Wang Qin, Zhang Chao, Jin Haoyu, Chen Ying, Yao Xiaohong, Gao Huiwang
Key Laboratory of Marine Environment and Ecology, Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Ministry of Education of China, Qingdao, China.
Laboratory for Marine Ecology and Environmental Sciences, Pilot National Laboratory for Marine Science and Technology, Qingdao, China.
Front Microbiol. 2022 Jun 17;13:915255. doi: 10.3389/fmicb.2022.915255. eCollection 2022.
Atmospheric deposition can supply nutrients to induce varying responses of phytoplankton of different sizes in the upper ocean. Here, we collected surface and subsurface chlorophyll maximum (SCM) seawaters from the Yellow Sea and East China Sea to conduct a series of onboard incubation experiments, aiming to explore the impact of anthropogenic aerosol (AR, sampled in Qingdao, a coastal city in Northern China) addition on phytoplankton growth using schemes with (unfiltered seawater, UFS) and without (filtered seawater, FS) microsized (20-200 μm) cells. We found that AR addition stimulated phytoplankton growth obviously, as indicated by chlorophyll (Chl ) in surface incubations, and had stimulatory or no effects in SCM incubations, which was related to nutrient statuses in seawater. The high ratio of nitrogen (N) to phosphorus (P) in the AR treatments demonstrated that P became the primary limiting nutrient. The alkaline phosphatase activity (APA), which can reflect the rate at which dissolved organic P (DOP) is converted into dissolved inorganic P, was 1.3-75.5 times higher in the AR treatments than in the control, suggesting that AR addition increased P bioavailability in the incubated seawater. Dinoflagellates with the capacity to utilize DOP showed the dominant growth in the AR treatments, corresponding to the shift in phytoplankton size structure toward larger cells. Surprisingly, we found that nanosized (2-20 μm) and picosized (0.2-2 μm) Chl concentrations in UFS were generally higher than those in FS. The APA in UFS was at least 1.6 times higher than in FS and was proportional to the contribution of microsized cells to the total Chl , suggesting that microsized cells play an important role in the increase in APA, which contributes to the growth of nanosized and picosized phytoplankton. Current work provides new insight into the increase of P bioavailability induced by atmospheric deposition and resultant ecological effect in coastal waters.
大气沉降可以提供营养物质，从而引起上层海洋中不同大小浮游植物的不同响应。在此，我们从黄海和东海采集了表层和次表层叶绿素最大值（SCM）海水，进行了一系列船上培养实验，旨在利用含有（未过滤海水，UFS）和不含有（过滤海水，FS）微型（20 - 200μm）细胞的方案，探讨添加人为气溶胶（AR，在中国北方沿海城市青岛采集）对浮游植物生长的影响。我们发现，添加AR显著刺激了浮游植物的生长，表层培养中的叶绿素（Chl）表明了这一点，并且在SCM培养中具有刺激作用或无影响，这与海水中的营养状况有关。AR处理中氮（N）与磷（P）的高比例表明P成为主要的限制营养元素。碱性磷酸酶活性（APA）可以反映溶解有机磷（DOP）转化为溶解无机磷的速率，在AR处理中比对照高1.3 - 75.5倍，这表明添加AR增加了培养海水中P的生物可利用性。具有利用DOP能力的甲藻在AR处理中显示出优势生长，这与浮游植物大小结构向更大细胞的转变相对应。令人惊讶的是，我们发现UFS中纳米级（2 - 20μm）和微微米级（0.2 - 2μm）叶绿素浓度通常高于FS中的浓度。UFS中的APA至少比FS中的高1.6倍，并且与微型细胞对总叶绿素的贡献成正比，这表明微型细胞在APA增加中起重要作用，这有助于纳米级和微微米级浮游植物的生长。当前的工作为大气沉降引起的沿海水域P生物可利用性增加及其产生的生态效应提供了新的见解。
