Tolerance of low dissolved oxygen and hydrogen sulfide by the polychaete Streblospio benedicti (Webster)

The spionid poluchaete Streblospio benedicti (Webster) is common in surface sediments of estuarine intertidal and subtidal habitats. Because of their broad distribution, S. benedicti populations are often exposed to hypoxia or anoxia during summer in estuaries with periodic deoxygenation. The opportunistic behavior of S. benedicti after disturbance (e.g., hypoxia or anoxia) has been recognized; however, its tolerance of low dissolved O2 has not been studied. In the present study, tolerance and behavior to hypoxia, anoxia and hydrogen sulfide of adult S. benedicti were determined in laboratory experiments. Under severe hypoxia, adults survived for at least 2 wk without significant mortality at two experimental dissolved O2 concentrations (14.5 and 7% air saturation at 26°C). In anoxia, all worms died within 55 h. The behavior of S. benedicti was modified; feeding ceased and burrowing activities were reduced in hypoxia and anoxia. Most worms came out to the sediment surface at time of death. Survival of worms exposed to anoxia and moderate concentrations of hydrogen sulfide (< 66 μM) was not decreased in comparison to reference individuals in anoxia alone. Results from this study suggest that field populations of S. benedicti may survive intermittent periods of hypoxia, but that the intensity and duration of low dissolved O2 events may be critical to survivorship and local population persistance.