The Subtropical Estuarine Complex of Paranagua Bay, Brazil
135
bay. During neap cycles, strong non-linear interactions allow for the formation of up to six high and low tides per day. Spring tides range from
1. 7 m at the mouth to 2. 7 m in the upper bay. The mean tidal range is 2.2 m,
with a tidal prism of 1.34 km 3 and a tidal intrusion of 12.6 km. Following
cold front forcing, storm surges elevate water levels up to 80 em above
astronomical tides (Marone and Camargo 1994). Current velocities increase upstream, with maxima of 0.8-0.85 m s- 1 at ebb and 1-1.4 m s- 1 at
flood (FUNPAR 1997).
The average annual freshwater input from the coastal plain catchment
area (about 1,918km 2 ) and from the small and steep drainage basins of the
Serra do Mar is close to 200m 3 s- 1 • The Cachoeira and Nhundiaquara
rivers, with an average discharge of 21.13 and 15.88 m 3 s- 1 , respectively, are
the main tributaries (Bigarella et al. 1978), while input to the mid-sector of
the bay is approximately 75m 3 s- 1 (Knoppers et al. 1987). Groundwater may
contribute up to 10% of the total surface freshwater runoff (FUNPAR
1997). Seasonal variations of freshwater input correspond to around 30%
of mean annual values during the dry period (May/October) and 170%
during the rainy period (November/ April). Runoff to the coastal zone ranges from approximately 7 to 28 x 10 6 m 3 day-- 1 during the dry and rainy season, respectively.
10.2.3 Chemical Characteristics
The distribution and temporal variation of physico-chemical properties
in Paranagua Bay are closely correlated to salinity and energy gradients.
Annual dissolved oxygen concentrations typically range from 4 to
7.5 mll- 1 • The lowest oxygen concentrations are usually found in bottom
waters of the inner and mid region during the rainy period, while enhanced primary productivity may cause highest saturation values in the
mid bay (Brandini 1985). The distribution patterns of suspended material
are less defined, probably due to the complex hydrodynamics of the
estuary. Average concentrations range from 10 to 120 mg 1- 1 in rainy summers but are about 40% lower during dry winters, possibly owing to resuspension of sediments by winds and intrusion of saline bottom waters.
The nutrient and trophic status of Paranagua Bay is the result of interactions between hydrodynamic processes and different mechanisms of
sink and supply, such as biological uptake, freshwater input, sedimentwater interactions and sewage discharge from the city of Paranagua. The
trophic state, based on annual rates of organic carbon supply and on chlorophyll, POC and nutrient concentrations, varies from almost oligotrophic
in winter in the outer section to eutrophic during summer in the middle
135
bay. During neap cycles, strong non-linear interactions allow for the formation of up to six high and low tides per day. Spring tides range from
1. 7 m at the mouth to 2. 7 m in the upper bay. The mean tidal range is 2.2 m,
with a tidal prism of 1.34 km 3 and a tidal intrusion of 12.6 km. Following
cold front forcing, storm surges elevate water levels up to 80 em above
astronomical tides (Marone and Camargo 1994). Current velocities increase upstream, with maxima of 0.8-0.85 m s- 1 at ebb and 1-1.4 m s- 1 at
flood (FUNPAR 1997).
The average annual freshwater input from the coastal plain catchment
area (about 1,918km 2 ) and from the small and steep drainage basins of the
Serra do Mar is close to 200m 3 s- 1 • The Cachoeira and Nhundiaquara
rivers, with an average discharge of 21.13 and 15.88 m 3 s- 1 , respectively, are
the main tributaries (Bigarella et al. 1978), while input to the mid-sector of
the bay is approximately 75m 3 s- 1 (Knoppers et al. 1987). Groundwater may
contribute up to 10% of the total surface freshwater runoff (FUNPAR
1997). Seasonal variations of freshwater input correspond to around 30%
of mean annual values during the dry period (May/October) and 170%
during the rainy period (November/ April). Runoff to the coastal zone ranges from approximately 7 to 28 x 10 6 m 3 day-- 1 during the dry and rainy season, respectively.
10.2.3 Chemical Characteristics
The distribution and temporal variation of physico-chemical properties
in Paranagua Bay are closely correlated to salinity and energy gradients.
Annual dissolved oxygen concentrations typically range from 4 to
7.5 mll- 1 • The lowest oxygen concentrations are usually found in bottom
waters of the inner and mid region during the rainy period, while enhanced primary productivity may cause highest saturation values in the
mid bay (Brandini 1985). The distribution patterns of suspended material
are less defined, probably due to the complex hydrodynamics of the
estuary. Average concentrations range from 10 to 120 mg 1- 1 in rainy summers but are about 40% lower during dry winters, possibly owing to resuspension of sediments by winds and intrusion of saline bottom waters.
The nutrient and trophic status of Paranagua Bay is the result of interactions between hydrodynamic processes and different mechanisms of
sink and supply, such as biological uptake, freshwater input, sedimentwater interactions and sewage discharge from the city of Paranagua. The
trophic state, based on annual rates of organic carbon supply and on chlorophyll, POC and nutrient concentrations, varies from almost oligotrophic
in winter in the outer section to eutrophic during summer in the middle