Phycoremediation: Use of Algae to Sequester Heavy Metals

Industrialization, natural processes, and urbanization have potentially accelerated the pace and the level of heavy metals (HMs) in soil and underground water. These HMs may be accumulated in plants and animals when they take up such contaminated water, and then make their way into human food chains. Several remediation technologies have been employed to take up HMs. Diverse conventional means such as ion exchange, electrolytic technologies, and chemical extraction have been employed in the past, but the majority of these techniques are not economical for extensive projects and they need stringent control and continuous monitoring. These technologies also have low efficiency for effective removal of HMs. In this context, algae offer an eco-friendly and sustainable alternative for remediation of HMs from polluted water. The accumulation of HMs by macro and microalgae is advantageous for phycoremediation compared to other approaches that are not economical and not environmentally friendly. So, there is an urgent necessity to refine the chances of accumulation of HMs in algae, employing the techniques of genetic engineering to create transgenic species for over-expressing metallothioneins and phytochelatins, which may form complexes with HMs and store them in vacuoles to make the maximum use of phytoaccumulation while also removing hazardous metals from the aquatic habitats. This review outlines the major sources of HMs, their adverse effects on humans, the potential of algae in phytoremediation (called phycoremediation), and their uptake mechanism of HMs.