El Niño and marine heatwaves: Ecological impacts on Oregon rocky intertidal kelp communities at local to regional scales

El Niños and marine heatwaves are predicted to increase in frequency under greenhouse warming. The impact of climate oscillations like El Niño-Southern Oscillation on coastal environments in the short-term likely mimics those of climate change in the long-term; therefore, El Niños may serve as a short-term proxy for possible long-term ecological responses to an increasingly variable climate. Understanding and prediction of ecosystem responses requires elucidating the mechanisms underlying different organizational scales (organism, space, and time). We analyzed spatiotemporal variation in the effect of the 2015-16 El Niño and the overlapping 2014-2016 East Pacific marine heatwave on three intertidal kelps (Hedophyllum sessile, Egregia menziesii, and Postelsia palmaeformis) at 7 sites across 300 km of the Oregon coast and over three years post El Niño. We measured percent cover, density, maximum length, growth, and Carbon:Nitrogen (C:N) ratios monthly in spring/summer at each site from 20...