Intertidal seaweed functional traits across latitude and tidal elevation: A comparison of Pacific and Atlantic shorelinesMacroalgal Traits

Robin Fales ^1,2, John Griffin³, Hannah Hall², Millie Parks³, Joshua Mutter³, Marina Dolbeth⁴, Marta Martins^4,5, Francisco Arenas⁴, Matthew Bracken²

¹Soka University of America, USA - ²University of California Irvine, USA - ³Swansea University, UK - ⁴Centro Interdisciplinar de Investigação Marinha e Ambiental, Portugal - ⁵University of Porto, Portugal

Human impacts and global change are imposing increasing stresses on temperate reef ecosystems. The traits of species in those systems – attributes associated with their performance or fitness – can influence the ability of a community to respond to these stressors. Through a highly collaborative effort between UC Irvine (USA), Swansea University (Wales, UK), and CIIMAR (Portugal), we are linking species traits to marine ecosystem functioning by evaluating seaweed functional traits and associated ecosystem processes across environmental gradients: tidal elevation, region, and latitude (northeast Pacific: northern and southern California, USA; northeast Atlantic: Portugal/southern Spain and Wales, UK). We sampled species and built a trait database encompassing 200+ species across these four regions, including traits associated with structural composition (thallus dry matter content, frond thickness, carbon internal tissue content, and C:N), resource acquisition (mass-specific surface area and surface-area-to-volume ratio), light competition (maximum length and aspect ratio), resource retention (surface area:perimeter, and branching order), and light capture (nitrogen content). Collectively, these results will allow us to evaluate the mechanistic relationships between form and function across environmental gradients, particularly the generality of these relationships across different ocean basins.