Warming seas: Native Sargassum species at risk

Sargassum species play a critical role in tropical and temperate coastal ecosystems by contributing to primary production and providing habitat to different species, while causing ecological disruptions and social challenges in some localities. As global warming intensifies, understanding how Sargassum species respond to rising seawater temperatures becomes increasingly important, and synthesizing evidence across diverse research approaches is critical to this goal. This study combines a comprehensive review and meta-analysis to evaluate the effects of warming on native and invasive Sargassum species in tropical and temperate regions. A total of 1471 studies were screened, of which 175 met the inclusion criteria and addressed Sargassum responses across tropical, warm-temperate, and cold-temperate regions. Our findings revealed that benthic native species are particularly vulnerable, with reduced growth rates and photosynthetic efficiency under projected warming scenarios in tropical and warm-temperate regions. In contrast, invasive species showed positive or neutral outcomes. Long-term monitoring and species distribution modeling studies supported these results, predicting significant habitat contractions and population declines for native species, while the invasive Sargassum muticum exhibited expanded ranges under future warming scenarios. These shifts could exacerbate ecological and social challenges, with cascading effects that compromise the functioning of ecosystems. Our study underscores the urgent need for monitoring programs and management strategies targeting Sargassum populations.