Date of Award


Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)


Biology/Environmental Biology

First Advisor

Jarrett E. K. Byrnes

Second Advisor

Georgia Mavrommati

Third Advisor

Robert Stevenson


Humans affect marine ecosystems worldwide, impacting species ranges, food web dynamics, ecosystem functioning, and ecosystem services. Subsequently, there is a dire need to understand environmental change from a holistic perspective by incorporating manipulative field experiments, quantitative and qualitative modeling, stakeholder engagement, and causal inference. Such causal and transdisciplinary approaches to climate change research provide scholars and the public with much needed insight to prevent and prepare for coming environmental alterations. Research outlined in this dissertation works to achieve this goal. After describing broad goals of this dissertation in chapter 1, we used a field experiment and structural equation modeling in chapter 2 to explore the relative impacts of the range expanding ecosystem engineering mud fiddler crab Minuca (Uca) pugnax on ecosystem functioning in both its historical habitat in Folger’s Marsh at UMass Boston Nantucket Field Station and its expanded range in the salt marshes of Plum Island Estuary (PIE) Long Term Ecological Research (LTER) site. In chapter 3, we explored the impact that the fiddler crab range expansion has on PIE food web dynamics using a qualitative network model and asked if alterations in PIE webs cascade to alterations to PIE ecosystem functioning. Finally in chapter 4, we determined the effect that both the mud fiddler crab range expansion and sea level rise have on PIE marsh area and ecosystem services provisioning, and the ability for mitigation policies to buffer both environmental changes, by administering a stakeholder survey and building a system dynamics model in Stella Architect. We found that fiddler crabs directly weaken sediment strength and indirectly increase aboveground biomass of Spartina alterniflora in both its historic and expanded rages, demonstrating predictability in how range expanders influence expanded habitats relative to historic ranges. Fiddler crabs also reduce sediment stability by reshuffling winners and losers in PIE food webs. Finally, fiddler crab simulated marsh erosion and high sea level rise dramatically reduced both total marsh area and recreational services provisioning; however, mitigation policies eliminated a crab effect and buffered losses due to sea level rise. Taken together, our research outlines the effects of environmental change on multiple ecosystem processes, which requires a transdisciplinary approach to uncover their individual and combined impacts.


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