Environmental settings of seagrass meadows control rare earth element distribution and transfer from soil to plant compartments

The role of seagrass meadows in the cycling and accumulation of rare earth elements and yttrium (REEY) is unknown. Here, we measured the concentration of REEY in the different compartments of Halodule wrightii (shoots, rhizomes, and roots) and soils in seagrass meadows near sandy beaches, mangroves, and coral reefs in the Todos os Santos Bay, Brazil. We provide data on the accumulation dynamics of REEY in seagrass compartments and demonstrate that plant compartments and soil properties determine accumulation patterns. The ∑REEY in soils were ~1.7-fold higher near coral reefs (93.0 ± 5.61 mg kg⁻¹) than near mangrove sites (53.9 ± 31.5 mg kg⁻¹) and were slightly higher than in sandy beaches (81.7 ± 49.1 mg kg⁻¹). The ∑REEY in seagrasses varied between 35.4 ± 28.1 mg kg⁻¹ near coral reefs to 59.2 ± 21.3 mg kg⁻¹ near sandy beaches, respectively. The ∑REE bioaccumulation factor (BAF) was highest in seagrass roots near sandy beaches (BAF = 0.67 ± 0.48). All values of ∑REE translocation are <1, indicating inefficient translocation of REE from roots to rhizome to shoot. PAAS normalized REE was enriched in light REE (LREE) over heavy REE (HREE). The REEY accumulation in Halodule wrightii revealed a low potential of the seagrass to act as a sink for these elements. However, their bioavailability and potential uptake may change with soil properties. Our results serve as a basis for a better understanding of REE biogeochemical cycling and its fate in the marine environment. REE have experienced increased use as they are central to new technologies revealing an urgent need for further investigations of potential impacts on coastal ecosystems.