In his thesis, JP studied the microbial production and consumption of methane, a powerful greenhouse gas, in both coastal and open areas of the Baltic Sea. Eutrophication of the Baltic Sea has led to high rates of methane production due to the accumulation of “legacy” organic matter (mainly decaying algae) in sediments. Yet, oxidation by microbes prevents much of the methane produced in these habitats from entering the atmosphere. JP studied the balance between production and consumption of methane in coastal areas, and how disturbances such as salt-water pulses into the Baltic Sea can affect methane cycling in offshore regions.
In a socially-distanced event at Viikki campus, the opponent Jouni Lehtoranta probed JP’s choice of methods, study areas and main conclusions, and at one point asked how many cows would be required to produce the same amount of methane as the Baltic Sea, provided that a single cow can produce 100 kg of methane per year. After thinking for a moment, JP rightly concluded that the number is probably in the millions. Considering that there are only 300 000 cows in Finland, it is clear that the Baltic Sea is an important potential source of methane. However, as JP’s work shows, much of this methane never reaches the atmosphere due to natural oxidation processes acting as a filter in the sediments and water column.
The thesis was supervised by Dr. Tom Jilbert and Dr. Susanna Hietanen and funded by the Academy of Finland as well as the Onni Talas Foundation and the Walter and Andrée de Nottbeck foundation. The e-thesis can be found here: https://helda.helsinki.fi/handle/10138/315095
Social-distancing was kept during the defense, the outdoor reception, and the speeches. Last picture: JP with his supervisors Tom Jilbert and Susanna Hietanen (pics: T. Jilbert, S. Zhao).