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| Titel |
Natural events of anoxia and low respiration index in oligotrophic lakes of the Atlantic Tropical Forest |
| VerfasserIn |
H. Marotta, M. L. S. Fontes, M. M. Petrucio |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 8 ; Nr. 9, no. 8 (2012-08-01), S.2879-2887 |
| Datensatznummer |
250007223
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| Publikation (Nr.) |
 copernicus.org/bg-9-2879-2012.pdf |
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| Zusammenfassung |
| Hypoxia is a well-recognized condition reducing biodiversity and
increasing greenhouse gas emissions in aquatic ecosystems, especially
under warmer temperatures of tropical waters. Anoxia is a natural event
commonly intensified by human-induced organic inputs in inland waters. Here,
we assessed the partial pressure of O2 (pO2) and CO2
(pCO2), and the ratio between them (represented by the respiration
index, RI) in two oligotrophic lakes of the Atlantic Tropical Forest,
encompassing dry and rainy seasons over 19 months. We formulated the
hypothesis that thermal stratification events could be coupled to natural
hypoxia in deep waters of both lakes. Our results indicated a persistence of
CO2 emissions from these tropical lakes to the atmosphere, on average ± standard error
(SE) of 17.4 mg C m−2 h−1 probably subsided by
terrestrial C inputs from the forest. Additionally, the thermal
stratification during the end of the dry season and the rainy summer was
coupled to anoxic events and very low RI in deep waters, and to
significantly higher pO2 and RI at the surface (about 20 000 μatm
and 1.0, respectively). In contrast, the water mixing during dry seasons at
the beginning of the winter was related to a strong destratification in
pO2, pCO2 and RI in surface and deep waters, without reaching any
anoxic conditions throughout the water column. These findings confirm our
hypothesis, suggesting that lakes of the Atlantic Tropical Forest could be
dynamic, but especially sensitive to organic inputs. Natural anoxic events
indicate that tropical oligotrophic lakes might be highly influenced by
human land uses, which increase organic discharges into the watershed. |
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