Spatiotemporal variability of kelp-like (Saccorhiza polyschides) populations along the Asturias Coast (north of Spain)

Abstract

Once dominant on temperate rocky shores around the world, kelp forests started declining globally during the last century, especially in the last two decades, due to an increasing interaction with anthropogenic-derived stressors (including ocean warming, marine heat waves, fishing and kelp harvesting, pollution and eutrophication). Between early 80s and late 90s, Laminaria hyperborea, Laminaria ochroleuca and Saccorhiza polyschides were three of the most abundant species along the north coast of Spain. However, since the late 90s, the distribution of these three species has significantly shifted onwards the disappearance of both Laminaria species (rarely finding isolated individuals), and the decreasing presence of S. polyschides. Here, we present the results of monitoring 12 transects along the West coast of Asturias over the last 14 years (2009 to 2023). We took different approaches to examine whether two factors, longitude and time, have a significant impact on the distribution of S. polyschides. Results showed a significant gradient of kelp abundance and density from bigger populations on the west coast to eastern locations, even finding local extinctions on two different eastern locations.