THE EFFECT OF THE EL NIÑO SOUTHERN OSCILLATION ON ZOOPLANKTON PHENOLOGY IN THE CALIFORNIA COAST

The El Niño Southern Oscillation (ENSO) is the most dominant interannual climatic phenomenon globally. However, the ways in which ENSO impacts the phenology of zooplankton, the primary consumers in the majority of marine food webs, is poorly understood. While ENSO comprises three phases (El Niño, La Niña, and neutral periods), much of the research focuses on El Niño events and changes in zooplankton biomass only. This is despite evidence that La Niña influences nutrient upwelling, and that different zooplankton taxa respond differently to ENSO events. Here, we examine how both El Niño and La Niña events, as well as their affected environmental variables, impact zooplankton taxa phenology using empirical data spanning two decades. Using data sampled within the California Coastal System (CCS), we assessed the timing of peak biomass to determine phenological differences between taxa during different ENSO phases. Our results demonstrate that phenological shifts vary greatly between taxa. Our results also show that there is a regional pattern in that Eastern Pacific (EP) El Niño and La Niña events are associated with delayed peaks in the majority of taxa examined, while Central Pacific (CP) El Niño and La Niña events are associated with earlier peaks in most taxa. We also found environmental variables that were strongly associated with phenological disruptions during different ENSO events. Our work furthers the understanding of how ENSO impacts zooplankton and gives insight into how these effects will respond to ongoing climate change leading to the disruption of ENSO events.

Presentation Preference: Oral

Primary Presenter: Fiona Madsen, McGill University (fionacmadsen@gmail.com)

Authors:

Fiona Madsen, McGill University  (fiona.madsen@mail.mcgill.ca)

Sean Connolly, Smithsonian Tropical Research Institute  (connollys@si.edu)

Frederic Guichard, McGill University  (fred.guichard@mcgill.ca)