Spatial analysis of eutrophication-related indicators in the northern Bothnian Bay
1University of Oulu, Faculty of Science, Geography
|Online Access:||PDF Full Text (PDF, 4.6 MB)|
|Persistent link:|| http://urn.fi/URN:NBN:fi:oulu-201605071653
|Publish Date:|| 2016-05-09
|Thesis type:||Master's thesis
At present, eutrophication is one of the biggest threats to the Baltic Sea environment. Eutrophication is a process in which water body gathers essential plant nutrients, mainly phosphorus and nitrogen into its system. Eutrophication causes a variety of changes to the marine environment. These effects include an increased primary production, turbidity and sedimentation, the occurrence of anoxia and hypoxia, as well as changes in macroalgal community structures. The most common parameters used to study the negative effects of eutrophication on the environment are nitrogen, phosphorus, chlorophyll-a, water transparency and oxygen. In the past, several efforts and actions were made in order to minimize the negative effects of eutrophication to the sea, for example by European directives. Some of these directives require the use of biological quality elements such as marine flora and fauna as an indicator for the water quality. Because of these requirements, it is important to study the use of filamentous algae as an indicator of eutrophication. This thesis contributes to a better understanding of the impact of land use on the environmental indicators of eutrophication and the opportunity to use filamentous algae as an indicator of eutrophication in the Bothnian Bay. The study area is situated in the Finnish side of the Bay, extending from the city of Oulu in south to the city of Tornio in north. This thesis analyses the impact of the land use practices on the environmental indicators of eutrophication by determining the optimum buffer sizes for land use. Different land use practices show clear correlations to the environmental variables and, based on these results, it can be stated that there is a connection between the two components. In order to investigate the correlation between filamentous algae and eutrophication indicators, the used indicators needed were interpolated to the whole study area. The interpolation was needed, because the datasets were collected from different areas and the resolution of the data of the filamentous algae was much higher. Since the amount of data points from the environmental variables was relatively low with 59 sites, 61 additional data points were chosen to increase the coverage of the data. Linear regression models were created for the environmental variables and based on these models values were estimated for the added data point. The interpolations of the environmental variables were compared with the average values of filamentous algae with the help of Spearman’s rho correlation matrix. In the tests, statistically significant correlations towards the environmental indicators of eutrophication were found. The analyses indicate a connection between the amounts of filamentous algae and eutrophication related indicators. Based on this, in can be concluded that filamentous algae is a useful indicator of eutrophication in the northern Bothnian Bay, when it is used together with other eutrophication indicators. However, attention needs to be paid when comparing data of filamentous algae in a large scale, since other physical factors, such as water temperature, have a significant impact to the distribution and abundance of the algae.
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