Environmental variability drives phytoplankton assemblage persistence in a subtropical reservoir
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2011-11
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Resumo
Temporal changes of assemblages may result from environmental variability and reflect seasonal
dynamics of their ecosystem. In the subtropics, the hydrological regime is usually characterized by well-defined wet
and dry seasons, regulating discharge and influencing a series of environmental variables that affect phytoplankton
persistence. Therefore, we may expect that dry seasons are environmentally more stable than wet seasons. We
analysed interannual phytoplankton assemblage variability (or, inversely, persistence) in a subtropical reservoir
sampled every austral summer and winter during 5 years. We tested (i) if phytoplankton assemblage structure
differed between the dry (summer) and wet (winter) seasons; (ii) if assemblage persistence differed between the
seasons; (iii) if assemblage persistence was related to environmental stability; and (iv) if assemblage dissimilarity
increased over time. Phytoplankton assemblages differed between the summer and winter seasons.Winter indicator
species were mostly Bacillariophyceae or Cryptophyceae, whereas Cyanophyceae and Chlorophyceae taxa were
more frequent and abundant in summer. Assemblages in the dry season were more persistent among years than
those occurring during rainy periods. Similarly, environmental variability tended to be lower among dry than among
rainy seasons. The relation between the phytoplankton temporal cycle and the temporal patterns of environmental
variability supports our prediction that high environmental stability results in more persistent assemblages.
Assemblage dissimilarity increased as sampling years were farther apart, for both seasons. Additionally, assemblages
in the rainy periods showed a more pronounced increase in dissimilarity, as their changes among years were less
predictable. We found a clear temporal pattern and an increased dissimilarity over time in the phytoplankton
assemblage structure. Unravelling these temporal patterns may improve our understanding of phytoplankton
temporal dynamics, and may have implications for management and monitoring programs. High dissimilarity of
assemblages among years, particularly among rainy periods, can obscure human impacts, and monitoring programs
should take this into account.
Descrição
v. 36, p. 839-848, nov. 2011.
Palavras-chave
Algae, Interannual variability, Plankton, Seasonality, Temporal stability
Citação
SCHNECK, Fabiana; RODRIGUES, Silvana C.; SCHWARZBOLD, Albano; MELO, Adriano S. Environmental variability drives phytoplankton assemblage persistence in a subtropical reservoir. Austral Ecology, v. 36, p. 839-848, Nov. 2011. Disponível em: <http://onlinelibrary.wiley.com/doi/10.1111/j.1442>.