Abundance and Distribution of Native and Exotic Kelp Forests in Patagonia (South West Atlantic, Argentina)Invasion Ecology

Natalia Aga Milovic^{1, 2}, Maria Paula Raffo³

¹University of Valparaíso, Chile - ²Marea Sintiente Foundation, Argentina - ³Patagonian National Center, Argentina

Kelp environments are recognized as biodiverse and productive marine ecosystems that capture carbon and preserve biodiversity. In the southwestern Atlantic, data remain scarce and outdated. This study aimed to assess the distribution and abundance of native kelps Macrocystis pyrifera and Lessonia spp., as well as the introduced kelp Undaria pinnatifida, within two National Parks (NP) in Santa Cruz Province: Isla Pingüino Interjurisdictional Marine Park (PIMIP) and Monte León National Park (PNML). Subtidal transects parallel to the coast were conducted in March and October 2023 (N=18, PIMIP; N=3, PNML), and individuals by species and life stage (juvenile and adult) were recorded along with audiovisual material. In PIMIP, M. pyrifera, Lessonia spp., and U. pinnatifida shared an ecological niche (Total N=1144). M. pyrifera was most abundant (N=512; adults: N=400, juveniles: N=112), followed by U. pinnatifida (N=401; adults: N=295, juveniles: N=106), with Lessonia spp. less frequent (N=231 adults). U. pinnatifida was recorded here for the first time, suggesting its establishment and expansion. In PNML, M. pyrifera and Lessonia spp. were recorded (Total N=177; transects N=3), with Lessonia spp. more abundant (N=156 adults), likely due to wave action, while the low density of M. pyrifera may reflect sampling location. These findings underscore the need for further research on forest dynamics and the ecological impact of U. pinnatifida in PIMIP. Educational materials produced offer valuable resources for local communities, tourism, and education, illustrating how scientific and educational initiatives can improve conservation outcomes.