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INVESTIGATING EFFECTS OF ANOMALOUS OCEANOGRAPHIC CONDITIONS ON PELAGIC FOOD WEB DYNAMICS IN THE CALIFORNIA CURRENT USING STABLE ISOTOPE ANALYSES (E)

Evaluating ecological impacts of the recent marine heatwave and 2015-2016 El Niño event in the northeastern Pacific Ocean is crucially important for predicting ecosystem responses to future events. Using stable isotope analysis to elucidate food web dynamics and energy flow is one method by which to evaluate ecosystem responses to environmental perturbations like El Niño-Southern Oscillation (ENSO) events. Nitrogen stable isotope values (δ15N) can be used to evaluate the diets of consumers, food web structure, and changes in isotopic baselines and primary production. We analyzed δ15N values of quarterly-collected zooplankton samples in the central California Current to evaluate the response of the copepod, Calanus pacificus, to recent anomalous conditions. We analyzed copepod δ15N values at two stations, one offshore and one nearshore, to specifically evaluate fluctuations in diet and trophic position, and nitrogen biogeochemical cycling associated with the anomalous warm conditions in the northeastern Pacific from 2012-2016. Our preliminary analyses suggest an overall increase in δ15N values with the onset of positive ENSO conditions in the California Current. We found high seasonal variability, and differences between nearshore and offshore stations, with overall lower δ15N values at the nearshore station. Amino acid δ15N analyses will provide more information on whether these changes are associated with biogeochemical cycling or food web shifts. Our study provides insight into the effects of anomalous conditions on food web dynamics and the trophic ecology of an abundant zooplankton consumer, which can be used to predict future ecosystem responses to ENSO events.

Authors

Hetherington, E. D., University of California, San Diego, USA, ehetheri@ucsd.edu

Kurle, C. M., University of California, San Diego, ckurle@ucsd.edu

Details

Poster presentation

Session #:059
Date: 03/03/2017
Time: 15:30 - 16:30
Location: Poster/Exhibit Hall

Presentation is given by student: Yes

PosterID: 498