Water Pollution In Ireland: Eutrophication

Eutrophication is the increase in chemical nutrients in an ecosystem which results in excessive plant growth and decay.

  • Whereas nutrients are a requirement in order for aquatic plants and animals to grow, unnaturally high levels of nutrients cause excessive growth.
  • When the plants die, they are decomposed by micro-organisms including bacteria which consume oxygen dissolved in the water in the process.
  • A large increase in the number of decomposing bacteria leads to a sharp decline in oxygen levels.  Certain fish such as salmon and trout need high levels of dissolved oxygen to survive and so a substantial number of fish kills are caused by eutrophication.
  • In most cases, the primary cause of eutrophication is phosphorus, with nitrates as the secondary cause.  The impact of nitrates is increasing, particularly in coastal waters.

In Ireland many of  our rivers, lakes and coastal waters  are significantly affected by eutrophication.