The California Current Ecosystem (CCE) LTER site (http://cce.lternet.edu) is located off the southern coast of California, extending from San Diego north to San Luis Obispo and westward over 500 km. This area comprises an ecosystem that includes the California Current, which is the eastern current of the North Pacific Gyre. This gyre is a system of currents that circulate water around the north Pacific Ocean. In much of the California Current, winds acting on the sea surface transport nutrient-rich, deep water upward, where it becomes available to organisms that live near the ocean's surface. This process is called coastal upwelling. Upwelling ecosystems are among the most productive ocean ecosystems in the world.

The CCE region has been studied intensively for over 60 years by a group called the California Cooperative Oceanic Fisheries Investigations (CalCOFI). Because there is a long record of observations and a rich data set from this region, scientists have noted changes in the CCE that happen over a variety of time scales. These changes include a long term ocean warming trend that has been documented over the past 6 decades, the Pacific Decadal Oscillation, and El Niños. The Pacific Decadal Oscillation is a series of warming and cooling periods that occur in 20-30-year cycles. El Niño is an episodic change in the ocean-atmosphere system of the equatorial Pacific that occurs approximately every two to seven years. El Niño is characterized by increased ocean temperatures and decreased upwelling in the equatorial Pacific Ocean, yet has influences that extend to the California Current system and elsewhere around the world. Many of the studies conducted as part of the CCE-LTER focus on changes in the ocean ecosystem that occur over these different time scales.

Research Focus

The researchers of the CCE-LTER site study four mechanisms that may lead to rapid shifts in the California Current Ecosystem:

• Changes in the food web in response to changes in ocean stratification and the supply of nutrients
• Transport of different groups of organisms along the coast from the northern to the southern part of the California Current system (and vice versa).
• Transport of organisms from the coast to regions located far offshore. Coastal species can be lost from an ecosystem if currents transport them offshore away from their preferred habitat.
• Changes in predation.

Our LTER site addresses these hypotheses with an integrated research program that has three elements:

(1) Experimental Process Studies: These studies focus on the hypothesis that food webs change in response to the stratification of the water column. Stratification occurs when less dense water overlies more dense water. Increases in density stratification - which occurs, for example, as surface ocean waters warm faster than deeper waters - reduces the supply of nutrients from deep waters into surface waters, where they are needed to fuel the growth of microscopic algae called phytoplankton. The amount of stratification, which affects nutrient supply, varies across both space and time. During CCE LTER process studies, research focuses on changes in ocean stratification across space. Variations in the amount of nutrients available to phytoplankton in different places and at different depths may change the species that are present. This is particularly true for tiny, single-celled blue green algae, called cyanobacteria, which often serve as the base of the ocean's food web. Cyanobacteria are most abundant in areas where the boundary between nutrient-poor surface waters and nutrient-rich deep waters occurs at intermediate depths. CCE LTER scientists are conducting these process studies in order to understand how species of cyanobacteria and other organisms change in relation to the depth of this boundary between the nutrient-rich and nutrient-poor water. This information is being used in models of ocean physics and biology to determine how changes in ocean stratification may affect the CCE over time.

(2) Time Series Studies: A time series is a group of repeated, scientific measurements made in the same place but at different times. CCE LTER is using four types of time series to test the hypotheses described above. The first type of time series consists of measurements made at sea four times a year to enhance the pre-existing CalCOFI time series. These new CCE LTER measurements examine oceanic microbes, organic matter dissolved in sea water, organic matter found in the form of particles in sea water, and concentrations of iron, which is an essential nutrient for marine plants and algae. The second type of time series uses satellite observations that measure pigments produced by phytoplankton and sea surface temperature. The third type of time series uses more frequent measurements of phytoplankton and ocean temperature made at nearshore sites including the Scripps pier, other locations along the coast in a network called the Southern California Coastal Ocean Observing Systems (SCCOOS), and the Ocean Institute at Dana Point. The fourth type of time series uses robotic ocean gliders to make continuous measurements across the CCE region.

(3) Modeling studies are an important part of the research at the CCE-LTER site. Computer models are used to help interpret and understand what drives the observations made during the experimental process and time series studies; to provide a method of using equations to test hypotheses; and to provide a way to connect observations made in space and in time. The CCE-LTER site focuses on three different types of models. One kind of model looks at the biology and physics of the California Current ecosystem in four dimensions: latitude, longitude, depth, and time. Another type of model attempts to understand the interactions between bacteria, phytoplankton, zooplankton, and fish. The final kind of model attempts to understand the balance budgets of heat, salt, nutrients, oxygen, and phytoplankton that come into, move within, and leave the CCE.

Information Management

The Information and Data Management portion of the CCE-LTER helps researchers to organize their data, and facilitates the exchange of research findings with other LTER partners, educators, policy makers, and the general public. Our information system contains the data from the various components of the CCE-LTER and allows researchers to access and combine all of those data. All of the documentation and data associated with the CCE-LTER projects is controlled by an Ocean Informatics electronic hub at the Integrative Oceanography Division (IOD) at the Scripps Institution of Oceanography.
Contact: Karen Baker (kbaker@ucsd.edu) Information Manager

Education and Outreach

Our Education and Outreach program teams scientists with local scientific and educational facilities engaging the "K through grey" community in both the process and the understanding gained from this research. We train undergraduates, graduate students, and postdoctoral scholars across disciplinary boundaries. Through collaborations with formal and informal science education organizations, we reach many schoolchildren each year, including local low-income and minority students.
Contact: Beth Simmons (bsimmons@ucsd.edu) Education Outreach Coordinator

Mark D. Ohman (mohman@ucsd.edu) Lead PI, CCE-LTER
Scripps Institution of Oceanography, University of California, San Diego