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.

全球范围内氯化钠（sodium chloride, NaCl）等道路用盐的施用量持续攀升，引发了学界对其给路边生境与淡水生态系统带来负面影响的担忧。为降低氯化钠的施用量并最大限度减轻道路用盐的生态影响，交通管理部门正持续探索替代用盐（如氯化镁（magnesium chloride, MgCl₂））与有机添加剂（如甜菜汁、蒸馏副产物）。然而，目前关于此类道路用盐替代品及添加剂如何影响水生群落（包括蚊类种群）的相关研究信息仍极为匮乏。尽管如此，明确道路用盐、盐类添加剂等人为因素对蚊类种群的影响机制，将有助于降低其对人类健康构成的威胁，在城市环境中尤为如此。本研究借助室外淡水中型实验生态系统（mesocosms），开展受控实验以探究道路用盐氯化镁（MgCl₂）与两种有机添加剂对骚扰库蚊（Culex restuans）的存活率及羽化情况的影响。此外，本研究还测定了发育过程中可能影响蚊幼虫的环境非生物因子变化。研究结果显示，氯化镁浓度升高会降低蚊类存活率，而有机添加剂则会提升食物资源丰度，进而缩短蚊类的平均羽化时长。此外，有机添加剂会将溶解氧（dissolved oxygen, DO）浓度降至低氧水平，这可能对鱼类等蚊类天敌产生负面影响。在氯化镁或其他盐类未达到毒性浓度的前提下，捕食压力降低加上羽化时长缩短，意味着有机添加剂可能会扩大蚊类种群规模。在交通管理部门推广使用道路用盐替代品及添加剂前，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。