| dc.identifier.uri | http://hdl.handle.net/11401/77789 | |
| dc.description.sponsorship | This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. | en_US |
| dc.format | Monograph | |
| dc.format.medium | Electronic Resource | en_US |
| dc.language.iso | en_US | |
| dc.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dc.type | Dissertation | |
| dcterms.abstract | Extracellular enzymes (EE) initiate heterotrophic remineralization by hydrolyzing high-molecular-weight organic matter to substrates sufficiently small (~600 Da) to be transported across cell membranes. An accurate understanding of EE associated remineralization processes in sedimentary deposits requires measuring patterns of extracellular enzyme activity (EEA) with minimal disturbance. Traditional methods for measuring EEA typically involve sectioning of sediment cores and incubation. This approach at best results in an averaged one-dimensional profile with low resolution. Any natural heterogeneity in enzyme activity is obscured and the possible association of activity patterns with sedimentary structure minimized. My dissertation work focused on the development of a planar sensor system to measure two-dimensional EEA in marine sediments. The underlying principle of this new system is the incorporation of a fluorogenic enzyme substrate (Leu-MCA in this application) into a polymer carrier and the controlled release of that substrate into a contacting medium while transport and reactions are continuously monitored. The sensor foils reveal real-time proteolytic enzyme (Leucine-aminopeptidase) activity patterns across the planar surfaces at high spatial resolution (~50-100µm). This 2-D methodology provides a unique means to directly and independently measure the complex, unsteady processes affecting reactive organic matter substrate distributions in both oxic and anoxic zones of sedimentary deposits. This new sensor system was used to study seasonal EEA distributions in Great Peconic Bay sediments. Results showed that EEA varies seasonally: highest during the spring bloom and summer, and lowest during the fall and early winter. Seasonal variation is determined by both temperature and the availability of reactive organic substrates. Spatial heterogeneity was less obvious in cold seasons mainly due to low bio-activities. In warm seasons, however, a higher degree of horizontal heterogeneity was observed as the result of increased organic deposits and active macrobenthos. Degradation hot spots with sizes ranging from millimeters to one centimeter were observed in some seasons and were found to be associated with burrow structures and phytoplankton aggregates. The deposition of phyto-detritus from an early spring bloom greatly enhanced surface sediment EEA, and at this time high EEA closely coincided with regions of elevated metabolite production. However, EEA and solute build up patterns are decoupled during much of the year because of the different transport mechanisms and rates of transport affecting reactive particle substrates and solutes in bioturbated deposits. EEA correlates directly with depth integrated remineralization rates (∑ CO<sub>2</sub>, NH<sub>4</sub><super>+</super> production) but because EEA is a potential measurement (saturated rate) the correlation is not necessarily stoichiometrically exact. An incubation experiment was conducted to study the EEA change as a response of bacteria communities to rapid variation in temperature. The results showed that bacteria responded quickly to temperature changes. Bacteria tend to synthesize a higher portion of LAP at low temperatures and a greater portion of Glucosidase and Phosphatase at temperatures higher than the in situ temperature they live. Temperature sensitivity curves showed that the initial response of the bacteria community to temperature change is always to alter their yield of EE. With longer exposure to a temperature change, community structure may alter or a succession of isoenzymes may occur shortly after a temperature shift. | |
| dcterms.abstract | Extracellular enzymes (EE) initiate heterotrophic remineralization by hydrolyzing high-molecular-weight organic matter to substrates sufficiently small (~600 Da) to be transported across cell membranes. An accurate understanding of EE associated remineralization processes in sedimentary deposits requires measuring patterns of extracellular enzyme activity (EEA) with minimal disturbance. Traditional methods for measuring EEA typically involve sectioning of sediment cores and incubation. This approach at best results in an averaged one-dimensional profile with low resolution. Any natural heterogeneity in enzyme activity is obscured and the possible association of activity patterns with sedimentary structure minimized. My dissertation work focused on the development of a planar sensor system to measure two-dimensional EEA in marine sediments. The underlying principle of this new system is the incorporation of a fluorogenic enzyme substrate (Leu-MCA in this application) into a polymer carrier and the controlled release of that substrate into a contacting medium while transport and reactions are continuously monitored. The sensor foils reveal real-time proteolytic enzyme (Leucine-aminopeptidase) activity patterns across the planar surfaces at high spatial resolution (~50-100µm). This 2-D methodology provides a unique means to directly and independently measure the complex, unsteady processes affecting reactive organic matter substrate distributions in both oxic and anoxic zones of sedimentary deposits. This new sensor system was used to study seasonal EEA distributions in Great Peconic Bay sediments. Results showed that EEA varies seasonally: highest during the spring bloom and summer, and lowest during the fall and early winter. Seasonal variation is determined by both temperature and the availability of reactive organic substrates. Spatial heterogeneity was less obvious in cold seasons mainly due to low bio-activities. In warm seasons, however, a higher degree of horizontal heterogeneity was observed as the result of increased organic deposits and active macrobenthos. Degradation hot spots with sizes ranging from millimeters to one centimeter were observed in some seasons and were found to be associated with burrow structures and phytoplankton aggregates. The deposition of phyto-detritus from an early spring bloom greatly enhanced surface sediment EEA, and at this time high EEA closely coincided with regions of elevated metabolite production. However, EEA and solute build up patterns are decoupled during much of the year because of the different transport mechanisms and rates of transport affecting reactive particle substrates and solutes in bioturbated deposits. EEA correlates directly with depth integrated remineralization rates (∑ CO<sub>2</sub>, NH<sub>4</sub><super>+</super> production) but because EEA is a potential measurement (saturated rate) the correlation is not necessarily stoichiometrically exact. An incubation experiment was conducted to study the EEA change as a response of bacteria communities to rapid variation in temperature. The results showed that bacteria responded quickly to temperature changes. Bacteria tend to synthesize a higher portion of LAP at low temperatures and a greater portion of Glucosidase and Phosphatase at temperatures higher than the in situ temperature they live. Temperature sensitivity curves showed that the initial response of the bacteria community to temperature change is always to alter their yield of EE. With longer exposure to a temperature change, community structure may alter or a succession of isoenzymes may occur shortly after a temperature shift. | |
| dcterms.available | 2017-09-20T16:53:35Z | |
| dcterms.contributor | Aller, Josephine | en_US |
| dcterms.contributor | Aller, Robert C | en_US |
| dcterms.contributor | Zhu, Qingzhi | en_US |
| dcterms.contributor | Lee, Cindy | en_US |
| dcterms.contributor | Arnosti, Carol. | en_US |
| dcterms.creator | Cao, Zhenrui | |
| dcterms.dateAccepted | 2017-09-20T16:53:35Z | |
| dcterms.dateSubmitted | 2017-09-20T16:53:35Z | |
| dcterms.description | Department of Marine and Atmospheric Science. | en_US |
| dcterms.extent | 130 pg. | en_US |
| dcterms.format | Application/PDF | en_US |
| dcterms.format | Monograph | |
| dcterms.identifier | http://hdl.handle.net/11401/77789 | |
| dcterms.issued | 2015-08-01 | |
| dcterms.language | en_US | |
| dcterms.provenance | Made available in DSpace on 2017-09-20T16:53:35Z (GMT). No. of bitstreams: 1
Cao_grad.sunysb_0771E_11676.pdf: 2311100 bytes, checksum: 4911c91ff472cd0c3e106ca7633380e8 (MD5)
Previous issue date: 2013 | en |
| dcterms.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dcterms.subject | Chemical oceanography | |
| dcterms.subject | Enzyme planar fluorosensor, Extracellular enzyme activity, in-situ, Leucine-aminopetidase, Marine sediments, Two-dimensional measurements | |
| dcterms.title | Annual sedimentary extracellular enzyme activities in Great Peconic Bay -- From a two dimensional perspective | |
| dcterms.type | Dissertation | |
