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| Titel |
Teleconnections between ecosystem productivity and climate indices in a tropical great lake |
| VerfasserIn |
François Darchambeau, Alberto V. Borges, Hugo Sarmento, Bruno Leporcq, Pascal M. Isumbisho, Georges Alunga, Pascal M. Masilya, Jean-Pierre Descy |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080988
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| Zusammenfassung |
| Productivity of deep tropical lakes is mainly determined by physical forcing. Located in
the East African Rift, Lake Kivu [2.50Ë S 1.59Ë S, 29.37Ë E 28.83Ë E] is a deep
meromictic lake. Phytoplankton biomass is generally low due to the lake’s oligotrophic
nature except when seasonal deeper mixing of the surface water layer brings up
nutrients from deeper waters, allowing a seasonal peak of phytoplankton biomass. This
seasonal mixing favours the development of diatoms, while, during the rest of the year,
the phytoplankton assemblage is dominated by cyanobacteria, chrysophytes and
cryptophytes. A long-term limnological survey on Lake Kivu conducted from 2002-2011
allowed us to delineate relationships between intra- and inter-annual variations of
limnological parameters and lake productivity. During this survey, inter-annual
variations of biomass and productivity were high, with for example a 5-fold maximum
difference between the seasonal peak of biomass. The importance of the annual
biomass peak was negatively correlated to the stability of the water column during
the season preceding the bloom. This suggests that the importance of the annual
bloom is not driven by weather conditions during the mixing period but by the
stratifying conditions prevailing several months earlier. Statistically highly significant
correlations were observed between intra- and inter-annual variations of water column
stability, phytoplankton biomass and tropical ocean climate indexes, including Western
Tropical Indian Ocean (WTIO) sea surface temperature (SST) anomaly index, Dipole
Mode Index (DMI), Southern Ocean Index (SOI) and El Niño-Southern Oscillation
(ENSO), were also observed. Inter-annual variations in relation to large scale climate
oscillations can be used as natural laboratories and give indications how ecosystems will
respond to climate change. This study allowed us to make some predictions on
the effects of climate change on lake water column stability and lake productivity. |
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