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 microalgal epiphyte load on eelgrass leaves. We estimated the epiphyte (microalgae) load on eelgrass by scraping eelgrass leaves with a microscope slide under filtered seawater. During Period T1, we selected and scraped the leaves of three randomly selected shoots. We then filtered the water containing the scraped epiphytes through preweighed GF/F filters, and we assessed the epiphyte load as the dry weight of epiphytes divided by the dry weight of the collected scraped shoots.