Spring ice melt effect on benthic oxygen production

Sammanfattning: In biology, the winter season is less studied than other seasons partly due to technical and logistical difficulties. The Arctic region is undergoing rapid changes with shorter and warmer winters, shorter snow duration and considerable changes in snow and ice cover as a result. Climate change also has other consequences such as added influx of DOC to aquatic systems which may have repercussions for aquatic food webs. This study investigates the effect of ice melt on benthic oxygen production and also investigates the pelagic counterpart. This study also investigates levels of light, CO2 and DOC and their impact on benthic and pelagic oxygen production in a simulated climate change scenario. Sampling for the study took place at the Umeå University Experimental Ecosystem Facility which exhibits artificial ponds, some of which had been treated to simulate changes caused by climate change such as added DOC or having been artificially heated during summers. Measurements for O2, CO2 and light (photosynthetic active radiation) were collected from these artificial ponds at three different occasions around the time of ice release: Iced over conditions, after ice melt and later in spring. Ice melt was not proven to result in a difference in benthic oxygen production, as no significance could be found between O2-production during ice-covered conditions and later during the spring. Ice release did however seem to be the cause of a significant effect in the pelagic habitat which exhibited higher O2-production during the period of ice release. A significant difference in O2-production was also found in the pelagic habitat between ponds treated with added DOC and ponds that were not, but no such difference could be found for the benthic habitat. This highlights important differences between the habitats. The study proposes that earlier times of ice release, higher levels of DOC and higher summer temperatures may perhaps influence the oxygen production in the benthic habitat to a lesser extent than the pelagic habitat in northern aquatic systems, but this requires further studies.