Greening the Grey: Integrating Oysters to Enhance Grey Infrastructure Effectiveness Against Sea Level Rise

As the global climate changes and ocean warming continues to accelerate, sea-level rise (SLR) is becoming a growing threat to coastal communities. Talbot and Dorchester County, Maryland (Chesapeake Bay) are experiencing some of the highest rates of SLR in the country. Historically, communities have used grey engineering such as breakwaters, seawalls or rip-rap, to protect their shorelines from erosion and storms. However, over time and without major upgrades, these will lose effectiveness due to natural degradation but also from inundation by SLR. Furthermore, these structures provide poor habitat for aquatic species and degrade the ecology of the surrounding environment. This project seeks to create hybrid coastal infrastructure by retrofitting grey infrastructure with oysters using oyster castles. Oysters are ecosystem engineers, offering both protective and non-protective benefits to coastal communities. Oyster castles are the most promising deployment method for creating hybrid infrastructure as they are able to withstand the physical disturbances of high energy environments, whereas other deployment methods (e.g. bagged spat-on-shell) cannot. This study focused on filling knowledge gaps about the effectiveness of oyster castles to stabilize shorelines and promote ecological function through a long-term BACI-designed ecosystem project. We constructed model-informed oyster castle breakwaters at Horn Point Laboratory with the aim of comparing both the protective and non-protective benefits of seeded and unseeded breakwaters by monitoring wave-dampening effects, shoreline response, biodiversity and oyster growth and reef accretion. Focusing mainly on the ‘before’ part of the BACI design, we took the first steps necessary in understanding the use of oyster castles in Maryland. The products of this research will allow us to more accurately understand the eco-value and benefits of retrofitting grey infrastructure with oysters, protecting coastal communities and habitats against sea-level rise.