钦州湾养殖区营养盐分布特征及富营养化状况研究

为了研究钦州湾养殖区的营养盐分布特征和富营养化现状、趋势和原因，于2018年冬季（2月）和夏季（8月）调查了钦州湾养殖区的营养盐及相应理化因子。结果显示，磷酸盐（PO₄3?）的浓度为3.7～40.0 μg/L，溶解性无机氮（DIN）浓度为41.1～664.8 μg/L ，其中，硝酸盐（NO₃?）占比最高（77%），其次是铵盐（NH₄+）（16%），而亚硝酸盐（NO₂?）占比最低（7%）。营养盐与理化因子的相关性和主成分分析显示，冬季陆源污染物输入是影响营养盐分布的主要因素，而夏季除了陆源输入外，生物过程对营养盐分布的影响不可忽视，这与夏季DIN和PO₄3?的浓度明显高于冬季的现象相对应。钦州湾养殖区水体的富营养化指数（ EI ）范围为0～19.65，平均为4.06，富营养化超标率为77%，其中，夏季水体富营养化程度高于冬季，处于中度富营养化状态。与近40年的历史数据相比，钦州湾水体富营养化状态呈显著增长趋势。与此相对应，钦州湾养殖区水体的N/P下降明显（低于Redfield值），其根本原因是磷排放的增加。

Study on the characteristics and eutrophication of nutrients in the mariculture farms of Qinzhou bay,South China

To study the distribution characteristics of nutrient and the status, trend and causes of eutrophication in the typical mariculture bay (Qinzhou bay, south China), the nutrients concentrations and other physicochemical parameters were investigated during two cruises in February (winter) and August (summer) 2018. The concentration of dissolved inorganic nitrogen (DIN) and phosphate (PO₄3?) ranged from 41.1～664.8 μg/L and 3.7～40.0 μg/L, respectively. Nitrate (NO₃?) was found to be the dominant component of DIN (accounting for 77% of DIN), followed by ammonium (NH₄+) (accounting for 16% of DIN) and nitrite (NO₂?) (accounting for 7% of DIN). According to the analysis of the correlation and principal component of nutrients and other physicochemical factors, the input of land-based pollutants was showed to be the dominant factor affecting the distribution of nutrient during the winter, while in summer, except for the input of land-based pollutants, the impact of biological processes on nutrient can not be ignored. The seawater quality of the bay was analyzed by eutrophication index ( EI ), and the results showed that the EI values ranged from 0～19.65 (average of 4.06), and the eutrophication degree in summer was higher than that in winter, which was at the moderate eutrophication. As the significant decrease of the N/P value compared with the historical data of nearly 40 years, the eutrophication status in Qinzhou bay was increasing significantly, which was due to the increase of phosphorus discharge for the past years.