Lethal and sublethal effects of sediment burial on the eastern oyster Crassostrea virginica

Abstract

Eastern oysters Crassostrea virginica are dominant ecosystem engineers that construct complex reefs in estuarine systems. Reef persistence relies on reef growth, which must outpace reef degradation and sediment deposition. The quantitative impact of burial on oyster survival and sublethal effects of sediment deposition are undefined. In this mesocosm study, we quantified effects of partial and complete burial (0, 50, 70, 90, and 110% of oyster shell height) on survival, biodeposition, condition index and growth of oysters (shell height = 25−75 mm). Survival only declined significantly when 90% or more of an oyster was buried; the critical burial depth inducing 50% mortality was 108%. This finding will allow scaling of mortality rates of oysters as a function of sediment load and oyster size. Biodeposition and condition index were negatively related to burial depth, whereas shell growth increased with burial depth. Decreases in biodeposition and condition index were likely related to disruption of feeding by burial and reallocation of energy resources to shell growth. The increase in shell growth was analogous to vertical migration of infaunal species -buried oysters increased vertical shell growth to breach the sediment surface to feed and respire, at the expense of tissue growth. While oysters are tolerant of partial burial in terms of survival, burial adversely affects metabolic processes that influence demographic rates and reef persistence. Future management efforts should consider the effects of partial burial, which often occur more frequently than catastrophic burial events causing mass mortality.

Quantitative Validation of a Habitat Suitability Index for Oyster Restoration

“…For low-relief reefs, reef persistence depends greatly on whether live oyster shell accretion outpaces subsidence and sedimentation (Schulte et al, 2009;Jordan-Cooley et al, 2011;Colden and Lipcius, 2015;Lipcius et al, 2015). In several cases, low-relief reefs in the GWR with HSI ≥ 0.3 exhibited low live adult oyster densities.…”

Reef height drives threshold dynamics of restored oyster reefs

“…Sedimentation impacts oyster populations directly through burial that smothers oysters, causing mass mortality (Norris 1953, Dunnington 1968, Miller et al 2002, Twichell et al 2010, and indirectly through partial burial that degrades habitat quality and reefbuilding processes (Colden & Lipcius 2015). At the study site with the highest sediment deposition rates (LR2), indications of heavy sedimentation were evident 2 mo following construction, and full burial of reefs occurred between 8 and 24 mo post-construction.…”

Validation of a habitat suitability index for oyster restoration

“…Our division of the analysis of live adult oyster densities and corresponding HSI values into low‐ and high-relief reef categories was necessary as some of the low-relief reefs constructed in the GWR had degraded due to sedimentation and subsidence into mud seabottom. For low-relief reefs, reef persistence depends greatly on whether live oyster shell accretion outpaces subsidence and sedimentation (Schulte et al 2009, Jordan-Cooley et al 2011, Colden and Lipcius 2015, Lipcius et al 2015). In several cases, low-relief reefs in the GWR with HSI values ≥0.3 exhibited low live adult oyster densities.…”