UC Santa Cruz

Connectivity between and among ecosystems is a key feature of the marine environment, taking many forms, and affecting populations, food webs, and a wide range of ecosystem processes. In the kelp forest ecosystem, connectivity with adjacent habitats and with interacting human systems shapes communities and influences ecosystem functioning. However, the identity and strength of these important connections, and their key features and consequences are not well understood. One approach for incorporating various forms of connectivity into marine ecology is through the social-ecological systems framework. By characterizing a system as having both ecological and social components, both of which are affected by external forces and entities such as adjacent ecosystems, the presence and consequences of these connections become more clear. The purpose of this dissertation was to expand our knowledge of kelp forests by characterizing and quantifying two distinct forms of kelp forest connectivity. In Chapter 1, I explore kelp forest food webs through the lens of ecosystem connectivity with adjacent coastal pelagic habitats. I synthesize existing knowledge about relevant kelp forest consumers, data on the dynamics of open ocean organisms, and information on community responses to trophic subsidies to better understand kelp forest food webs. I then further assess the role of trophic subsidies from open ocean habitats by looking specifically at five species of kelp forest fishes in central California (Chapter 2). I use stable isotopes and traditional diet content analyses to evaluate the importance of pelagic-based energy for nearshore rockfishes, and to provide a better understanding of how the kelp forest fish assemblage accesses and uses energy sources from the open ocean. In Chapter 3, I turn to the connectivity between kelp forest ecosystems and associated social systems. The nearshore fishery is the primary commercial fishery operating in central California’s kelp forests. I use a social-ecological systems framework to characterize the nearshore fishery and create a social baseline from which to better understand the connections among fishermen, fishing operations, markets, and kelp forests where the target species reside. I use fishery-dependent landings data, archival sources, information gained from interviews, and long-term ecological monitoring data to inform the research. In Chapter 4, I dig more deeply into one component of social-ecological connectivity in the nearshore fishery, combining ecological and social data sources to shed light on factors influencing the species composition of fisheries landings, a key component of the nearshore fishery and kelp forest dynamics.

The study of ecosystem connectivity and social-ecological relationships is an interdisciplinary endeavor. In this dissertation, I use a mixed methods approach to add to our understanding of kelp forest trophic connectivity and the connections between humans and kelp forests. I draw on theory and literature from both the ecological and the social sciences, integrating ideas related to ecosystem connectivity and the human dimensions of natural resources management. I show that new and useful insights can be gained through interdisciplinary approaches that incorporate connectivity among marine habitats and with people into our concept of marine ecosystems.