Data from: Road salt and organic additives affect mosquito growth and survival: an emerging problem in wetlands

The global increase in the application rate of road salts such as sodium chloride (NaCl) has led to concern about their negative effects on roadside habitats and freshwater ecosystems. To reduce the application rate of NaCl and minimize the ecological effects of road salts, transportation agencies are continuously seeking alternative salts such as magnesium chloride (MgCl 2) and organic additives such as beet juice and distillation byproducts. Yet, there is remarkably little information about how these road salt alternatives and additives affect aquatic communities, including their effects on mosquito populations. Nonetheless, understanding how anthropogenic factors such as road salts and salt additives affect mosquito populations could help minimize threats to human health, especially in urban environments. We used outdoor, freshwater mesocosms to experimentally investigate how the road salt MgCl 2 and two organic additives affect mosquito (Culex restuans) survival and emergence. Additionally, we measured changes to abiotic aspects of the environment that could affect mosquito larvae during development. We found that increased concentrations of MgCl 2 reduced mosquito survival while organic additives increased food resources that, in turn, reduced the average time to emergence for mosquitoes. Additionally, the organic additives reduced dissolved oxygen (DO) to hypoxic levels, which might negatively affect mosquito predators such as fish. In the absence of toxic concentrations of MgCl 2 or other salts, reduced predation coupled with the faster emergence times, means that organic additives, might increase mosquito population size. More comprehensive studies of multi-trophic interactions in freshwater ecosystems should be conducted before agencies promote the application of alternative road salts and road salt additives.

全球道路用盐（如氯化钠（NaCl））的施用量持续攀升，引发学界对其损害路边生境与淡水生态系统的广泛担忧。为降低氯化钠（NaCl）的施用量并减轻道路用盐的生态负面影响，交通管理部门正持续探索替代盐类（如氯化镁（MgCl₂））及有机添加剂（如甜菜汁与蒸馏副产物）。然而，目前关于此类道路用盐替代品与添加剂如何影响水生群落（包括蚊虫种群）的研究信息极为匮乏。尽管如此，厘清道路用盐及盐类添加剂等人为因素对蚊虫种群的影响，有助于降低其对人类健康的威胁，在城市环境中这一点尤为关键。本研究采用室外淡水中型实验生态系统开展实验，探究道路用盐氯化镁（MgCl₂）与两种有机添加剂对雷氏库蚊（Culex restuans）的存活率及羽化成功率的影响。此外，我们还测定了可能影响蚊虫幼虫发育阶段的环境非生物因子变化。实验结果显示，氯化镁（MgCl₂）浓度升高会降低蚊虫存活率；而有机添加剂可提升食物资源量，进而缩短蚊虫的平均羽化时长。同时，有机添加剂会将溶解氧（DO）降至缺氧水平，这可能对鱼类等蚊虫天敌产生不利影响。在氯化镁（MgCl₂）或其他盐类未达到毒性浓度的前提下，天敌捕食压力降低叠加羽化时长缩短，意味着有机添加剂或可扩大蚊虫种群规模。在交通管理部门推广使用替代道路用盐及盐类添加剂之前，应针对淡水生态系统中的多营养级相互作用开展更为全面的研究。