Browsing by Author "Sigg, Milla"

The Baltic Sea is a sensitive brackish waterbody, which is facing several disturbances. These stressors include land-use changes, over-fishing, climate change, pollution, alien species and eutrophication. Eutrophication causes increased primary production of opportunistic macroal-gae. These macroalgal mats cover the seafloor and cause light and oxygen depletion as well as mortality of benthic plants and fauna. Aquatic macrophytes provide important ecosystem ser-vices and food and shelter for macrofauna. The depletion of the benthic community may have large consequences to ecosystem functioning. In this master’s thesis, I studied the recovery of a macrophyte-associated macrofauna community after disturbance in a vegetated aquatic habitat. The disturbance was mimicking drifting algal mats, and it was induced in 2017. My thesis was a part of a larger project conducted at Tvärminne Zoological station in Hanko, Finland, studying the recovery of macrophyte communities of different functional diversity and their associated macrofauna. The samples were taken annually from 2017 to 2021. I examined which factors affected the recovery. In my analyses, I focused on the communities of animal species. Additionally, I assessed if there was an edge-effect in recovery and if opportunistic species were the first to recover, i.e., return to the site. The recovery was studied statistically using non-metric multidimensional scaling (NMDS), similarity percentage i.e., SIMPER and analysis of similarities i.e., ANOSIM. Results of the experiment showed that the site recovered in 2020 the latest. There was not a clear edge effect in recovery. A gradual re-introduction of common species happened, not a replacement of species. Some of the most common species possessed opportunistic traits. These results show that the recovery of systems is not linear but complex, and several factors affect their resilience.