Increasingly unpleasant scenes from the coast, especially from the northern Adriatic, such as the recent one in Poreč two days ago, are the result of the process of eutrophication, commonly referred to as “algal blooms”. Eutrophication is the process of enrichment of rivers, lakes, seashores and fish ponds with nutrients, mainly nitrogen and/or phosphorus compounds, leading to a rapid increase in phytoplankton biomass and the appearance of “aquatic blooms”. Eutrophication can be natural or anthropogenic.
Natural eutrophication is a long-term process that can last for centuries. It is a natural part of the ageing of stagnant waters, which gradually fill with sediment. Natural eutrophication is positive for the ecosystem as it leads to an increase in biological resources with few negative effects.
Anthropogenic eutrophication, caused by human activities, is an accelerated process that disturbs the ecological balance and has harmful consequences. It is increasingly occurring as a result of irrational human activities. Many natural and artificial lakes receive water from households and industries, often without any treatment, as well as from landfills and fields over-fertilised with organic and artificial fertilisers. As a result, especially after heavy rainfall, large amounts of phosphorus and nitrogen enter the lakes, which are washed away from the treated fields.
The result is the occurrence of “water blooms” when masses of algae (phytoplankton) develop due to the high nutrient concentrations. This occasionally leads to fish mortality, as the oxidation of nutrients consumes a large amount of oxygen. The situation worsens at high temperatures, when a lower oxygen concentration in the water dissolves. This leads to hypoxia, when the oxygen concentration in the water falls below 1-2 mg/l, or even anoxia, when there is no dissolved oxygen in the water at all. In addition, climate change, such as increasingly frequent droughts and floods, can exacerbate the situation.
It is therefore necessary to tackle the source of the pollution itself, namely to reduce the amount of nutrients entering the water. This can be achieved through the introduction of sustainable agricultural practises, the treatment of wastewater from settlements and industries, the monitoring of water conditions by the relevant authorities and the continuous education of the population.
