Within-marsh and Landscape Features Structure Ribbed Mussel Distribution in Georgia, USA, Marshes

Abstract

Ribbed mussels, Geukensia demissa, are marsh fauna that are used in coastal management and restoration due to the ecosystem services they provide. Ribbed mussel restoration efforts may be improved with a greater understanding of the environmental drivers of ribbed mussel distribution at multiple spatial scales to predict areas where restoration could be successful. This study sought to estimate the effects of within-marsh (4 m) and landscape (500 m) factors on ribbed mussel distribution. Ribbed mussel densities were surveyed at 11 sites along the coast of Georgia, USA, and overlaid with spatial data for within-marsh factors (elevation, distance to marsh features, slope) as well as landscape factors (percent cover by subtidal creek, forest, and development within a 500-m radius). The distribution model was then validated using three previously unsurveyed marshes and explained 55% of the variance in ribbed mussel abundance. Ribbed mussel abundances and occupancy were most sensitive to changes in within-marsh factors (elevation and distance to subtidal creeks, bodies of water inundated during the full tidal cycle) but were also sensitive to landscape features (percent landcover of forests and development). The highest ribbed mussel densities were found in mid-elevation areas (~ 0.7 m NAVD88), far from subtidal creeks, and in marshes surrounded with forest and development. These results contrast with distributions in the northeastern USA, where ribbed mussels are distributed along subtidal creek banks. This work suggests that restoration may be most effective when focused on appropriate elevations and at locations away from the marsh-creek ecotone.

Density‐dependent influence of ribbed mussels on salt marsh nitrogen pools and processes

“…m −2 ) fell well above a threshold (16 ind. m −2 ) previously determined for high mussel coverage in Georgia salt marshes (Annis et al., 2022). Positive density dependence of nitrogen removal is likely driven by similarly dependent mechanisms of enhanced nitrification (see Section 4 above; Figure 1a) that increase nitrate availability for denitrification via anaerobic microbial metabolism (Bilkovic et al., 2017; Laverock et al., 2011; Matheson et al., 2002).…”

“…Doboy Sound receives fresh-and saltwater input from the Altamaha River and the Atlantic Ocean, respectively. Mussel distribution and vegetation structure along Old Teakettle Creek were typical of salt marshes in southeastern US estuaries, with the highest mussel densities at mid-elevation platforms (i.e., short form cordgrass) surrounding the heads of intertidal creeks (Annis et al, 2022;Crotty & Angelini, 2020;Kuenzler, 1961;Lin, 1989). In summer 2017, a mussel manipulation was performed at the site as described in Williams et al (2023).…”