Mineral Accretion: An Environmentally Alternative to Plastic for Oyster Restoration

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 oysters. 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. These small plastics are commonly mistaken as a food item for marine organisms ranging in size from plankton to whales. Plastics can also leach out chemicals into the ocean, as well as, adsorb pollutants. It is now believed that these plastic pollutants may get passed up the food chain. This research is investigating the use of this an environmentally friendly material to replace the use of plastic as the base material for oyster restoration in a Florida based estuary. Steel mesh (in lieu of plastic) is attached to an impressed current cathodic protection system. Electricity is supplied to the steel mesh which will prevent corrosion and cause a rise in the local pH. This causes calcium and magnesium ions to combine with bicarbonate and hydroxide ions and precipitate as CaCO
3
or Mg(OH)
2
on the steel surface (mineral accretion). The electricity is supplied from a solar panel/lead acid battery source. In order to determine the efficacy of using mineral accretion mats for oyster restoration in the Indian River Lagoon, Florida, a two-phase experiment was designed to 1) determine the optimal steel and mesh size needed for oyster restoration and 2) determine if mineral accretion mats are as effective at promoting the growth of oysters and as traditional plastic mats.