title: Termination of a toxic Alexandrium bloom with hydrogen peroxide.
abstract: The dinoflagellate Alexandrium ostenfeldii is a well-known harmful algal species that can potentially cause paralytic shellfish poisoning (PSP). Usually A. ostenfeldii occurs in low background concentrations only, but in August of 2012 an exceptionally dense bloom of more than 1millioncellsL-1occurred in the brackish Ouwerkerkse Kreek in The Netherlands. The A. ostenfeldii bloom produced both saxitoxins and spirolides, and is held responsible for the death of a dog with a high saxitoxin stomach content. The Ouwerkerkse Kreek routinely discharges its water into the adjacent Oosterschelde estuary, and an immediate reduction of the bloom was required to avoid contamination of extensive shellfish grounds. Previously, treatment of infected waters with hydrogen peroxide (H2O2) successfully suppressed cyanobacterial blooms in lakes. Therefore, we adapted this treatment to eradicate the Alexandrium bloom using a three-step approach. First, we investigated the required H2O2dosage in laboratory experiments with A. ostenfeldii. Second, we tested the method in a small, isolated canal adjacent to the Ouwerkerkse Kreek. Finally, we brought 50mgL-1of H2O2into the entire creek system with a special device, called a water harrow, for optimal dispersal of the added H2O2. Concentrations of both vegetative cells and pellicle cysts declined by 99.8% within 48h, and PSP toxin concentrations in the water were reduced below local regulatory levels of 15μgL-1. Zooplankton were strongly affected by the H2O2treatment, but impacts on macroinvertebrates and fish were minimal. A key advantage of this method is that the added H2O2decays to water and oxygen within a few days, which enables rapid recovery of the system after the treatment. This is the first successful field application of H2O2to suppress a marine harmful algal bloom, although Alexandrium spp. reoccurred at lower concentrations in the following year. The results show that H2O2treatment provides an effective emergency management option to mitigate toxic Alexandrium blooms, especially when immediate action is required.
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94248, Amsterdam 1090 GE, The Netherlands.
authors.forename: Amanda
authors.initials: A
authors.lastname: Burson
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94248, Amsterdam 1090 GE, The Netherlands.
authors.forename: Hans C P
authors.initials: HC
authors.lastname: Matthijs
authors.affiliation: Arcadis Netherlands BV, Het Rietveld 59a, 7321 CT Apeldoorn, The Netherlands.
authors.forename: Wilco
authors.initials: W
authors.lastname: de Bruijne
authors.affiliation: Arcadis Netherlands BV, Het Rietveld 59a, 7321 CT Apeldoorn, The Netherlands.
authors.forename: Renee
authors.initials: R
authors.lastname: Talens
authors.affiliation: RIKILT Wageningen UR, Akkermaalsbos 2, Building 123, 6708 WB Wageningen, The Netherlands.
authors.forename: Ron
authors.initials: R
authors.lastname: Hoogenboom
authors.affiliation: RIKILT Wageningen UR, Akkermaalsbos 2, Building 123, 6708 WB Wageningen, The Netherlands.
authors.forename: Arjen
authors.initials: A
authors.lastname: Gerssen
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94248, Amsterdam 1090 GE, The Netherlands.
authors.forename: Petra M
authors.initials: PM
authors.lastname: Visser
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94248, Amsterdam 1090 GE, The Netherlands.
authors.forename: Maayke
authors.initials: M
authors.lastname: Stomp
authors.affiliation: Waterschap Scheldestromen, PO Box 1000, 4330 ZW Middelburg, The Netherlands.
authors.forename: Kees
authors.initials: K
authors.lastname: Steur
authors.affiliation: Waterschap Scheldestromen, PO Box 1000, 4330 ZW Middelburg, The Netherlands.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: van Scheppingen
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94248, Amsterdam 1090 GE, The Netherlands. Electronic address: j.huisman@uva.nl.
authors.forename: Jef
authors.initials: J
authors.lastname: Huisman
keywords: Alexandrium ostenfeldii; Coastal management; Harmful algal blooms; Hydrogen peroxide; Saxitoxin; Spirolides