For much of the twentieth century, marine microbial ecology was considered to be a minor and relatively unimportant aspect of oceanography. A lack of appropriate methodology led microbiologists to believe that bacteria were not abundant or particularly active. That view began to change with the development of an improved method for counting marine bacteria (Hobbie et al., 1977), which showed them to be much more abundant than conventional methods had suggested. Research accelerated after publication of a method for measuring bacterial secondary production (Fuhrman and Azam, 1982) and of a sensitive method for measuring microbial respiration in the ocean (Williams and Jenkinson, 1982). Data gathered with these improved methods left no doubt that bacterial growth and respiration constituted a major carbon flux in the ocean.