Heavy metal accumulation characteristics and potential ecological risk assessment of <italic>Enhalus acoroides</italic> beds on the east coast of Hainan Island

To evaluate the environmental quality of Enhalus acoroides seagrass beds in the coastal waters of Hainan Island, based on the survey results of typical distribution areas of E. acoroides seagrass beds in autumn 2022, the contents of heavy metals (Pb, Cr, As, Zn, and Cu) in seawater, sediments, and E. acoroides, as well as the growth characteristics of E. acoroides, were analyzed, and the potential ecological risk index method was used for evaluation. The results showed that the single heavy metal $ {E}_{{r}}^{{i}} $ values of seawater and sediments were all RI rankings of heavy metals in seawater and sediments in different sea areas of seagrass beds were Gaolong Bay > Lian harbor > Longwan bay > Changpi harbor > Xincun harbor; sediment—Changpi harbor > Gaolong bay > Longwan bay > Lian harbor > Xincun harbor, respectively, and both were RI belonged to the low-risk level. Among them, seawater Pb and sediment as accounted for 49.3% and 45.3% of the comprehensive RI, respectively. The enrichment of heavy metals by E. acoroides varied with the types of heavy metals and different tissue parts of seagrass, and the enrichment capacity of aboveground tissues for heavy metals (Pb, Cr, and Cu) was higher than that of belowground tissues.