Estuary Pearls is a collection of short articles on science activities in the Delta and is published by the San Francisco Estuary Partnership. In this edition: A new system for treating agricultural drainage water in the Delta could also help rebuild subsided islands. Manmade features in the Delta, including riprap-armored banks, water diversion pipes, pilings, and woody debris, may be sending juvenile native fishes into the jaws of finned invaders. Levels of pyrethroid insecticides spike sharply in the North Delta’s Cache Slough during winter rainstorms, rendering the water so toxic that it decimates laboratory populations of a half-inch crustacean called Hyalella azteca. Researchers hope new computer models will help clarify the effects of entrainment on the population of endangered Delta smelt. While the acreage of wetland restoration projects is growing throughout the Delta, scientists are still working to understand how best to help these areas become fully functioning, complex habitat as quickly and successfully as possible. An emergency barrier installed to protect the state’s water supply from saltwater intrusion during the recent record-setting drought had little effect on the ecosystem. A recent test found more than 250 chemicals in the Delta’s Cache Slough, but “Dr Doom” says figuring out what they all are, and their concentrations, is beside the point in our efforts to understand stressors on native fish resilience. View all articles by clicking here.