Diatoms as an indicator for tile drainage flow in a German lowland catchment

Naicheng Wu, Claas Faber, Uta Ulrich, Nicola Fohrer

The separation of runoff components within a model simulation is of great importance for a successful implementation of management measures. Diatoms could be a promising indicator for tile drainage flow due to their diverse preferences to different aquatic habitats. In this study, we collected diatom samples of 9 sites (4 tile drainage, TD, and 5 river sites, Ri) in a German lowland catchment at a weekly or biweekly time step from March to July 2013 with the aim of testing the suitability of diatoms for tile drainage flow, which is typical for lowland catchment. Planothidium lanceolatum ,Ulnaria biceps, andNavicula gregariadominated in TD sites with relative abundances of 22.2, 21.5, and 10.9%, respectively. For Ri sites, the most abundant species wasNavicula lanceolata(20.5%), followed byUlnaria biceps(12.9%),Cyclotella meneghiniana(9.5%), andPlanothidium lanceolatum(9.3%). Compared with Ri sites, TD had a lower diatom density, biomass, species richness, and percentage of Aquatic/Riparian diatoms (AqRi%). However, the proportion of Riparian diatoms (RiZo%) increased at TD. Indicator value method (IndVal) revealed that the two groups (Ri and TD) were characterized by different indicator species. Fifteen taxa, includingCocconeis placentula,Cyclotella meneghiniana,N. lanceolata, andU. biceps, were significant indicators for Ri sites.Planothidium lanceolatum,Achnanthidium minutissimum, andNavicula gregariawere significant indicators for TD sites. A pronounced variation was found in the species lists of diatom community between Ri and TD water body types associated with different indicator species. With respect to hydrograph separation, these findings highlight the suitability of diatoms as an indicator for tile drainage flow. However, spatial and temporal variations of diatoms should be considered in future surveys.