Development of Tools for Ecological Quality Assessment in Polish Marine Areas According to the Water Framework Directive

Home , Grabowa (river), Rega, Wieprza

Oceanological and Hydrobiological Studies International Journal of Oceanography and Hydrobiology Vol. XXXVIII, No.3 Institute of Oceanography (87-99) University of Gdańsk ISSN 1730-413X 2009 eISSN 1897-3191

DOI 10.2478/v10009-009-0037-1 Received: February 14, 2009 Original research paper Accepted: July 17, 2009

Development of tools for ecological quality assessment in Polish marine areas according to the Water Framework Directive. Part I – Nutrients

Elżbieta Łysiak-Pastuszak1, Włodzimierz Krzymiński, Łukasz Lewandowski

Institute of Meteorology and Water Management – Maritime Branch ul. Waszyngtona 42, 81-342 Gdynia, Poland

Key words: nutrients, eutrophication, response curves, ecological quality assessment, Baltic Sea

Abstract

Assessment of the ecological status of an aquatic environment according to the European Union Water Framework Directive (WFD) requires the determination of a link between the observed status of the marine ecosystem and catchment loading as well as the establishment of criteria for ecological status definitions. This article presents the results of a study identifying links between environmental pressures in the Polish sector of the Baltic Sea and state parameters applied in the assessment of eutrophication. Strong, statistically significant correlations were found between riverine loads of nutrients and their marine concentrations even in relatively short time data series.

1 Corresponding author: [email protected]

88 E. Łysiak-Pastuszak, W. Krzymiński, Ł. Lewandowski

INTRODUCTION

The Water Framework Directive (WFD) aims to achieve a good ecological status in all European rivers, lakes and coastal marine waters and demands that the ecological status is quantified based on biological indicators, i.e. phytoplankton and benthic flora and fauna (Anon. 2000). Nutrient concentrations, oxygen conditions or water transparency, the parameters traditionally applied to assess eutrophication, are treated as supportive ones. To implement the WFD it is necessary to develop and test methods that allow assessment of reference conditions, establish criteria for ecological status classification, and establish links between ecological status and catchment loading. In other words, it is necessary to develop a tool which, for a particular quality element, describes the correlation between environmental impact or anthropogenic pressure and effect, i.e. it is necessary to identify relevant environmental pressures for the construction of response curves or functional relations (Nielsen et al. 2002, Nielsen et al. 2003, Andersen et al. 2004). The implementation of WFD also requires an assessment of reference conditions as pristine, i.e. representing “the period without anthropogenic influence” (Schernewski&Neumann 2005), or, alternatively and more pragmatically, the best attainable conditions. By 2015 water bodies identified and categorized typologically (Schernewski&Wielgat 2004, Krzymiński et al. 2004) have to meet the standards of good ecological quality unless the area is heavily modified by human physical activity. This would require loading reduction, estimated in an action plan elaborated for the catchment area. Therefore, a classification of good, high, moderate, poor or bad status compared to reference conditions is essential for future planning and development of strategies for managing the environmental quality of groundwaters and surface water, including transitional and coastal marine waters. This series of contributions presents the results of a study identifying the links between environmental pressures in the Polish sector of the Baltic Sea and state parameters applied in the assessment of eutrophication.

MATERIALS AND METHODS

Assessment areas Traditionally eutrophication assessments of the Polish sector of the southern Baltic Sea focused on the characteristic regions (HELCOM 1987, 1990, 1993; Trzosińska&Łysiak-Pastuszak 1996, Łysiak-Pastuszak et al. 2004): the bays – the Gulf of Gdańsk in the east and the Pomeranian Bay in the west, the

Tools for ecological quality assessment. Part I – Nutrients 89 off-shore area - with distinguished regions of the Gdańsk Deep and SE Gotland Basin, and a coastal strip (delimited by 20 m bathyline according to the HELCOM definition of coastal areas (HELCOM 1997)) along the central Polish coast. Locations of the areas selected for the analyses in this study are shown in Fig. 1. The areas discussed in the present assessment are as follows (with codes for each station listed in parentheses): - Vistula River mouth section2 (ZN2), - internal Gulf of Gdańsk (NP, P114, P115, P110), - outer Puck Bay2 (KO, P102, P104), - Gdańsk Deep (P1, P116), - SE Gotland Basin (P140, P63), - central Polish coast (Z, L7, P16, K6, M), - open Pomeranian Bay (B13, B15, SK), - Oder River mouth section2 (Sw3).

Assessment data Nutrient reference values in the off-shore areas were determined on the basis of scarce historical data from the years 1938-1960 (Kijowski 1938, Głowińska 1962, Piątek 1962, Wiktor&Wiktor 1962, Trzosińska 1978) and the data collected in the oceanographic database of the Institute of Meteorology and Water Management in Gdynia between 1959 and 2004 (Łysiak-Pastuszak et al. 2004). The regular monitoring activities within the Polish sector of the southern Baltic Sea, related to HELCOM BMP, started in 1979 in the off-shore region, and were succeeded by the present HELCOM COMBINE programme in 1999 (IMGW, 1987-1999, 2000-2001). Since 1991 the HELCOM COMBINE in Poland has been included in the National Environmental Monitoring Programme. The data prior to that time were collected at random occasions within various scientific oceanographic projects (Majewski&Lauer 1994). The methodology regarding sampling and chemical determination of nutrients was carried out according to international marine chemistry guidelines (Grasshoff et al. 1976) and following the HELCOM manuals (HELCOM 1997; ICES 2004). The data on riverine nutrient loads - monthly mean values of riverine flows and nutrient concentrations between 1990 and 2005 - were supplied for the present assessment by Ośrodek Monitoringu Jakości Wód in Katowice (Katowice Branch of the Institute of Meteorology and Water Management). The measurements were carried out within the National Monitoring Programme of surface waters according to Polish Standard methods.

2 The areas form presently transitional water bodies according to WFD typology (Krzymiński et al. 2004).

www.oandhs.org

Fig. 1. Location of monitoring stations and assessment areas in the Polish sector of the Baltic Sea.

Tools for ecological quality assessment. Part I – Nutrients 91

RESULTS AND DISCUSSION

Reference conditions Reference conditions for eutrophication indicators in the marine environment have been determined for 1950 (HELCOM 2000). In the off-shore areas, the central Polish coast and the Gulf of Gdańsk, reference concentrations of dissolved phosphate (DIP) during winter were determined on the basis of scarce historical data (Łysiak-Pastuszak et al. 2006). In the cases of inorganic nitrogen (DIN = NO3 + NO2 + NH4), total nitrogen (TN) and total phosphorus (TP), the reference values have been determined by extrapolation of temporal trends (Łysiak-Pastuszak et al. 2004, HELCOM 2006), mainly for the data prior to 1985. Steep positive trends (statistically significant by t-Student test) in winter concentrations of oxidised nitrogen forms (TOxN) and dissolved phosphate (DIP) were discerned in the surface water layer (0-10 m) in the Polish bays between the end of the 1960s and 1988-1990; e.g.: Gulf of Gdańsk - DIP (<1984) tg α = +0.04 mmol m-3 a-1 (R2 = 0.24, p<0.05, n = 1 048); TOxN (<1984) tg α = +0.78 mmol m-3 a-1 (R2 = 0.35, p<0.02, n = 962); Pomeranian Bay - DIP (<1985) tg α = +0.12 mmol m-3 a-1 (R2 = 0.79, p<0.05, n = 188); TOxN (<1988) tg α = +1.39 mmol m-3 a-1 (R2 = 0.73, p<0.02, n = 189); tg α - slope of the regression curve (Łysiak-Pastuszak et al. 2004). The coastal (central Polish coast) and off-shore waters showed a significant increase in winter nutrient concentrations, though the detected trends were not statistically significant. In this case the reference values were derived using expert judgement by comparison of the medians and averages, utilizing the lower number as the reference value. Unfortunately, gaps in the data occur due to weather conditions, ship machinery or sampling gear break-downs, etc., and the data series on total nitrogen and phosphorus forms are much shorter in certain areas, starting only in 1999. This unevenness of data series has made the determination of temporal trends and functional relations difficult and sometimes impossible. The combined set of reference3 nutrient concentrations – DIP and DIN for the winter and TP and TN for the summer as proxies of productivity – are shown in Table 1. Although the presented reference values have been determined by a simplified statistical analysis, they are in good agreement with the Baltic-wide values established by more advanced modelling techniques

3 The determination of reference nutrient concentrations was carried out under various projects: WFD implementation in Poland (IMGW 2005), HELCOM EUTRO (HELCOM 2006) and EUTRO PRO, a project on thematic assessment of eutrophication in the Baltic Sea (HELCOM 2009).

www.oandhs.org

92 E. Łysiak-Pastuszak, W. Krzymiński, Ł. Lewandowski

Table 1

Reference conditions of nutrient concentrations determined in selected areas of the Polish sector of the southern Baltic Sea.

Geographical area Locality name DIN DIP DIN/DIP TN TP

Vistula river mouth section 10.00 0.70 14.3 15.00 0.90 Gulf of Gdańsk internal Gulf of Gdańsk 6.50 0.50 13.0 18.00 0.80 outer Puck Bay 5.50 0.40 16.3 18.00 0.70 Gdańsk Deep 4.00 0.25 16.0 14.00 0.60 Off-shore region SE Gotland Basin 2.50 0.25 10.0 14.00 0.60 Shallow area central Polish coast 4.00 0.35 11.4 13.00 0.60 open Pomeranian Bay 9.00 0.47 19.1 13.00 0.90 Pomeranian Bay Oder mouth section 15.00 0.70 21.0 18.00 0.90 DIN, DIP, TN and TP in [mmol m-3], DIN, DIP – mean winter (January-March) concentrations of nutrients in the upper (0-10 m) water layer, TN, TP – mean summer (June-September) concentrations of nutrients in the upper (0-10 m) water layer.

(Schernewski&Neumann 2005, HELCOM 2006). Nonetheless, the team working on the reference conditions expressed a strong opinion that the values should be verified by modelling or paleoecological research.

Response curves Functional relationships between nutrient inputs and marine nutrient concentrations were examined in relation to rivers’ direct impact areas; the Vistula River influencing the area of the Gulf of Gdańsk and Gdańsk Deep, and the Oder River influencing the Pomeranian Bay region. The summed up load of the Pomeranian Rivers (Łeba, Łupawa, Słupia, Wieprza, Grabowa, Parsęta, Rega and Ina), was presumed to have an impact on shallow coastal areas since their outlets are along the central Polish coast. The detailed list of identified functional relations (statistically significant) and their characteristics (formula, R – correlation coefficient, p – confidence limit and n – number of analysed data) is presented in Table 2. A strong, statistically significant, linear correlation was found between winter DIN concentrations in the surface (0-10 m) layer at station (ZN2), located in close proximity to the mouth of the Vistula River in the Gulf of Gdańsk, and annual mean DIN load discharged by the river (Fig. 2). The data series comprised the years 1987-2005. Analogous relations were found between the mean annual DIN concentration at this station and the Vistula River mean annual DIN load and consequently TN load. The direct impact of the Vistula River nitrogen load on concentrations in surface water along the Gulf of Gdańsk profile is well documented (Trzosińska&Łysiak-Pastuszak 1996, Łysiak-Pastuszak&Drgas 2002). The

Table 2

Functional relationships – statistically significant (at 95% confidence limit) linear correlations – found between riverine inputs and marine nutrient concentrations in the Polish marine areas. Geographical area Locality name Formula R, p, n Y [DIN(I-III)] = -9.1658 +0.0144*X [DIN Vist. a.m. load] 0.53, <0.55, 16 Vistula river mouth section Y [DIN (a.m.) = 1.8053 + 0.0052*X [DIN Vist. a.m. load] 0.57, <0.69, 18 Gulf of Gdańsk Y [DIN (a.m.) = 0.9439 + 0.0036*X [TN Vist. a.m. load] 0.63, <0.82, 18 Y [TP (V-IX) = 0.9415 + 0.0002*X [TP Vist. a.m. load] 0.92, <0.000, 6 outer Puck Bay Y [DIN (m.m.) = -0.3484 + 0.9585*X [DIN Vist. m.m.conc.] 0.35, <0.72, 49 Gdańsk Deep Off-shore region SE Gotland Basin st. L7: Y [DIP (a.m.) = 0.1042 + 0.0026*X [TP Pom. R. a.m. load] 0.58, <0.017, 15 Y [TP (a.m.) = 0.4957 + 0.0014*X [TP Pom. R. a.m. load] 0.72, <0.015, 9 Coastal area central Polish coast st. P16: Y [DIP (a.m.) = 0.1545 + 0.0021*X [DIP Pom. R. a.m. load] 0.51, <0.079, 15 Y [DIP (a.m.) = 0.2002 + 0.0006*X [TP Pom. R. a.m. load] 0.61, <0.012, 15 Y [DIN (a.m.) = -9.0728 + 0.0011*X [DIN Oder a.m. load] 0.73, <0.085, 17 open Pomeranian Bay Y [DIN (a.m.) = -11.4531 + 0.0008*X [TN Oder a.m. load] 0.62, <0.21, 13 Y [DIN (a.m.) = -23.1192 + 0.0025*X [DIN Oder a.m. load] 0.62, <0.21, 13 Pomeranian Bay Y [DIN (a.m.) = -25.5888 + 0.0017*X [TN Oder a.m. load] 0.60, <0.21, 13 Oder mouth section Y [TN (V-IX) = 8.0218 + 0.002*X [DIN Oder a.m. load] 0.82, <0.52, 6 Y [DIN (a.m.) = 6.3341 + 0.0014*X [TN Oder a.m. load] 0.82, <0.62, 6 a.m. – annual mean, m.m. – monthly mean, I-III – winter (January-March) mean, V-IX – extended summer (May-Septemebr) mean, Vist. – Vistula, Pom.R. – Pomeranian Rivers (Łeba, Łupawa, Słupia, Wieprza, Grabowa, Parsęta, Rega and Ina).

94 E. Łysiak-Pastuszak, W. Krzymiński, Ł. Lewandowski

Gulf of Gdańsk, st. ZN2 - V istula m outh se ction 70 y = -9.1658+0.0144*x; r= 0.53, p<0.55 (c.l. 95%), n=16

50 ] -3

30 DIN (I-III) [mmol m (I-III) DIN [mmol 20

0 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400

-1 DIN Vistula load [g s ] (annual mean) Fig. 2. Correlation between winter marine DIN concentrations in the surface water in the Gulf of Gdańsk and the annual mean riverine TN loads; data from 1987-2005. influence of the river with the growing distance from the mouth is marked in the decreasing correlation coefficients (R) between marine nitrate concentrations and riverine nitrate loads. At station ZN2 (the closest to the river mouth) R = 0.55, at station P116 (in the central part of the Gulf) R = 0.387 and at station P1 (in the Gdańsk Deep at a distance of about 50 Nm from the land) R = 0.36. No statistically significant correlations were found between marine phosphorus forms and riverine inputs along the Vistula plume. The influence of the Vistula is also very pronounced in the western part of the Gulf of Gdańsk, opposite to the natural (Coriolis effect and Ekman transport) spreading of the plume. A statistically significant correlation was found between summer TP concentrations at station KO (located in the outer Puck Bay, a transitional water body) and mean annual TP load from the river (Fig. 3), although the examined data series were quite short and covered only the period 1999-2005. A similar relationship was determined in this area for marine DIN monthly data and Vistula TN monthly mean concentrations (Table 2). It is worth noting that the linear correlation between marine DIP concentrations and riverine input from the Pomeranian Rivers was documented at two distant stations along the central Polish coast (Table 2).The example from station Ł7 is shown in Fig. 4.

Tools for ecological quality assessment. Part I – Nutrients 95

Gulf of Gdańsk, st. KO 1.06 y = 0.9415+0.0002*x; r=0.92, p<0.000 (c.l. 95%), n=6 1.05

1.04 ] -3 1.03

1.02

1.01

1.00 TP m (V-IX mean) [mmol

0.99

0.98

0.97 250 300 350 400 450 500 550 600 650

-1 TP Vistula load [g s ] (annual mean) Fig. 3. Correlation between summer marine TP concentrations at high frequency station KO in the Gulf of Gdańsk (“outer Puck Bay” water body) and Vistula River annual mean TP loads; data from 1999-2005.

Central coast, st. Ł7 0.55 y = 0.1042+0.0026*x; r=0.58, p<0.017 (c.l. 95%), n=15

0.50 ]

-3 0.45

0.40

0.35

DIP (annual mean) [mmol m mean) (annual DIP [mmol 0.30

0.25

0.20 50 60 70 80 90 100 110 120 130

-1 TP Pomeranian Rivers load [g s ] (annual mean) Fig. 4. Correlation between annual mean marine DIP concentrations in the surface water along the central Polish coast and the Pomeranian Rivers’ annual mean TP loads; data from 1990-2005.

www.oandhs.org

96 E. Łysiak-Pastuszak, W. Krzymiński, Ł. Lewandowski

Along the central Polish coast, at station P16, a similar correlation (marine DIP vs. rivers’ TP) was also detected (see Table 2). Contrary to the areas in closer proximity to the rivers’ mouths, no statistically significant correlations were found between marine DIN or TN concentrations and the Pomeranian Rivers’ inputs, meaning that other sources of nitrogen input play a major role here. Regarding the Oder River influence on nutrient concentrations in the Pomeranian Bay, two areas were examined: the Oder River mouth section - covering the closest proximity to the river mouth and corresponding to the typologically delineated transitional water body (Krzymiński et al. 2004), and the open bay area (Fig. 1). In both areas, statistically significant correlations were found between marine DIN concentration and Oder DIN annual mean load (Fig. 5, Table 2). In the Pomeranian Bay correlations between phosphorus forms in the seawater and riverine input were not found. Because of the short data series and their estimation in the already strongly eutrophied environment, none of the identified empirical correlations showed clear thresholds or break points that would indicate system degradation or recovery and support status boundary setting.

Pomeranian Bay, st. B13 40

y = -9.0728+0.0011*x; r=0.73, p<0.085 (c.l. 95%), n=17 35

30 ] -3

15 DIN (annual mean) [mmol m DIN mean) (annual [mmol 10

0 8000 10000 12000 14000 16000 18000 20000 22000 24000 26000 28000

-1 DIN Oder load [g s ] (annual mean) Fig. 5. Correlation between annual mean marine DIN concentrations in the surface water in the open part of the Pomeranian Bay and the annual mean DIN load from the Oder River; data from 1990-2005.

Tools for ecological quality assessment. Part I – Nutrients 97

Boundary setting The management objectives in the EU Water Framework Directive are to achieve at least good ecological status and to maintain existing high and good status in all surface waters across Europe including marine transitional and coastal waters (Anon. 2000). The border between good and moderate ecological status is the line at which measures have to be taken in order to improve any lower ecological status. The normative definitions of WFD clearly state that moderate status is determined when the values of biological quality elements or supporting physico-chemical quality elements deviate moderately from those associated with the marine water body type under undisturbed conditions (reference level). Hence, the border between good and moderate status can be considered synonymous with the acceptable deviation from reference conditions. Ideally, the acceptable deviation and other class boundary values should be determined on the basis of response curves which describe in quantitative terms the response of the ecosystem to disturbances. However, this would require ample and long-term data on both pressure and state parameters and which are rarely available. In the first application (OSPAR 1997, Ærtebjerg et al. 2003), the acceptable deviation was expressed as a percentage deviation from reference conditions and was set to 50%. During the HELCOM EUTRO project (HELCOM 2006) the preliminary eutrophication assessment of selected areas of the Baltic Sea was carried out on the basis of nutrient data using 50% as the acceptable deviation from the reference level for the border between good and moderate classes. Within the project other options were followed as well, e.g. 34% and 40% for water transparency in the Gulf of Riga and 25% was accepted as a general rule by Denmark, with 50% considered the absolute maximum. In Polish legislation (Anon. 2008), the border between good and moderate status for nutrients in transitional and coastal waters was arbitrarily set at 50%. The idea of acceptable deviation might have little meaning, therefore it is important to link the changes in the marine ecosystem, e.g. illustrious changes in benthic vegetation occurring due to the increasing eutrophication status (Nielsen et al. 2002). Nonetheless, 50% deviation should be considered a much too mild criterion in the case of a pressure factor and it is more justified to apply 25% deviation as the border between good and moderate ecological status, following the example of Denmark (Æertebjerg et al. 2003).

www.oandhs.org

98 E. Łysiak-Pastuszak, W. Krzymiński, Ł. Lewandowski

ACKNOWLEDGEMENT

This series of articles was prepared as a Polish contribution to the HELCOM EUTRO PRO project (Eutrophication in the Baltic Sea – an integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea Region) within statutory activities of IMGW, theme DS-O.3, financed by the Polish Academy of Sciences.

REFERENCES

Ærtebjerg G., Andersen J.H., Hansen O.S., (eds.), 2003, Nutrients and Eutrophication in Danish Marine Waters – A Challenge for Science and Management. Ministry of the Environment, National Environmental Research Institute, 2003, 126 pp. Andersen J.H., Conley D.J., Hedal S., 2004, Palaecology, reference conditions and classification of ecological status: the EU Water Framework Directive in practice, Marine Pollution Bulletin, 49: 283-290 Anon., 2000, Directive 200/60/EC of the Europen Parliament and the Council Establishing a Framework for Community Action in the Field of Water Policy. Legislative Acts and other instruments, ENV221 CODEC 513. European Union Głowińska A., 1963, Phosphate in the southern Baltic Sea betweeen 1947-1960, Prace Morskiego Instytutu Rybackiego, T.12/A: 7-21 (in Polish) Grasshoff K., Ehrhardt M., Kremling K., 1976 (1st ed.), 1983 (2nd ed.), Methods of seawater analysis, Verlag Chemie GmbH, 419 pp. HELCOM, 1987, First periodic assessment of the state of marine environment of the Baltic Sea, 1979-1983, Background document, Balt. Sea Environ. Proc., No. 17B: 351 pp. HELCOM, 1990, Second periodic assessment of the state of marine environment of the Baltic Sea, 1984-1988. Background document, Balt. Sea Environ. Proc., No. 35B: 428 pp. HELCOM, 1993, First assessment of the state of the state of coastal waters of the Baltic Sea, Balt. Sea Environ. Proc., No. 54: 155 pp. HELCOM, 1997, Manual for Marine Monitoring in the COMBINE Programme of HELCOM, http://sea.helcom.fi/Monas/CombineManual2/CombineHome.htm HELCOM, 2000, HELCOM Workshop on Background Concentrations. Summary Record, Stockholm, 9-11 October 2000, 29 pp. HELCOM, 2006, Development of tools for assessment of eutrophication in the Baltic Sea, Balt. Sea Environ. Proc. No. 104: 62 pp. HELCOM, 2009, Eutrophication in the Baltic Sea – An integrated thematic assessment of the effects of nutrient enrichment and eutophication in the Baltic Sea region, Balt. Sea Environ. Proc., No. 115B, 148 pp. ICES, 2004, Chemical measurements in the Baltic Sea: Guidelines on quality assurance, Ed. by E. Łysiak-Pastuszak and M. Krysell. Techniques in Marine Environmental Sciences, No. 35: 149 pp. IMGW, 1987-1999, Environmental conditions in the Polish zone of the southern Baltic Sea in 1986 (.....1998). B. Cyberska, Z. Lauer, A. Trzosińska (red.), IMGW - Materiały Oddziału Morskiego, Gdynia 1987-1999 (in Polish with Engl. summ.) IMGW, 2000-2001, Environmental conditions in the Polish zone of the southern Baltic Sea in 1999 (.....2001). W. Krzymiński, E. Łysiak-Pastuszak, M. Miętus (red.), IMGW - Materiały Oddziału Morskiego, Gdynia 2000-2001 (in Polish with Engl. summ.)

Tools for ecological quality assessment. Part I – Nutrients 99

IMGW, 2005, Determination of reference conditions appropriate to surface water types according to Annex II to of the Water Framework Directive 2000/60/UE. Opracowanie na zlecenie Ministerstwa Środowiska, Raport z prac, 36 pp. (mimeogr. in Polish) Kijowski S., 1938, Hydrological characteristics of the Gulf of Gdańsk - Die Charakteristik der Danziger Bucht in hydrologischer Beziehung, Bulletin Météorologique et Hydrographique publié par L’Institut National Météorologique de Pologne avec cartes et graphiques, 4-9: 26- 38 (in Polish with German and French resume) Krzymiński W., Kruk-Dowgiałło L., Zawadzka-Kahlau E., Dubrawski R., Kamińska M., Łysiak- Pastuszak E., 2004, Typology of Polish marine waters, Coastline Reports: Baltic Sea Typology, 4: 39-48 Łysiak-Pastuszak E., Drgas N., 2002, Part XV – Marine environment and Baltic Sea coastal zone. Major pollution sources to the Baltic Sea, [in:] Rudlicka A., Krzymiński W., Łysiak- Pastuszak E. (eds.) Report – status of natural environment in Poland between 1996-2002, Biblioteka Monitoringu Środowiska, Warszawa, IOŚ, 2003, 143-156 (in Polish) Łysiak-Pastuszak E., Drgas N., Piątkowska Z., 2004, Eutrophication in the Polish coastal zone: the past, present status and future scenarios, Marine Pollution Bulletin, 49: 186-195 Łysiak-Pastuszak E., Osowiecki A., Filipiak M., Olszewska A., Sapota G. et al., 2006, Preliminary assessment of the eutrophication status of selected areas in the Polish sector of the Baltic Sea according to the EU Water Framework Directive, Oceanologia, 48 (2): 213- 236 Majewski A., Lauer Z. (eds.), 1994, Baltic Sea Atlas, Instytut Meteorologii i Gospodarki Wodnej, Warszawa 1994, 214 pp. (in Polish with Engl. summ.) Nielsen S.L., Sand-Jensen K., Borum J., Geertz-Hansen O., 2002, Phytoplankton, nutrients and transparency in Danish coastal waters, Estuaries, 25 (5): 930-937 Nielsen K., Smød B., Ellegaard Ch., Krause-Jensen D., 2003, Assessing reference conditions according to the European Water Framework Directive using modelling and analysis of histroical data: an example from Renders Fjord, Denmark. Ambio, 32(4): 287-294 OSPAR, 1997, Oslo and Paris Commissions for the prevention of marine pollution. Joint meeting of the Oslo and Paris Commissions (OSPAR), Brussels, 2-5 September 1997, Summary Record (OSPAR 97/15/1) Piątek W., 1962, Preliminary results on phosphate (P2O5) in the southern Baltic between 1948- 1954, Prace Morskiego Instytutu Rybackiego w Gdyni, T.11/A: 6-79 (in Polish) Schernewski G., Neumann T., 2005, The trophic state of the Baltic Sea a century ago: a model simulation study, J. Mar. Sys., 53: 109-124 Schernewski G., Wielgat M., 2004, Towards a Typology for th Baltic Sea, G. Schernewski & N. Löser (eds.) Managing the Baltic Sea. Coastaline Reports, 2:35-52 Trzosińska A., 1978, Factors controlling the nutrient balance in the Baltic Sea. Productivity of the Baltic Sea, Polska Akademia Nauk – Komitet Badań Morza, Ossolineum, 25-51 Trzosińska A., Łysiak-Pastuszak E., 1996, Oxygen and nutrients in the southern Baltic Sea, Oceanological Studies, 25(1-2): 41-76 Wiktor K., Wiktor J., 1962, On some hydrological properties of the Pomeranian Bay, Prace Morskiego Instytutu Rybackiego w Gdyni – Nr 11/A, Wydawnictwo Morskie, Gdynia 1962, 113-136 (in Polish)