Temperature Experiment
Temperature is most likely to change in the future climate, especially during winter. As temperature directly affects almost all processes - physic, chemical and biological - temperature changes will probably have consequences on the state of and the biological structure of the fresh and marine water environment.
To examine the consequences of an increased winter temperature on the biological structure and the balance between autotrophic (phytoplankton) and heterotrophic (bacteria) process, DHI Water & Environment and University of Aarhus conducted mesocosm experiments in Bergen, Norway, in February 2003.
Thermoregulated mesocoms were established containing the natural winter plankton community and mesocoms at either, 6 ºC, 9 ºC, and 12 ºC were followed for the next 14 days. The response in phytoplankton and bacteria biomass and activity was continuously determined. The experiments revealed that bacteria activity were more stimulated than phytoplankton activity by the temperature increase, suggesting that an increased winter temperature will favour the bacteria compared to phytoplankton.
A favouring of the bacteria and heterothrophic activity in general can lead to an enhanced nutrient cycling in the water phase, and a reduction of sedimentation of organic matter. Hence, one isolated effect of temperature increases could be reduced oxygen consumption at the sediment surface. However, climate changes is more than just temperature changes and the effects from this experiment will be incorporated in mathematical models, which will be applied analysing the sum of climate changes on the marine environment.
A more detailed presentation and interpretation of the data is presented in ‘Vand & Jord, 2003 vol. 4 (in Danish)
 |