LTER: CCE-LTER Phase III: Ecological Transitions in an Eastern Boundary Current Upwelling Ecosystem

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Upwelling regions are some of the most productive ocean ecosystems. The study region of the California Current Ecosystem (CCE) LTER is the southern sector of the California Current System (CCS), a major upwelling biome where the 67-year California Cooperative Fisheries Investigations (CalCOFI) program provides essential information characterizing both natural climate variability and progressive changes. The CCE site spans a biogeographic boundary region, hence is an early sentinel of climate change; shows low frequency variations that are correlated with much of the North Pacific; is the preferred spawning site for most of the epipelagic fish biomass in the CCS; exhibits a broad gradient of ocean conditions over a short geographic distance; encompasses an undisturbed, layered sedimentary record of the past two millennia; and has well-developed models. The California Current Ecosystem (CCE) LTER program addresses two over-arching questions: What are the mechanisms leading to different ecosystem states in a coastal pelagic ecosystem? What is the interplay between changing ocean climate, community structure, and ecosystem dynamics? This program will develop a new quantitative basis for forecasting the effects of climate perturbations on the management of key living marine resources, including numerous fishes, invertebrates, marine mammals, and seabirds. The study region also affects CO2 exchange and carbon sequestration, as well as human recreation, navigation, and the livelihoods of large numbers of U.S. residents. The site encompasses a National Marine Sanctuary and constitutes major spawning habitat for most of the epipelagic fish biomass in the CCS. This research will involve extensive training of graduate students, undergraduate REU's, and will create teacher opportunities. Public programs and outreach efforts will be expanded in collaboration with the Birch Aquarium at Scripps, to increase public awareness and understanding of climate effects on coastal pelagic communities, to connect the publicPhase II support of CCE led to extensive new findings: a new null hypothesis for abrupt ecosystem shifts, understanding of phenological changes in marine fish spawning, new roles for both Si- Fe interactions and mesopelagic fishes in mediating Carbon export, long-term changes in nutrient stoichiometry in upwelling source waters, eddy-mediated transformations of plankton production, and alterations of mesopelagic fishes in relation to ocean de-oxygenation. CCE studies of mesoscale frontal systems found marked effects of ocean fronts on organisms across the food web ranging from bacteria to marine fishes. Glider-based studies showed elevated phytoplankton and zooplankton biomass at frontal discontinuities and satellite studies showed that such frontal features are increasing in the CCE region. Several thousand people were reached through outreach activities. This award builds on the investigator's previous analyses of the mechanisms underlying abrupt changes in ecosystem state with three new program elements: (1) intensive analysis of cross-shore transport as a modulator of long-term ecosystem variation; (2) development of quantitative forecasts of the biotic effects of El Niño-Southern Oscillation; and (3) expansion of the ability to characterize ecosystem perturbations using molecular approaches. Multi-scale measurements of the five core LTER variables and their responses to secular ocean changes (warming, increased density stratification, de-oxygenation, and acidification) in the NE Pacific will be sustained. CCE-LTER studies are making excellent progress toward understanding ecological state changes and the development of a quantitative framework for forecasting future changes in ecosystem states in a major upwelling ecosystem. In this new award the investigators will conduct intensive shipboard Lagrangian process studies to test the role of cross-shore transport in exporting nutrients, other biogenic compounds, and organisms into the offshore zone, thereby modifying population dynamics and biogeochemical export. Climate sensitivity of cross-shore transport will be assessed using autonomous measurements and integrative modeling. Other mechanisms related to ecosystem transitions (in situ changes in stratification, alongshore advection, top down predation) will be analyzed, respectively, by field studies employing a space-for-time exchange, in situ and remote sensing measurements combined with modeling, and bioenergetic modeling. Collaborative studies will develop a new framework for forecasting ENSO effects on marine pelagic ecosystems along the U.S. west coast. Molecular approaches will be used to characterize trends in microbial diversity and associated plankton interactomes.