Using a Lagrangian particle tracking model to evaluate impacts of El Niño-related advection on euphausiids in the southern California Current System

We propose a framework to examine the extent which advection alone can explain spring biomass fluctuations of six euphausiid species in southern California Current System (CCS) between 2008 and 2017. modeled population changes as fluxes from defined source boxes using currents State Estimate (CASE), regional optimization MIT general circulation model. This period encompasses Central Pacific El Niño (2009–10), Warm Anomaly (2014–15) Eastern (2015–16). Total populations all show strongest positive correlations with time-lagged flows preceding November–December. Three cool-water (Euphausia pacifica, Nematoscelis difficilis, Thysanoessa spinifera) opposite patterns for their calyptopis (larval) adult phases, calyptopes February–March flow suggesting periods situ reproduction. In contrast, three subtropical (Nyctiphanes simplex, Euphausia eximia, gibboides) consistent correlation across entire into region during enhanced favorable flows. tested whether interannual variations size were influenced by different winter-origin waters compared non-Niño years. found that associate less strongly more southern-origin anomalous Advection accounts varying proportions fluctuations, influences N. difficilis T. spinifera. Explicit measurements growth mortality rates are needed further resolve additional factors influencing events, implications future forecasts.