Gardner, Wayne S., Newell, Silvia E., McCarthy, Mark J., Hoffman, Daniel K., Lu, Kaijun, Lavrentyev, Peter J., Hellweger, Ferdi L., Wilhelm, Steven W., Liu, Zhanfei, Bruesewitz, Denise A. and Paerl, Hans W. (2017) Community biological ammonium demand: a conceptual model for cyanobacteria blooms in eutrophic lakes. Environmental Science & Technology, 51 (14). pp. 7785-7793. DOI 10.1021/acs.est.6b06296.

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Abstract

Cyanobacterial harmful algal blooms (CyanoHABs) are enhanced by anthropogenic pressures, including excessive nutrient (nitrogen, N, and phosphorus, P) inputs and a warming climate. Severe eutrophication in aquatic systems is often manifested as non-N2-fixing CyanoHABs (e.g., Microcystis spp.), but the biogeochemical relationship between N inputs/dynamics and CyanoHABs needs definition. Community biological ammonium (NH4+) demand (CBAD) relates N dynamics to total microbial productivity and NH4+ deprivation in aquatic systems. A mechanistic conceptual model was constructed by combining nutrient cycling and CBAD observations from a spectrum of lakes to assess N cycling interactions with CyanoHABs. Model predictions were supported with CBAD data from a Microcystis bloom in Maumee Bay, Lake Erie, during summer 2015. Nitrogen compounds are transformed to reduced, more bioavailable forms (e.g., NH4+ and urea) favored by CyanoHABs. During blooms, algal biomass increases faster than internal NH4+ regeneration rates, causing high CBAD values. High turnover rates from cell death and remineralization of labile organic matter consume oxygen and enhance denitrification. These processes drive eutrophic systems to NH4+ limitation or colimitation under warm, shallow conditions and support the need for dual nutrient (N and P) control.

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