Assessment of the ameliorating effect of sedimentary iron inputs on sulfide stress in eelgrass beds

Iron is recognized as an efficient method to alleviate sulfide stress. This study tested the response of Zostera marina plants to different levels of sedimentary sulfides (100.0-818.7 μmol L^-1) and iron inputs (590.0-825.3 μg L^-1) in a field experiment performed over an eighty-day period. We measured plant responses in terms of shoot density and plant morphology and productivity. The relationship between the propagation effort (PE, in %) and sulfide content (S, in μmol L^-1) was expressed as: PE = -14.01 × ln (S) + 86.86 (R² = 0.99, p < .01), which indicates that the toxic limit of the pore-water sulfide concentration for the survival of eelgrass is 493 μmol L^-1. The addition of iron can reduce the toxicity of sulfides to eelgrass beds, resulting in an increase in plant density and productivity, and can even reverse the decline of eelgrass beds exposed to high sulfide concentrations.