Table 1.

Environmental characteristics of the Bohai Sea (mean ± SE)

Layer	PO43− (mg/L)	NH4+ (mg/L)	NO2− (mg/L)	SiO32− (mg/L)	NO3− (mg/L)	Chl a (µg/L)	Temp (T) (℃)	Salinity (S) (ppt)	Depth (D) (m)
Surface	0.0038 ± 0.0017b	0.0207 ± 0.0161b	0.0296 ± 0.0286	0.2927 ± 0.2163	0.1188 ± 0.1336	3.95 ± 2.61	26.15 ± 1.41a	28.27 ± 1.32	2.98 ± 0.38c
Middle	0.0048 ± 0.0021a	0.0289 ± 0.0161a	0.0310 ± 0.0213	0.3131 ± 0.1704	0.1103 ± 0.0846	2.91 ± 2.73	24.35 ± 3.02b	28.76 ± 1.32	10.97 ± 4.85b
Bottom	0.0044 ± 0.0019ab	0.0276 ± 0.0137ab	0.0358 ± 0.0233	0.3103 ± 0.1765	0.1242 ± 0.1011	3.02 ± 2.53	24.17 ± 3.16b	28.84 ± 1.28	21.24 ± 13.89a

Note The superscript letters represent the statistical differences between environmental characteristics at different water depths