Investigation and analysis of ecological environment in the north of Bohai Sea

In order to investigate the ecological environment of Tangshan offshore breeding area (in the north of Bohai Sea), water quality and phytoplankton were investigated and monitored in two consecutive years (2019 and 2020). To evaluate and analyze the water condition of the breeding area, we used the nutrition index (E), Nutritional status quality index (NQI), organic pollution assessment index (A), Biodiversity Index (H’) and Integrated environmental quality index (EQI). The result showed that the range of E was 0.01∼0.97 in May (2019), 0.14∼0.59 in August(2019), 0.25∼0.63 in December(2019), 0.04∼1.21 in August(2020); the range of A was 0.39∼1.33 in May(2019), 0.73∼1.16 in August(2019), 0.87∼1.19 in December(2019), -0.15∼2.33 in August(2020); the range of H was 0.84∼2.11 in May(2019), 1.07∼1.21 in August(2019), 1.92∼2.86 in December (2019), 0.71∼1.47 in August(2020). By calculation, EQI was 94.34 in 2019 and 100 in 2020. The results showed that the nutrient level of the culture area was generally low, and it was in poor nutrition state. The phytoplankton diversity in summer was better than that in spring and winter. The organic pollution degree of the water area was low, but the water quality was good. In conclusion, the environmental quality of aquaculture area was good, which could meet the requirements of functional area.