Diatoms as proxies for recent (0-20 years) environmental change as recorded in Inner Nærøyfjord sediments, Western Norway
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Three sediment cores, retrieved at three different stations in the inner Nærøyfjord, Western Norway, are analysed for their diatom assemblage. The dating of the cores is based on the distribution of coarse silt, the occurrence of freshwater diatoms, and precipitation data. The sediments of these cores are dated to have been deposited over a period of 13 years from 2008 to 2021. Based on the dating, the calculated sedimentation rate for the inner Nærøyfjord is approximately ±1cm/year. Several changes in the distribution of the diatoms in the sediment layers can be observed. The majority of diatom peaks matches the recorded precipitation peaks. Besides variations due to differences in freshwater diatom supply, a constant decrease of freshwater diatoms is recorded at the station in the Basin since 2015. This can be connected to effects of climate change in the Nærøyfjord region. A steady increase of marine benthic diatoms at the sampling station in the Basin since 2016 indicates an improvement towards less near-shore erosion caused by ships. Less benthic erosion favours the growth of marine benthic diatoms. Generally low numbers of marine benthic diatoms close to the quay of the harbour at Gudvangen are interpreted as a sign of deteriorating growing conditions due to turbulences and the deposition of mined Anorthosite during its loading on cargo ships. It is possible to use diatoms to detect ongoing environmental change as recorded in Inner Nærøyfjord sediments. The status as proxies for environmental change is partly restricted by the determination to genus level instead of species level, which would narrow down possible sources for occurring changes in the distribution of diatoms in the sediments.
An Honours thesis submitted to Carl von Ossietzky Universität Oldenburg and Høgskulen på Vestlandet (Western Norway University of Applied Sciences) in fulfillment of the requirements for the degree of Bachelor of Science in Biology.