象山港中部养殖海区营养盐的季节变化及富营养化

Seasonal Variation in Nutrients and Evaluation of Eutrophication in the Aquaculture Areas in the Middle Water Areas of Xiangshan Harbor

关键词:  象山港  营养盐  季节变化  富营养化

Key words:  Xiangshan Harbor  Nutrient  Seasonal variation  Eutrophication

摘要:

根据2014年11月，2015年1月、3月和7月在象山港中部养殖海区开展的海洋调查所获得的海水营养盐数据，分析了该海域营养盐含量的季节变化，评价了海水的富营养化状况。结果显示，该海域无机氮平均含量秋季最高，春季次之，冬季最低；活性磷酸盐平均含量秋季最高，夏季次之，冬季最低。对不同养殖区域分析，宁海海藻养殖区和西沪港海带养殖区的无机氮浓度除冬季1个站位点外均劣于国家海水四类水质标准(0.50 mg/L)，活性磷酸盐浓度在春、秋两季劣于国家海水四类水质标准(0.045 mg/L)。全年各水层的N/P比值均高于Redfield比值，磷相对缺乏。根据富营养化评价模式，象山港中部养殖海区营养水平属于磷中等限制潜在性富营养型。

Abstract:

Based on data from the aquaculture sea-areas of the middle part of Xiangshan Harbor surveyed in autumn of 2014, and spring, summer, and winter of 2015, nutrient levels and seasonal variation in nutrients were evaluated. The results showed that the inorganic nitrogen and phosphorus levels in autumn were higher than those in spring, summer, and winter. Among all regions, the DIN (Dissolved inorganic nitrogen) concentrations in Ninghai seaweed and Xihu Harbor kelp culture areas were higher than the fourth level of seawater standard (0.50 mg/L), except one sampling station in the winter. PO4-P content were higher than the fourth level of seawater standard (0.045 mg/L) in the spring and autumn. This may be due to human activity, which was focused on the development of local economy and urban upgrading. Additionally, the rivers that flowed through the metropolis around Xiangshan Harbor carried domestic wastewater and rainfall, consisting of superfluous inorganic nitrogen and inorganic phosphorus, to the sea water. Conversely, seaweed, as well as algae such as kelp, was originally cultivated to reduce the level of DIN and PO4-P, and has not functioned optimally during recent years, contradicting with the nutrient data from previous investigation. The N/P ratios of the sea water in the middle areas of Xiangshan Harbor were higher than the Redfield ratio in four seasons, lacking in inorganic phosphorus correspondingly. According to the potential eutrophication assessment model, Xiangshan Harbor possessed potential, rich nutrition, with medium levels of restricted phosphorus in four seasons.