Very often we mention conservation activities as a major part of our work. But what lies behind this concept? Why is it so important?
Conservation or nature protection activities are the implementations of various measures that lead to the restoration, maintenance or improvement of the state of nature and its elements - species habitats, natural habitats or ecological processes. Sometimes these are large-scale technical measures involving the use of heavy machinery and equipment. Other times they are purely administrative - introducing certain regimes, bans or declarations of protection. Often under seemingly simple activities are hidden complex analyses and forecasts, precise planning and coordination. For a conservation activity to be successful, it needs to be planned and executed so that it achieves its objectives and does not harm other species or processes in the ecosystem. Naturally, it takes some time to see the effects of implemented measures, but if they are planned and implemented well - this will inevitably happen.
In Lake Atanasovsko, within the framework of "The Lagoon of Life" project, we are implementing five conservation measures that complement each other and increase the effect on the entire ecosystem. Behind them is a lot of planning and design time, and their implementation requires precise coordination and communication between everyone involved in the implementation - competent authorities, ecologists, technologists, and contractors. And the challenges are many - the constraints of the protected areas and the Natura 2000 zone, the adverse weather conditions, and the different types of machinery and equipment that we use.
In 2022, the "Lagoon of Life" project continues to implement conservation activities with significant progress and success.
- Restoration and maintenance of an optimal water regime in Lake Atanasovsko.
This is the main factor influencing the conditions in the coastal lagoon and it is important that it functions in such a way as to keep the ecosystem healthy on the one hand and to provide conditions for salt harvesting on the other. As part of this work, three large earth dikes are being restored in the North Lake, totalling more than 5 800 m in length. These dikes have been destroyed due to years of non-maintenance and have led to difficulties in the functioning of this entire part of the Lagoon - lack of water circulation, large fluctuations in water levels, mixing of waters with different salinities and deterioration of ecological conditions in the waters. For example - high turbidity, low oxygen content, and problems with sediment settling or resuspension in the waters. With the implementation of these activities, the described adverse effects will be eliminated, and in addition, the flooding of the peripheral parts of the lagoon will be ensured in order to provide good conditions for the other coastal habitats - Mediterranean salt meadows and Salicornia and other annual species. 202 hectares of the priority habitat Coastal Lagoons will be directly impacted and the ecological effect will spread to almost 700 hectares in the North Lake. In addition, a new 7 hectares of favourable nesting area for priority bird species (Avocet, Black-winged stilt, Kentish plover, Little tern etc.) will be provided in the most important part of the Lake Atanasovskoye Sanctuary.
The restoration of dikes is a major tool for the maintenance of Lake Atanasovsko. But for the last 40 years, this has been done mainly by filling in silt from the adjacent pools or repairing certain sections. The dikes have never been completely rebuilt and there is a lack of any technical documentation and experience for this. A technical project was prepared within the project to carry out the restoration, including both the construction technology and the logistical scheme for implementation. This is a great contribution to the future maintenance of Lake Atanasovsko in the implementation of similar measures.
Work is currently underway on two of the three large dikes and more than 1500 m of them have already been restored. Weather permitting, we expect 4000 m to be completed by the end of the year.
The basin before recovery.
Start of restoration works in October 2021.
Recovery is carried out with heavy machinery.
More than 1,500 m of dikes restored before August 2022.
2. Reducing the effects of fragmentation in Lake Atanasovsko
Due to salt extraction, Lake Atanasovsko is divided into a large number of basins by dykes and embankments. The connection between them is made by a series of channels and structures - sluices, spillways, and rafts. Their condition is of utmost importance for the water circulation and migration of nutrients and aquatic organisms between the individual basins, for example, the Caucasian dwarf goby and Artemia salina. The condition of these structures was severely degraded, leading to the almost complete isolation of certain basins and their exclusion from the life of the ecosystem.
Through this activity, 17,000 meters of embankments and mini-dikes and 14,000 meters of internal salt channels in both parts of Lake Atanasovsko and the hydraulic structures connecting the individual basins are being restored. Almost 5.5 hectares of Salicornia habitat and other annual species will also be restored, providing favourable conditions for nesting birds. So far, almost 80% of the planned volumes have been restored and the effects are already visible - the water exchange between the basins has increased by more than 4 times, allowing successful control of circulation and water levels. Water conditions have also improved, especially oxygen content and Chlorophyll A concentration, a sign of decreasing eutrophication.
For the implementation of this activity, we have already tested a new recovery technology - the so-called mini-dykes - in the previous project "Salt of Life". This technology was borrowed from the salt mines in Sečovlje (Slovenia). It is based on replacing, where technologically feasible, existing wooden dikes with mini-dikes - they are an intermediate structure between the large dikes and the 3.2 m wide dikes, they are built quickly and cheaply using a mini bagger and are easy to maintain. This eliminates the use of timber, heavy manual labour and the need for many workers to rebuild, replacing them with just one person - the mini bagger operator.
As part of this work, the North Lake Main Sea Lock, which feeds this part of the lagoon with fresh seawater, was repaired in 2021. This has improved the ability to control the water regime and resulted in greater stability of water levels, salinity and a reduction in sediment re-suspension and associated turbidity of the waters. The effect is visible - in 2022, the natural colony of the Ruppia maritima has recovered in Lake Atanasovsko. This species is strongly affected by erratic water levels and high turbidity and was not observed in the lake after 2019.
Restored mini-dikes in North Lake.
Construction of mini-dikes with a mini bagger.
Cleaned inland saline channels.
The restored natural colony of Ruppia maritima in 2022 after the repair of the North Lake main lock.
The main sluice was restored in 2021.
3. Creation of favourable conditions for nesting of the Great bittern (Botaurus stellaris)
The Great Bittern is a rare heron species that inhabits extensive reed stands with mosaically located ponds in which it hunts and nests. Such habitats are lacking in Lake Atanasovsko and so far the records of this bird nesting here are uncertain. Within the framework of the activity, a variety of freshwater habitats will be created in a 16-hectare area in an extensive reed stand in the northwestern part of Lake Atanasovsko. They will be hydraulically connected to each other and so it will be possible to supply them with fresh water all year round from the nearby river Banska.
0.1 hectares of water-loving trees will also be planted to provide resting and roosting sites, including for other birds that will benefit from this activity - Pygmy and Great Cormorants, Gray and Night Herons, Little Bittern, Glossy ibis, etc.
Implementation of the activity started in August 2022 and so far more than seven interconnected small ponds have been created in the reedbed with a total area of more than 1 hectare.
The excavated soil is used for the construction of the foundations of the large dikes in Lake Atanasovsko. It also provides additional retention volume for the high waters of the Banska River, which will reduce the risk of flooding the lake and compromise our conservation efforts.
The reed massifs before restoration.
The start of restoration works.