Interactions between flow hydrodynamics and biofilm attributes and functioning in streams
Final Report Abstract
Biofilms, i.e. surface-associated microbial communities that are embedded in a matrix of extracellular substances, constitute an integral component of the food web and biogeochemical cycling in lotic aquatic ecosystems. The architecture, biomass, diversity, community structure and functioning of stream biofilms are controlled by many factors including light, grazing, resource availability, water chemistry and hydro-morphology. In lotic aquatic ecosystems, the heterogeneous streambed composed of varying grain sizes (boulders to sand) leads to high spatio-temporal variability of the flow field. In a novel approach, we successfully linked detailed investigations on near streambed morphologic and flow diversity in mountainous streams to biofilm attributes and function (nitrogen uptake). As part of this project, we developed a new concept to express the near streambed flow and morphologic diversity based on common ecological theory of biodiversity. We applied this concept to analyze the relationships between near streambed flow and the hydraulic diversity and biofilm attributes and function at various spatial scales. In the field surveys we focused on the following hypotheses: (1) increased stream bed heterogeneity leads to higher spatiotemporal diversity of hydraulic parameters and conditions, (2) near streambed turbulence is important in explaining the variability in composition and architecture of the epilithic biofilms, (3) hydraulic habitat diversity (β- and γ-diversity of flow) and diversity of prokaryotes and micro-eukaryotes are positively correlated, (4) nitrogen uptake of epilithic stream biofilms increases with near streambed turbulence, and (5) nitrogen uptake is driven by biofilm biomass rather than biofilm diversity. In addition to the field studies, hydraulic flumes were developed and used in stream side mesocosm experiments to test the above hypotheses under controlled conditions. At the micro-scale, near streambed flow characteristics affected biofilm composition, community structure and architecture despite the multitude of other environmental factors that act on stream biofilms. Both approaches, the field surveys and the mesocosm flume experiment, demonstrated that the nitrogen uptake efficiency was controlled by near streambed turbulent flow. At sites with high near streambed turbulent flow, biofilms had less Chl a, less biomass, larger organic content and covered a larger surface area. Biofilms grown under this turbulent flow condition had the highest nitrogen uptake efficiency, thus they seem to be more efficient in nutrient retention at the micro-scale. The missing correlation between prokaryotic diversity and nitrogen uptake efficiency supported our hypothesis that niches overlap within the diverse community of stream biofilms leading to functional redundancy and N uptake of biofilms saturated. In order to upscale the results from the micro-scale, we successfully described the flow and morphologic diversity and tackled their interactions at increasing spatial scales. About 33 % of the regional morphologic diversity (γ-diversity) explained variations around the mean flow (β-diversity). A higher hydraulic β-diversity predicted a higher β-diversity of biofilm prokaryotes and algae, but not of mobile protozoans. Hence, there was a strong link between the physical niches created by the hydraulic diversity and the diversity of attached biofilm constituents as prokaryotes and algae. Overall, the project successfully characterized the linkage between streambed morphology and flow conditions on biofilms in mountainous streams and revealed pronounced effects on biofilm-mediated processes. By developing novel concepts on flow diversity and by developing novel approaches and tools for experiments and field surveys, we provide a basis for future studies about hydraulic effects on communities and biological processes in streams.
Publications
- (2015) Morphological controls on stream metabolism and reactive solute transport. Goldschmidt Symposium, Prague, Czech Republic
Kurz, M.J., Schmidt, C., Anlanger, C. & Risse-Buhl, U.
- (2016) Effect of hydrodynamics on microbial biofilm communities revealed by insitu measurements in mountaineous streams. Society of Freshwater Sciences, Sacramento, USA
Risse-Buhl, U., Anlanger, C., Kalla, K., Neu, T. R., Noss, C., Chatzinotas, A., Lorke, A. & Weitere, M.
- (2016) The effect of hydrodynamics on protozoans within stream biofilms. Annual meeting of the German Society of Protozoology, Saignelégeir, Switzerland
Risse-Buhl, U., Anlanger, C., Noss, C., Lorke, A., Neu, T. R. & Weitere, M.
- (2017) Herbicide sensitivity of stream biofilms grown at contrasting hydrodynamic conditions - a mesocosm study. Symposium of European Freshwater Sciences, Oloumouc, Czech Republic
Polst, B., Anlanger, C., Risse-Buhl, U., Weitere, M. & Schmitt-Jansen, M.
- (2017) Hydrodynamic heterogeneity keeps epilithic biofilm diversity high in fluvial ecosystems. Symposium of European Freshwater Sciences, Oloumouc, Czech Republic
Risse-Buhl, U., Anlanger, C., Chatzinotas, A., Noss, C., Lorke, A. & Weitere, M.
- (2017) Performance of the Vectrino Profiler at the sediment – water interface. Journal of Hydraulic Engineering-Asce, 55, 573- 581
Koca, K., Noss, C., Anlanger, C., Brand, A., Lorke, A.
(See online at https://doi.org/10.1080/00221686.2016.1275049) - (2017) Spatial scales of hydraulic and morphological habitat diversity in gravel bed streams. Meeting of the Association for the Sciences of Limnology and Oceanography, Hawaii
Anlanger, C., Noss, C., Weitere, M., Risse-Buhl, U. & Lorke, A.
- (2017) The role of hydrodynamics in shaping the composition and architecture of epilithic biofilms in fluvial ecosystems. Water Research, 127, 211-222
Risse-Buhl, U., Anlanger, C., Kalla, K., Neu, T.R., Noss, C., Lorke, A. & Weitere, M.
(See online at https://doi.org/10.1016/j.watres.2017.09.054) - (2018) Stress-induced community tolerance of stream biofilms grown at contrasting hydrodynamic conditions. Annual Meeting of the Society of Environmental Toxicology and Chemistry, Rome, Italy
Polst, B., Larras, F., Lips, S., Anlanger, C., Risse-Buhl, U., Weitere, M. & Schmitt-Jansen, M.
- (2018). Triangulation hand-held laser-scanning (TriHaLaS) for micro- and meso-habitat surveys in streams. Earth Surface Processes and Landforms
Noss, C., Wilkinson, J. & Lorke, A.
(See online at https://doi.org/10.1002/esp.4310)
