Kari Skjånes
Research Scientist
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ResearchGateBiography
Abstract
Algal-based wastewater treatment (phycoremediation) relies on microbial interactions within the algal phycosphere that are associated with algal growth and nutrient removal. However, the temporal dynamics of these communities under operational conditions remain poorly resolved. Using 16S and 18S rRNA gene metabarcoding, this study characterized bacterial and eukaryotic communities across alga-attached and free-living size fractions and over time in a raceway-based, pilot-scale phycoremediation system using a filamentous algal co-culture under semicontinuous municipal wastewater flow. Bacterial community composition in the phycosphere overlapped substantially with that observed in a previous laboratory-scale study using the same algal co-culture, with many highly abundant ASVs shared across studies, supporting consistency of key community members across scales. Phycosphere community dynamics were temporally aligned with algal growth, with bacterial alpha diversity in the alga-attached fraction highest during periods of active algal growth and declining with the onset of algal phosphorus limitation. During this high-diversity phase, several orders within Alphaproteobacteria were enriched, followed by declines as the algal culture progressed toward reduced growth. Eukaryotic communities also showed clear successional trends, with Perkinsids (Alveolata) increasing during peak algal biomass before giving way to diverse protists and rotifers. These findings demonstrate coordinated temporal patterns between algal growth dynamics and phycosphere microbial succession in pilot-scale wastewater raceways, providing operational insight into microbial community structure under phosphorus-limited phycoremediation.
Abstract
Algal-based wastewater remediation systems (phycoremediation) include phycosphere bacterial communities that influence algal growth, pollutant remediation, and downstream applications of biomass as fertilizers or bio-stimulants. This study investigated the bacterial community dynamics in a novel phycoremediation system using a co-culture of the green algae Stigeoclonium sp. and Oedogonium vaucheri. Bacterial abundance was estimated using flow cytometry (FCM), while community composition was assessed through 16S rRNA gene metabarcoding. Additionally, 28 bacterial strains were isolated from the bioremediation experiment, cultured, genetically characterized for identification and screened for production of the auxin phytohormone indole-3-acetic acid (IAA). Metabarcoding showed that the free-living bacterial community consisted of bacteria from both the wastewater effluent and the algal inocula, while the attached phycosphere community was dominated by bacteria from the algal inocula, indicating the stability of the algae-associated phycosphere. Taxa known to include plant growth-promoting bacteria (PGPB) were abundant, and several strains produced IAA. The bacterial community composition, combined with the potential production of phytohormone by isolated bacteria indicates symbiotic or commensal algae-microbe interactions within the phycosphere bacterial communities. Sterile filtration of wastewater effluent, including only the algal inoculum bacterial communities, reduced algal biomass production and increased bacterial abundance. This study highlights the critical role of microbial interactions in engineered ecosystems and provides insights for optimizing algal-based wastewater treatment technologies.
Authors
Ralf Rautenberger Alexandre Detain Kari Skjånes Peter Simon Claus Schulze Viswanath Kiron Daniela Morales-SánchezAbstract
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Division of Biotechnology and Plant Health
Microalgae contributions to future protein and fatty acid rich feed for Norwegian chicken at industrial scale - ALGEKYLLING
The main goal of the project is to create a knowledge and technology platform for production and use of chicken feed with proteins and polyunsaturated fatty acids (PUFA) from Norwegian microalgae biomass. The project consortium includes the whole production/value chain.
Division of Biotechnology and Plant Health
MikRho - Establishing Rhodomonas culture with beneficial microbiome adapted to industrial production
As one of the largest microalgae producers in Norway, CFEED contributes to sustainable feed solutions through its production of microalgae and the copepod