Electron microscopic study of succession in the periphyton community of lake Washington.

Microbial succession has been observed on electron microscope grids immersed in lake water for 1, 3, 6, and 10 days. As predicted by ecological theory, the biomass, numbers, and diversity of attached microorganisms increased as succession proceeded. The diversity index of Shannon showed a marked increase from 3.1 at day 1 to 4.2 at day 3. It continued to rise at day 6 and attained the maximum value calculated on day 10 of 4.8. Bacteria were the major pioneer colonizers in this mesotrophic community. Based on these results and the results of other microbiologists who have found bacteria to be the dominant component during the pioneer stage of succession in periphyton communities of varying trophic status, we suggest that microbial heterotrophs may commonly, and perhaps always, be the major component of the early pioneer community of autogenic successions.