < 30 psu) was strongest at the shoreward stations in the more northern transects. Wind driven shoreward surface flow, converged at the seaward edge of the plume and downwelled. Offshore flow was present below the thermocline and caused the thermocline to bend downward and contact the bottom at between 5 and 10 km offshore. In the zooplankton samples, we enumerated 33 taxa of larvae (17 taxa of bivalve veligers, 10 taxa of gastropod veligers, and 6 taxa of polychaete larvae). Using cluster analysis, larvae were separated into groups with similar patterns of distribution. If larvae were acting as passive particles then we hypothesized that: 1) Their distribution should remain tied to a water mass and 2) around a convergence or divergence, there should be no change in larval concentration. The distributions of larvae in Clusters 1, 4, 5, and 6 were consistent with the hypothesis that thy were acting as passive particles. Larvae in Clusters 2 and 3, however, did not appear to be acting as passive particles. Larvae in Cluster 2 did not remain tied to a water mass. They entered the study area in the estuarine plume waters, but within 20 km they were nearly absent from the plume water and were found seaward of the plume and at greater depth. Larvae in Cluster 3 were most abundant in areas of converging currents where the shoreward flowing surface waters downwelled at the plume front or against the shore. We hypothesized that larvae of organisms which as adults live in the intertidal or shallow, subtidal zones would have more nearshore distributions than the larvae of adults that are broadly distributed across the shelf. We compared the depth of the habitat of the adult bivalves from which the bivalve larvae in the different clusters were derived. The results were consistent with the hypothesis; larvae with distributions closer to shore tended to come from adults found at shallower depths or in the intertidal zone.
Assimilating High-Resolution Salinity Data Into A Model Of A Partially Mixed Estuary, Jiangtao Xu, Shenn-Yu Chao, Raleigh R. Hood, Harry V. Wang
Assimilating High-Resolution Salinity Data Into A Model Of A Partially Mixed Estuary, Jiangtao Xu, Shenn-Yu Chao, Raleigh R. Hood, Harry V. Wang
VIMS Articles
[1] A three-dimensional circulation model of the Chesapeake Bay is used to validate a simple data assimilation scheme, using high-resolution salinity data acquired from a ship-towed undulating vehicle (a Scanfish). The simulation period spans the entire year of 1995 during which the high-resolution Scanfish data were available in July and October, lasting a few days each. Since Scanfish data were irregularly distributed in time and space, only salinity fields are nudged in the model for simplicity. Model improvements through data assimilation are evaluated from a pair of experiments: one with data assimilation and one without. Data from scattered Chesapeake Bay …
Examination Of Diffusion Versus Advection Dominated Sediment Suspension On The Inner Shelf Under Storm And Swell Conditions, Duck, North Carolina, Guan-Hong Lee, Carl T. Friedrichs, Chris E. Vincent
Examination Of Diffusion Versus Advection Dominated Sediment Suspension On The Inner Shelf Under Storm And Swell Conditions, Duck, North Carolina, Guan-Hong Lee, Carl T. Friedrichs, Chris E. Vincent
VIMS Articles
[1] A benthic boundary layer tripod supporting six current meters and three profiling acoustic backscatter sensors (ABS) documented storm and swell conditions during the fall of 1996 at a depth of 13 m on the inner shelf off Duck, North Carolina. Sediment concentration was higher in the wave boundary layer (WBL) during storm conditions but higher similar to40 cm above the bed (cm ab) during swell conditions. To test the applicability of a diffusive balance during storm versus swell, ABS data were used to invert the vertical diffusion equation and solve for eddy diffusivity from 1 to 50 cm ab. …
Across-Shelf Sediment Transport: Interactions Between Suspended Sediment And Bed Sediment, Courtney K. Harris, Patricia Wiberg
Across-Shelf Sediment Transport: Interactions Between Suspended Sediment And Bed Sediment, Courtney K. Harris, Patricia Wiberg
VIMS Articles
[1] We use a two-dimensional, time-dependent sediment-transport model to quantify across-shelf transport, deposition, and sorting during wave-driven resuspension events characteristic of those that dominate sediment transport on many continental shelves. Decreases in wave-orbital velocities as water depth increases, and the resulting cross-shelf gradient in bed shear stress favor a net offshore transport of sediment. On wide, flat shelves (slopes similar to0.1%), these gradients are low, and the depth to which the seabed is reworked depends mainly on bottom shear stress and local sediment availability. On narrow, steep shelves (slopes similar to0.5%), however, the gradient in bottom stress generates significant cross-shelf …
Photochemical Production Of Dissolved Inorganic Nitrogen And Primary Amines From Dissolved Organic Nitrogen In Waters Of Two Estuaries And Adjacent Surficial Groundwaters, Dj Koopmans, Da Bronk
Photochemical Production Of Dissolved Inorganic Nitrogen And Primary Amines From Dissolved Organic Nitrogen In Waters Of Two Estuaries And Adjacent Surficial Groundwaters, Dj Koopmans, Da Bronk
VIMS Articles
Recent studies have shown that in a number of humic-rich surface waters in North America, NH4+ is released when dissolved organic matter (DOM) is exposed to sunlight. However, photochemical NH4+ production has not been observed in all surface waters, and factors that contribute to it are not well understood. We hypothesized that the presence or absence of NH4+ photoproduction may be affected by the light exposure history of DOM, The present study was undertaken to determine whether DOM from surficial groundwaters, with minimal light exposure history, would produce labile nitrogen (N) photoproducts more consistently, In this study, estuarine surface waters …
Delivery And Fate Of Fluvial Water And Sediment To The Sea: A Marine Geologist's View Of European Rivers, J. D. Milliman
Delivery And Fate Of Fluvial Water And Sediment To The Sea: A Marine Geologist's View Of European Rivers, J. D. Milliman
VIMS Articles
Despite their relatively small drainage areas, European rivers reflect a wide variety of hydrologic regimes, although with very few exceptions they have been strongly affected by human activity. Scandinavian rivers (particularly those draining Iceland and western Norway) can have high runoff, and, except for those draining Iceland, all have very low suspended and dissolved sediment loads. Northern and western European rivers have somewhat lower runoff, among the lowest suspended sediment yields in the world, and anthropogenically enhanced dissolved solid loads. Annual discharge of many of these rivers appears to vary inversely with the North Atlantic Oscillation index. Rivers discharging from …
Modeling The Response Of Top-Down Control Exerted By Gelatinous Carnivores On The Black Sea Pelagic Food Web, Temel Oguz, Hugh W. Ducklow, Jennifer E. Purcell, Paola Malanotte-Rizzoli
Modeling The Response Of Top-Down Control Exerted By Gelatinous Carnivores On The Black Sea Pelagic Food Web, Temel Oguz, Hugh W. Ducklow, Jennifer E. Purcell, Paola Malanotte-Rizzoli
VIMS Articles
Recent changes in structure and functioning of the interior Black Sea ecosystem are studied by a series of simulations using a one-dimensional, vertically resolved, coupled physical-biochemical model. The simulations are intended to provide a better understanding of how the pelagic food web structure responds to increasing grazing pressure by gelatinous carnivores (medusae Aurelia aurita and ctenophore Mnemiopsis leidyi) during the past 2 decades. The model is first shown to represent typical eutrophic ecosystem conditions of the late 1970s and early 1980s. This simulation reproduces reasonably well the observed planktonic food web structure at a particular location of the Black Sea …
Nitrogen Cycling Through A Fringing Marsh-Aquifer Ecotone, Cr Tobias, Iris C. Anderson, Elizabeth A. Canuel, Sa Macko
Nitrogen Cycling Through A Fringing Marsh-Aquifer Ecotone, Cr Tobias, Iris C. Anderson, Elizabeth A. Canuel, Sa Macko
VIMS Articles
Fringing wetlands are critical components of estuarine systems, and subject to water fluxes from both watersheds and estuaries. To assess the effect of groundwater discharge on marsh nitrogen cycling, we measured N-cycling in sediments from a fringing mesohaline marsh in Virginia which receives a seasonal groundwater input. Mineralization, nitrification, potential denitrification (DNF), and potential dissimilatory nitrate reduction to ammonium (DNRA) rates were estimated along with porewater concentrations of oxygen, sulfide, and conductivity during high (May 1997) and low (October 1997) groundwater discharge. All N-cycling processes were confined to the upper 1 to 1.5 m of marsh, where organic matter and …
Bacterial Consumption Of Doc During Transport Through A Temperate Estuary, Pa Raymond, Je Bauer
Bacterial Consumption Of Doc During Transport Through A Temperate Estuary, Pa Raymond, Je Bauer
VIMS Articles
Bacterial utilization of natural levels of dissolved organic carbon (DOC) was measured in the York River estuary, a sub-estuary of the Chesapeake Bay. This study was undertaken in order to elucidate spatial and temporal changes in bacterial carbon utilization and to evaluate its importance as a pathway for organic matter transformation in estuaries. Multiple pools of DOC were defined based on decomposition kinetics. The first pool (G(1)) made up a mean of 2.8% of total DOC and had turnover times of less than or equal to 5 d. The second pool (G(2)) comprised an average of 4.9% of total DOC …
Demonstration Of The Onshore Transport Of Larval Invertebrates By The Shoreward Movement Of An Upwelling Front, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff
Demonstration Of The Onshore Transport Of Larval Invertebrates By The Shoreward Movement Of An Upwelling Front, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff
VIMS Articles
Upwelling winds off North Carolina set up upwelling fronts. As the wind forcing relaxed following such a coastal upwelling event, we observed the upwelling front move onshore. The low-density surface water moved shoreward over the upwelled water, forming a convergence zone at the-front. This shoreward-moving front concentrated and transported larvae. Larval sergestid shrimp, spionid polychaete larvae, and the veligers of Odostomia sp. and Bittium sp, were concentrated on the seaward side of the moving convergence. Blue crab megalopae were concentrated at the surface immediately seaward of the front. These data demonstrate that a relaxing upwelling front can transport high concentrations …
Flow Convergence And Stability At A Tidal Estuarine Front: Acoustic Doppler Current Observations, John M. Brubaker, John H. Simpson
Flow Convergence And Stability At A Tidal Estuarine Front: Acoustic Doppler Current Observations, John M. Brubaker, John H. Simpson
VIMS Articles
Characteristics of the flow field in an estuarine frontal zone have been investigated in a field study in the lower James River estuary. Underway sampling with an acoustic Doppler current profiler (ADCP) on repeated transects across the front provided information on the structure of the flow field near the front and its evolution in time. As this tidal intrusion front advanced up the estuary during the flooding tide, prominent and consistent features in the velocity field included a localized zone of convergent flow beneath the visible surface line and a stratified shear layer just upriver of the front. Within the …
Effects Of Wind Speed And Particulate Matter Source On Surface Microlayer Characteristics And Enrichment Of Organic Matter In Southern Chesapeake Bay, Kewen Liu, Rebecca M. Dickhut
Effects Of Wind Speed And Particulate Matter Source On Surface Microlayer Characteristics And Enrichment Of Organic Matter In Southern Chesapeake Bay, Kewen Liu, Rebecca M. Dickhut
VIMS Articles
Surface microlayer (SM) samples were collected with a rotating cylinder sampler from the York and Elizabeth River estuaries of lower Chesapeake Bay bimonthly from May 1994 through June 1995. Two intensive samplings were also conducted in the York River during different seasons: one in December 1994 and another during June 1995. Four SM samples were collected during each intensive sampling within 4 days. All the samples were analyzed for total suspended particulates (TSP), particulate nitrogen (PN), particulate organic carbon (POC) and dissolved organic carbon(DOC). The thickness of the SM was observed to decrease linearly with increased wind speed. TSP and …
Sensitivity Of Bottom Stress And Bottom Roughness Estimates To Density Stratification, Eckernforde Bay, Southern Baltic Sea, Carl T. Friedrichs, Ld Wright
Sensitivity Of Bottom Stress And Bottom Roughness Estimates To Density Stratification, Eckernforde Bay, Southern Baltic Sea, Carl T. Friedrichs, Ld Wright
VIMS Articles
Thermohaline density stratification may significantly alter the classic near-bottom logarithmic velocity profile in many weak to moderately energetic, partially mixed estuaries. Results from Eckernforde Bay suggest fits to log profiles which neglect thermohaline stratification may lead to overestimates of bottom stress and roughness of the order of 130 % and 600 %, respectively. Measurements of velocity obtained at four heights within 1 m of the seabed are input to theoretical models for velocity shear derived via dimensional arguments for the ''overlap'' layer. Previous investigators applying dimensional arguments to thermohaline stratification in estuaries have assumed buoyancy flux to be independent of …
Simulation Of Annual Plankton Productivity Cycle In The Black Sea By A One-Dimensional Physical-Biological Model, Temel Oguz, Hugh Ducklow, Paola Malanotte-Rizzoli, Nikolai P. Nezlin, Umit Unluata
Simulation Of Annual Plankton Productivity Cycle In The Black Sea By A One-Dimensional Physical-Biological Model, Temel Oguz, Hugh Ducklow, Paola Malanotte-Rizzoli, Nikolai P. Nezlin, Umit Unluata
VIMS Articles
The annual cycle of the plankton dynamics in the central Black Sea is studied by a one-dimensional vertically resolved physical-biological upper ocean model, coupled with the Mellor-Yamada level 2.5 turbulence closure scheme. The biological model involves interactions between the inorganic nitrogen (nitrate, ammonium), phytoplankton and herbivorous zooplankton biomasses, and detritus. Given a knowledge of physical forcing, the model simulates main observed seasonal and vertical characteristic features, in particular, formation of the cold intermediate water mass and yearly evolution of the upper layer stratification, the annual cycle of production with the fall and the spring blooms, and the subsurface phytoplankton maximum …
Utilization And Turnover Of Labile Dissolved Organic Matter By Bacterial Heterotrophs In Eastern North Pacific Surface Waters, J Cherrier, Je Bauer, Erm Druffel
Utilization And Turnover Of Labile Dissolved Organic Matter By Bacterial Heterotrophs In Eastern North Pacific Surface Waters, J Cherrier, Je Bauer, Erm Druffel
VIMS Articles
Seawater incubation experiments were conducted in June and October 1992 to examine bacterial utilization of labile dissolved organic matter (DOM) in open ocean surface waters of the eastern North Pacific. Natural plankton extract-DOM (PE-DOM) and selected model compounds were added to seawater samples to evaluate bacterial utilization and respiration rates relative to bacterial carbon production rates for the various amendments. PE-DOM always stimulated bacterial production and DOM utilization, and the primary nitrogen source supporting this bacterial production was dissolved organic nitrogen (DON). Utilization of DON during exponential growth was balanced by the production of ammonium for samples amended with PE-DOM. …