Tracing Environmental Change and Human Impact as Recorded in Sediments from Coastal Areas of the Northwestern Baltic Proper

The eutrophication of the Baltic Sea due to increased anthropogenic nutrient loads during the 20th century is well documented and studied. However, in the Baltic Sea drainage area, humans have affected the environment longer than the environmental monitoring can provide data for. Sediment records from lakes and seas can provide fundamental data on the environmental conditions before ecosystems were impacted by humans and give the range of natural variation. This thesis presents diatom and geochemistry stratigraphies from five sediment records along the southeast coast of Sweden, northwestern Baltic Proper. These records cover time periods of 500 years to more than 2,000 years. The diatom stratigraphies and geochemical proxies allow for reconstruction of environmental histories at these sites. The outcomes of this thesis highlight the importance of a longer time perspective than the environmental monitoring can provide. Abstract Svensk sammanfattning List of papers Abbreviations and definitions Introduction Thesis objectives Background Holocene history of the Baltic Sea The present Baltic Sea Effects of climate on the Baltic Sea ecosystem Climate during the Holocene Records of early human impact in lakes Agrarian history in southern Sweden during the last millennium Description of study sites Kanholmsfjärden Ådfjärden Himmerfjärden Bråviken Gåsfjärden The western Gotland Basin Material and Methods Field work Chronologies Diatoms as a proxy for environmental change Geochemical proxies Data processing and statistical analyses Results – summary of papers Interpretation and Discussion Signs of eutrophication in the coastal zone during the last centuries Causes for eutrophication in the coastal zone Tracing human impact and climate change during medieval times Climate or nutrients as drivers of paleoecological trends in the Baltic Sea since 500 CE Implications for the environment Conclusions References Tack Paper I (missing) Paper II (missing) Paper III (missing) Paper IV (missing) Södertörn Doctoral Dissertations