Eutrophication

Eutrophication is a process where a waterbody has an abundance of minerals and nutrients within the water allowing for an algal bloom to occur leading to the loss of oxygen within the waterbody. The excessive concentrations of nutrients such as Nitrogen and Phosphorus within the water allows for the dense growth of algae within the surface water, often leading to ecological damage to the freshwater ecosystems in the affected area. With the decrease in the concentration of dissolved oxygen within the surface water, as a result of the process of algal bloom, lead to hypoxic conditions. These conditions lead to the loss of species of both flora and fauna located within the affected section leading to further environmental and ecological degradation.

Causes

The process of Eutrophication can be classified as either Natural eutrophication or Anthropogenic eutrophication. Natural eutrophication occurs over a timeframe of centuries with the natural build up of nutrients within closed water systems such as lakes with the deposition of sediments and organic material within these systems. As the water systems become more eutrophic the ecosystem can support more organisms as a result of increased nutrient concentrations in the water. This increased concentration does however also support more organisms such as the algae that leads to algal blooms leading to the environmental deterioration.

Anthropogenic eutrophication occurs as a result of anthropogenic activity such as the excessive use of fertilisers in the agricultural sector which enters the surface water as a result of surface runoff. The process of anthropogenic eutrophication can originate from both point, such as pipes used for the discharge of wastewater and illegal discharge of untreated material, and diffuse sources of pollution, such as agricultural fields where runoff from the land enters a fluvial system over a wider area. The artificial increase of nutrients within the surface water as a result of point and diffuse sources exacerbates the slow process of eutrophication allowing for the process to occur within open water systems such as stretches along river systems rather than just closed systems such as lakes and ponds.

The main causes of eutrophication in current systems across the world occur as a result of:

Excess phosphorus in freshwater systems (From Fertilisers)
Excess Nitrogen within water (From Fertilisers)
Untreated sewage (rich in Phosphorus and Nitrogen)

Artificially enriching surface water leading to the major environmental damage associated with surface water.

Impacts

There are many impacts associated within the process of eutrophication that have major impacts on each of the three pillars of sustainability, they being Environment, Economic and Social. The impacts include:

Ecological deterioration
Creation of a hypoxic environment that cannot support a healthy ecosystem
Destruction of food chains
Massive fish kills
Economic loss for the impacted fishing industry
Long term environmental damage with ecosystems require large periods of time to return pre-eutrophic conditions

Mitigation

The mitigation of Eutrophic events is mainly based in managing the loads of nutrients such as phosphorus and nitrogen that enter surface water systems. This is mainly done through improved agricultural practices and improved governance preventing the excessive discharge of these products within surface water systems.

Local scale mitigation can be achieved within agricultural activity with the use of buffer strips of grassland around the border of fields especially adjacent to surface water systems, this intercepts the nutrients that enter surface water through surface runoff reducing the impact of agricultural activity on the wider environment.

Other methods of mitigation of Eutrophication also include the reduction of the availability of nutrients within the system this is possible through the removal of organic material such as the algal blooms, the removal of nutrient sediments as well as the chemical treatment of the affected areas to establish more natural nutrient concentrations within surface water.