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Articles 661 - 690 of 1097

Full-Text Articles in Oceanography

Inner Shelf Circulation In Coastal Virginia: A Data Assimilation Approach, Hector Hito Sepulveda Jan 2004

Inner Shelf Circulation In Coastal Virginia: A Data Assimilation Approach, Hector Hito Sepulveda

OES Theses and Dissertations

The primary objective of this dissertation is to describe the tidal and subtidal flow patterns over the inner shelf of the Delmarva Peninsula, located in the Mid-Atlantic Bight of the United States (36.6–38.0 N), north of the Chesapeake Bay. The objective is pursued with a combination of direct measurements and numerical assimilative techniques. The dynamic balance of the study area is little known, and the distribution of tidal properties has not been described for this area since very rough descriptions in the 1950's. Hydrographic and current velocity profiles from four regional cruises in the inner shelf were used to study …

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Sources And Cycling Of Carbonyl Sulfide In The Sargasso Sea, Gregory A. Cutter, Lynda S. Cutter, Katherine C. Filippino Jan 2004

Sources And Cycling Of Carbonyl Sulfide In The Sargasso Sea, Gregory A. Cutter, Lynda S. Cutter, Katherine C. Filippino

OES Faculty Publications

The cycling of the radiatively important gas carbonyl sulfide (OCS) was studied in surface waters of the Sargasso Sea. In August 1999, surface OCS concentrations averaged 8.6 pmol L-1, showed minor diel variations, and varied little with depth. An OCS precursor, total dissolved organic sulfur (DOS), was lowest at the surface (40 nmol L-1) and increased with depth. The photoproduction rate of OCS from in situ incubations averaged 9.6 pmol L-1 h-1, whereas dark production was 7.0 pmol L-1 h-1. Apparent quantum yields were 10-5-10-7 from 313-436 …

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Light Dependence Of Selenium Uptake By Phytoplankton And Implications For Predicting Selenium Incorporation Into Food Webs, Stephen B. Baines, Nicholas S. Fisher, Martina A. Doblin, Gregory A. Cutter, Lynda S. Cutter, Brian Cole Jan 2004

Light Dependence Of Selenium Uptake By Phytoplankton And Implications For Predicting Selenium Incorporation Into Food Webs, Stephen B. Baines, Nicholas S. Fisher, Martina A. Doblin, Gregory A. Cutter, Lynda S. Cutter, Brian Cole

OES Faculty Publications

The potentially toxic element selenium is first concentrated from solution to a large but highly variable degree by algae and bacteria before being passed on to consumers. The large loads of abiotic and detrital suspended particles often present in rivers and estuaries may obscure spatial and temporal patterns in Se concentrations at the base of the food web. We used radiotracers to estimate uptake of both selenite (Se(IV)) and C by intact plankton communities at two sites in the Sacramento/San Joaquin River Delta. Our goals were to determine (1) whether C and Se(IV) uptake were coupled, (2) the role of …

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Analytical Intercomparison Between Flow Injection-Chemiluminescence And Flow Injection-Spectrophotometry For The Determination Of Picomolar Concentrations Of Iron In Seawater, Andrew R. Bowie, Peter N. Sedwick, Paul J. Worsfold Jan 2004

Analytical Intercomparison Between Flow Injection-Chemiluminescence And Flow Injection-Spectrophotometry For The Determination Of Picomolar Concentrations Of Iron In Seawater, Andrew R. Bowie, Peter N. Sedwick, Paul J. Worsfold

OES Faculty Publications

A lab- and ship-based analytical intercomparison of two flow injection methods for the determination of iron in seawater was conducted, using three different sets of seawater samples collected from the Southern Ocean and South Atlantic. In one exercise, iron was determined in three different size-fractions (< 0.03 &μm, < 0.4 μm, and unfiltered) in an effort to better characterize the operational nature of each analytical technique with respect to filter size. Measured Fe concentrations were in the range 0.19 to 1.19 nM using flow injection with luminol chemiluminescence detection (FI-CL), and 0.07 to 1.54 nM using flow injection with catalytic spectrophotometric detection with N, N-dimethyl-p-phenylenediamine dihydrochloride (FI-DPD). The arithmetic mean for the FI-CL method was higher (by 0.09 nM) than the FI-DPD method for dissolved (< 0.4 μm) Fe, a difference that is comparable to the analytical blanks, which were as high as 0.13 nM ( CL) and 0.09 nM (DPD). There was generally good agreement between the FI-CL determinations for the < 0.03 μm size fraction and the FI-DPD determinations for the < 0.4 μm size fraction in freshly collected samples. Differences in total-dissolvable ( unfiltered) Fe concentrations determined by the two FI methods were more variable, reflecting the added complexity associated with the analysis of partially digested particulate material in these samples. Overall, however, the FI-CL determinations were significantly (P = 0.05) lower than the FI-DPD determinations for the unfiltered samples. Our results suggest that the observed, systematic inter-method differences reflect measurement of different physicochemical fractions of Fe present in seawater, such that colloidal and/or organic iron species are better determined by the FI-CL method than the FI-DPD method. This idea is supported by our observation that inter-method differences were largest for freshly collected acidified seawater, which suggests extended storage (>6 months) of acidified samples as a possible protocol for the determination of dissolved iron in seawater.

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Influence Of Short-Term Variations In Food On Survival Of Crassotrea Gigas Larvae: A Modeling Study, Eric N. Powell, Eleanor A, Bochenek, John M. Klinck, Eileen E. Hofmann Jan 2004

Influence Of Short-Term Variations In Food On Survival Of Crassotrea Gigas Larvae: A Modeling Study, Eric N. Powell, Eleanor A, Bochenek, John M. Klinck, Eileen E. Hofmann

OES Faculty Publications

A biochemically-based model was developed to simulate the growth, development, and metamorphosis of larvae of the Pacific oyster, Crassostrea gigas. The model defines larvae in terms of their protein, lipid, carbohydrate, and ash content and includes variation in growth efficiency and egg quality to better simulate cohort population dynamics. Changes in tissue composition occur as the larva grows and in response to the biochemical composition of the food. The premise behind this modeling study was that certain periods of larval life are more critical than others with respect to the availability of food and that food quality is as …

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Physical Forcing Of Phytoplankton Community Structure And Primary Production In Continental Shelf Waters Of The Western Antarctic Peninsula, Barbara B. Prézelin, Eileen E. Hofmann, Mark Moline, John M. Klinck Jan 2004

Physical Forcing Of Phytoplankton Community Structure And Primary Production In Continental Shelf Waters Of The Western Antarctic Peninsula, Barbara B. Prézelin, Eileen E. Hofmann, Mark Moline, John M. Klinck

OES Faculty Publications

Analyses of a multidisciplinary data set, collected in continental shelf waters of the Western Antarctic Peninsula (WAP) during austral summer of January 1993, identified a previously unrecognized forcing mechanism that sets up a physical and chemical structure that supports and assures site-specific diatom-dominated communities and enhanced biological production (Prézelin et al., 2000). This forcing is active when the southern boundary of the Antarctic Circumpolar Current (ACC) flows along the shelf edge, thereby facilitating onshelf bottom intrusions of nutrient-rich Upper Circumpolar Deep Water (UCDW), which then is upwelled or mixed into the upper water column. At times or locations where UCDW …

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Black Carbon In Estuarine And Coastal Ocean Dissolved Organic Matter, Antonio Mannino, H. Rodger Harvey Jan 2004

Black Carbon In Estuarine And Coastal Ocean Dissolved Organic Matter, Antonio Mannino, H. Rodger Harvey

OES Faculty Publications

We measured black carbon (BC) in ultrafiltered, high-molecular weight dissolved organic matter (UDOM) in surface waters of Delaware Bay, Chesapeake Bay, and the adjacent Atlantic Ocean (U.S.A.) to investigate the importance of riverine and estuarine dissolved organic matter (DOM) as a source of BC to the ocean. BC was 5-72% of UDOM-C (27 ± 17%), which corresponds to 8.9 ± 6.5% of dissolved organic carbon (DOC), with higher values in the heavily urbanized midbay region of the Delaware Estuary and lower yields in the river and coastal ocean. The spatial and seasonal distributions of BC along the salinity gradient of …

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Relevant Scales In Zooplankton Ecology: Distribution, Feeding, And Reproduction Of The Copepod Acartia Hudsonica In Response To Thin Layers Of The Diatom Skeletonema Costatum, Alexander B. Bochdansky, Stephen M. Bollens Jan 2004

Relevant Scales In Zooplankton Ecology: Distribution, Feeding, And Reproduction Of The Copepod Acartia Hudsonica In Response To Thin Layers Of The Diatom Skeletonema Costatum, Alexander B. Bochdansky, Stephen M. Bollens

OES Faculty Publications

We investigated the interaction of the copepod Acartia hudsonica in relation to thin layers of the diatom Skeletonema costatum. Thin layers have recently received much attention, since they are common and persistent features in the water column, often overlooked by traditional sampling methods. Their frequent abundance in coastal oceans and the high biomass associated with them has led to the assumption that they are important grazing sites of calanoid copepods. We employed 2-m tall tower tanks that allowed us to simulate thin layers. Three variables representative of three time scales were considered: the distribution of copepods in the tanks …

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Interactive Regulation Of Dissolved Copper Toxicity By An Estuarine Microbial Community, Christina L. Dryden, Andrew S. Gordon, John R. Donat Jan 2004

Interactive Regulation Of Dissolved Copper Toxicity By An Estuarine Microbial Community, Christina L. Dryden, Andrew S. Gordon, John R. Donat

OES Faculty Publications

Cultured marine microorganisms under copper stress produce extracellular compounds having a high affinity for copper (copper-complexing ligands). These ligands are similar in binding strength to those found in natural waters, but few studies have examined the relationship between copper, copper-complexing ligand concentrations, and natural microbial populations. A series of in situ experiments in the Elizabeth River, Virginia, revealed that an intact estuarine microbial community responded to copper stress by production of extracellular, high-affinity copper-complexing ligands. The rate of ligand production was dependent on copper concentration and resulted in a reduction of the concentration of free cupric ions, Cu2+, …

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Age And Growth Of Scotia Sea Icefish, Chaenocephalus Aceratus, From The South Shetland Islands, M. La Mesa, J. Ashford, E. Larson, M. Vacchi Jan 2004

Age And Growth Of Scotia Sea Icefish, Chaenocephalus Aceratus, From The South Shetland Islands, M. La Mesa, J. Ashford, E. Larson, M. Vacchi

OES Faculty Publications

Samples of Chaenocephalus aceratus (Lönnberg) were collected during a trawl survey carried out around the South Shetland Islands in January–February 2002. Fish were caught by commercial bottom trawl fishing down to 500 m depth, using a stratified randomized sampling design. As observed in other recent surveys within the same area, C. aceratus represented one of the predominant species. Overall, 357 specimens ranging from 13 and 67 cm (TL) were selected for the present study. Ages were estimated by counting annuli present in the sagittal otoliths, exposed by grinding and polishing along their sagittal plane. To estimate the precision of age …

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Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Margaret R. Mulholland, Deborah A. Bronk, Douglas G. Capone Jan 2004

Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Margaret R. Mulholland, Deborah A. Bronk, Douglas G. Capone

OES Faculty Publications

Two methods used to measure dinitrogen (N2) fixation (acetylene reduction and 15N2 uptake) often result in different N2 fixation rates. Part of the discrepancy may arise from the observation that Trichodesmium can release a fraction of their recently fixed N2 as dissolved organic nitrogen (DON) and/or ammonium (NH4 +). To resolve outstanding issues regarding N2 fixation and the production of dissolved combined nitrogen (N) by Trichodesmium, we conducted a comprehensive analysis of N2 fixation and the production of DON and NH4+ in cultures of Trichodesmium IMS101. We performed …

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A Holocene Record Of Changing Arctic Ocean Ice Drift Analogous To The Effects Of The Arctic Oscillation, Dennis A. Darby, Jens F. Bischof Jan 2004

A Holocene Record Of Changing Arctic Ocean Ice Drift Analogous To The Effects Of The Arctic Oscillation, Dennis A. Darby, Jens F. Bischof

OES Faculty Publications

The Arctic Oscillation (AO) controls the configuration of the Transpolar Drift (TPD). If thicker ice from the Beaufort Gyre were exported, the volume of fresh water/sea ice in the Nordic seas would significantly increase, decreasing the formation of North Atlantic deep water. This would cool large parts of the Northern Hemisphere and affect global climate. Therefore, in order to understand how the global climate system functions, it is imperative to know how the TPD changed over the last millennium or more. The provenance of grains in a sediment core located near the confluence of the TPD and the Beaufort Gyre …

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Advection, Krill, And Antarctic Marine Ecosystems, Eileen E. Hofmann, Eugene J. Murphy Jan 2004

Advection, Krill, And Antarctic Marine Ecosystems, Eileen E. Hofmann, Eugene J. Murphy

CCPO Publications

Advective processes are recognized as being important in structuring and maintaining marine ecosystems. In the Southern Ocean advective effects are perhaps most clearly observed because the Antarctic Circumpolar Current (ACC) provides a connection between most parts of the system, including open ocean and continental shelf regions. The ACC also provides a mechanism for large-scale transport of plankton, such as Antarctic krill (Euphousia superba Dana), which is an important component of the Southern Ocean food web. This overview provides a summary of recent observational and modelling results that consider the importance of advection to the Southern Ocean ecosystem and, in particular, …

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Estimation Of Drag Coefficient In James River Estuary Using Tidal Velocity Data From A Vessel-Towed Adcp, Chunyan Li, Arnoldo Valle-Levinson, Larry P. Atkinson, Kuo Chuin Wong, Kamazima M. M. Lwiza Jan 2004

Estimation Of Drag Coefficient In James River Estuary Using Tidal Velocity Data From A Vessel-Towed Adcp, Chunyan Li, Arnoldo Valle-Levinson, Larry P. Atkinson, Kuo Chuin Wong, Kamazima M. M. Lwiza

CCPO Publications

[1] A phase-matching method is introduced to calculate the bottom drag coefficient in tidal channels with significant lateral variation of depth. The method is based on the fact that the bottom friction in a tidal channel causes tidal velocity to have a phase difference across the channel. The calculation involves a few steps. First, the observed horizontal velocity components are analyzed to obtain the amplitude and phase of the velocity at the major tidal frequency. The phase of the longitudinal velocity is then fitted to a relationship derived from the linearized momentum balance. The drag coefficient is then calculated. This …

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Numerical Study Of The Diapycnal Flow Through A Tidal Front With Passive Tracers, Chingming Dong, Robert Houghton, Hsien-Wang Ou, Dake Chen, Tal Ezer Jan 2004

Numerical Study Of The Diapycnal Flow Through A Tidal Front With Passive Tracers, Chingming Dong, Robert Houghton, Hsien-Wang Ou, Dake Chen, Tal Ezer

CCPO Publications

A two-dimensional numerical model is used to study the diapycnal flow through a tidal front with passive tracers. In a basic numerical experiment a passive tracer is released into the bottom water at the offshore edge of a tidal front, and it subsequently moves on-bank with a velocity that decreases with time. This qualitatively agrees with a recent field experiment using a dye tracer on Georges Bank. Additional experiments are performed to investigate the sensitivity of the tracer dispersion to the tidal phase and the location of tracer release within the front. As the release point is moved on-bank across …

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On The Sensitivity Of The West Caribbean Sea Circulation To Tides, Wind, And Mesoscale Ocean Eddies: A Three-Dimensional Ocean Model Study, Deeptha V. Thattai, Tal Ezer, Bjorn Kjerfve Jan 2004

On The Sensitivity Of The West Caribbean Sea Circulation To Tides, Wind, And Mesoscale Ocean Eddies: A Three-Dimensional Ocean Model Study, Deeptha V. Thattai, Tal Ezer, Bjorn Kjerfve

CCPO Publications

A three-dimensional, primitive equation ocean model is used to study the circulation in the West Caribbean Sea (WCS) region, and to test the sensitivity of the coastal flow to various forcing fields such as tides, climatological wind, and Caribbean eddies. The model domain is bordered by latitudes 15 – 22 degrees N and longitudes 76 – 87 degrees W, with the MesoAmerican Barrier Reef System (MBRS, along the coasts of Mexico, Belize, Guatemala, and Honduras) and the southern coast of Cuba as land boundaries. The WCS is open to the Caribbean Sea in the southeast and the Yucatan Channel in …

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A Modelling Study Of The Influence Of Environment And Food Supply On Survival Of Crassostrea Gigas Larvae, Eileen E. Hofmann, Eric N. Powell, Eleanor A. Bochenek, John M. Klinck Jan 2004

A Modelling Study Of The Influence Of Environment And Food Supply On Survival Of Crassostrea Gigas Larvae, Eileen E. Hofmann, Eric N. Powell, Eleanor A. Bochenek, John M. Klinck

CCPO Publications

A biochemically based model was developed to simulate the growth, development, and metamorphosis of larvae of the Pacific oyster (Crassostrea gigas). The unique characteristics of the model are that it: (1) defines larvae in terms of their protein, neutral lipid, polar lipid, carbohydrate, and ash content; (2) tracks weight separately from length to follow larval condition; and (3) includes genetic variation in growth efficiency and egg quality to better simulate cohort population dynamics. The model includes parameterizations for filtration, ingestion, and respiration, which determine larval growth rate, and processes controlling larval mortality and metamorphosis. Changes in larval tissue …

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Lagrangian Modelling Studies Of Antarctic Krill (Euphausia Superba) Swarm Formation, Eileen E. Hofmann, A. G. Edward Haskell, John M. Klinck, Cathy M. Lascara Jan 2004

Lagrangian Modelling Studies Of Antarctic Krill (Euphausia Superba) Swarm Formation, Eileen E. Hofmann, A. G. Edward Haskell, John M. Klinck, Cathy M. Lascara

CCPO Publications

A two-dimensional Lagrangian particle model was developed to examine the spatial distribution of Antarctic krill (Euphausia superba). The time-dependent location of particles, which represent krill individuals, is determined by random diffusion, foraging activity, and movement induced by the presence of neighbours. Foraging activity is based on prescribed food conditions and is such that krill swim slower and turn more frequently in areas of high food concentration. The presence or absence of neighbours either disperses krill, if the local concentrations become too dense, or coalesces krill, if concentrations become too dilute, respectively. Predation on krill is included and affects …

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Satellite Evidence Of Hurricane-Induced Phytoplankton Blooms In An Oceanic Desert, S. M. Babin, J. A. Carton, T. D. Dickey, J. D. Wiggert Jan 2004

Satellite Evidence Of Hurricane-Induced Phytoplankton Blooms In An Oceanic Desert, S. M. Babin, J. A. Carton, T. D. Dickey, J. D. Wiggert

CCPO Publications

The physical effects of hurricanes include deepening of the mixed layer and decreasing of the sea surface temperature in response to entrainment, curl-induced upwelling, and increased upper ocean cooling. However, the biological effects of hurricanes remain relatively unexplored. In this paper, we examine the passages of 13 hurricanes through the Sargasso Sea region of the North Atlantic during the years 1998 through 2001. Remotely sensed ocean color shows increased concentrations of surface chlorophyll within the cool wakes of the hurricanes, apparently in response to the injection of nutrients and/or biogenic pigments into the oligotrophic surface waters. This increase in post-storm …

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Modeled And Observed Empirical Orthogonal Functions Of Currents In The Yucatan Channel, Gulf Of Mexico, Lie-Yauw Oey, Tal Ezer, Wilton Sturges Jan 2004

Modeled And Observed Empirical Orthogonal Functions Of Currents In The Yucatan Channel, Gulf Of Mexico, Lie-Yauw Oey, Tal Ezer, Wilton Sturges

CCPO Publications

Candela et al. [2003] have reported empirical orthogonal function (EOF) analyses based on 23-month current-meter and acoustic Doppler current profiler measurements in the Yucatan Channel. Those authors noted the difference between EOFs obtained from observations and their z-level models and EOFs calculated by Ezer et al. [2003] from the results of a terrain-following model. Here a new analysis is reported that explains this difference, and that also suggests the importance of shelf-edge meander mode of the core Loop Current in the channel. We show that the terrain-following model gives EOFs with characteristics similar to those observed when data from the …

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An Investigation Of Dissolved Organic Matter In A Shallow Coastal Bay Subject To Aureococcus Anophagefferens Blooms, Jean-Paul Simjouw Jan 2004

An Investigation Of Dissolved Organic Matter In A Shallow Coastal Bay Subject To Aureococcus Anophagefferens Blooms, Jean-Paul Simjouw

OES Theses and Dissertations

Aureococcus anophagefferens, the pelagophyte responsible for brown tide blooms, was identified in Chincoteague Bay in 1997 and has “bloomed” there since at least 1998. Aureococcus anophagefferens is capable of using dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) substrates to support growth, and this utilization is hypothesized to give the organism a competitive advantage relative to other phytoplankton when inorganic nutrient concentrations are low or depleted. Because previous studies suggest dissolved organic matter (DOM) is important in initiating and sustaining brown tide blooms, a field study of the variations in DOC concentration and DOM composition was performed at …

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Inter-Annual To Inter-Decadal Variability Of Upwelling And Anchovy Population Off Northern Chile, Jose L. Blanco-Garcia Jan 2004

Inter-Annual To Inter-Decadal Variability Of Upwelling And Anchovy Population Off Northern Chile, Jose L. Blanco-Garcia

OES Theses and Dissertations

The coastal ocean of northern Chile has persistent wind-driven upwelling that produces high nutrient and chlorophyll concentrations in a narrow band along the coast. The objective of this thesis is to study the low frequency temporal variability of the upwelling system, to understand the spatial and temporal changes in the wind field, and how these changes may affect the upwelling and anchovy variability. Data used in this thesis includes time series of wind, sea level, sea surface temperature, and atmospheric pressure at coastal stations, from 1960 to 2003, and oceanographic and acoustic cruises for the period 1993–2003. The time series …

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Strong Mid-Depth Currents And A Deep Cyclonic Gyre In The Gulf Of Mexico, Wilton Sturges, Eric Chassignet, Tal Ezer Nov 2003

Strong Mid-Depth Currents And A Deep Cyclonic Gyre In The Gulf Of Mexico, Wilton Sturges, Eric Chassignet, Tal Ezer

CCPO Publications

The main purpose of this work was to explore the possibility that the deep flow (~2000m) around the edges of the Gulf circulates in a cyclonic, or counter-clockwise direction. The existence of such flow was proposed on theoretical grounds but had not been previously documented. Our results are quite clear that such flow is reliably observed.

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Wind-Induced Exchange In Semi-Enclosed Basins, Rosario Sanay Oct 2003

Wind-Induced Exchange In Semi-Enclosed Basins, Rosario Sanay

OES Theses and Dissertations

The wind-induced circulation over laterally varying bathymetry was investigated in homogeneous and in stratified systems using the three-dimensional Regional Ocean Model (ROMS). For homogeneous systems, the focus was to describe the influence of the earth's rotation on the lateral distribution of the flow with particular emphasis on the transverse circulation. Along-basin wind-stress with no rotation caused a circulation dominated by an axially symmetric transverse structure consisting of downwind flow over the shoals and upwind flow in the channel along the whole domain. Transverse circulation was important only at the head of the system where the water sank and reversed direction …

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Experimental Investigation Of Elemental Incorporation In The Otoliths Of Larval And Juvenile Fish: Implications For Use As Environmental Recorders, Gretchen Bath Martin Jan 2003

Experimental Investigation Of Elemental Incorporation In The Otoliths Of Larval And Juvenile Fish: Implications For Use As Environmental Recorders, Gretchen Bath Martin

Biological Sciences Theses & Dissertations

Innovative techniques for discerning fish stocks, identifying nursery habitats, locating spawning sites, tracing larval transport pathways, and quantifying the degree of population connectivity are required to meet the goals of sustainable management of marine capture fisheries. One of the most promising techniques is the use of elemental signatures in fish otoliths (ear stones), which record valuable life history data and serve as the link between fish and their environment. To validate the assumption that otolith elemental composition is a function of water elemental concentrations, and to address the possible effects of external variables such as temperature and salinity, the composition …

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Effects Of Epiphyte Load On Optical Properties And Photosynthetic Potential Of The Seagrasses Thalassia Testudinum Banks Ex König And Zostera Marina L, Lisa A. Drake, Fred C. Dobbs, Richard C. Zimmerman Jan 2003

Effects Of Epiphyte Load On Optical Properties And Photosynthetic Potential Of The Seagrasses Thalassia Testudinum Banks Ex König And Zostera Marina L, Lisa A. Drake, Fred C. Dobbs, Richard C. Zimmerman

OES Faculty Publications

The biomass and optical properties of seagrass leaf epiphytes were measured to evaluate their potential impact on the photosynthetic performance of the seagrasses Thalassia testudinum Banks ex König (turtlegrass) and Zostera marina L. (eelgrass). Turtlegrass was obtained from oligotrophic waters near Lee Stocking Island, Bahamas; eelgrass was collected from a eutrophic environment in Monterey Bay, California. Leaf–epiphyte loads were characterized visually and quantified using measurements of their phospholipid biomass. Light absorption and reflectance of the intact epiphyte layer were determined spectrophotometrically. Turtlegrass epiphytes from the oligotrophic site absorbed a maximum of 36% of incident light in peak chlorophyll absorption …

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A Biooptical Model Of Irradiance Distribution And Photosynthesis In Seagrass Canopies, Richard C. Zimmerman Jan 2003

A Biooptical Model Of Irradiance Distribution And Photosynthesis In Seagrass Canopies, Richard C. Zimmerman

OES Faculty Publications

Although extremely vulnerable to coastal eutrophication, seagrasses represent important structuring elements and sources of primary production in shallow waters. They also generate an optical signature that can be tracked remotely. Accurate knowledge of light absorption and scattering by submerged plant canopies permits the calculation of important plant- and ecosystem-level properties, including rates of photosynthesis, vegetation abundance, and distribution. The objectives of this study were to develop a realistic, yet simply parameterized two-flow model of plane irradiance distribution through a seagrass canopy submerged in an optically active water column, to evaluate its performance against in situ measurements, and to explore the …

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Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert Jan 2003

Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert

OES Faculty Publications

Amino acid oxidation (AAO) and peptide hydrolysis (PH) are processes affecting the recycling of organic material and nutrients. We compared extracellular AAO and PH rates to C and N uptake rates along estuarine gradients of salinity, nutrients and productivity in the Pocomoke River, a subestuary of the Chesapeake Bay. This estuary is seasonally depleted in inorganic N, and rich in dissolved organic material (DOM) throughout the year. AAO, PH, and N uptake rates measured in 1999 and 2000 were not limited to particular size fractions measured, or to auto- or heterotrophic groups of organisms. At a station near the turbidity …

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Sources Of Sediment Found In Sea Ice From The Western Arctic Ocean, New Insights Into Processes Of Entrainment And Drift Patterns, Dennis A. Darby Jan 2003

Sources Of Sediment Found In Sea Ice From The Western Arctic Ocean, New Insights Into Processes Of Entrainment And Drift Patterns, Dennis A. Darby

OES Faculty Publications

The geochemical fingerprint of entrained Fe oxide mineral grains in Arctic Ocean sea ice is used to determine precise sources of this sediment. This approach substantiates the importance of the Laptev Sea as a source of sea ice and even the presence of Russian ice in the Beaufort Sea off Alaska. Fe oxide grains from the Laptev Sea were found in floes in the Beaufort Sea, Chukchi Borderland, and central Arctic Ocean, demonstrating the importance of sea ice in distributing itself throughout the Arctic Ocean and the potential of transporting sediment from Russian rivers to North American shelves. Banks Island …

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The Variability Of Currents In The Yucatan Channel: Analysis Of Results From A Numerical Ocean Model, Tal Ezer, Lie-Yauw Oey, Hyun-Chul Lee, Wilton Sturges Jan 2003

The Variability Of Currents In The Yucatan Channel: Analysis Of Results From A Numerical Ocean Model, Tal Ezer, Lie-Yauw Oey, Hyun-Chul Lee, Wilton Sturges

CCPO Publications

The flow through the Yucatan Channel and into the Gulf of Mexico is a major component of the Gulf Stream and the subtropical gyre circulation. Surprisingly, however, little is known about the forcing and physical parameters that effect the current structures in the Channel. This paper attempts to improve our understanding of the flow through the Channel with a detailed analysis of the currents obtained from a primitive-equation model that includes the Gulf and the entire Caribbean Sea and forced by 6-hourly wind from ECMWF. The analysis includes two parts: First, the overall statistics of the model results, including the …

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