Macroalgal blooms caused by marine nutrient changes resulting from human activities

1. Macroalgal blooms (green tides) are occurring more frequently in many regions of the world, leading to significant impacts on marine ecology and economies. Although many studies and hypotheses have been proposed, the exact mechanism of green tide formation remains unclear. 2. The world’s largest green tides recur in the Yellow Sea and this area is representative for studying the origin and mechanism of green tide formation. We conducted a meta-analysis of studies related to green tides and associated hypotheses for their formation. 3. Rapid industrialization/urbanization and environmental protection actions in coastal zones have led to an increase in nitrate (nitrite) and decline in ammonium (ammonia), and this has resulted in increasing levels of dissolved inorganic nitrogen in seawater. 4. We found that presence of appropriate attachment substrates for Ulva including laver culture rafts and certain hydrological conditions are supplementary factors to green tide formation in the Yel...