The Performance of a Fully Automated System for Testing the Combined Effects of Acidification and Hypoxia on Fish Early Life Stages

Many coastal marine fish experience covarying pH and dissolved oxygen (DO) conditions within their natural habitats, which potentially modulates their vulnerability to the growing threat of coastal acidification and eutrophication. To better understand the combined effects of low pH and DO on potentially susceptible early fish life stages, we designed and built a computer-controlled experimental system that allows rearing fish offspring under static and fluctuating pH and DO levels. The nine independent units each housing up to six replicate rearing containers (20L) permit full factorial 3 × 3 experimental designs (e.g., 3 pH x 3 DO levels) for advanced multistressor approaches and quantification of interactions. Fluctuating levels in rearing chambers can mimic the tidal and diel variability under current and future climate scenarios, given the likelihood that the frequency and duration of extreme low pH and DO may increase. We provide a full performance assessment of our rearing system and report on initial findings from preliminary experiments using Atlantic silverside offspring, an ecologically important forage fish and uniquely suited model species.