Multi-trophic level responses to marine heatwave disturbances in the California Current Ecosystem

Marine heatwaves (MHWs) caused by multiple phenomena with days to months duration are increasingly common disturbances in ocean ecosystems. We investigate the impacts of MHWs on pelagic communities using spatially resolved multi-decade time-series of multiple trophic levels (microbes to fish) from the Southern California Current Ecosystem. We show that most planktonic groups decrease in abundance during marine heatwaves, although results were statistically significant for more phytoplankton groups than zooplankton groups and some taxa (e.g., Prochlorococcus) were more abundant during heatwaves. We also test how marine heatwave characteristics (intensity, duration, and subsurface expression) shape the biotic response. Preliminary results suggest that indices of phytoplankton biomass are generally more sensitive to marine heatwave intensity than duration. In contrast, responses of most zooplankton taxa were not significantly correlated to either intensity or duration, although the total biomass (estimated by zooplankton displacement volume) was somewhat more strongly correlated with MHW duration than intensity. Mobile consumers (forage fish) showed more complex responses, with fish egg abundance declining during MHWs but not correlating with any MHW characteristics. Ongoing work will further explore how plankton communities respond to vertically integrated temperature anomalies, particularly whether these patterns can explain variability in metazoan response to these events.

Presentation Preference: Oral

Primary Presenter: Tz-Chian Chen, Florida State University (tc22@fsu.edu)

Authors:

Tz-Chian Chen, Florida State University  (tc22@fsu.edu)

Mati Kahru, Scripps Institution of Oceanography, University of California San Diego  (mkahru@ucsd.edu)

Michael Landry, Scripps Institution of Oceanography, University of California San Diego  (mlandry@ucsd.edu)

Mark Ohman, Scripps Institution of Oceanography, University of California San Diego  (mohman@ucsd.edu)

Andrew Thompson, NOAA Fisheries, Southwest Fisheries Science Center  (andrew.thompson@noaa.gov)

Michael Stukel, Florida State University  (mstukel@fsu.edu)