Urbanization drives multiple environmental changes that influence critical ecosystem processes. Factors such as salinization by deicing road salts, reduced water clarity (and greater light attenuation) from eutrophication and sediment loading, and warming constrain not only the biodiversity of ponds, but also their physical mixing (with consequences for oxygen availability and the provision of ecosystem services). Leveraging an extensive urban gradient in the Greater Toronto Area, we collected summertime depth profiles from 50 stormwater retention ponds to investigate their vertical stratification. We found that water columns were generally stratified but contrary to expectations, we found relatively minor roles of basin area and depth. Instead, we discovered an overwhelming effect of salinity along with significant impacts of temperature and water clarity on water density gradients. Findings extend our fundamental understanding of mixing regimes in small, shallow waterbodies and indicate increasing risks to pond functioning in a warmer and saltier future.

中文翻译：

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盐化、变暖和水体透明度降低抑制了小型城市池塘的垂直混合

城市化推动了影响关键生态系统过程的多种环境变化。除冰盐造成的盐化、富营养化和沉积物负荷造成的水体透明度降低（以及更大的光衰减）以及变暖等因素不仅限制了池塘的生物多样性，而且限制了它们的物理混合（对氧气的可用性和生态系统的提供产生影响）服务）。利用大多伦多地区广泛的城市梯度，我们收集了 50 个雨水滞留池的夏季深度剖面，以调查其垂直分层。我们发现水柱通常是分层的，但与预期相反，我们发现盆地面积和深度的作用相对较小。相反，我们发现盐度的压倒性影响以及温度和水透明度对水密度梯度的显着影响。研究结果扩展了我们对小型浅水体混合机制的基本理解，并表明在温暖和含盐量更高的未来，池塘功能的风险不断增加。