Exploring the Impact of Paleowater Salinity on the Development of Ediacaran-Cambrian Ecosystems

The Ediacaran–Cambrian transition marks the most dramatic evolutionary turnover in Earth history: the rise of diverse Ediacaran fossil assemblages, followed by rapid metazoan diversification and the assembly of the first metazoan-dominated marine ecosystems. While extensive paleoenvironmental studies have emphasized redox fluctuations and nutrient loading as potential key drivers of this this landmark evolutionary event, the role of paleowater salinity, an environmental factor critical to the ecological development of diverse aquatic ecosystems, remains poorly constrained. Recent advances in boron-based salinity proxies, particularly the B/Ga ratio, have enabled robust, high-resolution reconstruction of paleosalinity across this critical interval. Here, we present new B/Ga ratio data from the late Ediacaran Dongpo Biota, multiple Shaanxilithes-bearing fossil sites, and the early Cambrian Qingjiang and Chengjiang biotas, to explore the potential link between paleowater salinity and ecosystem development across the Ediacaran–Cambrian transition. Integrated with global published paleosalinity records, our results demonstrate that Ediacaran ecosystems persisted across a broad salinity gradient from hyposaline to hypersaline waters, while the iconic Cambrian Chengjiang and Qingjiang biotas formed exclusively under stable, normal marine salinity conditions. These findings highlight the fundamental influence of paleowater salinity on the ecological development of Ediacaran–Cambrian ecosystems, and provide new insights into the co-evolution of life and environment during this critical geological interval.