Aquatic invertebrate resting egg sensitivity to glutaraldehyde and sodium hypochlorite

Ballast tank treatment technologies are currently in development to reduce the risk of acquiring or transporting viable aquatic organisms that could be introduced to ecosystems and become invasive. Aquatic invertebrate resting eggs represent a challenge to such technologies because of morphological and biochemical adaptations to stress that also protect eggs from artificial stressors. To evaluate the potential efficacy of chemical biocides for ballast tank treatment, the present study examined the acute toxicity of glutaraldehyde and sodium hypochlorite on resting eggs of the freshwater cladoceran Daphnia mendotae and marine brine shrimp (Artemia sp.). Glutaraldehyde was toxic to resting eggs of Artemia sp., as indicated by a lethal concentration to 90% of organisms (LC90) of 95% confidence interval (226 +/- 10 mg/L). Daphnia mendotae, in contrast, displayed erratic responses to glutaraldehyde. Sodium hypochlorite was similarly toxic to resting eggs of Artemia sp. and D. mendotae, which displayed LC90s of 86.5 +/- 3.0 and 78.3 +/- 1.6 mg/L, respectively. Burial in sediment protected resting eggs from toxicants. The present results corroborate those from previous investigations of resting egg sensitivity to artificial stressors, supporting the conclusions that resting eggs are less sensitive than other life stages to artificial stressors and that chemical biocide concentrations effective against other life stages may be ineffective against resting stages.