ELF ECOLOGICAL MONITORING IN MICHIGAN .4. CHANGES IN EARTHWORM COMMUNITIES OF TEST AND CONTROL SITES FROM 1984 TO 1993

Results of a 10-year study of lumbricid communities in Michigan's Uppe r Peninsula are reported. The objective of the investigation was to as sess potential effects of Extremely Low Frequency (ELF) electromagneti c (EM) fields on lumbricid populations. The first 5 years (1984-88) we re pre-operational, i.e., the ELF antenna which generated these EM fie lds had not yet been activated. During the last 5 years (1989-93), the antenna was operational at 76 Hz and 150 Amps. Lumbricid community da ta from the pre-operational period have been reported previously. Here , community and selected population parameters from the operational pe riod are given in detail, together with summaries for the entire study period. In the Test site (adjacent to the ELF antenna), fluctuations in community diversity were relatively small; in the Control site (not subject to ELF influence), diversity increased steadily and significa ntly over the last 6 years of the study. Specific population responses to climatic patterns as well as long-term dynamics of non-dominant sp ecies were shown to underlie appreciable changes in community structur e. Between-site comparisons in terms of potential EM field effects wer e suggested to be inappropriate, since community-level data (unlike sp ecies-specific data) lack the power to predict what the magnitude and nature of community composition and structure would have been in the a bsence of ELF EM field influence.