Cathodically protected steel as an alternative to plastic for oyster restoration mats

Abstract

Oyster populations in many coastal areas have decreased as a result of overharvesting and habitat degradation. In order to help restore oyster populations and natural water filtration, many restoration efforts utilize plastic mesh to reseed oyster reefs. However, plastics do not break down or mineralize in seawater, instead they break down into smaller and smaller pieces eventually becoming what is termed microplastics. One alternative may be the use of a cathodically protected steel which develops a mineral accretion layer and enhances calcareous marine growth. In order to test the efficacy of this material for oyster restoration and its ability to promote oyster growth, a field experiment was designed to compare it to traditional plastic mats at three locations. At all sites, the steel mats were able to promote the recruitment of oysters at a rate equal to or greater than the plastic mats. The amount of mineral accretion and the total number of oysters present on the mats were dependent on the environmental and ecological conditions of the test site. The steel mats were easy to work with, provided sufficient oyster settlement, and gain in weight over time. This makes them an attractive alternative to plastic oyster restoration mats, with implications for creating artificial reefs or living shorelines.