Phytoplankton in Lake Tanganyika : vertical and horizontal distribution of in vivo fluorescence

Determinations of chlorophyll a and in vivo fluorescence of photosynthetic pigments were used to study vertical and horizontal distribution of phytoplankton in Lake Tanganyika (East Africa). Blue excited fluorescence (IVF^sub b^) was an approximate predictor of chlorophyll a at different depths and...

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Bibliographic Details
Published in:Hydrobiologia 1999-07, Vol.407, p.89-103
Main Authors: SALONEN, K, SARVALA, J, JÄRVINEN, M, LANGENBERG, V, NUOTTAJÄRVI, M, VUORIO, K, CHITAMWEBWA, D. B. R
Format: Article
Language:English
Subjects:
Africa, Tanganyika L
Anabaena
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Chlorophyll
Congo
Cyanophyta
Fluorescence
Fresh water ecosystems
Fundamental and applied biological sciences. Psychology
Lakes
Phytoplankton
Plankton
Synecology
Tanzania
Thermal stratification
Thermocline
Ultraviolet radiation
Upwelling
Zaire
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Summary:Determinations of chlorophyll a and in vivo fluorescence of photosynthetic pigments were used to study vertical and horizontal distribution of phytoplankton in Lake Tanganyika (East Africa). Blue excited fluorescence (IVF^sub b^) was an approximate predictor of chlorophyll a at different depths and locations. Green excited fluorescence (IVF^sub g^), which reflects phycoerythrin in cyanobacteria, explained chlorophyll a variation equally well, and in combination with IVF^sub b^ the degree of explanation was improved to 87% (n = 90). Particularly during the shallow stratification in March-May, the maxima of chlorophyll a, IVF^sub b^ and IVF^sub g^ were located within the thermocline. Such distribution may have resulted from the high penetration of UV light, often accentuated by very shallow daytime thermal stratification, leading to inhibition of phytoplankton near the surface. Because the decrease of chlorophyll a specific IVF^sub b^ was less striking towards the surface, the decrease of IVF^sub b^ was not caused by light inhibition only. In October-November, epilimnetic IVF^sub b^ and chlorophyll a values seemed to be consistently higher than in April-May and often showed remarkable patchiness. The sometimes very dense phytoplankton blooms (Anabaena sp., Cyanobacteria) observed in the central and southern parts of the lake, suggest that local upwelling or mixing events may be important for the development of phytoplankton in Lake Tanganyika.[PUBLICATION ABSTRACT]
ISSN:0018-8158
1573-5117
DOI:10.1023/A:1003764825808