Advancements in Algal Microbiome Research: A Game-Changer for Climate Resilience and Invasion Success?

While marine microbiomes have been getting more attention in recent years, they remain understudied compared to those of terrestrial systems. With the refinement of molecular methods, microbiome research has extended to other key marine organisms such as macroalgae. The microbiome plays a key role in macroalgal health, adaptation to environmental conditions, and resilience to climate stressors. The main factors affecting the algal microbiome are host specificity (genetics, functional profile, phylum and species identity), life stage, morphology, thallus region, and tissue age. Other significant drivers of microbiome community structure include spatiotemporal distribution and environmental conditions, especially as global stressors intensify with climate change. The mechanisms through which the microbiome of invasive seaweeds might enhance their competitiveness over native species are still unclear. However, there is evidence that, like climate resilience, invasive potential is linked to the functional flexibility of associated microbiota, allowing the host to adapt to the new environmental conditions. The main objective of this review was to synthesize the current understanding of the macroalgal microbiome and propose future directions in microbiome research based on identified shortcomings. Based on the knowledge gaps detected, there is an urgent need for multi-factorial experimental studies that link host and microbiome gene expression through chemical signals under future climate change scenarios, standardization of analytical methods, and a focus on underrepresented geographical regions and species. While algal microbiome research holds great promise for predicting and mitigating the effects of climate change and invasive species, embracing new tools and tackling ecologically relevant mechanistic and applied questions will be essential to advancing this field.