The eutrophication history of a tropical water supply reservoir in Brazil
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Journal of Paleolimnology
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Guarapiranga Reservoir is the second most
important public water supply in Sa˜o Paulo, Brazil and
has been eutrophic for several decades. We inferred the
major ecological shifts for the period 1919–2010
related to multiple stressors (forest flooding, hydrological change, use of algicide and eutrophication),
using geochemistry (TOC, TN, TP, C/N, d15N, d13C)
and diatom assemblages in a short (75-cm) sediment
core. Thirty-two diatom species were abundant in the
core and stratigraphically constrained incremental sum
of squares analysis enabled identification of three
diatom zones and four subzones, i.e. depths at which
marked changes in species composition occurred.
Early diatom assemblages were dominated by benthic,
oligotrophic taxa, mainly Eunotia, influenced by
flooded vegetation after dam construction. A shift to
dominance by a planktonic species (Eunotia tukanorum) occurred ca. 1932, during the period of initial
physical disturbance and early use of the water body as
a public water supply. Diatoms and geochemical
variables show that the reservoir was oligotrophic
from *1919 to 1947. Eutrophication began *1975
and by the early 1980s the reservoir had become
eutrophic, in response to an explosive increase in
human population in the watershed. Severe cultural
eutrophication has persisted since *1990. Higher
concentrations of copper in the sediments, beginning in
1991, reflect the increased use of copper sulfate to control cyanobacteria blooms and provide a chronological marker. Higher d15N values in recent sediments
indicate greater sewage inputs and low C/N values
reflect the predominant contribution of algae to
sediment organic matter. Eutrophic taxa Cyclotella
meneghiniana and Nitzschia sp. dominate recent
diatom assemblages, along with Aulacoseira granulata, a species that is tolerant of copper sulfate. Diatom
assemblages reflect multiple stressors, however, geochemical information provides a better understanding
of the early phase of the reservoir. Paleolimnologically
documented trophic state changes in this important
drinking water supply are largely attributable to
increased urbanization of the drainage basin and inputs
of sewage. Management efforts should focus on
mitigating this nutrient source.
Como referenciar
FONTANA, LUCIANE; ALBUQUERQUE, ANA L.S.; BRENNER, MARK; BONOTTO, DANIEL M.; SABARIS, TATIANI P.P.; PIRES, MARIA A.F.; COTRIM, MARYCEL E.B.; BICUDO, DENISE C. The eutrophication history of a tropical water supply reservoir in Brazil. Journal of Paleolimnology, v. 51, n. 1, p. 29-43, 2014. Disponível em: http://repositorio.ipen.br/handle/123456789/8953. Acesso em: 30 Dec 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.