Date of Degree

2-2022

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

J. Stephen Gosnell

Committee Members

Elizabeth Alter

Phillip Staniczenko

Dianne Greenfield

Mary Alldred

Subject Categories

Biology | Ecology and Evolutionary Biology

Keywords

salt marsh, Geukensia demissa, Spartina alterniflora, nonconsumptive effects, antipredator training, captive-rearing programs

Abstract

Species interactions may mediate the ability of organisms to survive in a community and provide valued services but are rarely fully considered in restoration planning. To address this, I considered how service provisioning will change as restored marsh communities mature and the value of incorporating antipredator training into captive-rearing programs.

For chapter 1, I explored how a facultative mutualism between Atlantic ribbed mussels Geukensia demissa and cordgrass Spartina alterniflora may enhance marsh growth and nitrogen cycling in a eutrophic setting. I created experimental plots in Jamaica Bay, NY, that contained live mussels, mussel shells, or no mussels (control) and measured sediment and plant characteristics after 9 weeks. I also collected sediment cores for use in continuous flow-through incubations with ambient site water and water enriched with stable isotope-labeled nitrate. Denitrification in marsh plots with live mussels was significantly higher than the other treatments. Live mussels likely enhanced denitrification as biodeposits increased sediment organic carbon and anaerobic conditions. Mussel treatments did not impact cordgrass growth, possibly due to the eutrophic conditions of our study system or the duration of our trials. Ribbed mussels may be a valuable addition for salt marsh restoration projects in eutrophic estuaries since they increase the ecosystem service of nitrogen removal.

For chapter 2, I compared the filtering and biodeposition rates of ribbed mussels in the presence of predators (blue crabs (Callinectes sapidus)), oyster drills (Urosalpinx cinerea)), injured conspecifics, or other local species (mud snails, Tritia obsoleta)) from the Hudson River estuary (NY) in laboratory experiments conducted in July–August 2019. The effect of predator diet on ribbed mussel responses was also considered. Although mussels tended to be less active in the presence of predators and injured conspecifics, significant decreases were observed in few traits, and there was no evidence that predator diet influenced mussel responses. Variability in feeding rates and other factors such as water quality may play a larger role than predator presence in determining mussel activity. These results suggest that G. demissa will continue to provide positive impacts on water clarity and quality and increase denitrification rates via biodeposition even as restored communities attract predators.

For chapter 3, I identified studies that analyzed changes in organisms following both antipredator training and lethal exposure to predators. Notably, I identified only 12 studies that analyzed outcomes in both training and lethal exposure settings and found the majority of measurements focused on traits. Although meta-analysis indicated that antipredator training changed prey traits and increased prey survival, relationships between changes in traits and fitness could not be assessed given the rarity of studies that included both outcomes. While these results support the general use of antipredator training, they also suggest that trait changes cannot be reliably used as proxies for fitness impacts.

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