Loading...
Evaluating the Potential for Mutualisms to Enhance Restoration Success in Urban Salt Marshes
Journal Title
Readers/Advisors
Dr. Mark Lesser, Eileen Allen, Dr. Mary Alldred
Journal Title
Term and Year
Fall 2021
Publication Date
2021-12-15
Book Title
Publication Volume
Publication Issue
Publication Begin
Publication End
Number of pages
Files
Research Projects
Organizational Units
Journal Issue
Abstract
Efforts to restore degraded ecosystems often focus on the effects of single species on ecosystem processes while neglecting the influence of species interactions. Understanding these interactions can expedite the restoration process and prevent unforeseen negative outcomes. Spartina alterniflora (Saltmarsh Cordgrass) and Geukensia demissa (Atlantic Ribbed Mussel) play a foundational role in wetland biogeochemical processes and community structure in coastal marshes throughout the Eastern United States. The relationship between Spartina and Geukensia is widely considered to be a textbook example of a facultative mutualism. Spartina provide structure that promotes Geukensia settlement and shading that protects Geukensia from overheating and desiccation. Geukensia promote the growth of Spartina by transferring nutrients from the water column to sediments. Both species influence biogeochemical processes by altering oxygen and carbon availability in sediments. However, some studies in constructed and urban marshes have indicated that this interaction may be context-dependent, responding to environmental factors such as sedimentation and ambient nutrient availability. We performed a systematic review and meta-analysis to quantify trends in the strength and effects of this mutualism. We looked at how the two species affected biomass and growth of their mutualist, and we quantified the effects of both species on nitrogen-cycling processes. Mutualistic effects are significantly stronger in non-urban than urban systems, and in natural relative to recently constructed wetlands. The effect of the two species on the marsh nitrogen cycle remains relatively the same regardless of context. To determine the ability of Geukensia to recruit to a restored urban Spartina marsh, we examined patterns in the abundance and size distributions of Geukensia population data at two sites within Jamaica Bay (New York, NY), an urban site with significant human impact, over the period of 2005-2012. Elders East was the site of a 40-acre restoration in 2006, and JoCo was monitored as an unmodified reference site. Geukensia abundance and size increased at Elders East beginning two years after restoration, indicating that restored marshes provide suitable habitat for Geukensia. Initial colonization occurred along marsh edges and creek banks. Geukensia abundance declined at JoCo, possibly due to loss of edge habitat in the unrestored marsh. We performed a mussel addition experiment to investigate how the mutualism behaves under different sedimentation conditions. Our sediment depleted site was Elders East in Jamaica Bay, while our sediment replete site was Randall’s Island, an island in NYC’s Harlem River that was also the subject of a Spartina marsh restoration in 2006. We found that Geukensia presence did not significantly influence Spartina growth characteristics or soil organic content in these systems. There were greater differences between sites than between treatment types, but the site differences were still non-significant in most cases. The variability in the outcomes of the Spartina-Geukensia mutualism suggests that care must be taken when incorporating species interactions into habitat management programs.