Galloping and anarchic anthropization is degrading more and more the fresh water resources available on the surface. The general objective of the study is to determine the ecology of Uronema elongatum of the current freshwater of the Littoral Region, Cameroon in order to propose its use as a biological indicator of the quality of the rivers of this Region. The specific objectives are: (1) to make a floristic inventory of the algae of some rivers of the Littoral region and to describe the morphology of the species Uronema elongatum; (2) to measure physicochemical parameters associated with these rivers; (3) make a floristic inventory of the macrophytes of these rivers and (4) establish probable correlations. Pelagic algae as well as those attached to stones and macrophytes were sampled. Physicochemical parameters were measured. Uronema elongatum is filamentous with looped chromatophores. Its density decreases with mineral-organic pollution of rivers with a maximum value at the Miana river of 1.250 ind/l. This density is greater on macrophytes and very low or absent on stones. Uronema elongatum has large cells (15 μm) in less polluted rivers and small in highly polluted rivers (5 μm). It emerges that Uronema elongatum is a filamentous, epiphytic, pollu-resistant species that proliferates in the current waters of the Littoral region in Cameroon. This species can be used as an indicator of pollution in this region.

The anarchic and rampant human impact in the city of Douala is the cause of the deterioration of its wetlands. The overall objective of the study is to determine the water quality of Kambo and Longmayagui rivers of Douala located in peri-urban and urban center respectively from Diatoms indexes. Organic materials and stones were sampled in each river. A total of 43 species belonging to 9 families and 22 genera were identified. The Diatom index is 4.0 to Kambo river (site 1) and 6.9 to Longmayagui river (site 2). These indexes show that Kambo river is less polluted, while Longmayagui river is polluted. The most frequent and abundant Diatoms in the samples of the two streams, Batika river characteristics (control) and Kambo can be used as indicators of unpolluted environment. These are : Amphipleura pellucida Kuetzing, Aulacoseira granulata (Ehrenberg) Simonsen, Cymatopleura solea Bourrelly, Cymbella amphicephala Naegeli, Cymbella cesatii (Rabenhorst) Grunow, Cymbella frustula Krammer and Lange-Berthalot, Cymbella naviculiformis Averswald, Diatoma mesodon (Ehrenberg) Kuetzing, Fragilaria capucina (Kuetzing) Lange-Bertalot, Melosira varians JG Agarda, Navicula accomoda Hustedt, Navicula nivalis Ehrenberg, Nitzschia fonticola Grunow, Pinnularia gibba Ehrenberg and Tabellaria flocculosa (Roth) Kuetzing. Monitoring, based on biological indexes of algae could be developed in order to prevent risks of disruption due to various pollutants.

Toxic metals have a polluting with toxic to living organisms even at low concentrations. The overall objective of the study is to determine the impact of some pollutants on the nutritional quality of corn (Zea mays) and potato (Ipomoea batatas) grown mainly in wetlands of Kambo and Longmayagui rivers. Nitrates, phosphates, cadmium and lead were measured in water and in different corn and potato organs grown in the swampy fields Yassa and Arir with 3 repetitions, respectively. The results obtained show that plants produce fields have chlorosis and necrosis and a yellowing of the leaves. Potato tubers rot and show clearly are not consumables. Ears of corn obtained are big but have some spaced seeds. The cadmium content is high in corn seeds 0.10 ± 0.02 mg/kg dry matter and corn tuber 0.08 ± 0.09 mg/kg of dry matter. This content is greater than the tolerance in humans from 0.005 mg/kg dry matter. The lead content is high in the potato tuber 35.00 ± 0.03 mg/kg dry matter and corn 17.00 ± 0.00 mg/kg dry matter. These lead levels are high the threshold of tolerance in different organs of these plants to the standard of 0.05 mg/kg of dry matter. The nitrate and phosphate are higher in potato roots and corn stalks in relation to other organs. The finding of very advanced level of degradation of wetlands Douala directly affecting the nutritional quality of crops shows that it would be desirable that people and governments aware of the pollution on health over the poor quality of products consumer cultures of these lowlands.

The rampant and uncontrolled human impact degrades increasingly freshwater resources available in surface. The overall objective of the study is to determine the diversity and distribution of microalgal périphytics communities Batika and Tongo'o Bassa rivers. The specific objectives are to make a floristic inventory; measure the physicochemical parameters associated with these rivers and to identify their spatial and temporal variations. Organic materials and stones were sampled in each river. A total of 87 species were identified, of which about 39.08% of Diatomophyceae, 26.43% of Chlorophyceae, 11.49% of Cyanophyceae, 09.19% of Zygophyceae, 08.04% of Euglénophyceae, 03.44% of Dinophyceae, 01.14% respectively Chrysophyceae and Prasinophyceae. Diatoms are the most frequent class in samples of river stations. Chlorophyceae are the most dominant class and dense in all stations. The Uronema elongatum, Mougeotia sp. and Oedogonium sp. 1 species are common to all stations. The specific changes in algal communities between stations located upstream from the stations located in the transition and downstream are striking, with a richness and diversity in higher epiphyton station 1 (46 species) and lower the epilithon station 6 (8 species).

Les observations faites dans notre pays notamment dans la ville de Douala montrent que, l’état de ces écosystèmes aquatiques où sont déversées les eaux résiduaires provenant des différents dépotoirs des industries et des agglomérations et même du lessivage des terres environnantes, est assez démonstratif de l’impact de l’action de l’homme. L’objectif du présent travail est d’identifier et d’analyser les différentes formes d’anthropisation, ainsi que leurs effets sur le milieu afin de proposer des solutions de gestions durables. La méthodologie adoptée est celle basée sur les enquêtes et les types d’enquêtes adoptés sont l’enquête en face à face et l’enquête par observation directe. Les résultats des enquêtes ont montré que plus de la moitié des personnes enquêtées se sont installées dans cette zone à cause des difficultés financières. L’inondation apparaît comme la première menace subie par les populations. La majorité des popualtions se sont appuyés sur l’accès facile au site et le faible coût des domaines fonciers pour s’y installer. L’action de déversement des déchets dans le cours d’eau figure parmi les activités anthropiques les plus menées par les personnes ayant déjà été victime d’une catastrophe tandis que la production de la matière plastique se révèle être l’activité qui induis le moins les catastrophes le long du Tongo Bassa. Le remblai constitue la solution première à la prévention contre les catastrophes. Par ailleurs, les activités les plus menées sont l’élevage et l’agriculture et la majorité des personnes effectuant une activité la font sur la rive du cours d’eau. De manière générale, les déchets sont déverser dans les bacs à ordures et la majorité des domiciles possèdent des latrines aménagées situées loin de la rive. Plus de la moitié de la population enquêtée connait les noms des espèces végétales et les utiliser à des fins alimentaires. La proposition du drainage du cours d’eau est la plus avancée par les personnes enquêtées.

Demographic change is responsible for the degradation of wetlands Douala. The overall objective of the study is to analyze the impact of uncontrolled human impact on the lives of people and vegetation located in the neighborhoods of Kambo and Longmayagui rivers (Douala). Interviews with heads of district and surveys of the local population have been made. In total 1 314 boxes were counted (125 boxes in Kambo and 1 189 boxes in Longmayagui). Seventy-five people were surveyed in Kambo (60 %) and 450 people in Longmayagui (37.84 %). The local population is mainly originally from western Cameroon. The main reason she moved into these areas is poverty. She practices mainly agriculture on the banks of Longmayagui and Kambo rivers and dump all their waste into rivers. The plants are invasive and regularly cleared it. These plants are useful to local residents for food and traditional medicine. The management of these areas is not a matter for policy makers but each riparian without any help is doing in managing its space. The interviews and surveys have highlighted the complexity of interactions between actors. Respondents are aware: they identify the environmental, social, political and territorial raised by the management of risk areas.