52
Bastiaan Knoppers . Bjorn Kjerfve
coastal lagoons of the state of Rio de Janeiro which form the most extensive blooms
are cyanobacteria, which proliferate during the warm summer and early fall. In winter and spring, dinoflagellates and diatoms, respectively, prevail (Moreira 1988; Moreira
and Knoppers 1990; Carmouze et al. 1993). Similar phytoplankton populations and
successional patterns are found in Concei<;:iio 1. However, diatoms, dinoflagellates, and
micro flagellates are more common than cyanobacteria, and anoxigenic autotrophic
purple bacteria dominate at and below the halocline within the central sections of
Concei<;:iio 1., particularly during prolonged periods of weak tidal flushing and stagnation of bottom waters (Knoppers et al. 1984; Odebrecht and Caruso 1987; Odebrecht
1988).
The more rapidly flushed lagoons, Cananeia-Iguape and the Patos Estuary, are governed by autotrophic flagellates and centric and pennate diatoms (Tundisi et al. 1973;
Abreu et al. 1992; 1994a,b). The striking feature in Piratininga 1. is the succession between phytoplankton and the macro algae. The macro algae commence proliferation
in winter and attain senescence in fall., as shown by the annual cycle of biomass dry
weight (Fig. 3.9). The subsequent degradation of the macro algae provides a nutrient
pulse for the sustenance of phytoplankton, i.e., chlorophyll a (Fig. 3.9) until growth is
resumed by the macro algae. Similar successional patterns have been observed in the
Peel-Harvey Estuary in western Australia, and the Venice Lagoon in Italy. The regeneration of nutrients occurs largely at the sediment-water interface (Sfrizo et al. 1988;
Carneiro et al. 1993 1994).
Other primary producers that should be considered are mangroves and emergent macrophytes. Mangroves cover 930 km2 along the southeastern coast, but are
largely absent in the lagoons. The southernmost limit of mangroves in Brazil is
Praia do Sonho, Santa Catarina (Schaeffer-Novelli 1989) at latitude 28°53'S, and thus
no mangroves are found in Rio Grande do SuI, including the Patos-Mirim Lagoon system. The only lagoon along the southeastern coast that has extensive mangrove forests is Cananeia-Iguape 1., which is not a choked lagoon but is flushed twice a day
by tides with a range of 1 m and exhibits salinities in the range 10-35. The CananeiaIguape mangroves cover 52 km 2 (Herz 1991) and consist mostly of Rhizo-phora
mangle 1., Avicennia schaureiana Stapf and Leech, and Laguncularia racemosa GFW
Meyer (Cintron and Schaeffer-Novelli 1992). The choked lagoons of Santa Catarina
and Rio de Janeiro, on the other hand, are characterized by occasional scrubby
patches of mangroves along the borders of the lagoons. The reason for this is the
lack of tidal range in the lagoons because of their choked characteristics, and also
the rather low salinities in many lagoons but hypersaline conditions in Araruama 1.
(Oliveira 1959).
The predominant marginal vegetation in most of the low-salinity choked lagoons
of Rio de Janeiro consists of the macrophyte Typha dominguensis Pers. The distribution, density, and primary production along the lagoon margins are controlled by salinity, frequency of marginal inundation, freshwater run-off, and groundwater supply. The most dense and productive patches are encountered in the vicinity of riverine
mouths. Studies of macrophytes, including their impact upon aquatic primary lagoon
production, have been restricted to MariG! 1. and Guarapina L. (Couto 1989). Although
the marginal macrophyte vegetation may be important as a filter, these wetlands typically comprise less than 10% of the lagoon's surface area.
Bastiaan Knoppers . Bjorn Kjerfve
coastal lagoons of the state of Rio de Janeiro which form the most extensive blooms
are cyanobacteria, which proliferate during the warm summer and early fall. In winter and spring, dinoflagellates and diatoms, respectively, prevail (Moreira 1988; Moreira
and Knoppers 1990; Carmouze et al. 1993). Similar phytoplankton populations and
successional patterns are found in Concei<;:iio 1. However, diatoms, dinoflagellates, and
micro flagellates are more common than cyanobacteria, and anoxigenic autotrophic
purple bacteria dominate at and below the halocline within the central sections of
Concei<;:iio 1., particularly during prolonged periods of weak tidal flushing and stagnation of bottom waters (Knoppers et al. 1984; Odebrecht and Caruso 1987; Odebrecht
1988).
The more rapidly flushed lagoons, Cananeia-Iguape and the Patos Estuary, are governed by autotrophic flagellates and centric and pennate diatoms (Tundisi et al. 1973;
Abreu et al. 1992; 1994a,b). The striking feature in Piratininga 1. is the succession between phytoplankton and the macro algae. The macro algae commence proliferation
in winter and attain senescence in fall., as shown by the annual cycle of biomass dry
weight (Fig. 3.9). The subsequent degradation of the macro algae provides a nutrient
pulse for the sustenance of phytoplankton, i.e., chlorophyll a (Fig. 3.9) until growth is
resumed by the macro algae. Similar successional patterns have been observed in the
Peel-Harvey Estuary in western Australia, and the Venice Lagoon in Italy. The regeneration of nutrients occurs largely at the sediment-water interface (Sfrizo et al. 1988;
Carneiro et al. 1993 1994).
Other primary producers that should be considered are mangroves and emergent macrophytes. Mangroves cover 930 km2 along the southeastern coast, but are
largely absent in the lagoons. The southernmost limit of mangroves in Brazil is
Praia do Sonho, Santa Catarina (Schaeffer-Novelli 1989) at latitude 28°53'S, and thus
no mangroves are found in Rio Grande do SuI, including the Patos-Mirim Lagoon system. The only lagoon along the southeastern coast that has extensive mangrove forests is Cananeia-Iguape 1., which is not a choked lagoon but is flushed twice a day
by tides with a range of 1 m and exhibits salinities in the range 10-35. The CananeiaIguape mangroves cover 52 km 2 (Herz 1991) and consist mostly of Rhizo-phora
mangle 1., Avicennia schaureiana Stapf and Leech, and Laguncularia racemosa GFW
Meyer (Cintron and Schaeffer-Novelli 1992). The choked lagoons of Santa Catarina
and Rio de Janeiro, on the other hand, are characterized by occasional scrubby
patches of mangroves along the borders of the lagoons. The reason for this is the
lack of tidal range in the lagoons because of their choked characteristics, and also
the rather low salinities in many lagoons but hypersaline conditions in Araruama 1.
(Oliveira 1959).
The predominant marginal vegetation in most of the low-salinity choked lagoons
of Rio de Janeiro consists of the macrophyte Typha dominguensis Pers. The distribution, density, and primary production along the lagoon margins are controlled by salinity, frequency of marginal inundation, freshwater run-off, and groundwater supply. The most dense and productive patches are encountered in the vicinity of riverine
mouths. Studies of macrophytes, including their impact upon aquatic primary lagoon
production, have been restricted to MariG! 1. and Guarapina L. (Couto 1989). Although
the marginal macrophyte vegetation may be important as a filter, these wetlands typically comprise less than 10% of the lagoon's surface area.