Raquel Torres1,2, Ana Campos1,2, Jacob Goldman2, Leonardo Mata1,2, Isabel Barrote2,3, João Silva2
1Greener Grazing, LLC, Greenfield, 01301, MA, USA
2Centre of Marine Sciences (CCMAR), University of Algarve, Campus of Gambelas, 8005-139 Faro, Portugal
3Faculty of Science and Technology, University of Algarve, Campus of Gambelas, 8005‑139 Faro, Portugal
Species of the red seaweed genus Asparagopsis are rich in halogenated bioactive compounds, particularly bromoform. Its use as a feed additive in ruminant livestock drastically decreases the animal’s methane production, thereby reducing the industry’s environmental impact. To address the high demand for Asparagopsis biomass, it is necessary to understand the culture conditions that promote higher growth rates and the concentration of the halogenated compounds. Here we evaluated how light quality and intensity affects the growth and bromoform content of the Asparagopsis taxiformis tetrasporophyte in indoor tumbling cultures at two biomass densities (0.5 and 2 g L-1). We also assessed the effect of light intensity on the photosynthetic response by measuring oxygen evolution rates. We found that a combination of spectra that included intermediate wavelengths (485-630 nm) at a light intensity of at least 90 μmol quanta m-2 s−1 promoted the highest growth rates within the range of conditions tested, regardless of the biomass density. However, the lower saturating irradiances for photosynthesis (65.2 and 53.9 μmol quanta m-2 s−1 at densities of 0.5 and 2 g L-1, respectively) and the development of contamination in the 90 μmol quanta m2 s−1 treatment, suggests that long-term exposure to light intensities above 60 μmol quanta m2 s−1 could be detrimental. Our results also show that managing light intensity (and exposure duration) can be used to promote the bromoform content of A. taxiformis. These results provide valuable information to optimise the production of biomass and bioactive compounds in Asparagopsis indoor tumbling cultures.