Number of zooplankton taxa and total abundance of zooplankton sampled from the Chicago River before and after a large CSO event from three locations sampled in 2023. Three locations were sampled, with the disturbed location receiving 9.1 billion liters over two weeks. Sharing letters indicate similarities among locations within each period (‘a/b’ before CSO, ‘x/y’ after CSO), while asterisks denote significant changes within locations before and after the event.