Blue infrastructure is an important component of urban green infrastructure, due to its capacity for water cycle regulation and soil formation, as well as supporting unique biodiversity. Urban ponds, as part of urban blue, can harbour a diverse assemblage of aquatic macroinvertebrates. As yet, it is not clear how urbanisation affects macroinvertebrate diversity. In this study, we focus on diving beetles (Dytiscidae) in the Helsinki Metropolitan Area, Finland, to investigate how urbanisation affects their diversity, as well as the effects of margin steepness and the presence or absence of fish on urban dytiscids. We sampled dytiscids using 1-L activity traps in 14 fishless ponds and 11 ponds with fish, at ten sites. We applied generalised linear mixed models (GLMM) and non-metric multidimensional scaling (NMDS) to analyse the effects on dytiscid assemblages. We found that urbanisation had a negative effect on species richness but not on abundance. Steepness of pond margins and the presence or absence of predatory fish, affected both species richness and abundance: dytiscids prefer ponds with gently sloping margins; they have 80% higher species richness and are 79% more abundant in fishless ponds, and medium to large-sized dytiscid species are more capable of coexisting with fish. Urban wetlands can support a diversity of dytiscids at the regional level, and the presence of ponds without predatory fish is beneficial for maintaining dytiscid diversity. We recommend maintaining a diverse range of ponds and wetland habitats for the maintenance of aquatic biodiversity in urban regions.

蓝色基础设施是城市绿色基础设施的重要组成部分，因为它具有调节水循环和土壤形成的能力，并支持独特的生物多样性。作为城市蓝色的一部分，城市池塘可容纳各种各样的水生无脊椎动物。到目前为止，还不清楚城市化如何影响无脊椎动物的多样性。在这项研究中，我们重点研究芬兰赫尔辛基都会区的潜水甲虫（Dytiscidae），以研究城市化如何影响其多样性，以及边缘陡峭度和鱼类的存在与否对城市畸形的影响。我们在10个地点的14个无鱼塘和11个有鱼塘中使用1-L活性阱对dydycids进行了采样。我们应用广义线性混合模型（GLMM）和非度量多维标度（NMDS）来分析对dyscids组合的影响。我们发现，城市化对物种丰富度没有负面影响，但对物种丰富度没有负面影响。池塘边缘的陡峭性和掠食性鱼类的有无都影响物种的丰富性和丰度。它们的物种丰富度提高了80％，在无鱼池塘中的丰富度提高了79％，中型到大型的dydycid物种更容易与鱼类共存。城市湿地可以在区域一级支持多样性的生物多样性，而没有掠食性鱼类的池塘的存在有利于维持生物多样性。