8 Baia de Guanabara, Rio De Janeiro, Brazil
B. KJERFVE, L.D. DELACERDA, and G.T.M. DIAS
8.1 Introduction
Baia de Guanabara (approx. 23°45'5 44°45'W) is a eutrophic and polluted
coastal bay in Brazil, impacted by the discharge from the Rio de Janeiro
metropolitan area. The shallow bay measures 28 km from west to east and
30 km from south to north, has a 131-km perimeter, a mean water volume
of 1.87 x 10 9 m3, and 384km 2 surface area. The entrance to Baia de Guanabara is only 1.6km wide (Fig. 8.1). The bay is structurally controlled and
has a central channel with a depth of 30m and a sandy bottom near the
entrance, reflecting wave and tidal forcing. Bottom sediments are mostly
muds as a result of the Holocene transgression and rapid fluvial sedimentation, accelerated by channelization of rivers and deforestation in the
drainage basin. An extensive sandbank is located seaward of the bay entrance and a flood-oriented sand wave system indicates sand transport
into the bay. The mean freshwater runoff measures 125m 3 s- 1 and peaks in
January. Tides are mixed and mainly semidiurnal with a range of 0.7 m,
and peak spring tidal currents reach 0.5 m s- 1 inside the bay and 1.6 m s- 1
in the bay entrance. The passage of northward propagating polar fronts
occasionally results in strong winds from the southwest and high-energy,
long-period waves from the south. The salinity of the bay varies from
21.0 to 34.5 with a weak vertical salinity stratification. An estuarine circulation is characterized by a 900m 3 s- 1 net surface outflow. Fifty percent of
the water volume in Baia de Guanabara flushes every 11.4 days. Largely
untreated sewage enters the bay from the west, resulting locally in very
poor water quality. The near-bottom mean dissolved oxygen concentration
at the inner-most station measures 3.1 mg 1- 1 and results in anoxic bottom
muds. The worst water quality is indicated by average fecal coliform counts
higher than 1,000 ml- 1 • The average chlorophyll concentration in the inner
bay, in response to high nutrient loading, exceeds 130 jlg 1- 1 •
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001
B. KJERFVE, L.D. DELACERDA, and G.T.M. DIAS
8.1 Introduction
Baia de Guanabara (approx. 23°45'5 44°45'W) is a eutrophic and polluted
coastal bay in Brazil, impacted by the discharge from the Rio de Janeiro
metropolitan area. The shallow bay measures 28 km from west to east and
30 km from south to north, has a 131-km perimeter, a mean water volume
of 1.87 x 10 9 m3, and 384km 2 surface area. The entrance to Baia de Guanabara is only 1.6km wide (Fig. 8.1). The bay is structurally controlled and
has a central channel with a depth of 30m and a sandy bottom near the
entrance, reflecting wave and tidal forcing. Bottom sediments are mostly
muds as a result of the Holocene transgression and rapid fluvial sedimentation, accelerated by channelization of rivers and deforestation in the
drainage basin. An extensive sandbank is located seaward of the bay entrance and a flood-oriented sand wave system indicates sand transport
into the bay. The mean freshwater runoff measures 125m 3 s- 1 and peaks in
January. Tides are mixed and mainly semidiurnal with a range of 0.7 m,
and peak spring tidal currents reach 0.5 m s- 1 inside the bay and 1.6 m s- 1
in the bay entrance. The passage of northward propagating polar fronts
occasionally results in strong winds from the southwest and high-energy,
long-period waves from the south. The salinity of the bay varies from
21.0 to 34.5 with a weak vertical salinity stratification. An estuarine circulation is characterized by a 900m 3 s- 1 net surface outflow. Fifty percent of
the water volume in Baia de Guanabara flushes every 11.4 days. Largely
untreated sewage enters the bay from the west, resulting locally in very
poor water quality. The near-bottom mean dissolved oxygen concentration
at the inner-most station measures 3.1 mg 1- 1 and results in anoxic bottom
muds. The worst water quality is indicated by average fecal coliform counts
higher than 1,000 ml- 1 • The average chlorophyll concentration in the inner
bay, in response to high nutrient loading, exceeds 130 jlg 1- 1 •
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001