Life Sciences Commons^™

Nitrate Reductase Activity, Nitrate Uptake And Iodine Speciation In The Marine Environment, Chin-Chang Hung

OES Theses and Dissertations

The present method for the determination of new production (NP) by measuring the uptake of added ¹⁵NO₃^– suffers from a number of limitations. In an attempt to improve this situation, this research examined the possibility of estimating ¹⁵NO₃– uptake by measuring the activity of nitrate reductase (NRA). In addition, because it has long been suspected that the biological reduction of IO₃^– to I^– may be mediated by nitrate reductase (NR), this research investigated the ability of NR to catalyze the reduction of iodate to iodide.

An improved method for the determination …

Production Of Copper-Complexing Ligands In Response To Elevated Concentrations Of Copper In Marine Synechococcus Spp., Arunsri Chatkaeomorakot Brown

Theses and Dissertations in Biomedical Sciences

Synechococcus spp. (marine cyanobacteria) are extremely sensitive to copper toxicity and can produce high-affinity ligands of unknown structure which form complexes with free cupric ion. These ligands may contribute to the biological control of the levels of free cupric ions in surface seawater. Synechococcus spp. are known to produce metallothioneins (MT) in response to cadmium and zinc stress. In the present study the hypothesis that marine Synechococcus produce MT in response to copper was tested. Three marine Synechococcus spp. i.e., PCC 7001, PCC 73109, and PCC 7003, were exposed to different concentrations of CUSO 4 for various time periods. Size …

Benthic Community Analysis Of Hog Island Bay, Virginia, David James Lewis

Biological Sciences Theses & Dissertations

The benthic infaunal macroinvertebrate communities of Hog Island Bay of the Virginia Eastern Shore were quantitatively sampled at 30 locations on August 31 and September 1, 1995. The primary objectives of this study were: (1) to characterize the subtidal macroinfaunal benthic communities of Hog Island Bay, (2) to examine relationships between abiotic factors and the macroinfaunal communities and (3) to characterize the environmental condition of the system using the Benthic Index of Biotic Integrity (B-IBI) (Weisburg et al. 1997) and the EMAP Benthic Index for the Virginian Province (Strobel et al. 1995).

The ecological condition of Hog Island Bay appears …

The Cause And Consequence Of Ontogenetic Changes In Social Aggregation In New Zealand Spiny Lobsters, Mark J. Butler Iv, Alistair B. Macdiarmid, John D. Booth

Biological Sciences Faculty Publications

Ontogenetic changes in the behavior, spatial distribution, or habitat use of a species are presumably adaptations to ecological forces that differ in their effect on various life stages. The New Zealand rock lobster Jasus edwardsii is one of several species of spiny lobster that exhibits dramatic ontogenetic shifts in sociality and spatial distribution, and we tested whether such changes are adaptive. We first surveyed several natural populations of J. edwardsii to document size-specific differences in aggregation. To determine if chemical cues discharged by conspecifics promote aggregation of certain ontogenetic stages, we tested the responsiveness of lobsters of 3 ontogenetic stages …

Comparative Study Of Selenium Requirements Of Three Phytoplankton Species: Gymnodinium Catenatum, Alexandrium Minutum (Dinophyta) And Chaetoceros Cf. Tenuissimus (Bacillariophyta, Martina A. Doblin, Susan I. Blackburn, Gustaaf M. Hallegraeff

OES Faculty Publications

This study investigated the selenium (Se) requirements of three phytoplankton species which commonly bloom in southern Australian estuaries. The present study showed that the toxic dinoflagellate Gymnodinium catenatum Graham had an obligate requirement for Se (IV) in culture. After two transfers (~ 4 weeks ≈ 7 generations) in Se-deficient seawater medium, this phytoplankton species exhibited a decline in growth rate (25%) and biomass yield (90%), while complete cessation of cell division occurred under prolonged (8 weeks ≈ 12 generations) Se starvation. Addition of 10^-9-10^-7 M H₂SeO₃ to nutrient-enriched seawater medium resulted in increased G.catenatum …

Modeling The Effects Of Doliolids On The Plankton Community Structure Of The Southeastern Us Continental Shelf, A. G. Edward Haskell, Eileen E. Hofmann, Gustav-Adolf Paffenhofer, Peter G. Verity

CCPO Publications

A model of the lower trophic levels that consists of a system of coupled ordinary differential equations was developed to investigate the time-dependent behavior of doliolid populations associated with upwelling features on the outer southeastern US continental shelf. Model equations describe the interactions of doliolids with two phytoplankton size fractions, five copepod developmental stages and a detrital pool. Additional equations describe nitrate and ammonia. Model dynamics are based primarily upon data obtained from field and laboratory experiments for southeastern US continental shelf plankton populations. Variations on a reference simulation, which represents average upwelling conditions without doliolids, were carried out to …

The Impacts Of External Nutrient Sources On Marine Phytoplankton In An Eastern Shore Sea-Side Estuary, Claudette Lajoie Jenkins

OES Theses and Dissertations

The Eastern Shore of Virginia (Greens Creek) as well as a large portion of the North Atlantic coastline is characterized by estuarine systems not dominated by large river systems. Instead, small freshwater creeks influence many coastal systems yet little information has been documented on their ecological significance. The focus of this research is to identify the biogeochemical and physical interactions within an estuarine water-column and understand the importance of freshwater sources in governing phytoplankton production. The hypothesis of this research is that increases in external nutrient loading into Greens Creek will not result in an increase in primary production. The …

Limitation Of Algal Growth By Iron Deficiency In The Australian Subantarctic Region, Peter N. Sedwick, Giacomo R. Ditullio, David A. Hutchins, Philip W. Boyd, F. Brian Griffiths, A. Clive Crossley, Thomas W. Trull, Bernard Queguiner

OES Faculty Publications

In March 1998 we measured iron in the upper water column and conducted iron- and nutrient-enrichment bottle-incubation experiments in the open-ocean Subantarctic region southwest of Tasmania, Australia. In the Subtropical Convergence Zone (∼42°S, 142°E), silicic acid concentrations were low (< 1.5μM) in the upper water column, whereas pronounced vertical gradients in dissolved iron concentration (0.12-0.84 nM) were observed., presumably reflecting the interleaving of Subtropical and Subantarctic waters, and mineral aerosol input. Results of a bottle-incubation experiment performed at this location indicate that phytoplankton growth rates were limited by iron deficiency within the iron-poor layer of the euphotic zone. In the Subantarctic water mass (∼46.8°S, 142°E), low concentrations of dissolved iron (0.05-0.11nM) and silicic acid (< 1μM) were measured throughout the upper water column, and our experimental results indicate that algal growth was limited by iron deficiency. These observations suggest that availability of dissolved iron is a primary factor limiting phytoplankton growth over much of the Subantarctic Southern Ocean in the late summer and autumn.

Resource Allocation And Sucrose Mobilization In Light Limited Eelgrass Zostera Marina, Teresa Alcoverro, Richard C. Zimmerman, Donald G. Kohrs, Randall S. Alberte

OES Faculty Publications

This study evaluated the ability of Zostera marina L. (eelgrass) to balance the daily photosynthetic deficit by mobilization of carbon reserves stored in below-ground tissues during a period of extreme winter light limitation. A quantitative understanding of the mobilization process and its limitations is essential to the development of robust models predicting minimum light levels required to maintain healthy seagrass populations. Plants were grown in running seawater tanks under 2 light regimes. One treatment was provided with 2 h irradiance-saturated photosynthesis (H_sat) to produce severe Light Limitation, while control plants were grown under 7 h H_sat, …