Background and aim of the research:
Offshore Drøbak there is a 1500m long and up to 25m high underwater wall from the skerries of Hurum via Småskjær to the islet of Søndre Kaholmen on which the Oscarsborg fortress is located. The wall was built in 1874-79 as a defence construction to prevent large vessels from sailing into the inner Oslofjord on the west side of the Oscarsborg fortress. Two small openings in the upper parts of the wall, one near Hurum, and another south of Søndre Kaholmen, allow small boats to pass.
For many decades, the inner Oslofjord environment has been negatively impacted by intense human activities, resulting in physical disturbance, chemical and organic pollution, eutrophication and related low oxygen conditions at the sea bottom. An ongoing discussion about how to improve water circulation and bottom water oxygen conditions in the inner Oslofjord, recently focused on the impact an opening of the Drøbakjeté might have on the circulation pattern.
The master thesis will focus on multiproxy studies (micropaleontological, sedimentological and geochemical parameter analyses) of marine sediment cores located in the vicinity of the Drøbakjeté (ideally N and S of the construction). Based on sediment accumulation rates, organic carbon and trace metal concentrations in dated cores, temporal environmental changes (past century) and spatial variability in the area can be determined.
The study of fossil benthic foraminiferal assemblages will allow us to assess the impact of the wall construction on the benthic soft bottom environment and ecosystem over time (last century) and space.
Research methodologies and database:
- The study will be based on the analyses of short sediment cores collected in the vicinity of the Drøbakjeté, Oslofjord.
- The project will focus on the analyses of pollutants, organic carbon content, and fossil benthic foraminiferal assemblages of dated sediment cores.
Learning outcomes:
- The master's student will be involved in field- and laboratory work.
- The student is asked to produce her/his own data and to describe and summarize the results in a scientific way.
- The student should be able to determine local environmental and ecological status changes over time, define reference conditions, and link and compare the results to existing studies.