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
Plant nutrition nutrients a plant may be lacking. Many plants engage in symbiosis with microorganisms. Two important types of these relationship are Though nitrogen is plentiful in the Earth's atmosphere, relatively few plants harbour nitrogen-fixing bacteria, so most plants rely on nitrogen compounds present in the soil to support their growth. These can be supplied by mineralization of soil organic matter or added plant residues, nitrogen fixing bacteria, animal waste, through the breaking of triple bonded N molecules by lightning strikes or through the application of fertilizers. At least 17 elements are known to be essential nutrients for plants. In relatively large