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Variability in factors causing light attenuation in Lake Victoria
Author(s) -
LOISELLE STEVEN A.,
AZZA NICHOLAS,
CÓZAR ANDRES,
BRACCHINI LUCA,
TOGNAZZI ANTONIO,
DATTILO ARDUINO,
ROSSI CLAUDIO
Publication year - 2008
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.2007.01918.x
Subject(s) - phytoplankton , environmental science , biomass (ecology) , oceanography , organic matter , colored dissolved organic matter , chlorophyll a , dissolved organic carbon , water column , ecology , hydrology (agriculture) , nutrient , geology , biology , botany , geotechnical engineering
Summary 1. The major optical components controlling the attenuation of photosynthetic available radiation in nearshore areas of Lake Victoria (Uganda and Kenya) were examined and their impact compared. It was found that chromophoric dissolved organic matter and tripton play a dominating role in many nearshore areas, indicating that the coastal areas of Lake Victoria cannot be considered as Case I waters. 2. Concentrations of chromophoric dissolved organic matter declined with distance from the coast in an exponential manner indicating dilution and degradation of terrestrial sources of organic matter rather than in situ production. The importance of tripton was found to follow a similar pattern, while the relative importance of phytoplankton biomass in overall attenuation of photosynthetic available radiation was found to increase with distance from the coast. A specific attenuation coefficient for phytoplankton biomass was determined (0.019 m 2 mg Chl a −1 ). 3. Using a light limitation approach based on carrying capacity, it was possible to map areas that are closer to being light limited. Light limitation appears to occur throughout most bays and some coastal areas receiving catchment waters. This spatial information, geographically referenced to bathymetric and catchment conditions, was utilized to understand the importance of environmental conditions in limiting phytoplankton biomass.