Hulot, F. D.; Hanot, C.; Nelieu, S.; Lamy, I.; Karolak, S.; Delarue, G.; Baudry, E.

Contamination is one of the major threats to freshwater biodiversity. Compared to other aquatic ecosystems, peri-urban ponds are unique because they are embedded in human-dominated areas. However, it is poorly understood how different land uses such as urban or agricultural contribute multiple pollutants to ponds and thus affect pond biodiversity. In this work, 12 ponds located in a peri-urban area (Ile-de-France region, France) were monitored for 2 consecutive years in spring and fall. We surveyed macroinvertebrates and measured the physicochemical parameters and contaminants of different classes (trace elements, pharmaceuticals, pesticides and polycyclic aromatic hydrocarbons) in both water and sediment. The objective was twofold: to explore local and regional macroinvertebrate spatiotemporal diversity and to understand the effects of contaminants on abundance and community structure. We observed 247 macroinvertebrate morphotaxa, none of which were rare or sensitive to pollutants. Local alpha diversity (within ponds) showed small differences between ponds and higher variability between years and seasons for species richness and Shannon diversity. We did not observe a relationship between land use around the pond (agricultural, urban, or semi-natural) and its alpha diversity. Regional beta diversity (between ponds) showed that differences in species composition reflected species replacement more than differences in species richness; these were primarily due to the high abundance of pollutant-tolerant species in some of the ponds. The effects of environmental parameters on community structure were studied using partial redundancy analysis based on the presence-absence of morphotaxa, showing that community assemblages are shaped by sediment levels of pharmaceuticals and trace metals, as well as chemical oxygen demand, conductivity and total nitrogen concentration in water. In conclusion, ponds in peri-urban areas are exposed to various human activities, with our results suggesting that this exposure leads to chronic and diverse contaminations that affect species communities.