University of Natural Resources and Life Sciences, Vienna, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; WasserCluster Lunz - Biological Station GmbH, Dr Carl Kupelwieser Promenade 5, 3293 Lunz am See, Austria.
CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Sci Total Environ. 2018 Jul 1;628-629:44-52. doi: 10.1016/j.scitotenv.2018.02.030. Epub 2018 Feb 13.
Our study aimed to explore the effects of agriculture on the phosphorus buffer capacity of 11 headwater streams in Austria. We used phosphorus adsorption curves and re-suspension experiments to determine both, the potential of the sediments to act as phosphorus source or sink and the actual phosphorus exchange between water and sediments. Additionally, we determined the alkaline phosphatase activity (APA) in epilithic and epipsammic biofilms as indicator for the phosphorus demand of the benthic and hyporheic community. We hypothesized that highly polluted streams will show decreased phosphorus buffer capacities, which were either due to saturation or restricted water-sediment interactions. Our results support the second hypothesis. Fine sediment accumulations, organic matter content, and phosphorus concentrations in water and sediments increased with percent cropland in the catchment. Below SRP concentrations of 120μgL in the stream water, sediments showed a high potential for phosphorus release, with zero equilibrium phosphorus concentrations (EPC) being more than twice as high as SRP concentrations. Above 150μgL, EPC reached only 20-50% of SRP concentrations, indicating a high potential of the sediments to act as phosphorus sinks. These findings were confirmed by phosphorus uptake of these sediments during re-suspension. While APA in epilithic biofilms decreased with increasing SRP concentrations, APA in epipsammic biofilms showed the reverse pattern, indicating a restricted phosphorus supply of the hyporheic community despite phosphorus surplus in the water column. Our study shows that inputs of fine sediments from agricultural sources may reduce the phosphorus buffering mechanism of stream sediments through restrictions of water-sediment interactions. Consequently, water column and sediment processes are increasingly decoupled and phosphorus-rich stream water will not effectively reach the reactive sites in the sediments responsible for uptake. Therefore, phosphorus mitigation measures in stream ecosystems must comprise sediment management in the catchment as well as in-stream measures for the rehabilitation of the hyporheic zone.
我们的研究旨在探索农业对奥地利 11 条源头溪流磷缓冲能力的影响。我们使用磷吸附曲线和再悬浮实验来确定沉积物作为磷源或汇的潜力以及水和沉积物之间的实际磷交换。此外，我们还测定了附石和附沙生物膜中的碱性磷酸酶活性（APA），作为底栖和渗流区生物群落磷需求的指标。我们假设高度污染的溪流将表现出降低的磷缓冲能力，这要么是由于饱和或限制了水-沉积物相互作用。我们的结果支持第二个假设。细沉积物积累、有机质含量以及水中和沉积物中的磷浓度随集水区内的农田百分比增加而增加。在溪流水中 SRP 浓度低于 120μgL 时，沉积物表现出很高的磷释放潜力，零平衡磷浓度（EPC）比 SRP 浓度高出两倍多。在 150μgL 以上时，EPC 仅达到 SRP 浓度的 20-50%，表明沉积物具有很高的作为磷汇的潜力。这些发现通过这些沉积物在再悬浮过程中的磷吸收得到了证实。虽然附石生物膜中的 APA 随 SRP 浓度的增加而降低，但附沙生物膜中的 APA 则呈现相反的模式，表明尽管水柱中磷过剩，但渗流区的磷供应受到限制。我们的研究表明，来自农业源的细沉积物输入可能会通过限制水-沉积物相互作用来降低溪流沉积物的磷缓冲机制。因此，水柱和沉积物过程越来越解耦，富磷的溪流水将无法有效地到达负责吸收的沉积物中的反应部位。因此，溪流生态系统中的磷缓解措施必须包括集水区内的沉积物管理以及恢复渗流区的溪流内措施。
