es6b06296_si_001.pdf (269.3 kB)
Community Biological Ammonium Demand: A Conceptual Model for Cyanobacteria Blooms in Eutrophic Lakes
journal contribution
posted on 2017-06-24, 00:00 authored by Wayne S. Gardner, Silvia E. Newell, Mark J. McCarthy, Daniel K. Hoffman, Kaijun Lu, Peter J. Lavrentyev, Ferdi L. Hellweger, Steven W. Wilhelm, Zhanfei Liu, Denise A. Bruesewitz, Hans W. PaerlCyanobacterial
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.