Carbon capture by stipitate kelp forests in Peru: insights from population assessment of Lessonia trabeculata at 15°S

Marine forests are key providers of ecosystem services globally with increasing recognition of their relevance in the context of climate adaptation and mitigation. Along the Southeast Pacific, these forests sustain productive and intricate trophic webs, serving as crucial sustenance for coastal systems and subsidies for deeper habitats. This study aimed to estimate the contribution of Lessonia trabeculata to the local blue carbon pathways within the southern sector of the largest coastal protected area in Peru, Reserva Nacional San Fernando (RNSF). By integrating remote sensing, scientific diving, and the traditional knowledge of artisanal divers, we conducted a comprehensive assessment and conservative estimates of carbon captured by these forests during the austral winter of 2021 using the least destructive assessment methods. We conservatively estimated ~1300 t C captured as standing stock by L. trabeculata in the southern sector of RNSF. Said biomass-held carbon assimilation would annually release ~1300 t C m² y^-1 as detritus, of which, once exported could potentially yield to ~130 t C m² y^-1 sequestered in deep-sea sediments. Detrital productivity of L. trabeculata was calculated for the first time in Peru, along with the social and environmental cost of emissions equivalent to the amount of carbon captured (855.8k US$) and potentially removed by the standing stock (85.7k US$). In addition, we present an overview of the conservation state of the kelp population in the coastal protected area, along with allometric equations for estimating biomass based on biometric measurements easily attainable underwater. This study represents the continuation of a pioneering effort towards the understanding of blue carbon in marine forests of Peru. Our study contributes to advancing the understanding and management of these ecosystems in the face of climate challenges. The implications for the rapidly growing blue carbon field in the region's socioecological context are further discussed.