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Dynamics and limitations of phytoplankton biomass along a gradient in M wanza G ulf, southern L ake V ictoria ( T anzania)
Author(s) -
Cornelissen I. J. M.,
Silsbe G. M.,
Verreth J. A. J.,
Donk E.,
Nagelkerke L. A. J.
Publication year - 2014
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/fwb.12253
Subject(s) - phytoplankton , biomass (ecology) , chlorophyll a , environmental science , nutrient , detritus , oceanography , photosynthesis , environmental chemistry , biology , chemistry , ecology , botany , geology
Summary We investigated how dynamics in phytoplankton biomass are driven through light and nutrient limitations in the M wanza G ulf, L ake V ictoria ( T anzania). We measured light attenuation, chlorophyll a and water quality parameters along a phytoplankton biomass gradient in the M wanza G ulf at six sampling stations in three different seasons from A ugust 2009 to M arch 2011. We found a higher rate of attenuation of photosynthetic available radiation than in other gulfs of L ake V ictoria which could only partially be explained by phytoplankton biomass, measured as chlorophyll a . Suspended particulate detritus strongly affected light attenuation, particularly in shallow water. In shallow water in the southern part of the M wanza G ulf, nutrients were in excess and phytoplankton biomass was limited by light. In deeper water near the entrance of the gulf, light was not limiting when nitrogen probably was, as indicated by the N : P ratio. Low abundance of N ‐fixing phytoplankton species suggests that N ‐fixation was low in shallow water. Phytoplankton biomass was lower in M wanza G ulf than in northern gulfs of L ake V ictoria, but might increase in the future as a result of nutrient enrichment caused by an increase in intensive agriculture and rapid growth of the city of M wanza.