Seawalls have been found to support fewer mobile species than natural rocky shores, and other biological effects include changes of density, size, and reproductive capability of the organisms that live there.
One key difference between seawalls and rocky intertidal habitat is the lack of habitat heterogeneity and complexity associated with slope, rugosity, crevices, and overhangs that provide refuge from thermal stress, desiccation, and physical disturbances. While the shoreline of Seattle will likely never return to its natural state, some important physical characteristics that provide microhabitats and promote biological diversity may be integrated into future seawall design to improve the habitat there. In our project, we tested the potential benefits of slopes and crevices along Seattle’s Elliott Bay seawall. These elements were built into habitat enhancement panels to test whether engineered complexity could increase species diversity and abundance.