Phytoplankton functional groups for ecological assessment in young sub-tropical reservoirs: case study of the Nam-Theun 2 Reservoir, Laos, South-East Asia

  • Joanna Martinet Nam Theun 2 Power Company Limited (NTPC), Environment & Social Division – Water Quality and Biodiversity Dept.– Aquatic Environment Lab, Lao People's Democratic Republic.
  • Stéphane Descloux EDF, Hydro Engineering Centre – Savoie Technolac, France.
  • Pierre Guédant Nam Theun 2 Power Company Limited (NTPC), Environment & Social Division – Water Quality and Biodiversity Dept.– AE Lab, Lao People's Democratic Republic.
  • Frederic Rimet | frederic.rimet@thonon.inra.fr Institut National pour la Recherche en Agriculture (INRA), France.

Abstract

The early stages following the creation of reservoirs are typically physical and biological unstable periods due to the conversion from a lotic to a lentic ecosystem. The sub-tropical Nam Theun 2 Reservoir (Laos) was impounded in 2008. Several limnological parameters were monitored from March 2009 to December 2011 in order to understand the evolution of the phytoplankton community. A strong inter annual variability of hydrodynamic pattern was observed. Rainfall and hydraulic balance were the main physical factors driving the community structure. Periods of highest hydraulic stability led to a phytoplankton biomasses increase. The first assemblages were dominated by the S-C-strategists reaching high biomasses but low diversity. Over the three years, phytoplankton became more diverse due to a diversification of ecological niches, mostly explained by a greater water transparency and a more stable thermal stratification. The applicability of functional groups for biomonitoring in this young sub-tropical reservoir was investigated and compared to a classical taxonomical approach. The dominant functional groups (Lo, A, E, F, N and P) characterized the NT2 Reservoir as meso-oligotrophic with a tolerance to low nutrients supply. Our results support the hypothesis that a functional group approach is more informative than a species-based approach to assess trophic level and dissolved organic carbon concentrations in such reservoirs.

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Published
2014-05-15
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Original Articles
Keywords:
phytoplankton biomass, functional groups succession, young sub-tropical reservoir, trophic level.
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How to Cite
1.
Martinet J, Descloux S, Guédant P, Rimet F. Phytoplankton functional groups for ecological assessment in young sub-tropical reservoirs: case study of the Nam-Theun 2 Reservoir, Laos, South-East Asia. J Limnol [Internet]. 2014May15 [cited 2021May6];73(3). Available from: https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2014.958