Transparency (>0.9 m) . According to the System for the Evaluation of Coastal Water Quality, these thresholds correspond to "good to medium" suitability classes, except for total phosphorus. One of the original features of this study is the use of the bounds of the credibility interval of the fixed-effect coefficients as local weathering standards for the characterization of the physico-chemical status of this anthropized African ecosystem.

In view of the very strong degradation of aquatic ecosystems, it is urgent to set up monitoring systems that are best able to report on the effects of the stresses they undergo. This is particularly true in developing countries, where specific and relevant quality standards and funding for monitoring programs are lacking. The objective of this study was to make a relevant and objective choice of physico-chemical parameters informative of the main stressors occurring on African lakes and to identify their alteration thresholds. Based on statistical analyses of the relationship between several driving forces and the physico-chemical parameters of the Nokoué lagoon, relevant physico-chemical parameters were selected for its monitoring. An innovative method based on Bayesian statistical modeling was used. Eleven physico-chemical parameters were selected for their response to at least one stressor and their threshold quality standards also established: Total Phosphorus (<4.5mg/L) , Orthophosphates (<0.2mg/L), Nitrates (<0.5 mg/L), TKN (<1.85 mg/L), Dry Organic Matter (<5 mg/L) , Dissolved Oxygen (>4 mg/L), BOD (<11.6 mg/L) , Salinity (7.6 ‰) , Water Temperature (<28.7 °C) , pH (>6.2) , and Transparency (>0.9 m) . According to the System for the Evaluation of Coastal Water Quality, these thresholds correspond to "good to medium" suitability classes, except for total phosphorus. One of the original features of this study is the use of the bounds of the credibility interval of the fixed-effect coefficients as local weathering standards for the characterization of the physico-chemical status of this anthropized African ecosystem.

The present study focused on using benthic macrofauna to assess the risks of moving away from Good Ecological Status towards the functioning of an anthropized system (Nokoué-Benin), based on de ning reference values for macroinvertebrate metrics, stress thresholds and the responses of selected metrics to stressors. The approach used is a combination of a joint species distribution model and Bayesian networks. We used JSDM to select relevant metrics and generate posterior probabilities. We then converted these posterior probabilities into posterior response probabilities for each of the stress levels and fed them into a Bayesian network. To de ne the reference values of the metrics and the stress thresholds derived from the probability density diagrams for low-pressure levels, we used the responses predicted by the Bayesian network. An application of this approach was then carried out on a lagoon sampled during high and low water periods for three consecutive years (2004)(2005)(2006), with 33 macroinvertebrate taxa present in all seasons and sampling points, and measurements of 14 environmental parameters used as application data. This study demonstrated a reliable inference, the selection of seven relevant metrics and the de nition of reference conditions. The relevance of the metrics and ecological assessment criteria, despite the small sample size, suggests the potential for wider applicability of the approach to aquatic ecosystem monitoring and assessment programs in developing countries, which are generally characterized by a lack of monitoring data.