 Twelve 150m 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. The Relationship Between Ribbed Mussel (Geukensia demissa) Density and Salt Marsh Shoreline Erosion The Relationship Between Ribbed Mussel (Geukensia demissa) Density and Salt Marsh Shoreline Erosion Joshua Moody 1, David Bushek 1 and Danielle Kreeger 2 1 Rutgers, Haskin Shellfish Research Laboratory, Port Norris, NJ 2 Partnership for the Delaware Estuary Wilmington, DE B A Introduction A Funding Provided By  National Shellfisheries Association  Delaware National Estuarine Research Reserve  Society of Wetlands Scientists  National Fish and Wildlife Foundation  New Jersey Sea Grant Bertness, M.D Ribbed Mussels and Spartina alterniflora production in a New England salt marsh. Ecology. 65(6): Bertness, M.D. and E. Grosholz Population dynamics of the ribbed mussel, Geukensia demissa: The costa and benefits of an aggregated distribution. Oceologica, 67: Yokoyama, Hisashi, Misa Inoue, and Katsuyuki Abo Estimation of the assimilative capacity of fish-farm environments based on current velocity measured by plaster balls. Aquaculture, 240: Literature Cited 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). Hypothesis: Within an energy regime, salt marsh shoreline erosion decreases as mussel density increases.  Increasing storm severity, boat wakes, and sea-level rise threaten salt marshes. (A)  The synergistic relationship between the ribbed mussel Geukensia demissa and Spartina alterniflora may provide some protection.  Deposition of nutrient rich feces from mussels enhances production of S. alterniflora creating 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. Methods C D B Preliminary Results Erosion as a Function of Percent Mussel Cover  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.