Population and community stability in the face of small – scale experimental harvesting in intertidal communities structured by the southern bull kelp, Durvillaea incurvataResistance, Resilience and Phase Shifts

Eliseo Fica-Rojas¹, Daniela N. López², Alejandro Pérez-Matus^3,1, Nelson Valdivia^2,4

¹Millennium Nucleus for Ecology and Conservation of Temperate Mesophotic Reef Ecosystem, Chile - ²Universidad Austral de Chile, Chile - ³Pontificia Universidad Católica de Chile, Chile - ⁴Centro FONDAP de Investigación de Dinámicas de Ecosistemas Marinos de Altas Latitudes, Chile

Ecological stability is fundamental to understanding how natural systems withstand and recover from disturbances while remaining relatively unchanged over time. Stability assessment is particularly relevant when disturbances impact species with a large contribution to the community, such as foundation species, which create complex biogenic habitats and modulate the structure, functioning, and stability of entire communities. Long-lived species such as corals and trees have received significant attention in the context of stability, while comparatively less research has been done on the stability of ecosystems structured by short-lived foundation species. This work aims to determine the ecological stability of two intertidal communities in south-central Chile, structured by the alga Durvillaea incurvata. The study included an experimental pulse removal of D. incurvata individuals in fixed 1 m2 plots, which mimicked a harvesting episode of this species, and a 25-month monitoring period. Recovery was assessed by estimating various dimensions of stability at population and community levels, for both compositional and aggregate aspects of monitored communities. The results indicate a rapid response of D. incurvata populations to the removal, with high resilience and full recovery promoted by continuous recruitment and growth of new individuals. The D. incurvata understory community showed low compositional resistance but high functional resistance. Notably, compositional differences and community biomass returned to reference values within 5 to 7 months, following D. incurvata’s recovery patterns. These findings provide valuable insight into the recovery dynamics of temperate coastal communities and enhance our understanding of ecological stability, highlighting the role of small-scale harvesting strategies, short-lived foundation species and understory population dynamics in maintaining the stability of coastal ecosystem under disturbances.