TABLE 1.

Depth of SPM sampling and hydrological properties in the water column in the center of the western gyre of the Black Sea at sampling station PHOX2 in March 2013 and station 64PE418-4 in June 2017.

Year	Redox zone	Depth (mbsl)	O2 (μ mol kg–1)	HS– (μ M)	NO3– (μ mol L–1)	Salinity	Density
2013	Oxic	50	121	<DL	1.3	19.4	14.9
		70	2.2	<DL	2.5	20.1	15.7
	Suboxic	80	<DL	<DL	2.5	20.4	15.9
		85	<DL	<DL	0.3	20.5	16.0
		90	<DL	<DL	0.04	20.6	16.0
		95	<DL	<DL	0.04	20.8	16.1
		100	<DL	<DL	0.03	20.9	16.1
		105	<DL	<DL	0.03	20.9	16.2
		110	<DL	4.6	0.03	20.9	16.2
	Euxinic	130	<DL	15	<DL	21.1	16.4
		170	<DL	32	<DL	21.4	16.6
		250	<DL	85	<DL	21.7	16.8
		500	<DL	206	<DL	22.1	17.0
		1000	<DL	354	<DL	22.3	17.2
		2000	<DL	397	<DL	22.3	17.2
2017	Oxic	50	170	<DL	2.8	19.3	15.0
		55	115	<DL	3.6	19.5	15.1
		60	43	<DL	4.7	19.7	15.3
		70	5.9	<DL	3.0	20.2	15.6
	Suboxic	90	<DL	<DL	0.06	20.7	16.0
	Euxinic	130	<DL	<DL	<DL	21.2	16.4
		500	<DL	7.2	<DL	22.1	17.0
		1000	<DL	114	<DL	22.3	17.2
		1500	<DL	165	<DL	22.3	17.2
		2000	<DL	208	<DL	22.3	17.2

mbsl, meter below sea level. HS^– measurements taken in 2017 have been deemed unreliable as they are lower than those in 2013, possibly due to Niskin bottle leakage. Hence the redox zones for the 2017 depths were determined based on the similarity in the oxygen, nitrate, salinity, and density values between 2013 and 2017. DL, detection limit. For list of detection limits see Sollai et al. (2018).