Site: California Current Ecosystem LTER

The Integrated Pacific Decadal Oscillation index (PDO, red) nicely predicts the variation in an important species of krill (Nyctiphanes simplex, blue) in the CCE site.
Credit: Di Lorenzo & Ohman, 2013

More than 60 years of zooplankton census data revealed that some populations respond indirectly to climate changes in two stages: first, ocean circulation responds to wind, then the zooplankton population level responds to ocean circulation. This broadly applicable principle of ‘double integration’ implies that direct correlations with climate variables should be replaced by metrics that reflect the biological time scale (e.g., life span) of the organisms concerned.