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Oyster reefs have declined globally, impacting ecosystem structure, function, and services. The flat oyster Ostrea angasi was a dominant ecosystem engineer throughout southern Australia, forming extensive reefs now diminished to <1% of historical coverage. Restoration of O. angasi has gained traction over the last decade, exclusively in subtidal habitats. However, O. angasi historically occurred in the intertidal zone, which could broaden restoration opportunities and success. There is little information quantifying factors that influence the performance of O. angasi in intertidal habitats. To test survival of O. angasi under thermal and desiccation stress experienced in intertidal habitats under winter, summer, and heatwave conditions, we emersed individuals from three age classes (1, 4, and 7 months old) at air temperatures of 10, 25, or 40°C in a series of laboratory experiments. Oysters exhibited moderate tolerance to exposure, with survival depending on interactions between emersion duration and temperature, and emersion duration and shell length. Survival broadly increased with shell length, but decreased with temperature and emersion duration. We used model predictions from the laboratory experiments to simulate intertidal survival rates at a potential restoration site in southern Australia. The simulation revealed low survival when low tides coincided with heatwaves. Field validation is needed to understand the effects of repeated tidal cycles and other biotic and abiotic influences. Our findings provide preliminary evidence for extending the restoration range of O. angasi into the low intertidal zone and can be considered when mitigating transport‐related mortality during large‐scale restoration. [ABSTRACT FROM AUTHOR]

Kelp beds are a defining feature of temperate reefs worldwide, playing a fundamental role as ecosystem engineers and primary producers. Overgrazing by the native sea urchin Heliocidaris erythrogramma has driven a phase shift from kelp beds of Ecklonia radiata to barrens across much of Port Phillip Bay, Victoria. Here, we present the results of a transplant experiment, which took juvenile E. radiata sporophytes from a source reef and attached them with silicon tubing to basalt tiles. Following an initial localized cull, we monitored the development and survival of individual E. radiata to investigate the drivers of loss during transplantation, including disturbance (control vs. procedural control), receiving environment (kelp canopy vs. no canopy), and translocation site (within vs. between reefs). We also investigated the role of holdfast reattachment and developmental stage on kelp survival. Sixty‐nine percent of the kelp transplants survived over the 17 weeks, with no increased loss resulting from transplantation to a reef 41 km away. We observed high survival of transplants in the absence of ongoing urchin exclusion. Furthermore, the provision of a canopy is not necessary and may result in adverse impacts on survival and development of juvenile sporophyte transplants presumably through competition for light. Individuals at the collection location (controls) were unlikely to survive to maturity suggesting their removal for transplanting is likely to have minimal impact on the kelp population of the donor reef. The methods used could be feasibly upscaled for rehabilitating or restoring kelp beds both in Port Phillip Bay and elsewhere. [ABSTRACT FROM AUTHOR]