海洋酸化与光照耦合效应对海洋光合有机物光学与化学特性的影响

有机物光学与化学特性是影响有机物在上层海洋光化学活性和微生物可利用性的内在因素，也是表征海洋生物泵碳埋藏效率的重要指标。人类活动导致大气CO2不断升高，引起海洋酸化现象，并进一步影响海洋初级生产力，而这一效应还与光照强度密切相关。海洋酸化与光照耦合如何改变光合有机产物的化学与光学特性，进而影响有机物的降解活性及碳埋藏效率，是需要深入研究的科学问题。因此，本课题拟以实验室（中肋骨条藻和多尼骨条藻）与现场（东海陆架海）培养相结合，采用吸收光谱与荧光光谱等技术，探讨海洋酸化与光照耦合对：（1）海洋光合有机物元素组成（C:N）及溶解有机碳（DOC）与颗粒有机碳（POC）生产速率比的影响；（2）颗粒有机物（POM）与溶解有机物（DOM）吸收光谱特性的影响；（3）DOM分子组成变化的影响。本研究从有机物光学与化学特性入手，可为认识酸化与光照耦合效应对我国近海有机碳、氮循环的潜在影响提供新的视角与思路。

The optical-chemical characteristics of marine organic matter influence its photochemical reactivity and bioavailability, which could also be used to characterize the carbon sequestration efficiency of the marine biological pump. The enhanced atmospheric CO2 concentration by anthropogenic activities during the past decades has caused acidification in the upper ocean, which sequentially influences the marine primary production. Furthermore, the effect of ocean acidification is related with light intensity. Thus, more attention is needed to be paid on how the synergetic effects of ocean acidification and light intensity impacting on the chemical and optical characteristics of photosynthetic organic matter, and hence influencing the degradation reactivities of organic matter as well as the carbon sequestration efficiency. So, in this study, lab-based incubation of monocultures of Skeletonema costatum and Skeletonema dohrnii, isolated from Chinese coastal sea, will be conducted under enhanced CO2 level coupled with varied light intensities, as well as in situ incubation in the coastal East China Sea. The absorbance spectra of photosynthetic dissolved and particulate organic matter (DOM and POM) and the fluorescence spectra of DOM will be analyzed to evaluate the synergetic impacts of ocean acidification and light intensity on: (1) the stoichiometry (C:N) of POM and DOM and the ratio of the production rates of dissolved and particulate organic carbon (DOC and POC); (2) the characteristics of the absorption spectra of POM and DOM; (3) and the alteration of DOM molecular components. This project focusing on the optical-chemical characteristics of marine photosynthetic organic matter, will provide new thought and sight to better understand the potential effect of ocean acidification coupled with light intensity to the organic carbon and nitrogen cycling in the coastal seas in China.