No description available.

No description available.

No description available.

A limited amount of research has been done to investigate the factors influencing algal abundance in large river systems. This study examines light as the primary factor that controls algal abundance in the Upper Mississippi, Missouri and Ohio Rivers. Data were collected for 2004 in conjunction with the Environmental Monitoring Assessment Program- Great River Ecosystems EMAP-GRE project using EPA approved methods. Chlorophyll a concentrations were 34.6 µg•L-1 in the Upper Mississippi, 19.8 µg•L-1 in Missouri River and 9 µg•L-1 in the Ohio River for 2004. Chlorophyll a concentrations were significantly different among the three rivers (p<0.0001) but not between years. Inter-river variation could be loosely correlated with light availability: mean Average Irradiance Dosages, which consider factors that affect light climate (depth, transparency, velocity, surface irradiance), by river corresponded with mean chlorophyll a levels by river. Intra-river variation seemed to be due to both the influence of light and nutrients.

During the Northeastern Gulf of Mexico Chemical and Hydrography study (NEGOM-COH), nine oceanographic cruises were fielded during the spring, summer and fall seasons from November 1997 to August 2000. Surface chlorophyll-? fluorescence, salinity, and temperature data were logged once a minute from the R/V Gyre and subsurface chlorophyll-? fluorescence, salinity, temperature, and nutrients were profiled when the ship stopped to make stations. Each cruise occupied 94-98 stations, partitioned among 11 cross-margin transects of water depths between 10 m to 1000 m. Overall chlorophyll-? abundance within the study area is forced by the amount of freshwater discharge. Seasonal and interannual differences are largely determined by the monthly mean streamflow for the major rivers within the NEGOM area, particularly the Mississippi River. However, an important forcing function for transport of river water to the outer continental shelf and slope is the periodic presence of anticyclonic slope eddies. Especially when these slope eddies were centered south and east of the Mississippi River delta, they entrained and so redistributed low salinity green water to a wider area within the NEGOM region than could be predicted by mean monthly streamflow alone. The mean surface chlorophyll-? concentrations, and in particular the distribution of relatively high surface chlorophyll-? concentrations off-shelf, were strongly dependent upon entrainment of freshwater by these slope eddies, especially during the three summer cruises. Interannual variability in the summertime entrainment of low salinity green water was driven by summer-to-summer differences in sea surface height (SSH) of the slope eddy(s), and in how far they extended on margin. Satellite observations of ocean color showed that freshwater entrainment by anticyclonic eddies persisted for a temporal scale of several weeks each summer. Satellite-derived surface chlorophyll-? concentrations were positively correlated with in situ measurements of surface chlorophyll-?, with greatest agreement between satellite and ship measurements of surface chlorophyll-? at concentrations <1.5 mg/m3. Because subsurface chlorophyll-? concentrations were often elevated at depths greater than the first optical depth, satellite measurements of chlorophyll-? concentration generally underestimated integrated chlorophyll-? standing stocks within the euphotic zone.

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 17, 2010) Includes bibliographical references (p. 32-35)

No description available.

No description available.

Food production systems need to keep pace with the rising global population. Food from aquatic environments comes from both capture fisheries and aquaculture. Industrial fishing pressure has caused a global loss of more than 90% of large predatory fishes and 80% of the world’s fish stocks are reported as fully exploited or overexploited. Global finfish, shellfish and aquatic plant aquaculture has been steadily increasing to meet the global demand for seafood. In British Columbia, aquaculture is primarily marine, with salmon and shellfish accounting for the majority of species cultured. Although shellfish aquaculture accounts for significantly less production and value compared to salmon aquaculture, the amount of foreshore dedicated to farming shellfish is nearly half (44%) the total area utilized by all aquaculture in the Province. Introduced Pacific oysters (Crassostrea gigas) (74%) dominate shellfish aquaculture in British Columbia. Pacific oysters are known to be very efficient generalist filter feeders that can grow faster and larger than native species. Extensive aquaculture is a form of aquaculture, where farmed animals feed exclusively on naturally occurring food in the surrounding water column. The goal of this research was to determine if there was a measureable depletion of phytoplankton around shellfish farms along the west coast of Canada and the United States. Chlorophyll-a, a pigment found within phytoplankton, was used as a proxy for phytoplankton abundance for this study. In field season one, two bays were studied, one exposed to shellfish culture (Westcott Bay) and one not exposed to shellfish culture (Fisherman Bay). The concentration of chlorophyll-a was measured in each bay at three locations at two depths (0.5 and 3 meters) and at two tidal heights (high and low). Chlorophyll-a concentration was found to be related to either depth or tide, with location in a bay showing no difference in either of the bays studied. In addition to water column measurements, 100 Pacific oysters were placed at two locations within Westcott Bay Seafarm to test for local differences in oyster growth. The results from this experiment showed that Pacific oysters grown in the center of a shellfish farm were smaller than oyster grown at the farm’s periphery. Field season two tested for spatial patterns between chlorophyll-a concentration and proximity to a shellfish farm in three different bays (Westcott Bay, Trevenon Bay and Gorge Harbour). A measureable depletion footprint of chlorophyll-a concentration was detected in the two sheltered shallow bays tested (Westcott Bay and Gorge Harbour), whereas no depletion footprint was detected in the exposed, deep bay (Trevenon Bay). Tide height played a significant role in predicating chlorophyll-a concentration in all three of the bays studied. These results suggested that some areas may be more suitable for shellfish culture than others. Taken together, this research demonstrated a measureable gradient of phytoplankton in sheltered shallow bays exposed to shellfish culture with depletion closest to the farm site, as well as greater oyster growth at the periphery of shellfish farms where phytoplankton would be predictably in greater abundance. / Graduate

This thesis describes the design, optimisation and shipboard deployment of a flow injection - chemiluminescence (FI-CL) technique for the determination of iron (Fe) in seawater. Chapter One presents an overview of the marine biogeochemistry of Fe, including its speciation, sources and sinks, abundance and limitation for phytoplankton growth in the Wodd*s oceans. Current analytical methods for the determination of Fe in natural waters are also reviewed. Chapter Two reports the instrumental development of the FI - CL method. Each component is described and its suitability to the flow manifold discussed. Different CL detection systems are evaluated and a charge coupled device used to investigate the spectral profile of the Fe-catalysed luminol reaction. Automation of the FI manifold is also detailed along with acquisition of CL signals. Chapter Three details the optimisation of a FI - CL procedure for the determination of Fe in seawater. Reagent clean-up techniques, blank procedures and a standard addition operating routine are detailed. Fe(III) reduction using sulphite is treated theoretically. Matrix effects are investigated and the synthesis of an 8-hydroxyquinoline resin used for in-line matrix elimination and preconcentration is reported. The optimised method is selective to Fe(II+IIl) in the linear range 0.04-10 nM, with a precision of 3.2% (n=5) for a LO nM standard and a limit of detection (3s) of 40 pM for a load time of 1 min. Chapter Four presents the results of an investigation into the kinetic effect of Fe on luminol CL using the continuous addition of reagent (CAR) technique. Instrumental and chemical parameters are optimised, interferences investigated and the CAR-CL technique compared with alternative flow configurations. In Chapter Five, the application of the F - CL method to the shipboard determination of Fe in the surface North and South Atlantic (SO'^N to 50°S) is presented. Data are reported for samples collected from the upper water column (<200 m) in eight different biogeochemical provinces, which represent coastal, upwelling and oligotrophic regions of the Adbntic Ocean. Total dissolvable iron (unfiltered, TD-Fe) levels range ftom <0.1 to 6.1 nM and indicate that high and spatially variable TD-Fe (>2 nM) concentrations exist in Equatorial and tropical North Atlantic regions influenced by atmospheric deposition from the West African continent. Away from strong input mechanisms, TD-Fe concentrations in the upper water column average 0.6 nM. Input sources are fingerprinted via correlation with other trace metals (Al, Co, Ni), nutrients and hydrography, whilst active biological uptake is shown to be the dominant sink. TD-Fe vertical distributions through the upper mixed layer display strong relationships with chlorophyll a concentrations, and measurements in the deep chlorophyll maximum of the South Atlantic oligotrophic gyre show that, despite elevated nitrate at such depths, Fe concentrations are at a minimum (ca. 0.1 nM) and may be low enough to (co-)limit phytoplankton growth.