Multiple-stressor effects of dicyandiamide (DCD) and agricultural stressors on trait-based responses of stream benthic algal communities

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Abstract

Agricultural practices often result in multiple stressors affecting stream ecosystems, and interacting stressors complicate environmental assessment and management of impacted streams. The nitrification inhibitor dicyandiamide (DCD) is used for nitrogen management on farmland. Effects of leached DCD on stream ecosystems are still largely unstudied, even though it could be relevant as a stressor on its own or in combination with other agricultural stressors. We conducted two experiments in 128 outdoor stream-fed mesocosms to assess stressor effects on biomass, cell density, taxon richness, evenness and functional trait composition of benthic algal communities. First, we examined responses to a wide DCD gradient (eight concentrations, 0–31 mg L−1) and two additional stressors, deposited fine sediment (none, high) and nutrient enrichment (ambient, enriched). Second, we determined algal responses to four stressors: DCD, sediment, nutrients, and reduced flow velocity. Here DCD treatments included controls, constant application (1.4 mg L−1) and two pulsed treatments mimicking concentration patterns in real streams (peaks 3.5 mg L−1, 2.2 mg L−1). Sediment and nutrient enrichment were influential stressors in both experiments, with fine sediment having the most pervasive effects. In Experiment 2, reduced flow velocity had pervasive effects and stressor interactions were mainly restricted to two-way interactions. DCD had few, weak stressor main effects, especially at field-realistic concentrations (Experiment 2). At the highest concentrations in Experiment 1 (above levels observed in real streams), DCD effects were still rare but some significant stressor interactions occurred. Analyses of functional traits were helpful in identifying potential mechanisms driving changes in densities and community composition. These findings suggest that, while DCD on its own may be a minor stressor, it could have adverse effects on algal communities already exposed to other stressors, a scenario common in agricultural streams.

Detaljer

Författare
  • Romana K. Salis
  • Andreas Bruder
  • Jeremy J. Piggott
  • Tina C. Summerfield
  • Christoph D. Matthaei
Externa organisationer
  • University of Otago
  • University of Duisburg-Essen
  • University of Applied Sciences and Arts of Southern Switzerland
  • Trinity College Dublin
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Ekologi

Nyckelord

Originalspråkengelska
Artikelnummer133305
TidskriftScience of the Total Environment
Volym693
StatusPublished - 2019 nov 25
PublikationskategoriForskning
Peer review utfördJa
Externt publiceradJa