Aim: We modeled isoscapes in the Northeast Pacific using satellite-based data with the main objective of testing if isoscapes defined by a few key parameters can be used as a proxy for secondary productivity.

Location: Northeast (NE) Pacific; 46 – 60⁰N and 125 – 165⁰W.

Time period: From 1998 to 2017 (ongoing).

Major taxa studied: Zooplankton with a focus on large herbivores.

Methods: Approximately 280 summer zooplankton samples were analyzed for Carbon (δ¹³C) and Nitrogen (δ¹⁵N) stable isotope (SI) ratios. Environmental conditions experienced by zooplankton organisms were extracted from satellite, in situ sensor and model databases. A generalized additive model approach was used to explain the spatial variability of δ¹³C and δ¹⁵N values and predict isoscapes.

Results: Sea surface temperature (SST), sea level anomaly (SLA) and chlorophyll-a concentration emerged as the significant SI predictors. Modelled isoscapes reproduced patterns observed in δ¹³C and δ¹⁵N value distribution, such as a decrease from the coast to offshore. The contribution of eddies in enhancing local production in the open ocean was also well captured by the models. In the central part of the NE Pacific higher SI values were correlated with higher large copepod biomass measured by the North Pacific Continuous Plankton Recorder (CPR) survey. However, in the area off the coast of British Columbia (BC) high δ¹⁵N variability appeared to be associated with episodic intrusions of coastal waters demonstrating that caution is needed when interpreting sharp changes in SI ratios.

Main conclusions: While the mechanisms driving SI ratio variability are complex, we demonstrated that a few parameters used as a proxy for some of these major mechanisms are able to successfully produce isoscape models. This approach was proven useful to provide a qualitative estimate of the secondary production, which can be particularly valuable in a region where few data are available.

Approximately 280 summer zooplankton samples were analyzed for Carbon (δ¹³C) and Nitrogen (δ¹⁵N) stable isotope (SI) ratios. Environmental conditions experienced by zooplankton organisms were extracted from satellite, in situ sensor and model databases. A generalized additive model approach was used to explain the spatial variability of δ¹³C and δ¹⁵N values and predict isoscapes.

We provide C and N isoscapes at zooplankton level for the NE Pacific for 1998-2017. The uncertainties associated with the predicted values are provided as well and should be considered when using the isoscape value. Please don't hesitate to contact the corresponding author for any questions that you might have about the isoscapes production and uses. See ReadMe file for data structure information.