Water quality and health status of the Senegal River estuary M. Troussellier a, * , P. Got a , M. Bouvy b , M. M 0 Boup b , R. Arfi b , F. Lebihan b , P. Monfort a , D. Corbin b , C. Bernard c a Laboratoire Ecosyst emes lagunaires, UMR 5119 CNRS, Universit e Montpellier II, Case 093, Place E. Bataillon, 34095 Montpellier Cedex 5, France b Institut de Recherche pour le D eveloppement (IRD), IRD Center Bel Air, BP 1386, Dakar, Senegal c USM505 Ecosyst emes et interactions toxiques, Mus eum National d’Histoire Naturelle, 12 Rue Buffon, 75231 Paris Cedex 05, France Abstract The Senegal River estuary was sampled in May 2002 to get the first data on both the trophic and sanitary status of the water of the main river of the northwest African coast. Several physical, chemical and microbiological variables were measured twice along a transect. Inorganic nutrient concentrations were low while phytoplanktonic abundances (0.58–1.8 · 10 5 cells ml 1 ), bacterial abundances (0.27–8.1 · 10 7 cells ml 1 ), activity (22–474 pmol l 1 h 1 ), were among the highest recorded in such ecosystems. Microbiological variables revealed a eutrophicated status for this estuary. Largest abundances of fecal contamination bacterial indicators were only detected in localized areas (Saint-Louis city and surrounding areas). The apparent good survival of fecal indicator bacteria in the estuarine waters despite a long residence time (4–5 days) has been evaluated by complementary survival experiments. Exposed to a salinity gradient, a local Escherichia coli strain showed a significantly better survival than those of an E. coli reference strain. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Bacteria; Phytoplankton; Fecal contamination indicators; Eutrophication; Senegal River estuary 1. Introduction Coastal rivers often receive large urban sewage in- puts, due to the large density of inhabitants in coastal areas (Scialabba, 1998). As a consequence, these rivers can bring large amounts of nutrients and pollutants in receiving marine coastal areas. Nutrient enrichment leads to the eutrophication of a large number of coastal zones (e.g. Cloern, 2001) with a concomitant increase in harmful algal bloom frequency. Sewages, among others impacts, appeared to have a massive effect on human population health through microbiological contamina- tion of coastal waters and shellfishes as reported in re- cent studies (GESAMP, 2001). Coastal areas often provide very important recrea- tional and economic resources (Costanza et al., 1997), and therefore the trophic status of coastal waters, the safety of beach or shellfish and fish farming waters are of concern for many countries. The ‘‘health’’ status of African rivers and estuaries has been poorly studied, while they are the place of large demographic development and receive increasing vol- ume of waste, particularly sewage without significant treatment. On the other hand, African coastal areas support fisheries, which are essential protein resources for many African countries (e.g. Jouffre, 1998; Caveri- vi  ere et al., 2002; SIAP, 2002). The only large river of the northwest coast of Africa is the Senegal River. The Senegal River watershed covers near 335,000 km 2 and spreads over four countries (Guinea, Mali, Mauritania, Senegal). The number of inhabitants on the Senegal River basin is around 3,500,000. The hydrology of this river system has changed since the constructions of two dams (Diama in Senegal and Manantali in Mali). The Diama dam, lo- cated 27 km upstream of Saint-Louis city in Senegal, was designed to prevent the intrusion of saline water from the Atlantic Ocean. The objectives of this dam were to expand irrigated farming along the Senegal River and the Delta, and to store surface water in res- ervoirs which are used for drinking water and cattle. Population, especially around the city of Saint-Louis * Corresponding author. Fax: +33-04-67-14-37-19. E-mail address: troussel@univ-montp2.fr (M. Troussellier). 0025-326X/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2003.10.028 www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 48 (2004) 852–862