Abiotic triggers for maximising germling numbers in Asparagopsis taxiformis (Rhodophyta, Bonnemaisoniales) via tetrasporogenesis

• Published in: Journal of applied phycology 2024-12, Vol.36 (6), p.3561-3579
• Main Authors: Theobald, Emma J., Rule, Margaret B., Jackson, Timothy L., Rula, Najeen A., Diaz-Pulido, Guillermo, Jackson, Emma L.
• Format: Article
• Language: English
• Subjects: Arsenic; Arsenic trioxide; Asparagopsis taxiformis; Barrier reefs; Biofilters; Biomedical and Life Sciences; Bioremediation; Cultivation; Dietary supplements; Ecology; Feed supplements; Freshwater & Marine Ecology; Growth rate; Iodides; Irradiance; Life Sciences; Nutrients; Optimization; Photons; Plant Physiology; Plant Sciences; Potassium; Potassium iodide; Potassium iodides; Temperature effects; Temperature requirements; Tetrasporophytes
• ISSN: 0921-8971; 1573-5176
• DOI: 10.1007/s10811-024-03326-7

There is global interest in cultivating the red alga Asparagopsis taxiformis due to its efficacy as a potent anti-methanogenic feed supplement and as a biofilter for the bioremediation of nutrient-enriched waters. However, the development of A. taxiformis cultivation is currently hindered by a lack of information about the conditions required to maximise tetraspore release and thus secure a reliable source of germlings for out-planting. In this study, we examined the effects of temperature, irradiance, and standard nutrient supplementation (F/8, potassium iodide (KI) and arsenic trioxide (As 2 O 3 )) on the number of germlings produced per tetrasporophyte, using a strain of A. taxiformis widespread within the Great Barrier Reef, Australia. Temperature, irradiance and nutrient supplementation played a pivotal role in germling numbers, which was optimised at 22 °C under 7 µmol photons m −2  s −1 and with supplementation of F/8 nutrient media, arsenic trioxide (As 2 O 3 ; 98 µg L −1 ) and potassium iodide (KI; 166 µg L −1 ). Once tetrasporophytes were removed from these inducing conditions, tetrasporogenesis ceased within 12 days. In a further five-week experiment investigating the effect of separate supplementation of As 2 O 3 and KI, germling numbers were maximised under supplementation with either As 2 O 3 or As 2 O 3  + KI, with the relative growth rate of tetrasporophytes maximised under supplementation with F/8 + As 2 O 3  + KI. Under optimum conditions, an average of 3,261 ± 826 (SD) germlings were produced per tetrasporophyte over a five-week period. Our results provide a strong starting point for developing hatchery protocols for generating a reliable supply of germlings for nursery cultivation in tropical settings.