Seasonal variations and distribution of diatom flora of Lake Ahémé (Benin, West Africa)

Lake Ahémé (part of Ramsar 1017) is one of the most productive brackish water ecosystems and is the second-largest lake in Benin in terms of area, after Lake Nokoué. However, this lake has received little attention for hydrobiological studies, although it is subject to heavy pollution. Therefore, the present study aims to contribute to the monitoring of Lake Ahémé, by assessing the diatom flora. For this purpose, eight sites were surveyed during the dry and wet seasons between September 2014 and 2016. Physico-chemical parameters were measured and diatoms were collected using a phytoplankton net. Margalef, Simpson, Shannon-Weaver, Pielou Equitability and Berger-Parker diversity indices showed significant diversity in Lake Ahémé. The n-MDS and ANOSIM analyses of the diatom communities showed heterogeneity according to seasons and sites. SIMPER analysis revealed that Aulacoseira granulata, Entomoneis paludosa, Nitzschia sigma, Nitzschia linearis, Tryblionella debilis, Thalassiosira lacustris, Cyclotella sp., Iconella capronii, Iconella robusta and Cerataulina bicornis contributed to the changes in diatom community structure. Redundancy analysis showed that temperature, pH, conductivity, total dissolved solids and dissolved oxygen were driving factors in the distribution of diatoms species in Lake Ahémé. The influence of the Atlantic Ocean on Lake Ahémé is noted through the presence of high salinity tolerant species such as Entomoneis paludosa, Nitzschia closterium, Nitzschia sigma and Coscinodiscus wailesii. Further taxonomic research is needed to better understand diatom ecology and species biogeographical distribution.

Publication year:2020

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