Article (Scientific journals)
Spatial and temporal variations of dissolved CO2, CH4 and N2O in Lakes Edward and George (East Africa)
Borges, Alberto; Okello, William; Bouillon, Steven et al.
2023In Journal of Great Lakes Research, 49 (1), p. 229-245
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Keywords :
CO2, CH4, N2O, Lake Edward, Lake George
Abstract :
[en] We report dissolved CO2, CH4 and N2O concentrations in two large East African Rift lakes, Edward (surface area 2,325 km2, average depth of 37 m) and George (surface area 273 km2, average depth of 2 m). Lake George showed modest seasonal and spatial variations, and lower partial pressure of CO2 (pCO2) (26±16 ppm, mean±standard deviation), CH4 (234±208 nmol L-1) and N2O saturation levels (%N2O) (80±9%) than Lake Edward (404±145 ppm, 357±483 nmol L-1, 139±222%). Surface waters in both lakes were over-saturated in CH4, and Lake George was under-saturated in CO2 while Lake Edward was slightly over-saturated in CO2. This difference was related to higher phytoplankton biomass in Lake George than Lake Edward, with average chlorophyll-a concentrations of 177±125 and 18±25 µg L-1, respectively. Permanent high cyanobacterial biomass in Lake George led to uniform dissolved CO2, CH4 and N2O concentrations. In surface waters of Lake Edward, spatial variations of pCO2, CH4 and N2O were related to bottom depth, and locally (in particular in Katwe Bay) also related to the inputs of water from Lake George via the Kazinga Channel, a 40-km natural channel connecting the lakes. Short-term mixing events related to storms increased CO2, CH4 and N2O content in surface waters, in particular for CH4 and N2O. This indicates that mixing events in response to storms can create ‘hot moments’ for CH4 and N2O emissions to the atmosphere in tropical lakes, given the weaker vertical density gradients compared to higher latitude systems.
Research center :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Borges, Alberto  ;  Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Okello, William
Bouillon, Steven
Deirmendjian, Loris
Nankabirwa, Angela
Nabafu, Erina
Lambert, Thibault
Descy, Jean-Pierre ;  Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Morana, Cédric ;  Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Language :
English
Title :
Spatial and temporal variations of dissolved CO2, CH4 and N2O in Lakes Edward and George (East Africa)
Publication date :
01 February 2023
Journal title :
Journal of Great Lakes Research
ISSN :
0380-1330
eISSN :
2773-0719
Volume :
49
Issue :
1
Pages :
229-245
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
HIPE
AFRIVAL
Available on ORBi :
since 28 November 2022

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