Eutrophication together with climate change caused by excess nutrient inputs and greenhouse gas emissions are major threats to the Baltic Sea ecosystem. These societal challenges can be adressed with biological solutions such as microalgae that can contribute to both climate change and eutrophication mitigation efforts. The project aims to study natural microalgal communities grown in pilot scale cultivation systems to recover nutrients from different industrial waste streams (leachate, dairy, coastal seawater) and carbon dioxide from fluegas. Previous research has mainly focused on monocultures that are known to have the desired characteristics (high lipid content, high growth rate). However, natural communities are often more resilient in terms of environmental fluctuations and have the potential to fill up several functional niches that might increase productivity and nutrient recovery. Past studies have also shown that interactions between microalgae and bacteria can result in a higher productivity. The project investigates how community composition, seasonal succession and interactions between the organisms affect nutrient recovery and biomass quality (biochemical metabolites) in pilot scale outdoor systems in temperate Scandinavian climate. We hypothesise that succession of species over different seasons occur in the reactors and that selection for the best competitors lead to a stable production of high quality products and recovery of nutrients.