Does the population size increase or decrease at higher trophic levels in the pyramid of numbers for all of your ecosystems?

The population size should decrease at higher trophic levels. The reason is there isn't enough prey to feed the predators as the trophic levels increase. For example, the biggest impact in the ocean would be if you lost all the small fish in an ocean because the predators would be left with less food. It's not exactly correlating, but if you think a little about the statistics it makes sense. 

hope this helps

Dthrough a slow process