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Impacts of nutrient loading and fish grazing on the phytoplankton community and cyanotoxin production in a shallow tropical lake: Results from mesocosm experiments
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  • Mathias Koffi Ahoutou,
  • Eric Kouamé Yao,
  • Rosine Yao Djeha,
  • Mamadou Kone,
  • Kevin Tambosco,
  • Charlotte Duval,
  • Sahima Hamlaoui,
  • Cécile Bernard,
  • Marc Bouvy,
  • Benjamin Marie,
  • Bernard Montuelle,
  • Marc Troussellier,
  • Felix Koffi Konan,
  • Mireille Dosso,
  • Jean-François Humbert,
  • Catherine Quiblier,
  • Julien Kalpy
Mathias Koffi Ahoutou
Institut Pasteur d’Abidjan

Corresponding Author:[email protected]

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Eric Kouamé Yao
Institut Pasteur d’Abidjan
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Rosine Yao Djeha
Institut Pasteur d’Abidjan
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Mamadou Kone
Institut Pasteur d’Abidjan
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Kevin Tambosco
INRAE-Sorbonne Université
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Charlotte Duval
MNHN
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Sahima Hamlaoui
MNHN
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Cécile Bernard
MNHN
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Marc Bouvy
Université de Montpellier
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Benjamin Marie
MNHN
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Bernard Montuelle
INRAE-Université de Savoie
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Marc Troussellier
Université de Montpellier
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Felix Koffi Konan
Université Jean Lorougnon Guédé
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Mireille Dosso
Institut Pasteur d’Abidjan
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Jean-François Humbert
INRAE-Sorbonne Université
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Catherine Quiblier
MNHN
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Julien Kalpy
Centre Nationale de Référence de Salmonella, Laboratoire de Bactériologie et Virologie Institut Pasteur de Côte d'Ivoire
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Abstract

Given the increasing eutrophication of water bodies in Africa due to increasing anthropogenic pressures, data are needed to better understand the responses of phytoplankton communities to these changes in tropical lakes. These ecosystems are used by local human populations for multiple purposes, including fish and drinking water production, potentially exposing these populations to health threats if, for example, an increase in toxic cyanobacterial blooms is associated with increasing eutrophication. To test the short-term response of the phytoplankton community to the addition of nutrients (phosphorus and nitrogen, alone or in combination) and Nile tilapia, we developed an in situ mesocosm experiment in a freshwater lagoon located near Abidjan (Ivory Coast). We found that phytoplankton growth (estimated by chlorophyll-a quantification) was highly stimulated when both nitrogen and phosphorus were added, while there was no clear evidence for such colimitation by these two nutrients when considering their concentrations in the lagoon. Phytoplankton growth was accompanied by significant changes in the diversity and composition of this community and did not lead to an increase in the proportions of cyanobacteria. However, the addition of fish to some mesocosms resulted in a drastic decrease in phytoplankton biomass and a dominance of chlorophytes in this community. Finally, these experiments showed that the addition of nitrogen, alone or combined with phosphorus, stimulated microcystin production by cyanobacteria. In addition, no evidence for microcystin accumulation in the fish was found. Taken together, these data allow us to discuss strategies for controlling cyanobacterial blooms in this tropical ecosystem.
11 Oct 2021Submitted to MicrobiologyOpen
11 Oct 2021Submission Checks Completed
11 Oct 2021Assigned to Editor
13 Oct 2021Reviewer(s) Assigned
15 Nov 2021Review(s) Completed, Editorial Evaluation Pending
16 Nov 2021Editorial Decision: Revise Major
10 Feb 20221st Revision Received
15 Feb 2022Submission Checks Completed
15 Feb 2022Assigned to Editor
15 Feb 2022Review(s) Completed, Editorial Evaluation Pending
15 Feb 2022Reviewer(s) Assigned
14 Mar 2022Editorial Decision: Accept
Apr 2022Published in MicrobiologyOpen volume 11 issue 2. 10.1002/mbo3.1278