Diversity of aquatic macroinvertebrates in relationship with the environmental factors of a lotic ecosystem in tropical region: the Sô river in South-East of Benin (West Africa)

International audienceThe present study was aimed to study the diversity of aquatic macroinvertebrate populations in relation to the abiotic parameters of the Sô River. For this purpose, aquatic macroinvertebrates were sampled monthly between February 2016 and April 2017 on 12 sampling stations and in various habitats along the Sô River. Similarly, twenty environmental variables were measured to assess the environmental characteristics of Sô river. The recorded fauna consists of 2053 individuals corresponding to 44 families and 61 taxa belonging to three main zoological groups (Arthropods, Molluscs, Annelids). The stand population showed that Coleoptera (17.06%), Basomatophora (14.19%), Heteroptera (11.37%), Odonata (10.26%), Mesogasteropoda (9.01%) and Decapoda (9%) are the most abundant orders. Another oders constitute only a small fraction of the total fauna harvested. The redundancy analysis performed shows that abiotic parameters that strongly influence taxonomic diversity and taxon abundance are: current velocity, nitrogen and phosphorus compounds, mineralization parameters and canopy

Air pollution and development in Africa: impacts on health, the economy, and human capital

Background Africa is undergoing both an environmental and an epidemiological transition. Household air pollution is the predominant form of air pollution, but it is declining, whereas ambient air pollution is increasing. We aimed to quantify how air pollution is affecting health, human capital, and the economy across Africa, with a particular focus on Ethiopia, Ghana, and Rwanda. Methods Data on household and ambient air pollution were from WHO Global Health Observatory, and data on morbidity and mortality were from the 2019 Global Burden of Disease Study. We estimated economic output lost due to air pollution-related disease by country, with use of labour income per worker, adjusted by the probability that a person (of a given age) was working. Losses were expressed in 2019 international dollars and as a proportion of gross domestic product (GDP). We also quantified the contribution of particulate matter (PM)2·5 pollution to intelligence quotient (IQ) loss in children younger than 10 years, with use of an exposure–response coefficient based on previously published data. Findings Air pollution was responsible for 1·1 million deaths across Africa in 2019. Household air pollution accounted for 697 000 deaths and ambient air pollution for 394 000. Ambient air pollution-related deaths increased from 361 000 in 2015, to 383 000 in 2019, with the greatest increases in the most highly developed countries. The majority of deaths due to ambient air pollution are caused by non-communicable diseases. The loss in economic output in 2019 due to air pollution-related morbidity and mortality was $3·02 billion in Ethiopia (1·16$1·63 billion in Ghana (0·95% of GDP), and $349 million in Rwanda (1·19% of GDP). PM2·5 pollution was estimated to be responsible for 1·96 billion lost IQ points in African children in 2019. Interpretation Ambient air pollution is increasing across Africa. In the absence of deliberate intervention, it will increase morbidity and mortality, diminish economic productivity, impair human capital formation, and undercut development. Because most African countries are still early in development, they have opportunities to transition rapidly to wind and solar energy, avoiding a reliance on fossil fuel-based economies and minimising pollution. Funding UN Environment Programme

Checklist of the fresh and brackish water snails (Mollusca, Gastropoda) of Bénin and adjacent West African ecoregions

Currently no comprehensive checklist of fresh and brackish water gastropods from Bénin exists, and those for adjacent West African areas are outdated. Yet, such checklists provide essential biodiversity information and a consistent taxonomic and nomenclatural framework for that biodiversity. Here a first checklist of the fresh and brackish water gastropods from Bénin and adjacent West African ecoregions is presented, based on an extensive literature review and field surveys between September 2014 and June 2019 in six major fresh and brackish water ecosystems in Bénin. This inventory includes information on synonymy, species distribution in West Africa, habitats, and conservation status. The fresh and brackish water gastropod fauna includes 60 species, belonging to 28 genera and 16 families. Pachychilidae, Ampullariidae, Neritidae, and Bulinidae were the most diverse families with 9, 8, 7, and 7 species, respectively. However, literature and field data indicated that 23 species observed in West African basins that extend to Bénin do not occur in the territory of Bénin. These species were not detected in our field surveys, most likely because they are rare at collecting sites. Of the 60 species included, five are classified as “Data Deficient”, 43 as “Least Concern”, two as “Nearly Threatened”, one as “Vulnerable”, and six as “Endangered” by the IUCN, whereas the remaining three species were not evaluated. Because the taxonomy of fresh and brackish water gastropods in West Africa is still largely based on morphology, comparative molecular and taxonomic studies may result in substantial revisions of this checklist over the coming years

Caractérisation physico-chimique d’un système lotique en région tropicale : la rivière Sô au Sud- Bénin, Afrique de l’Ouest.

Objectif : Faire une caractérisation physico-chimique des eaux de la rivière Sô en vue d’offrir des éléments de base pour une modélisation écologique future du système.Méthodologie et Résultats : Les données ont été collectées mensuellement pendant 18mois, de Juin 2015 à Novembre 2016 au niveau de douze stations d’échantillonnage. Seize paramètres physico-chimiques dont huit in-situ (température, pH, transparence, profondeur, salinité, oxygène dissous, conductivité électrique et Solides Totaux Dissous) et huit au laboratoire (NTK, NO2-, NO3-, NH4+, PO43- ortho, PO43-total, Ca2+ et Mg2+) ont été mesurés. Le test de Kruskal Wallis et de SNK, la matrice de corrélation, la Classification Hiérarchique Ascendante (ACH) et l’Analyse en Composantes Principales (ACP) ont été appliqués à l’ensemble des paramètres mesurés. Les résultats ont permis d’identifier quatre groupes de stations avec 80% de dissemblance. Le groupe 1 constitué des stations du cours inférieur, présente des eaux fortement minéralisées, les groupes 2 et 3 constitués des stations du cours moyen, témoignent d’une pollution azotée et phosphorée et le groupe 4 constitué des stations du cours supérieur de la rivière présente les caractéristiques des eaux très bien oxygénées et favorable à l’accroissement des espèces aquacoles.Conclusions et applications : la partie amont de la rivière Sô présente des eaux d’une bonne productivité piscicole tandis que les cours aval et moyen présentent des eaux de fortes teneurs en composés azotés et phosphorés perturbant le biotope ce qui pourrait crée un déséquilibre de la faune aquatique. Ces résultats constituent des données de base pour la mise en place d’un plan de gestion durable de la rivière et son bassin versant.Mots-clés : Physico-chimie, Pollution, Système lotique, Rivière Sô, Région tropicale

Using self–organizing maps and machine learning models to assess mollusc community structure in relation to physicochemical variables in a West Africa river–estuary system

International audienceThe poor understanding of changes in mollusc ecology along rivers, especially in West Africa, hampers the implementation of management measures. We used a self–organizing map, indicator species analysis, linear discriminant analysis and a random forest model to distinguish mollusc assemblages, to determine the ecological preferences of individual mollusc species and to associate major physicochemical variables with mollusc assemblages and occurrences in the Sô River Basin, Benin. We identified four mollusc assemblages along an upstream–downstream gradient. Dissolved oxygen (DO), biochemical oxygen demand (BOD), salinity, calcium (Ca), total nitrogen (TN), copper (Cu), lead (Pb), nickel (Ni), cadmium (Cd) and mercury (Hg) were the major physicochemical variables responsible for structuring these mollusc assemblages. However, the physicochemical factors responsible for shaping the distribution of individual species varied per species. Upstream sites (assemblage I) showed high DO and low BOD and mineral compounds (i.e., TN, salinity, and Ca), which are primarily responsible for structuring the occurrences of bivalves (Afropisidium pirothi, Etheria elliptica, Sphaerium hartmanni) and the gastropod Lanistes varicus. Sites along the middle reach (assemblage II) were characterised by a high degree of organic pollution but low heavy metal pollution; we detected no specific mollusc indicator species. Downstream sites (assemblage III) displayed high mineral and heavy metal concentrations and a fauna without specific indicator species. Finally, downstream sites associated with brackish water (assemblage IV) displayed important levels of organic and heavy metal pollution. These sites are dominated by diverse gastropods (i.e., Bulinus spp., Gabbiella africana, Indoplanorbis exustus, Pachymelania fusca, Radix natalensis, Stenophysa marmorata and Tympanotonos fuscatus). Our results highlight that mollusc communities in the Sô River Basin are structured by key physicochemical variables related to the river–estuary continuum. Habitats that are progressively more downstream are confronted with increasing anthropogenic stress. Conservation and management plans should focus on downstream habitats