“Understanding anthropogenic pressures on Lake Prespa”

The main goal of the project “Understanding anthropogenic pressures on Lake Prespa” was to determine the water quality of the tributaries of Lake Prespa, the littoral zone of the Lake, as well as two vertical profiles at Kazan and Central Point. The activities required for this are seasonal culminating in heightened research in the summer. Water quality and trophic status are evaluated using physical, chemical, and microbiological parameters from health and ecological perspectives. Agricultural practices in the region are major pollution sources. Total nitrogen and total phosphorus levels indicate the ecosystem’s nutrient load, with ammonia nitrogen also present in the studied areas.

Physical, chemical, and microbiological indicators are crucial for assessing water quality. They act as sensors, detecting pollution in surface water and quickly responding to environmental changes. The results of the microbiological research show organic and faecal pollution of Lake Prespa and its tributaries are in correlation with the physical and chemical results. The rivers are much more polluted than the Lake with the most polluted being the River Golema where a predominance of fresh faecal pollution Escherichia coli was observed indicating as continuous discharge of municipal wastewater. The values ​​for other coliform bacteria as well as enterococci (faecal streptococci) are also maximum.

 Our findings:

 Tributaries rich in pollutants and nutrients, loaded with wastewater from surrounding settlements, greatly burden the coastline in front of their inlets.

• Faecal pollution originates from the discharge of wastewater from unregulated septic tanks, from households, from livestock farms, as well as from the runoff of atmospheric waters. Detailed knowledge of faecal pollution in aquatic environments is of crucial importance for basin management activities, in order to maintain safe waters for recreational and economic purposes.
• A particular danger for the Lake is the anoxic conditions (oxygen-free conditions) identified in the summer period at 15-, 20-, and 25-meters depth. Bacteria consume oxygen to decompose organic matter and, in the event of incomplete mineralisation, they settle on the bottom, which is an additional reason for accelerated eutrophication and siltation of the Lake. The absence of this essential element contributes to the disruption of the natural balance in the ecosystem and leads to visible negative consequences for wildlife.

The findings from the “Identification of Anthropogenic Pressures on Lake Prespa” project offer valuable guidance for the protected area manager to develop and implement effective environmental conservation measures.

It is necessary to control the amount of water from rivers used for irrigation, as this reduces the amount of water feeding the Lake, and to pay close attention to the minimum biological level (important for wildlife). Continuous monitoring of the water quality of Lake Prespa and the rivers in its catchment area is also needed in order to timely signal the existence of certain negative impacts and take measures. Additionally, raising public awareness about the proper use of protective agents (pesticides, fungicides, artificial fertilizers) on agricultural land, the use of water from rivers and the lake for irrigation of the apple orchards that abound in this region is critical.

Our research to date indicates strong anthropogenic pressures and an accelerated process of eutrophication of Lake Prespa. An additional threatening factor to this situation is the frequent fluctuations (changes) in the water level in the lake, or rather the drastic decrease in the water level. This situation negatively affects the entire living world in the lake, which leads to a disruption of the natural balance in this lake ecosystem. In order to prevent further eutrophication processes in Lake Prespa, it is necessary to eliminate existing pollutants and implement appropriate regimes for protection against allochthonous pollution. In order to ensure the best possible water quality in the Lake and its tributaries, constant control is necessary not only of the water but also of the sediment, which is an integral component of every aquatic ecosystem, and is especially important in cases where there are anoxic conditions in the water.

By: Elizabeta Veljanoska Sarafiloska – PSI Hydrobiological Institute