• United States Department of Agriculture, Forest Service, Cooperative State Research Service
  

Aquatic sampling has evolved at an exceptional pace in recent years. While the varieties of sampling hardware have increased manyfold, perhaps more important have been advances in the sophistication and sensitivity of the hypotheses being tested. Previously, impacts on aquatic ecosystems were measured solely as changes in number of individuals or taxa; however, researchers now are focusing attention on the subtler impacts on community level processes, such as recolonization and decomposition of Ìeaf litter, and on experimental designs highly sensitive to subtle shifts in community structure (Rabeni and others 1980). The burgeoning literature on freshwater community dynamics and sampling hardware and the great significance to society of aquatic communities suggested a need for this manual.