The viscosity of water is the thickness of water (it might also be considered the stickiness when talking about other fluids). Water has many properties, and the viscosity of water influences in many of them. We can take the surface tension of a liquid as an example. The more viscous a substance is, higher will the surface tension be and vice versa since there will be a higher and lower attraction between molecules respectively.
→ The surface tension of water is something really important since it contributes in many ways to the environment and if you think about it, if the water was a little less viscous, there wouldn't be water since the viscosity of water makes it resistant to evaporation to a certain degree.
Increases because there's more food for the carnivores, as a result, the gradually the herbivores will decrease as the reach to a point they are no longer able to feed all the predators