NCCOSfunded scientists from the University of North Carolina documented the effect of rocky sills (shore-parallel, rock structures) on near shore habitat. Short rock sills are a common stabilization method and a living shoreline restoration technique, but little is known about their effects. The researchers studied algal mat abundance at two sites of silled marsh compared to adjacent shorelines with no stabilization.
At the seaward marsh edge, macroalgal abundance in natural marshes was 4 times larger and displayed more taxonomic richness than in silled marshes; marsh grass abundance was not affected. Since these habitats provide sustenance to many juvenile fishes and invertebrates extensive use of sills may have an unanticipated adverse effect on fisheries.
This new finding suggests that living shorelines alter the abundance of benthic algal primary producers indicating the full impact of sill installation on subtidal and marsh communities is not understood.