Abstract
Previous studies have demonstrated that macro-scale climatic events such as ENSO, cause changes in meteorological and hydrological conditions, inducing physicochemical changes in the water column, as well as in coastal and estuarine communities in the Atlantic Ocean. Rio de la Plata (RdlP) is the second largest estuary of South America, where ENSO is a macro-scale environmental driving force. In this paper, the species composition, abundance, as well as the temporal and horizontal variation of the mesozooplankton in the north coast of the RdlP during 2009-2010 ENSO were analyzed. Zooplankton samples were collected with sub-surface trawls in fifteen stations during eleven sampling surveys. Physico-chemical parameters of the water column (temperature, salinity, dissolved oxygen, turbidity, and chlorophyll a) were determined and related to the RdlP flows. The holoplankton was dominated by estuarine copepod (Acartia tonsa), freshwater cladocerans (Bosmina hagmanni, Ceriodaphnia dubia, Moina sp.), and in the meroplankton, barnacle larvae were the most abundant group. Temporal variability was reflected in abundance differences and ecological indexes between both ENSO phases. The copepods abundance showed a positive association with RdlP flow during El Niño (Nov 2009-Apr 2010), and negative during La Niña-Neutral (Sep 2010-Jan 2011). During El Niño months, the higher richness of typical freshwater cladocerans was observed, promoting a horizontal heterogeneity in the study area. During La Niña-Neutral, the zooplankton showed lower species richness and was dominated by copepods typical of the RdlP (Acartia tonsa). Canonical Correspondence Analysis showed that salinity, RdlP flow, and chlorophyll a explained 88.4% of the total variance of the species-environment relationships. This paper presents new information on zooplanktonic organisms’ response to climatic and hydrological events in the RdlP estuary.
Highlights
Previous studies have demonstrated that macro-scale climatic events such as ENSO, cause changes in meteorological and hydrological conditions, inducing physicochemical changes in the water column, as well as in coastal and estuarine communities in the Atlantic Ocean
Durante fases de El Niño-Oscilación del Sur (ENOS) se encontraron variaciones interanuales en los patrones comunitarios zooplanctónicos debido a modificaciones en las descargas de agua dulce o ingresos de masas oceánicas asociados a las fases, positiva (El Niño) o negativa (La Niña) de ENOS (Kimmel & Roman, 2004; Andrade et al, 2016)
(5.6±3.3 Nefelométricas de Turbidez (NTU)) en enero 2011 y máximo en febrero 2010 (61.9±38.4 NTU), con diferencias significativas entre fases de ENOS (El Niño: 33.5±26.9 NTU; La Niña-Neutral: 20.0±19.1 NTU; U=1.78; P
Summary
Ernesto1,2*, Karina Sans, Pablo Muniz, Natalia Venturini, Mónica Gómez1 & Felipe García-Rodríguez. Se ha demostrado que los eventos climáticos a macro-escala como El Niño-Oscilación Sur (ENOS) ocasionan modificaciones en las condiciones meteorológicas e hidrológicas, promoviendo cambios físico-químicos en la columna de agua y en las comunidades bentónicas y pelágicas de zonas costeras y estuarinas en el Océano Atlántico. La abundancia de copépodos mostró asociación con los caudales del RdlP, negativos durante la fase El Niño y positivos durante La Niña-Neutral. Durante La Niña-Neutral (septiembre 2010-enero 2011) el zooplancton presentó menor riqueza de especies y estuvo dominado por copépodos típicos del RdlP (Acartia tonsa). Mediante un Análisis de Correspondencia Canónica se determinó que la salinidad, caudal del RdlP y concentración de la clorofila a explicaron el 88.4% de la varianza total de la relación especie-ambiente. Palabras claves: Zooplancton, El Niño, caudales, salinidad, biodiversidad, Río de la Plata
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