Monitoring the Fate of Artificial Reefs: Using Hydrographic Methods to Examine Degradation and Movement

Artificial reefs are used around the world for a variety of purposes, yet few long-term studies have been conducted with a focus on interannual changes to the individual structures. Throughout the U.S. Mid-Atlantic region, several programs have utilized retired subway cars as artificial reef structures. “Redbird Reefâ€, a site located off the coast of Delaware, is an example of this, with over 900 emplaced subway cars in the artificial reef system. Sonar surveys have been conducted over the period 2012-2016, providing one of the most extensive monitoring efforts for an artificial reef. This study focuses on the changes to emplaced structures at a .45 x .2 km section of Redbird Reef on both short and long timescales. A focus is placed on changes to the positions of the subway cars relative to the seabed over the period 2012-2016 in terms of horizontal rotation and change in relief. A secondary focus is on storm-response dynamics of the cars, analyzing the extent and rates of change in relief and structural degradation during Hurricane Sandy in 2012 and Hurricane Joaquin in 2015. Changes in response to storm events can alter the relief of the artificial reef, potentially altering its ecological function within the local benthic and pelagic ecosystem