Asparagopsis

The genus Asparagopsis belongs to the Order Bonnemaisoniales, Family Bonnemaisoniaceae. Currently, it comprises of only two taxonomically accepted species based from literatures:

Asparagopsis armata Harvey, 1855

Asparagopsis taxiformis (Delile) Trevisan de Saint-Léon, 1845 (Figure 1)

Other possible species are still under study and debate:

Asparagopsis sanfordiana

Asparagopsis svedelli

This genus, particularly Asparagopsis taxiformis is also a complex species line which composed of six (6) cryptic lineages with different biogeographic distributions.[2]

Figure 2. Developing carposporophyte of A. taxiformis viewed under a microscope.

Like other seaweeds from the Order Bonnemaisoniales, the life history of the genus Asparagopsis is triphasic and heteromorphic meaning an alternation of 2 diploid and 1 haploid stage comprised the whole life cycle. Reproduction begins when the spermatium (male gamete) from the male gametophyte fertilizes the carpogonium (female gamete) of the female gametophyte. This results to a developing zygote that eventually becomes a diploid carposporophyte. The carposporophyte grows along the axes of the female branch and acts as a parasite, absorbing nutrients from the female plant. Seasonal environmental conditions, such as temperature, activates the release of mature carpospores from the cystocarp. Carpospores will settle and germinate to become tetrasporophytes. Eventually, tetrasporophytes will produce tetraspores, usually in sets of four (4), two spore will become the male gametophyte, while the remaining two becomes the female gametophyte. The sex ratio is normally at 50:50. [6]

The species Asparagopsis taxiformis is found throughout the tropical and subtropical regions. While Asparagopsis armata is strictly distributed at the warm temperate region where it clings on other seaweeds using its barbed harpoon branches. A. taxiformis typically grows on solid substrate of rocky-reef areas, from intertidal (wave and tide exposed) to subtidal areas. [7]

The genus Asparagopsis is known to be an important highly invasive species. Both species A. armata and A. taxiformis are included on the list of the “worst invasive alien species threatening biodiversity in Europe and Mediterranean Sea[8].” Asparagopsis armata a native species from Australia and New Zealand has spread its population strictly at the temperate region, particularly in Europe. Due to its invasive capacity, presence of Asparagopsis have an effect on the distribution and abundance of other marine organisms, such as peracarid crustaceans[9]

Assemblage of epifaunal communities in the Mediterrenean Sea shows a decrease diversity and homogenize distribution compare with other associated seaweeds present in the area. The structure of the associated macrofauna: species composition, variability among samples, and relative abundance of the species was also different in a habitat dominated by A. armata and A. taxiformis. This further validates the capacity of genus Asparagopsis to be successful and influential bio-invaders to different habitats. [10]

Figure 3. The filamentous Tetrasporophyte phase of A. taxiformis attached on a rocky reef substrate.

The genus Asparagopsis, particularly, A. taxiformis is highly utilized as feeds for livestocks; Fertilizer; Food for human consumption; and for Medicinal application: antibacterial, antimicrobial, antibiotic, goiter disease among others. [11]

In Hawai'i, dried Asparagopsis taxiformis is consider as a delicacy where it is commonly eaten in poke (fish salad). Preparation of the seaweeds is done by cleaning and soaking overnight in freshwater to remove the bitter iodine taste. [12]

Like all macroalgae, Asparagopsis contains bromoform, a halogen compound which is known to inhibit methane production in ruminants. It has been shown to convert much of the enteric methane (a powerful greenhouse gas) to energy (and some carbon dioxide) for cattle during normal digestion. Because of its high bromoform content, Asparagopsis has proven to be very effective in inhibiting methane production in livestock. Experiments shows that by adding about 20% of seaweed biomass to animal feeds it effectively reduces emissions by 98-99%.[13][14] This could address the increase carbon footprint from the meat industry and mitigate climate issues in the long run.[15]

A collaborative study conducted in Australia by Meat and Livestock Australia, CSIRO and James Cook University, confirmed the effectiveness of Asparagopsis in reducing methane emissions.[16] Emissions were reduced by 80% when Asparagopsis accounted for 3% of the cattle's feed.[17][18]

Several research companies and organizations have already started in looking on the possibility to develop culture technologies for the cultivation and farming of Asparagopsis taxiformis in both land-based and ocean hatchery systems. These are Greener Grazing,[19] Symbrosia,[20] and Blue Ocean Barns.[21]

In 2020 an Asparagopsis-based food supplement FutureFeed won a Food Planet Prize worth $1 million.[22] The importance of the product is as a food supplement.[23]

In Australia, various groups are currently determining its commercial viability, specifically scaling up farmed production of the seaweed and if there are any negative effects (to milk production from feed given to dairy animals or the health of animals, generally) which would prevent its widespread acceptance.