Major contraction at warmer edges of the distribution of the cold-water algae Himanthalia elongata (Linnaeus) S.F.Gray 1821

JOANA PEREIRA; CATIA MONTEIRO ; ROCIO NIETO VIELA; FERNANDO LIMA

Brest

Congreso; European phycological congress; 2023

Global warming has been impacting marine ecosystems. Some of the most widespread consequences have been shifts in species distributions. A striking example is the case of the sea spaghetti, Himanthalia elongata, a canopy-forming brown macroalgae with an important structuring role in coastal ecosystems. This species is becoming extinct at its warm distribution edges – a phenomenon often associated with further biodiversity loss. Our objective was to reconstruct the historical changes in the distribution of H. elongata on the Atlantic coast of Europe – an area in which this species was repeatedly surveyed since the 1950s – re-evaluating its current distribution and abundance and correlating distributional changes with remotely sensed and in-situ temperatures collected by a network of autonomous loggers. This algae used to occur from Scandinavia to central Portugal, with a distribution gap in the warmer Bay of Biscay. In the last decades, however, its distribution retreated hundreds of km northwards along the Portuguese coast, and currently, it can only be found in a single location. Additionally, Galician populations have declined, and the distributional gap in the Bay of Biscay has been widening eastwards. Here we will describe some drastic distributional shifts and explore the likelihood of their association with recent warming.