The mesozooplankton of the Patos Lagoon Estuary, Brazil: trends in community structure and secondary production

ABSTRACT

The zooplankton abundance and composition of the Patos Lagoon Estuary (PLE) reflects the local hydrological regime with alternating periods of flood, freshwater run-off and mixing of water. However, little is known about the interannual zooplankton variations and secondary productivity of this community. We sampled zooplankton monthly at two stations within the estuary from April 2009 to March 2013. The brackish/marine calanoid copepod Acartia tonsa was found to play an important role in the PLE, with secondary production values of 1.17 mg C m⁻³ day⁻¹ being comparable with the high values achieved in other estuaries worldwide. During the study period, the greatest change in the community structure was observed in the spring-summer under El Niño influence when the prolonged terrestrial run-off combined with higher temperatures allowed the establishment of a freshwater community that was largely composed of the calanoid copepod Notodiaptomus incompositus, cyclopoids and cladocerans. The freshwater copepod N. incompositus, which replaced A. tonsa, was second in importance with regard to production (mean 0.13 C m⁻³ day⁻¹). Our work emphasizes the ecological importance of long-term zooplankton monitoring studies and provides the first assessment of N. incompositus production.

RESPONSIBLE EDITOR:

• Tone Falkenhaug

KEYWORDS:

• Acartia tonsa
• ENSO
• Notodiaptomus incompositus
• productivity

Acknowledgements

The authors would like to thank Dr Gabriela A. Rezende for helping with PRIMER analyses as well as Dr Clarisse Odebrecht, Dr Virgínia M. Tavano and three anonymous reviewers for valuable contributions on earlier versions of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The study was funded by the Ministry of Science and Technology (MCT/CNPQ) and FAPERGS through the Brazilian Long-Term Ecological Research Program (BR-LTER) in the Patos Lagoon Estuary and Adjacent Coast. We acknowledge CNPQ and CAPES for granting scholarships to Priscila Teixeira-Amaral, Danielle Ortiz de Ortiz and Vanessa Ochi Agostini; Conselho Nacional de Desenvolvimento Científico e Tecnológico [403805/2012-0]; and Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul [3122-2551/12-7].