Marine heatwaves facilitate invasive algae takeover as foundational kelp

Abstract

Abstract Extreme warming events have diminished kelp ecosystems around the world, but few reports exist about their impacts on invasive species. Warming events along the coast of Baja California from 2014 to 2016 negatively affected kelp forest communities historically dominated by Macrocystis pyrifera. We measured changes in the macroalgal community at Todos Santos Islands, Baja California, Mexico between 2018 and 2019. Our results documented a dramatic reduction of M. pyrifera, and a concurrent structural shift to invasive kelps dominance, with Sargassum horneri and Undaria pinnatifida being highly abundant in 2019. This study provides insights about impacts of invasive kelp species on macroalgal community structure under future climate scenarios.