Biodiversity and Community Structure of Micro-Arthropods in the Memve’ele Dam, the Tributary River and the River Receiving the Evacuated Turbine Water (South-Cameroon)

Abstract

A survey was undertaken from July 2021 to January 2022 in South-Cameroon on the biodiversity of micro-arthopods in the Memve’ele dam (Site 1), the tributary river (Site 2) and the adjacent river (Sites 3 and 4). Four abiotic parameters were measured <i>in-situ </i>while nine other abiotic parameters were measured in the laboratory using standard methods. Micro-arthopods were counted and identified. Water quality was determined. BOD<sub>5</sub>, conductivity, NO<sub>2</sub><sup>-</sup>, NO<sub>3</sub><sup>-</sup>, pH, PO<sub>4</sub><sup>3-</sup>, temperature and suspended solids were on average within the standards for drinking water. Chlorophyll a, color, DO, NH<sub>4</sub><sup>+</sup> and turbidity values were on average above the standard upper limits. Based on the water quality index (WQI) raw waters were unfit for direct drinking (Dam: WQI=898.864; Site 2: WQI=752.451; Site 3: WQI=883.808; and Site 4: WQI=1,665.883) and presented ideal conditions for fish farming or irrigation for agriculture. A total of 5,487 specimens belonged to three classes, eight orders, 20 families, 57 genera, and 87 species and morphospecies (54 freshwater and 33 tolerant species able to develop in at least two water environments). <i>Ectocyclops</i> sp. was the most recorded species (10.6%), followed by <i>Cyclops</i> sp. (9.1%), <i>Alona costata</i> (8.9%), <i>Mesocyclops</i> sp. (7.9%), <i>Tropocyclops</i> sp. (7.5%), <i>Senecella calanoides</i> (6.8%), <i>Diaphanosoma sarsi</i> (6.1%), while other species were represented each by less than 5.0%. Low species richness, high species diversity and a very low dominance by a few species were noted. Assemblages were highly even (Pielou’s index close to 1). Species exhibited in all sites, a positive global net association. The assemblage recorded during the wet season at Site 3 functioned as a pioneer community (Broken-Stick model) while, the assemblage recorded during the dry season at Site 2 and the one recorded during the dry season at Site 3 functioned as nomocenosis (log-linear or log-normal models) and were therefore little evolved. In contrast, during the two seasons in the dam and Site 4, as well as during the rainy season in Site 2 and the combined seasons in Site 3, the assemblages functioned as highly evolved communities (Zipf or Zipf-models) with significant regenerative force, suggesting that these assemblages maintained a complex information network developed at spatio-temporal scales. The evolved state (close to natural balance) of the micro-arthopods communities should be preserved and protected.