Nonclassical Biomanipulation: PROS and CONS

Abstract

Physical, chemical, and biological techniques can be used to manage eutrophication, a global environmental hazard that might worsen. Biomanipulation is an eco-friendly, cost-effective, and potentially profitable technology for ecological restoration. This review contrasts nonclassical biomanipulation, which uses planktivorous fish to reduce algal blooms, with classical biomanipulation, which employs piscivorous fish to indirectly increase zooplankton populations to manage eutrophication. Owing to certain challenges associated with classical biomanipulation, including the elimination of planktivorous fish, the increase in the number of macrophytes, and the decrease in phosphorus (internal as well as external), preference is given to nonclassical biomanipulation. In tropical lakes with high productivity, where reducing the concentration of nutrients is nearly impossible, nonclassical biomanipulation can also be utilized to control algal blooms. In both lakes and confined water bodies, nonclassical biomanipulation altered the phytoplankton composition at the beginning of the experiment. Using nonclassical biomanipulation, 63% of the 30 studies we reviewed revealed that phytoplankton were successfully controlled. In Lakes Donghu and Qiandaohu, two planktivorous fish, Hypophthalmichthys molitrix and Hypophthalmichthys nobilis nobilis, effectively suppressed Microcystis blooms. However, H. molitrix and H. nobilis are useful for controlling eutrophic environments that do not contain enough macrozooplankton. When large herbivorous zooplankton are unable to effectively suppress nuisance algal blooms, nonclassical biomanipulation has been proven to be an effective strategy; however, it is useless when nanophytoplankton species are blooming organisms. Furthermore, experiments are needed to fully understand the effectiveness of this technique, as environmental parameters such as region and season strongly impact the behavior of water bodies.