大亚湾水体营养盐分布特征及其生态环境效应

Distributions Characteristics of Nutrients in Sea Water and Its Ecological Environment Effects in Daya Bay

2019年秋季和2020年春季在大亚湾海域开展了生态环境现状调查,调查要素包括水温、盐度、pH、溶解氧、化学需氧量(COD)、溶解无机氮(DIN)、磷酸盐(DIP)、叶绿素a等。秋季DIN和DIP平均浓度分别为(5.00±3.36)、(0.31±0.56)μmol/L,春季分别为(3.12±1.97)、(0.13±0.05)μmol/L,春季DIN和DIP含量低于秋季。秋、春季DIN和DIP高值区均位于淡澳河入海口、哑铃湾和范和港湾口以及渔业养殖和港口交汇海域,且呈现自湾顶至湾口逐渐减小趋势,主要受入海径流、外海水入侵、渔业养殖、污水排放等多重因素影响。大部分海域处于贫营养化状态,仅湾顶局部海域为中度富营养化水平。春季叶绿素a平均值为(2.10±1.07)μg/L,大于秋季[(0.83±0.54)μg/L],秋、春季叶绿素a空间分布大体与营养盐相同,即湾顶高,湾中和湾口逐渐降低,秋、春季N/P平均值分别为30.52±20.09和26.68±17.70,湾顶浮游植物繁殖的主要限制因子为磷,湾口的主要限制因子为氮。

In autumn 2019 and spring 2020,the ecological environment status sruvey was carried out in the seawaters of Daya Bay,including water temperature,salinity,pH,dissolved oxygen(DO),chemical oxygen demand(COD),dissolved inorganic nitrogen(DIN),dissolved inorganic phosphorus(DIP)and chlorophyll a,etc.The average contents of DIN and DIP were(5.00±3.36)μmol/L and(0.31±0.56)μmol/L in autumn,and richer than(3.12±1.97)μmol/L and(0.13±0.05)μmol/L in spring.The high concentrations of DIN and DIP were in Danao river mouth,Yaling Bay and Fanhe Bay inner mouth,inersection of fishery breeding and ports,gradually declined from the bay s top to mouth,which were mainly influenced by runoff,seawater intrusion,fishery breeding and wastewater discharge.The most water areas of Daya Bay belonged to oligotrophical,only the bay s top was mesotrophical.The average contents of chlorophyll a was(2.10±1.07)μg/L in spring,and higher than(0.83±0.54)μg/L in autumn,but the chlorophyll a had similar spatial distributions to nutrients in spring and autumn.The mean ratio of N:P was 30.52±20.09 in autumn and 26.68±17.70 in spring,phytoplankton growth was controlled by phosphorus in the bay s top,gradually turning to be regulated by nitrogen in the bay s mouth.