Environmental modulation of the plankton community composition and size-structure along the eutrophic intertidal coast of the Río de la Plata estuary, Argentina

  • Maximiliano D. Garcia | maxidg6@yahoo.com.ar Instituto Argentino de Oceanografía, Argentina.
  • Nicolás Bonel Universidad Nacional del Sur, Argentina.

Abstract

In this study we investigated the spatial distribution of the plankton community, bacterio-, phyto- and zooplankton, in relation with environmental conditions along the intertidal coast of the Río de la Plata estuary, Argentina. Plankton was analyzed in terms of species composition, abundance, biomass (carbon content) and size-structure. We aim to evaluate the potential effects of anthropogenic impacts (e.g., nutrient enrichment) and physicochemical gradients alongshore (e.g., salinity, turbidity) on the composition and functioning of the plankton. We asked whether the natural structuring of the plankton by salinity and turbidity, known to be true of estuaries, is modified by eutrophication along the studied shoreline. We found that the density and biomass of bacteria and phytoplankton were strikingly enhanced by high eutrophication levels along the intertidal southwest coast of the Río de la Plata estuary. We also found that the highest zooplankton density in the most polluted area but the biomass showed a different distribution pattern. Nevertheless, when zooplankton was analyzed by means of its size fraction, we accordingly found that the microzooplankton biomass was positively associated with smaller-size phytoplankton groups and the most polluted study sites. Copepods were the major taxonomic groups that best represented the mesozooplankton biomass. We therefore expected that its distribution was modulated by the presence of its food items (i.e., large cells) which, in turn, were more abundant in the middle-outer zone. In contrast, we found that the highest biomass of copepods occurred at the innermost site of the estuary and we found no significant association with other planktonic groups. Overall, this study highlights the noteworthy impacts of human activities modifying the functioning of this coastal ecosystem. The differences found in the taxonomic composition and size structure of the planktonic community assemblage between the most polluted and less polluted sites constitutes an excellent baseline for considering plankton as ecological an indicator of water quality.

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Author Biographies

Maximiliano D. Garcia, Instituto Argentino de Oceanografía
Laboratorio de Ecología de Zooplancton
Nicolás Bonel, Universidad Nacional del Sur
Laboratorio de Zoología de Invertebrados I - Departamento de Biología, Bioquímica y Farmacia
Published
2014-05-15
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Issue
Section
Original Articles
Supporting Agencies
Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT-FONCyT))
Keywords:
Density, biomass, bacteria, phytoplankton, zooplankton, estuarine environment.
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How to Cite
1.
Garcia MD, Bonel N. Environmental modulation of the plankton community composition and size-structure along the eutrophic intertidal coast of the Río de la Plata estuary, Argentina. J Limnol [Internet]. 2014May15 [cited 2020Jun.6];73(3). Available from: https://www.jlimnol.it/index.php/jlimnol/article/view/jlimnol.2014.911