Primary Productivity in Permafrost-Influenced Aquatic Ecosystems of the Arctic (PROPERAQUA)

本项目旨在调查科雷马河（俄罗斯西伯利亚冻土带）受永久冻土融化（永久冻土）有机物质影响的初级生产力。由于气候变化，北极的永久冻土正在融化，使大量含有高度不稳定碳的有机物质暴露在环境中。科雷马河地区是研究陆地-河流-海洋界面气候变化驱动过程的理想地点。每年在融雪期间，降解的永久冻土中的有机物质被冲入科雷玛河，成为细菌消耗和光降解的额外碳来源，反过来又会增加这个水生生态系统中二氧化碳的产量。光自养生物生产生物质（生物初级生产）的CO2利用率（CO2汇）仍然是北极碳循环知识中的一个空白。在这个项目中，将测量生物碳循环的两个关键指标：(i)总产氧量（GOP）和（ii）净群落生产量（NCP）。GOP是由光合作用产生的氧的速率，并被用作生物量（总初级生产量）的总碳固定和储存速率的代表。NCP是指因GOP减少的碳吸收量和通过群落呼吸损失的有机碳。从春季到秋季将测量GOP和NCP的季节变化及其空间分布。为了实现这一目标，为海洋系统建立的最先进的方法将首次应用于北极内陆水域。该方法依靠测量氧氩比（O2/Ar）以及溶解氧同位素比（17O/16O和18O/16O）来解剖氧气的物理和生物来源以及科雷马河水体中大气和光合氧气的独特同位素特征。最后，初级生产力的新数据以及p（CO2）、溶解有机碳和营养物质含量的测量将被整合到一个水文-生物地球化学数值模型中，以一维碳预算将科雷马河碳循环的主要成分和相关的水文过程联系起来。PROPERAQUA将揭示北极水生生态系统中融化的永久冻土中有机物质和营养物质的周转和命运，并将协调水生初级生产对北极碳预算的贡献。这些结果为更大规模的研究提供了基础，旨在更好地确定气候变化对北极水生碳循环的当前和未来环境影响。

This project aims to investigate the primary productivity in the Kolyma River (Siberian tundra, Russia) influenced by organic material from thawing permafrost (perennially frozen soil). Permafrost in the Arctic is thawing due to climate change, exposing to the environment large amounts of organic material that contain highly labile carbon. The Kolyma River region is an ideal location to study climate change-driven processes at the land-river-sea interfaces. Each year during the snow melt period, organic material from degrading permafrost is washed out into the Kolyma River, becoming an additional source of carbon for bacterial consumption and photodegradation that in turn will increase the production of CO2 in this aquatic ecosystem. The rates of CO2 utilization (CO2-sink) by photoautotrophic organisms for the production of biomass (biological primary production) are still a gap in the knowledge of the Arctic carbon cycle. In this project, two key metrics of the biological carbon cycle will be measured: (i) gross oxygen production (GOP) and (ii) net community production (NCP). GOP is the rate of oxygen that has been produced by photosynthesis and is used as a proxy of the total rate of carbon fixation and storage as biomass (Gross Primary Production). NCP is the net amount of carbon uptake reduced by GOP and the loss of organic carbon through community respiration. Seasonal changes of GOP and NCP along with their spatial distribution will be measured from spring to autumn. To accomplish this goal, a state-of-the-art method established for marine systems will be applied to Arctic inland waters for the first time. This method relies on measurements of Oxygen-to-Argon ratios (O2/Ar) as well as the isotope ratios of dissolved oxygen (17O/16O and 18O/16O) to dissect the physical and biological sources of oxygen and the distinct isotopic signatures of atmospheric and photosynthetic oxygen in the waters of the Kolyma River. Finally, the novel data of primary productivity along with measurements of p(CO2), dissolved organic carbon and the content of nutrients will be integrated into a hydrology-biogeochemistry numerical model to link in a one-dimensional carbon budget the major constituents of the carbon cycle and associated hydrological processes of the Kolyma River. PROPERAQUA will unravel the turnover and fate of organic matter and nutrients from thawing permafrost in Arctic aquatic ecosystems and will reconcile the contribution of aquatic primary production to the Arctic carbon budget. These results serve as a baseline for larger-scale studies aiming to better identify the current and future environmental impact of climate change in the Arctic aquatic carbon cycle.