Relationship between Physicochemical Parameters and Copepod Community Structure in the Tinguilinta River Estuary (Boké, Guinea)

Abstract

This study investigates the spatio-temporal distribution of copepods (zooplankton) in the Tinguilinta River estuary, in relation to water physicochemical parameters, during the dry and rainy seasons across fifteen sampling stations. Field sampling was conducted for both physicochemical and biological analyses. The physical and chemical properties of the water were measured in the laboratory. Copepods were collected using a plankton net with a mesh size of 55 µm. Thirty copepod species were identified under the microscope, belonging to four orders and sixteen families, with a marked predominance of Calanoids (77.34%). Overall, the lowest taxonomic richness and abundance were recorded at station S7 during the dry season, while the highest values occurred at station S1 during the rainy season. Species diversity assessed using the Shannon-Weaver index (H′), remained relatively consistent among stations, with lower values observed at S12 (1.97) and S14 (2.00), and higher values at S1 (2.97), S2 (2.93), and S4 (2.92). The evenness index (E′) ranged between 0.81 and 0.97, indicating a more balanced distribution of species at station S15. Principal component analysis (PCA) proved effective in discriminating physicochemical variables and highlighting ecological gradients. The analysis distinguished three groups of stations, differentiated by their respective states of imbalance. Redundancy analysis (RDA) further revealed that dissolved oxygen, salinity, conductivity, temperature, and pH are the main drivers influencing taxonomic diversity and abundance. Overall, this study demonstrates the influence of environmental variables on copepod community distribution across the fifteen estuarine stations and supports the use of copepods as potential bioindicators of pollution.