The CCE LTER signature datasets were chosen to exemplify ecosystem change occurring across trophic levels and at multiple spatial and temporal scales. These signature datasets span responses of inorganic nutrient supply, organic matter transport, net primary production and populations to ecosystem forcing. While some datasets were initiated with CCE LTER in 2004, others build on prior research allowing extended 75+-year time-series documenting ecological transitions in a coastal upwelling biome.
Nitracline Depth
CCE research has established that the depth of the nitracline (defined here as the shallowest depth at which nitrate exceeds 1.0 µmol L-1) is an excellent proxy for nitrate supply to the surface ocean. It has been shown to correlate with multiple metrics related to microbial community structure, including surface chlorophyll concentrations and the relative contributions of coastal and offshore microbial communities as assessed by sequencing of 16S and 18S rRNA. We measure nitrate (and other nutrient) concentrations using the colorimetric approach with an autoanalyzer. Samples are collected from multiple depths at all CalCOFI stations on each of our quarterly survey cruises. While CalCOFI nitrate measurements date back to the late 1960s, they only became a routine measurement in the early 1980s. In this dataset, we provide both standard nitracline depth (NCD) and nitracline depth extended (NCDx) which extrapolates the nitracline depth in regions in which surface nitrate exceeds 1.0 µmol L-1.
Data Access
Signature Data File
Nitracline Depth in EDI
Satellite-Observed Net Primary Production
CCE has developed a multi-satellite merged product for estimating net primary production remotely. This dataset is modified from the widely used VGPM model and has been extensively validated using net primary production measurements made daily by the H14CO3- uptake method on CalCOFI quarterly cruises. Data are available at daily resolution from Sep 6, 1997 to the (near) present and over a spatial range from 130 to 115°W and 30 to 50° with 4-km resolution. Sample maps are shown below (units are mg C m-2 d-1).
Data Access
Signature Data File
Low-Latitude Euphausiids
Euphausiid (krill) populations exhibit long-term variations that have been linked to changes in ocean circulation, including the Pacific Decadal Oscillation. We use a suite of low-latitude euphausiids (Euphausia eximia, Euphausia gibboides, Euphausia recurva, and Nyctiphanes simplex) as sentinel taxa that reflect enhanced northward transport into the CCE study domain. Euphausiids have been collected (and subsequently manually sorted) in net tows (0.505-mm mesh towed obliquely to a maximum depth of 140 or 210 m) at each station on springtime CalCOFI cruises since 1951. Data shown here includes the abundance (individuals m-2) of all phases and stages of the four taxa on CalCOFI lines 77 to 93.
Euphausiid (krill) populations exhibit long-term variations that have been linked to changes in ocean circulation, including the Pacific Decadal Oscillation. We use a suite of low-latitude euphausiids (Euphausia eximia, Euphausia gibboides, Euphausia recurva, and Nyctiphanes simplex) as sentinel taxa that reflect enhanced northward transport into the CCE study domain. Euphausiids have been collected (and subsequently manually sorted) in net tows (0.505-mm mesh towed obliquely to a maximum depth of 140 or 210 m) at each station on springtime CalCOFI cruises since 1951. Data shown here includes the abundance (individuals m-2) of all phases and stages of the four taxa on CalCOFI lines 77 to 93.
Data Access
Signature Data File
Phytoplankton Pigments
CCE uses phytoplankton diagnostic pigments as one way of tracking changes in phytoplankton community composition over time. Different taxa of phytoplankton have characteristic pigments that are used either as accessory light harvesting pigments or for photoprotection. For instance, fucoxanthin is typically considered diagnostic for diatoms, while divinyl chlorophyll a is considered diagnostic for Prochlorococcus. We note, however, that there are often exceptions to these general patterns and that pigment concentration is an imperfect proxy for biomass, because phytoplankton can adjust their pigment:carbon ratios in response to a dynamic light field. We measure phytoplankton pigments by high-pressure liquid chromotagraphy. Sampling intensity has varied throughout the CCE LTER period, although (at a minimum) we always sample two depths (typically surface mixed layer and deep chlorophyll maximum) at each CCE LTER cardinal station on the quarterly CalCOFI survey cruises. Figures below show log-transformed anomalies for surface mixed layer pigment concentrations.
Data Access
Signature Data File
Particulate Organic Carbon
CCE measures particulate organic carbon (POC) to track changes in the spatial distribution of organic matter in the ecosystem. POC refers to the total organic carbon content of all “seston” (i.e., suspended particles). Seston includes both living (prokaryotes, phytoplankton, and heterotrophic protists) and non-living (detritus) organic matter. CCE measures POC at all stations and multiple depths on quarterly CalCOFI cruises. POC is measured by first filtering water through a pre-combusted glass fiber (GF/F) filter (nominal pore size = 0.7 µm). Filters are frozen until analysis, at which point they are acidified to remove inorganic carbon and then analyzed with an elemental analyzer (returning both carbon and nitrogen contents of the seston).
Data Access
Signature Data File
Particulate Organic Carbon Dataset in EDI