Asexual cultivation techniques of the red macroalgae Asparagopsis taxiformis for commercial application

Shenae Hunter

Asparagopsis is a genus of red macroalgae (seaweed) endemic to coastal waters in Australia and characterised by its complex heteromorphic life history. Previous research discovered Asparagopsis metabolites such as bromoform reduce methanogenesis in livestock rumen by up to 99%. Agriculture accounts for 14% of Australia's total greenhouse gas emissions, predominantly derived from enteric fermentation from ruminant livestock. Cultivating this macroalga is of environmental significance, given the urgency of emission reductions for climate change mitigation while meeting market demand for meat. Understanding manual cultivation techniques is necessary due to limitations of abundance in the wild. There is limited research into cultivation of the asexual lifecycle of Asparagopsis. This research aimed to identify if fragmentation of Asparagopsis is viable, and if growth can be sustained for nearshore cultivation, by mimicking naturally occurring conditions in lab-based cultivation. Light exposure, salinity, temperature, and a lack of nutrients experienced in ocean environments was emulated. Fragments of Asparagopsis taxiformis gametophytes were collected from Perth coastal waters in June and September and cultivated in aquaria at varying temperatures, substrates, and fragment types. Growth rates were overall negatively correlated, with marginal growth in some conditions, concluding that asexual cultivation using these parameters is not recommended. The viability of fragments for up to three months in some conditions gives rise to questions of the potential for asexual cultivation in other environments. The optimum conditions across these aquaria were based around a temperature of 21°C, 25μmol photons m-2 s-1 light exposure and holdfast fragments attached to a substrate such as rope. Of particular significance were tip fragments that retained a dark red pigment, which may provide an ideal setting for continued viability and eventual growth due to the reliance of pigment in photosynthesis processes. Further testing is required to analyse the specific ideal temperature, light exposure and fragmentation origin, alongside other factors such as nutrient levels, to assess if asexual fragmentation is possible for use in commercial cultivation.

Asexual cultivation techniques of the red macroalgae Asparagopsis taxiformis for commercial application

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