Dr. John Lichter, Bowdoin College

Seminar Abstract: European settlement of coastal Maine brought about a novel disturbance regime that impacted rivers and estuaries through overfishing, deforestation, dams, and water pollution. The negative consequences of these activities intensified with industrialization in the 19^th and 20^th centuries. To better understand the legacies of past human disturbance on coastal waterways in Maine, we reconstructed the history of Merrymeeting Bay and its two large tributaries, the Androscoggin and Kennebec Rivers, from documentary sources and the sedimentary record. Merrymeeting Bay is a large freshwater tidal ecosystem that played an important role in the Colonial and industrial history of the region. Reconstruction of diatom assemblages showed natural climate variability and human effects. By the early 18^th century, land clearance began an era of high sedimentation and eutrophication that strongly intensified in the 19^th and 20^th centuries. By the mid-20^th century, the ecosystem collapsed with seasonal anoxia and widespread fish kills. Implementation of Clean Water Act brought about rapid improvement in water quality related to oxygen depletion; however, little improvement in nutrient pollution was recorded by the diatom assemblages. Further recovery may require more stringent regulation of nutrient inputs from industrial and municipal point sources.

Research Interests: My research as an ecosystem ecologist began on coastal sand dunes bordering Lake Michigan where I studied the mechanisms of plant succession. Since then, I have contributed to research investigating the effects of rising atmospheric CO₂ on forest productivity and biogeochemical cycling with colleagues at Duke University. After coming to Bowdoin College in 2000, I began research on the ecology and environmental history of Merrymeeting Bay, which provide many engaging and important research topics for an ecologist. I am most interested in understanding the legacies of past human disturbance on the river-estuary complex and in providing information useful for the sound management and conservation of Maine's coastal ecosystems. To this end, I work with Bowdoin students to reconstruct the history of the ecosystem and to understand the consequences of past and present human activity on the ecosystem.

Host: Dr. William Schlesinger