Demographic responses of an extremophile crustacean to environmental factors: Great Salt Lake (Utah, USA) brine shrimp (Artemia franciscana)

Abstract

Hypersaline Great Salt Lake’s (GSL: Utah, USA) pelagic food web is dominated by the herbivore, Artemia franciscana. Artemia demographic responses (survival, developmental transition, and reproduction) to GSL salinities, temperatures, common phytoplankton and yeast, and food levels were examined by factorial experiment. Survival across developmental stages was best at 90 ppt salinity, and decreased as temperature increased. Transition between life stages was best at 45 ppt salinity, and increased as temperature increased. Food was most important with both survival and transitioning responding similarly to food types and increasing with amount of food. Artemia reproduce in two ways (diapausing cysts – oviparity, live young – ovoviviparity): ovoviviparous and total reproduction were greatest at 90 ppt salinity and 20 °C, while oviparous reproduction was weakly affected by salinity and greatest at 20 °C. Oviparity was greatest at low food availability, while ovoviviparity and total reproduction increased with food availability, so reproduction shifted from oviparity to ovoviviparity as food increased. Maternal effects were observed for cyst hatchability, and ovoviviparous nauplii survival and transitioning to the juvenile stage. Combinations of salinity, temperature, food taxa and food amount strongly affect demography, making single factor studies of limited value. Results explain Artemia abundance in different parts of GSL and among years.