Ecosystem Functions of Pacific Northwest Estuaries: The Role of Ocean and Watershed Drivers in Eelgrass and Coho Salmon Dynamics

• Main Author: Magel, Caitlin L.
• Other Authors: Chan, Francis, Hacker, Sally D., Rumrill, Steven, Brown, Cheryl, Gitelman, Alix, Lewis, David, Integrative Biology
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Oregon State University
• Subjects: Eelgrass; Coho salmon; Pacific; Ocean acidification
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/gt54kv37z

Interest is expanding for the potential role of estuaries, particularly seagrass and salt marsh habitats, to sequester carbon, mitigate ocean acidification, and support abundant fisheries. The important functions of estuaries are part of a broader set of ecosystem services, or benefits to humans, which are regulated by ocean and watershed dynamics. The aim of this dissertation is to investigate ocean and watershed dynamics to better understand the key drivers and consequences of ecosystem change in Pacific Northwest (PNW) estuaries. Chapters 2, 3, and 4 of my dissertation address gaps in our understanding of ecosystem change in PNW estuaries and improve our ability to address estuary management challenges in the face of climate and other human-driven changes. Chapter 5, although distinct from my other chapters, aligns with the theme of my dissertation, which is to understand the drivers and consequences of climate and human-driven changes for important coastal organisms and habitats. In Chapter 2, I investigate the relative role of ocean, estuary, and watershed drivers in determining macrophyte (eelgrass Zostera marina and ulvoid macroalgae) production among four PNW estuaries (Willapa Bay, WA, Netarts Bay, OR, Yaquina Bay, OR, and Coos Bay, OR) between 2006-2019. Significant environmental change has occurred over this time period, including the longest marine heatwave event (anomalously elevated water temperature) on record in the northeast Pacific Ocean. Substantial changes in macrophyte ecosystems were observed, however responses differed among the four estuaries. These findings provide a framework for predicting the response of macrophytes in PNW estuaries to environmental change and indicate that some estuaries may be more resilient to these changes than others. In Chapter 3, I investigate the drivers and consequences of recent declines in eelgrass and ulvoid macroalgae in South Slough, Coos Bay, Oregon via a record of macrophyte communities and environmental variables of ocean, estuary, and watershed ...