PhD Dissertation Defense: Justin Ridge

The Ph.D. Dissertation Defense of Justin Ridge will be presented at IMS (Institute of Marine Science) seminar room 222 in Morehead City, NC and live broadcast to Murray Hall, room 3204 of the UNC at Chapel Hill Marine Sciences Department. Held on Wednesday, February 17th, 2017 at 2:00 PM.

Title: The influence of sea level on the growth and composition of oyster reefs

Abstract: Oyster reefs play an important role in the estuarine landscape but have been globally decimated over the past century from overharvesting, deteriorating water quality, and disease.  Expanding our knowledge of how these habitats are responding to anthropogenic and climate driven changes will help improve management strategies.  My work seeks to build on prior research that has shown growth of intertidal oyster reefs is strongly linked to specific elevation ranges within the intertidal zone.  Using high resolution mapping (terrestrial lidar) and cores of reefs, I have found that oyster reefs are in a dynamic equilibrium with sea level, responding rapidly (< 1 year) to changes in water level.  Examining oyster reefs across time scales, from ancient reefs (~4,000-2,000 years old) to extant natural reefs (150 years old) and recently constructed reefs (5-10 years old), there is evidence that oyster reefs exhibit the catch-up and keep-up growth phases tied to sea-level rise found in coral reefs.  Within this context, reefs experience exceptional rates of shell production and organic carbon accumulation while catching up to sea level, but these values are at least a magnitude less in reefs that are keeping up with sea level.  Burial of ancient reefs is likely a result of estuarine changes related to the migration of adjacent barrier islands, indicating oyster reefs existing near the limits of suitable conditions could be fatally impaired by estuarine modifications, either anthropogenic (inlet and river dynamics) or climate driven (storms).