Seagrasses as indicators for coastal trace metal pollution: A global meta-analysis serving as a benchmark, and a Caribbean case study

• We present the first benchmark for seagrasses as bioindicators for trace metal pollution.
• Seagrass leaf trace metal concentrations can be used to assess pollution at both global and local scale.
• Seagrass trace metal levels are related to metal pollution due to anthropogenic forcing.

Seagrass beds are highly productive coastal ecosystems providing a large array of ecosystem services including fisheries and carbon sequestration. As seagrasses are known to be highly sensitive to anthropogenic forcing, we evaluated the use of trace metal concentrations in seagrasses as bioindicators for trace metal pollution of coastal regions at both global and local scale. We carried out a meta-analysis based on literature data to provide a global benchmark list for trace metal accumulation in seagrasses, which was lacking in literature. We subsequently carried out a case study at the Caribbean islands of Curaçao and Bonaire to test for local-scale differences in trace metal concentrations in seagrasses, and internal metal allocation. The benchmark and local study show that trace metal concentrations in seagrass leaves, regardless of the species, can vary over a 100–1000-fold range, and are related to the level of anthropogenic pressure, making seagrasses highly valuable indicators.