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Hot Spots Subject to Qualitative Assessment in the Biodiversity Category
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4.3.5. Hot Spots Subject to Qualitative Assessment in the Biodiversity Category
Hot Spots subject to qualitative assessment using the developed methodology include waste dump sites, degraded territories, numerous military sites, large settlement ponds and/or drained peat quarries. These sites occupy a vast area, and their numerical evaluation is therefore difficult. Instead of applying a scoring technique, these Hot Spots should be described/characterised on the basis of professional knowledge and available criteria. From a biodiversity perspective, these Hot Spots cannot be scored using numerical criteria due to a lack of information on the species composition and biota community functioning in their locations. More or less detailed qualitative information can be found in scientific literature with regard to peat extraction sites.
The Dnipro Basin wetlands (mainly the Pripyat sub-catchment) are located at the intersection of two major bird migration routes: the Big Dnipro Route (the north-south and vice versa) and the Polesye Route (the west-east and vice versa). Therefore the Pripyat Basin wetlands and landscapes, together with marshy floodplains of the Pripyat tributaries, have a global value for biodiversity conservation. Despite large-scale peat extraction and drainage activities, nearly half of the Pripyat wetland area has retained its natural features.
Being rich in food resources, the vast Pripyat wetlands and largest eutrophic European marshes provide food and rest for migratory visitors, exhausted by long travel. Marshes and waterlogged floodplain sections provide resting and nesting grounds for many endangered bird species.
Biological and landscape diversity of the Pripyat Basin has been greatly affected by intensive anthropogenic pressures. The region’s flora and fauna has acquired the features that are characteristic of anthropogenic transformation, with natural habitats of many species being disturbed and degraded, and wetland species diversity reduced and replaced by non-wetland ones. Existing nature reserve/protected area capacity is not adequate to ensure conservation of landscape and biological diversity of the Pripyat Basin, and needs to be expanded, enhanced and integrated into the European ecological network.
Large-scale peat extraction activities cause progressive increase of salinity levels in water, with soluble peat decomposition products entering and polluting surface waters.
The complete degradation of the peat layer in a significant portion (over 1 million ha) of the drained area in the Pripyat Basin poses a serious threat of large-scale climatic and ecological changes in Europe, that can result in deterioration of the regional water balance, degradation of aquatic/wetland ecosystems of European value, and a reduction of biological and landscape diversity.
Anthropogenic pressures have triggered large-scale transformation of the Pripyat Basin wetlands into a vast ‘anthropogenic’ semi-desert area, manifested by outcropping sand lenses. These sand spots grow in size at a rapid rate, and the threat of them joining each other is now real. This implies that local degraded sites are beginning to develop into a larger single semi-desert area.
As a result of large-scale drainage activities, which have affected the balance of wetland, lake and river ecosystems by bringing about new ecosystem types (polders, ponds, inter-dam spaces), the local aquatic communities have changed dramatically, especially in terms of the dominating species composition. It should be noted that this transformation process is now finished for zoo- and phytoplankton communities, while higher aquatic plants and bottom fish communities are still far from stabilisation.
Species composition and distribution patterns have been examined (to greater or lesser extent) only in the locations of nature reserves and protected areas, rather than across the Basin as a whole. Less knowledge and information is available on the aquatic species composition and distribution pattern, being limited to the locations of stationary monitoring sites operated in selected protected areas.
Another group of Hot Spots subject to qualitative assessment/characterisation includes power stations discharging their cooling waters into water bodies. For the purpose of this study, the following major water bodies are to be considered as Hot Spots subject to qualitative assessment/characterisation from the perspective of their impact on the environment and biodiversity:
- Cooling pond of the Khmelnitsk NPP (the Goryn River);
- Cooling pond of the Rivne NPP (the Styr River);
- Cooling pond of the Chernobyl NPP (the Pripyat River);
- Cooling pond of the Zaporizhzhia NPP (the Kakhovka reservoir);
- Cooling pond of the Kurakhovka TPP (the Vovcha River);
- Cooling pond of the Tripolsky TPP (the Kaniv reservoir);
- Cooling pond of the Krivy Rig TPP (the Kakhovka reservoir).
A cooling pond is a quite large body of water, receiving up to 10 million m3/day of water warmed up by 8–120C from a 300 MW station, and therefore has a highly specific flow and temperature regime. Continuous inflow of warm waters leads to a temperature increase in the whole pond, or in sections. Artificial changes in the temperature regime dramatically affect the hydrological, hydrochemical and hydrobiological regime of a water body.
The issue of assessing the complex impact of cooling water discharges on the ecosystem is rather complicated. The severity of impact of elevated temperatures depends not only on the heat capacity of a water body itself and absolute temperature values, but also on the species community structure and sensitivity to temperature changes. All these factors substantially complicate the assessment of temperature effects on certain groups, communities and species.
It should be borne in mind that cooling ponds are used for various purposes and provide water to a broad range of users. This implies that specific water quality requirements of various users should be met, including energy, fisheries, drinking water supply, agriculture and recreation. Water quality is highly responsive to internal processes, taking place in a water bodies and determined by the functioning of aquatic biota communities.
The direct impact of temperature elevations on aquatic biota is often combined with other factors that are able to smoothen this impact. For example, soil erosion can be a decisive factor for benthic communities, or oxygen levels in the bottom layer of water, etc.
Invertebrates. Benthos as an ecosystem component is sensitive to a number of factors, and with regard to a cooling pond, temperature and soil quality are the most important ones. Direct effects of temperature and soil quality, being combined with active accumulation and decomposition of organic matter at the bottom, may cause an oxygen deficit in the deeper water layer. This process is most obviously manifested in the locations of fish-rearing farms and leads to a reduction of species diversity and abundance in the vicinity of cooling water discharges. A higher rate of reduction of benthic population, biomass and species diversity has been recorded in the sections with elevated temperatures, as compared to other sections of a cooling pond. In the cooling ponds of the Kurakhovka and Krivy Rig TPPs, reduced abundance and quantity of invertebrates was also apparent in the central section, suggesting a strong impact of large fish-rearing farms. For example, the distribution of invertebrate communities across the cooling pond of the Kurakhovka TPP is as follows: 4-8 species present in the location of cooling water outfall, 3 species in the central section, and 13 species in the location of water intake. Biomass values vary accordingly: 1.3–7.8 g/m2; 6.5–15.3 g/m2, and 146.7 g/m2. The impact of cooling water discharges on benthic communities grows stronger as the water-surface area reduces.
Macrozoobenthos composition generally remains stable in large cooling ponds, mainly comprising widely spread euribiotic species. Significant shifts can be recorded in smaller cooling ponds due to the elimination of oxiphilic and stenothermic species. In the Dnipro Basin, species communities in the locations of cooling water discharges are usually dominated by Oligohaeta species, tending to shift to Oligohaeta/Hironomida or Hironomida communities nearer a water intake site. In the sections with normal temperature regime (or minimum temperature elevation), macrozoobenthic communities are dominated by Dreissena molluscs.
Higher water temperatures over a winter period stimulate earlier pubescence and reproduction of Oligohaeta species (tibuficide), leading to earlier arrival of the next generation by the end of summer. In the locations of cooling water discharges, pubescence/reproduction period also slightly alters for Hironomida and Dreissena species. Some Pontic-Caspian fauna species tend to flourish in the warmer water of cooling ponds. For example, the cooling pond of the Kurakhovka TPP is now home for the Pontogammarus robustoides species, which is extremely productive at elevated temperatures (by 3–50С), producing a larger number of generations of larger-bodied organisms with higher biomass, as opposed to unheated waters. Many cooling ponds in the Dnipro Basin are now home for Dreissena polymorpha, D. bugensis, Cordilophora caspia and other invertebrate species.
Despite a large number of publications and reports, there is no common agreement with respect to impact of elevated temperatures on zooplankton communities. Some research data and materials are available on issues relating to exposure of organisms to thermal and mechanical stress as they pass through the hydropower turbines. Animal mortality rate depends on a large number of variables such as design features of water supply mains, absolute temperatures and ranges, and size pattern of zooplankton. Larger Crustacea are the most vulnerable species, as opposed to Rotatoria. Mortality rate shows increase at elevated temperature of cooling water (up to 35-400С).
Fish. Warm-water fish rearing farms are widely spread across the Dnipro Basin. Elevated temperatures lead to higher growth and reproduction rates in fish. However, native fish species were found to be very sensitive to higher temperatures, which affect the phenology and timing of lifecycle phases. Earlier time of spawning in the locations of cooling water discharges and further migration of young fish to the lower-temperature sections results in mass kills of fish organisms. Moreover, noticeable losses of fish organisms have been recorded in the locations of pumping stations.
Birds. Warmer waters are favoured by migratory waterfowl that may stay on an ice-free cooling pond for a longer period, and even spend a whole winter on a pond located in the latitude of Kyiv.
Plants. Higher aquatic plants are usually sparse in the locations of cooling water discharges, characterised by a highly modified riparian zone, which is virtually unsuitable for plant development. Available data suggest that generally the species composition and trends in dominating algal communities vary slightly as a result of temperature increase to 30-320C, with heat-loving species emerging in some locations, being characteristic of thermal waters. Cairns (1969) showed that elevated temperatures play a key role in modifying the algal community structure by shifting from diatom algal species to green alga at a water temperature of about 300С, and further shifting to blue-green alga at 35-370С.
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