Out-of-range observations of significant rafts of giant kelp (Macrocystis pyrifera) washing ashore in southern NSW in winter 2020. On 9 August 2020, two local marine naturalists on the south coast of New South Wales, Australia noticed a significant amount of a large unfamiliar kelp washed up on a local beach. Following some quick confirmations via phone and email, it was revealed that the unfamiliar seaweed was giant kelp (Macrocystis pyrifera): a species whose closest known populations are ~450 km away to the south (in Tasmania and western Victoria) and whose transport to New South Wales would have required oceanic rafting over several weeks and hundreds of kilometres against the prevailing south-flowing East Australian Current. Subsequent community-led searches over the following days confirmed four more locations of often-substantial amounts of giant kelp wrack, as well as many more anecdotal and unconfirmed accounts.

This record provides an overview of the scope and research output of NESP Marine Biodiversity Hub project E7 - "Assessing the feasibility of restoring giant kelp beds in eastern Tasmania". For specific data outputs from this project, please see child records associated with this metadata. -------------------- This project will extend an externally funded project conducted through UTAS commencing in 2018 to select for thermally tolerant and low-nutrient-tolerant giant kelp (Macrocystis pyrifera) genotypes, and to examine effects of acclimation of selected genotypes by pre-exposure to warm, nutrient-poor conditions. The proposed project will outplant pre-exposed selected genotypes of giant kelp as micro-sporophytes in an experiment with and without provision of an added source of nutrient. The work is designed to assess the feasibility of this approach as a means to develop minimum patch sizes for giant kelp that can be self-replacing and self-expanding, thus providing restoration and future climate-proofing options for this EPBC-listed marine community. Planned Outputs • Experimental data from macrocystis restoration • Final report

This record provides an overview of the NESP Marine and Coastal Hub bridging study - "Future-proofing restoration & thermal physiology of kelp". For specific data outputs from this project, please see child records associated with this metadata. -------------------- For restoration to be effective, the cause of habitat decline must be understood and overcome. But this is problematic when climate change is driving habitat loss since it cannot be reversed or ameliorated prior to restoration. A previous NESP project led by this team (Project E7, Marine Biodiversity Hub) identified warmwater-tolerant strains of giant kelp from remnant patches in eastern Tasmania, where the species has experienced precipitous declines due to ocean-warming. These strains have high potential to assist with ‘future-proofing’ kelp forest restoration, however it is still unclear what the physiological mechanisms are that provide their improved thermal tolerance. This project is designed to better understand these physiological mechanisms to advance kelp restoration efforts in Australia and globally, and progress toward the identification of populations of Australian kelp that may be resilient to (or especially threatened by) ocean warming and climate change. Outputs • Ecophysiological measurements from laboratory experiments of warm-tolerant vs average giant kelp genotypes [dataset] • Final technical report with analysed data, including a short summary of recommendations for policy makers of key findings [written]

This record described kelp growth and ecophysiological data relevant to the thermal tolerance of specific warm-tolerant and 'normal' family-lines of giant kelp (Macrocystis pyrifera) from Tasmania, Australia. For habitat restoration to be effective, the cause of habitat decline must be understood and overcome. But this is problematic when climate change is driving habitat loss, since it cannot be reversed or ameliorated prior to restoration. A previous NESP project, led by this team, identified warmwater-tolerant strains of giant kelp (Macrocystis pyrifera) from remnant patches in eastern Tasmania, where the species has experienced severe declines over the past half-century due to climate change and ocean-warming. While these strains have high potential to assist with ‘future-proofing’ of kelp forest restoration activities, it is still unclear what the physiological mechanisms are that provide their improved thermal tolerance. Here we cultivated the warm-tolerant giant kelp strains, along with giant kelp strains of normal tolerance, at both cool (16 °C) and warm temperatures (20 °C). We then harvested the juvenile kelp, and examined a suite of physiological traits that may be responsible for their differences in thermal tolerance, including nutrient usage (carbon and nitrogen content), cellular membrane processes (fatty acid contents), and photosynthesis (PAM fluorometry and photosynthetic pigments). The cultivation trials again illustrated the improved ability of the warm-tolerant strains to develop at stressful warm temperatures relative to normal giant kelp. For the first time, we also demonstrate that their improved thermal performance may extend to the development and fertilisation of the earlier kelp ‘gametophyte’ life-stage. Despite the clear differences in growth between the two test groups, the physiological assessments illustrated a complex pattern of responses, some of which are contrary to expected based on prior knowledge of thermal performance in kelps. Nonetheless, our results indicate that the warm-tolerant strains of giant kelp have a greater capacity to alter the composition of their fatty acids and may be more efficient users of nitrogen (a key nutrient for growth and development). This new information will help inform ongoing kelp breeding and selection programs for future-proofing kelp restoration in Australia and globally. This improved understanding of the physiology of kelp thermal tolerance might also help with identifying individuals and populations of Macrocystis, and other kelps, that may be resilient to (or especially threatened by) ocean warming and climate change.