the key organisms that will build and maintain the reef are appropriate for use at the site (i.e., the intended species of coral or shellfish will likely survive, grow, and successfully reproduce in the environment). This can most simply be identified by any evidence that these organisms are already thriving nearby under similar environmental conditions. For coral reefs, a site should have sufficient light conditions and water quality comparable to those at nearby thriving reefs, taking into account the nutrient and turbidity levels, water temperature, depth, and flow conditions (Edwards and Gomez 2007). Also, it is important to consider the distance to adjacent healthy reefs to support larval replenishment to facilitate recovery and colonization of the restored reefs (Abelson 2006). Furthermore, the sites selected for establishing new reefs should have sufficient settlement space for outplanted corals or shellfish that includes barren and stable reef rock areas that lack excessive algal growth, or a sandy seabed that is sufficiently stable to place artificial structures without the risk of being smothered from the movement of itself or the sand. An example of an oyster reef pilot project is described in “Shellfish Reef as Shoreline Protection.”
Shellfish Reef as Shoreline Protection The oyster reef pilot project in the Eastern Scheldt in the Netherlands (Figure 12.7) aimed to prevent erosion by using reef-forming Pacific oysters. This oyster builds 3D reef structures that can be effective in dissipating wave energy and thus protecting adjacent shorelines from erosion. To grow the reefs, a substrate of oyster shells was placed on the tidal flat. To prevent the shells being washed away with the tide or during storms, they were stowed in boxes made of steel wire known as gabions. In the summer, oyster larvae, which need a hard substrate on which to grow, attach themselves to the shells and gradually build up a solid reef structure that can withstand winds and waves. Once the oysters have established, the steel wires of the gabion corrode away, after which the reef will have to survive on its own, constantly renewing itself by settlement of new larvae. During the past decade, the experiments in the Eastern Scheldt have demonstrated that the use of oysters as ecosystem engineers for erosion prevention is technically and biologically feasible and socially acceptable. The projects in the Eastern Scheldt have shown that highly dynamic environments such as estuaries, where interlinked physical processes are at work, offer exciting opportunities to build with nature.
12 | Reefs
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