International Journal of Aquaculture, 2024, Vol.14, No.3, 165-173 http://www.aquapublisher.com/index.php/ija 170 5.3 Comparative analysis across species A comparative analysis of heavy metal tolerance across freshwater and marine plants reveals distinct and shared strategies. Both Elodea canadensis and Posidonia oceanica exhibit strong antioxidant defenses, highlighting the universal importance of oxidative stress mitigation in heavy metal tolerance. However, freshwater plants like Lemna minor rely more on rapid growth and biomass accumulation to dilute metal concentrations, whereas marine plants like Zostera marina benefit from extensive root systems for metal immobilization. Furthermore, the synthesis of metal-binding peptides such as phytochelatins and metallothioneins is a common strategy observed across species. The efficiency of these peptides in sequestering heavy metals is critical for both freshwater and marine plants. However, the expression levels and types of these peptides may vary, reflecting adaptations to specific environmental conditions. 6 Ecological and Environmental Implications 6.1 Role in phytoremediation Aquatic plants play a crucial role in phytoremediation, a green technology that utilizes plants to remove contaminants from the environment. This method is particularly effective for heavy metal pollution in water bodies. Aquatic plants such as Canadian waterweed (Elodea canadensis), Posidonia oceanica, Eelgrass (Zostera marina) and duckweed (Lemna minor) have shown significant potential in accumulating heavy metals from polluted water, making them ideal candidates for phytoremediation (Souza and Silva, 2019; Ali et al., 2020; Pang et al., 2023). The ability of these plants to absorb and translocate heavy metals from water to their aerial parts enhances their phytoremediation efficiency (Pang et al., 2023). Moreover, the use of macrophytes in phytoremediation is cost-effective, environmentally friendly, and can be implemented on-site, reducing the logistical challenges associated with other remediation methods (Nguyen et al., 2020). 6.2 Impact on ecosystem health The presence of heavy metals in aquatic ecosystems poses a severe threat to biodiversity and ecosystem health. Heavy metals can accumulate in the food chain, leading to toxic effects on aquatic organisms and humans. By employing aquatic plants for phytoremediation, the concentration of heavy metals in water bodies can be significantly reduced, thereby mitigating their harmful effects on the ecosystem. Aquatic macrophytes not only remove heavy metals but also improve water quality by reducing other pollutants, thus enhancing the overall health of the ecosystem (Obinna and Ebere, 2019; Souza and Silva, 2019). The use of aquatic plants in constructed wetlands has proven effective in treating industrial effluents and municipal wastewater, further contributing to ecosystem restoration. 6.3 Interaction with other pollutants Aquatic plants used in phytoremediation can interact with a variety of pollutants, including organic contaminants. The ability of these plants to remove both heavy metals and organic pollutants makes them versatile tools for environmental cleanup (Christian and Beniah, 2019; Obinna and Ebere, 2019). Factors such as water pH, temperature, and the presence of other contaminants can influence the efficiency of pollutant removal by aquatic plants (Li et al., 2015; Christian and Beniah, 2019). For instance, acidic water conditions can enhance the uptake of heavy metals by plants (Li et al., 2015). Additionally, the interaction between heavy metals and organic pollutants can affect the bioavailability and toxicity of these contaminants, necessitating a comprehensive understanding of these interactions for effective phytoremediation (Christian and Beniah, 2019). 7 Challenges and Future Directions 7.1 Technical and methodological challenges The study of heavy metal tolerance in aquatic plants faces several technical and methodological challenges. One significant challenge is the variability in heavy metal concentrations in natural environments, which complicates the standardization of experimental conditions and the reproducibility of results. Additionally, the complex interactions between different heavy metals and plant species require sophisticated analytical techniques to accurately measure and interpret the data. The heterogeneity of contaminated sites also poses a challenge, as it
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