RT journal article
T1 Basin-Scale Control on the Phytoplankton Biomass in Lake Victoria, Africa
A1 Cózar Cabañas, Andrés
A1 Bruno Mejías, Miguel
A1 Bergamino, Nadia
A1 Úbeda-Sánchez, Bárbara
A1 Bracchini, Luca
A1 Dattilo, Arduino M.
A1 Loiselle, Steven
A2 Biología
K1 Ocean color sensors
K1 East-Africa
K1 climate-Change
K1 Great-Lakes
K1 variability
K1 water
K1 Tanganyka
K1 Seawifs
K1 Eutrophication
K1 productivity
AB The relative bio-optical variability within Lake Victoria was analyzed through the spatio-temporal decomposition of a 19972004 dataset of remotely-sensed reflectance ratios in the visible spectral range. Results show a regular seasonal pattern with a phase shift (around 2 months) between the south and north parts of the lake. Interannual trends suggested a teleconnection between the lake dynamics and El-Nino phenomena. Both seasonal and interannual patterns were associated to conditions of light limitation for phytoplankton growth and basin-scale hydrodynamics on phytoplankton access to light. Phytoplankton blooms developed during the periods of lake surface warming and water column stability. The temporal shift apparent in the bio-optical seasonal cycles was related to the differential cooling of the lake surface by southeastern monsoon winds. North-south differences in the exposure to trade winds are supported by the orography of the Eastern Great Rift Valley. The result is that surface layer warming begins in the northern part of the lake while the formation of cool and dense water continues in the southern part. The resulting buoyancy field is sufficient to induce a lake-wide convective circulation and the tilting of the isotherms along the north-south axis. Once surface warming spreads over the whole lake, the phytoplankton bloom dynamics are subjected to the internal seiche derived from the relaxation of thermocline tilting. In 1997-98, El-Nino phenomenon weakened the monsoon wind flow which led to an increase in water column stability and a higher phytoplankton optical signal throughout the lake. This suggests that phytoplankton response to expected climate scenarios will be opposite to that proposed for nutrient-limited great lakes. The present analysis of remotely-sensed bio-optical properties in combination with environmental data provides a novel basin-scale framework for research and management strategies in Lake Victoria.
PB Howard Browman, Institute of Marine Research, Norway
YR 2012
FD 2012-12-08
LK http://hdl.handle.net/10498/19760
UL http://hdl.handle.net/10498/19760
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 07-nov-2026