Environmental flow releases in lowland Australian rivers are currently timed to avoid high-carbon production on floodplains. Moreover, return flows (water draining from floodplains back into rivers) are avoided if there exists a risk of introducing deoxygenated “blackwater” into the main channel. This concern has restricted the range of possible watering scenarios being considered by environmental flow managers. We utilised a series of blackwater flows in the lower Murrumbidgee floodplain, Australia, in 2016 and 2017 to determine the origin and trophic contribution of blackwater dissolved organic carbon (DOC) in a floodplain wetland. We demonstrate a consistent difference in the isotope signature of blackwater DOC compared to both dissolved inorganic carbon (DIC) and river water DOC, explained by the greater contribution of floodplain vegetation (including the river red gum Eucalyptus camaldulensis) to blackwater DOC. Stable carbon isotope signatures suggest a contribution of blackwater to algal production, whereby microbial-mediated conversion of blackwater DOC into DIC may create opportunities for primary autotrophic productivity. This carbon signature was incorporated by the common yabby Cherax destructor. In the main river channel, C. destructor, the native gudgeon Hypseleotris spp. and the introduced European carp Cyprinus carpio may utilise the same basal carbon source. The use of small to moderate floodplain inundation with return flow to the river, properly monitored, would ameliorate the risk of hypoxia while providing the benefit of floodplain-derived DOC and associated increases to in-stream productivity.

目前已对澳大利亚低地河流的环境流量释放进行了定时，以避免洪泛区的高碳生产。此外，如果存在将脱氧的“黑水”引入主渠道的风险，则可以避免回流（从洪泛区流回河流）。这种担忧限制了环境流量管理者正在考虑的可能的浇水方案的范围。我们在2016年和2017年利用澳大利亚下穆伦比基（Murrumbidgee）洪泛区的一系列黑水流量，确定了洪泛区湿地中黑水溶解有机碳（DOC）的起源和营养贡献。我们证明了与溶解的无机碳（DIC）和河水DOC相比，黑水DOC的同位素特征具有一致的差异，桉树camaldulensis）到黑水DOC。稳定的碳同位素特征表明黑水对藻类生产的贡献，因此微生物介导的黑水DOC转化为DIC可能为初级自养生产力创造机会。这种碳素签名是由常见的yabby Cherax破坏者并入的。在主河道，C.析构函数，天然销子Hypseleotris属。和引进的欧洲鲤鱼Cyprinus carpio可能会利用相同的基础碳源。使用适当监测的中小型洪泛区淹没和回流河流，可以减轻缺氧风险，同时提供洪泛区DOC带来的好处，并提高溪流生产力。