TY - JOUR
T1 - Diversity and ecology of phytoplankton in Lake Edward (East Africa)
T2 - Present status and long-term changes
AU - Stoyneva-Gärtner, Maya P.
AU - Morana, Cédric
AU - Borges, Alberto V.
AU - Okello, William
AU - Bouillon, Steven
AU - Deirmendjian, Loris
AU - Lambert, Thibault
AU - Roland, Fleur
AU - Nankabirwa, Angela
AU - Nabafu, Erina
AU - Darchambeau, François
AU - Descy, Jean Pierre
N1 - Funding Information:
The study was conducted within the HIPE project, financed by the Belgian Scientific Policy Office (BELSPO, Brussels, Belgium) under the BRAIN program (BR/154/A1/HIPE), and by travel grants by the Fund for Scientific Research (FWO-Vlaanderen) provided to C.M. and S.B. AVB is a senior research associate at the FNRS.
Funding Information:
The study is based on 137 samples collected from Lake Edward in October-November 2016, March-April 2017 and January 2018, carried out in the framework of the HIPE (Human impacts on ecosystem health and resources of Lake Edward) research project supported by the Belgian Scientific Policy Office (BELSPO). The two first campaigns were conducted in the rainy season (October-November 2016, March-April 2017) and the third one in the dry season. (January 2018). A variety of sites in littoral and pelagic zones were sampled along two depth gradients in the Ugandan part of Lake Edward and Katwe Bay ( Fig. 1 ). Lake George and the Kazinga Channel, which flows into Lake Edward, were sampled during the three sampling campaigns. In January 2018, a deeper station (90 m deep) located in the Congolese waters was also sampled once ( Fig. 1 ).
Publisher Copyright:
© 2020 International Association for Great Lakes Research
PY - 2020/8
Y1 - 2020/8
N2 - Lake Edward is one of the African Rift Valley lakes draining into the Nile River basin. We conducted three sampling series in Lake Edward in October-November 2016, March-April 2017 and January 2018, in distinct seasonal conditions and in several sites varying by depth and proximity to river outlets, including the Kazinga Channel, which connects the hypertrophic Lake George to Lake Edward. The phytoplankton was examined using microscopy and marker pigment analysis by high performance liquid chromatography (HPLC) and subsequent CHEMTAX processing for estimating abundance of phytoplankton groups. Chlorophyll a concentration in the pelagic and littoral open lake sites barely exceeded 10 µg L−1 whereas, in contrast, in the semi-enclosed Bay of Katwe influenced by the Kazinga Channel chlorophyll a was up to 100 µg L−1. Despite substantial seasonal variations of limnological conditions such as photic and mixed layer depths, cyanoprokaryotes/cyanobacteria represented on average 60% of the phytoplankton biomass, followed by diatoms, which contributed ~25% of chlorophyll a, and by green algae, chrysophytes and cryptophytes. 248 taxa were identified with clear prevalence of cyanobacteria (104 taxa), from the morphological groups of coccal and filamentous species (non-heterocytous and heterocytous). The high proportion of heterocytous cyanobacteria, along with a relatively high particulate organic carbon to nitrogen (C:N) ratio, suggest N limitation as well as light limitation, most pronounced in the pelagic sites. During the rainy season, the most abundant diatoms in the plankton were needle-like Nitzschia. Comparison with previous studies found differences in water transparency, total phosphorus, and phytoplankton composition.
AB - Lake Edward is one of the African Rift Valley lakes draining into the Nile River basin. We conducted three sampling series in Lake Edward in October-November 2016, March-April 2017 and January 2018, in distinct seasonal conditions and in several sites varying by depth and proximity to river outlets, including the Kazinga Channel, which connects the hypertrophic Lake George to Lake Edward. The phytoplankton was examined using microscopy and marker pigment analysis by high performance liquid chromatography (HPLC) and subsequent CHEMTAX processing for estimating abundance of phytoplankton groups. Chlorophyll a concentration in the pelagic and littoral open lake sites barely exceeded 10 µg L−1 whereas, in contrast, in the semi-enclosed Bay of Katwe influenced by the Kazinga Channel chlorophyll a was up to 100 µg L−1. Despite substantial seasonal variations of limnological conditions such as photic and mixed layer depths, cyanoprokaryotes/cyanobacteria represented on average 60% of the phytoplankton biomass, followed by diatoms, which contributed ~25% of chlorophyll a, and by green algae, chrysophytes and cryptophytes. 248 taxa were identified with clear prevalence of cyanobacteria (104 taxa), from the morphological groups of coccal and filamentous species (non-heterocytous and heterocytous). The high proportion of heterocytous cyanobacteria, along with a relatively high particulate organic carbon to nitrogen (C:N) ratio, suggest N limitation as well as light limitation, most pronounced in the pelagic sites. During the rainy season, the most abundant diatoms in the plankton were needle-like Nitzschia. Comparison with previous studies found differences in water transparency, total phosphorus, and phytoplankton composition.
KW - Biodiversity
KW - Community structure
KW - Long-term change
KW - Productivity
KW - Tropical lake
UR - http://www.scopus.com/inward/record.url?scp=85078874025&partnerID=8YFLogxK
U2 - 10.1016/j.jglr.2020.01.003
DO - 10.1016/j.jglr.2020.01.003
M3 - Article
AN - SCOPUS:85078874025
SN - 0380-1330
VL - 46
SP - 741
EP - 751
JO - Journal of Great Lakes Research
JF - Journal of Great Lakes Research
IS - 4
ER -