Large‐Scale Flow Management Action Drives Estuarine Ecological Response

Resource managers rely on large-scale flow and habitat enhancement actions to support sensitive species in the San Francisco Bay–Delta. The effects of these target ecosystems are largely unknown. In 2018, we implemented an ecosystem-scale experiment reduce salinity improve access high-quality Suisun Marsh, California, for Endangered Species Act-listed Delta Smelt Hypomesus transpacificus. action included a release approximately 46 million m3 additional conjunction with operation novel water management facility, Marsh Salinity Control Gates. This experimental resulted more low-salinity than would have been present as compared similar historical low-flow summer conditions. We evaluated effect decreasing assemblage using combination ordination analyses circular statistics. focused this analysis long-term monitoring data collected within during July August found that aquatic community changed significantly small sloughs but not large-slough response action. shift from 2018 differed trends both slough sizes, albeit habitat. Specifically, observed (1) California bay shrimp Crangon franciscorum Striped Bass Morone saxatilis abundance like occurring low-salinity, wet year types; (2) uncharacteristic seasonal decline Black Sea jellyfish Maeotias marginata. posit changes were driven by behavioral responses lower-salinity conditions physical displacement directional resulting