Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health
Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health
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DOI：
10.5194/bg-7-1357-2010
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发表时间：
2010-01-01
期刊：
影响因子：
4.9
通讯作者：
Laane, R. W. P. M.
中科院分区：
文献类型：
--
作者：
Greenwood, N.;Parker, E. R.;Laane, R. W. P. M.
本文介绍了两年多来（2007年和2008年）部署在北海中部，在牡蛎理由和北方斜坡的多格银行（北多格）的仪表系泊高时间分辨率观测的新结果。水柱分层，在夏季在这两个网站，导致有限的交换的水在底部混合层。从这些系泊的数据显示，夏季氧气消耗的牡蛎理由的可变性质。现场测量和船载测量相结合，可以对导致底层水中溶解氧浓度下降的物理和生物条件进行检查。在2007年和2008年，在两个站点的底层水中的溶解氧的浓度被观察到整个夏季期间开始分层后下降。耗尽溶解氧浓度（6.5毫克升（-1），71%的饱和度）进行了测量，在北Dogger，一个网站，这是不显着的影响，人为的营养输入。低氧饱和度（5.2毫克l（-1），60%饱和度），测量了短时间内在牡蛎理由。底部水温的季节性增加占溶解氧浓度下降的牡蛎理由相比，10%在北Dogger.Dissolved在牡蛎理由的底层水中的溶解氧浓度的55%被证明是强烈的短期事件，包括风暴和脉冲颗粒有机物输入的影响。相比之下，溶解氧浓度在底层水在北Dogger反映了较长的季节性过程，如在夏季逐渐升温和更稳定的供应颗粒有机物的底部混合层。研究地点之间的差异表明，如果要在海洋管理和确保生态系统健康中使用氧气，就需要更好地了解推动这些过程的机制。这些高频率的观测提供了更好的理解在北海的底部氧浓度耗尽的性质。
This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central North Sea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger). The water column was stratified in the summer at both sites, leading to limited exchange of the water in the bottom mixed layer. Data from these moorings revealed the variable nature of summer oxygen depletion at the Oyster Grounds. The combination of in situ and ship-based measurements allowed the physical and biological conditions leading to decreasing dissolved oxygen concentrations in bottom water to be examined. In 2007 and 2008, the concentration of dissolved oxygen in the bottom water at both sites was observed to decrease throughout the summer period after the onset of stratification. Depleted dissolved oxygen concentration (6.5 mg l(-1), 71% saturation) was measured at the North Dogger, a site which is not significantly influenced by anthropogenic nutrient inputs. Lower oxygen saturation (5.2 mg l(-1), 60% saturation) was measured for short durations at the Oyster Grounds. The seasonal increase in bottom water temperature accounted for 55% of the decrease in dissolved oxygen concentration at the Oyster Grounds compared to 10% at North Dogger.Dissolved oxygen concentration in bottom water at the Oyster Grounds was shown to be strongly influenced by short term events including storms and pulses of particulate organic matter input. In contrast, dissolved oxygen concentration in bottom water at the North Dogger reflected longer seasonal processes such as a gradual temperature increase over the summer and a more steady supply of particulate organic matter to the bottom mixed layer. The differences between the study sites shows the need for an improved understanding of the mechanisms driving these processes if the use of oxygen in marine management and ensuring ecosystem health is to be meaningful and successful in the future. These high frequency observations provide greater understanding of the nature of the depletion in bottom oxygen concentration in the North Sea.