Let the oyster reefs tell their story- a novel approach to reconstructing coastal environmental histories

Intertidal oyster reefs (Crassostrea virginica) are a vital part of coastal ecosystems around the world, providing habitat for marine life and improving water quality. These integral parts of coastal landscapes also dissipate wave energy, reducing estuarine shoreline erosion. Within the last century, oyster reefs across the world have decreased in abundance and areal extent due to anthropogenic and environmental changes, such as harvesting, pollution, climate change and disease. However, previous studies of restored oyster reefs—based on direct measurements of oyster-reef growth over a decade—have shown the ability of intertidal reefs to outpace sea-level rise via vertical accretion.

In this study we present a novel application of ²¹⁰Pb geochronology (Constant Rate of Supply Model) combined with radiocarbon dating applied to two natural intertidal oyster reefs in North Carolina, USA. Our findings show that within the last 560 years, the oyster reef located on an open mudflat consistently grew at the rate of sea-level rise (SLR). The second examined reef was located in a sandy tidal channel and initially formed around 700 years ago. Reef sediments recorded a disturbance associated with a large storm event, Hurricane Barbara (1953).

Our new application of the ²¹⁰Pb geochronology method, combined with radiocarbon dating, analyses of shell condition and size, and grain size, opens the possibilities to explore the historical record of oyster-reef health and growth rate to evaluate its sensitivity or resilience to sea-level rise, sediment supply, storms and anthropogenic disturbances. Identifying periods and conditions of optimal growth for oyster-reef habitats will provide vital information for restoration efforts. Additionally, oyster reefs may contain a detailed and well-preserved record of local sea level in their sediments.