If the little buggers spring or jump like a flea when disturbed it's most likely a springtail. These little bugs live in the top layers of soil especially high quality soils that have a lot of life in it and come out and on top of the soil when it rains or snow falls and begins to melt into the ground. Most of them are dead probably because they are drowning but it's ok they won't harm your garden if it is a springtail.