Eutrophication may only be made available again during autumn turn-over or in conditions of turbulent flow. Enhanced growth of aquatic vegetation or phytoplankton and algal blooms disrupts normal functioning of the ecosystem, causing a variety of problems such as a lack of oxygen needed for fish and shellfish to survive. The water becomes cloudy, typically coloured a shade of green, yellow, brown, or red. Eutrophication also decreases the value of rivers, lakes and aesthetic enjoyment. Health problems can occur where eutrophic conditions interfere with drinking water treatment. Human activities can accelerate the rate at which nutrients enter ecosystems. Runoff from agriculture
Jellyfish jellyfish are relatively better able to survive in warmer waters. Some jellyfish populations that have shown clear increases in the past few decades are invasive species, newly arrived from other habitats: examples include the Black Sea, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil). Increased nutrients from agricultural or urban runoff with nutrients including nitrogen and phosphorus compounds increase the growth of phytoplankton, causing eutrophication and algal blooms. When the phytoplankton die, they may create dead zones, so called because they are