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Kristina Sundbäck

Om Kristina Sundbäck

Benthic ecology, microbenthos, microbial ecology. My research deals with the benthic ecology of marine shallow-water, illuminated sediments. The role of microbenthic communities (microalgae, bacteria and microscopic fauna) in the carbon and nutrient cycling in the "coastal filter" is studied. The response and recovery of these shallow-water ecosystems when exposed to anthropogenic impacts, such as changed nutrient load, raised temperature due to climate change, physical disturbance, and toxicants, alone or in combination, are assessed, as well as the role of habitat diversity on multifunctionality.

Current project The role of habitat diversity on the nutrient cycling and multifunctionality of shallow- water sediments While the relationship between biodiversity on species level and ecosystem function (BEF research) is today a timely research topic, hardly any experimental studies have been done on the role of habitat diversity on individual functions or multifunctionality. Experiments including different levels of habitat diversity of natural shallow-water sediments have been run during different seasons. We showed that experimental ecosystems comprised of a diversity of habitats show higher levels of multiple ecosystem functions than ecosystems with low habitat diversity. Our results show that the effect of habitat diversity on multifunctionality varies with season; it has direct effects on ecosystem functioning in summer and indirect effects, via changes in species diversity, in autumn, but no effect in spring. We propose that joint consideration of habitat diversity and species diversity will prove valuable for both environmental management and basic research. Some publications are still under way. This study has been lead by Dr Christian Alsterberg (GU, LU) as a post doctoral project, in collaboration with Pofessor Stefan Hult (GU), Professor Sara Hallin (SLU), Docent Lars Gamfeldt GU, Dr Lea Wittorf (SLU), Dr Fabian Roger (GU, LU), Dr Pia Engström (GU), Dr Yann Clough (LU) and KS.

Previous recent projects Role of shallow-water sediments as sinks and sources of nitrogen in the coastal zone Shallow-water illuminated sediments constitute an important functional part of the "coastal filter" where nutrients are transformed, retained and removed by processes mainly driven by autotrophic and heterotrophic microorganisms. The trophic state of the sediment (balance between oxygen production and consumption) largely decides whether the sediment functions as a sink or source of nitrogen (N). Autotrophic sediment functions mainly as a sink of nutrients. The role of dissolved organic nitrogen (DON) in the N-turnover and as a nitrogen source for benthic microalgae has also been studied. Dissolved free amino acids can constitute an important N source for benthic microalgae when the availability of dissolved inorganic nitrogen is limited. A Field study on nitrogen fixation (nitrogenas activity and abundance of nifH genes) on 60 sites along a 150 km stretch of the Swedish west coast, showed that the potential for N fixation in illuminated sediments can be considerable, stretching beyond cyanobacterial mats. The balance between N fixation by benthic

microbial mats and nitrogen removal by denitrification was studied to better understand the effect of managing nutrient loads to shallow bays. This study was done in co-operation with the County administration of Västra Götaland. Response of of shallow-water illuminated sediments to single and multiple stressors – individual functions and multifunctionality We have focused on the sensitivity and resilience of shallow-water, illuminated sediments to local, regional and global-scale environmental changes. The emphasis was on the role of microbially mediated key ecological functions and characters (primary production, trophic status, mineralization, nutrient cycling, nitrogen retention and removal, as well as biodiversity. Natural intact sediments were manipulated in flow-through mesocosms, under natural variation of light and temperature. Single and combined stressors included nutrient load, toxicants, hypoxia, increased sedimentation, warming and acidification. A further analyses of the results from 6 studies showed that stressors affected individual functions both positively and negatively, but multifunctionality was generally unaffected by both single and joint stressors. The functioning of coastal illuminated sediment systems thus appears resilient to exposure to moderate levels of both single multiple stressors. This resilience is due to the robustness of the benthic microalgal community, particularly benthic diatoms.