First record of <i>Undaria pinnatifida</i> (Laminariales, Phaeophyceae) in beach-cast macroalgae from the southeastern coast of Buenos Aires province, Argentina

Undaria pinnatifida (Harvey) Suringar 1873 is a marine brown macroalga of the order Laminariales, native to northern Asia. This species has an invasive behaviour, currently present on several coasts worldwide, including Argentina. Along the coast of Mar del Plata (Buenos Aires province), sporophytes of U. pinnatifida have been found growing within the local harbour area, but no information is available about its distribution in other coastal areas outside this harbour. In this note, we report for the first time the presence of U. pinnatifida outside the local harbour. The sporophytes appeared in a beach-cast macroalgal accumulation on a sandy beach located more than 15 km south of the local harbour. The data collected from the U. pinnatifida thalli studied (relative wet biomass, size, maturity, and preservation state) suggests that this species may be present in subtidal macroalgal assemblages beyond the harbour limits. It is therefore expected that the occurrence of U. pinnatifida in coastal beach-casts will increase, particularly during summer. The biomass of macroalgae deposited on sandy beaches can be utilized in a wide variety of applications. In this context, the presence of U. pinnatifida in beach-cast accumulations may represent a new, locally available resource, opening additional opportunities for its exploitation in the region.