15 N may reveal algal and bacterial role

Our second set of flume experiments used 15N-NO3 to follow nitrogen uptake into different organismic groups in benthic biofilms. Currently, our samples are frozen while Boku Tulln is establishing a method to analyse 15 N in amino acids specific for algae and bacteria. The analyses of our samples are planned for early summer.

In addition, we have conducted short-term plateau SRP and NH4 field additions in 3 agricultural streams in summer 2021. Each stream had three 100m-long reaches: one control, one with biochar bags, and one with woodchip bags. To reduce interference, reaches were ordered randomly for each addition (2 per stream). Our aim was to analyse whether woodchip bags would increase N and P uptake in small nutrient polluted and morphologically degraded streams in agricultural catchment compared to non-treated reaches and reaches with biochar bags. Our first results show that both biochar and woodchips could improve P uptake but not NH4.

Kick-off meeting

Finally, after almost one year delay (waiting for an opportunity to meet in person), we had an online kick-off meeting on February 10. At least, we could look at the first results of 2020 and plan the sampling and the experiments accordingly for 2021.

Flume experiment started

Our first flume experiments started in November. We colonized biofilms under dark conditions and exposed them to nutrients with and without leaves. Preliminary results show that leaves stimulate heterotrophic P and N uptake.

Field sampling

Our field sampling in Lower Austria has started, comparing different headwater streams with and without riparian buffers and riparian forests. We investigated P uptake, P release, and respiration in the sediments.