Spatio-temporal patterns and taxonomy of cladocerans (Crustacea) in the Congo River and its main tributaries

• Grant number: 22/08926-9
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2023
• End date: November 30, 2024
• Field of knowledge: Biological Sciences - Ecology - Ecosystems Ecology
• Principal Investigator: Gilmar Perbiche Neves
• Grantee: Camila Moreira da Silva
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated scholarship(s): 23/10648-0 - Dispersion, extinction and evolution of microcrustacean zooplankton at an intercontinental scale, BE.EP.MS

Abstract

Understanding the dynamics of aquatic taxonomic groups, such as zooplankton, allows finding patterns and effects correlated with different environmental variables, aiming to recognize study priorities for water resources, in order to optimize their use and management. In addition, new studies in precarious regions with scarce knowledge are essential, which will allow the recognition of areas with potential for conservation and incentives for new studies. This project aims to analyze the taxonomic structure, abundance, diversity and spatial and seasonal distribution of cladocerans (Crustacea, Branchiopoda), seeking to understand the main regional and local changes in the Congo River (Africa). The following hypotheses will be tested: I. The main river presents greater abundances and equitability, unlike the tributaries, as well as presenting greater alpha diversity; II. The dissimilarity will be greater in the main river than in the tributaries, as well as the beta diversity also higher, but with reduced dominance in the same area; III. In the low water period, species richness will be positively affected, in order to present higher values in the whole extension, including the main river and the tributaries, while in the high water period there will be less abundance; IV. The high values of nutrients and chlorophyll-a will reflect in high species richness, but the opposite will occur with higher values of total carbon and lower pH; V. Gamma diversity, influenced by alpha and beta diversity, will present greater value in points with greater depth, regardless of their position. Three campaigns were carried out along 1,700 km of the Congo River, distributed in the high and low months. These are 57 points, with five replicas at the points, obtained through the 10-liter Schindler-Patalas trap. Physical and chemical variables were measured in situ (dissolved oxygen, pH and conductivity, transparency and depth. In the laboratory, the concentrations of total suspended solids, particulate and dissolved organic carbon, nutrients and chlorophyll-a were measured). The cladoceran samples will be analyzed (qualitatively and quantitatively) with the help of specialized bibliography, stereoscopes and microscopes, in addition to the help of other specialist researchers. A new species of the genus Kurzia Dybowski & Grochowski, 1894, already found in the initial screenings, will be described following barcoding sequencing (COI) methodologies, in addition to describing structures through illustrations and photographic records. The data obtained will be analyzed statistically to verify the differences in composition between the central channel and the tributaries, as well as descriptive statistics (means, medians, standard deviation and variance), ecological indices (richness, diversity - alpha with richness, Shannon-Wiener and Simpson, beta with Sorensen and gamma), dominance, evenness, and abundance), differences between campaigns and sampling points (using permutational analysis of variance), and ordered Bray-Curtis dissimilarity in a non-metric multidimensional scaling analysis. The correlation of cladoceran abundance with limnological variables will be performed with a redundancy analysis based on distance (using Bray-Curtis dissimilarity) and principal coordinate analysis, and diversity indices will be calculated, in addition to using the TITAN analysis ( Analysis of Threshold Indicators), to detect the pattern and potential bioindicator of taxa. The data and results will be published in repositories and in two articles to be submitted to journals with a high impact factor (one on ecology and the other describing the new species), in addition to presentations at national and international scientific events. The results will provide a first database on the cladocerans of this important river, including taxonomic and ecological information.