Oceanography and Atmospheric Sciences and Meteorology Commons^™

Age And Growth Of Larval And Juvenile Atlantic Croaker, Micropogonias Undulatus, From The Middle Atlantic Bight And Estuarine Waters Of Virginia, Stephen W. Nixon, Cynthia M. Jones

OES Faculty Publications

Sagittal otoliths were used to determine age and growth of 605 larval and juvenile Atlantic croaker, Micropogonias undulatus, collected in the Middle Atlantic Bight and estuarine waters of Virginia. This study is the first to use age-based analysis for young Atlantic croaker collected in this region. A Laird-Gompertz model (r2=0.95) was used to describe the growth of Atlantic croaker up to 65 mm standard length (SL) and 142 days (t): SL((t)) = 2.657 exp (4.656 [1-exp (-0.0081t)]); where SL((t)) = standard length at day t. Spatial and temporal patterns in the size and age of Atlantic croaker showed a …

Response Of Otolith Microchemistry To Environmental Variations Experienced By Larval And Juvenile Atlantic Croaker (Micropogonias Undulatus), Simon R. Thorrold, Cynthia M. Jones, Steven E. Campana

OES Faculty Publications

Minor and trace elements incorporated into otoliths during growth may permanently record environmental conditions experienced by fishes. To determine the validity of this approach, we used laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to assay sectioned otoliths from juvenile Atlantic croaker (Micropogonias undulatus) collected from each of three sites in the Neuse River, North Carolina, and the Elizabeth River, Virginia. Elemental concentrations at the center of the otoliths did not differ between locations, although both Mg : Ca and Ba : Ca were significantly higher at the edge of otoliths from the Neuse River than from the …

Destruction Of Chloropigments In Copepod Guts, A. B. Bochdansky, D. Deibel

OES Faculty Publications

In a recent account regarding the destruction of chloropigments within the guts of copepods, Head & Harris (1996) (H&H) presented valuable data on pigment destruction in copepods. However, in one of their main conclusions, the authors invoked 2 enzyme pools to explain the pattern of pigment destruction: one directly derived from copepods, the other one produced by the ingested algae. If this conclusion is correct, it would have tremendous impact on the interpretation of data collected by the gut pigment technique. Estimating ingestion rates of copepods in the field would be very difficult, if not impossible, if pigment destruction was …

Detection Of Harmful Algal Blooms Using Photopigments And Absorption Signatures: A Case Study Of The Florida Red Tide Dinoflagellate, Gymnodinium Breve, David F. Millie, Oscar M. Schofield, Gary J. Kirkpatrick, Geir Johnson, Patricia A. Tester, Btyan T. Vintard

OES Faculty Publications

The utility of photopigments and absorption signatures to detect and enumerate the red tide dinoflagellate, Gymnodinium breve, was evaluated in laboratory cultures and in natural assemblages. The carotenoid, gyroxanthindiester, was an adequate biomarker for G. breve biomass; water‐column concentrations corresponded with cell standing crops and chlorophyll a concentrations during bloom events in Sarasota Bay, Florida. Unlike other carotenoids, the relative abundance of gyroxanthin‐diester did not change throughout a range of physiological states in culture and the gyroxanthin‐diester: chlorophyll a ratio exhibited little variability in a natural assemblage during bloom senescence. Stepwise discriminant analysis indicated that wavelengths indicative of in vivo …

Regulation Of Algal Blooms In Antarctic Shelf Waters By The Release Of Iron From Melting Sea Ice, Peter N. Sedwick, Giacomo R. Ditullio

OES Faculty Publications

During summer 1995-96, we measured iron in the water column and conducted iron-enrichment bottle-incubation experiments at a station in the central Ross Sea (76°30'S, 170°40'W), first, in the presence of melting sea ice, and 17 days later, in ice-free conditions. We observed a striking temporal change in mixed-layer dissolved iron concentrations at this station, from 0.72-2.3 nM with sea ice present, to 0.16-0.17 nM in ice-free conditions. These changes were accompanied doubling of algal (diatom) biomass. Our incubation experiments suggest that conditions were iron-replete in the presence of sea ice, and iron-deficient in the absence of sea ice. We surmise …

A Modeling Study Of The Effects Of Size- And Depth-Dependent Predation On Larval Survival, Margaret M. Dekshenieks, Eileen E. Hofmann, John M. Klinck, Eric N. Powell

CCPO Publications

The form of the predation pressure experienced by larval stages of marine invertebrates is largely unknown. However, it is believed that the type, timing and rate of larval predation are critical in determining recruitment to adult populations. In this study, a time and depth-dependent model of the growth and behavior of larvae of the Eastern oyster, Crassostrea virginica, was used to investigate the effects of different forms of size-and depth-dependent predation on larval survivorship. The simulated larval survival for a cohort experiencing size-dependent predation showed that the greatest percent of the cohort survived to competent settlement size when the …

Factors Affecting The Recruitment Of Juvenile Caribbean Spiny Lobsters Dwelling In Macroalgae, Mark J. Butler Iv, William F. Herrnkind, John H. Hunt

Biological Sciences Faculty Publications

In south Florida, Caribbean spiny lobsters (Panulirus argus) settle and spend their first few months in macroalgae or seagrass. After a few months, these ''algal-phase'' juveniles emerge from vegetation and, as ''postalgal-phase'' juveniles, seek refuge in crevices, often dwelling in groups. The importance of crevice shelters in determining the abundance of postalgal-phase juvenile spiny lobsters has been studied but we know little about the processes affecting lobster distribution and survival during their cryptic algal-dwelling phase. We found that postlarval supply varied independently of changes in the structure of macroalgal settlement habitat. For this reason, postlarval supply alone can not reliably …

Small-Scale Settlement Patterns Of The Oyster Crassostrea Virginica On A Constructed Intertidal Reef, Ian K. Bartol, Roger Mann

Biological Sciences Faculty Publications

The construction of three-dimensional, intertidal reefs resembling those widely present during colonial times in the Chesapeake Bay, but now absent due to years of overharvesting, may provide a more ecologically advantageous environment for oyster settlement and subsequent survival than present subtidal, two-dimensional habitats. We examined settlement processes on a constructed, 210 x 30 m intertidal reef composed of oyster shell. The reef was destructively and non-destructively sampled weekly throughout the summer and fall at tidal heights ranging from 30 cm above to 90 cm below mean low water (MLW) and at two substrate levels (reef surface and 10 cm below …

Seasonal And Inter-Annual Patterns Of Sediment-Water Nutrient And Oxygen Fluxes In Mobile Bay, Alabama (Usa): Regulating Factors And Ecological Significance., Jean L. Cowan, Jonathan Pennock, Walter R. Boynton

School of Marine Science and Ocean Engineering

Sediment oxygen and nutrient fluxes were measured monthly for 2 yr in Mobile Bay, Alabama, USA. Rates of sediment oxygen consumption (0.1 to 1.25 gO₂ m^-2 d^-1), ammonium flux (-22 to 181 µmol m^-2 h^-1), nitrate flux (-14 to 67 µmol m^-2 h^-1), phosphate flux (-2 to 20.4 µmol m^-2 h^-1), and dissolved silicate flux (-15 to 342 µmol m^-2 h^-1) were moderate to high compared to values for other estuaries. A step-wise regression analysis revealed that dissolved oxygen concentration and temperature in bottom-waters …

Modeling Nutrient And Plankton Processes In The California Coastal Transition Zone: 3. Lagrangian Drifters, J. R. Moisan, Eileen E. Hofmann

CCPO Publications

Two types of numerical Lagrangian drifter experiments were conducted, using a set of increasingly complex and sophisticated models, to investigate the processes associated with the plankton distributions in the California coastal transition zone (CTZ). The first experiment used a one-dimensional (1-D; vertical) time-dependent physical-bio-optical model, which contained a nine-component food web. Vertical velocities, along the track of simulated Lagrangian drifters, derived from a three-dimensional (3-D), primitive equation circulation model developed to simulate the flow observed within the CTZ; were used to parameterize the upwelling and downwelling processes. The second experiment used 880 simulated Lagrangian drifters from a 3-D primitive equation …

Modeling Nutrient And Plankton Processes In The California Coastal Transition Zone: 1. A Time- And Depth-Dependent Model, J. R. Moisan, Eileen E. Hofmann

CCPO Publications

A time- and depth-dependent, physical-bio-optical model was developed for the California coastal transition zone (CTZ) with the overall objective of understanding and quantifying the processes that contribute to the vertical and temporal development of nutrient and plankton distributions in the CTZ. The model food web components included silicate, nitrate, ammonium, two phytoplankton size fractions, copepods, doliolids, euphausiids, and a detritus pool. The wavelength-dependent subsurface irradiance field was attenuated by sea water and phytoplankton pigments. The one-dimensional (1-D) model adequately simulated the development and maintenance of a subsurface chlorophyll maximum in different regions within the CTZ. An analysis of the individual …

Modeling Nutrient And Plankton Processes In The California Coastal Transition Zone: 2. A Three-Dimensional Physical-Bio-Optical Model, J. R. Moisan, Eileen E. Hofmann, D. B. Haidvogel

CCPO Publications

A three-dimensional (3-D) primitive equation model, developed to simulate the circulation features (filaments) observed in the California coastal transition zone (CTZ), was coupled to a nine-component food web model and a bio-optical model. The simulated flow fields from a 3-D primitive equation model are used to advect the constituents of the food web model, which include silicate, nitrate, ammonium, two phytoplankton size fractions, copepods, doliolids, euphausiids, and a detritus pool. The bio-optical model simulates the wavelength-dependent attenuation of the subsurface irradiance field. The overall objective of this modeling study was to understand and quantify the processes that contribute to the …

Nutrients And Chlorophyll At The Shelf Break Off The Southeastern United States During The Genesis Of Atlantic Lows Experiment: Winter 1986, L. P. Atkinson, J. L. Miller, T. N. Lee, W. M. Dunstan

CCPO Publications

The outer shelf and upper slope off Charleston, South Carolina, were the site of oceanographic and meteorological measurements during the winter of 1986. The purpose of the study was to test ideas about front formation, heat transport, and stratification during cold air outbreaks. An ancillary part of the study was the observation of nutrients and chlorophyll concentrations. The observations extended across the shelf and sometimes crossed the Gulf Stream front. The results show slightly elevated nitrate concentrations in outer shelf waters (1 - 2 μM NO₃) with chlorophyll concentrations in the 1 - 1.8 μg L^-1 range. …

Effects Of Climate Change On Hypoxia In Coastal Waters: A Doubled Co2 Scenario For The Northern Gulf Of Mexico, Dubravko Justic, Nancy N. Rabalais, R. Eugene Turner

Faculty Publications

Projections of general circulation models suggest that freshwater discharge from the Mississippi River to the coastal ocean will increase 20% if atmospheric CO2 concentration doubles. This result is likely to affect water column stability, surface productivity, and global oxygen cycling in the northern Gulf of Mexico, which is the site of the largest (up to 16,500 km2) and most severe hypoxic zone (liter‒1) in the western Atlantic Ocean. We use a coupled physical-biological two-box model to investigate potential effects of climate change on seasonal oxygen cycling and hypoxia in river-dominated coastal waters. The model was developed and calibrated using comprehensive …

Nutrient Changes In The Mississippi River And System Responses On The Adjacent Continental Shelf, Nancy N. Rabalais, R. Eugene Turner, Dubravko Justic, Quay Dortch, William J. Wiseman, Barun Sen Gupta

Faculty Publications

The Mississippi River system ranks among the world's top 10 rivers in freshwater and sediment inputs to the coastal ocean. The river contributes 90% of the freshwater loading to the Gulf of Mexico, and terminates amidst one of the United States' most productive fisheries regions and the location of the largest zone of hypoxia, in the western Atlantic Ocean. Significant increases in riverine nutrient concentrations and loadings of nitrate and phosphorus and decreases in silicate have occurred this century, and have accelerated since 1950. Consequently, major alterations have occurred in the probable nutrient limitation and overall stoichiometric nutrient balance in …

Observation Of Shelfwater Overrunning The Southern Slope Sea, Ajoy Kumar

OES Theses and Dissertations

Analyses of two years (1992 and 1993) of high resolution (1.47 km²) sea surface temperature satellite images of the southern Mid-Atlantic Bight (MAB), showed that unusually extensive overhang of shelf water occurs episodically, and coherently over along shelf distances of several hundred kilometers. These episodes are dubbed overrunning of the Slope Sea by shelf water. The overrunning volume has a "face" and a "back" (southern and northern limit). It transports substantial quantities of shelf water southward, and does not retreat onto the shelf, but eventually joins the western edge of the Gulf Stream in the vicinity of Chesapeake …

Recruitment Of Blue Crab, Callinectes Sapidus, Postlarvae To The Back-Barrier Lagoons Of Virginia's Eastern Shore, Robert D. Brumbaugh

OES Theses and Dissertations

Most research on the early life history of the blue crab, Callinectes sapidus, has been conducted in large partially stratified estuaries such as the Chesapeake Bay. In contrast, little is known about the recruitment dynamics or habitat requirements of blue crab postlarvae (megalopae) in shallow well-mixed lagoonal systems that make up a considerable part of the species' range. In Virginia's coastal lagoons, planktonic blue crab megalopae are most abundant at night on flooding tides, and are not abundant during the daytime or on ebbing tides. This appears to enhance retention within the lagoons, despite the short residence time of water …

The Effects Of Environmental Variability On The Population Structure Of The Eastern Oyster (Crassostrea Virginica): A Modeling Study, Margaret Mcmanus Dekshenieks

OES Theses and Dissertations

Three models were coupled to investigate the effects of changes in environmental conditions on the population structure of the Eastern oyster, Crassostrea virginica. The first model, a time-dependent model of the oyster population as described in Powell et al. (1992) and Hofmann et al. (1992, 1995), tracks the distribution, development, spawning, and mortality of sessile oyster populations. The post-settlement model incorporates mortality through parasitism, predation, food depletion and extremes in environmental conditions. The post-settlement model supplies the initial abundance of larvae spawned into the water column, and in turn is the recipient of cohorts of spawn which survive through metamorphosis. …

Seasonal And Mesoscale Variability In The Distribution Of Antarctic Krill, Euphausia Superba, West Of The Antarctic Peninsula, Cathy Meyer Lascara

OES Theses and Dissertations

Observations collected between November 1991 and September 1993 during four multidisciplinary cruises were analyzed to provide a description of seasonal and mesoscale variability in the distribution and abundance of Antarctic krill, Euphausia superba, within continental shelf waters west of the Antarctic Peninsula and to investigate possible relationships between variability in krill distributions and variability in selected environmental parameters. Acoustic measurements of krill were made each season at designated locations to estimate the abundance of krill, in terms of vertically-integrated krill biomass and the number of aggregations, characterize the depth distribution of krill, and provide a quantitative description of the size, …

A One-Dimensional Model For Storm Breaching Of Barrier Islands, Cheol Shik Shin

Civil & Environmental Engineering Theses & Dissertations

A set of numerical models is developed for simulating the four stages of barrier breaching characterized by one horizontal spatial dimension.

The SBEACH model is employed for the first stage of dune/beach erosion. The Lax-Wendroff two-step explicit scheme for Stage II is developed to simulate initiation of ocean flood propagation on initially dry barrier islands and the method of characteristics (MOC), is employed to compute additional boundary data. The development of the Preissmann implicit scheme for water motion and a forward time centered space explicit scheme for sediment motion in Stages III and IV provide a tool to study the …

Democratization Of Ocean Research: A Model For The Post-Cold War Era?, Maureen A. Kennelly

Marine Affairs Theses and Major Papers

Since the end of World War II the field of oceanography has enjoyed the generous patronage of the federal government under the "social contract" model for the support of science. This model is based on the principles of freedom and autonomy for scientists, insulation of science from politics, and emphasis on basic research. With the recent ending of the Cold War, the simple science policies of the post-World War II years are being philosophically and politically challenged and the rationales for the support of science are being questioned. National security is no longer the driving force behind science funding in …

Effect Of Light/Dark Transition On Carbon Translocation In Eelgrass Zostera Marina Seedlings, Richard C. Zimmerman, Randall S. Alberte

OES Faculty Publications

Carbon translocation in the marine macrophyte Zostera marina L. (eelgrass) was investigated to elucidate the impact of light/dark transitions on sucrose partitioning between roots and shoots. After exposure of leaves to C-14-bicarbonate, the level of C-14-labelled photoassimilates increased monotonically in both leaves and fully aerobic roots of plants maintained in the light. Accumulation of C-14 in roots and leaves ceased abruptly when plants were transferred to darkness that induced root anaerobiosis even though C-14 levels remained high in the dark-exposed leaves. Thus, translocation of C-14 photoassimilates from shoots to roots was inhibited when roots became anoxic. Anoxia induced by light …

A Coupled, Non-Linear, Steady State Model For Early Diagenetic Processes In Pelagic Sediments, Surya P. Dhakar, David J. Burdige

OES Faculty Publications

A steady state, coupled, non-linear model has been developed for early diagenetic processes in pelagic and hemi-pelagic marine sediments. Model results show that the occurrence of oxic and sub-oxic diagenetic processes is significantly affected by variations in parameters such as the sedimentation rate, bioturbation coefficient, sediment porosity, and organic matter flux to the sediments. Increases in the sedimentation rate or the bioturbation coefficient increase organic matter oxidation by sub-oxic processes, whereas an increase in sediment porosity decreases organic matter oxidation by sub-oxic processes. Sediment data from three contrasting MANOP sites are fit reasonably well with the model. The resulting best-fit …

Biogenic Matter Diagenesis On The Sea Floor: A Comparison Between Two Continental Margin Transects, William M. Berelson, Jim Mcmanus, Kenneth H. Coale, Kenneth S. Johnson, Tammy Kilgore, David J. Burdige, Cynthia Pilskaln

OES Faculty Publications

Benthic chamber measurements of the reactants and products involved with biogenic matter diagenesis (oxygen, ammonium, nitrate, silicate, phosphate, TCO₂, alkalinity) were used to define fluxes of these solutes into and out of the sediments off southern and central California. Onshore to offshore transects indicate many similarities in benthic fluxes between these regions. The pattern of benthic organic carbon oxidation as a function of water depth, combined with published sediment trap records, suggest that the supply of organic carbon from vertical rain can just meet the sedimentary carbon oxidation + burial demand for the central California region between the …

The Implications Of Turbidite-Driven Redox Changes In Sediments Of The Iberia Abyssal Plain, Timothy J. Shaw, P. A. Meyers

Faculty Publications

No abstract provided.

Organic Matter Accumulation, Sulfate Reduction, And Methanogenesis In Pliocene–Pleistocene Turbidites On The Iberia Abyssal Plain, P. A. Meyers, Timothy J. Shaw

Faculty Publications

No abstract provided.

Modeling The Vertical Distribution Of Oyster Larvae In Response To Environmental Conditions, Margaret M. Dekshenieks, Eileen E. Hofmann, John M. Klinck, Eric N. Powell

CCPO Publications

A size-structured, time and vertically-dependent model was used to investigate the effects of water column structure on the distribution of larvae of the oyster Crassostrea virginica. Formulations used to model larval growth and behavior are based upon laboratory studies. Simulated vertical larval distributions obtained for conditions representative of a well-mixed, partially stratified and strongly stratified water column illustrate the effect that salinity and temperature gradients have on moderating larval swimming and hence on larvae vertical location. For well-mixed conditions, smaller larvae are dispersed throughout most of the water column. For strongly stratified conditions, the smaller-sized larvae cluster within the …

Circulation Near Submarine Canyons: A Modeling Study, John M. Klinck

CCPO Publications

Circulation near a submarine canyon is analyzed with a numerical model. Previous theoretical work indicated that stratification controlled the interaction of coastal flow with canyons, specifically, the ratio of canyon width to the internal radius of deformation. A wide canyon was thought to merely steer the flow, while a narrow canyon would create substantial cross-shelf exchange. Four cases are analyzed considering two directions of alongshore flow and two choices of initial stratification. The weakly stratified case has an internal radius about equal to the canyon width, while the strongly stratified case has one about 3 times the canyon width. The …

The Effect Of Arctic River Hydrological Cycles On Arctic Ocean Circulation, Peter Becker

OES Theses and Dissertations

Understanding Arctic Ocean circulation may be critical to fully understanding the global oceanic salt and heat cycles and their response to climate variability. This thesis examines how one important aspect of Arctic Ocean circulation, the effect of freshwater inflow, may contribute to the variability of these cycles. The multiple roles that freshwater runoff performs in the Arctic Ocean include: (1) the formation of shelf and basin scale density currents; (2) maintenance of the strong density stratification; (3) control of the thickness and strength of the ice pack; and (4) control of deep convection. Sources and sinks of freshwater in the …

On The Interpentadal Variability Of The North Atlantic Ocean: Model Simulated Changes In Transport, Meridional Heat Flux And Coastal Sea Level Between 1955-1959 And 1970-1974, Tal Ezer, George L. Mellor, Richard J. Greatbatch

CCPO Publications

Previous studies by Greatbatch et al. (1991) indicate significant changes in the North Atlantic thermohaline structure and circulation between the pentads 1955–1959 and 1970–1974, using data analyzed by Levitus (1989a,b,c) and a simple diagnostic model by Mellor et al. (1982). In this paper these changes are modeled using a three-dimensional, free surface, coastal ocean model. Diagnostic and short-term prognostic calculations are used to infer the dynamically adjusted fields corresponding to the observed hydrographic and wind stress climatology of each pentad. While the results agree with earlier studies indicating that the Gulf Stream was considerably weaker (by about 30 Sv) during …