Which method is used to enhance the effectiveness of larvicides in water bodies?

The use of surfactants to enhance the effectiveness of larvicides in water bodies is particularly effective because surfactants lower the surface tension of water. This allows the larvicides to spread more evenly across the water's surface, improving their overall distribution and effectiveness in targeting mosquito larvae. By coating the larvae and their habitats, surfactants can also improve the larvacide's ability to penetrate protective coatings that may surround the larvae, ensuring better uptake and effectiveness of the treatment.

In contrast, the other methods mentioned do not specifically enhance the action of larvicides. Reducing water flow might have some impact on the habitat but does not directly enhance the effectiveness of larvicides. Increasing salinity could adversely affect both the larvicides and the larvae, possibly making the control efforts less effective. Adding nutrients might promote the growth of algae and other organisms, which could further complicate mosquito control efforts rather than improving them. Therefore, the use of surfactants stands out as a direct and scientifically supported method to enhance larvicidal action in mosquito control practices.