Abstract
The aim of this thesis was the study of respiration in ocean marginsediments and the assessments of tools needed for this purpose.
The first study was on the biological pump and global respirationpatterns in the deep ocean using an empirical model basedon sediment oxygen consumption data. In this thesis the depthdependence of respiration patterns was modelled using a compiled dataset of sediment oxygen consumption rates. We showed that the depthrelationship can best be described by a double exponential model. Byassuming a uniform flux laterally across the global ocean the depthattenuation of POC could be derived. The results from this study implya more efficient biological pump.
The second study was on the short-term fate of phytodetritus,investigated across the Pakistan margin of the Arabian Sea. Stationsranged in water depths from 140 to 1850 m, encompassing the oxygenminimum zone. Phytodetritus sedimentation events were simulated byadding 13C-labelled algal material to surface sediments. The labelledcarbon was subsequently traced into bacterial lipids as a proxy ofbacterial biomass, foraminiferan and macrofaunal biomass as well asinto dissolved organic and inorganic pools. The largest pool ofprocessed carbon was found in dissolved inorganic carbon, attributedto respiration. Macrofaunal influence was most pronounced at the lowerpart of the oxygen minimum zone.
The third study was on benthic respiration rates in the Gulf ofFinland, Baltic Sea. Rates were based on in situ incubationsusing benthic chamber landers. Three contrasting stations withdifferent sediment accumulation regimes were visited. The effect ofchanges in water masses on the benthic fluxes was investigated with adynamic diagenetic model. Fluxes of dissolved inorganic carbon werehighest at the station with accumulation bottom, intermediate at thestation with transport bottom and lowest at the station with erosionsediments.
The fourth study was primarily a theoretical investigation of how wella certain model parameter can be constrained based on a certaindataset. A model of bio-irrigation was used as a good example of this.The interpretation is based on fitting observed data with a modelcontaining several parameters, where some parameters are a priori unknown. In this chapter, it was tested under whatconditions the results obtained through this fitting are robust. Theresults from this study imply that using only the concentrationchange in the overlying water, it is not possible to constrain boththe rate and the mechanism of bio-irrigation, thus, sampling theporewaters at the end of the incubation is a necessity.
The fifth study was an an evaluation of the performance of an oxygenoptode. The performance of the sensor was evaluated and compared withdata obtained by other methods. The principal conclusion was that,owing to high accuracy, long-term stability (morethan 20 months), lack of pressure hysteresis and limitedcross-sensitivity, this method is overall more suitable for oxygenmonitoring in the aquatic environment than other methods.
The first study was on the biological pump and global respirationpatterns in the deep ocean using an empirical model basedon sediment oxygen consumption data. In this thesis the depthdependence of respiration patterns was modelled using a compiled dataset of sediment oxygen consumption rates. We showed that the depthrelationship can best be described by a double exponential model. Byassuming a uniform flux laterally across the global ocean the depthattenuation of POC could be derived. The results from this study implya more efficient biological pump.
The second study was on the short-term fate of phytodetritus,investigated across the Pakistan margin of the Arabian Sea. Stationsranged in water depths from 140 to 1850 m, encompassing the oxygenminimum zone. Phytodetritus sedimentation events were simulated byadding 13C-labelled algal material to surface sediments. The labelledcarbon was subsequently traced into bacterial lipids as a proxy ofbacterial biomass, foraminiferan and macrofaunal biomass as well asinto dissolved organic and inorganic pools. The largest pool ofprocessed carbon was found in dissolved inorganic carbon, attributedto respiration. Macrofaunal influence was most pronounced at the lowerpart of the oxygen minimum zone.
The third study was on benthic respiration rates in the Gulf ofFinland, Baltic Sea. Rates were based on in situ incubationsusing benthic chamber landers. Three contrasting stations withdifferent sediment accumulation regimes were visited. The effect ofchanges in water masses on the benthic fluxes was investigated with adynamic diagenetic model. Fluxes of dissolved inorganic carbon werehighest at the station with accumulation bottom, intermediate at thestation with transport bottom and lowest at the station with erosionsediments.
The fourth study was primarily a theoretical investigation of how wella certain model parameter can be constrained based on a certaindataset. A model of bio-irrigation was used as a good example of this.The interpretation is based on fitting observed data with a modelcontaining several parameters, where some parameters are a priori unknown. In this chapter, it was tested under whatconditions the results obtained through this fitting are robust. Theresults from this study imply that using only the concentrationchange in the overlying water, it is not possible to constrain boththe rate and the mechanism of bio-irrigation, thus, sampling theporewaters at the end of the incubation is a necessity.
The fifth study was an an evaluation of the performance of an oxygenoptode. The performance of the sensor was evaluated and compared withdata obtained by other methods. The principal conclusion was that,owing to high accuracy, long-term stability (morethan 20 months), lack of pressure hysteresis and limitedcross-sensitivity, this method is overall more suitable for oxygenmonitoring in the aquatic environment than other methods.
| Original language | English |
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| Qualification | Doctor (dr.) |
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| Supervisors/Advisors |
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| Award date | 12 Nov 2007 |
| Place of Publication | Utrecht |
| Publisher | |
| Publication status | Published - 12 Nov 2007 |