Gottgens, J. F. University of Toledo, jgottge@uoft02.utoledo.edu
Kaplan, S. F. Lake Michigan Ecological Research Station, USGS, Stephanie_Kaplan@nps.org
Simmers, B. S. University of Toledo, bsimmer@uoft02.utoledo.edu

 
TESTING THE USEFULNESS OF SEDIMENTARY INDICATORS TO REFLECT PAST ENVIRONMENTAL CONDITIONS
 
We tested the ability of five indicators to reflect past environmental conditions by comparing core records from the western basin of Lake Erie with the lake's documented pollution history. Two cores, taken by divers from 9.5 m deep and isotopically-dated, showed an increase in the Centrales/Pennales (C/P) diatom ratio from 0.54 in early-settlement deposits (>100 years BP) to 1.40 during the 1960s. C/P values in recent deposits returned to early-settlement levels and matched ratios documented in field studies. Similarity indices were highest for recent vs. early-settlement and for eutrophic (1950s) vs. hyper-eutrophic (1960s) deposits. Fluctuations in phosphorus accumulation corresponded to known changes in trophic state. Large-bodied cladocerans, thought to correlate with lower trophic states, comprised 24% of total cladocerans in the 1960s deposits. This increased to 53% with the recent recovery of the lake matching the ratio reported in field studies. Hexagenia limbata tusk accumulation decreased to zero in sediments deposited during hyper-eutrophy and increased again in more recent layers confirming the documented history of the basin. Mercury stratigraphy in the cores paralleled known environmental input and peak levels, reported in a 1970 core, were recovered in deposits of similar age in 1995 cores. Comparing stratigraphic data with historical information tested the usefulness of these data for paleolimnological reconstructions in lakes where baseline conditions and historical variability are unknown.
 
Day: Friday, Feb. 5
Time: 04:15 - 04:30pm
Location: Sweeney Center
 
Code: CS63FR0415S