Seasonal Variations In Stream Salinity In Eastern Nebraska's Salt Creek Watershed – Implications for the Survival of the Endangered Salt Creek Tiger Beetle

Eastern Nebraska's saline wetlands are bisected by three named streams which are home to the endangered Salt Creek Tiger Beetle (Cicindela nevadica lincolniana). Adult beetles use the saline stream banks and sand bars for mating and oviposition having a preference for higher ranges of soil moisture and salinity. Recently, beetle populations have dwindled into the hundreds and thus, to increase their numbers in the wild, wetland managers plan to reintroduce beetles to target locations along the creeks. However, to achieve success, managers need information on seasonal and storm event variations in stream salinity. To assist reintroduction efforts, a study was initiated in 2007 to monitor variations in stream water quality within Little Salt, Rock and Salt Creeks. Thirteen sampling locations were selected - six along Little Salt Creek, four on Salt Creek, and three on Rock Creek. At each location salinity and temperature measurements were made weekly using a YSI 30M probe. Results indicate that stream salinities are generally highest in Little Salt Creek, followed by Salt Creek and Rock Creek. It should be noted that the only present-day Salt Creek Tiger Beetle populations are found along Little Salt Creek. Salinity increases downstream in all three streams, and several zones of higher salinity were located along each stream course. Stream salinity decreases dramatically in response to precipitation events, and appears to reach a maximum during baseflow periods. As the specific moisture and salinity needs of the Salt Creek Tiger Beetle are still being investigated by entomologists, it is not yet clear how variations in stream salinity impact beetle behavior. The data do suggest however that if beetles are found to have a low tolerance for the measured variations, it may be necessary for managers to take steps to regulate stream salinity if the beetles are to survive.