Impact of breakwaters on sediment characteristics and submerged aquatic vegetation

Abstract

This study examined the impact of breakwaters, with varying ages (1-19 y) and in 3 salinity regions of Chesapeake Bay, on sediment characteristics and submerged aquatic vegetation (SAV). Sediment and SAV characterisitcs were determined at an adjacent-exposed and a breakwater-protected site in 24 locations. A mesocosm experiment was also conducted to evaluate SAV response to 4 organic-content treatments for 3 SAV species (Ruppia maritima, Vallisneria americana, and Zannichellia palustris). Breakwater effects on sedimentation were site-specific, some sites, having no apparent affect, while others where sandy shoreline erosion was dominant, an increase in grain size and sedimentation rate was observed. At other sites breakwaters facilitated fine-sediment deposition. SAV responses in the mesocosms, were highly variable with organic content. Therefore, SAV biomass in breakwater-protected area was related to the amount and type of sediments that the breakwater retained. Site evaluations should be conducted before breakwater construction if SAV colonization is desired.