Oceanography Commons^™

A Tribute To Peter George Brewer In Celebration Of His 65th Birthday, George T. F. Wong, Robert F. Anderson, Michael P. Bacon, Hein J. W. De Baar, James W. Murray, Mary I. Scranton

OES Faculty Publications

Peter George Brewer is an ocean chemist of the rare breed that can cross back and forth over the divide between being a front-line research scientist and being a research executive. As if that is not remarkable enough, in the process, he has also demonstrated sustained growth in the depth, breadth, and diversity of his scientific endeavors. Some of his formidable contributions to ocean chemistry have already been highlighted in a profile of him as a major mover and shaker in the field (Irion, 2001). Here, we provide additional glimpses of him from the perspective of a group of individuals …

Forcing And Dynamics Of Seafloor-Water Column Exchange On A Broad Continental Shelf, William B. Savidge, Ann Gargett, Richard A. Jahnke, James R. Nelson, Dana K. Savidge, R. Timothy Short, George Voulgaris

OES Faculty Publications

Relict sediments of elevated permeability characterize the majority of continental shelves globally (Emery, 1968). In these settings, interactions between benthic boundary layer (BBL) flows and seabed topography generate pressure fluctuations that drive advective and dispersive porewater transport, dramatically increasing the magnitude and variability of porewater solute and particulate exchange across the sediment-water interface (Huettel et al., 1996; Huettel and Rusch, 2000). On broad shallow shelves with a relatively large area-to-volume ratio, the seafloor’s role is magnified. Energetic events may reorganize bedforms across a significant fraction of the shelf, leading to altered exchange dynamics that may persist long after the organizing …

Arctic Perennial Ice Cover Over The Last 14 Million Years, Dennis A. Darby

OES Faculty Publications

Knowledge of the long-term history of the perennial ice is an important issue that has eluded study because the Cenozoic core material needed has been unavailable until the recent Arctic Coring Expedition (ACEX). Detrital Fe oxide mineral grains analyzed by microprobe from the last 14 Ma (164 m) of the ACEX composite core on the Lomonosov Ridge were matched to circum-Arctic sources with the same mineral and 12-element composition. These precise source determinations and estimates of drift rates were used to determine that these sand grains could not be rafted to the ACEX core site in less than a year. …

Impacts Of Chromophoric Dissolved Organic Material On Surface Ocean Heating In The Chukchi Sea, Victoria J. Hill

OES Faculty Publications

Recent observations show visible light attenuation in the Arctic Ocean to be greater than previously assumed. High attenuation observed during the period prior to ice melt and increased phytoplankton production, was attributed primarily to the high levels of absorption by chromophoric dissolved organic material ( CDOM) present in these waters. Preliminary evidence suggests this material is produced by ice algae in the early spring. Optical data from the Chukchi shelf system collected in the spring and summer of 2002, were used to model energy absorption in the mixed layer by both dissolved and particulate material. In the spring, absorption by …

Food Limitation In Larval Fish: Ontogenetic Variation In Feeding Scope And Its Potential Effect On Survival, Alexander B. Bochdansky, Peter Grønkjær, Pierre Pepin, William C. Leggett

OES Faculty Publications

We used the radiated shanny Ulvaria subbifurcataas a model species to explore the relative gut fullness from hatch to metamorphosis of wild larvae, and compared these values with those of laboratory-reared larvae fed at maximum rates. Ingestion rates of most wild larvae were above starvation levels but below the maximum feeding levels of laboratory-reared larvae. Twenty-six percent of freshly-hatched wild larvae and 11% of large, pre-settlement wild larvae had insufficient food in their stomach to satisfy metabolic requirements. These results, taken on their own, are consistent with the much hypothesized increased foraging performance and survival of larger larvae relative …

Ship Ballast Tanks: How Microbes Travel The World, Fred C. Dobbs

OES Faculty Publications

As the international shipping fleet travels the oceans, it carries with it hidden cargoes of microbes. Fred C. Dobbs explores the hazards posed and what can be done to counteract them.

Naturally Present Fatty Acids As Internal Calibrants For Fourier Transform Mass Spectra Of Dissolved Organic Matter, Rachel L. Sleighter, Georgina A. Mckee, Zhanfei Liu, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

The analysis of dissolved organic matter ( DOM) by Fourier transform ion cyclotron resonance mass spectrometry ( FTICR- MS) has gained wide interest recently, driven primarily by its ultrahigh resolving power and mass accuracy. Accurate calibration of mass spectra is a key step to successfully decipher the DOM components. We propose a simple and accurate method to internally calibrate the peaks in the complex spectra without the need to add a calibrant. Mass spectra of DOM samples from the Dismal Swamp, Virginia, and the lower Chesapeake Bay display the presence of naturally occurring fatty acids which can be readily recognized …

Determination Of Photochemically Produced Carbon Dioxide In Seawater, Emily M. White, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

An analytical system was developed to determine photochemically produced carbon dioxide in marine waters. Our system was designed to measure low levels of carbon dioxide by maintaining a closed system to prevent atmospheric contamination during sample preparation, irradiation, and analysis. To detect low levels of photoproduced carbon dioxide in seawater, background dissolved inorganic carbon (DIC) was removed before irradiation. To strip out DIC, samples were acidified to pH 3.0 (converting DIC to carbon dioxide) and bubbled with low carbon dioxide air. The pH was then readjusted back to the original value, and the resulting low-DIC seawater samples were transferred pneumatically …

A Modelling Study Of Developmental Stage And Environmental Variability Effects On Copepod Foraging, Jerry D. Wiggert, Eileen E. Hofmann, Gustav-Adolf Paffenhöfer

CCPO Publications

We used a stochastic Lagrangian model to study how behaviour contributes to copepod grazing success. The model simulates distinct foraging behaviours of Clausocalanus furcatus, Paracalanus aculeatus, and Oithona plumifera. Three sets of simulations were performed to investigate the effects of (a) prey-size preference; (b) variation in prey-size spectra; and (c) turbulence intensity on these species’ grazing rates. The size preference simulations demonstrate that, compared with copepodites, mature females have cell ingestion rates that are an order of magnitude lower, while carbon uptake is reduced by 35%. A prey spectrum that is skewed towards cells ,<6 >μm promotes copepodite …

Otolith Chemistry Indicates Population Structuring By The Antarctic Circumpolar Current, Julian R. Ashford, Cynthia M. Jones, Eileen E. Hofmann, Inigo Everson, Carlos A. Moreno, Guy Duhamel, Richard Williams

CCPO Publications

Large-scale transport of seawater in ocean currents may generate spatially complex population structure through the advection of life stages of marine fish species. To test this, we compared the chemistry of otolith nuclei from Patagonian toothfish (Dissostichus eleginoides), presently managed as spatially discrete Populations corresponding to fishing management areas along the Antarctic Circumpolar Current (ACC), which transports water eastward around the Southern Ocean. The chemistry of otolith nuclei, laid down during early life, differed significantly between fishing areas Off South America and the Antarctic and between some Antarctic areas. However, we found significant discrepancies from expectation for a …

Mesoamerican Reef Spawning Aggregations Help Maintain Fish Population: A Review Of Connectivity Research And Priorities For Science Management, W. Heyman, W. B. Kjerfve, T. Ezer

CCPO Publications

The life history of most marine organisms includes an obligate period of pelagic larval dispersal. Migration to spawning areas and pelagic dispersal is often well beyond the home range of these organisms. Designing marine protected areas to include a broad range of taxa and their various dispersal patterns is an important and daunting challenge. This paper addresses the issue of connectivity for one set of species in a limited geographic area. We focus on transient spawning reef fish within the Mesoamerican Reef and their connectivity. We divide our scientific review into four sections as follows: (1) ecological characterization of transient …

Quantifying Vertical Mixing In Estuaries, W. Rockwell Geyer, Malcolm E. Scully, David K. Ralston

CCPO Publications

Estuarine turbulence is notable in that both the dissipation rate and the buoyancy frequency extend to much higher values than in other natural environments. The high dissipation rates lead to a distinct inertial subrange in the velocity and scalar spectra, which can be exploited for quantifying the turbulence quantities. However, high buoyancy frequencies lead to small Ozmidov scales, which require high sampling rates and small spatial aperture to resolve the turbulent fluxes. A set of observations in a highly stratified estuary demonstrate the effectiveness of a vessel-mounted turbulence array for resolving turbulent processes, and for relating the turbulence to the …

Transverse Structure Of Wind-Driven Flow At The Entrance To An Estuary: Nansemond River, Diego A. Narváez, Arnoldo Valle-Levinson

CCPO Publications

Observations of current velocity profiles were combined with an analytical solution to study the transverse partition of the wind-driven flow in an estuary, the Nansemond River, which is a tributary of the James River in the Chesapeake Bay. Observations spanned two periods of nearly 3 months in autumn-winter of 2003-2004 and spring-summer 2004. The wind-driven circulation consisted of downwind flow over the shoal and upwind flow in the channel at the entrance to the estuary. This pattern developed mainly with landward winds and provided observational evidence that sustains analytical and numerical model results. The transverse structure of the flow showed …

Absorption Spectral Slopes And Slope Ratios As Indicators Of Molecular Weight, Source, And Photobleaching Of Chromophoric Dissolved Organic Matter, John R. Helms, Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

A new approach for parameterizing dissolved organic matter ( DOM) ultraviolet-visible absorption spectra is presented. Two distinct spectral slope regions ( 275-295 nm and 350-400 nm) within log-transformed absorption spectra were used to compare DOM from contrasting water types, ranging from wetlands (Great Dismal Swamp and Suwannee River) to photobleached oceanic water ( Atlantic Ocean). On the basis of DOM size-fractionation studies ( ultrafiltration and gel filtration chromatography), the slope of the 275-295- nm region and the ratio of these slopes (S_R; 275-295- nm slope : 350-400- nm slope) were related to DOM molecular weight ( MW) and …

Salt Fluxes At The Chesapeake Bay Entrance, Ruth Lane

OES Theses and Dissertations

Underway measurements of salinity and flow profiles were used to compute salt fluxes at the mouth of the Chesapeake Bay in spring and summer. Waters were sampled along a cross-bay transect over four tidal cycles in 1997: at the end of April, during neap tides, and in mid-July, during spring tides. Data were interpolated onto a uniform grid along the transect area. A least squares regression with semidiurnal and diurnal harmonics was fit on both salinity and flow at each point of the grid to separate tidal from non-tidal influences. The results of the least squares fit were used to …

Limb Regeneration After Multiple Autotomy And Coxae Removal In The Blue Crab Callinectes Sapidus, Jennifer Ambler

OES Theses and Dissertations

This study investigated limb regeneration in the juvenile blue crab, Callinectes sapidus, specifically the role of the coxa and pedal nerve innervation of the regenerative limb bud over time. The coxa is a leg segment that has been defined as the source of positional, cellular, and neuronal information needed for limb regeneration in brachyuran crabs. This study indicates that removal of coxae under regenerative and non-regenerative conditions did not deter limb regeneration. The coxa is not the exclusive location of limb regenerative information since limbs re-grew with normal positional and functional arrangement in 86% of crabs showing regeneration at removal …

Annual And Interannual Variability In The Wind Field And The Hydrography Along The Seward Line In The Northern Gulf Of Alaska, Isaac Schroeder

OES Theses and Dissertations

The Northeast Pacific GLOBEC (GLOBal ocean Ecosystems dynamics) program (October 1997 to December 2004) collected hydrographic data along the Seward Line that stretches from the inner shelf (GAM 59.8°N, 149.5°W) and extends over 200 km beyond the continental slope (GAK13 58.1°N, 147.8°W). The complexity of the interannual hydrographic variability in this area stems from the interacting influences of local forcing such as winds, coastal freshwater discharge, eddies, fronts and remote forcing like El Niño-Southern Oscillation. Until now, the influence of winds on the system has been calculated using coarse resolution upwelling index data or spatially sparse buoy data. The coarse …

Mixed Layer Dynamics Along The Seward Line In The Northern Gulf Of Alaska, Nandita Sarkar

OES Theses and Dissertations

The northern Gulf of Alaska marine ecosystem is very productive with a "nutrient paradox". Primary producers require light and nutrients for photosynthesis. A primary source of nutrients is the deep ocean, while light is available in a relatively shallow layer in the upper ocean. In most productive parts of the world oceans, nutrients are brought to surface waters by upwelling. However, in the northern Gulf of Alaska, the winds are generally downwelling inducing and the mechanism(s) by which nutrients are brought to the euphotic zone are not known. One mechanism that might bring nutrients into the euphotic zone is the …

The Sensitivity Of The Southwest Monsoon Phytoplankton Bloom To Variations In Aeolian Iron Deposition Over The Arabian Sea, Jerry D. Wiggert, Raghu G. Murtugudde

CCPO Publications

[1] A coupled, 3-D biophysical ocean general circulation model is used to investigate how aeolian iron deposition affects the Arabian Sea ecosystem. Two separate aeolian iron deposition fields, derived from the GISS and GOCART atmospheric transport models, have been applied as surface boundary conditions. The model results exhibit widespread biogeochemical sensitivity to the choice of deposition field. With GOCART deposition, SW Monsoon phytoplankton blooms in the western and central Arabian Sea are enhanced and exhibit greater realism. The central Arabian Sea bloom is supported by supplemental input of horizontally advected iron from a pool that undergoes a yearlong progression that …

The Observation, Modeling, And Retrieval Of Bio-Optical Properties For Coastal Waters Of The Southern Chesapeake Bay, Xiaoju Pan

OES Theses and Dissertations

The primary purpose of this study was to develop an inverse method to retrieve the inherent optical properties (IOPs) and biogeochemical parameters (e.g. chlorophyll a concentration and salinity) appropriate to monitor the water quality and biogeochemical processes from remote sensing of the coastal waters in the southern Chesapeake Bay and coastal Mid-Atlantic Bight region (MAB) dominated by Case 2 waters. For this purpose, knowledge of the relationship between remote sensing reflectance (R_rs) and IOPs and the effect from bottom reflectance on R_rs, is required.

A substantial investigation of IOPs has been conducted for the coastal …

Interactions Between Phytoplankton And Bacteria In The Uptake Of Organic Compounds, Andrea Michel Rocha

OES Theses and Dissertations

The most common methods for estimating bacterial productivity are [³H]-leucine and [³H]-thymidine incorporation. Uptake of these compounds has been attributed primarily to bacteria; however, because dissolved organic nitrogen may be an important N source for some phytoplankton, the use of these compounds to estimate bacterial productivity needs to be reexamined. In order to ascertain whether phytoplankton could compete with bacteria on relevant timescales and thereby bias bacterial productivity estimates in estuaries, I examined the ability of cultured phytoplankton and size-fractionated natural populations to take up leucine and thymidine in systems seasonally dominated by phytoplankton mixotrophs. In …

Response Of Eelgrass Zostera Marina To Co2 Enrichment: Possible Impacts Of Climate Change And Potential For Remediation Of Coastal Habitats, Sherry L. Palacios, Richard C. Zimmerman

OES Faculty Publications

Projected increases in dissolved aqueous concentrations of carbon dioxide [CO_2(aq)] may have significant impacts on photosynthesis Of CO₂-limited organisms such as seagrasses. Short-term CO_2(aq) enrichment increases photosynthetic rates and reduces light requirements for growth and survival of individual eelgrass Zostera marina L. shoots growing in the laboratory under artificial light regimes for at least 45 d. This study examined the effects of long-term CO_2(aq) enrichment on the performance of eelgrass growing under natural light-replete (33% surface irradiance) and light-limited (5% surface irradiance) conditions for a period of 1 yr. Eelgrass shoots were grown at …

Simulations Of Phytoplankton Species And Carbon Production In The Equatorial Pacific Ocean 1. Model Configuration And Ecosystem Dynamics, Baris Salihoglu, Eileen E. Hofmann

OES Faculty Publications

The primary objective of this research is to investigate phytoplankton community response to variations in physical forcing and biological processes in the Cold Tongue region of the equatorial Pacific Ocean at 0N, 140W. This research objective was addressed using a one-dimensional multicomponent lower trophic level ecosystem model that includes detailed algal physiology, such as spectrally-dependent photosynthetic processes and iron limitation on algal growth. The ecosystem model is forced by a one-year (1992) time series of spectrally-dependent light, temperature, and water column mixing obtained from a Tropical Atmosphere-Ocean (TAO) Array mooring. Autotrophic growth is represented by five algal groups, which have …

Co2 Control Of Trichodesmium N-2 Fixation, Photosynthesis, Growth Rates, And Elemental Ratios: Implications For Past, Present, And Future Ocean Biogeochemistry, D. A. Hutchins, F.-X. Fu, Y. Zhang, M. E. Warner, Y. Feng, K. Portune, P. W. Bernhardt, M. R. Mulholland

OES Faculty Publications

Diazotrophic marine cyanobacteria in the genus Trichodesmium contribute a large fraction of the new nitrogen entering the oligotrophic oceans, but little is known about how they respond to shifts in global change variables such as carbon dioxide (CO₂) and temperature. We compared Trichodesmium dinitrogen (N₂) and CO₂ fixation rates during steady-state growth under past, current, and future CO₂ scenarios, and at two relevant temperatures. At projected CO₂ levels of year 2100 (76 Pa, 750 ppm), N₂ fixation rates of Pacific and Atlantic isolates increased 35-100%, and CO₂ fixation rates increased 15-128% …

Otolith Chemistry Reflects Frontal Systems In The Antarctic Circumpolar Current, J. R. Ashford, A. I. Arkhipkin, C. M. Jones

OES Faculty Publications

Pronounced environmental trends across fronts suggest that the otolith chemistry of oceanic fish can resolve zones on either side, promoting application to population questions at similar spatial scales. Trace and minor elements laid down immediately prior to capture - along the edges of otoliths from Patagonian toothfish Dissostichus eleginoides - discriminated frontal zones in the Antarctic Circumpolar Current in the Southwestern Atlantic Ocean. Mean values differentiated sampling areas by up to 2.6 standard deviations, suggesting: (1) otolith Mg/Ca enrichment related to fish activity around the Burdwood Bank; (2) Mn/Ca enrichment associated with South America; (3) Sr/Ca linked to the presence …

Impact Of Anthropogenic Combustion Emissions On The Fractional Solubility Of Aeroosol Iron: Evidence From The Sargasso Sea, Peter N. Sedwick, Edward R. Sholkovitz, Thomas M. Church

OES Faculty Publications

We report empirical estimates of the fractional solubility of aerosol iron over the Sargasso Sea during periods characterized by high concentrations of Saharan dust (summer 2003) and by low concentrations of aerosols in North American/maritime North Atlantic air masses (spring 2004 and early summer 2004). We observed a strong inverse relationship between the operational solubility of aerosol iron (defined using a flow-through deionized-water leaching protocol) and the total concentration of aerosol iron, whereby the operational solubility of aerosol iron was elevated when total aerosol iron loadings were low. This relationship is consistent with source-dependent differences in the solubility characteristics of …

Grazing Impacts Of Diverse Zooplankton Taxa On Thin Layers, Alexander Bochdansky

OES Faculty Publications

The US Navy needs to know how distributions and abundances of light-scattering and sound-scattering organisms in the ocean vary in space and time, particularly in the vertical dimension. Recent field observations have shown that many biological properties may vary substantially over small e.g. centimeter scales, commonly referred to as thin layers e.g. Cowles et al. 1998, 1999, Hanson Donaghay 1998, Holliday et al. 1999, Dekshenieks et al. 2001, Alldredge et al. 2002, Rines et al. 2002. Our previous ONR-funded research has allowed us to begin to understand how zooplankton interact with thin layers and how they can take advantage of …

Application Of Maldis-Ms To Identification Of Phytoplankton In Ballast Water, Dana Woodruff, Karen L. Wahl, Nancy B. Valentine, Fred Dobbs

OES Faculty Publications

Non-native invasive species are increasingly evident in marine and estuarine environments, largely because of the intake and release of ballast water from sea vessels. Innovative methods are needed to quickly and accurately detect and speciate non-native and/or harmful phytoplankton in ballast water. Recent advances in ionization techniques such as matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) have allowed detection of intact biomolecules within ballast samples. Statistically-based algorithms are used to discern "fingerprints" of phytoplankton species and to discern individual species from mixtures. MALDI-MS is particularly attractive for field applications because of the speed of analysis, minimal liquids/consumables required, and femtomole (10-15) …

Bottom-Up Forcing And The Decline Of Steller Sea Lions (Eumetopias Jubatus) In Alaska: Assessing The Ocean Climate Hypothesis, Andrew W. Trites, Arthur J. Miller, Michael A. Alexander, Steven J. Bograd, John A. Calder, Antonietta Capotondi, Kenneth O. Coyle, Emanuele Di Lorenzo, Bruce P. Finney, Edward J. Gregr, Chester E. Grosch, Thomas C. Royer

CCPO Publications

Declines of Steller sea lion ( Eumetopias jubatus) populations in the Aleutian Islands and Gulf of Alaska could be a consequence of physical oceanographic changes associated with the 1976–77 climate regime shift. Changes in ocean climate are hypothesized to have affected the quantity, quality, and accessibility of prey, which in turn may have affected the rates of birth and death of sea lions. Recent studies of the spatial and temporal variations in the ocean climate system of the North Pacific support this hypothesis. Ocean climate changes appear to have created adaptive opportunities for various species that are preyed upon …

Simulations Of Phytoplankton Species And Carbon Production In The Equatorial Pacific Ocean 2. Effects Of Physical And Biogeochemical Processes, Baris Salihoglu, Eileen E. Hofmann

CCPO Publications

A one-dimensional multi-component lower trophic level ecosystem model that includes detailed algal physiology is used to investigate the response of phytoplankton community and carbon production and export to variations in physical and biochemical processes in the Cold Tongue region of the equatorial Pacific Ocean at ON, 140W. Results show that high-frequency variability in vertical advection and temperature is an important mechanism driving the carbon export. Filtering out low frequency physical forcing results in a 30% increase in primary production and dominance of high-light adapted Prochlorococcus and autotrophic eukaryotes. Sensitivity studies show that iron availability is the primary control on carbon …