Aquaculture water as a source of sustainable growth medium for diatom cultivation and its nutritive suitability as a potential aqua feed

Abstract Diatoms are innately equipped with wide tolerance ability and their cultivation in myriad of effluents as well as aquaculture water represents an emerging, sustainable and effective aquafarming practice which can re-establish circularity in bioeconomy. This study investigates the fate of utilizing mixture of aquaculture water and sea water as a nutrient medium for the growth as well as recovery of value-added products from diatoms. A significant increase in the cell number of Chaetoceros gracilis and Thalassiosira weissflogii, compared to the control groups was observed when grown in the simulated medium. An efficient removal of nutrients like total nitrogen (up to 60%), phosphorous (up to 89%) and reduction of chemical oxygen demand (up to 88%) was also noted in the treatment groups. In addition to this, the extent of accumulation of metabolites like carotenoids, carbohydrates, proteins and phenol was significantly influenced especially under the 30% and 50% aquaculture water and sea water mixed medium for both species. However, the total lipid % DW was reported to be greater than the control groups in the 10% setups. Hence, it can be noted that nutrient rich aquaculture water could not only suffice the survival of the algal strains but also enhance their overall biochemical potential thus alleviating their scope of being utilized as a natural source of feed for the native organisms in the respective aquatic bodies.