SALINITY TOLERANCE OF THE COPEPOD APOCYCLOPS-DENGIZICUS (LEPESCHKIN, 1900), A KEY FOOD-CHAIN ORGANISM IN THE SALTON-SEA, CALIFORNIA

The copepod Apocyclops dengizicus is a key item in the food chain of the Salton Sea where the salinity is currently 45 g l-1. The salinity of the Salton Sea may reach 90 g l-1 within the next 20 years. This study examined the salinity tolerance of this copepod. Large copepodite and adult A. dengizicus were introduced into various salinities with and without acclimation. The 96 h LC50 without acclimation was 101 g l-1. Mortality (at 96 h) without acclimation was low at salinities of 90 g l-1 or less. Copepod cultures were maintained, with successful reproduction of at least one new generation, at salinities of from 0.5 to 68 g l-1 for at least 120 days. Copepods maintained at higher salinities, up to 79 g l-1, remained alive up to 90 days, but a new generation was not produced. In laboratory studies of larval production and survivorship, few nauplii were released at salinities of 68 g l-1 or higher, and none survived to the copepodite stage.