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Diagnostic analysis of the major threats of and proposals for improving its ecological status Lambert Niyoyitungiye

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Lambert Niyoyitungiye. Diagnostic analysis of the major threats of and proposals for improving its ecological status. 2020. ￿hal-02882704￿

HAL Id: hal-02882704 https://hal.archives-ouvertes.fr/hal-02882704 Preprint submitted on 27 Jun 2020

HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. “Diagnostic analysis of the major threats of Lake Tanganyika and proposals for improving its ecological status’’.

By Lambert Niyoyitungiye1*

1 Department of Life Science and Bioinformatics, Assam University, Silchar-788011, Assam State, India.

*Corresponding Author : Lambert Niyoyitungiye Environmental Toxicology Laboratory Department of Life Science & Bioinformatics Assam University, Silchar – 788 011, India Tel: +917086919951; E-mail: [email protected]

1 Background and Topic Significance , in and in . Its waters join the Lake Tanganyika is one of the largest in DRC via the , then the of Africa and second biggest Lake . However, many decisions Considering the area after . in favor of Lake Tanganyika future have Worldwide, it is the longest fresh water lake been taken at the time of the first and holds second position in terms of depth International Conference on Conservation after and third place in terms of and Biodiversity of Lake Tanganyika, held volume after the Caspian Sea and Lake in Burundi- in 1991, where Baikal (Wetzel, 1983 and Kar, 2013). In regional and international scientists were fact, Lake Tanganyika has a volume of 18 present to discuss about the wealth and 3 2 900km , covers an area of 34,000 km with increasing threats of Lake Tanganyika a length of 677 km and a width of 72km and (Cohen, 1991). Despite all these 2 is spread on a watershed of 231,000km . Its initiatives, the lake is still subject to frequent altitude rises to 775m; its average depth fluctuations in the chemistry of its water and is 770m with a maximum of 1433m. Lake to desiccation (Wetzel, 2001) due to sudden Tanganyika is surrounded by four countries changes in weather conditions. It is facing a sharing unequally 1,838km of its entire serious pollution problem from various perimeter (Hanek and al., 1993): Burundi in sources, such as discharge of domestic the North-East controlling 159 km (9% of sewage, population growth, rise of the coast), Democratic.Republic.of.Congo industrialization, use of pesticides and (DRC) to the West with 795 km (43% of the chemical fertilizers in agriculture, coast), Tanzania to the East and South- sedimentation and erosion resulting from East with 669 km (36% of the coast) and deforestation. So, the surface waters of Zambia to the south with 215 km (12% of Lake Tanganyika are highly polluted by the coast). Seven main towns and cities different harmful contaminants from are established on the edge of Lake activities in large cities established on its Tanganyika such as: Baraka, and catchment areas. The Figure1 shows the in DRC, Bujumbura and Rumonge in geographical location of Lake Tanganyika.

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Figure 1: Geographical situation of Lake Tanganyika

2 Main threats of Lake Tanganyika mills, sugar refineries, etc), heavy metals, fuel and oil from boats, pesticides and 2.1 Pollution chemical fertilizers (Patterson G. & Makin Pollution is a major threat to Lake J., 1997). The Large-scale deforestation Tanganyika’s sustainability. Water pollution and unsuitable agricultural practices have occurs when wastes are thrown into water amplified the damage caused by erosion bodies without prior treatment (Nzungu, leading to sedimentary deposition in the 2017). Industrial and municipal Sewage are littoral zone (habitat for organisms). not currently treated before entering into the Turbidity and changes in substrates can lake and the governments of riparian alter habitats, disrupting food chain/web countries do not have legislation to prevent and primary productivity which reducing contamination of the lake. Pollutants include species diversity (Cohen et al., 1993). The domestic wastes (household dirt, Figure2 shows the different types of excrement), industrial wastes (stationery, pollution in Lake Tanganyika. tanneries, slaughterhouses, dairies, oil

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Figure 2: Different types of pollution of Lake Tanganyika: Point-Source of domestic pollution (A), Sedimentary pollution owing to rainy erosion (B), Urban wastewater pollution (C) and Industrial pollution (D).

2.2 Overfishing and use of in 1994-1995 (60 kg/ha/year), 12,900 tons destructive gears for Zambia (69kg/ha/year) and 90,000 tons in Democratic Republic of Congo (34 Overfishing and the use of destructive kg/ha/year). These estimates give an methods alter biological community’s average catch ranging from 54to 66 structure and food chain, and may have kg/ha/year for the whole Lake (Lindqvist et negative socio-economic consequences al., 1999). The observed fishery yields in (Pearce, Petit and Kiyuku, 1995). Studies Burundi (94.5 and 111.5 kg/ha/year, show that fish stocks have already been respectively in 1992 and 1995) are close to drastically reduced through fishing activities the potential yield of 100kg/ha estimated by (Pearce, Petit and Kiyuku, 1995). Annual Coulter (1977). The nocturnal Catch per fish catches recorded on Lake Tanganyika Unit Effort (CPUE) of the commercial units have been on an upward trend since 1970, in Burundi decreased from 166 kg in 1994 currently at around 200 000 tonnes. Recent to 111 kg in 1996, while in Mpulungu it estimates by country indicate a yield of dropped from 877kg in 1994 to 535kg about 21,000 tons for Burundi in 1992 in1996. The decline in catchable stocks of (94.5kg/ha/year), 55,000 tons for Tanzania

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Luciolates stappersii around Mpulungu the commercial catches and the majority of city is not compensated. At the northern the fish caught are juveniles. The figure 3 extremity of the lake, the commercial units shows the Overfishing and use of have stopped their activities and Luciolates destructive gears in Lake Tanganyika. stappersii represents only around 20% of

Figure 3: Overfishing (A) and use of destructive gears (B) in Lake Tanganyika.

2.3 Increase of human population space needed for feeding and reproduction of the lake's biodiversity. In fact, Almost all the Lake Tanganyika's threats hippopotamus populations cannot survive are linked to anthropogenic sources. Lack without the vegetation used for pasture and of education on Lake resources temporary conservation of their babies and conservation, rapid population growth and crocodiles must also have poverty contribute to environmental damage vegetation to protect buried eggs and habitat destruction in the Lake basin. In (Manirakiza, 2017). riparian countries, the annual population growth rate is from 2.5 to 3.1%. This 2.4 Eutrophication gradual increase in demographic pressure Eutrophication is an excessive supply of has forced changes of tropical forest in land nutrients in an aquatic environment leading use to create small agricultural plots to plants proliferation (Algae), bordering Lake Tanganyika. In addition, depletion, fish species depletion, general infrastructures such as hotels and dwelling degradation of water quality and the houses are being built anarchically in the imbalance of the ecosystem.The major supra-littoral zone of Lake Tanganyika nutrients causing eutrophication without prior environmental impact phenomenon are phosphorus (contained in assessment on fragile soils and are phosphates) and nitrogen (contained in subsequently harmful to Lake Tanganyika’s ammonium ions, nitrates and nitrites) environment (Manirakiza, 2017). The (Nzungu, 2017). Eutrophication is thus installation of these infrastructures results in manifested by the appearance of large destruction and degradation of the quantities of algae and other invasive plant bordering vegetation which reduce the species acting by excluding other species in

4 the lake environment. An invasive species catch, aquatic biodiversity and loss of representing the most obvious threat to aesthetic and recreational value of the Lake Tanganyika is Eichhornia crassipes, invaded areas (Bikwemu and Nzigidahera, commonly named “water hyacinth” which 1997). The figure 4 shows the algal grows rapidly and spreads along the shore proliferation leading to green colour of Lake of Lake Tanganyika as well as in the Tanganyika water occurring recently on 10th shallow bays and backwaters of the September 2018 while the figure 5 shows northern extremity of the lake. The Eichhornia crassipes (water hyacinth) on consequences include a reduction of fishes the shores of Lake Tanganyika.

Figure 4: Algal blooms with green colour of Lake Tanganyika water

Figure 5: Proliferation of Eichhornia crassipes along LakeTanganyika shores, nearby Bujumbura port

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3 Conclusion and Scopes for future Minimize the use of pesticides and fertilizers in the Lake Many chemical substances emitted into the Tanganyika catchment by environment from anthropogenic sources promoting sustainable pose a threat to the functioning of aquatic alternatives strategies. ecosystems and to the use of water for  Prevention of eutrophication by limiting various purposes. However, it is imminent supply of phosphorus and nitrates from that the water quality, biodiversity and water runoff, erosion and leaching of natural resources of Lake Tanganyika are fertilized agricultural land leading to an increasingly threatened. The necessity of increase of nutrients stock in Lake strict measures to prevent and control the Tanganyika. release of these substances into the aquatic  Determination of Heavy metals environment has resulted in the concentration accumulated in fish tissue development and implementation of water and some macro-invertebrates to management policies and strategies for the prevent the health risks to human sustainable management and exploitation consumers. of Lake Tanganyika resources. The following strategies are advisable generally 4 References to the governments of riparian countries and especially to the peoples living in the Bikwemu G, Nzigidahera B. (1997). catchment of Lake Tanganyika: Fighting Proliferation of the Floating  Establishing of a monitoring network for Plants in pelagic environment of the continuous analysis of the quality of Lake Tanganyika. the lake's coastal waters as well as the Cohen AS, Bills R, Cocquyt CZ, Caljon rivers and streams flowing into the lake. AG. (1993). The impact of sediment  Determination of the impassable pollution on biodiversity in Lake boundaries for buffer zones around Tanganyika. Conservation Biology. Lake Tanganyika and prohibit the 7: 667-677. construction of dwelling houses and hotels in the buffer zones of Lake Cohen AS. (1991). Report on the First Tanganyika; International Conference on the  Rehabilitation of existing sewage Conservation and Biodiversity of treatment stations and construction of Lake Tanganyika. Biodiversity new stations as human populations is Support Programme,[NP] (USA). ever-increasing in the northern riparian Coulter GW. (1977). Approches to towns of Lake Tanganyika. estimating fish giomass and  Sustainable land management by potential yield in Lake Tanganyika. fighting against deforestation in Lake Journal of fish Biology. 11: 393-408. Tanganyika watershed and promoting alternatives solutions to firewood, Hanek G, Coenen E J, Kotilainen (1993). lumber wood, construction wood and Development of fisheries in Lake charcoal. Tanganyika, Bujumbura-Burundi,  Pollution mitigation: FAO/FINNIDA project. Research for Reduction of urban and industrial development of fisheries in Lake pollution through the collection Tanganyika. GCP/RAF/end/TD.25: and treatment of wastewater and 1-22. solid waste.

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Lindqvist QV, Mölsä H, Salonen K, at Sarvala J. (1999). From Limnology http://www.ltbp.org/FTP/EXEC.PDF. to Fisheries: Lake Tanganyika and Pearce M.J.(1995). Effects of exploitation other Large Lakes. Hydrobiologia. on the pelagic fish community in the 407:1-218. south of Lake Tanganyika. In: Manirakiza (2017). Etat de la Flore et de la Pitcher, T.J., Hart, P.J.B. (eds.).The végétation de La zone littorale du Impacts of Species Changes in Lac Tanganyika et implications pour African Lakes. Chapman and Hall, la Conservation : Cas des zones London. Pp.425-442. inondables de la réserve naturelle Petit P, Kiyuku A. (1995). Changes in the forestière de Kigwena (Burundi), pelagic fisheries of northern Lake Université du Burundi, Mémoire de Tanganyika during the 1980s. In: Master Complémentaire, p15. Pitcher, T.J., Hart, P.J.B. (eds.) the Nzungu (2017). Impact de l‟assainissement Impacts of Species Changes in non collectif en zone sensible sur African Lakes. Chapman and Hall, les eaux du lac Tanganyika: Cas de London. pp. 443-455. la Baie Safari Gate. Prévention et Wetzel R G. (1983). Limnology remédiation des pollutions. Mémoire Philadelphia, Saunders College de Master Complémentaire en Publishing.p858. Sciences de l‟Environnement, Université du Burundi, Bujumbura- Wetzel R G.(2001). Limnology of Burundi. Lake and river ecosystems. San Patterson G, Makin J. (1997). The State of Diego, Academic Press, 3rd Biodiversity in Lake Tanganyika – A edition.p1006. Literature Review: Pollution Control Kar D. (2013). Wetlands and Lakes of the and Other Measures to Protect World. Springer (London). Print Biodiversity in Lake Tanganyika ISBN 978-81-322-1022-1. E-Book (UNDP/GEF/RAF/92/G32) (Natural ISBN: 978-81-322-1923-8. Resources Institute, June)available pp.xxx+687.

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