How To Understand The Environment Of Lake Turowskie

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1 Limnological Review 6 An (2006): attempt to determine the trophic state of Lake Turowskie 277 An attempt to determine the trophic state of Lake Turowskie and the role of the catchment in the process of its eutrophication Renata Tandyrak, Mariusz Teodorowicz, Jolanta Grochowska University of Warmia and Mazury in Olsztyn, Chair of Engineering of Environmental Protection ul. Prawocheńskiego 1, Olsztyn Kortowo; renatat@uwm.edu.pl Abstract: Lake Turowskie is a small (7.2 ha) and shallow H max = 9 m), highly eutrophicated water basin located among morainal hills. A location in the catchment which is almost totally used for agricultural purposes (94.2%) and a multiyear sewage inflow from a nearby alcohol distillery caused its degradation. e actual biogene load amounting to 1.69 g P/m 2 /year and g N/m 2 /year has exceeded considerably the critical load calculated for this basin with the Vollenweider method (1968). e waters of the basin were characterized by very high concentrations of biogenous elements, reaching the values of 1.39 mg P/dm 3 and 8.2 mg N/dm 3, which stimulated its primary production manifesting itself with considerable concentrations of chlorophyll a (max mg/m 3 ), low water transparency (0.45 m) and overoxygenation ( % O 2 ) of the water layers. Key words: lake, catchment, eutrophication, sediments, external loading Introduction Eutrophication is a natural process occurring in lakes from the beginning of their existence. In the times when shortage of clean water was not sufferred drastically, it was even considered a favourable phenomenon (Starmach et al. 1976), however, nowadays mainly due to man s activity it has intensified rapidly. Medium substances are supplied to water basins not only as a result of outwashing from soil, dri ing by wind or as precipitation. Agriculture, recreation, transformation of natural environments, and, first of all, industry play a great part. A continuous inflow of organic matter building elements causes changes in hydrochemical properties of waters, leading to their total degradation both from the economic and aesthetical standpoint. e basic action which should be taken to neutralize this process consists in eliminating external sources of pollution by means of proper management of catchments and lake margins. Phosphorus is usually the element which determines the fertility of a lake and, connected with it, abundance of the occurrence of phytoplancton (Kajak 1998). e part which it plays and the fact that it most o en limits primary production, determines the necessity to focus special attention on the reduction of its content in lake waters. In the case of not severely degraded basins, a radical reduction of external phosphorus load, reaching 90%, can improve the environmental state of a lake; in other cases an improvement, if any, is not significant. In highly eutrophicated basins, in which sediments became the main source of phosphorus (Lijklema 1985, Shaw and Prepas 1990, Stauffer 1987), even such a radical reduction of the external load does not cause an expected improvement (Carvahlo et al. 1995, Marsden 1989, Van Liere and Janse 1992, Wagner 1997), and then reclamation becomes necessary. However, prior to that, the cause of progressing eutrophication should always be identified and protection action within the catchment should be taken. e aim of this thesis has been to determine the trophic state of Lake Turowskie and the contribution of the catchment to the progressing process of its eutrophication. e study was aimed at determining the possibility of lake reclamation.

2 278 Tandyrak R., Teodorowicz M., Grochowska J. e characteristics of the object of the study and its catchment Lake Turowskie is located south-east of the village of Turówek, at the altitude of m above sea level, in a basin among morainal hills of the maximum height of m above sea level. Its shape is prolate along the SE NW axis. It is a small water body, Choiński (1991) estimates its area at 7.5 ha (according to the author s measurements it has been estimated at 7.2 ha), with a regular and relatively hard. With a high level of the water, the maximum depth is 9 m (in the central part of the basin), and the mean depth is 3.8 m. e volume of the lake is small and amounts to around m 3. e basin has no permanent inflow or runoff. e catchment of the lake, which is ha in area, is typically agricultural the share of farm land amounts to 94.2%, a small part (4.5%) is occupied by woods, built-up areas constitute 1.2%, and marshland and water bodies 0,1% of its area. An alcohol distillery, curently inactive, is located in the village of Turówek. In spring 2002, the owner of the object made an attempt of its reclamation with the method of phosphorus inactivation, using aluminium sulfate as a coagulant. Unfortunately, a er introducing the first dose of it, further work was stopped. Material and method e basin research, covering all seasons of the lake year, was carried out within a year cycle from February 2001 to January Water samples for investigation were collected at one measurement site situated at the deepest place of the lake. Each time, visibility of Secchi disc was determined and the thermal and oxygen section was made every 1 m. e content of dissolved oxygen was measured by means of an oxygen probe. Water samples for other physico-chemical determinations were collected from the depth of 1, 4 and 8 m. Mineral and organic phosphorus was determined colorimetrically with ammonium molybdate and tin chloride (II) as a reducer, ammonium nitrogen was determined with the indophenol and distillation method, Kjeldahl nitrogen with the distillation method, total nitrogen was calculated as the sum of Kjeldahl nitrogen, nitrites (with the colorimetric method with sulphanilic acid and α-naphthylamine hydrochloride) and nitrates (colorimetrically with phenyldisulfonic acid), chlorophyll a was determined with the Strickland Parsons method. e size of the catchment and the way of its management were estimated by determining its water divide and computing the area with the help of a planimeter on a map in the scale of 1: e spatial flow of biogenes was calculated using coefficients given by Giercuszkiewicz-Bajtlik (1990). When calculating permissible and dangerous phosphorus and nitrogen loads, Vollenveider (1968) statistical model was used. Samples of sediments were collected from two sites. Site 1 was at the deepest place of the lake, site 2 was located opposite the alcohol distillery. e chemical constitution of the sediments was determined according to the methodology proposed by Januszkiewicz (1978), total phosphorus according to Golachowska (1977) a er burning in a mixture of acids H 2 SO 4 and HClO 4. Description of the findings Lake Turowskie is a small and relatively shallow basin located in a terrain depression and surrounded mostly by elevated banks, which limits the dynamics of its waters (Fig. 1). Summer stagnation was characterized by the presence of epilimnion with a thickness of 2 m in May, deepend to 3 m in a later period, metalimnion, covering with its range waters from 3 to 5-6 m deep with a maximum gradient 4,3 C/m, and volumetrically small hypolimnion. e actual range of epilimnion corresponded to the theoretical one calculated a er Patalas (1960) 2.74 m, which, according to the criterion of dependence between the effective length of the lake and the range of epilimnion allows to number it among lakes of the 4 th degree of static equilibrium. Mixing of waters down to the depth of 6 m was found out in October. An investigation carried out at the end of January showed the existence of thermal stratification typical of winter period. e dynamics of the waters of Lake Turowskie, as well as its fertility, were reflected in the aerobic systems being formed. e concentration of oxygen in epilimnion waters in May and June, and in the layer also in August, was high, and saturation reached % O 2. e highest oxygen saturation of the water layer was observed in May, and it was

3 An attempt to determine the trophic state of Lake Turowskie 279 Fig. 1. Seasonal variation of water temperature in Lake Turowskie Fig. 2. Seasonal variation of oxygen content in water of Lake Turowskie also then that the range of aerobic zone was the largest, vestigial amounts of this gas being found above the. During summer stagnation, there occurred oxygen exhaustion from the, expansion of the anaerobic zone range, and at the end of this period only epilimnion remained oxygenated (65% O 2 at the depth of 3 m). Incomplete autumn circulation did not cause oxygenation of waters. High oxygen saturation of the water layers during the summer stagnation is generally connected with algal blooms, which is accompanied by a high reaction, poor water transparency and high chlorophyll a concentrations. e water reaction recorded in that time reached the value of 9,3 ph (in autumn and winter it dropped to 7,0-7,2 ph). Visibility of Secchi disc was very low in the vegetation period, in June it amounted to only 0.4 m, and the amount of chlorophyll a measured then amounted to mg/m 3. e oxygen exhaustion progressing from the, leading to its complete decay, is the result of the processes of decomposition of organic matter supplied from the catchment, produced in the basin or deposited in sediments. Analyses of sediments showed a differentiation of their chemical constitution in different parts of the lake (Fig. 3). Deposits from site 2 were characterised by a definitely higher content of organic matter (34.01 %), as well as nitrogen (2.03%) and phosphorus (0.49%), compared to 15.29; 0.76; and 0.49 %, respectively, in site 1. Concentrations of total phosphorus in interstitial waters were fairly high, especially in the layer 0-5 cm (Fig. 4), reaching 4.46 mg P/dm 3 at site 1 and 8.31 mg P/dm 3 at site 2. In waters the concentrations of this element

4 280 Tandyrak R., Teodorowicz M., Grochowska J. Fig. 3. Chemical composition of the sediments in Lake Turowskie ranged from 0.34 to 1.39 mg P/dm 3. erefore, the occurring gradients were high, especially at site 2 (Fig. 4), which should be conducive to diffusive transporting of phosphorus to the lake waters (Tab. 1). Mineral phosphorus in water layers was found during the whole research period and remained a dominant form even in the peak period of summer stagnation. e concentrations of both mineral and total phosphorus in the layer of waters increased with the duration of summer stagnation, while they were the lowest in the spring. Similarly to phosphorus, mineral nitrogen was also constantly found in the basin waters, and its amounts were determined by the content of ammonia nitrogen or nitrate nitrogen in the layers, and by the content of ammonia nitrogen in the layers. Nitrite nitrogen occurred in small concentrations (maximally on the and mg N-NO 2 above the ), which practically had no impact on the total nitrogen content. e permissible and dangerous load for this lake, calculated according to Vollenweider criteria (1968) amounts to g P/m 2 /year and g P/m 2 /year, and g N/m 2 /year and 1.78 g N/m 2 / year, respectively. Actual external burden with biogenic substance load (Tab. 2) calculated on the basis of the catchment area, the way of its management and unit flow coefficients given by Giercuszkiewicz-Bajtlik (1990) amounted to 1.69 g P/m 2 /year and g N/ m 2 /year. It results from the comparison of these loads that biogenic elements flow exceeds both permissible and critical values many times. Fig. 4. Content of mineral P and total P in nthe over- waters, near- waters and interstitial waters of Lake Turowskie. Tab. 2. Total annual nutrients loading to Lake Turowskie calculated using unit run-off coefficients of Giercuszkiewicz-Bajtlik (1990). External sources of pollution Phosphorus (kg P/year) Tab. 1. Value of ranges of the selected physico-chemical water parameters of Lake Turowskie. Parameter Unit Layer Value Temperature O C 4 m Oxygen mg O 2 /dm 3 4 m Reaction ph 4 m Conductivity µs/cm 4 m Nitrate mg N/dm 3 4 m Ammonium mg N/dm 3 4 m Total N mg N/dm 3 4 m Mineral P mg P/dm 3 4 m Total P mg P/dm 3 4 m Nitrogen (kg N/year) 1. Spatial sources Atmospheric sources Total

5 An attempt to determine the trophic state of Lake Turowskie 281 Discussion e current trophic state of the lake is a consequence of a continuous process of primary production, which increases its organic matter burden. A er a certain time it exceeds the limits permissible for a given water body, leading, as a rule, to aerobic disturbances, and sometimes to complete deoxidation of the water environment due to oxygen consumption in the processes of decomposition of decaying organisms (Januszkiewicz 1975). Algal blooms also reduce visibility to a large degree. Low transparency values, like those noted in Lake Turowskie, are observed in high trophy water bodies (Lossow 1969, Mucha and Rybak 1979, Tandyrak 2004). Planning and carrying out effective activity aimed at neutralizing accelerated eutrophication of water bodies requires not only an identification of the ways of the inflow of eutroficating elements and estimation of the amount of supplied loads, but also getting to know the circulation of these elements in the basin ecosystem (Kajak 1995, Zdanowski et al. 1992). Only part of phosphorus, occurring in a dissoluble form in intersedimentary waters, is released from sediments. It is a small fraction in terms of quantity, but it is the most mobile one and it is exchanged directly with the lake water (Boström et al. 1982, Forsberg 1989). Concentrations of phosphorus in interstitial waters of Lake Turowskie were fairly high, particularly in the 0-5 cm layer (Fig. 4). e transmission of phosphorus from interstitial waters to higher-located over- waters is first of all determined by the concentration gradient on the water deposit border, gas convestion and bioturbulence being less important (Lappalainen 1982). Higher contents of organic matter, as well as those of nitrogen and phosphorus at the site located in the vicinity of the alcohol distillery can prove the influence of this facility on the formation of environmental conditions in the water body under discussion. On the basis of theoretical calculations and laboratory and field examinations it can be stated that Lake Turowskie is eutrophicated to a considerable degree. Anaerobic conditions prevailing in the water layers are conducive to releasing biogenic substances deposited in sediments, but the method of managing the catchment is of tremendous importance in supplying this basin with medium substances. From the standpoint of neutralizing eutrophication, closing the alcohol distillery, which was still active not long ago, is certainly a positive move, but area flows from the agriculturally used grounds, supplying excess amounts of nitrogen and phosphorus compounds from artificial fertilizers continue to be a serious problem in the case of the basin under discussion. An occurrence of high contents of mineral nitrogen during the whole vegetation period indicates high abundance of lakes in nitrogen, as well as continuously occurring processes of nitrification and mineralization of organic matter deposited in sediments. It is favoured by a high temperature of waters, observed in the waters of the described basin. e example of Lake Turowskie shows that reclamation action of any kind should be taken a er a thorough analysis of potential sources of pollution. e undertaken measures can give positive results only a er carrying out appropriate measures within the catchment and eliminating or significant reducing of the loads of biogenic compounds flowing from this area. It is noteworthy, which is indicated by Lossow et al. (1998), that every reclamation involves a risk of failure. Unquestionably, it must always be preceded by detailed lake research and determining the cause of eutrophication progress, as well as protective measures within the catchment. It should also take into account a unique nature of every water body. References Boström B., Petterson K Different patterns of phosphorus release from lake sediments in laboratory experiments. Hydrobiologia 92: Carvahlo L., Beklioglu M, Moss M Changes in a deep lake following sewage diversion a challenge to the orthodoxy of external phosphorus control as a restoration strategy? Freshwater Biol. 34: Choiński A., Katalog Jezior Polski. Część II: Pojezierze Mazurskie. Wyd. Nauk. UAM, Poznań. Forsberg G Importance of sediments in understanding nutrients cyclings in lakes. Hydrobiologia 176/177: Giercuszkiewicz-Bajtlik M Prognozowanie zmian jakości wód stojących, Instytut Ochrony Środowiska. Warszawa. Golachowska J Prosta i szybka metoda oznaczania fosforu całkowitego w osadach dennych jezior. Rocz. Nauk Rol., H 98: Januszkiewicz T Zagadnienie fosforu w eutrofizacji i ochronie wód. Gospodarka Wodna, 2:

6 282 Tandyrak R., Teodorowicz M., Grochowska J. Januszkiewicz, T Studium nad metodyką analizy współczesnych osadów dennych jezior. Zesz.Nauk. ART w Olsztynie, 8. Kajak Z Eutrofizacja nizinnych zbiorników zaporowych. Biblioteka Monitringu Środowiska, Łódź. Kajak Z Hydrobiologia Limnologia. Ekosystemy wód śródlądowych, PWN, Warszawa. Lappalainen M Convection in sediments and its role in material exchange between water and sediments. Hydrobiologia 86: Lijklema A Internal loading Mechanisms and assessment of magnitude. Lake Pollution and Recovery. Wat. Poll. Contr. Assoc., Rome: Lossow K Wpływ napowietrzania na chemizm wód Jeziora Starodworkiego. WSR Olsztyn (PhD esis) Lossow K., Gawrońska H., Tonder J Kryteria wyboru optymalnej metody rekultywacji zbiorników wodnych na przykładzie Jeziora Wolsztyńskiego, Bad. Limnol. 1: Marsden M.W Lake restoration by reduction external phosphorus loading: the influence of sediment phosphorus release. Freshwater Biol. 21: Mucha A., Rybak M Zawartość chlorofilu w fitoplanktonie Jeziora Długiego. Zesz. Nauk. ART. 9: Patalas K Mieszanie wody jako czynnik określający intensywność krążenia materii w różnych morfologicznie jeziorach okolic Węgorzowa, Rocz. Nauk Rol. 77: 1-15 Shaw J.F.H, Prepas E.E Relationship between phosphorus in shallow sediments and in the trophogenic zone of seven Alberta Lakes. Wat. Res. 24, Starmach K., Wróbel S., Pasternak K Hydrobiologia. Limnologia. PWN, Warszawa. Stauffer R.E Vertical nutrient transport and its effects on epilimnetic phosphorus in four calcareous lakes. Hydrobiologia 154: Tandyrak R Effect of Lake Starodworskie treatment by phosphorus inactivation on the primary production properties. Pol. J. Natur. Sc. 17, 2: Van Liere L., Janse J.H Restoration and resilience to recovery of the Lake Loosdrecht ecosystem in relation to its phosphorus flow. Hydrobiologia 233: Vollenweider R. A Scientific fundamentals of the eutrofication of lakes and flowing water, with particular reference to nitrogen and phosphorus as factor in eutrofication. Tech. Report Organization for Economic Cooperation and Development, Paris. Wagner K Lake and watershed management evaluation of Lake Elckie, Elk, Poland, EAPS Project. Zdanowski B., Karpiński A., Prusik S Warunki środowiskowe wód jezior Wigierskiego Parku Nardowego. Zesz. Nauk. PAN, 3: Streszczenie Badania prowadzono na niewielkim (7,2 ha), płytkim (H max =9 m), silnie zeutrofizowanym Jeziorze Turowskim, położonym w kotlinie, wśród wzgórz morenowych. Jego zlewnia jest niemal w całości (94,2%) użytkowana rolniczo, ponadto w pobliskiej wsi przez wiele lat funkcjonowała gorzelnia, odprowadzająca ścieki do omawianego zbiornika. Ograniczona dynamika wód Jeziora Turowskiego (ryc.1) (zbiornik o IV stopniu statyczności), a także jego żyzność miała swe odbicie w tworzących się układach tlenowych (ryc. 2). W okresie stagnacji letniej warstwa epilimnionu była nasycona tlenem w %, jednakże tylko w maju stwierdzano śladowe ilości tego gazu w warstwie naddennej. W pozostałych miesiącach obserwowano postępujące od dna odtlenienie wód, cyrkulacja jesienna także nie uzupełniła niedoborów tlenu w warstwach najgłębszych. Obliczone rzeczywiste obciążenie zewnętrzne ładunkiem substancji biogenicznych wynosiło 1,69 g P/m 2 /rok i 36,02 g N/m 2 /rok. Wartości te wielokrotnie przewyższają ładunki krytyczne wyliczone wg kryteriów Vollenweidera (1960). Wody Jeziora Turowskiego są zasobne w pierwiastki biogeniczne, a stężenia ich ogólnych form sięgały 1,39 mg P/dm 3 oraz 8,2 mg N/dm 3 (tab.1). Fosfor mineralny w powierzchniowych warstwach wód był obecny w ciągu całego okresu badawczego i pozostawał formą dominującą nawet w szczytowym okresie stagnacji letniej. Także azot mineralny występował stale w wodach zbiornika, a o jego ilości decydowała forma amonowa lub azotanowa. Istniejące w warstwach wód naddennych warunki beztlenowe uruchamiały zasilanie wewnętrzne wód w fosfor pochodzący z osadów dennych. Wyższą zawartością tego składnika, a także większym procentowym udziałem azotu i materii organicznej. charakteryzowały się osady ze stanowiska 2, zlokalizowanego w okolicach gorzelni (ryc. 3). W wodach międzyosadowych i nadosadowych na tym stanowisku obserwowano także wyższe stężenia fosforu mineralnego i ogólnego (ryc. 4). Tak wysoka zawartość biologicznie dostępnych form substancji biogenicznych sprzyjała występowaniu zakwitów glonów, co z kolei ograniczało przezroczystość wód do 0,4 m. Stężenia chlorofilu a sięgały 271,31 mg/m 3, odczyn wzrastał do 9,3 ph.