This layer is intended to represent the geographic extent of NOAA Fisheries’ Trinidad Head Line Survey. The Trinidad Head Line ocean observing program started in 2007 and is led by NMFS Southwest Fisheries Science Center. This survey collects oceanographic and biological samples that inform quantitative studies of the California Current Large Marine Ecosystem. The Southwest Fisheries Science Center and Cal Poly Humboldt (CPH) have conducted frequent ocean observing cruises to characterize seasonal and interannual variability in the plankton ecosystem in coastal waters off northern California. In combination, these data give insight into how coastal ecosystems respond to seasonal cycles and larger scale climate dynamics, and contribute to a much broader coastwide collaborative effort to understand the dynamics of the California Current Large Marine Ecosystem. At five stations that span the continental shelf and upper continental slope, physical, biological, and chemical parameters are measured. Historically there have been six stations, but the sixth station is no longer an active sampling location as of 2014. Cruises occur approximately monthly throughout the year. Oceanographic parameters are measured throughout the water column (to a maximum depth of 500 m), and water samples are collected for assays of nutrients, chlorophyll, eDNA, and domoic acid. Zooplankton samples are collected from the upper 100 meters of the water column and analyzed to quantify changes in size of dominant krill species and variability in the community structure of krill, copepods, and larval fish in response to climate forcing.