We evaluated single and interactive effects of density reduction of Zostera marina L., a habitat-forming species, shading, and sediment nutrient enrichment on the response of Z. marina and its associated epifauna over a 10-week experiment during the summer of 2015. Before the experiment was started (Period T0), above-ground eelgrass shoot biomass was evaluated using the shoots collected from 10 cells of 10 x 10 cm while applying the Z. marina density reduction.