| dc.contributor.author | Chen, Wenhao. | en_US |
| dc.date.accessioned | 2014-10-21T12:38:02Z | |
| dc.date.available | 1992 | |
| dc.date.issued | 1992 | en_US |
| dc.identifier.other | AAINN80229 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55346 | |
| dc.description | A significantly improved understanding of the amount of DOC and DON in seawater, their sources and sinks is of critical importance in understanding the global cycles of carbon and nitrogen. Recently, a major controversy about the measurement of DOC and DON and their chemical reactivity and biological lability has attracted much attention in the oceanographic community, mainly due to the high values found by Suzuki et al (1985) and Sugimura and Suzuki (1988) using a high temperature catalytic oxidation (HTCO) method. | en_US |
| dc.description | Major modifications were made to the HTCO DOC system of Sharp (1973). The modified system was tested for accuracy, precision, and reliability. The total blank of this system was determined to be in the range of 10-20 $\mu$M carbon. Differentiating between the machine blank and the water blank was done by the use of "Wonder Water" (Millipore Super-Q water oxidized by HTCO), which was found to be essentially carbon-free. This result was confirmed by an experiment using $\sp $C. | en_US |
| dc.description | The HTCO DOC method was compared directly to the UV photo-oxidation method: the former finds 5-60% more DOC in seawater, but not 2-4 times more. | en_US |
| dc.description | Six methods of sample preservation were tested. Poisoning with HgCl$\sb2$ and acidification and storage under refrigeration were found to be both efficient and convenient. For the HTCO measurement, the latter was more practical, and thus preferable. | en_US |
| dc.description | The HTCO system was also used to measure DON according to the method of Suzuki et al. (1985). This method was found to be efficient and precise. Results for seawater samples were in the range of those obtained previously by UV and persulfate oxidation methods. The very high DON values of Suzuki et al. (1985) could not be reproduced by the application of this method. | en_US |
| dc.description | The production of DOC by phytoplankton was studied by culture experiments. The diatoms Chaetoceros gracilis and Phaeodactylum tricornutum, the flagellate Isochrysis galbana, and the natural algal assemblage in the Northwest Arm, Nova Scotia were found to release a significant amount of DOC in log phase growth. Maximum release took place during the stationary and decomposition stages. The dinoflagellate Alexandrium tamarense lived as both autotroph and heterotroph. The release of DOC by this species differed greatly from the other species, taking place only after the crash of the culture. | en_US |
| dc.description | Long term studies on the use of algal exudates by bacteria in sea water demonstrated that DOC released by marine diatoms had high potential turnover rates. Microbial consumption of DOC followed first order reaction kinetics. A decay rate as high as 0.49 day$\sp{-1}$ was obtained in this way for the DOC released by C. gracilis. The exudates of A. tamarense were found to be essentially bacteria resistant. | en_US |
| dc.description | Two time-series observations in the Northwest Arm and Bedford Basin, Nova Scotia demonstrated significant increases in DOC during phytoplankton blooms. Similarities between the results from batch cultures and from spring bloom observations suggested that the bloom phytoplankton released significant amounts of DOC during and after the bloom. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1992. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.subject | Biogeochemistry. | en_US |
| dc.title | The measurement, production and degradation of marine dissolved organic matter. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
