Nitrate and Nitrite Variability at the Seafloor of an Oxygen Minimum Zone Revealed by a Novel Microfluidic In-Situ Chemical Sensor.
Nitrate and Nitrite Variability at the Seafloor of an Oxygen Minimum Zone Revealed by a Novel Microfluidic In-Situ Chemical Sensor.
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DOI：
10.1371/journal.pone.0132785
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Sommer S
中科院分区：
文献类型：
--
作者：
Yücel M;Beaton AD;Dengler M;Mowlem MC;Sohl F;Sommer S
微流控，或芯片上实验室(LOC)是一项很有前途的技术，它允许开发微型化学传感器。与人们对生物医学科学的浓厚兴趣形成鲜明对比的是，LOC传感器在水产科学中的应用仍处于初级阶段，但更广泛地使用这类传感器可以缓解海洋生物地球化学过程中采样不足的问题。在这里，我们描述了一种新型的LOC型传感器的首次水下测试，该传感器在西非近海毛里塔尼亚氧气最低区的海底获得了硝酸盐+亚硝酸盐(ΣNOx)和亚硝酸盐的现场校准时间序列(长达40h)。初步测试表明，该传感器成功地再现了水柱(160米)的营养盐剖面。在50、100和170米深的着陆器部署表明，毛里塔尼亚大陆架上的生物地球化学变异性很高：50米处的ΣNOx浓度最低，为15.2至23.4μM(中位数为18.3μM)；而在100米处，ΣNOx在40小时内变化在21.0至30.1μM之间(中位数为25.1μM)。170m处的ΣNOx水平中位数最高(25.8μM)，变异性较小(22.8~27.7μM)。在50m处，亚硝酸盐浓度在短短30小时内从1μM下降到0.2DNA M，并伴随着氧气的减少和硝酸盐浓度的增加。结合氧气、温度、压力和流速的时间序列，我们认为，深水通过跨陆架输送的幕式入侵导致富硝酸盐但贫氧的水域侵入浅层，从而导致海底氮循环。在高水位下对LOC传感器的首次验证表明，当部署更长时间并作为传感器网络的一部分时，LOC技术有可能有助于理解底栖生物地球化学动力学。
Microfluidics, or lab-on-a-chip (LOC) is a promising technology that allows the development of miniaturized chemical sensors. In contrast to the surging interest in biomedical sciences, the utilization of LOC sensors in aquatic sciences is still in infancy but a wider use of such sensors could mitigate the undersampling problem of ocean biogeochemical processes. Here we describe the first underwater test of a novel LOC sensor to obtain in situ calibrated time-series (up to 40 h) of nitrate+nitrite (ΣNOx) and nitrite on the seafloor of the Mauritanian oxygen minimum zone, offshore Western Africa. Initial tests showed that the sensor successfully reproduced water column (160 m) nutrient profiles. Lander deployments at 50, 100 and 170 m depth indicated that the biogeochemical variability was high over the Mauritanian shelf: The 50 m site had the lowest ΣNOx concentration, with 15.2 to 23.4 μM (median=18.3 μM); while at the 100 site ΣNOx varied between 21.0 and 30.1 μM over 40 hours (median = 25.1μM). The 170 m site had the highest median ΣNOx level (25.8 μM) with less variability (22.8 to 27.7 μM). At the 50 m site, nitrite concentration decreased fivefold from 1 to 0.2 μM in just 30 hours accompanied by decreasing oxygen and increasing nitrate concentrations. Taken together with the time series of oxygen, temperature, pressure and current velocities, we propose that the episodic intrusion of deeper waters via cross-shelf transport leads to intrusion of nitrate-rich, but oxygen-poor waters to shallower locations, with consequences for benthic nitrogen cycling. This first validation of an LOC sensor at elevated water depths revealed that when deployed for longer periods and as a part of a sensor network, LOC technology has the potential to contribute to the understanding of the benthic biogeochemical dynamics.