Oceans and seas host the majority of biomass and global energy cycles as they make up more than half of the Earth’s surface (Mestdagh et al., 2020). Significant changes occur within marine ecosystems due to the difference in the environment caused by warming oceans (Yun, 2022). The seriousness of the matter can be estimated from the fact that in 2018, the concentration of CO2 in Hawaii was recorded to be 409.23 ppm, which is the highest concentration estimated in about the last 3 million years (Gregory, 2021).
One of the main reasons behind the increase in temperature is emission of CO2 in the atmosphere due to exessive use of fossil fuels, resulted in several social, economic, and environmental challenges, which are also severe issues facing today.
There is a need for innovative and sustainable ways of sustainable renewable energy to tackle climate change. The marine ecosystem provides a wide variety of solutions for environmental issues. Microalgae present in different aquatic environments have proved themselves capable of absorbing CO2 from the atmosphere and ultimately reducing its amount from the environment (Peter et al., 2022). This article explores how marine macroalgae can help achieve many of these objectives, including improving aquaculture, reducing CO2 emissions, and resulting in a healthy environment.
“We may have stumbled onto the next green revolution.” ~ Charles H.
WHAT ARE MICRO-ALGAE
Tiny living organisms within the marine environment are called marine microbes, and they are only visible under a microscope. 98% of the total biomass comprises these microorganisms, and they supply the majority of the oxygen to the world. They are also the world’s greenhouse gas processors (AIMS, 2022).
Algae are photosynthetic organisms capable of growing in a wide variety of aquatic habitats like oceans, rivers, ponds, lakes, etc. Algae can also tolerate different conditions, including pH values, salinities, and temperature at a wide range. They can grow alone and in symbiosis with other organisms (Barsanti et al., 2008). According to size, we can classify Algae as microalgae and macroalgae. Macroalgae are large-sized, multicellular organisms that can be seen through the naked eye. On the other hand, microalgae are small-sized, unicellular organisms that can be seen with the help of a microscope (Das, Aziz, and Obbard, 2011).
BENEFITS PROVIDED BY MICRO-ALGAE
Microalgae offer a wide range of applications in cosmetics, medicines, health supplements, and biofuels, among other things (Das, Aziz, and Obbard, 2011). Microalgae have also been shown to be helpful for the treatment of wastewater and the reduction of CO2 emissions from the atmosphere due to these advantages (Brennan and Owende, 2010). Algae photosynthetic carbon sequestration has been identified as having enormous promise in efforts to achieve global or regional carbon neutrality.
As important drivers of crucial biogeochemical cycles in oceans and freshwaters, algae play an important role in CO2 absorption from the atmosphere and the mitigation of global climate change. These activities have a significant relationship with the United Nations SDGs. Using marine macroalgae as a feedstock for biofuels to reduce reliance on fossil fuel combustion as a source of energy, we are investigating how marine macroalgae can assist in achieving some of these goals.
This includes improving aquaculture, contributing to the “Blue Carbon” CO2 drawdown to mitigate climate change, and supplying biomass as feedstock for biofuels. While further research is needed, we believe that growing macroalgae in the air has tremendous potential in terms of cutting CO2 emissions and improving aquaculture production conditions. In addition to promoting biosynthesis and biomass development, the photosynthetic activity of macroalgae can modify pH levels as a consequence of CO2 depletion/HCO3– accumulation.
There is a possibility that this will mitigate the adverse effects of ocean acidification by buffering the pH fall caused by increases in human carbon dioxide emissions. However, despite its growing importance, macroalgal aquaculture now accounts for just a tiny amount of the Cdrawdown generated by wild macroalgae populations and an even smaller portion of world CO2 emissions.
A more substantial contribution to the reduction of human CO2 emissions and ocean acidification may, on the other hand, be made by expanding intensive macroalgal aquaculture in a more significant way. (Gao and Beardall, 2022). Jill Kauffman Johnson, leader and advocate of algae, in a TED talk titled “Beer to Algae; the future of low carbon food systems,” stated that “microalgae, fermentation can be an opportunity for producing food that is more nutritious by utilizing fewer resources while eliminating greenhouse gases. It will protect biodiversity and ecosystem and can be one of the most powerful solutions for addressing climate change.”
MICROALGAE CARBON METABOLISMS
As the principal oxygen-producing photosynthetic microorganisms on the planet, microalgae, commonly called autophototrophs, contribute to over half of the worldwide CO2 fixation. However, it is possible for certain microalgae species to flourish in dark conditions because they have heterotrophic metabolism. Some algae strains can thrive mixotrophically under particular conditions.
Heterotrophic or mixotrophic growth of microalgae is crucial as it enables microalgae to store the organic carbon found in wastewaters, which would otherwise be released in the atmosphere if broken down by bacteria (Zhou et al.,.2017). The types of carbon that microalgae can assimilate, the processes involved in microalgae CO2 capture, and high concentration CO2 stress will all be explored in the following sections.
INTEGRATION OF INORGANIC CARBONS BY AUTO-PHOTOSYNTHESIS
- CARBONS INORGANIC IN THEIR MANY FORMS
A variety of dissolved inorganic carbon (DIC) species, including CO2, H2CO3, HCO3, and CO32, may be taken up by microalgae in the aquatic environment. On the other hand, terrestrial plants have a substantially limited spectrum of DIC assimilation than aquatic plants. The DIC forms are very variable and rely on various factors, including pH, mixing velocity, and microalgae concentration. The DIC forms preferred by different strains of microalgae may be diverse from one another (Hernández-López et al.,2021).
- CO2 ASSIMILATION THROUGH AUTOPHOTOTROPHISM
Microalgal CO2 fixation is converting CO2 and water into organic compounds by using the photosynthetic intermediates ATP and NADPH, which are produced by algae. In the same way, as terrestrial plants do, microalgae acquire CO2 via the Calvin cycle, which consists of three stages: carboxylation, reduction, and regeneration (Zhou et al.,.2017). Overall, the carboxylation stage comprises the incorporation of CO2 into ribulose-1, 5-bisphosphate (RuBP) by ribulose-1, 5-bisphosphate carboxylase (RuBisCo), which results in the synthesis of two molecules of 3-phosphoglycerate (3-PGA) as a result of the reaction (Maity, and Mallick,2022).
Then, with the help of 3-phosphoglycerate kinase and glyceraldehyde phosphate dehydrogenase, 3-PGA is phosphorylated and reduced to generate glyceraldehyde 3-phosphate, which is then phosphorylated and decreased again to form 3-PGA (G-3-P). At the end of the process, RuBP is restored by a sequence of reactions, and the cell is ready to begin the next fixation cycle. In microalgae, CO2 is delivered to RuBisCo by a series of the cell membrane, chloroplast membranes, cell wall, cytoplasm, stroma, and extracellular boundary layer crossings that occur sequentially (Merlo et al.,.2022).
Marine algae and their derivatives are becoming recognized for their potential use in environmental remediation efforts. They offer a variety of biotechnological exploitation as well as usage in industry. Their utilization is beneficial to several biological factors that are thoroughly documented in the scientific literature. They have a significant potential for lowering levels of environmental contaminants.
Microalgae biotechnology is becoming more popular, and it may use to produce a variety of environmentally beneficial products, including biofuels such as biogas, biodiesel, and even bioethanol. The byproducts generated may also be utilized in other industrial operations due to their versatility. Microalgae have the potential to reduce related environmental problems by recycling carbon dioxide from the atmosphere.
Marine microalgae are beneficial in creating biological resources, but they also serve as a generator for the marine environment. They contribute to the movement of energy throughout the ecosystem and also impact the overall productivity of the ecosystem, whether directly or indirectly. They are intimately associated with fishing resources, aquaculture, and geological protection, among other things (Wu et al., 2021).
Extreme weather events induced by climate change are wreaking havoc on people’s livelihoods, while the loss of marine, aquatic, and terrestrial biodiversity exacerbates the problem. The high rate of CO2 in the atmosphere is the primary reason behind global warming today. The best way to reduce CO2 from the atmosphere is by controlling its emission into the atmosphere. But as the world’s population is growing at a very high rate, it is increasing societal demands.
These increased demands are causing a development in industrialization, resulting in raising the rate of CO2 being emitted by different sectors, especially the transportation and energy sectors, into the atmosphere. Therefore, the governments should collaborate with industry partners and scientists to take any action to either limit or tackle these issues. Micro-algae have been proved very beneficial for converting CO2 into valuable biomolecules. As the utilization of microalgae is profitable, sustainable, and feasible at a global level.
- AIMS, 2022. [online] Available at: <https://www.aims.gov.au/docs/research/marine-microbes/microbes/microbes.html#:~:text=Marine%20microbes%20are%20tiny%20organisms,that%20freeload%20along%20with%20them.> [Accessed 27 March 2022].
- Barsanti, L., Coltelli, P., Evangelista, V., Passarelli, V., Frassanito, A., Vesentini, N. and Gualtieri, P., 2008. Low-resolution characterization of the 3D structure of the Euglena gracilis photoreceptor. Biochemical and Biophysical Research Communications, 375(3), pp.471-476.
- Brennan, L. and Owende, P., 2010. Biofuels from microalgae—A review of technologies for biofuels and co-product production, processing, and extractions. Renewable and Sustainable Energy Reviews, 14(2), pp.557-577.
- Das, P., Aziz, S. and Obbard, J., 2011. Two-phase microalgae growth in the open system for enhanced lipid productivity. Renewable energy, 36(9), pp.2524-2528.
- Gao, K. and Beardall, J., 2022. Using macroalgae to address UN Sustainable Development goals through CO<sub>2</sub> remediation and improvement of the aquaculture environment. Applied Phycology, pp.1-8.
- Gregory, R., 2021. Climate disasters, carbon dioxide, and financial fundamentals. The Quarterly Review of Economics and Finance, 79, pp.45-58.
- Hernández-López, I., Valdés, J.R.B., Castellari, M., Aguiló-Aguayo, I., Morillas-España, A., Sánchez-Zurano, A., Acién-Fernández, F.G. and Lafarga, T., 2021. Utilisation of the marine microalgae Nannochloropsis sp. and Tetraselmis sp. as innovative ingredients in the formulation of wheat tortillas. Algal Research, 58, p.102361
- Maity, S. and Mallick, N., 2022. Trends and advances in sustainable bioethanol production by marine microalgae: A critical review. Journal of Cleaner Production, p.131153.
- Merlo, S., GabarrellDurany, X., Pedroso Tonon, A. and Rossi, S., 2021. Marine microalgae contribution to sustainable development. Water, 13(10), p.1373.
- Mestdagh, S., Fang, X., Soetaert, K., Ysebaert, T., Moens, T. and Van Colen, C., 2020. Seasonal variability in ecosystem functioning across estuarine gradients: The role of sediment communities and ecosystem processes. Marine Environmental Research, 162, p.105096.
- Ncdc.noaa.gov. 2020. Global Climate Report – Annual 2020 | National Centers for Environmental Information (NCEI). [online] Available at: <https://www.ncdc.noaa.gov/sotc/global/202013#:~:text=The%20global%20annual%20temperature%20has,2.30%C2%B0F)%20above%20average.> [Accessed 20 March 2022].
- Peter, A., Koyande, A., Chew, K., Ho, S., Chen, W., Chang, J., Krishnamoorthy, R., Banat, F., and Show, P., 2022. Continuous cultivation of microalgae in photobioreactors as a renewable energy source: Current status and future challenges. Renewable and Sustainable Energy Reviews, 154, p.111852.
- Wu, J., Gu, X., Yang, D., Xu, S., Wang, S., Chen, X. and Wang, Z., 2021. Bioactive substances and potentiality of marine microalgae. Food Science & Nutrition, 9(9), pp.5279-5292.
- Yun, M., 2022. Microbial Response to a Rapidly Changing Marine Environment: Global Warming and Ocean Acidification. [online] Frontiers. Available at: <https://www.frontiersin.org/research-topics/13497/microbial-response-to-a-rapidly-changing-marine-environment-global-warming-and-ocean-acidification#authors> [Accessed 27 March 2022].
- Zhou, W., Wang, J., Chen, P., Ji, C., Kang, Q., Lu, B., Li, K., Liu, J. and Ruan, R., 2017. Bio-mitigation of carbon dioxide using microalgal systems: advances and perspectives. Renewable and Sustainable Energy Reviews, 76, pp.1163-1175.
Link to similar posts: https://scientiamag.org/blue-biotechnology-the-secrets-of-the-ocean-are-yet-to-be-explored/
Samra Hayat Khan is a Biotechnologist, currently works in a pharmaceutical company as a research and development officer. Samra is a passionate advocate for marine sciences, their unparalleled benefits for humankind, and their significance for saving mother earth.