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全球海洋上部及近岸水域同时发生着有机物的自养生产和异养降解两个方向相反的生物地球化学过程,自养生产即自养细菌和浮游植物利用无机态营养盐合成生产并最终释放有机物到水体中[1-2],而异养降解则是异养细菌选择性地降解水体中有机物并转化为无机态,这两个过程驱动着全球海洋营养物质循环[3]. 自生DON是指浮游生物食物网中病毒与死亡细胞自溶、海藻、浮游植物与细菌直接分泌和摄食浮游植物的原始与多细胞动物排泄释放的DON[4]. 外来DON是指通过大气沉降[5]、沉积物释放[6]和陆源输入[7]等方式进入到水体的DON.
本文采用2000—2014年在珠江口牛尾海每月水质调查监测结果,采用DIN和总溶解氮(TDN)浓度系列子集导出的数据来分析湾中DON浓度的时空变化,结合叶绿素-a (Chl-a)的实测结果,确定湾中DON滞留时间(TDON),利用二元混合质量平衡模式[8-9],结合盐度(S)实测数据,探讨研究自养生产和异养降解过程产生的剩余DON(ΔDON),研究湾中生物活动驱动氮循环机制及其碳源/汇特征.
珠江口牛尾海中DON的自养生产和异养降解
Autotrophic production and heterotrophic degradation of DON at the Niuweihai (Ngau Mei Hoi) area of the Pearl River Estuary
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摘要: 本文研究了珠江口牛尾海海域2000—2014年期间溶解有机氮(DON)月际变化与空间分布;并基于二维混合质量平衡模式,结合叶绿素a(Chl-a)估算该海域的DON滞留时间(TDON),评估自养生产和异养降解作用所产生的余量DON(ΔDON).结果显示,牛尾海海域中DON浓度约(0.118±0.056) mg·L−1,浮游植物生产的DON释放率约为27.1 g·g−1 (N /Chl-a),其TDON约为6 d,证实牛尾海海域是一个DON循环速率相对较快海域.牛尾海主湾区水域ΔDON接近于零,说明其DON的自养生产与异养降解接近平衡;湾顶水域ΔDON约0.010 mg·L−1,说明其DON自养生产占主导地位.总体上,牛尾海海域DON自养生产明显强于异养降解作用.Abstract: In the paper the monthly variations and spatial distributions of dissolved organic nitrogen (DON) were analyzed at the Niuweihai (Ngau Mei Hoi) area of Pearl River Estuary during 2000—2014.Based on the two-component mixing mass-balance model, the residence time of the DON (TDON) was also estimated combining with the data of chlorophyll a (Chl-a), in order to assess the net DON (ΔDON) from autotrophic production and heterotrophic degradation at the Niuweihai area, our results showed the DON concentration was (0.118±0.056) mg·L−1, and the DON release rate from the phytoplankton production was ~27.1 g·g−1 (N /Chl-a).The residence time (TDON) was about 6 days, suggesting that the DON cycle rate was fast at the Niuweihai area.The ΔDON concentration was close to zero, indicating the DON in main body waters was close to equilibrium between the autotrophic production and heterotrophic degradation.The ΔDON concentration was ~0.010 mg·L−1, indicating the autotrophic production of DON was stronger than the heterotrophic degradation at the bay’s top waters.In general, the autotrophic production of DON at the Niuweihai sea area was significantly stronger than heterotrophic degradation.
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Key words:
- DON /
- autotrophic production /
- heterotrophic degradation /
- the Pearl River Estuary /
- the Niuweihai area
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表 1 2000—2014年牛尾海中干季和湿季各监测站表层和底层平均T、S、pH、DO、Chl-a和DIN浓度a
Table 1. T,S,pH,DO,Chl-a and DIN concentrations averaged for surface- and bottom-waters at various sites for the dry and wet seasonsa at the Niuweihai area between 2000 and 2014
季节
Period站号
SiteT/°C S pH DO/(mg·L−1) Chl-a/(μg·L−1) DIN/(mg·L−1) 表层 底层 表层 底层 表层 底层 表层 底层 表层 底层 表层 底层 干季 PM1 20.9 20.6 32.6 32.6 8.1 8.1 6.9 7.4 3.3 3.0 0.053 0.054 PM2 20.9 20.7 32.5 32.6 8.1 8.1 6.9 7.2 3.0 2.9 0.059 0.062 PM3 20.9 20.5 32.6 32.7 8.1 8.1 7.1 7.1 2.9 2.5 0.055 0.067 PM4 20.7 20.5 32.6 32.6 8.1 8.1 6.8 7.3 2.8 3.0 0.050 0.052 PM6 20.9 20.6 32.4 32.6 8.1 8.1 7.0 7.1 3.1 2.4 0.064 0.070 PM7 20.8 20.5 32.6 32.8 8.1 8.1 7.1 7.1 2.2 2.1 0.061 0.075 干季 PM8 20.7 20.5 32.6 32.8 8.1 8.1 7.1 7.1 2.1 1.6 0.070 0.082 PM9 20.6 20.3 32.6 32.7 8.1 8.1 7.0 7.2 2.1 2.2 0.068 0.078 PM11 20.6 20.5 32.6 32.8 8.1 8.1 7.0 7.1 1.9 1.6 0.075 0.085 平均值 20.8 20.5 32.6 32.7 8.1 8.1 7.0 7.2 2.6 2.4 0.062 0.069 湿季 PM1 27.5 25.7 30.7 32.4 8.2 8.1 6.5 5.9 3.1 3.5 0.053 0.053 PM2 27.4 25.9 30.7 32.2 8.2 8.1 6.1 5.9 3.5 2.9 0.059 0.063 PM3 27.4 24.6 30.9 33.1 8.2 8.1 6.4 5.2 2.9 2.5 0.055 0.068 PM4 27.3 25.7 30.7 32.5 8.2 8.1 6.2 5.9 2.6 3.4 0.050 0.053 PM6 27.1 24.8 30.8 32.9 8.1 8.1 6.4 5.1 3.9 2.9 0.064 0.079 PM7 27.0 24.0 31.2 33.5 8.2 8.0 6.6 4.9 2.0 1.7 0.061 0.080 PM8 26.8 23.6 31.4 33.7 8.2 8.0 6.6 4.9 1.9 1.3 0.070 0.080 PM9 26.8 24.1 31.6 33.5 8.2 8.1 6.3 5.2 1.9 1.9 0.068 0.069 PM11 26.7 23.7 31.6 33.7 8.2 8.1 6.5 5.0 1.8 1.5 0.075 0.077 平均值 27.1 24.7 31.1 33.1 8.2 8.1 6.4 5.3 2.6 2.4 0.047 0.069 a干季指10月—翌年3月,湿季指4—9月. The dry season is Oct–Mar and the wet season is Apr–Sep. 表 2 2000—2014年牛尾海中DON的平均滞留时间
Table 2. Average residence times for DON at the Niuweihai area between 2000 and 2014
站号
Site水深/m
Water depthIDON/(g·m−2N) PP/(g·(m2∙d)−1C) TDON/d PM1 6 0.772 0.415 3.6 PM2 8 1.020 0.493 4.1 PM3 13 1.629 0.535 6.0 PM4 6 0.749 0.386 3.8 PM6 11 1.338 0.553 4.7 PM7 17 1.924 0.526 7.2 PM8 20 2.001 0.492 8.0 PM9 15 1.600 0.487 6.4 PM11 21 2.220 0.477 9.1 表 3 2000—2014年牛尾海中各测站的平均ΔDON和ΔDIN
Table 3. Average ΔDON and ΔDIN at various sites at the Niuweihai area between 2000 and 2014
站号
Site水深/m
Water depthΔDON/(mg·L−1) ΔDIN/(mg·L−1) PM1 6 0.013 −0.051 PM2 8 0.009 −0.043 PM3 13 0.013 −0.031 PM4 6 0.009 −0.050 PM6 11 0.008 −0.031 PM7 17 0.005 −0.016 PM8 20 −0.006 −0.006 PM9 15 −0.000 −0.013 PM11 21 0.000 −0.002 -
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