AQUATIC PLANT COMMUNITIES OF THE LEMNETEA MINORIS R.Tx CLASS IN THE BUG VALLEY OLD RIVER-BEDS AGAINST THE HABITAT CONDITIONS

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1 Teka Kom. Ochr. Kszt. Środ. Przyr., 2006, 3, AQUATIC PLANT COMMUNITIES OF THE LEMNETEA MINORIS R.Tx CLASS IN THE BUG VALLEY OLD RIVER-BEDS AGAINST THE HABITAT CONDITIONS Danuta Urban *, Hanna Wójciak ** * Institute of Soil Science and Environmental Management, Agricultural University of Lublin, K. Leszczyńskiego str. 7, Lublin, Poland, danuta.urban@ar.lublin.pl ** Department of Botany and Mycology, Institute of Biology, Maria Curie-Skłodowska University Akademicka str. 19, Lublin, Poland, hwojciak@biotop.umcs.lublin.pl Summary. In 2003 studies of the habitat conditions and distribution of water plant communities of the Lemnetea, Charetea and Potametea classes as well as rush communities of the Phragmitetea class were begun in several dozen old river-beds in the Bug valley (along the Kryłów Kodeń stretch of the border) [Urban and Wójciak 2004]. In the years the studies encompassed Bug valley old river-beds where phytocenoses of the Lemnetea minoris class occurred. Spirodeletum polyrhizae (Kelhofer 1915) w. Koch em. R. Tx. Et a. Schwabe 1974 in r. Tx and Lemnetum trisulcae (Kelhofer 1915) Knappet Stoffers 1962 associations predominated, whereas the Wolffietum arrhizae Miyaw. Et j. Tx and Lemnetum gibbae Miv. Et j. Tx associations were less common in the studied floodplain lakes. The following parameters were determined in water and sediment samples collected in the old river-beds (at sites where communities of the Lemnetea minoris class occur): ph along with phosphorus, potassium, sodium, calcium, magnesium and iron content, as well as electrolytic conductivity in the water samples and organic matter content in the sediments. Key words: old river-beds, the Bug valley, plant associations of the Lemnetea minoris class, chemical properties of water and deposits INTRODUCTION Meandering lakes, called old river-beds, river lakes or buŝyska, are characteristic hydrographic features of the Bug Valley [Michalczyk et al. 2002]. In the old river-beds associations of aquatic plants, rushes, waterside terophytes and periodically wet cavities developed along with alder and willow carrs, riparian purple willows as well as willowand-poplar riparian forests [Wójciak and Urban 2003]. The results of earlier studies [Wójciak and Urban 2004] indicate that the Spirodeletum polyrhizae and Lemnetum trisulcae associations predominated in the analysed water bodies; these associations are also common in other parts of the Lublin region and Poland [Tomaszewicz 1979, Fijałkowski and Izdebski 1996, Urban and Wójciak 2003]. Wolffietum arrhizae and

2 242 Danuta Urban, Hanna Wójciak Lemnetum gibbae associations occurred more rarely in old river-beds of the Bug valley [Wójciak and Urban 2004]. The studies were aimed at determining the habitat conditions (chemical properties of waters and bottom sediments) of aquatic plant associations of the Lemnetea minoris class in selected old river-beds in the Bug valley. STUDY AREA, MATERIAL AND METHODS In the years , studies concerning the habitat conditions of aquatic plant associations of the Lemnetea minoris class were conducted in 28 old river-beds of the Bug valley (along the Kryłów-Kodeń stretch of the border). The study area encompassed shallow water bodies situated in the vicinity of the following localities: Kryłów (Kr1, Kr2), Starosiele (Sr), Dubienka (Db1, Db2), Uchańka (Uch), Husynne near Okopy (Hs), Okopy Nowe (ON1, ON2), Hniszów (Hn1, Hn2), Wola Uchruska (WU), Stulno (St1, St2), ZbereŜe (Zb), Sobibór wieś (Sb1, Sb2), Dołhobrody (Dł1, Dł2), Łydyny (Ły), Sławatycze (Sł1, Sł2), Liszna (Li), Nowosiółki (Nw1, Nw2), Jabłeczna (Jb1, Jb2) and Kodeń (Kd). The immediate surroundings of the old river-beds under study varied: the Kr1, Kr2, Db1, Db2, Zb, Sb1, Dł2 reservoirs and, partially, the Sł1, Li and Jb1 reservoirs were adjoined by meadows of the Molinio-Arrhenatheretea class. The Hn, Sb2 and, partially, the Sb1, Dł1, Sł2, Jb2 and Kd old river-beds were close to alder carrs and willow thickets of the Alnetea glutinosae class, as well as willow and mixed poplar-and-willow riparian forests of the Salicetea purpureae class. At the banks of water bodies Hs (north), Uch (south), ON1 (north), ON2 (south), WU1, St1 (south), Zb (west), Dł1 (west), Ły (all sides), Nw2 (east), Ja2 (east) and Kd (east) there were some buildings, whereas tarmac roads were close to the buŝyska designated as St2, Sł1, Sł, Li, Jb1 and Jb2 old [Urban and Wójciak 2004]. Phytosociological studies were conducted in the years (in June and August), using the generally recognized Braun-Blanquet method [1951]. Phyto-sociological units were distinguished according to studies by Matuszkiewicz [2005], Fijałkowski [1991] and Tomaszewicz [1979]. Water and bottom sediment samples were collected from the old river-beds studied (at sites where communities of the Lemnetea minoris class occur) in the autumn of The following parameters of the water samples were determined according to the methodology described by Hermanowicz et al. [1999] and Dojlido [1995]: ph, electrolytic conductivity and total phosphorus content. In the bottom sediment samples, ph in H 2 O and organic matter content were determined through combustion at a temperature of 560ºC. After mineralizing the deposits in a mixture of nitric acid and perchloric acid, the following parameters were determined in the solutions and water samples: Ca, K and Na (using flame emission spectrometry) as well as Mg and Fe (using absorption atomic spectrometry (AAS). RESULTS AND DISCUSSION Based on the studies conducted, the following associations of the Lemnetea minoris class were distinguished (Tab. 1):

3 AQUATIC PLANT COMMUNITIES OF THE LEMNETEA MINORIS Lemnetum gibbae Miv. et J. Tx (Table 1, relevé 1); Spirodeletum polyrhizae (Kelhofer 1915) W. Koch em. R. Tx. et A. Schwabe 1974 in R. Tx (Table 1, relevé 2-13); Lemnetum trisulcae (Kelhofer 1915) Knappet Stoffers 1962 (Table 1, relevé 14-24); Wolffietum arrhizae Miyaw. et J. Tx (Table 1, relevé 25-28). Table 1. Floristic composition of associations of the Lemnetea minoris class in 28 old-river beds of the Bug valley Tabela 1. Skład florystyczny zbiorowisk z klasy Lemnetea minoris w 28 starorzeczach doliny Bugu Old river-bed Starorzecze Kr2 Jb1 Uch Dł1 Sr Hn2 Hs Sb2 Ły Li Sł2 Sł1 Nw ON ON Hn1 Db1 Zb WU Db2 St2 Sb1 Kr1 Kd Jb2 Nw Dł2 St1 Association Zbiorowisko No. of phytosociological relevé Nr zdjecia fitosocjologicznego Water surface cover in % Pokrycie lustra wody w % Number of species in relevé Liczba gatunków w zdjęciu Lemna gibba Spirodela polyrhiza Lemna minor Lemna trisulca Wolffia arrhiza Potametea: Lemna turionifera Hydrocharis morsus ranae Ceratophyllum demersum Nymphaea alba Utricularia vulgaris Stratiotes aloides Nuphar lutea Phragmitetea: Sagittaria sagittifolia Lemnetum gibbae Miv. et J. Tx. 1960, 2. Spirodeletum polyrhizae (Kelhofer 1915) W. Koch em. R. Tx. et A. Schwabe 1974 in R. Tx. 1974, 3. Lemnetum trisulcae (Kelhofer 1915) Knappet Stoffers 1962, 4. Wolffietum arrhizae Miyaw. et J. Tx In small and shallow floodplain lakes (Kr1, Db2, ON1, Hn1, Hn2, St1 and St2, Ły, Sł2, Li, Nw1, Jb1 and Jb2), these phytocenoses usually occupied the entire water table (August 2004 and 2005). In larger old river-beds, they occurred in the form of small patches amid rush plants. The phytocenoses in the Bug valley were connected with quiet and shallow old river-beds, between cm and 2 metres in depth. Mineral or mixed mineral-and-organic formations (more rarely organic formations) constituted the substratum of these reservoirs. During the analysis of the study results, it was found that both the deposits and water samples collected from the old river-beds had an alkaline or neutral reaction (Tabs 3, 4). The organic matter content in the collected sediment samples ranged from 33.1 (Hn1) to 98.1% (Dł1). With regard to the organic matter content [Dąbkowski and Pawłat-Zawrzykraj 2003], the samples studied can be divided into the following groups:

4 244 Danuta Urban, Hanna Wójciak mineral deposits (organic matter content < 5%); samples: Db1, Sr, WU, Zb, St2, Uch, Hn2, Dł1, Ły, Sł2, Li, Nw1, St1, Dł2, Nw2, Jb2; organic-and-mineral deposits (organic matter content 5-20%); samples: Db2, Kd, Sb2, Jb1, Hs, SŁ1, Kr2; organic deposits (organic matter content > 20%); samples: Hn1, NN2, Kr1, ON1, Sb2. The electrolytic conductivity of the analysed water samples ranged from 284 to 799 µs cm 1. The highest conductivity (above 700 µs cm 1 ) characterized water samples collected from the ON2, ON1 (Lemnetum trisulcae) and Sł2 (Spirodeletum polyrhizae) old river-beds, whereas samples from the Dł1 (Spirodeletum polyrhizae) exhibited the lowest conductivity. Data from Tables 2 and 3 indicate that the macroelement content in the water and bottom deposit samples was varied. The total phosphorus content in the water samples ranged from 0.08 to 0.61 mg dm 3. The highest P concentrations (above 0.40 mg dm 3 ) were recorded in the water of the Kr2 (Lemnetum gibbae), Hn1, Kd, Kr1, ON1 (Spirodeletum polyrhizae), Hs (Lemnetum trisulcae) and Jb2 (Wolffietum arrhizae) old river-beds, whereas the lowest concentrations (below 0.20 mg dm 3 ) occurred in the water of the Sb1, Jb1, Sł1 (Lemnetum trisulcae) and Nw1 (Spirodeletum polyrhizae) reservoirs. Studies by Woyciechowska and Dojlido [2003] indicate that the Bug River waters are characterized by high general phosphorus concentrations. The highest concentrations were recorded in the upper reaches of the river. The maximum phosphorus concentration (in the vicinity of Horodło) stood at 1.29 mg dm 3. Characteristic concentrations within the Kryłów-Terespol stretch ranged from 0.30 to 1.24 mg dm 3 P. The phosphorus content of the deposits analysed ranged from 0.3 to 2.0 g kg 3. The highest P content was found in sediments from the Kd (Lemnetum trisulcae), Sł1 (Spirodeletum polyrhizae) and Jb2 (Wolffietum arrhizae) old river-beds, whereas the lowest one occurred in the WU (Lemnetum trisulcae), Jb1 and Nw1 (Spirodeletum polyrhizae) river-beds. According to Bojakowska and Sokołowska [2003], the bottom deposits of the Bug River contain 0.06% P (0.6 g kg 3 ) on average. The results of analyses indicate that the potassium content in the water samples was varied and ranged from 0.7 to 75.3 mg dm 3. The highest K content was found in samples from the ON1, ON2 (Lemnetum trisulcae), Uch and Ły (Spirodeletum polyrhizae) water bodies, whereas the lowest one was recorded in samples from the Nw2 (Lemnetum gibbae) and Li (Spirodeletum polyrhizae) old river-beds. According to Dojlido [1995], the potassium content in the waters of the Bug River (estuary) ranged from 3 to 6 mg dm 3 (4.5 mg dm 3 on average). The potassium content in the sediment samples was balanced and ranged from 0.01 to 0.08 g kg 3. Deposits from the ON2, Uch, ON1 and Ły water bodies were characterized by the highest K content. During analysis of research results it was found that the sodium content in the water samples collected ranged from 7.7 to 39.6 mg dm 3. The highest Na content was recorded in the ON2, St2, Kr1 (Lemnetum trisulcae), Jb1, Hs, Sł2 (Spirodeletum polyrhizae) and St1 (Wolffietum arrhizae) old river-beds. According to Dojlido [1995], the sodium content in the waters of the Bug River ranged from 16 to 34 mg dm 3 (22 mg dm 3 on average). The sodium content of the deposits studied ranged from 0.3 to 0.17 g kg 3. The highest Na content was found in samples collected from the ON2, WU, St2 (Lemnetum trisulcae) and St1 (Wolffietum arrhizae) old river-beds, whereas the lowest was recorded in the Db1, Db2 (Lemnetum trisulcae), Uch and Hs (Spirodeletum polyrhizae) river-beds.

5 AQUATIC PLANT COMMUNITIES OF THE LEMNETEA MINORIS Table 2. Diversity of ph, conductivity and chemical composition in surface waters in 28 old river-beds of the Bug valley (along the Kryłów Kodeń stretch of the border) Tabela 2. ZróŜnicowanie ph, przewodności i właściwości chemicznych wody w 28 starorzeczach doliny Bugu (na odcinku granicznym Kryłów Kodeń) Old river-bed Starorzecze ph Conductivity Przewodność µs cm 1 Content Zawartość (mg dm 3 ) P K Na Ca Mg Fe Lemnetum gibbae Kryłów Kr Spirodeletum polyrhizae Jabłeczna Jb Uchańka Uch Dołhobrody Dł Starosiele Sr Hniszów Hn Husynne Hs Sobibór Sb Łydyny Ły Liszna Li Sławatycze Sł Sławatycze Sł Nowosiółki Nw Lemnetum trisulcae Okopy Nowe ON Okopy Nowe ON Hniszów Hn Dubienka Db ZbereŜe Zb Wola Uhruska WU Dubienka Db Stulno St Sobibór Sb Kryłów Kr Kodeń Kd Wolfietum arrhizae Stulno St Dołhobrody Dł Nowosiólki Nw Jabłeczna Jb The results of analyses presented in Table 1 indicate that the calcium content in the water samples was varied and ranged from 26.7 to 132,2 mg dm 3, and reached the highest values in the Db2, ON1, ON2, St2 (Lemnetum trisulcae), Hs and Ły (Spirodeletum polyrhizae) old river-beds. Samples from Zb and Sb1 (Lemnetum trisulcae) were characterized by the lowest Ca content. According to Dojlido [1995], the waters of the Bug River (in the vicinity of Wyszków) contained between 39 and 116 mg dm 3 Ca (80 mg dm 3 on average). The calcium content in the deposits analysed was also varied and ranged from 0.48 to

6 246 Danuta Urban, Hanna Wójciak 4.17 g kg 3. Deposits from the Hn1, ON2 and WU (Lemnetum trisulcae) old river-beds exhibited the highest Ca content, whereas the lowest content was found in sediments from the Uch, Nw1 (Spirodeletum polyrhizae) and Jb2 (Wolffietum arrhizae) water bodies. Studies by Bojakowska and Sokołowska [2003] indicate that the bottom sediments of the Bug River contain 4.25% Ca (42.5 g kg 3 ) on average. Table 3. Diversity of ph and chemical composition of bottom deposits in 28 old river-beds of the Bug valley (along the Kryłów Kodeń stretch of the border) Tabela 3. ZróŜnicowanie ph i właściwości chemicznych osadów dennych w 28 starorzeczach doliny Bugu (na odcinku granicznym Kryłów Kodeń) Old river-beds Starorzecze ph Organic matter Materia organiczna (%) Content Zawartość (g kg 3 ) P K Na Ca Mg Fe Lemnetum gibbae Kryłów Kr Spirodeletum polyrhizae Jabłeczna Jb Uchańka Uch Dołhobrody Dł Starosiele Sr Hniszów Hn Husynne Hs Sobibór Sb Łydyny Ły Liszna Li Sławatycze Sł Sławatycze Sł Nowosiółki Nw Lemnetum trisulcae Okopy Nowe ON Okopy Nowe ON Hniszów Hn Dubienka Db ZbereŜe Zb Wola Uhruska WU Dubienka Db Stulno St Sobibór Sb Kryłów Kr Kodeń Kd Wolfietum arrhizae Stulno St Dołhobrody Dł Nowosiólki Nw Jabłeczna Jb The content of magnesium in the water samples studied ranged from 2.0 to 15.9 mg dm 3. The highest Mg content was found in the ON1, ON2, Kr1, Db1 (Lemnetum minoris) and Hs (Spirodeletum polyrhizae) old river-beds, while the Sb1 and WU (Lemnetum trisulcae) buŝy-

7 AQUATIC PLANT COMMUNITIES OF THE LEMNETEA MINORIS ska exhibited the lowest Mg content. According to Dojlido [1995], the Mg content in the waters of the Bug river ranged from 10 to 20 mg dm 3. The Mg content of the deposits analysed ranged from 0.2 to 1.7 g kg 3. The highest Mg content was recorded in the deposits of the Db2 and Kd (Lemnetum trisulcae) old river-beds, whereas the Zb (Lemnetum trisulcae), Ły, Nw1 (Spirodeletum polyrhizae), Nw2 and Jb2 (Wolffietum arrhizae) sediments had the lowest Mg content. According to Bojakowska and Sokołowska [2003], the deposits of the Bug River contained 0.1% Mg (1.0 g kg 3 ) on average. The results of the analyses showed that the iron content in the water samples ranged from 0.03 to 1.06 mg dm 3. The highest Fe content was recorded in the ON2, Zb (Lemnetum trisulcae), Dł1, Ły (Spirodeletum polyrhizae) and Dł2 (Wolffietum arrhizae) reservoirs. The iron concentration in the waters of the Bug (in the vicinity of Wyszków) ranged from 0.20 to 0.94 mg dm 3 Fe (0.49 mg dm 3 on average). The deposits studied had a varied iron content, ranging from 1.19 to 22.8 g kg 3. The highest Fe content was found in the deposits from the Db1, St2 (Lemnetum trisulcae), Nw1 (Spirodeletum polyrhizae), St1, Nw2 and Jb2 (Wolffietum arrhizae) old river-beds. Studies by Bojakowska and Sokołowska [2003] indicate that the deposits of the Bug River contained 0.56 % Fe (5.6 g kg 3 ) on average. Water samples ranked by the average macroelement content (from the highest to the lowest) within the distinguished associations: P: Lemnetum gibbae>wolfietum arrhizae>lemnetum trisulcae>spirodeletum polyrhizae K: Lemnetum gibbae>lemnetum trisulcae>spirodeletum polyrhizae>wolfietum arrhizae Na, Mg: Lemnetum gibbae>spirodeletum polyrhizae>lemnetum trisulcae>wolfietum arrhizae Ca: Lemnetum trisulcae>spirodeletum polyrhizae>lemnetum gibbae>wolfietum arrhizae Fe: Wolfietum arrhizae>spirodeletum polyrhizae>lemnetum gibbae>lemnetum trisulcae Deposits ranked by the average macro- and microelement content (from the highest to the lowest) within the distinguished associations: P: Wolfietum arrhizae, Lemnetum trisulcae, Spirodeletum polyrhizae>lemnetum gibbae K, Na: Wolfietum arrhizae>lemnetum trisulcae>spirodeletum polyrhizae>lemnetum gibbae Ca: Lemnetum trisulcae>wolfietum arrhizae>spirodeletum polyrhizae>lemnetum gibbae Mg, Fe: Lemnetum gibbae>lemnetum trisulcae>spirodeletum polyrhizae>wolfietum arrhizae Figure 1 depicts correlation coefficients for the ph and macroelement content in the water and deposit system. No significant correlations were found, except the correlation between the ph of the water and ph of the deposits ph P K Na Ca Mg Fe Fig. 1. Correlation coefficients R 2 between the ph and content of macroelements determined in the water and deposit system in the old river-beds studied (28 samples, significant for α 0.10 = ) Rys. 1. Współczynnik korelacji R 2 pomiędzy zawartością makroelementów w wodzie i osadzie badanych starorzeczy (28 próbek, istotne dla α 0.10 = ) A study by Urban and Wójciak [2004] presents the results of chemical analyses of water samples from 30 old river-beds of the Bug valley. A comparison of these data with the results obtained in 2004 shows that:

8 248 Danuta Urban, Hanna Wójciak phosphorus and sodium concentrations in the water samples studied were higher in 2004 potassium, calcium and magnesium concentrations were lower in CONCLUSIONS 1. In the 28 old river-beds studied, the occurrence of 4 water plant associations of the Lemneta minoris (Lemnetum gibbae, Spirodeletum polyrhizae, Lemnetum trisulcae and Wolffietum arrhizae) class was found. 2. The highest P, K, Na and Mg content was found in water samples collected from old river-beds at sites where the Lemnetum gibbae association occurs. 3. The highest average P, K and Na content was found in deposit samples collected from old river-beds at sites where the Wolffietum arrhizae association occurs. REFERENCES Bojakowska I., Sokołowska G., Geochemistry of river and lake sediments. [In:] Dojlido J., Kowalczewski W., Miłaszewski R., Ostrowski J., (eds) The Bug river water and nature reserves. Wyd. IMiGW, WSzEi Z, Warszawa, pp (in Polish). Braun-Blanquet J., 1951, Pflanzensoziologie. Spronger Verlag, Wien, pp Dąbkowski Sz. L., Pawłat-Zawrzykraj A., Selected chemical characteristics of the bottom sediments in the Raszynka river catchment. Water Environment Rural, 3 (6), (in Polish). Dojlido J.R., Chemistry of surface water. Wyd. Ekonomia i Środowisko, Białystok, pp. 342 (in Polish). Fijałkowski D., 1991: Plant communities of the Lublin distrct. Wyd. UMCS, Lublin, pp. 303 (in Polish). Fijałkowski D., Izdebski K., Vegetation of the Lublin distrct. Wyd. LTN, pp. 88 (in Polish). Hermanowicz W., Dojlido J., DoŜańska W., Koziorowska B., Zerbe J., 1999: Physicochemical examination of water and sewage. Arkady, Warszawa, pp. 342 (in Polish). Matuszkiewicz W., 2005: A guide for marking Poland s plant communities. Wyd. Naukowe, PWN, Warszawa, pp Michalczyk Z., Kovalchuk I., Makarewicz A., Piszcz J., Turczyński M., 2002: Hydrologic characterization of the Bug basin. [In:] Dombrowki A., Głowacki Z., Jakubowski W., Kovalchsk I., Michalczyk Z., Nikiforov M., Szwajgier W., Wojciechowski K.H., (eds) Ecological corridor of the Bug river valley. State-threats-protection. IUCN, Warszawa, pp (in Polish). Tomaszewicz H., Poland s water and rush vegetation. Wyd. UW, Warszawa, pp Urban D., Wójciak H., Vegetation of water ecosystems. [In:] Dojlido J., Kowalczewski W., Miłaszewski R., Ostrowski J., (eds) The Bug river water and nature reserves. Wyd. IMiGW, WSzEiZ, Warszawa, pp (in Polish). Urban D., Wójciak H., Water rush plant associations of the Bug valley old river-bed (Kryłów-Kodeń section) versus the habitat conditions. Teka Kom. Ochr. Kszt. Środ. Przyr., 1, (in Polish).

9 AQUATIC PLANT COMMUNITIES OF THE LEMNETEA MINORIS Wójciak H., Urban D., Species of the Lemna, Spirodela i Wolffia in the Bug valley old river-beds Kryłów Kodeń stretch of the border (mscr.). Wołek J., Species co-occurrence patterns in pleustonic plant communities (class Lemnetea). Fragm. Flor. et Geobot. suppl., 5, 1-. Woyciechowska J., Dojlido J., Water quality classification of rivers. [In:] Dojlido J., Kowalczewski W., Miłaszewski R., Ostrowski J., (eds) The Bug river water and nature reserves. Wyd. IMiGW, WSzEiZ, Warszawa, pp (in Polish). ZBIOROWISKA WODNE Z KLASY LEMNETEA MINORIS R.Tx STARORZECZY DOLINY BUGU NA TLE WARUNKÓW SIEDLISKOWYCH Streszczenie. W 2003 r. rozpoczęto badania warunków siedliskowych i rozmieszczenia zbiorowisk wodnych z klas Lemnetea, Charetea i Potametea oraz szuwarowych z klasy Phragmitetea w kilkudziesięciu starorzeczach doliny Bugu (odcinek graniczny Kryłów Kodeń) [Urban i Wójciak 2004]. W latach badaniami objęto te starorzecza doliny Bugu, w których występowały fitocenozy z klasy Lemnetea minoris. PrzewaŜały asocjacje Spirodeletum polyrhizae (Kelhofer 1915) w. Koch em. R. Tx. Et a. Schwabe 1974 in r. Tx i Lemnetum trisulcae (Kelhofer 1915) Knappet Stoffers Rzadziej w badanych buŝyskach rozwijały się zespoły Wolffietum arrhizae Miyaw. Et j. Tx i Lemnetum gibbae Miv. Et j. Tx W próbkach wody i osadów pobranych ze starorzeczy (w miejscach występowania zbiorowisk z klasy Lemnetea minoris) oznaczono: ph oraz zawartość: fosforu, potasu, sodu, wapnia, magnezu i Ŝelaza, ponadto w próbkach wody przewodność elektrolityczną, a w osadach zawartość materii organicznej. Słowa kluczowe: starorzecza, dolina Bugu, zbiorowiska roślinne z klasy Lemnetea minoris, chemizm wód i osadów