桑沟湾养殖海域营养盐时空分布特征及富营养化评价

根据2014年10月、2015年3月、5月和8月在桑沟湾养殖水域开展的海洋调查所获取的营养盐状况调查数据,分析了营养盐含量的季节变化和平面分布,并对该水域营养水平状况进行了评价.结果显示,该海域秋季溶解无机氮(DIN)含量明显高于其他三个季节.夏季NO2-N的平均含量最高,秋季NO3-N的平均含量最高,春季NH4-N的平均含量最高,冬季PO4-P的平均含量最高.与海水水质标准相比,各季节DIN总体水平均低于海水一类标准值,春季和夏季PO4-P总体水平低于海水一类标准值,秋季和冬季PO4-P总体水平则高于海水一类标准值.从平面分布看,春季DIN含量呈湾内低、湾外高的趋势,夏季和秋季呈湾内高、湾外低的趋势,冬季呈自湾内南部水域向北逐渐降低的趋势.春季和冬季PO4-P含量均呈自湾内中部水域向外逐渐下降的趋势,夏季呈自湾内中部水域向外逐渐上升的趋势;秋季则呈湾内高、湾外低的趋势.春季、夏季和冬季N/P比值均高于Redfield比值,无机磷相对缺乏,而秋季N/P比值与Redfield比值基本一致.根据潜在性富营养化评价模式,桑沟湾养殖海域四个季节的营养水平较低,均属贫营养水平.与20世纪八九十年代相比,桑沟湾浮游植物生长的主要限制性因素已由整体的氮限制转变为春、夏季磷限制为主.

Temporal and Spatial Variation Characteristics of Water Nutrients and Eutrophication Evaluation in Aquaculture Water Areas of Sanggou Bay

In this study, based on the water nutrients data of Sanggou Bay surveyed in the autumn of 2014, and the spring, summer and winter of 2015, the seasonal variation and distribution of nutrients were analyzed and the nutrient levels were evaluated. The results showed that dissolved inorganic nitrogen (DIN) levels in the autumn of 2014 was the highest among four surveyed seasons. The average content of NO2-N and NO3-N was the highest during the summer and autumn, respectively. By comparison, the average contents of NH4-N and PO4-P were the highest during the spring and winter, respectively. Compared with the seawater quality standard, DIN contents in four seasons were lower than the levels in the first level of seawater standard. Active phosphate contents were lower than the first level of seawater standard in spring and summer, but were higher than first level of seawater standard in autumn and winter. From the perspective of horizontal distribution, the content of DIN of the inner bay was lower than that of the outer bay in spring, but was higher than those of the outer bay in summer and autumn. The content of DIN exhibited an increasing trend from the north to the south area during the winter. The content of PO4-P showed an increasing trend from the outer bay to the central area in spring and winter. Furthermore, the content of PO4-P showed a decreasing trend from the outer bay to the central area in summer, and the content of PO4-P of the inner bay was higher than that of the outer bay in autumn. The N/P ratio was the same as the Redfield ratio in autumn of 2014, and the N/P ratio was higher than the Redfield ratio in spring, summer and winter of 2015, with relatively low levels of inorganic phosphorus. According to the potential eutrophication assessment model, nutrition levels were relatively poor in the autumn of 2014, and the spring, summer and winter of 2015. Compared with the 1980s and 1990s data of Sanggou Bay, the main limiting factor for phytoplankton growth has changed from nitrogen to phosphorus limitation in spring and summer.