Paleoproductivity of Late Holocene Lake Huron

Jamal Khaled Nigim, The University of Western Ontario

Abstract

The paleolimnology of North America’s Lake Huron is described using lead-210 dating, mineralogy, magnetic susceptibility, total organic carbon (TOC), total nitrogen (TN), carbon:nitrogen (C/N) ratio, grain size, and the δ¹³C_OM and δ¹⁵N_TN of organic matter. Sediment cores from Lake Huron’s 6 depositional basins and Georgian Bay span the Medieval Warm Period, Little Ice Age, and Canadian-European settlement. The main organic matter source is lacustrine algae, as indicated by δ¹³C_OM, δ¹⁵N_TN and C/N. Prior to the 19th century, primary production changes are reflected only by small variations in TOC and TN. A gradual increase in δ¹⁵N_TN (~1.1 ‰) suggests an increase in primary production since the start of the Industrial Revolution, likely due to warming and rising nutrient input. Deforestation, primarily during the 19^th century, contributed to a rise in TOC in the Huron basin. Further land clearance likely caused a prominent increase in magnetic susceptibility during the early- to mid-20^th century.