External examiners:

• Main Authors: Laura Forsström, Prof Atte Korhola, Dr. John Hobbie
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Climate change; Phytoplankton; Subarctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.413.3632; http://ethesis.helsinki.fi/julkaisut/bio/bioja/vk/forsstrom/phytopla.pdf

The climate is warming and it is most noticeable in the arctic and subarctic areas, where the warming trend is expected to be the greatest. Arctic and subarctic freshwater ecosystems, which are a very characteristic feature of the northern landscape, are especially sensitive to climate change. They could be used as early warning systems, but more information about the ecosystem functioning and responses are needed for proper interpretation of the observations. Phytoplankton species and assemblages could be especially suitable for climate-related studies, since they have short generation times and react rapidly to changes in the environment. In addition, phytoplankton provides a good tool for lake classifications, since different species have different requirements and tolerance ranges for various environmental factors. The use of biological indicators is particularly useful in arctic and subarctic areas, where many of the chemical factors commonly fall under the detection limit and therefore do not provide much information about the environment. This work brings new information about species distribution and dynamics of subarctic freshwater phytoplankton in relation to environmental factors. The phytoplankton of lakes in Finnish