Ammonium treatments to suppress toxic blooms of Prymnesium parvum in a subtropical lake of semi-arid climate: Results from in situ mesocosm experiments

• Published in: Water research (Oxford) 2013-09, Vol.47 (13), p.4274-4285
• Main Authors: Grover, James P., Roelke, Daniel L., Brooks, Bryan W., Gable, George M., Neisch, Michael T., Hayden, Natanya J., Valenti, Theodore W., Prosser, Krista N., Umphres, George D., Hewitt, Natalie C.
• Format: Article
• Language: English
• Subjects: Ammonium; Ammonium Compounds - analysis; Ammonium Compounds - pharmacology; Analysis of Variance; Animals; Applied sciences; aquaculture; Biomass; Daphnia - drug effects; Desert Climate; eutrophication; Eutrophication - drug effects; Exact sciences and technology; Haptophyta - drug effects; Harmful algal blooms; Hydrogen-Ion Concentration - drug effects; Lakes; Nitrates - analysis; Nitrites - analysis; nitrogen; Nitrogen - analysis; Phosphorus - analysis; Pollution; ponds; Prymnesium; Prymnesium parvum; Reservoirs; risk; semiarid zones; Texas; toxicity; Toxicity Tests, Acute; Tropical Climate; Water treatment and pollution; Zooplankton
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2013.05.001

Prymnesium parvum is a haptophyte alga that forms toxic, fish-killing blooms in a variety of brackish coastal and inland waters. Its abundance and toxicity are suppressed by ammonium additions in laboratory cultures and aquaculture ponds. In a cove of a large reservoir (Lake Granbury, Texas, USA) with recurring, seasonal blooms of P. parvum, ammonium additions were tested in mesocosm enclosures for their ability to suppress blooms and their effects on non-target planktonic organisms. One experiment occurred prior to the peak abundance of a P. parvum bloom in the cove, and one encompassed the peak abundance and decline of the bloom. During 21-day experiments, weekly doses raised ammonium concentrations by either 10 or 40 μM. The added ammonium accumulated in experimental mesocosms, with little uptake by biota or other losses. Effects of ammonium additions generally increased over the course of the experiments. The higher ammonium dose suppressed the abundance and toxicity of P. parvum. The biomass of non-haptophyte algae was stimulated by ammonium additions, while positive, negative and neutral effects on zooplankton taxa were observed. Low ammonium additions insufficient to control P. parvum exacerbated its harmful effects. Our results indicate a potential for mitigating blooms of P. parvum with sufficient additions of ammonium to coves of larger lakes. However, factors excluded from mesocosms, such as dilution of ammonium by water exchange and sediment ammonium uptake, could reduce the effectiveness of such additions, and they would entail a risk of eutrophication from the added nitrogen. [Display omitted] •Ammonium additions to control Prymnesium parvum blooms were tested in the field.•Enclosures experiments were done during bloom initiation and bloom decline.•In both phases, weekly ammonium doses of 40 mM reduced abundance and toxicity.•These ammonium doses had few effects on non-target planktonic organisms.