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Long term trend in seawater nutrient (μM) and COD (mg/L) content in the northern Beibu Gulf. Data are means ±SD.
| Year | DIN | NO3 | NO2 | NH4 | PO4 | SiO3 | COD |
|---|---|---|---|---|---|---|---|
| 1980s | 1.7 ± 1.9 | 2.1 ± 2.4 | 0.07 ± 0.05 | 1.5 ± 0.4 | 0.6 ± 0.2 | 23.5 ± 28.5 | 1.2 ± 0.9 |
| 1990s | 14.2 ± 13.8 | 9.3 ± 11.9 | 0.37 ± 0.39 | 2.7 ± 2.5 | 0.3 ± 0.3 | 28.2 ± 27.5 | 1.8 ± 1.0 |
| 2000s | 19.4 ± 17.8 | 20.4 ± 16.5 | 1.72 ± 1.66 | 2.7 ± 2.8 | 0.4 ± 0.4 | 31.4 ± 38.6 | 1.8 ± 1.0 |
| 2010s | 29.9 ± 21.9 | 26.5 ± 20.2 | 2.43 ± 2.55 | 4.0 ± 2.9 | 0.6 ± 0.5 | 33.6 ± 29.6 | 1.6 ± 1.0 |
