Impact of hypoxia on the survival, egg production and population dynamics of Acartia tonsa Dana

Concern for the increasing occurrence of coastal zone hypoxia has generally focused on the direct, short-term impact of reduced dissolved oxygen (DO) concentrations on the survival of commercially important species such as fish and crabs. Copepods, especially the naupliar stages, are important pelagic food web components, yet only a few studies have considered the effect of reduced DO concentrations on their survival and population dynamics. This study considers the impact of both lethal and sublethal DO concentrations on copepods. Acartia tonsa were reared at 25°C at saturating DO (normoxic control) and reduced (hypoxic) DO concentrations of 1.5 or 0.7 ml l^-1. Oxygen concentrations were maintained in replicate flasks, by bubbling seawater with air (control), or mixtures of nitrogen and oxygen. Egg production, but not survival, was significantly higher in the controls compared to the 1.5 ml l ^-1 DO treatment. Survival and egg production were significantly lower at 0.7 ml l^-1 DO compared to the control. The results suggest that the sublethal as well as the lethal effects of hypoxia may have important repercussions on population and community dynamics in coastal systems.