This project supports the Commonwealth Governments’ $8.1 million investment, administered by the FRDC, in the ‘National Hatchery Network for the commercialisation of seaweed production as a key input into feedstock to help reduce methane emissions.’
Two species of Asparagopsis are native to Australia: temperate A. armata and tropical A. taxiformis. Both produce bioactive compounds (bromoform) and when fed in small amounts to cattle and sheep they reduce methane emissions by up to 98% (Xi et al. 2018, Kinley et al. 2020): supplementing the diet of livestock with a small amount of Asparagopsis is seen as an important way of reducing global methane production (Beauchemin et al. 2022). The ‘tetrasporophyte’ phase of the life cycle is cultured in land-based facilities and considerable effort is focussed on understanding the optimal conditions for growing Asparagopsis to maximise biomass and bromoform productivity per unit culture system.
At present, most publications describing Asparagopsis culture utilise F2 medium or similar solutions including Provasoli Enriched Seawater (PES; Anderson 2005, Mihaila et al. 2023). As a result, most seaweed farmers utilise F2 media, as this is easily available as a pre-mixed, bulk solution. However, these media were designed to culture microalgae and likely do not contain optimal nutrient combinations or concentrations. F2 alone has 14 different constituents, all in varying concentrations, which could be tested and optimised specifically for the growth of Asparagopsis.
The impact of nutrient supply regimes – both macronutrients (nitrogen in different forms i. e. nitrate vs ammonium, and phosphate) and micronutrients (trace elements such as iron, and organic molecules i.e. vitamins, such as B12) – on growth of Asparagopsis tetrasporophytes is unknown. Understanding the interplay between nutrient ratios, uptake rates, and growth outcomes is crucial information for the industry. By potentially removing unused or harmful components from the medium or adjusting supply rates, industry can enhance the cost-effectiveness of large-scale cultivation. The nutrient uptake and usage information gathered in the project will also assist bioremediation and biofilter projects proposed using Asparagopsis (https://www.seaweedalliance.org.au/news/refocused-on-biofiltration).
We will focus initially on A. armata, the most cultivated Asparagopsis species in Australia (Jo Lane pers. comm) with four companies currently growing it: the IMAS team have strong expertise in culturing. A. armata. Following development, the successful growth medium recipe will be shared with ASSA’s tropical A. taxiformis culture facility at James Cook University. Time permitting, we will conduct trials to test whether the new recipe and nutrient supply regime enhances the growth of the tropical species.
References
Andersen, R. A. (Ed.). (2005) Algal culturing techniques. Academic press: New York.
Beauchemin, K.A.; Ungerfeld, E.M.; Abdalla, A.L.; Alvarez, C.; Arndt, C.; Becquet, P.; Benchaar, C.; Berndt, A.; Mauricio, R.M.; McAllister, T.A.; et al. (2022) Invited review: Current enteric methane mitigation options. J. Dairy Sci.105, 9297–9326.
Kinley R.D., G. Martinez-Fernandez, M.K. Matthews, R. de Nys, M. Magnusson, N.W. Tomkins (2020) Mitigating the carbon footprint and improving productivity of ruminant livestock agriculture using a red seaweed, J. Clean. Prod. 259.
Li X., H.C. Norman, R.D. Kinley, M. Laurence, M. Wilmot, H. Bender, R. de Nys, N. Tomkins (2018) Asparagopsis taxiformis decreases enteric methane production from sheep, Anim. Prod. Sci. 58: 681–688.
Mihaila, A.A., Lawton, R.J., Glasson, C.R.K. et al. (2023) Early hatchery protocols for tetrasporogenesis of the antimethanogenic seaweed Asparagopsis armata. J Appl Phycol 35, 2323–2335.
