, Volume 556, Issue 1, pp 85-98

Responses of Estuarine Benthic Invertebrates to Sediment Burial: The Importance of Mobility and Adaptation

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Abstract

Estuarine benthic organisms are frequently subjected to disturbance events caused by hydrodynamic processes that disrupt and move the sediment in which the animals reside, however the mechanisms by which physical disturbance processes affect infaunal and epifaunal populations and communities remain poorly resolved. The responses of three infaunal and two epifaunal estuarine benthic species to sediment disturbance (burial) were compared in laboratory experiments. Overburden stress (kPa) was calculated to quantify the force exerted on organisms by sediment burial for 6 d. At the levels tested (0–16 kPa), increasing overburden stress did not significantly decrease survival or growth of juvenile burrowing bivalves, Macoma balthica (Linnaeus). Survival of juveniles and adults of the tubiculous polychaete Streblospio benedicti (Webster) and neonates of the burrow-forming amphipod Leptocheirus plumulosus (Shoemaker) declined exponentially with increasing overburden stress. The mean S. benedicti survival rate was 4% of the control at an overburden stress of ≈4 kPa, while an overburden stress of 12 kPa was necessary to comparably reduce survival of L. plumulosus. At the low levels of overburden stress used in the experiments with epifauna (≤0.2 kPa), juvenile oyster Crassostrea virginica (Gmelin) did not suffer significant mortality at an overburden stress of 0.1 kPa. In contrast, the epifaunal tunicate Molgula manhattensis (DeKay) exhibited significant mortality when partially (one or two siphons exposed) or completely buried under sediment with an overburden stress of 0.2 kPa. Species-specific response to burial varied as a function of motility, living position, and inferred physiological tolerance of anoxic conditions while buried. We conclude that some benthic species exhibit mechanical and possibly physiological adaptations that may allow them to survive deposition events of the magnitude commonly encountered in estuarine environments.