The Patos Lagoon Estuary, Brazil
175
cheria longicaulis (70.4 g C m- 2 ) occurs in the winter and early spring,
whilst biomass peaks of Lyngbya confervoides (55.7 g C m- 2 ) and Microcoleus chthomoplastes ( 19.8 g C m- 2 ) correspond to the summer and fall, respectively. Other blue-green algae (i.e., Gomphosphaeria, Chroococuus) are
probably responsible for levels of high carbon fixation in the marshes
(Coutinho and Seeliger 1986; Seeliger et al. 1997).
At optimal temperature ( 15 oC) and salinity the growth of Ruppia maritima beds commences from seed germination in spring (Koch and Seeliger
1988). Biomass peaks may attain up to 83 g C m- 2 (30% below-ground biomass) after the formation of reproductive shoots in the summer, though
large variations between beds are common. Despite favorable light, temperature, and salinity regimes for perennial growth in the estuary, annual
growth cycles of Ruppia with massive die-off in fall are common, owing to
exposure of populations at the end of summer and/or increased sediment
dynamics. Since the size and density of Ruppia beds and the turnover of
leaves influence epiphyte colonization and growth, epiphyte biomass and
production is highly variable; however, maximum epiphyte biomass may
occasionally represent more than SO% of the total Ruppia biomass.
The dominant primary producers in lower marshes ( 64% flooding),
mid-marshes (20% flooding), and mesohaline transition zones between
mid- and lower marshes are Spartina alterniflora, Spartina densijlora, and
Scirpus maritimus, respectively. Their combined total mean net aboveground production (288-808 g C m- 2 year- 1 ) is comparable to highly productive Spartina alternijlora marshes elsewhere. The net below-ground
production of Spartina alternijlora (7289-2095 g C m- 2 year- 1 ) and Scirpus
maritimus (1510-2283g C m- 2 year- 1 ) represents more than 70% of their
total net primary production. The seasonal production cycles are likely to
be a function of air temperature optima. Rapid growth of the C 3 plant Scirpus maritimus proceeds at low temperatures ( <15 °C) in early spring and
highest live above-ground biomass and maximum dead/total aerial biomass is reached at the end of spring and at the end of summer, respectively. In contrast, maximum growth of C 4 plants (S. densijlora, S. alterniflora)
occurs above 20 °C at the end of spring, while highest dead and total aboveground biomass are reached in the early fall and during fall/winter, respectively (Costa 1997; Seeliger et al. 1997).
Conservative estimates of net primary production, based on minimum
and maximum biomass difference, suggest that up to 86% of the annual
autochthonous carbon in the estuary is produced by dominant marsh
plants and macro benthic and blue-green algae. Although the total annual
primary production in the Patos Lagoon estuary may considerably vary
between years, owing to changes in environmental conditions, sequential
pulses of carbon fixation by some producers and constant fixation by
175
cheria longicaulis (70.4 g C m- 2 ) occurs in the winter and early spring,
whilst biomass peaks of Lyngbya confervoides (55.7 g C m- 2 ) and Microcoleus chthomoplastes ( 19.8 g C m- 2 ) correspond to the summer and fall, respectively. Other blue-green algae (i.e., Gomphosphaeria, Chroococuus) are
probably responsible for levels of high carbon fixation in the marshes
(Coutinho and Seeliger 1986; Seeliger et al. 1997).
At optimal temperature ( 15 oC) and salinity the growth of Ruppia maritima beds commences from seed germination in spring (Koch and Seeliger
1988). Biomass peaks may attain up to 83 g C m- 2 (30% below-ground biomass) after the formation of reproductive shoots in the summer, though
large variations between beds are common. Despite favorable light, temperature, and salinity regimes for perennial growth in the estuary, annual
growth cycles of Ruppia with massive die-off in fall are common, owing to
exposure of populations at the end of summer and/or increased sediment
dynamics. Since the size and density of Ruppia beds and the turnover of
leaves influence epiphyte colonization and growth, epiphyte biomass and
production is highly variable; however, maximum epiphyte biomass may
occasionally represent more than SO% of the total Ruppia biomass.
The dominant primary producers in lower marshes ( 64% flooding),
mid-marshes (20% flooding), and mesohaline transition zones between
mid- and lower marshes are Spartina alterniflora, Spartina densijlora, and
Scirpus maritimus, respectively. Their combined total mean net aboveground production (288-808 g C m- 2 year- 1 ) is comparable to highly productive Spartina alternijlora marshes elsewhere. The net below-ground
production of Spartina alternijlora (7289-2095 g C m- 2 year- 1 ) and Scirpus
maritimus (1510-2283g C m- 2 year- 1 ) represents more than 70% of their
total net primary production. The seasonal production cycles are likely to
be a function of air temperature optima. Rapid growth of the C 3 plant Scirpus maritimus proceeds at low temperatures ( <15 °C) in early spring and
highest live above-ground biomass and maximum dead/total aerial biomass is reached at the end of spring and at the end of summer, respectively. In contrast, maximum growth of C 4 plants (S. densijlora, S. alterniflora)
occurs above 20 °C at the end of spring, while highest dead and total aboveground biomass are reached in the early fall and during fall/winter, respectively (Costa 1997; Seeliger et al. 1997).
Conservative estimates of net primary production, based on minimum
and maximum biomass difference, suggest that up to 86% of the annual
autochthonous carbon in the estuary is produced by dominant marsh
plants and macro benthic and blue-green algae. Although the total annual
primary production in the Patos Lagoon estuary may considerably vary
between years, owing to changes in environmental conditions, sequential
pulses of carbon fixation by some producers and constant fixation by