Potential removal capacity and secondary pollution risk evaluation of heavy metals in Gracilaria lemaneiformis from a typical seaweed farming base

Abstract

Seaweeds are significant primary producers in marine ecosystems and accumulate heavy metals from the environment during growth. However, seaweed litter is produced during the growth and harvest process and has become an important bottleneck that restricts the sustainable development of the seaweed cultivation industry. In this study, we investigated the risk assessment and potential removal of heavy metals in the Gracilaria lemaneiformis cultivation zone in a typical seaweed farming base and evaluated the secondary pollution risk of heavy metals in G. lemaneiformis litter. The results indicated that G. lemaneiformis was a good candidate for the removal and active absorption of heavy metals. A total of 60 thousand tons of harvestable G. lemaneiformis was estimated to remove 242.5 kg copper, 34.5 kg cadmium, 74 kg lead, and 2134.5 kg zinc from a typical seaweed farming base in 2018. Furthermore, the G. lemaneiformis did not pose a health risk to consumers. Variations in the heavy metal accumulation index between dead and fresh G. lemaneiformis litter differed significantly and provided evidence that metals could be either imported or exported from litter to the environment. It is suggested that G. lemaneiformis litter had a potential function in simultaneous heavy metal accumulation and release, and the function of metal accumulation was more effective during growth and decay. The results of this study contribute to the knowledge of heavy metal pollution status and risk assessment in the environment and in G. lemaneiformis, underscoring the strong capacity of heavy metal accumulation in G. lemaneiformis from the environment and the potential heavy metal removal by G. lemaneiformis cultivation and its utilization in a typical seaweed farming base.