During the first two years of study, mussels began to colonize the habitat panels. By the end of 2009 the percent cover of mussels was consistently higher on panels that had cobble surfaces, including the flat panels. The graph to the left shows percent cover of mussels at each elevation by panel design (finned, stepped, flat) and by surface treatment (smooth or cobble) in August 2009. Statistical analysis showed that the cobble surface was a significant factor in higher percent cover of Mytilus.
During the second two years of the study, mussels continued to increase on all of the panel types and were much more abundant than in the first two years. In the graph to the right, the red line shows the maximum coverage of mussels that was seen during the first two years, and shows how much more abundant they were on the panels by the end of the study.
Mussels are known as ecosystem engineers, and mussel beds can increase habitat complexity and species richness and have been identified as key structures for consideration in conservation and management goals. While they can dominate the intertidal zone and exclude some larger organisms that compete with them for primary space, they can also have positive effects on many secondary space inhabitants. Mussels support species exclusive to mussel beds and increase abundance of generalist species, and these effects can increase with mussel bed age and size. Some species of mussels have been documented to increase species richness by hundreds of species. They also provide prey for birds and a variety of marine invertebrates . Organisms within the mussel matrix were not sampled in this study, though they may be developing and contributing to the seawall community.