BOTANY WITH THE BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

XI. HABITATS OF AQUATIC MACROPHYTES AND DISTRIBUTION OF THEIR PLANT COMMUNITIES IN UKRAINE

Aquatic plants occur in the shallows of riverbeds, bays, and branches, inter-estuary watercourses, and streams. They are typically widespread in Water bodies with negligible or absent current, such as lakes, oxbows, marshes, estuaries, and coastal shallows of seas. They are also characteristic of artificial water bodies, including irrigation canals, ponds, and reservoirs, as well as areas subject to groundwater and surface waterlogging.

Rivers. Ukraine (territory of 603.7 thousand km²) counts about 71 thousand rivers with a total length of 243 thousand km. Of these, 160 rivers exceed 100 km in length, and about 4 thousand are longer than 10 km. The rest have channels not exceeding 10 km in length. Most Ukrainian rivers belong to the Black Sea and Sea of Azov basins, while 2.5 thousand rivers drain into the Baltic Sea basin. Nearly half of them (30 thousand rivers) empty into the Dnieper, 11 thousand into the Dniester, and the rest into the Danube, Southern Bug, Seversky Donets, and other smaller rivers [102].

The river network density exceeds 0.1 km/km², decreasing across the flatland territory from northwest to southeast.

A higher river network density is characteristic of Polissia (0.18-0.23 km/km²), whereas it is lower in the Forest-Steppe (0.17-0.20 km/km²) and even lower in the Steppe (0.05-0.1 km/km²). In the Carpathians, it reaches its maximum at 0.5-1 km/km².

Major rivers of Ukraine include the Dnieper (which receives waters from about 30 thousand rivers), the Danube, the Dniester, the Southern Bug, the Pripyat, the Desna, and the Seversky Donets; medium-sized rivers include the Sula, Vorskla, Psel, Ros, Syniukha, Samara, and Orel, among others. Rivers of dissected plains are the most common in Ukraine. They feature wide valleys with gentle slopes, a valley gradient exceeding 10 cm/km, and a current velocity of 0.2-0.3 m/s. Some small rivers of this type flowing through the Steppe may dry up during the summer period.

Polissia rivers feature an even gentler gradient (up to 10 cm/km). They have wide valleys, a significant portion of which is waterlogged.

Mountain rivers (of the Carpathians and Crimea) are characterized by narrow valleys and steep slopes. Their channels are shallow, with a width ranging from 10-20 cm in the upper reaches to 80-100 m in the lower reaches. The gradients are 60-70 m/km and 5-10 m/km, respectively.

Almost all rivers experience spring floods, followed by summer low-water periods with occasional flash floods. Water levels drop even further in winter. Ice cover forms in December and lasts for 2-3.5 months.

Ukrainian rivers transport a substantial mass of suspended silt. The highest turbidity is observed in rivers of the Steppe (250-500 g/m³) and Forest-Steppe (200-300 g/m³) zones.

High water turbidity is also noted in rivers of the Carpathians (300-500 g/m³) and Crimea — originating from areas subject to active erosion processes (300-500 g/m³). Rivers of Polissia have the lowest turbidity (up to 50 g/m³).

A low degree of mineralization characterizes the waters of Carpathian rivers (100-200 mg/L) and Polissia rivers (200-500 mg/L). High water mineralization is typical for rivers in the Donbas basin and the southwestern regions of Ukraine.

The channels of small rivers generally range from 1-2 to 10-20 (30) m in width and are often completely overgrown with aquatic vegetation (Polissia, Forest-Steppe). In Polissia, they have an average depth of 50-150 (200) cm. The bottom is trough-shaped, sandy or silty-sandy, with a water pH of 6.0-8.0. Aquatic plants form belts of varying widths, depending on the bottom slope, current velocity, and water depth. The coastal zone hosts plant communities of *Glycerietum maximae*, *Sparganio-Glycerietum fluitantis* (Polissia, Forest-Steppe), *Phragmitetum communis*, and *Scirpetum lacustris* (Forest-Steppe, Steppe). In areas with continuous flooding and flowing water, sparse communities of *Nupharo lutei-Nymphaeetum albae*, *Potametum obtusifolii* (Polissia), *Potametum perfoliati*, *Myriophyllo-Potametum* (Polissia, Forest-Steppe), *Elodeetum canadensis*, and *Myriophylletum verticillati* (Forest-Steppe, Steppe) occur. In shallows with a slower current and sandy bottom sediments, communities of *Batrachio trichophylli-Callitrichetum cophocarpae* and *Ranunculo-Cardaminetum parviflorae* develop (Forest-Steppe, Polissia). In the Steppe zone, due to anthropogenic eutrophication, these areas typically remain free of vegetation. In deeper areas (100-150 cm) with permanent flooding and silty bottom sediments in Polissia, communities of *Potameto natantis-Nymphaeetum candidae*, *Stratiotetum aloidis*, and *Hydrocharitetum morsus-ranae* are frequently found. In the Forest-Steppe and Steppe, such habitats are dominated by *Ceratophylletum demersi*, *Potametum pectinati*, and others. In shallows where the current velocity is higher (0.3-0.6 m/s), coastal belts are usually non-overgrown, though single-species communities of *Potametum perfoliati*, *Potametum pectinati*, and *Myriophylletum verticillati* (Steppe) occasionally occur in the channel as isolated patches stretched along the current.

The channels of medium and large rivers become overgrown only along their margins. In areas with a slow current and gently sloping bottom, belts of helophytic and aquatic vegetation develop, including *Typhetum angustifoliae*, *Glycerietum maximae*, *Acoretum calami*, *Bolboschoenetum maritimi continentale*, as well as true aquatic communities of *Potametum perfoliati*, *Potametum pectinati*, and *Myriophylletum verticillati*. In areas with a steeper bottom, a belt of emergent macrophytes typically does not form. It is also absent where the current velocity exceeds 0.5 m/s. True aquatic plants are represented by sparse communities of *Potamogeton perfoliatus*, *Myriophyllum spicatum*, and *Nuphar lutea* (submerged form).

Aquatic macrophytes are most characteristic of bays, river branches, oxbows, and inter-estuary watercourses. Bays, much like small river channels, are extremely prone to overgrowing with aquatic plant communities. They lack significant current in their main parts, with stronger flow occurring only in areas adjacent to the main riverbed. The size of the bays ranges from several hundred square meters to 1-2 hectares. The bottom is flat and gentle, sloping toward the riverbed, with sandy, silty-sandy, and silty bottom sediments. The depth of the bays varies from 50-70 to 150-250 (300) cm, with a water pH of 6.0-8.0. Aquatic macrophytes form vegetation belts in the coastal zone and areas bordering the main channel, while forming mosaic patches elsewhere.

Characteristic plant communities of the shoreline strips include *Glycerietum maximae*, *Sparganio-Glycerietum fluitantis* (Polissia), *Phragmitetum australis*, *Typhetum angustifoliae*, and *Caricetum acutiformis* (Forest-Steppe, Steppe). Communities of *Sagittario-Sparganietum emersi*, *Sparganietum erecti*, and *Bolboschoenetum maritimi continentale* (all zones) are frequently observed. In contact zones between bays and river channels, *Potametum graminei*, *Potametum perfoliati*, *Myriophylletum verticillati*, *Potametum pectinati*, and *Nupharo lutei-Nymphaeetum albae* commonly occur. Patches are more frequently formed by *Scirpetum lacustris*, *Potametum natantis*, *Nupharo lutei-Nymphaeetum albae*, and *Polygonetum amphibii*. Rare communities of *Nymphoidetum peltatae* occur on alluvial sites, whereas *Trapetum natantis* and *Potameto natantis-Nymphaeetum candidae* (Polissia, Forest-Steppe) inhabit waterlogged sites. In wetland habitats, *Stratiotetum aloidis*, *Potametum lucentis*, and *Hydrocharitetum morsus-ranae* are widespread.

River branches are usually overgrown with aquatic macrophytes only in their coastal parts. The width of these branches ranges from 3-5 to several tens of meters. The bottom is trough-shaped, gentle, with sandy and silty-sandy bottom sediments. The depth varies from 100-200 to 500-700 cm, with a water pH of 6.0-8.0. The current is generally slow. Aquatic plants are arranged in belts, or less frequently as belt-like patches or patch-forming communities. In coastal shallows and along the shoreline, *Glycerietum maximae*, *Sparganio-Glycerietum fluitantis* (Polissia, Forest-Steppe), *Bolboschoenetum maritimi continentale*, *Glycerietum plicatae*, and *Acoretum calami* (Forest-Steppe, Steppe) are most common. *Phragmitetum australis*, *Typhetum angustifoliae*, and *Scirpetum lacustris* are widely distributed in other ecotopes. In deeper areas (up to 150-200 cm), *Myriophylletum verticillati*, *Nymphaeetum albo-luteae*, *Potametum natanto-lucentis*, and *Potametum pectinati* are common, while *Trapetum natantis* is less frequent.

Oxbow lakes, which unlike river branches are only temporarily connected to the main channel, feature more densely overgrown water areas, and only rarely is their central part free of aquatic macrophytes. The width of oxbows ranges from 20-30 to 200 (500) m, and their length reaches several kilometers. The average depth is 50-150 (200) cm, rarely 10-12 m, with a water pH of 6.0-8.0. Aquatic macrophyte communities form belts in the coastal zone and patches across the open water. The belts are dominated by *Phragmitetum communis*, *Typhetum angustifoliae*, and *Typhetum latifoliae*, whereas deeper sites are inhabited by *Ceratophylletum demersi* and *Elodeetum canadensis*. The patches most frequently comprise *Scirpetum lacustris*, *Potametum lucentis*, *Potametum crispi*, *Potameto natantis-Nymphaeetum candidae* (Polissia, Forest-Steppe), and *Nupharo lutei-Nymphaeetum albae*.

Inter-estuary watercourses, typical of lowland deltaic rivers, are characterized by aquatic macrophyte communities forming belts in the coastal zone. *Potametum perfoliati* and *Potametum pectinati* are most common, while *Elodeetum canadensis* and *Ceratophylletum demersi* are less frequent. Deeper areas support communities of *Nupharo lutei-Nymphaeetum albae*. Fading watercourses are distinguished by denser plant communities that frequently occupy the central part of their bed as well.

The coastal strip develops communities of *Thelypteridi-Phragmitetum*, followed toward greater depths by *Sparganietum erecti* and *Sagittario-Sparganietum emersi*. Central areas are occupied by *Elodeetum canadensis*, *Myriophylletum verticillati*, *Ceratophylletum demersi*, *Nupharo lutei-Nymphaeetum albae*, and others.

Near streams and groundwater discharge zones, plant communities develop comprising common reed (*Phragmites australis*), creeping bentgrass (*Agrostis stolonifera*), greater water-parsnip (*Sium latifolium*), nodding beggarticks (*Bidens cernua*), sea club-rush (*Bolboschoenus maritimus*), narrowleaf cattail (*Typha angustifolia*), broadleaf cattail (*Typha latifolia*), flowering rush (*Butomus umbellatus*), and European water-plantain (*Alisma plantago-aquatica*).

Lakes. Ukraine counts over 3 thousand lakes with a total surface area of about 2 thousand km². Of these, only about 40 lakes have a water surface area exceeding 10 km². Floodplain lakes are the most common, though distributed unevenness across Ukraine. Most of them are located in the river valleys of the Dnieper, Pripyat, Desna, Samara, Sula, and Khorol. Polissia rivers contain a particularly large number of floodplain lakes.

Non-floodplain lakes of ancient valley systems — such as karstic, landslide, glacial, and relict lakes — are less common. Eutrophic lakes predominate in terms of trophic regime, with mesotrophic lakes being less common (Polissia, Carpathians) and oligotrophic lakes being the rarest. The latter occur primarily in the Carpathians and extremely rarely in Polissia. The largest lake in Polissia is Lake Svitiaz (of karstic origin), with an area of 24.2 km², an average depth of 7 m, and a maximum depth of 58 m. Situated in the Danube Delta lowland is Lake Yalpug, the largest freshwater lake in Ukraine (area 220 km², average depth 2.6 m, maximum depth 6 m). A significant number of brackish lakes are concentrated in Steppe Crimea, where salinity reaches 10-19%. Lakes are relatively scarce in the Carpathians and Crimean Mountains. The largest lake in the Carpathians is Lake Synevyr, situated at an altitude of 700 m with a depth of 16-24 m.

Floodplain lakes range in area from 0.1-1 ha to several hundred hectares (along the Dnieper, Desna, Seversky Donets, etc.). Their water bodies are elongated along the river channel, less frequently oval or round in shape. Their average depth ranges from 150 to 250 (500) cm, reaching up to 15 m in certain lakes. The bottom is flat, with sandy (mesotrophic water bodies), silty-sandy, and silty-peaty (eutrophic) sediments; the average water pH is 6.0-8.0. In these lakes, aquatic macrophytes typically occupy coastal shallows, forming successive vegetation belts. In overgrown water bodies, they are distributed evenly across the entire water area in mosaic patches. The areas of the lake farthest from the river channel are more intensively overgrown with aquatic plants and feature dense vegetation cover.

The most characteristic plant communities across vegetation belts with increasing depth in Polissia include Glycerietum maximae, Glycerio fluitantis-Oenanthetum aquaticae, Typhetum angustifoliae, Potametum obtusifolii, Potametum natanto-lucentis, Potameto natantis-Nymphueetum candidae, Myriophyllo-Nupharetum, Hydrochari-Stratiotetum, and others. In the Forest-Steppe zone, The Role of Phragmitetum communie, Glycerietum plicatae, Sagittario-Sparganietum emersi, Typhetum angustifoliae, Myriophyllo-Nupharetum, and Potametum crispi increases, whereas the role of Glycerio fluitantis-Oenanthetum aquaticae, Potametum obtusifolii, and Potameto natantis-Nymphaeetum candidate decreases. The vegetation belts of floodplain water bodies in the steppe zone are distinguished by the predominance of Scirpetum lacustris, Phragmitetum communis, Glycerietum maximae, and Bolboschoenetum maritime-maritimi communities, while deeper areas are dominated by Batrachio circinati-Alismatetum graminei, Potametum pectinati, and others. Characteristic patch-forming communities in overgrowing floodplain water bodies of Polissia are Typhetum latifoliae and Scirpetum lacustris, whereas in areas with a constant water level, Elodeetum canadensis, Potameto natantis-Nymphaeetum candidate, Potametum lucentis, and Ceratophylletum submerse prevail. In the Forest-Steppe, Alopecuro-Alismetum, Eleocharitetum palustris, Potametum crispi, Nymphaeetum albo-luteae, Schoenoplectetum tabernaemontani, Typhetum laxmannii, Bolboschoenetum maritime-maritimi, Najadetum marinae, Lemno-Spirodele, Parvopotameto-Zannichellietum palustris, and Batrachietum rionii frequently occur.

Rare communities such as Trapetum natantis, Nemphoidetum peltatae, Spirodelo-Aldrovandetum, and Salvinio-Spirodeletum, as well as endangered ones like Potametum natantis, Ceratophylletum submerse, Potametum obtusifolii, and Nymphaeetum albo-luteae, are found in floodplain water bodies across all regions. The habitats of the latter are shrinking due to anthropogenic pressure and edaphotope eutrophication. The group of endangered communities also includes Ponametum candidate, Potametum obstusifolii, and Nymphaeetum albo-luteae.

Extrafloodplain lakes of ancient river valleys are characteristic of Polissia, whereas in the Forest-Steppe and Steppe they are scarce. These water bodies are circular or oval-circular in shape with gently sloping banks, spanning from 0.1 to several tens of hectares, with an average depth of 50–150 (200) cm, and occasionally 500 cm. The bottom is flat, covered with thick muddy (Forest-Steppe, Steppe) or muddy-peaty (Polissia) deposits, with a water pH ranging from 7.0–8.0 (Polissia, Forest-Steppe) to 8.4–8.7 in the Steppe. Unlike northern lakes, southern ones are almost entirely overgrown with vegetation. Aquatic macrophytes occupy the entire littoral zone as well as shallow waters up to 200 cm deep. The macrophyte communities are arranged zonally in Polissia, less frequently patch-zonally, and patch-zonally in the Forest-Steppe and Steppe.

Vegetation belts in Polissia and the Forest-Steppe are dominated by communities with a high proportion of Phragmitetum communis (Polissia) and Typhetum angustifoliae (Forest-Steppe) coenoses. In extrafloodplain water bodies of ancient river valleys in Polissia, Trapetum natantis and Salvinio-Spirodeletum communities occur more frequently than in floodplain ones. In Forest-Steppe and steppe water bodies, Ceratophylletum lanaitici, Potarrretum sarmatici, and Potametum natanto-lucentis are rare. Areas with unstable water regimes are characterized by Eleocharitetum palustris, Schoenoplectetum tabernaemontani, Najadetum marinae, Lemnö-Spirodertetum, Salvinieto-Spirodelletum, and Potametum pectinati. Spring-flooded lakes of ancient watercourses in drainage basins subject to heavy anthropogenic eutrophication are distinguished by the dominance of Celatopliylletum demersi, Potametum pectinati, and Parvopotameto-Zannicliellietum palustris coenoses.

Extrafloodplain lakes of karst and glacial origin are typical of northwestern Ukraine (Volyn and Rivne regions). They have a circular or oval-circular shape and cover areas ranging from 1–2 to several hundred hectares. The average depth of these lakes is 3–5 m, with a maximum of 7–8 m. The bottom is mostly flat, covered with sandy and muddy-sandy deposits. Muddy-peaty deposits occur along the boundary between the lake and mire massifs, with a water pH of 4.5–6.8. Aquatic macrophytes occupy a narrow shallow-water zone up to 50–70 (100) m wide, arranged in bands. Karst and fluvioglacial lakes occur both with and without Sphagnum quagmires. The latter are characterized by macrophyte belts of Scirpetum lacustris, Typhelum latifoliae, Typhetum angustifoliae, Glycerietum maximae, Eleocharitetum palustris, and less frequently Phragmitelum communis. In areas with permanent flooding, sparse coenoses of Polygonetum amphibii, Potametum natantis, Nupharo lutei-Nyinphaeetum albae, and Potameto natantis-Nymphaeetum candidae are found. Other communities are much rarer, including phytocoenotic fragments of the Isoeto-Lobelietum association, which are confined to shallow, sparsely overgrown water bodies and form a submerged vegetation belt along their shores. When water bodies are fully or partially surrounded by mire massifs (most often mesotrophic), Sphagnum quagmires develop at their contact zones. These are rare and characteristic of forest and subalpine belts of the Ukrainian Carpathians. Rare and relict species whose continuous ranges lie much further north grow on these quagmires, notably bog sedge (Scheuchzeria palustris), great sundew (Drosera anglica), mud sedge (Carex limosa), cordroot sedge (C. chordorhiza), and others.

Interfluve lakes are characteristic of the delta regions of major rivers such as the Dnieper, Dniester, and Danube. They feature low banks, an average depth of 50–100 (150) cm, and occasionally 200 cm. Bottom deposits are muddy, with the silt layer often exceeding 100 cm in thickness, and water pH ranging from 7.8–8.4. Aquatic macrophyte communities cover the entire surface of these lakes, arranged in concentric bands. The central part is dominated by patches of Phragmitetum communis and Typhetum angustifoliae communities. Towards the open water and also along the perimeter, Elodeetum canadensis, Potametum perfoliati, Potametum pectinati, Myriophylletum spicati, and Potametum lucentis develop. Stands of Ceratophylletum demersi, Lenmo-Spirodelletum, and Salvinio-Spirodelletuni coenoses frequently occur among these communities. Further toward the center of the water body lie Nupharo lutei-Nymphaeetum albae and Nymphaeetum albo-luteae, occupying the entire central water area. Here, especially in areas with local currents, rare phytocoenoses occur, such as Trapetum natantis, Trapo-Nymphoidetum peltatae, Nymphoidetum peltatae, and Spirodelo-Aldrovandetum.

Estuaries (limans) in Ukraine are mostly located in the Steppe zone. Based on water mineralization, they are classified as freshwater, slightly brackish, and highly brackish. The Dniester Estuary (area 360 km²) is the freshest water estuary.

Among highly brackish estuaries, Kuyalnik and Hadzhibei stand out for their large surface areas. The estuaries are characterized by shallow depths (averaging 200–500 cm). The bottom is generally flat, muddy-sandy, with significant illuvial deposits in places. Macrophyte communities in freshwater estuaries occupy all shallow water areas as well as the littoral zones. Phragmitetum communis and Typhetum angustifoliae communities predominate here, while Typhetum laxmannii, Scirpetum lacustris, and Schoenoplectetum tabernaemontani form near the shores and throughout the upper PARTS OF THE estuary. Between these communities, as well as in open waters, Parvopotameto-Najadetum coenoses are widespread. In sheltered areas, Batrachietum rionii, Ceratophylletum demersi, Myriophyllo-Potametum, and Potametum crispi coenoses can be found.

In slightly brackish estuaries, macrophyte communities are typically confined to alluvial deposits formed by river runoff in the avandelta and are distributed in bands corresponding to the decrease in these deposits and the increase in water depth. These formations are cone-shaped, pointing upstream. The expanded part is dominated by Phragmitetum communis, Typhetum angustifoliae, and Scirpetum lacustris communities. Toward the open water of the estuary, coenoses of Sparganietum erecti, Potametum pectinati, Potametum perfoliati, and Ceratophylletum demersi are located, interspersed with patches of floating-leaved macrophytes such as Nymphoidetum peltatae, Nupharo lutei-Nymphaeetum albae, and Trapetum natantis. In areas with a water depth of up to 300 cm, patches of Potametum perfoliati and Potametum pectinati form across the estuary (Dniester Estuary). In the littoral Zones of the middle and lower parts of the estuaries, aquatic plant communities occur as isolated patches of Myriophylletum verticillati and Potametum pectinati.

Species of brackish habitats—such as Zannichellietum palustris, Ruppietum maritimae, and Zosteretum marinae—play a significant role in the aquatic vegetation of shallow areas in estuaries adjacent to marine waters. These same communities represent the vegetation of brackish estuaries, where they form mosaic patches. Near the shores of these estuaries, isolated patches of various shapes belonging to Phragmitetum communis, Typhetum laxmannii, Scirpetum lacustris, and Bolboschoenetum maritimi coenoses occur, mostly confined to the upper reaches of the estuaries. In highly brackish estuaries, vegetation formed by wide-amplitude ecological species is concentrated in the upper part, while halohydrophytic vegetation is found in areas with a water depth of 50–200 cm. These are characterized by Zosteretum marinae (in areas with muddy deposits) and Ruppietum maritimae (on sandy bottom deposits). In coastal shallows with fluctuating water levels, Scirpetum maritimi, Scirpetum lacustris, and Bolboschoenetum maritimo-maritimi communities occur. Phragmitetum communis and Typhetum laxmannii communities are widespread in the upper parts of the estuaries.

Shallow coastal marine areas. Aquatic macrophytes occur in shallow coastal marine zones. These habitats are characterized by relatively shallow depths (50–250 (500) cm) and shell-sandy, less frequently muddy-shell-sandy bottom deposits. They feature large areas occupied by aquatic macrophyte communities with a broad ecological amplitude and halohydrophytes. These communities are typical of the pre-Mouth areas of the Danube, Dniester, and Dnieper rivers, as well as small rivers flowing into the Black and Azov seas. Particularly large areas are occupied by macrophyte communities in Yagorlyk, Tendrov, and Dzharyлгач (Dzharylgach) bays of the Black Sea, and Berdyansk, Obitochna, Belosaraysk, and Sivash bays of the Azov Sea.

In shallow waters and areas with unstable moisture, Scirpetum maritimi, Scirpetum lacustris, Bolboschoenetum maritimo-maritimi, Phragmitetum communis, Typhetum laxmannii, and Schoenoplectetum tabernaemontani coenoses are concentrated. Areas with permanent flooding are occupied by submerged macrophyte communities, whose distribution and composition depend on local ecological conditions. In pre-mouth marine coastal zones where sea and river waters mix, large areas are occupied by Potametum pectinati and Myriophylletum verticillati communities, alongside Najadetum marinae and Parvopotameto-Zannichellietum palustris. In marine bays and habitats with muddy-sandy-shell deposits, Ruppietum maritimae, Zannichellietum palustris, and Zosteretum marinae associations predominate. In areas with sandy-shell deposits, Ruppietum maritimae communities are found, while the aforementioned communities occur much less frequently.

Mires and Wetlands. Aquatic macrophytes are widely represented in Ukrainian wetlands, which cover about 1.2 million hectares. The largest number of wetlands is concentrated in Ukrainian Polissia [3]. The average boggy proportion of this territory is 6.3%, reaching a maximum of 11%. In the Forest-Steppe, wetlands cover 1.6%, in the Carpathians 0.4%, and in the Steppe only 0.3%. Wetlands up to 50 hectares predominate. About 40% of wetlands cover areas exceeding 100 hectares, and only 7% span around 1,000 hectares. The vast majority of Ukrainian wetlands are lowland mires located in river valleys (Polissia and northern Forest-Steppe districts). Among the large mire massifs of ancient river valleys are the Irdyn and Tiasmin mires (Forest-Steppe). Eutrophic mires predominate by trophic type (over 80%). Mesotrophic mires (11–12%) occur mainly in Polissia and less frequently in the Forest-Steppe. Oligotrophic mires (4–5%) are situated in Polissia and the Carpathians.

Aquatic macrophytes occur more frequently in wetland water bodies whose area typically does not exceed 1,000 m², with a depth of 10–30 (150) cm, and peaty and muddy-peaty bottom deposits. Aquatic macrophyte communities form discrete patches. Most frequent are Ceratophylletum submersi, Ceratophylletum demersi, Potameto natantis-Nymphaeetum candidae, Potametum compressa, Potametum lucentis, Stratiotetum aloidis,

and Hydrocharitetum morsus-ranae. Macrophyte communities characteristic of wetland habitats, such as Thelypteridi-Phragmitetum and Cicuto-Caricetum pseudocyperi, grow in the littoral zone.

In addition to water bodies, aquatic macrophyte communities are also widespread in wetland depressions. They participate in The formation of the herbaceous cover and are therefore classified as wetland vegetation by many researchers. These are typically broad-ecology communities whose edificators can thrive under waterlogging and temporary moisture deficits. They include common reed (Phragmites australis), broadleaf cattail (Typha latifolia), narrow-leaf cattail (T. angustifolia), sharp sedge (Carex acuta), lesser pond sedge (C. acutiformis), tufted sedge (C. elata), bohemian sedge (C. bohemica), false fox sedge (C. pseudocyperus), marsh marigold (Caltha palustris), marsh woundwort (Stachys palustris), cowbane (Cicuta virosa), water-cup (Beckmannia eruciformis), water forget-me-not (Myosotis palustris), floating mannagrass (Glyceria fluitans), bog bean (Menyanthes trifoliata), and sweet flag (Acorus calamus).

Aquatic macrophyte communities are widespread in temporarily flooded and waterlogged areas. They are formed by species capable of rapid development and of surviving certain periods (2–3 months during the growing season) without optimal moisture. In areas with surface flooding and no waterlogging, the most frequent species are: in areas with a water level above 15 cm—lesser duckweed (Lemna minor), greater duckweed (Spirodela polyrrhiza), amphibious bistort (Polygonum amphibium), dark-green hornwort (Ceratophyllum demersum); below 15 cm—mudwort (Limosella aquatica), nodding bur-marigold (Bidens cernua), brooklime (Veronica beccabunga), pale persicaria (Polygonum lapathifolium), short-fruited yellow-cress (Rorippa brachycarpa), naked flatsedge (Cyperus glaber), clustered flatsedge (C. glomeratus), and narrow-leaf cattail (Typha angustifolia). In waterlogged areas, the dominant species are spreading water-crowfoot (Batrachium divaricatum), Berchtold's pondweed (Potamogeton berchtoldii), Fries' pondweed (P. friesii), marsh marigold (Caltha palustris), common spikerush (Eleocharis palustris), water-dropwort (Oenanthe aquatica), greater water-parsnip (Sium latifolium), water forget-me-not (Myosotis palustris), and broadleaf cattail (Typha latifolia). In saline areas (with groundwater sub-irrigation), communities formed by creeping bentgrass (Agrostis stolonifera), sea club-rush (Bolboschoenus maritimus), and lanceolate water-plantain (Alisma lanceolatum) are more frequent.

Ponds and Reservoirs. Over 23,000 ponds and reservoirs have been built in Ukraine for economic river flow regulation. The largest number of them has been created in the basins of the Dnieper, Southern Bug, and Dniester rivers. High flow regulation is characteristic of the Siversky Donets and Azov Sea river basins. In terms of water volume, reservoirs of the Dnieper cascade stand out. In addition, reservoirs with a water volume exceeding 100 million m³ include Ladyzhyn (Southern Bug), Karachunivka (Inguletz), Pechenihy (Siversky Donets), and Chervony Oskil (Oskil). Sixty reservoirs have a volume of 10–100 million m³, while the rest hold up to 10 million m³ of water. Reservoirs with hydroelectric power plants experience fluctuating water levels throughout the year.

The largest number of ponds is concentrated in the Middle and Lower Dnieper basins, totaling about 6.7 thousand with a total water surface area of 284 km². A significant number of ponds are also found in the basins of the Prypiat, Southern Bug, and Dniester rivers, as well as along the Black Sea coast. The area of most ponds does not exceed 10 hectares.

According to their origin and water supply, ponds are classified as river dams, embankment ponds, excavated ponds (kopanky), and supplied (fill-and-draw) ponds. The former are small, located on intermittent small streams or rivulets, and receive year-round water replenishment. Embankment ponds are typically situated in gullies and ravines, fed mainly by precipitation or snowmelt, alongside groundwater. Supplied ponds are filled with water from rivers and other water bodies. The hydrological features of ponds are determined by the composition of their water sources and economic management regime.

The areas occupied by aquatic macrophytes growing in ponds and reservoirs have recently increased due to expanding hydro-construction in the country. The largest stands occur in artificial reservoirs formed on rivers (Dnieper, Southern Bug, Northern Donets) or by partial damming of watercourses (Ros, Ingul, Rosava, Snyvukha, etc.). Macrophyte communities predominate in the upper and coastal shallows of the middle sections of reservoirs, while occurring less frequently in the lower sections. Their spatial distribution is closely linked to local currents, bottom sediment composition, water depth, and site shelter. In artificial reservoirs, emergent macrophytes are dominated by Phragmitetum communis, Typhetum angustifoliae, Scirpetum lacustris, Glycerietum maximae, Rorippo amphibiae-Oenanthetum aquaticae, Typhetum latifoliae, Eleocharitetum palustris, Sparganietum erecti, and Sagittario-Sparganietum emersi, while in Polissia and Forest-Steppe regions, Caricetum ripariae, Caricetum gracilis, Caricetum vesicariae, Caricetum vulpinae, Phalaridetum arundinaceae, and many others also occur. They frequently form vegetation belts in littoral zones and patches in open shallows. Areas with permanent flooding are dominated by Potametum perfoliati, Potametum lucentis, Potametum pectinati, Potametum graminei, Myriophylletum verticillati, Nupharo lutei-Nymphaeetum albae, Potameto natantis-Nymphaeetum candidae, Polygonetum amphibii, and Potametum natantis. In recent years, the areas of Hydrocharitetum morsus-ranae and Hydrochareto-Stratiotetum communities have expanded. In southern reservoirs (Kakhovka), the areas of rare Trapetum natantis and Nymphoidetum peltatae communities are increasing, whereas in northern ones, Potameto natantis-Nymphaeetum candidae is expanding.

Aquatic macrophyte communities frequently occur in ponds, being confined to shallow areas and typically forming patches. Their composition is dominated by communities of alluvial habitats, the most widespread being Typhetum angustifoliae, Glycerietum maximae, Bolboschoenetum maritimi continentale, Glycerio fluitantis-Agrostietum stoloniferae, Sparganio-Glycerietum fluitantis, and Rorippo amphibiae-Oenanthetum aquaticae, alongside true aquatic communities such as Ceratophylletum demersi, Myriophylletum verticillati, Potametum natanto-lucentis, Potametum perfoliati, Polygonetum amphibii, and Nymphoidetum peltatae (in southern regions).

In flooded former peat-extraction quarries, aquatic macrophyte communities in shallow areas are represented by Typhetum latifoliae, Typhetum angustifoliae, and less frequently Phragmitetum communis. Substantial areas are occupied by Stratiotetum aloidis, Lemnetum trisulcae, Lemnetum minoris, Lemno-Spirodelletum, and Hydrocharitetum morsus-ranae coenoses. Among them, patches of Potameto natantis-Nymphaeetum candidae and, less commonly, Nupharo lutei-Nymphaeetum albae are frequently found.

In flooded quarries of former crystalline rock mining, sparse communities of Potametum pectinati, Potametum perfoliati, and Myriophylletum verticillati (southern regions) develop, usually occurring as patches.

The distribution of macrophyte communities in drainage canals depends on the presence and type of lining, the age of the canals, bank slopes, and water flow velocity. They are mostly concentrated near the canal banks, while in overgrowing canals they occupy the entire bed. The vegetation comprises Phragmitetum communis, Typhetum angustifoliae, Typhetum laxmannii, Typhetum minimae (southern regions), Glycerietum maximae, Sparganio-Glycerietum fluitantis, Eleocharitetum palustris, Typhetum latifoliae, and others. In deeper areas, Potametum graminei, Potametum obtusifolii (Polissia, Forest-Steppe), Potametum pectinati, Potametum perfoliati, and Myriophylletum verticillati (Forest-Steppe, Steppe) develop primarily.