Diverse stability responses of a sub-Antarctic invertebrate understorey community to experimental giant kelp removal

Abstract

Ecological stability is crucial for understanding anthropogenic biodiversity loss and its consequences, especially when disturbances affect species that influence numerous others. The giant kelp Macrocystis pyrifera, an iconic foundation species, supports diverse communities on temperate and subpolar coasts. While giant kelp communities in temperate regions have been extensively studied, field-based manipulative research in subpolar latitudes is still limited. We investigated the resistance, resilience, and recovery of a community subjected to experimental giant kelp removal in a sub-Antarctic ecosystem. We simulated pulsed kelp loss caused by destructive storms and monitored the macrobenthic invertebrate understorey for 12 mo. The experimental disturbance elicited varying stability responses of the understorey. Understorey community biomass was strongly resistant to the disturbance but declined gradually (i.e. low resilience), showing incomplete recovery compared to undisturbed communities. Community density (total number of individuals per sample) increased notably following the removal (i.e. weak resistance) but ultimately returned to undisturbed levels (i.e. high resilience and complete recovery). Species composition exhibited low resistance and resilience, and no recovery from the disturbance. Secondary coextinctions of several understorey species accounted for the observed low compositional stability. In contrast to giant kelp communities in temperate latitudes, the slower recovery rates of kelp and the loss of key positive interactions likely contributed to the observed stability responses in this subpolar ecosystem’s invertebrate understorey. By examining the response of a sub-Antarctic understorey community to giant kelp removal, our study enhances our understanding of how foundation species sustain local biodiversity.