Marine macrophytes are the foundation of algal forests and seagrass meadows-some of the most productive and diverse coastal marine ecosystems on the planet. These ecosystems provide nursery grounds and food for fish and invertebrates, coastline protection from erosion, carbon sequestration, and nutrient fixation. For marine macrophytes, temperature is generally the most important range limiting factor, and ocean warming is considered the most severe threat among global climate change factors. Ocean warming induced losses of dominant macrophytes along their equatorial range edges, as well as range extensions into polar regions, are predicted and already documented. While adaptive evolution based on genetic change is considered too slow to keep pace with the increasing rate of anthropogenic environmental changes, rapid adaptation may come about through a set of non-genetic mechanisms involving the functional composition of the associated microbiome, as well as epigenetic modification of the genome and its regulatory effect on gene expression and the activity of transposable elements. While research in terrestrial plants demonstrates that the integration of non-genetic mechanisms provide a more holistic picture of a species' evolutionary potential, research in marine systems is lagging behind. Here, we aim to review the potential of marine macrophytes to acclimatize and adapt to major climate change effects via intraspecific variation at the genetic, epigenetic, and microbiome levels. All three levels create phenotypic variation that may either enhance fitness within individuals (plasticity) or be subject to selection and ultimately, adaptation. We review three of the most important phenotypic variations in a climate change context, including physiological variation, variation in propagation success, and in herbivore resistance. Integrating different levels of plasticity, and adaptability into ecological models will allow to obtain a more holistic understanding of trait variation and a realistic assessment of the future performance and distribution of marine macrophytes. Such multi-disciplinary approach that integrates various levels of intraspecific variation, and their effect on phenotypic and physiological variation, is of crucial importance for the effective management and conservation of seagrasses and macroalgae under climate change.
KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors would like to thank to the Fundação para a Ciência e Tecnologia (FCT) for funding the research in the Marine and Environmental Sciences Centre (MARE) throughout the project UID/MAR/04292/2013, the Biosystems and Integrative Sciences Institute (BioISI) throughout the project UID/MULTI/04046/2013, the Centre of Marine Sciences (CCMAR) throughout the project UID/Multi/04326/2013 and the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) throughout the project UID/Multi/04423/2013. BD investigation was supported by FCT throughout a Postdoctoral grant (SFRH/BPD/115162/2016). ES and GP thank the Pew Foundation (USA), the Portuguese FCT through MARFOR (Biodiversa/0004/2015) and a postdoctoral fellowship (SFRH/PBD/107878/2015) to AE. AJ is supported by the Norwegian Research Council (Havkyst project 243916). IM is partially supported by the European Regional Development Fund (ERDF), in the framework of the program PT2020. The authors would also like to thank to the Mar 2020 program through the VALPRAD project (16-01-04-FMP-0007). We acknowledge the two reviewers for their comments and suggestions that helped to improve the structure and quality of this review.