This project will compare the structure and dynamics of central and southern Californian nearshore ecosystems by parameterizing and analyzing the performance of three approaches for modeling these areas. The goals are to develop analytical tools to facilitate ecosystem-based decision making and management, and to forecast how marine reserves and the impending re-invasion of sea otters to southern Californian waters will affect the region's fisheries. The investigators will synthesize and leverage an array of preexisting data from spatially-extensive, long-term monitoring efforts. Along with a time series on the range, density, and feeding habits of sea otters, community data from a network of MPAs and reference sites of known age will provide the large-scale observational experiments needed to disentangle the effects of sea otters and MPAs on the structure and dynamics of California's nearshore ecosystems and their fisheries. The results will be incorporated into three different approaches: 1) EcoPath with EcoSim, 2) Metabolic scaling theory, and 3) Loop Analysis. These models range in data requirements, ease of application, and assumptions, and they vary greatly in the extent to which they simplify biology's complexity. By employing multiple modeling approaches, one can compare predictions for how the effects of MPAs and the impending re-invasion of sea otters will affect the productivity, dynamics, and resilience of these important communities. The data synthesis, analyses, and modeling efforts will provide ecosystem-based information to facilitate management decisions that will be needed in dealing with the impending conflict between the government's protection and supported re-establishment of a federally threatened species, and the preservation and governance of numerous fisheries. The comparisons will advance our understanding of ecosystem processes in central and southern CA kelp forests, including the interaction between bottom-up and top-down processes, and how these are influenced by geographic variation in key structural and functional attributes. On a more practical level, this work will result in 1) a set of analytical tools and effective and transferable ecosystem-based indicators to assess the status, thresholds and resiliency of nearshore temperate reef ecosystems; and 2) a collection of ecosystem-based predictions of short- and long-term community dynamics, including resiliency to environmental change and to commercially and recreationally valued kelp forest fisheries. These products will inform the design of monitoring and evaluation programs for MPAs, and will be especially useful for fisheries managers by helping them predict and accommodate the impacts of the re-invasion of sea otters into southern CA kelp forests. The project will also fulfill educational objectives through the training of 3 postdocs and 1 (Hispanic) graduate student in the development and application of ecosystem models and indicators. Postdocs will receive training in how to convene and run workshops, and to communicate scientific findings to resource managers and policymakers. Finally, the work will lead to the development of a collaborative partnership between academic researchers, NOAA fisheries scientists and USGS ecologists.
Forests of giant kelp (Macrocystis pyrifera) occur on shallow rocky reefs along the western coast of North America and other temperate regions of the world. Among the most productive ecosystems on Earth, these forests create habitat and primary production that support species rich communities. Culturally and economically important commercial and recreational fisheries target many species of finfishes and invertebrates (e.g., sea urchins, spiny lobster, abalone) within kelp forests. Recent establishment of marine protected areas (MPAs) throughout the coast of California and elsewhere holds the potential for increasing size and abundance of fished species, particularly those higher in the food chain. These changes may have consequences that amplify throughout forest foodwebs and are difficult to predict. Moreover, in kelp forests off southern California, important fisheries for spiny lobster, California sheephead, and red urchin are likely to be significantly impacted if populations of the federally listed southern sea otter (Enhydra lutris nereis), a voracious predator considered to be a "keystone" species, continue to grow and expand southward to their historical geographic limits. In order to understand and proactively address these potential changes to kelp forest ecosystems along the coast of California, we developed analytical tools that facilitate ecosystem-based decision making and management. These tools will allow us to forecast how marine reserves and the impending re-colonization of sea otters will affect both the ecosystems in the region and the valued fisheries they support. Using large-scale and long-term monitoring data from central and southern California kelp forests we characterized the composition and dynamics of these communities in order to inform and calibrate ecosystem-based models such as Ecopath with Ecosim, loop analysis, and allometric models. These ecological models required an unprecedented collection of quantitative information about life-history traits, demography, and interactions of kelp forest species. To accomplish this we constructed an online interactive database (http://kelpforest.ucsc.edu/) and enlisted dozens of researchers doing kelp forest related work at several research institutions from Mexico to Alaksa to collect and enter thousands of observations from the scientific literature. This database will be maintained in perpetuity, and can be expanded for application to other ecosystems and fields of research. Key findings of the modeling and empirical analyses conducted for this project include the following results: Fishing of one or more species of finfish has impacts on abundance (biomass) of organisms at all levels within kelp forest food webs. Our models show these effects are greater when particular species of fish and ecological roles (e.g., plankton eaters) are targeted. Species showing strong indirect responses to fishing are therefore the most important to monitor for the impacts of fishing or the establishment of MPAs As expected, models show the abundance of the foundation species, giant kelp, has important effects on biomass levels higher in the food web, however, the amount of year-to-year variability in kelp abundance, which is predicted to increase under changing climate conditions, can have equally important consequences. Models that incorporate species body size in food web networks perform better at predicting the behavior of the foodweb than those that do not, and this benefit actually increases as these networks become more complex. Giant kelp and urchin populations show dramatic phase shifts in southern California kelp forests. We tested a suite of potential early warning indicators to identify tipping points between algae and urchin-dominated periods within a 31 year record of monitoring data. None of the indicators tested were effective predictors suggesting that the phase shifts are complex and likely governed by multiple and external interacting processes. Size-selective fishing on one species, the California sheephead, was shown to alter its ability to regulate urchin populations. Measures such as increased minimum size limits and marine reserves may serve to restore historical trophic roles of key predators and thereby enhance the resilience of marine ecosystems. This project has also had an enormous impact on the training and career development of numerous affiliated researchers. Over fifty undergraduate students participated in collecting data for the online database. One graduate student developed expertise in ecological models and completed a PhD dissertation. Five post doctoral researchers have participated in the project and have since advanced in their careers, three in academic faculty positions and two as researchers at federal agencies. The study has fostered research collaborations among academics at several universities and federal researchers (National Marine Fisheries Service, US Geological Service). These data syntheses, analyses, and modeling efforts have generated conclusions and tools that can be applied to facilitate difficult management decisions. These are particularly necessary in dealing with the impending socioeconomic conflict between the government’s protection and supported re-establishment of a federally threatened species, and the sustainability of numerous valued fisheries. These ecosystem models can also be used to provide realistic targets for the performance of networks of marine reserves, providing a benchmark for their evaluation and potential adaptive management.
