Comparison of 1982–1983 and 1997–1998 El Niño effects on the shallow-water fish assemblage of the Patos Lagoon estuary (Brazil)

Abstract

were observed in locations dtroughout the world. In southern Brazil, E1 Nino events are associated with increased rainfall and higher freshwater discharge into Patos Lagoon, a large coastal lagoon that empties into the Atlantic Ocean. Based on interdecadal meteorological and biological data sets encompassing the two strongest E1 Nino events of the la.~t 50 yr, we evaluated the hypothesis that E1 Nino-induced hydrological changes are a major driving force controlling the interannual variation in the structure and dynamics of fishes in the Patos Lagoon estuary. High rainfall in the drainage basin of the lagoon coincided with low salinity in the estuarine area during both E1 Nino episodes. Total rainfall in the drainage basin was higher (767 versus 711 mm) and near-zero salinity conditions in the estuarine area lasted about 3 mo longer during the 1997-1998 E1 Nino event compared with the 1982-1983 event. Hydrological changes triggered by both E1 Nino events had similar relationships to fish species composition and diversity patterns, but the 1997-1998 event appeared to have stronger effects on the species a.~emblage. Although shifts in species composition were qualitatively similar during the two E1 Nino events. distance between E1 Nino and non-EI Nino assemblage multivariate centroids was greater during the 1996-2000 sampling period compared with the 1979-1983 period. We provide a conceptual model of the principal mechanisms and processes connecting the atmospheric-oceanographic interactions triggered by the E1 Nino phenomena and their effect on the estuarine fish assemblage. stood, Timmermann et al. (1999) showed that, under a scenario of increasing greenhouse-gas concentrations, EI Nino-like conditions would become more frequent. The frequency and intensity of EI Nino events and their effects may also be influenced by the phases of interdecadal modes of sea surface temperature variation (Mestas-Nunez and Enfield 1999, 2001). If El Nino events increase in severity and duration in response to global change, it will become critically important to understand how meteorological and hydrological patterns associated with EI Nino events affect ecosystems. Patos Lagoon (3~, 490W) represents an appropriate ecosystem to evaluate how disturbances induced by EI Nino can affect the dynamics and structure of fish estuarine assemblages. EI Nino episodes have affected the western coasts of the Americas frequently over the last 5,000 yr (Rollins et al. 1986), which coincides with the geomorphologic age (5,000-6,000 yr) estimated for the Patos Lagoon system on the Atlantic coast of southern Brazil (Knoppers and Kjerfve 1999). High rainfall in southern Brazil during EI Nino events (Grimm et al. 1998, 2000) increases freshwater discharged .

Plasma ion levels of freshwater and marine/estuarine teleosts from Southern Brazil

“…In addition, this approach confirms the physiological and ionoregulatory mechanisms reported for fish found in estuarine regions (Elliott & Dewailly, 1995;Prodócimo & Freire, 2001;Garcia et al, 2003aGarcia et al, , 2003bGarcia et al, , 2004Burns et al, 2006;Freire & Prodócimo, 2007;Martinho et al, 2007;Da Rocha et al, 2009). Our findings also confirm results from earlier studies regarding the environments used by these fish species for feeding, reproduction and nursery grounds (Chao et al, 1985;Vieira & Castello, 1996;Garcia et al, 2003aGarcia et al, , 2003bGarcia et al, , 2004Burns et al, 2006).…”

Prolonged estuarine habitat use by dusky grouper Epinephelus marginatus at subtropical latitudes revealed by otolith microchemistry

“…Climatic interannual variability is considerable in the study region. For instance, the strong El Niño Southern Oscillation (ENSO) event that occurred in 2002 (birth year of some of the individuals analyzed here), led to positive rainfall anomalies in this region that increased freshwater discharge into the lagoon, which, in turn, had significant effects on fish distribution and abundance (Garcia et al 2003(Garcia et al , 2004. However, no generalized substantial increases in Ba:Ca ratios in E. marginatus otoliths were observed, nor was it possible to link these to the increased freshwater runoff produced by this or other similar climatic events.…”

Effects of the hydrological regime on the ichthyofauna of riverine environments of the Upper Paraná River floodplain

“…Extreme climatic events affect fish assemblages due to their influence on the variation of the hydrological regime, as has been widely demonstrated for estuaries (Garcia et al, 2004) but still not intensely evaluated for inland waters.…”