Organic carbon cycling in streams

Project: Organic carbon cycling in streams: Effects of agricultural land use

Agriculture is the dominant land use form in Lower Austria, covering more than 46 % of the total area. Agriculture delivers significant amounts of dissolved organic matter (DOM) to streams, thereby changing basic processes at the water-sediment interface and affecting the ecological state of the stream ecosystem. The aim of the project is to investigate the influence of agricultural land use on the quantity and quality of DOM inputs to streams and to clarify the effects of this DOM on the aquatic carbon cycling in stream ecosystems.

Our research will be based on both in-situ determinations of DOM quality and stream processes in the Hydrological Open Air Laboratory (HOAL) in Petzenkirchen, a priority area for the FTI strategy of Lower Austria, and on laboratory experiments at the WasserCluster Lunz and the Bundesamt für Wasserwirtschaft (Petzenkirchen). In microlysimeter experiments, we will study the effects of different agricultural practices (e.g. fertilization, tillage) on the amount and composition of DOM delivered to fast-draining near-surface flow paths. In the HOAL catchment, we will measure the impact of different flow paths, such as surface runoff, tile drainage and groundwater, on the DOM input during baseflow and stormflow conditions. Via flume experiments, we will investigate the effects of different DOM sources on the growth and activity of benthic microorganisms, the oxygen consumption in the stream, and the aquatic emission of greenhouse gases. The results will be analyzed with respect to consequences of DOM inputs from agricultural areas for the health and the ecological state of stream ecosystems and will be incorporated into recommendations for a sustainable management of agricultural streams.

In addition, the Center for Integrated Sensors Systems at the Danube University Krems will develop a sensor for the in-situ determination of DOM in freshwater to be used in both scientific research and water quality monitoring. At present, DOM analyses in freshwater studies mostly rely on water sample analyses in the laboratory, limiting sampling frequency and affecting data quality. In-field DOM sensors with a high temporal resolution will facilitate the tracking of DOM changes over time, e.g. in response to variations in biotic activities or hydrology, and will, thus, enable a detailed insight into DOM dynamics. In the case of water quality monitoring, DOM sensors could be used to detect organic pollution, such as diesel oil, farm leakage, or sewage inputs, and as early-warning systems of failure in water quality.

The project is funded by the Provincial Government of Lower Austria within the Science Call 2015.