Environmental changes in Saginaw Bay,Lake Huron recorded by geolipid contents of sediments deposited since 1800 |
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Authors: | Philip A Meyers Norishige Takeuchi |
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Institution: | (1) Oceanography Program Department of Atmospheric and Oceanic Science, The University of Michigan, Ann Arbor, Michigan |
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Abstract: | Changes in organic materials preserved within sediments of Saginaw Bay deposited over the past two centuries record corresponding
periods in the environmental history of this part of Lake Huron and its watershed. Sediments deposited since 1940 show an
increasingly greater input of aquatic organic matter in response to accelerating cultural eutrophication of Saginaw Bay. Concentrations
of fatty acids, sterols, fatty alcohols, and aliphatic hydrocarbons are higher in these modern sediments than in deeper ones.
Molecular distributions of these geolipids reflect less aquatic material deeper in the sediments. Prior to 1875, sediment
organic matter appears to be diluted by mineral matter from enhanced erosion caused by clearing of the watershed for farming
and settlement. During this period there is better preservation of carbonate minerals due to quicker burial. Since 1875, petroleum
components comprise over 90% of the total aliphatic hydrocarbon content of these sediments, reflecting the advent and continued
existence of chronic, low-level petroleum contamination of this part of the Great Lakes. |
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