Aarhus Universitets segl

Per Andersen

The impact of urea on toxic diatoms – Potential effects of fertilizer silo breakdown on a Pseudo-nitzschia bloom

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  • Anna Karoline Junker Olesen, Københavns Univ, SNM, Danmark
  • Sara Harðardóttir, Københavns Universitet, Danmarks Tekniske Universitet, Danmark
  • Niels Daugbjerg, Københavns Universitet
  • ,
  • Per Andersen
  • Maren Moltke Lyngsgaard, Danmark
  • Bernd Krock, Alfred Wegener Institute - Helmholtz Centre for Polar and Marine Research, Danmark
  • Nina Lundholm, Københavns Univ, SNM, Danmark
In spring 2016, two silos containing liquid nitrogen-containing fertilizer collapsed on a harbor in Fredericia, Denmark. More than 2,750 tons of fertilizer spilled into inner Danish waters. A bloom of Pseudo-nitzschia occurred approximately one month after the incident. The bloom caused a 5-week quarantine of numerous mussel-harvesting areas along the eastern coast of Jutland. The levels of domoic acid measured up to 49 mg kg−1 in mussel meat after the bloom. In the months following the event, the species diversity of phytoplankton was low, while the abundance was high comprising few dominant species including Pseudo-nitzschia. The main part of the liquid nitrogen-containing compound was urea, chemically produced for agricultural use. To investigate the potential impact of urea on Pseudo-nitzschia, four strains, including one strain of P. delicatissima, two of P. seriata and one of P. obtusa, were exposed each to three concentrations of urea in a batch culture experiment: 10 μM, 20 μM and 100 μM N urea, and for comparison one concentration of nitrate (10 μM). Nitrate, ammonium, and urea were metabolized at different rates. Pseudo-nitzschia obtusa produced domoic acid and grew best at low urea concentrations. Both P. seriata strains had a positive correlation between urea concentration and growth rate, and the highest growth rate in the nitrate treatment. One strain of P. seriata produced domoic acid peaking at low N loads (10 µM N urea and 10 µM N nitrate). In conclusion, the ability to adapt to the available nitrogen source and retain a high growth rate was exceedingly varying and not only species-specific but also strain specific.
TidsskriftHarmful Algae
Antal sider12
StatusUdgivet - 2020
Eksternt udgivetJa


  • Domoic acid, Fertilizer spill, Harmful algal bloom, Nitrogen, Pseudo-nitzschia, Urea

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