Between 1984 and 2001, the delta lost 277 km2 (107 sq mi) of wetlands, or an average of approximately 16 km2 (6.2 sq mi) per year, from natural and human-induced causes. The Volga discharges large amounts of industrial waste and sediment into the relatively shallow northern part of the Caspian Sea. The added fertilizers nourish the algal blooms that grow on the surface of the sea, allowing them to grow larger.