The Rio de Ia Plata Estuary, Argentina-Uruguay
199
front (Mianzan and Guerrero in press; Fig. 13.2C). Mixing of estuarine and
marine waters and enhancement of vertical nutrient flux fertilize the frontal area (Mendez et al. 1997), with maximum chlorophyll-a concentrations
occurring at the surface salinity front. Neritic diatoms, colonies of Phaeocystis sp. (Nellen 1990), and aggregations of dinoflagellates and coccolithophores ( Carreto and Akselman 1996; Gayoso 1996) dominate the
phytoplankton, allowing for the development of dense copepod (i.e., Acartia tonsa) populations that constitute food for the gelatinous plankton
(i.e., Mnemiopsis maccradyi; Mianzan and Sabatini 1985; Sorarrain 1998).
Many fish species in the area feed on gelatinous plankton (Mianzan et al.
1996).
13.5 Human Impacts and Management Needs
The Rio de la Plata estuary receives waters impacted by both subsistence
and highly productive agriculture and cattle raising. Industrial and urban
areas around the estuary, principally Buenos Aires and Montevideo with
about 13 million inhabitants, affect the aquatic habitat and conflict with
environmental issues. The activities of the ports in Buenos Aires and Montevideo, dredging, and subaquatic sediment disposals along the main
access channels cause major environmental impacts. The estuary is the
maritime access to a highly complex fluvial system communicating with
the Amazon Basin and nautical accidents have caused oil spills in recent
years; so, navigation activities are inadequately considered by environmental management plans.
Higher metal concentrations in the sediments and water column in
areas under the influence of port activities or municipal sewage discharge
are probably related to point sources. The disappearance of commercially
valuable species like mussels and the red crab has been related to industrial
wastes (Grana and Pineiro 1997). Municipal and industrial wastewater of
Montevideo is released close to the head of the salt wedge regime. Since
some contaminants are likely to be retained, this area is particularly sensitive and, owing to the biological significance of the head of the salt wedge
for the life cycles of many valuable fish species, deserves especial attention
in future environmental plans.
Socio-economic activities in the Rio de la Plata estuary include industrial and artisanal fisheries. During productive years, fisheries of Micropogonias furnieri in mixohaline waters involve about 200 vessels and 1,000
fishermen, generating approximately 30 million dollars in revenues. In the
Argentine-Uruguayan Common Fishing Zone this resource is managed
199
front (Mianzan and Guerrero in press; Fig. 13.2C). Mixing of estuarine and
marine waters and enhancement of vertical nutrient flux fertilize the frontal area (Mendez et al. 1997), with maximum chlorophyll-a concentrations
occurring at the surface salinity front. Neritic diatoms, colonies of Phaeocystis sp. (Nellen 1990), and aggregations of dinoflagellates and coccolithophores ( Carreto and Akselman 1996; Gayoso 1996) dominate the
phytoplankton, allowing for the development of dense copepod (i.e., Acartia tonsa) populations that constitute food for the gelatinous plankton
(i.e., Mnemiopsis maccradyi; Mianzan and Sabatini 1985; Sorarrain 1998).
Many fish species in the area feed on gelatinous plankton (Mianzan et al.
1996).
13.5 Human Impacts and Management Needs
The Rio de la Plata estuary receives waters impacted by both subsistence
and highly productive agriculture and cattle raising. Industrial and urban
areas around the estuary, principally Buenos Aires and Montevideo with
about 13 million inhabitants, affect the aquatic habitat and conflict with
environmental issues. The activities of the ports in Buenos Aires and Montevideo, dredging, and subaquatic sediment disposals along the main
access channels cause major environmental impacts. The estuary is the
maritime access to a highly complex fluvial system communicating with
the Amazon Basin and nautical accidents have caused oil spills in recent
years; so, navigation activities are inadequately considered by environmental management plans.
Higher metal concentrations in the sediments and water column in
areas under the influence of port activities or municipal sewage discharge
are probably related to point sources. The disappearance of commercially
valuable species like mussels and the red crab has been related to industrial
wastes (Grana and Pineiro 1997). Municipal and industrial wastewater of
Montevideo is released close to the head of the salt wedge regime. Since
some contaminants are likely to be retained, this area is particularly sensitive and, owing to the biological significance of the head of the salt wedge
for the life cycles of many valuable fish species, deserves especial attention
in future environmental plans.
Socio-economic activities in the Rio de la Plata estuary include industrial and artisanal fisheries. During productive years, fisheries of Micropogonias furnieri in mixohaline waters involve about 200 vessels and 1,000
fishermen, generating approximately 30 million dollars in revenues. In the
Argentine-Uruguayan Common Fishing Zone this resource is managed