秋季珠江口外海海域的生态环境特征

于2015年9月（秋季）对珠江口外海海域不同深度水体中的营养盐、溶解氧（DO）和叶绿素a（Chl a）进行了调查，通过分析它们的空间分布特征及相互关系对珠江口外海海域的生态环境进行了研究。调查期间，营养盐、DO和Chl a的浓度和分布情况表明珠江口外海海域的生态环境总体较好，该区域的近岸受一定程度的陆源影响。在垂直分布上，珠江口外海海域水体的温度和盐度层化明显，导致营养盐、DO和Chl a的垂直分布均出现明显的差异。珠江口外海海域浅层水体（约小于50 m）的营养盐由于受浮游植物光合作用的影响而具有较低的浓度，深层水体（约大于50 m）的营养盐由于受有机物氧化分解的影响而具有较高的浓度。基于营养盐浓度和比值初步判断调查区域的营养盐限制情况，发现珠江口外海海域大部分浅层水体的营养盐可能同时存在氮限制和磷限制。综合分析营养盐、DO和Chl a之间的关系，发现2015年秋季珠江口外海海域的水体整体上处于异化作用占主导的阶段。

Characteristics of the ecological environment in the seawater off the Pearl River estuary in autumn

Nutrients, dissolved oxygen and chlorophyll a (Chl a) in different layers of the seawater off the Pearl River estuary were investigated in September 2015. Distribution patterns and relationships of these parameters were analyzed to study the ecological environment characteristics in this area. The results showed that the seawater ecosystems off the Pearl River estuary were generally in a good condition with the low concentrations of nutrients and Chl a, and the appropriate dissolved oxygen level. Their distribution patterns showed that the nearshore waters were influenced by river runoff to some extent. Because of the stratified water temperature and salinity, nutrients, dissolved oxygen and Chl a showed obvious vertical variations. Shallow waters (<~50 m) off the Pearl River estuary had relatively low concentrations of nutrients because of the photosynthesis of phytoplankton, while the deep waters (>~50 m) off the Pearl River estuary had generally high nutrient concentrations due to the release of nutrients from organic matter decomposition. Based on nutrient concentrations and their ratios, we found the phytoplankton growth in most of the shallow waters (<~50 m) off the Pearl River estuary may suffering both N and P limitation during the investigating period. The relationships among nutrients, dissolved oxygen and Chl a manifested that the water system off the Pearl River estuary in autumn was dominated by dissimilation processes.