Carbon Sequestration Potential of Marine Microalgae

Marine ecosystems occupies the largest proportion in the Earth which is nearly 75% of the total area. It plays an important in the climate change. Like anyother ecosystems, the marine ecosystem also affected by global warming may be due to anthropogenic activities and increase in the concentration of atmospheric carbon dioxide. The ocean productivity also decreased by the impact of anthropogenic activities induced climate change. It altered the food web dynamics, reduced abundance of habitat-forming species, shifting species distributions [1]. High content of CO2 in the atmosphere trigger the global warming and consequent climate shift which is the hazards for the sustainability of life on the earth. Different technology followed by CO2 capture, but the biological methods still challenging technology due to low amount of biomass yield, high contamination, cost of maintenance, repair cost of fermentor and extraction of biomaterial is the major concern [2].


Introduction
Marine ecosystems occupies the largest proportion in the Earth which is nearly 75% of the total area. It plays an important in the climate change. Like anyother ecosystems, the marine ecosystem also affected by global warming may be due to anthropogenic activities and increase in the concentration of atmospheric carbon dioxide. The ocean productivity also decreased by the impact of anthropogenic activities induced climate change. It altered the food web dynamics, reduced abundance of habitat-forming species, shifting species distributions [1]. High content of CO 2 in the atmosphere trigger the global warming and consequent climate shift which is the hazards for the sustainability of life on the earth. Different technology followed by CO 2 capture, but the biological methods still challenging technology due to low amount of biomass yield, high contamination, cost of maintenance, repair cost of fermentor and extraction of biomaterial is the major concern [2].
Microalgae is also one of the important microbial communities which are simple photosynthetic unicellular organisms. They can be either prokaryotes (cyanobacteria) or eukaryotes that can grow and live in harsh conditions because of its simple structure [3]. Carbon dioxide capture by marine microalgae is an important strategy to reduce temperature in the atmosphere. It is a pressing challenge for the humanity to to reduce gaseous emissions and their consequential climatic changes, greenhouse and global warming effects. The current level of CO 2 in atmosphere is approximately 280 parts per million (ppm) to 400ppm [4] The CO 2 is essential for growth of microalgae , and the lifetime of CO 2 is 50 to 200 years [5]. The CO 2 is contributing approximately 52% in total global warming [6]. Different microalgae have been studied for carbon dioxide fixation, among them Chlorella vulgaris received chief attention, which can tolerate high concentrations of CO 2 , and high photosynthetic capacity. This microalgae can maintain high growth rate and CO 2 fixation rate in a wide range of CO 2 concentrations from 0.04 to 18% (v/v), can be considered as a good species to fix CO 2 [7].
There are many studies reported on the microalgal based CO 2 bio-mitigation, but there is lacking of literature review on the latest technologies on microalgal cultivation, which is mainly towards successful CO 2 bio-sequestration of atmospheric CO 2 and flue gascontaining CO 2 . This opinion paper aims to summarize and discuss about the CO 2 bioconversion efficiency of microalgae species and the potential and future challenges of carbon capture.

Capturing CO 2 By Marine Microalgae
Microalgae can have the capability of to Dissolve Inorganic Carbon (DIC) from the aquatic environment in forms of CO 2 , H 2 CO 3 , HCO 3 , and CO. By contrast, terrestrial plants are much less diversified in the DIC assimilation [8]. The CO 2 captured by photosynthesis and converted into organic compounds powered by ATP and NADPH [9]. There are several photobioreactors used to cultivate the microalgae and the photobioreactor should be designed with specific parameters like carbon and nutrient level, light intensity, light/dark cycle, temperature, and pH. Some microalgae species Oceanography & Fisheries Open access Journal possess heterotrophic metabolism and are able to grow in dark environments. The ability of microalgae to grow heterotrophically or mixotrophically is significant and important because this allows microalgae to sequester organic carbons present in waste waters, which can eventually emit to the atmosphere if broken down by bacteria [10]. The marine microalgae have the ability to convert almost 80% carbon dioxide into oxygen. The microalgae may be the better choice due to their small size and have high growth rate compared to other plant and also absorbs more CO 2 in a short time. It has the potential to reduce the toxicity of the water and utilize it as a nutrient factor for growth.

Conclusion
Microalgae are fast-growing microorganism with relatively high CO 2 biofixation rate compared to terrestrial plants. They provide so many co-products and renewable energy production. The CO 2 sequestration can be achieved towards environmental sustainability and economic feasibility. Microalgal-based CO 2 bio-sequestration is an innovative technology to bring significant advancement in CO 2 bio-mitigation aiming towards a global warming solution. In future multidisciplinary approach involving chemists, engineers and biologists would be beneficial for greater purposes.

Conflict of Interest
We declare that we have no conflict of interest.