Temporal and Spatial Variation of Nutrients and Evaluation of the Eutrophication in the Qingdao Lancelet Reserve Area in 2017

Abstract:

In this study, we have evaluated the level and distribution of nutrients in the Qingdao Lancelet Reserve Area using the results of surveys of the Qingdao Lancelet Reserve Area in September (Summer) and November (Autumn), 2017. The results showed that the average level of dissolved inorganic nitrogen (DIN) in the autumn was higher than that in the summer, and the average NO2-N and NH4-N levels were 1.98 and 1.44 times higher in the autumn than in the summer, respectively. However, the average NH4-N and PO4-P levels in the summer was about 88.8% and 47.6% of that in autumn, respectively. According to the seawater quality standard, in the summer the DIN content was better than the first-level seawater quality standard, and the PO4-P content was also better than the first-level seawater quality standard; in the autumn, the DIN content was better than the first-level seawater quality standard, and PO4-P content was worse than the first-level seawater quality standard. In terms of area distribution across the Qingdao Lancelet Reserve Area, the DIN concentration distribution trends of the seawater in the summer were core area > experimental area > buffer area; the DIN concentration distributions in the autumn seawater were buffer area > experimental area > core area. The distribution trends of PO4-P content in the summer seawater were experimental area > core area > buffer area. The distribution trends of the PO4-P content in the autumn seawater were core area > experimental area > buffer area. In the summer of 2017, the N/P ratio was the same as the Redfield ratio in the Qingdao Lancelet Reserve Area, but in the autumn of 2017, the N/P ratio was lower than the Redfield ratio, with relatively low levels of DIN. According to the potential eutrophication assessment model, the Qingdao Lancelet Reserve Area’s nutrition level was poor in both the summer and autumn of 2017. Generally speaking, the Qingdao Lancelet Reserve Area was at an oligotrophic level, and the seawater quality in the Qingdao Lancelet Reserve Area was good.