Effect of resuspension on mineralisation of organic material: Laboratory studies of water movement intensity and concentration of suspended sediment
Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
The Earth’s surface contains of 71% oceans and a large part of the global carbon cycle takes place in the oceans. In the aquatic environment, the sediment-water interface plays an important role for the mineralisation of organic material. One factor that can affect the mineralisation is resuspension. Resuspension cause mixing of surface sediments and bottom water and result in a redistribution of the sediment when it settles again. Resuspension also increases the transport of oxygen into the sediment, reduces the diffusive boundary layer surrounding particles, and enhance the nutrient uptake. Resuspension can be induced by both wave action and bottom currents and is a common physical process in both shallow coastal areas and in the deep ocean. Human impacts, such as dredging and trawling, can also cause resuspension.
The effect of resuspension on mineralisation of organic material was studied in two experiments ex situ during December to April 2004/2005. The aim for Experiment 1 was to investigate how the intensity of the resuspension event affects the degradation rate. The aim for Experiment 2 was to investigate how different concentrations of resuspended sediment affect the degradation rate of organic matter. Sediment samples were collected in December and late March at a marine field station, Askö, Sweden. Sediment and bottom water were transferred to and incubated in sealed bottles. For Experiment 1, resuspension was created in bottles with a specially designed rotary table, creating different intensity of water movements. In Experiment 2, bottles with different concentrations of sediment were put on an ordinary rotary table. The mineralisation rates were in both experiments monitored by daily sampling of sediment-water slurry, and analysed for total inorganic carbon by a gas chromatography with a thermal detector, GC-TCD.
Results from Experiment 1 did not show any clear patterns regarding inorganic carbon formation. Experiment 2 did show clear patterns for two of six replicates of mineralisation of organic material. For these replicates the mineralisation rate were low according to previous studies. However, the sediment concentration seems to not affect the mineralisation rate. For both experiments, valuable information on how to better design experiments to investigate the importance of resuspension and the effect of mineralisation of organic material was yielded. Hence, further studies are needed to continue the investigation of the importance of resuspension for the mineralisation rate of organic material, and its impacts on the nutrient fluxes in the oceans.
Place, publisher, year, edition, pages
Institutionen för tematisk utbildning och forskning , 2005. , 22 p.
Mineralisation rate, organic material, resuspension, water movement intensity, suspended sediment
IdentifiersURN: urn:nbn:se:liu:diva-4946ISRN: LIU-ITUF/MV-D--05/16--SEOAI: oai:DiVA.org:liu-4946DiVA: diva2:20830