[en] Lake Kivu, East Africa, is a deep oligotrophic and meromictic lake containing high amounts of
dissolved methane (∼55–60 km3) and carbon dioxide (∼300 km3) in its deep waters. Methane
harvesting for energy production began in 2015, and a monitoring programme was set up to
assess possible disturbance on the ecosystem. Phytoplankton biomass and composition was
assessed twice per month or monthly at 2 monitoring sites between June 2005 and December
2019, based on HPLC analysis of chlorophyll a (Chl-a) and marker pigments. This long-term
series shows that significant changes occurred around 2010 in the lake phytoplankton, with a
notable increase of Chl-a and changes in the assemblage toward an increase in non-motile
green algae and diatoms. To assess possible changes due to methane harvesting, we compared
2 periods, 2012–2014 and 2018–2019. Chl-a concentration decreased slightly in 2018–2019
compared to the reference period of 2012–2014, and significant changes occurred in
composition of the phytoplankton assemblage. In terms of relative contribution to Chl-a,
diatoms increased from 26% to 46%, whereas green algae decreased ∼2-fold, from 35% in
2012–2014 to 18% in 2018–2019. Multivariate analyses showed that phytoplankton composition
was influenced by seasonal and interannual variations of limnological variables related to
changes in meteorological factors. To assess possible future changes due to methane
exploitation, we recommend increasing sampling frequency and taxonomic resolution, as well
as improving environmental data acquisition.
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Mudakikwa, Eric
Thiery, Wim
Latli, Adrien
Leporcq, Bruno
Rugema, Edouard
Descy, Jean-Pierre ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Language :
English
Title :
Phytoplankton pigment analysis as a tool for monitoring a tropical great lake, Lake Kivu (East Africa)
Publication date :
2021
Journal title :
Inland Waters
ISSN :
2044-2041
eISSN :
2044-205X
Publisher :
Freshwater Biological Association, London, United Kingdom
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