Reduction of nutrient emission from Polish territory into the Baltic Sea (1988–2014) confronted with real environmental needs and international requirements

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Average annual primary production [g C m−2 yr−1] in different regions of the Baltic Sea in 1954–2013 (source: Renk 2000 – publication of NMFRI; unpublished data of NMFRI)

Area	Study period	Primary Production	Author(s)
Kattegat	1954–1960	97.5	Steemann Nielsen 1965
	1964–1969	90.4	Gargas et al. 1978
	1988–1990	290	Richardson & Christoffersen 1991
Belt Sea	1953–1957	86	Steemann Nielsen 1965
	1975–1977	116.5	Gargas et al. 1978
Belt Sea – Sound	1972	70–77	Edler 1978
	1973	73–183
Belt Sea – Kiel Bight	1971–1793	158	Bodungen et al. 1975
Bornholm Basin – Arkona Deep	1971–1974	85	Renk 1983
	1967–1978	94.3	Schulz & Kaiser 1973 and 1976
Bornholm Basin – Mecklenburg Bight	1969–1978	130	Kaiser et al. 1981
Bornholm Basin – Bornholm Deep	1967–1972	59–138	Schulz & Kaiser 1974 and 1975
	1971–1975	95	Renk 1983
	1987–1991	123	Renk 1997
Gulf of Gdansk	1971–1974	140
	1987	304
	2004–2013	138–285	unpublished data, NMFRI
		average: 229
Gulf of Gdańsk – Puck Bay	1965–1991	198	Renk 1997
Gulf of Gdańsk – Gdansk Deep	1971–1974	107
	1981–1985	129
	1987–1991	172
Gotlańd Basin – Gotlańd Deep	1970	38	Schulz & Kaiser 1973
	1973	91	Ackefors & Lindahl 1975
	1974	116	Lindahl 1977
	1987–1991	141	Renk 1991 and 1997
Aland Sea	1974–1976	66–94	Lindahl 1977
Bothnian Bay	1973–1974	18–70
Gulf of Finland	1967–1971	30–65	Niemi 1975; Bagge & Niemi 1971
		78	Forsskåhl et al. 1982
Gulf of Finland – Helsinki area	1968	150–200	Bagge & Lehmusluoto 1971

Country allocation of nutrient load reduction acc_ to Country Allocated Reduction Target (CART) (HELCOM 2013a,b) and regional allocation of TP load reduction acc_ to Håkanson et al_ (2010)

Country	HELCOM (2013a,b) approach				Håkanson et al. (2010) approach
	CARTTN [tons yr-1]	CART TP [tons yr-1]	Percentage contribution		Region	TP [tons yr-1]	TN [tons yr-1]
			TN	TP
Denmark	2890	38	3.24	0.26	Bothnian Sea	Not needed	Reduction not recommended by the authors
Germany	7670	170	8.59	1.18
Poland	43 610	7480	48.86	52.04	Bothnian Bay	Not needed
Lithuania	8970	1470	10.05	10.23
Latvia	1670	220	1.87	1.53	Gulf of Finland	3180
Estonia	1800	320	2.02	2.23
Russia	10 380	3790	11.63	26.36	Gulf of Riga	550
Finland	3030	356	3.39	2.48
Sweden	9240	530	10.35	3.69	Baltic Proper	5000
Sum	89 260	14 374	100.00	100.00		8730

Annual primary production [g C m-2 yr-1] in various regions of the Baltic Sea and various periods of time (source: Renk 2000 – publication of NMFRI)

Area	Study period
	1971–1974	1981–1985	1987–1991	1994–1998
Gulf of Gdańsk (average value)	140	156
Gulf of Gdańsk (Gdansk Deep)	107	129	172	190
Bornholm Basin (Bornholm Deep)	82	91	123	164
Gotland Basin (Gotland Deep)	92	116	141	140
Słupsk Furrow	88	103

Combined flow normalized TN and TP loads discharged by the Vistula, the Oder, and the Pomeranian rivers in the reference period (1997–2003) and in 2012–2014, and the difference in loads in these two periods (yellow columns); maximum loads observed in 1992–1994 (TN) and 1988–1991 (TP), and the difference between maximum loads and those in 2012–2014 (green columns); allocation of load reduction acc_ to BSAP (HELCOM 2013b) (red column)

Nitrogen, phosphorus loads	In 1997–2003	In 2012–2014	Difference between 1997–2003 and 2012–2014	Maximal observed (years in brackets)	Difference between max. observed and 2012–2014	BSAP Poland
tons yr-1
TN	169648	140 372	29 276	209 243 (1992–1994)	68 871	43 610
TP	11 548	8990	2558	14 903 (1988–1991)	5913	7480

Eutrophication indicators in the brackish water systems (salinity 5–20 PSU) for four specified trophic states (source: Nixon 1995; Håkanson & Bryhn 2008)

Trophic state	Håkanson and Bryhn (2008)					Nixon (1995)
	Secchi depth	Chl-a	TN	TP	Cyanobacteria	Organic carbon supply
	m	μg l-1			μg wm l-1	g C m-2 yr-1
Oligotrophic	> 8	< 2	< 70	< 10	< 9.5	< 100
Mesotrophic	4.5–8	2–6	70–220	10–30	9.5–380	100–300
Eutrophic	1.5–4.5	6–20	220–650	30–90	380–2500	301–500
Hypertrophic	< 1.5	> 20	> 650	> 90	> 2500	> 500

Average combined flow normalized TN and TP loads, calculated for the reference period (1997–2003) for the Vistula and the Oder, and approximated for Polish rivers directly feeding the Baltic Sea, and target TN and TP concentrations at CART assumptions (Table 2); concentrations in brackets are offcially accepted maximum allowable values, meeting the good ecological status specified in WFD (Garcia et al_ 2012)

Average flow normalized TN loads	Average flow normalized TP loads	Target CART and max allowable WFD concentrations TN	Target CART and max allowable WFD concentrations TP	Target CART and max allowable WFD concentrations TN	Target CART and max allowable WFD concentrations TP
Vistula + Oder + other rivers		Vist		Oder
tons N yr-1	tons P yr-1	mg dm-3
94 794 + 57 220 + 17 634 = 169 648	6250+4116+1182= 11 548	2.06 target TN concentrations could be slightly lower if we took into account the reduction of direct atmospheric deposition to the Baltic Sea by Poland; (4.00)	0.067 (0.29)	2.57 target TN concentrations could be slightly lower if we took into account the reduction of direct atmospheric deposition to the Baltic Sea by Poland; (4.00)	0.083 (0.29)