Battershill, ChrisElizabeth , Thompson2026-01-292026-01-292026-01-27https://hdl.handle.net/10289/17903Disturbances are recognised as key drivers of ecosystem change, yet there remains limited consensus on how different disturbance types interact, particularly across trophic levels and within subcanopy communities. Existing theories often overlook the nonlinear relationships between climate-driven stressors and species interactions, underscoring the need for system-specific studies to clarify recovery mechanisms. The grounding of the MV Rena on Astrolabe Reef/Otāiti in 2011 resulted in New Zealand’s worst maritime environmental disaster. Fourteen years later, this provides a rare opportunity to assess how legacy disturbance interacts with natural variability to influence subcanopy assemblages. This thesis investigated subcanopy dynamics at two Bay of Plenty locations: Astrolabe Reef, directly impacted by the MV Rena wreck, and Motiti Island, a nearby reef indirectly affected by the wreck, but directly affected by Cyclone Gabrielle, and both systems subject to fishing pressure, sedimentation, and other stressors. Biodiversity surveys, species inventories and Baited Remote Underwater Videos, were combined with manipulative clearance experiments to test environmental responses. At Astrolabe Reef, small-scale clearances were established in high and low impact zones, while at Motiti Island, large canopy removals in Carpophyllum spp and Ecklonia radiata transition zones simulated storm-driven disturbance. Quantitative assessments after eleven weeks of the clearances revealed rapid recolonisation but divergent trajectories. At Astrolabe Reef, sites nearer the wreck were dominated by turfing algae and urchins (Centrostephanus rodgersii), while more distant sites supported greater sponge richness and habitat heterogeneity. At Motiti Island, opportunists such as kina (Evechinus chloroticus) and turfing algae shifted into available space. Carpophyllum spp. recovered strongly and expanded downslope, contrasting with the weak recovery of Ecklonia radiata. These findings demonstrate that outward canopy recovery can mask deeper structural shifts in subcanopy communities. More broadly, they highlight how legacy disturbance, grazer dynamics, and climate-driven pressures interact to shape resilience pathways in temperate reefs.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis