Articles | Volume 30, issue 9
https://doi.org/10.5194/hess-30-2543-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/hess-30-2543-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Leveraging 20 years of remote sensing to characterize surface phytoplankton seasonality and long-term trends in lake Tanganyika
François Toussaint
CORRESPONDING AUTHOR
Earth and Life Institute – Environmental Sciences (ELIE), Faculty of Biosciences Engineering, UCLouvain, Croix du Sud 2, L7.05.02, 1348 Louvain-la-Neuve, Belgium
Alice Alonso
Earth and Life Institute – Environmental Sciences (ELIE), Faculty of Biosciences Engineering, UCLouvain, Croix du Sud 2, L7.05.02, 1348 Louvain-la-Neuve, Belgium
Marnik Vanclooster
Earth and Life Institute – Environmental Sciences (ELIE), Faculty of Biosciences Engineering, UCLouvain, Croix du Sud 2, L7.05.02, 1348 Louvain-la-Neuve, Belgium
Related authors
No articles found.
Elise Verstraeten, Alice Alonso, Louise Collier, and Marnik Vanclooster
Hydrol. Earth Syst. Sci., 29, 1829–1845, https://doi.org/10.5194/hess-29-1829-2025, https://doi.org/10.5194/hess-29-1829-2025, 2025
Short summary
Short summary
This study takes a data-driven approach to evaluate long-term groundwater nitrate concentration trends in Wallonia, Belgium, over ~20 years following the implementation of regional nitrogen management policies. Results highlight a persistently negative impact of agricultural land use, the importance of sustained policies and long-term monitoring to mitigate nitrogen legacy effects, and the need for improved datasets to better capture controlling factors.
Damien Delforge, Olivier de Viron, Marnik Vanclooster, Michel Van Camp, and Arnaud Watlet
Hydrol. Earth Syst. Sci., 26, 2181–2199, https://doi.org/10.5194/hess-26-2181-2022, https://doi.org/10.5194/hess-26-2181-2022, 2022
Short summary
Short summary
Causal inference methods (CIMs) aim at identifying causal links from temporal dependencies found in time-series data. Using both synthetic data and real-time series from a karst system, we study and discuss the potential of four CIMs to reveal hydrological connections between variables in hydrological systems. Despite the ever-present risk of spurious hydrological connections, our results highlight that the nonlinear and multivariate CIM has a substantially lower false-positive rate.
Issoufou Ouedraogo and Marnik Vanclooster
Proc. IAHS, 384, 69–74, https://doi.org/10.5194/piahs-384-69-2021, https://doi.org/10.5194/piahs-384-69-2021, 2021
Short summary
Short summary
The results of the study have shed light on the pollution problem of groundwater at the pan-African scale. We demonstrated the unambiguous link between population density (urban areas, agricultural activity) and pollution of groundwater. We showed that the machine learning techniques are promising for modelling groundwater degradation at the African scale because of its ability to provide meaningful analysis of nonlinear and complex relationships such as those found in hydrogeological studies.
Cited articles
Adrian, R., O'Reilly, C. M., Zagarese, H., Baines, S. B., Hessen, D. O., Keller, W., Livingstone, D. M., Sommaruga, R., Straile, D., Van Donk, E., Weyhenmeyer, G. A., and Winder, M.: Lakes as sentinels of climate change, Limnol. Oceanogr., 54, 2283–2297, https://doi.org/10.4319/lo.2009.54.6_part_2.2283, 2009.
Alvera-Azcárate, A., Barth, A., Rixen, M., and Beckers, J. M.: Reconstruction of incomplete oceanographic data sets using empirical orthogonal functions: Application to the Adriatic Sea surface temperature, Ocean Model., 9, 325–346, https://doi.org/10.1016/j.ocemod.2004.08.001, 2005.
Beckers, J. M. and Rixen, M.: EOF Calculations and Data Filling from Incomplete Oceanographic Datasets, J Atmos Ocean Technol, 20, 1839–1856, https://doi.org/10.1175/1520-0426(2003)020<1839:ECADFF>2.0.CO;2, 2003.
Bergamino, N., Loiselle, S. A., Cózar, A., Dattilo, A. M., Bracchini, L., and Rossi, C.: Examining the dynamics of phytoplankton biomass in Lake Tanganyika using Empirical Orthogonal Functions, Ecol. Modell., 204, 156–162, https://doi.org/10.1016/j.ecolmodel.2006.12.031, 2007.
Bergamino, N., Horion, S., Stenuite, S., Cornet, Y., Loiselle, S., Plisnier, P. D., and Descy, J. P.: Spatio-temporal dynamics of phytoplankton and primary production in Lake Tanganyika using a MODIS based bio-optical time series, Remote Sens. Environ., 114, 772–780, https://doi.org/10.1016/j.rse.2009.11.013, 2010.
Brönmark, C. and Hansson, L. A.: Environmental issues in lakes and ponds: Current state and perspectives, Environ. Conserv., 29, 290–307, https://doi.org/10.1017/S0376892902000218, 2002.
Bulengela, G.: “I am a Fisher”: Identity and livelihood diversification in Lake Tanganyika Fisheries, Tanzania, Mar. Technol. Res., 6, 268718, https://doi.org/10.33175/mtr.2024.268718, 2024.
Carrea, L., Crétaux, J. F., Liu, X., Wu, Y., Bergé-Nguyen, M., Calmettes, B., Duguay, C. R., Jiang, D., Merchant, C. J., Mueller, D., Selmes, N., Simis, S., Spyrakos, E., Stelzer, K., Warren, M., Yesou, H., and Zhang, D.: ESA Lakes Climate Change Initiative (Lakes_cci): Lake products, Version 2.1., https://doi.org/10.1038/s41597-022-01889-z, 2024.
Cohen, A. S., Gergurich, E. L., Kraemer, B. M., McGlue, M. M., McIntyre, P. B., Russell, J. M., Simmons, J. D., and Swarzenski, P. W.: Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems, P. Natl. Acad. Sci. USA, 113, 9563–9568, https://doi.org/10.1073/pnas.1603237113, 2016.
Corman, J. R., Mcintyre, P. B., Kuboja, B., Mbemba, W., Fink, D., Wheeler, C. W., Gans, C., Michel, E., and Flecker, A. S.: Upwelling couples chemical and biological dynamics across the littoral and pelagic zones of Lake Tanganyika, East Africa, Limnol. Oceanogr., 1, 214–224, https://doi.org/10.4319/lo.2010.55.1.0214, 2010.
Coulter, G. W.: Lake Tanganyika and its life, Oxford University Press, Oxford, UK, ISBN 0-19-858525X, 1991.
Descy, J. P., Hardy, M. A., Sténuite, S., Pirlot, S., Leporcq, B., Kimirei, I., Sekadende, B., Mwaitega, S. R., and Sinyenza, D.: Phytoplankton pigments and community composition in Lake Tanganyika, Freshw. Biol., 50, 668–684, https://doi.org/10.1111/j.1365-2427.2005.01358.x, April 2005.
Descy, J. P., Tarbe, A. L., Stenuite, S., Pirlot, S., Stimart, J., Vanderheyden, J., Leporcq, B., Stoyneva, M. P., Kimirei, I., Sinyinza, D., and Plisnier, P. D.: Drivers of phytoplankton diversity in Lake Tanganyika, Hydrobiologia, 653, 29–44, https://doi.org/10.1007/s10750-010-0343-3, 2010.
Gbetkom, P. G., Crétaux, J. F., Biancamaria, S., Blazquez, A., Paris, A., Tchilibou, M., Gal, L., Kitambo, B., Jucá Oliveira, R. A., and Gosset, M.: Lake Tanganyika basin water storage variations from 2003–2021 for water balance and flood monitoring, Remote Sens. Appl., 34, https://doi.org/10.1016/j.rsase.2024.101182, 2024.
Gordon, H. R. and Wang, M.: Retrieval of water-leaving radiance and aerosol optical thickness over the oceans with SeaWiFS: a preliminary algorithm, Appl. Opt., 33, 443–452, https://doi.org/10.1364/AO.33.000443, 1994.
Hecky, R. E. and Fee, E. J.: Primary production and rates of algal growth in Lake Tanganyika, Limnol. Oceanogr., 26, 532–547, https://doi.org/10.4319/lo.1981.26.3.0532, 1981.
Hecky, R. E. and Kling, I.-I. J.: The phytoplankton and protozooplankton of the euphotic zone of Lake Tanganyika: Species composition, biomass, chlorophyll content, and spatio-temporal distribution, Limnol. Oceanogr., 26, 548–564, https://doi.org/10.4319/lo.1981.26.3.0548, 1981.
Horion, S., Bergamino, N., Stenuite, S., Descy, J.-P., Plisnier, P.-D., Loiselle, S. A., and Cornet, Y.: Optimized extraction of daily bio-optical time series derived from MODIS/Aqua imagery for Lake Tanganyika, Africa, Remote Sens. Environ., 114, 781–791, https://doi.org/10.1016/j.rse.2009.11.012, 2010.
Hu, C. and Campbell, J.: Oceanic Chlorophyll a Content, in: Biophysical Applications of Satellite Remote Sensing, edited by: Hanes, J., Springer, 171–203, https://doi.org/10.1007/978-3-642-25047-7_7, 2014.
Kraemer, B. M., Hook, S., Huttula, T., Kotilainen, P., O'Reilly, C. M., Peltonen, A., Plisnier, P. D., Sarvala, J., Tamatamah, R., Vadeboncoeur, Y., Wehrli, B., and McIntyre, P. B.: Century-long warming trends in the upper water column of lake tanganyika, PLoS One, 10, https://doi.org/10.1371/journal.pone.0132490, 2015.
Kutser, T.: Passive optical remote sensing of cyanobacteria and other intense phytoplankton blooms in coastal and inland waters, Int. J. Remote Sens., 30, 4401–4425, https://doi.org/10.1080/01431160802562305, 2009.
Laliberté, J. and Larouche, P.: Chlorophyll a concentration climatology, phenology, and trends in the optically complex waters of the St. Lawrence Estuary and Gulf, J. Mar. Syst., 238, 103830, https://doi.org/10.1016/j.jmarsys.2022.103830, 2023.
Langenberg, V. T., Mwape, L. M., Tshibangu, K., Tumba, J. M., Koelmans, A. A., Roijackers, R., Salonen, K., Sarvala, J., and Mölsä, H.: Comparison of thermal stratification, light attenuation, and chlorophyll a dynamics between the ends of Lake Tanganyika, Aquat. Ecosyst. Health Manag., 5, 255–265, https://doi.org/10.1080/14634980290031956, 2002.
Langenberg, V. T., Sarvala, J., and Roijackers, R.: Effect of wind induced water movements on nutrients, chlorophyll a, and primary production in Lake Tanganyika, Aquat Ecosyst Health Manag., 6, 279–288, https://doi.org/10.1080/14634980301488, 2003.
Lombard, F., Boss, E., Waite, A. M., Uitz, J., Stemmann, L., Sosik, H. M., Schulz, J., Romagnan, J. B., Picheral, M., Pearlman, J., Ohman, M. D., Niehoff, B., Möller, K. O., Miloslavich, P., Lara-Lopez, A., Kudela, R. M., Lopes, R. M., Karp-Boss, L., Kiko, R., Jaffe, J. S., Iversen, M. H., Irisson, J. O., Hauss, H., Guidi, L., Gorsky, G., Giering, S. L. C., Gaube, P., Gallager, S., Dubelaar, G., Cowen, R. K., Carlotti, F., Briseño-Avena, C., Berline, L., Benoit-Bird, K. J., Bax, N. J., Batten, S. D., Ayata, S. D., and Appeltans, W.: Globally consistent quantitative observations of planktonic ecosystems, Front. Mar. Sci., 6, https://doi.org/10.3389/fmars.2019.00196, 2019.
Macintyre, S.: Climatic Variability, Mixing Dynamics, and Ecological Consequences in the African Great Lakes, in: Climatic Change and Global Warming of Inland Waters: Impacts and Mitigation for Ecosystems and Societies, edited by: Charles R. Goldman, Michio Kumagai, and Richard D. Robarts, John Wiley and Sons, Ltd., 311–336, https://doi.org/10.1002/9781118470596.ch18, 2012.
MacQueen, J.: Some methods for classification and analysis of multivariate observations, in: Proceedings of the Fifth Berkeley Symposium on Mathematical Statistics and Probability, Vol. 1, University of California Press, Berkeley, 281–297, https://projecteuclid.org/euclid.bsmsp/1200512992 (last access: 28 April 2026), 1967.
Martin, Seelye.: An introduction to ocean remote sensing, Cambridge University Press, 496 pp., https://doi.org/10.1017/CBO9781139094368, 2014.
McClain, C. R., Hooker, S., Feldman, G., and Bontempi, P.: Satellite Data for Ocean Biology, Biogeochemistry, and Climate Research, Eos, 87, 337–343, https://doi.org/10.1029/2005GL024310, 2006.
Mölsä, H., Sarvala, J., Badende, S., Chitamwebwa, D., Kanyaru, R., Mulimbwa, M., and Mwape, L.: Ecosystem monitoring in the development of sustainable fisheries in Lake Tanganyika, Aquat. Ecosyst. Health Manag., 5, 267–281, https://doi.org/10.1080/14634980290031965, 2002.
Moore, T. S., Dowell, M. D., Bradt, S., and Ruiz Verdu, A.: An optical water type framework for selecting and blending retrievals from bio-optical algorithms in lakes and coastal waters, Remote Sens. Environ., 143, 97–111, https://doi.org/10.1016/j.rse.2013.11.021, 2014.
Moses, W. J., Gitelson, A. A., Berdnikov, S., and Povazhnyy, V.: Estimation of chlorophyll a concentration in case II waters using MODIS and MERIS data - Successes and challenges, Environ. Res. Lett, 4, 045005, https://doi.org/10.1088/1748-9326/4/4/045005, 2009.
Naithani, J., Deleersnijder, E., and Plisnier, P. D.: Origin of intraseasonal variability in Lake Tanganyika, Geophys. Res. Lett., 29, https://doi.org/10.1029/2002GL015843, 2002.
Neil, C., Spyrakos, E., Hunter, P. D., and Tyler, A. N.: A global approach for chlorophyll a retrieval across optically complex inland waters based on optical water types, Remote Sens. Environ., 229, 159–178, https://doi.org/10.1016/j.rse.2019.04.027, 2019.
Nicholson, S. E.: The nature of rainfall variability over Africa on time scales of decades to millenia, Glob. Planet Chang., 26, 137–158, https://doi.org/10.1016/S0921-8181(00)00040-0, 2000.
Niyongabo, A., Zhang, D., Guan, Y., Wang, Z., Imran, M., Nicayenzi, B., Guyasa, A. K., and Hatungimana, P.: Predicting Urban Water Consumption and Health Using Artificial Intelligence Techniques in Tanganyika Lake, East Africa, Water, 16, https://doi.org/10.3390/w16131793, 2024.
O'Reilly, C. M., Alin, S. R., Piisnier, P. D., Cohen, A. S., and McKee, B. A.: Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa, Nature, 424, 766–768, https://doi.org/10.1038/nature01833, 2003.
Paffen, P., Coenen, E., Bambara, S., Wa Bazolana, M., Lyimo, E., and Lukwesa, C.: Synthesis of the 1995 simultaneous frame survey of Lake Tanganyika fisheries, FAO/FINNIDA Research for the Management of the Fisheries on Lake Tanganyika, GCP/RAF/271/FIN–TD/60 (En), 22 pp., https://www.fao.org/fishery/static/LTR/FTP/TD60.PDF (last access: 28 April 2026), 1997.
Papa, F., Crétaux, J. F., Grippa, M., Robert, E., Trigg, M., Tshimanga, R. M., Kitambo, B., Paris, A., Carr, A., Fleischmann, A. S., de Fleury, M., Gbetkom, P. G., Calmettes, B., and Calmant, S.: Water Resources in Africa under Global Change: Monitoring Surface Waters from Space, Surv. Geophys., 44, 43–93, https://doi.org/10.1007/s10712-022-09700-9, 2023.
Plisnier, P.-D. and Coenen, E. J.: Pulsed and Dampened Annual Limnological Fluctuations in Lake Tanganyika, in: The Great Lakes of the World (GLOW), edited by: Munawar, M. and Hecky, R. E., Michigan State University Press, 8396, https://doi.org/10.14321/j.ctt1bqzmb5.11, 2001.
Plisnier, P.-D., Poncelet, N., Cocquyt, C., De Boeck, H., Bompangue, D., Naithani, J., Jacobs, J., Piarroux, R., Moore, S., Giraudoux, P., Batumbo, D., Mushagalusa, D., Makasa, L., Deleersnijder, E., Tomazic, I., and Cornet, Y.: Cholera outbreaks at Lake Tanganyika induced by climate change? – “CHOLTIC”, final report, Belgian Science Policy, Brussels, 117 pp., https://www.belspo.be/belspo/SSD/science/Reports/CHOLTIC_FinRep.pdf (last access: 28 April 2026), 2015.
Plisnier, P., Nshombo, M., Mgana, H., and Ntakimazi, G.: Monitoring climate change and anthropogenic pressure at Lake Tanganyika, J. Great Lakes Res., 44, 1194–1208, https://doi.org/10.1016/j.jglr.2018.05.019, 2018.
Plisnier, P., Kayanda, R., MacIntyre, S., Obiero, K., Okello, W., Vodacek, A., Cocquyt, C., Abegaz, H., Achieng, A., Akonkwa, B., Albrecht, C., Balagizi, C., Barasa, J., Abel Bashonga, R., Bashonga Bishobibiri, A., Bootsma, H., Borges, A. V., Chavula, G., Dadi, T., De Keyzer, E. L. R., Doran, P. J., Gabagambi, N., Gatare, R., Gemmell, A., Getahun, A., Haambiya, L. H., Higgins, S. N., Hyangya, B. L., Irvine, K., Isumbisho, M., Jonasse, C., Katongo, C., Katsev, S., Keyombe, J., Kimirei, I., Kisekelwa, T., Kishe, M., Otoung A. Koding, S., Kolding, J., Kraemer, B. M., Limbu, P., Lomodei, E., Mahongo, S. B., Malala, J., Mbabazi, S., Masilya, P. M., McCandless, M., Medard, M., Migeni Ajode, Z., Mrosso, H. D., Mudakikwa, E. R., Mulimbwa, N., Mushagalusa, D., Muvundja, F. A., Nankabirwa, A., Nahimana, D., Ngatunga, B. P., Ngochera, M., Nicholson, S., Nshombo, M., Ntakimazi, G., Nyamweya, C., Ikwaput Nyeko, J., Olago, D., Olbamo, T., O'Reilly, C. M., Pasche, N., Phiri, H., Raasakka, N., Salyani, A., Sibomana, C., Silsbe, G. M., Smith, S., Sterner, R. W., Thiery, W., Tuyisenge, J., Van der Knaap, M., Van Steenberge, M., van Zwieten, P. A. M., Verheyen, E., Wakjira, M., Walakira, J., Ndeo Wembo, O., and Lawrence, T.: Need for harmonized long-term multi-lake monitoring of African Great Lakes, J. Great Lakes Res., 49, https://doi.org/10.1016/j.jglr.2022.01.016, 2023a.
Plisnier, P., Cocquyt, C., Cornet, Y., Poncelet, N., Nshombo, M., Ntakimazi, G., Nahimana, D., Makasa, L., and MacIntyre, S.: Phytoplankton blooms and fish kills in Lake Tanganyika related to upwelling and the limnological cycle, J. Great Lakes Res., 49, https://doi.org/10.1016/j.jglr.2023.102247, 2023b.
Plisnier, P.-D., Chitamwebwa, D., Mwape, L., Tshibangu, K., Langenberg, V., and Coenen, E.: Limnological annual cycle inferred from physical-chemical fluctuations at three stations of Lake Tanganyika, Hydrobiologia, 407, 45–58, https://doi.org/10.1023/A:1003762119873, 1999.
Rousseeuw, P. J.: Silhouettes: a graphical aid to the interpretation and validation of cluster analysis, J. Comput. Appl. Math., 20, 53–65, https://doi.org/10.1016/0377-0427(87)90125-7, 1987.
Salonen, K., Sarvala, J., Järvinen, M., Langenberg, V., Nuottajärvi, M., Vuorio, K., and Chitamwebwa, and D. B. R.: Phytoplankton in Lake Tanganyika-vertical and horizontal distribution of in vivo fluorescence, Hydrobiologia, 407, 89–103, https://doi.org/10.1023/A:1003764825808, 1999.
Sen, P. K.: Estimates of the Regression Coefficient Based on Kendall's Tau, J. Am. Stat. Assoc., 63, 1379–1389, https://doi.org/10.1080/01621459.1968.10480934, 1968.
Stenuite, S., Pirlot, S., Hardy, M. A., Sarmento, H., Tarbe, A. L., Leporcq, B., and Descy, J. P.: Phytoplankton production and growth rate in Lake Tanganyika: Evidence of a decline in primary productivity in recent decades, Freshw. Biol., 52, 2226–2239, https://doi.org/10.1111/j.1365-2427.2007.01829.x, 2007.
Tierney, J. E., Mayes, M. T., Meyer, N., Johnson, C., Swarzenski, P. W., Cohen, A. S., and Russell, J. M.: Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500, Nat. Geosci., 3, 422–425, https://doi.org/10.1038/ngeo865, 2010.
Van Bocxlaer, B., Schultheiß, R., Plisnier, P. D., and Albrecht, C.: Does the decline of gastropods in deep water herald ecosystem change in Lakes Malawi and Tanganyika?, Freshw. Biol., 57, 1733–1744, https://doi.org/10.1111/j.1365-2427.2012.02828.x, 2012.
Verburg, P. and Hecky, R. E.: The physics of the warming of Lake Tanganyika by climate change, Limnol. Oceanogr., 54, 2418–2430, https://doi.org/10.4319/lo.2009.54.6_part_2.2418, 2009.
Verburg, P., Hecky, R. E., and Kling, H.: Ecological consequences of a century of warming in Lake Tanganyika, Science, 301, 505–507, https://doi.org/10.1126/science.1084846, 2003.
Vuorio, K., Nuottajärvi, M., Salonen, K., and Sarvala, J.: Spatial distribution of phytoplankton and picocyanobacteria in Lake Tanganyika in March and April 1998, Aquat. Ecosyst. Health Manag., 6, 263–278, https://doi.org/10.1080/14634980301494, 2003.
Wetzel, R. G.: Limnology: Lake and River Ecosystems, Third Edition., Academic Press, San Diego, 1006 pp., https://doi.org/10.1016/C2009-0-02112-6, 2001.
Williamson, C. E., Saros, J. E., Vincent, W. F., and Smol, J. P.: Lakes and reservoirs as sentinels, integrators, and regulators of climate change, Limnol. Oceanogr., 54, 2273–2282, https://doi.org/10.4319/lo.2009.54.6_part_2.2273, 2009.
Xu, F.-L., Tao, S., Dawson, R. W., Li, P.-G., and Cao, J.: Lake Ecosystem Health Assessment: Indicators and Methods, Water Res., 35, 3157–3167, https://doi.org/10.1016/S0043-1354(01)00040-9, 2001.
Short summary
We analysed 20 years of satellite data to study changes in surface phytoplankton concentration in Lake Tanganyika. Results reveal strong seasonal patterns linked to known hydrodynamics, with decreasing levels in deep areas and increases in shallow regions. These changes could alter the lake’s ecosystem and threaten the resources that millions of people rely on.
We analysed 20 years of satellite data to study changes in surface phytoplankton concentration...