Fig. 1

Oxygen permeability, effect of egg abundance on pH, and effect of pH on viability of eggs. a Oxygen permeability in experimental containers. Data points are means of 5–20 replicates and error bars are standard deviations. Oxygen levels in glass containers remain low and stable over several days whereas the Oxygen concentration in polypropylene containers increases, reaching near saturation after less than 5 days. Lines represent Oxygen saturation (10.4 mg O₂ L⁻¹), hypoxia (4 mg O₂ L⁻¹), and severe hypoxia (2 mg O₂ L⁻¹). b Samples with increasing egg abundance have decreasing pH. Data points are individual samples. Eggs were counted at the start of the experiment. In Exp. 2, where eggs were arrested for 50 days in abundances of 300–120,000 mL⁻¹, each increase in egg abundance resulted in a drop in pH. Thus, the samples with lowest egg abundance have a pH of 7.5 while the samples with highest egg abundance have a pH of ≤ 6. The initial pH of 8 in control samples did not change during the duration of the experiment (data not shown). c The survival rate of eggs is stable over a wide range of pH. Ten samples from Exp. 2 were hatched in triplicate and the emerging nauplii counted. Error bars are s.d. For samples with pH 6.0–7.5, the survival is stable and between 78 and 90% ZTM. The survival rate of eggs in samples with sediment realistic acidity levels suggests that the acidity of the environment is not of great importance to egg survival. At the lowest pH in the experiment, the survival rate is 55%