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Uptake rates of ammonium and nitrate by phytoplankton communities in two eutrophic tropical reservoirs
Author(s) -
Gasparini Fernandes Cunha Davi,
Fernandes de Melo Lima Vitória,
Menegante Néri Amanda,
Albino Marafão Gabriela,
Cristina Poli Miwa Adriana,
do Carmo Calijuri Maria,
Albertino Bendassoli José,
Tromboni Flavia,
Maranger Roxane
Publication year - 2017
Publication title -
international review of hydrobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 1434-2944
DOI - 10.1002/iroh.201701900
Subject(s) - eutrophication , phytoplankton , nitrate , cyanobacteria , environmental chemistry , ammonium , nutrient , biology , temperate climate , algae , biomass (ecology) , ecology , environmental science , chemistry , genetics , organic chemistry , bacteria
While excess phosphorus typically results in the eutrophication of inland waters, there is growing evidence that excess nitrogen (N) and the availability of different N forms influence phytoplankton community composition, often favoring potentially toxic genera. In this study, the environmental dynamics, phytoplankton community structure, and N uptake rates were investigated in two tropical reservoirs. Phytoplankton ammonium (N H 4 + ) and nitrate (N O 3 − ) acquisition was assessed through 15 N addition experiments over 2 years. We found that changes in ambient nutrient concentrations and temperature influenced different phytoplankton groups, which tended to have different N uptake strategies. The preferred N‐source by Cyanobacteria wasN H 4 +while Dinophyceae and other groups seemed adapted to also take upN O 3 − , possibly due to competition. Potential uptake rates (maximum of 8.5 μM‐N hr −1 forN H 4 +and 1.3 μM‐N hr −1 forN O 3 − ) were high in comparison to previous reports from temperate freshwater or marine systems, likely due to elevated algal biomass and temperature. When normalized to biomass as chlorophyll‐a (Chl‐a), specific uptake rates varied between 0.01–3.4 μmol‐N μgChl‐a −1 day −1 forN H 4 +and <0.01–0.8 μmol‐N μgChl‐a −1 day −1 forN O 3 −and were comparable to those reported for other eutrophic and hypereutrophic aquatic systems. In addition, higher temperatures favored Cyanobacteria (e.g., Cylindrospermopsis raciborskii and Microcystis aeruginosa ), while a more diverse community was found during colder months. Results highlight how high loading of reduced forms of nitrogen and high temperatures can exacerbate harmful Cyanobacteria blooms in tropical reservoirs and be a concern for drinking water quality.