Kelp forest decline allows invasive turf algae to spread in NW IberiaInvasion Ecology

Nerea Alvite¹, Sara Barrientos¹, Rodolfo Barreiro¹, Cristina Piñeiro-Corbeira¹

¹Universidad de A Coruña, Spain

Kelps are key foundation species on temperate and Arctic rocky shores, which are experiencing a marked global decline due to climate change, overfishing, or the introduction of invasive species. This study investigates the relationship between kelp forest degradation and the proliferation of the invasive turf-forming red algae, Falkenbergia rufolanosa stadium of Asparagopsis armata, in NW Iberia. Over a period of five years, we conducted seasonal monitoring of eight subtidal rocky reefs to document the loss of golden kelp Laminaria ochroleuca and the spread of F. rufolanosa. Our results show a significantly higher prevalence of the invasive species coverage in degraded reefs where kelp forests are no longer present, while healthy kelp forests exhibit a much lower presence of the invader. These results suggest that kelp forest decline facilitates the spread of F. rufolanosa. Additionally, a marked negative trend in kelp recruitment was observed throughout the study area, indicating potential long-term consequences for kelp forest recovery. The findings highlight the key role of healthy kelp forests in keeping at bay the invasive species and maintaining marine biodiversity. The study underscores the pressing need for effective management strategies to protect and restore kelp forests, emphasizing their importance as ecological barriers against biological invasions in coastal ecosystems.