| Phytoplankton primary production plays an important role in the global ocean production and is the first step in the uptake and sequestration of atmospheric CO2 to the deep ocean. Along with light, temperature and nutrient elements (N, P, Si, Fe, Co), extracellular availability of trace organic micronutrients, such as vitamins B12 and B1, is essential in the growth of many phytoplankton species. Vitamin B12 functions as a coenzyme in algal metabolism including the synthesis of DNA, Acetyl CoA, and methionine (amino-acid).; Despite the importance of vitamin B12 in the marine environment, the vitamin's ecological role and biogeochemical cycling in the marine systems is yet poorly understood. This is mainly due to lack of direct method for the determination of vitamin B12 in seawater. The bioassay method involves indirect determination of vitamin B12 using assay organisms whose growth is not always B12-specific and thus could underestimate the actual concentrations of this vitamin. Therefore, this dissertation research combined laboratory experiments and field investigations to develop a direct method of measuring vitamin B12 in seawater and used the new method to investigate the impact of vitamin B12 on the coastal phytoplankton bloom dynamics and shed light on the role of autochthonous (e.g. sediment remobilization) and allochthonous (e.g. freshwater discharge) in the cycling of vitamin B12 in the coastal embayments of Long Island, New York.; A direct method for the determination of vitamins B12 and B1 in seawater has been developed. This new protocol involves C 18 solid-phase extraction and quantification by Reversed Phase High Performance Liquid Chromatography (HPLC) with an UV-Vis absorbance detector at 362 nm and 270 nm respectively. The detection limits of the protocol are on the order of 0.03 pM and 0.08 for B12 and B1 with spike recoveries of 92--99%. The method was successfully applied to the determination of vitamins B12 and B1 in coastal waters of New York including filtered seawater, pore water, and river water samples. This method is sensitive, simple and reproducible and thus can be employed as a routine analytical tool for the accurate determination of dissolved B 12 and B1 in the marine environment. (Abstract shortened by UMI.)... |
