13 The Rio de la Plata Estuary, Argentina-Uruguay
H. MIANZAN, c. LASTA, E. ACHA, R. GUERRERO, G. MACCHI,
and C. BREMEC
13.1 Introduction
The Rio de la Plata is an extensive and shallow coastal plain estuary on the
western South Atlantic coast (35-36°S). The estuary receives freshwater
from South America's second largest basin (about 3.2 million km 2 ) through
the Parana River, one of the longest in the world, its main tributary, the
Paraguay River, and the Uruguay River. The funnel of the Rio de la Plata
estuary extends for over 280 km from the head (25 km wide), at the confluence of the Parana and Uruguay rivers, to the 230-km-wide mouth between
Punta Rasa and Punta del Este. A submerged shoal, the Barra del Indio,
represents a geomorphological barrier and divides the Rio de la Plata
estuary into an inner and an outer system (Fig. 13.1 ). The inner fluvial
system under strong tidal influence, with a depth between 1 and 5 m, is
about 180 km long and up to 80 km wide and extends over 13,000 km 2 • In
the outer mixohaline brackish system with an area of about 22,000km 2 ,
both depths (5-25 m) and section width increase concomitantly (Fig.13.1).
However, the mixohaline area increases to about 38,000 km 2 if based on the
mean position of the 30 isohaline (Guerrero et al. 1997a,b). The limit between mixohaline waters and continental shelf waters depends on the dynamics of the estuary. The main characteristics of the Rio de la Plata estuary
are its large spatial scale and the occurrence of a quasi-permanent salt
wedge regime, which generates a border system (bottom and surface
salinity fronts) which plays an important role in the reproductive processes of fish species and where high zooplankton biomass concentrates.
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
©Springer-Verlag Berlin Heidelberg 2001
H. MIANZAN, c. LASTA, E. ACHA, R. GUERRERO, G. MACCHI,
and C. BREMEC
13.1 Introduction
The Rio de la Plata is an extensive and shallow coastal plain estuary on the
western South Atlantic coast (35-36°S). The estuary receives freshwater
from South America's second largest basin (about 3.2 million km 2 ) through
the Parana River, one of the longest in the world, its main tributary, the
Paraguay River, and the Uruguay River. The funnel of the Rio de la Plata
estuary extends for over 280 km from the head (25 km wide), at the confluence of the Parana and Uruguay rivers, to the 230-km-wide mouth between
Punta Rasa and Punta del Este. A submerged shoal, the Barra del Indio,
represents a geomorphological barrier and divides the Rio de la Plata
estuary into an inner and an outer system (Fig. 13.1 ). The inner fluvial
system under strong tidal influence, with a depth between 1 and 5 m, is
about 180 km long and up to 80 km wide and extends over 13,000 km 2 • In
the outer mixohaline brackish system with an area of about 22,000km 2 ,
both depths (5-25 m) and section width increase concomitantly (Fig.13.1).
However, the mixohaline area increases to about 38,000 km 2 if based on the
mean position of the 30 isohaline (Guerrero et al. 1997a,b). The limit between mixohaline waters and continental shelf waters depends on the dynamics of the estuary. The main characteristics of the Rio de la Plata estuary
are its large spatial scale and the occurrence of a quasi-permanent salt
wedge regime, which generates a border system (bottom and surface
salinity fronts) which plays an important role in the reproductive processes of fish species and where high zooplankton biomass concentrates.
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
©Springer-Verlag Berlin Heidelberg 2001