Di-nitrogen (N₂) fixation rates, and the diversity of the organisms that fix N₂, remain largely unconstrained in the aquatic landscapes or aquascapes (e.g., lakes, wetlands, streams, rivers, estuaries) between land and sea. As a result, we lack a mechanistic understanding of the controls and contributions of N₂ fixation across disparate aquatic environments, and cannot accurately incorporate this process into local and global nitrogen (N) budgets. This special issue brings together papers highlighting current advances in understanding of N₂ fixation within and across all aquatic habitats, integrating novel methodology for studying N₂ fixation, quantification of N₂ fixation fluxes in understudied habitats, the role of N₂ fixation in biotic assemblages, and the rate and fate of fixed N in heterogeneous landscapes. Together, these papers address important gaps in understanding and highlight the frontiers of research on N₂ fixation in aquatic habitats.

双氮 (N ₂ ) 固定率以及固定 N ₂ 的生物多样性在水生景观或水族造景（例如湖泊、湿地、溪流）中基本上不受限制、河流、河口）陆地和海洋之间。因此，我们对不同水生环境中固氮 ₂ 的控制和贡献缺乏机械理解，并且无法准确地将这一过程纳入当地和全球氮（N）预算。本期特刊汇集了一些论文，重点介绍了当前对所有水生生境内部和跨水生生境的 N ₂ 固定的理解进展，整合了研究 N ₂ 固定的新方法、N ₂ 固定的作用，以及异质景观中固定氮的速率和命运。这些论文共同解决了理解方面的重要差距，并强调了水生生境中固氮 ₂ 研究的前沿。