Twelve 150m study sites in four tributaries of the Delaware Estuary (3 per tributary). (A)

1. The Relationship Between Ribbed Mussel (Geukensiademissa) Density and Salt Marsh Shoreline ErosionJoshua Moody1, David Bushek1 and Danielle Kreeger21Rutgers, Haskin Shellfish Research Laboratory, Port Norris, NJ 2Partnership for the Delaware Estuary Wilmington, DE Introduction Preliminary Results Erosion as a Function of Percent Mussel Cover A • Increasing storm severity, boat wakes, and sea-level rise threaten salt marshes. (A) • The synergistic relationship between the ribbed mussel Geukensiademissa and Spartinaalternifloramay provide some protection. • Deposition of nutrient rich feces from mussels enhances production of S. alternifloracreating levees along the marsh edge which trap sediments, enhancing vertical accretion. (Bertness, 1984) • Marsh shoreline erosion precludes levee formation. • The physical structure formed by mussel aggregations may provide stability to the marsh edge (B), but data are lacking. B Hypothesis:Within an energy regime, salt marsh shoreline erosion decreases as mussel density increases. Methods • Twelve150m study sites in four tributaries of the Delaware Estuary (3 per tributary). (A) • Site 1 is located at tributary mouth. • Site 2 is located above first meander. • Site 3 is located up river where wave action is lower. • Each site was demarcated with 31 transects located five meters apart along the marsh edge. • A permanent post was placed 1 m back from the marsh edge at each transect. A • Contrary to our expectiatons, preliminary data from these six sites suggest only the slighest relationship between erosion and percent mussel cover. As data from six more study sites are incorporated, more prominent trends may emerge. • These data do not consider mussel density, mussel demographic, or mass transport rates. • Percent mussel cover, mass transport and erosion will be investigated using multivariate statistical analysis in order to analyze the potentially complex relationship between them. • Regardless of the relationship between ribbed mussels and erosion, ribbed mussels may provide several other valuable ecosystem services such as levee formation, nutrient cycling, biological filtration, and increasing habitat complexity. B • Objective 1: Quantify Mussel Demographics (Bertness and Grosholz, 1985): percent mussel cover quantified at each transect; ten 25cm 2 samples excavated for mussel density and demographic analysis. (B) • Objective 2:Quantify Mass Transport Rate of Water (Yokoyama et al 2004): dissolution rates of plaster-o-paris hemispheres (clods) measured at each transect . (C) • Objective 3: Quantify Lateral Marsh Movement: Change in the position of the marsh edge from each permanent transect post was measured after one year . (D) • Analysis: Lateral marsh movement, mussel density, and mass transport rate will be compared within sites, among sites and among tributaries using standard statistical analysis (correlation, regression, ANOVA, and ANCOVA). C Funding Provided By Literature Cited Bertness, M.D. 1984. Ribbed Mussels and Spartina alterniflora production in a New England salt marsh. Ecology. 65(6): 1794-1807. Bertness, M.D. and E. Grosholz. 1985. Population dynamics of the ribbed mussel, Geukensia demissa: The costa and benefits of an aggregated distribution. Oceologica, 67:192-204. Yokoyama, Hisashi, Misa Inoue, and Katsuyuki Abo. 2004. Estimation of the assimilative capacity of fish-farm environments based on current velocity measured by plaster balls. Aquaculture, 240: 233-247. D • National Shellfisheries Association • Delaware National Estuarine Research Reserve • Society of Wetlands Scientists • National Fish and Wildlife Foundation • New Jersey Sea Grant