UC Santa Cruz

In many systems there has been extensive loss of foundation species and associated ecosystem services over the past century, as human alterations have increased. This is particularly true in temperate estuaries, where the main foundation species—salt marsh, seagrasses and oysters, have been in a state of decline. As restoration and conservation efforts increase, there is a critical need to better understand factors that affect the recovery of estuarine foundation species, as well as to characterize the consequences of such recovery. My dissertation research examines drivers and consequences of loss and recovery in two foundation species in Elkhorn Slough, a highly impacted estuary in Central California.

In Chapters 1 and 2, I explore the role of a prolific crab species as both a consumer and ecosystem engineer in marsh ecosystems. I focus on vulnerable marsh edges prone to marsh loss; tidal creek bank edges (Ch. 1) and salt pannes. (Ch. 2). In Chapter 1, I show that crab grazing and the engineering of extensive burrow networks has a negative effect on marsh biomass, and this combined effect compromises the ability of the marsh to stabilize sediments, prevent erosion, and accrete and track sea level rise. In Chapter 2, I show that the rate of marsh recovery and panne contraction is driven by both physical and biological drivers. In Chapter 3, I conducted two small-scale experimental seagrass restorations and tracked structural and functional recovery. I detected astonishingly rapid expansion of restored plots and a related increase in associated ecosystem services such as biodiversity and improvement of water quality. Unlike other foundation species (corals, mangroves, redwood forests), seagrasses are fast-growing and I have demonstrated the rapidity of restoration success and a trajectory of multifunctional recovery.

My work highlights how estuary management can be improved by investigations grounded in experimental field ecology, because they increase our understanding of the spatial variability of top-down effects and how they affect ecosystem function. In highly impacted estuaries like Elkhorn Slough, testing restoration strategies and their broad-scale outcomes are also critical for informing adaptive management and conservation efforts through time.