Observation of Eunotia enigmatica (Bacillariophyta), a rare South-American diatom species, in the Congo Basin, tropical Africa

ABSTRACT

In material collected in the Losambila river, a small tributary of the Congo River at Yangambi (Tshopo Province, Democratic Republic of the Congo), an unusual Eunotia species was observed. The same taxon was also detected in material taken at the beginning of 2018 in a small tributary of the Luapula river in the Haut-Katanga Province in the South of DR Congo. We could identify it as Eunotia enigmatica, recently described from reservoirs in south-eastern Brazil. The valve morphology of the Congolese material is compared with the Brazilian. E. enigmatica was not observed frequently but was not rare either. In two samples of the Losambila river this taxon reached up to 5.6 and 5.4 % of the total diatom assemblage. It is not the only species with a distribution known from Africa and South-America observed in the Losambila River. Encyonopsis frequentis, also described from South America, was more common than E. enigmatica in samples collected in the Tshopo Province, and reached up to 16.8% of the total diatom composition in the Losambila river. However, Encyonopsis frequentis was not observed in the samples where E. enigmatica was present. The same applies to the material from the tributary of the Luapula river where Encyonopsis frequentis was not found in the sample where E. enigmatica was present.

KEYWORDS:

• Eunotia enigmatica
• DR Congo
• Encyonopsis frequentis
• diatoms
• taxonomy

Acknowledgments

The authors are grateful to Dr. André De Kesel (Meise Botanic Garden) for providing the authors material from the tributary of the Luapula River, DR Congo, and to Myriam de Haan and Laetitia Caljon for the technical assistance. Many thanks also to the staff of INERA-Yangambi, to all members of the sampling campaign and to the people from the village of Ekutsu for their support, making the sampling possible and successful.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is resulting from the FORETS (Formation, Recherche et Environnement dans la Tshopo) project coordinated by the Center for International Forestry Research (CIFOR) and financed by the European Union. 

Notes on contributors

Christine Cocquyt

Christine Cocquyt has been studying phytoplankton and diatoms in tropical Africa for almost four decades. Besides diatom taxonomy, she is involved in palaeo-limnologic investigations in East Africa and the Sahara region in Chad.

Contribution: lead investigator of this paper making all LM and SEM observations, and preparing the manuscript.

Jacob Mambweni Makaya

Jacob Mambweni Makaya is an agricultural engineer and responsible for the hydrobiology laboratory of INERA -Yangambi (DR Congo), National Program of Natural Resources Management and Conservation Research at the Forestry Section. Recently he started diatom investigation in Yangambi (DR Congo) to determine the water quality of small rivers in the Yangambi Biosphere Reserve.

Contribution: sampling of the material in Lake Makako and first screening of the permanent microscopic slides.

Mamie Ngendja Kabitoma

Mamie Ngendja Kabitoma is an agricultural engineer doing research on Rice at INERA -Yangambi (DR Congo). Recently she started diatom investigation in Yangambi (DR Congo) to determine the water quality of small rivers in the Yangambi Biosphere Reserve.

Contribution: sampling of the material in Lake Makako and first screening of permanent microscopic slides.