From intermittent to persistent cyanobacterial blooms: identifying the main drivers in an urban tropical reservoir

  • Cleber C. Figueredo Universidade Federal de Minas Gerais (UFMG), Brazil.
  • Ricardo M. Pinto-Coelho Universidade Federal de Minas Gerais (UFMG), Brazil.
  • Ana Maria M.B. Lopes Dept. Botanica, .
  • Pedro H.O. Lima Universidade Federal de Minas Gerais, Brazil.
  • Björn Gücker Universidade Federal de São João del-Rei, Brazil.
  • Alessandra Giani | agiani@icb.ufmg.br Universidade Federal de Minas Gerais (UFMG), Brazil.

Abstract

Eutrophication has impacted water bodies around the world. Knowledge on how to manage and restore these systems is urgently needed in order to maintain adequate water quality. However, causes and consequences of eutrophication may differ among lakes located in tropical and temperate regions. The eutrophication process is better understood for temperate lakes due to the availability of a larger number of studies and longer time-series of data sets. In tropical regions, long-term studies are rare, but could exemplify the particularities of eutrophication speed under conditions of higher temperatures. The purpose of this work was to analyze the evolution of the eutrophication process in an urban tropical reservoir, using a 15-year time series (with occasional interruptions). The dataset comprised monthly sampling of several environmental variables and the phytoplankton community. We found a continuous process of water quality deterioration, mainly related to increasing levels of nutrient and phytoplankton biomass, as well as decreasing water transparency, even after the installation of a municipal wastewater treatment plant. The ongoing eutrophication resulted in a steep trend of increasing cyanobacteria biomass that turned from a seasonal appearance into more persistent blooms in the most recent decades, while the relative contribution of other algal phyla to total phytoplankton biomass declined, which resulted in a loss of phytoplankton diversity. Phosphorus was the major determinant of the persistent blooms. Even though nitrogen concentrations were very high in this system, they were not significantly correlated with phytoplankton or cyanobacteria biomass. Total-P concentrations increased about three times during the study period, indicating that the reservoir did not respond to recent restoration efforts. The average water temperature, always sufficiently high to allow phytoplankton growth all year round, is an additional factor that makes tropical reservoirs especially sensitive to eutrophication. In contrast to temperate systems, the constantly favorable temperatures in the tropics may facilitate the persistence and dominance of cyanobacteria in the plankton community.

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Author Biographies

Cleber C. Figueredo, Universidade Federal de Minas Gerais (UFMG)
Professor, Dept. Botanica
Ricardo M. Pinto-Coelho, Universidade Federal de Minas Gerais (UFMG)
Professor, Dept. Biologia Geral
Ana Maria M.B. Lopes, Dept. Botanica
PhD Student
Pedro H.O. Lima, Universidade Federal de Minas Gerais
Undergraduate Student
Alessandra Giani, Universidade Federal de Minas Gerais (UFMG)
Professor, Dept. Botanica
Published
2016-04-15
Info
Issue
Section
Original Articles
Supporting Agencies
FAPEMIG (Fundação de Amparo a Pesquisa de Minas Gerais), CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico), municipality of the city of Belo Horizonte (MG, Brazil)
Keywords:
Eutrophication, long-term studies, cyanobacteria, bloom stability, tropical reservoirs, wastewater treatment.
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How to Cite
1.
Figueredo CC, Pinto-Coelho RM, Lopes AMM, Lima PH, Gücker B, Giani A. From intermittent to persistent cyanobacterial blooms: identifying the main drivers in an urban tropical reservoir. J Limnol [Internet]. 2016Apr.15 [cited 2020Sep.24];75(3). Available from: https://www.jlimnol.it/index.php/jlimnol/article/view/jlimnol.2016.1330