*3.2.2.2 Eutrophy*

In eutrophic conditions, the situation becomes more complex. In this case, the water contains an abundance of nutrients, which fuels high levels of biological activity. As a result, light is absorbed on the surface of the water and does not reach the depths, resulting in cloudy water. Oxygen levels in the water are very low, and deposited organic materials decompose through anaerobic processes, further contributing to eutrophication. The lack of oxygen in these waters also makes them


#### **Table 2.**

*Proposed classification system for the status of the Nuremberg trophy.*

uninhabitable for fish, which often die off. Nutrient enrichment is the main factor responsible for the degradation of surface water quality, causing intense growth of algae, which can reduce activities related to fisheries, recreation, and industry.

Algae grow rapidly in eutrophic waters and form a layer on the surface that can lead to a reduction in dissolved oxygen levels, increased suspended solids, and a decrease in the diversity of aquatic species. Strong growth of cyanobacteria, in particular, can occur in these waters, causing health problems for humans and livestock if these waters are used. The growth of algae can also release toxic and volatile substances, causing nerve damage and raising concerns about the phenomenon of nutrient enrichment. While nitrogen and carbon are also essential for the growth of aquatic organisms, controlling their levels is difficult due to the atmospheric and water cycles of these elements. However, phosphorus has been identified as the most limiting element for the growth of aquatic organisms, as evidenced by numerous studies (**Figure 4**).
