Sodium sulfite can reliably induce chemical hypoxia without toxic effects in the model sea anemone species, Exaiptasia diaphana

Zhen Qin, Lorenzo Vassura, Bianca Allegra Parodi, Elise Laetz

Climate change is accelerating the deoxygenation of aquatic ecosystems, making understanding its effects on biological processes critical. An emerging method for inducing hypoxia during experimentation utilizes sodium sulfite to scavenge oxygen, however it remains unclear if hypoxia-inducing concentrations of sodium sulfite are toxic to aquatic species. We decoupled sodium sulfite’s potential toxicity from its hypoxia-inducing effects by rapidly replacing the oxygen it removes via vigorous aeration. We examined the model species Exaiptasia diaphana (a sea anemone) and its endosymbiotic dinoflagellates by exposing them to a dosage that mimics the diel oxygen cycle for two weeks. We examined common stress indicators including, the anemone’s metabolic rates and thermal tolerance, the algae’s photosynthetic efficiency, cell density and reproduction in treated and untreated specimens, finding no effects of sodium sulfite exposure. A second trial assessed acute toxicity, finding that anemones lacked observable stress responses after 70x the concentration needed to induce anoxia (8.669 g/L). We therefore conclude that sodium sulfite is a viable, cost-effective and non-toxic way to induce hypoxia in laboratory settings.