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Human health effects of eutrophication derive from two main issues excess nitrate in drinking water and exposure to toxic algae. [50] Nitrates in drinking water can cause blue baby syndrome in infants and can react with chemicals used to treat water to create disinfection by-products in drinking water. [ 51 ]
The most notable effects of eutrophication are vegetal blooms, sometimes toxic, loss of biodiversity and anoxia, which can lead to the massive death of aquatic organisms. [8] Due to the hypoxic conditions present in dead zones, marine life within these areas tends to be scarce.
It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. [1] Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion.
Gradual environmental changes through eutrophication or global warming can cause major oxic-anoxic regime shifts. Based on model studies this can occur abruptly, with a transition between an oxic state dominated by cyanobacteria , and an anoxic state with sulfate-reducing bacteria and phototrophic sulfur bacteria .
This compounds the effects of eutrophication in coastal zones described above. Open ocean areas with no oxygen have grown more than 1.7 million square miles in the last 50 years, and coastal waters have seen a tenfold increase in low-oxygen areas in the same time.
Phosphates have low toxicity in the environment but cause nutrient pollution, a major water quality problem in many watersheds. [17] Phosphates in water cause eutrophication of algae which creates conditions favorable to formation of harmful algal blooms. These blooms prevent light and oxygen from getting into the water, leading to the death of ...
This effect far exceeds the individual harmful impact of either. [ 135 ] [ 138 ] [ 137 ] In addition, ocean warming exacerbates ocean deoxygenation , which is an additional stressor on marine organisms, by increasing ocean stratification, through density and solubility effects, thus limiting nutrients, [ 139 ] [ 140 ] while at the same time ...
Diffuse source pollution from agricultural fertilizers is more difficult to trace, monitor and control. High nitrate concentrations are found in groundwater and may reach 50 mg/litre (the EU Directive limit). In ditches and river courses, nutrient pollution from fertilizers causes eutrophication. This is worse in winter, after autumn ploughing ...