The Relationship Between Shoreline Armoring and Adjacent Submerged Aquatic Vegetation in Chesapeake Bay and Nearby Atlantic Coastal Bays

Abstract

Shoreline armoring is an ancient and globally used engineering strategy to prevent shoreline erosion along marine, estuarine, and freshwater coastlines. Armoring alters the land water interface and has the potential to affect nearshore submerged aquatic vegetation (SAV) by changing nearshore hydrology, morphology, water clarity, and sediment composition. We quantified the relationships between the condition (bulkhead, riprap, or natural) of individual shoreline segments and three measures of directly adjacent SAV (the area of potential SAV habitat, the area occupied by SAV, and the proportion of potential habitat area that was occupied) in the Chesapeake Bay and nearby Atlantic coastal bays. Bulkhead had negative relationships with SAV in the polyhaline and mesohaline zones. Salinity and watershed land cover significantly modified the effect of shoreline armoring on nearshore SAV beds, and the effects of armoring were strongest in polyhaline subestuaries with forested watersheds. In high salinity systems, distance from shore modified the relationship between shoreline and SAV. The negative relationship between bulkhead and SAV was greater further off shore. By using individual shoreline segments as the study units, our analysis separated the effects of armoring and land cover, which were confounded in previous analyses that quantified average armoring and SAV abundance for much larger study units (subestuaries). Our findings suggest that redesigning or removing shoreline armoring structures may benefit nearshore SAV in some settings. Because armoring is ubiquitous, such information can inform efforts to reverse the global decline in SAVand the loss of the ecosystem services that SAV provides.

Interannual variation in submerged aquatic vegetation and its relationship to water quality in subestuaries of Chesapeake Bay

“…2). The large area, complex shoreline, and many tributaries make it difficult to identify generalities that apply throughout the estuary; therefore, prior studies have introduced the use of subestuaries as effective units of observation and analysis (King et al 2005, Li et al 2007, Patrick et al 2014, 2015. Each subestuary has its own local watershed (Fig.…”

“…Each subestuary has its own local watershed (Fig. 3), and subestuaries can be treated as replicates in statistical analyses that quantify regional patterns (such as relationships within a salinity zone) and estuary-wide patterns (Li et al 2007, Patrick et al 2014, 2015.…”

“…The Chesapeake Bay is a diverse system with 23 SAV species, which differ in substrate preference, morphology, minimum light requirement, heat tolerance, sensitivity to waves and other physical forces, growth rate, and dispersal capability (Bourn 1932, Backman & Barilotti 1976, Congdon & McComb 1979, Goldsborough & Kemp 1988, Steward 1991, Kimber et al 1995, Moore et al 2000, Kemp et al 2004. Dividing the estuary into salinity zones helps account for some of those differences (Moore et al 2000, Orth et al 2010, Patrick et al 2014, 2015 in SAV responses to stressors. For example, poor water clarity may have greater impacts on polyhaline SAV communities dominated by Zostera marina because Z. marina requires more light than the species dominant in the lower salinity zones (Batiuk et al 2000, Kemp et al 2004.…”

Local and regional disturbances associated with the invasion of Chesapeake Bay marshes by the common reed Phragmites australis

“…Broader-scale investigations are needed because the factors driving regional distributions may differ from drivers of distribution within individual ecosystems. Broader-scale analyses have been completed for other ecological responses in estuaries through spatial analysis of digital maps across large regions (Comeleo et al 1996;Paul et al 2002;Li et al 2007;Rodriguez et al 2007;Patrick et al 2014Patrick et al , 2016.…”

Twenty-first century climate change and submerged aquatic vegetation in a temperate estuary: the case of Chesapeake Bay

“…Related factors, such as changes in rainfall and the frequency and intensity of storms, will have important indirect effects that will be more specific to each estuary (Day, YanezArancibia, and Rybczyk 2011;Statham 2012;Porter et al 2013;Kennish, Brush, and Moore 2014). The predicted 0.7-1.6 m of sea-level rise in the Chesapeake Bay region will also impact SAV (e.g., Patrick, Weller, and Ryder 2016). Rates of predicted sea-level rise differ for various estuaries, in other regions, and these have been discussed elsewhere (e.g., Najjar et al 2010).…”