The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Modelling of Water Circulation and the Dynamics of Phytoplankton for the Analysis of Eutrophication

Arto Inkala

Dissertation for the degree of Doctor of Science (Technology) to be presented with due permission for public examination and debate in Auditorium E at Helsinki University of Technology (Espoo, Finland) on the 26th of October at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-5686-X)   [525 KB]
Dissertation is also available in print (ISBN 951-22-5664-9)


The eutrophication and algal blooms are problems in many Finnish lakes and sea areas. One possible way to approach the problem is mathematical modelling. If the most important processes have been successfully modelled, it is easy to calculate the effects of nutrient load changes. This thesis presents experiences on developing and applying eutrophication models.

The pre-calculated flow fields are the most important input to the water quality model, so the applications of the flow model are examined in two papers. The results indicate that the flow model can produce typical flows caused by wind. The simulations of the timing of upwelling were also successful. The excessive vertical diffusion can cause problems in eutrophication model applications.

The results of simulations indicate that the greenhouse effect will advance and enlarge the spring bloom of phytoplankton. However, the average phytoplankton biomass in the Gulf of Finland will be near current level, defined in these scenarios by the available amount of nutrients almost unchanged due to the insignificant changes in the external nutrient inputs.

The more significant nutrient load reductions from the major loading points have a clearly decreasing effect on the total algal biomasses even in one year long simulations. When the nitrogen fixing cyanobacteria was taken into account in the simulation, the results indicated that the phosphorus removal from St. Petersburg would decrease both average cyanobacteria and other algae biomasses. The biomass of other algae might increase in the zone where additional nitrogen is transported from the east. The Finnish national agenda, which is nitrogen dominated, does not seem to be an effective way to fight against accumulations of cyanobacteria. However, the total phytoplankton biomass will decrease near the Finnish coast.

This thesis consists of an overview and of the following 6 publications:

  1. Inkala A., Myrberg K. 2001 Comparison of hydrodynamical models of the Gulf of Finland in 1995 - a case study, Systems Analysis Laboratory Research Reports E9, September 2001, Helsinki University of Technology, (submitted also to Environmental Modelling & Software). © 2001 by authors.
  2. Inkala A., Kuusisto M., Sarkkula J., Koponen J. 1999, Currents and transport of sewage water in the coastal area of Vaasa, Northern Baltic Sea - a study with current measurements and modelling, Proceedings of the 3rd International Marine Environmental Modelling Seminar '99, 12-14.4.1999, Lillehammer, Norway. © 1999 SINTEF. By permission.
  3. Inkala A., Hellsten S., Heikkinen M. 1998, Integrated 3D Modelling of Water Circulation and the Dynamics of Phytoplankton; the Effects of New Reservoir, Internat. Rev. Hydrobiol. 83:681-688. © 1998 Wiley-VCH Verlag Berlin GmbH. By permission. Wiley InterScience
  4. Inkala A., Bilaletdin Ä., Podsetchine V., 1997, Modelling the effect of climate change on nutrient loading, temperature regime, and algal biomass in the Gulf of Finland, Boreal Environment Research 2:287-301. © 1997 Boreal Environment Research. By permission.
  5. Inkala A., Pitkänen H. 1999, The effect of load reductions on algal biomass in the eastern Gulf of Finland - modelling point of view, Boreal Environment Research 4:357-366. © 1999 Boreal Environment Research. By permission.
  6. Kiirikki M., Inkala A., Kuosa H., Pitkänen H., Kuusisto M., Sarkkula J. 2001, Evaluating the effects of nutrient load reductions on the biomass of toxic nitrogen-fixing cyanobacteria in the Gulf of Finland, Boreal Environment Research 6:131-146. © 2001 Boreal Environment Research. By permission.

Keywords: phytoplankton dynamics, hydrodynamics, load reductions, eutrophication, nutrients, Gulf of Finland

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© 2001 Helsinki University of Technology

Last update 2011-05-26