Defining isoscapes in the Northeast Pacific as an index of ocean productivity

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 distrib...