39 Lakes as Sentinels of Environmental Change

Tuesday, 19 May 2020
1:30 PM - 5:30 PM
Lake Superior Ballroom MN

LINKING POST-GLACIAL (HYDRO)GEOLOGY TO REDOX GEOCHEMISTRY AND ECOLOGY OF MIDWESTERN LAKES

Paper number: 39-9
Program: Theme Sessions
Time: 3:50 PM – 4:10 PM

Authors

Abstract

The late Eville Gorham’s influential work looked holistically at the elemental inventory of lakes and wetlands, then by using mass-balance accounting and statistics to infer mechanisms, linked geochemical cycles to ecological processes. His words are a great reminder that hypothesis-driven research is rooted with observations: "My kind of science is based on chance and serendipity. Something will turn up.”[1] This shared scientific process unites limnologists from both the ecological and the geological sides of the spectrum.

As a geochemist interested in the pervasive redox-stratified oceans of Earth’s past, I have been drawn to study some seemingly quirky upper-Midwest lakes: those that are meromictic with > mM concentrations of dissolved iron in anoxic bottom waters (“ferruginous” conditions to geochemists). Such conditions arise from strong redox gradients within a lake, which in turn result from favorable morphometric parameters, an active carbon cycle, and a supply of solutes. After studying several of these lakes in the Midwest, accessing state-available data, and digging deep into the limnological literature, I have begun to wonder if some of these features are not quirky, but instead common among our lake-rich states. These observations have led me to hypothesize that ferruginous and/or meromictic systems may be an expected result of (hydro)geological features of post-glacial landscapes. I will discuss predictions and tests of this hypothesis, as well as whether data collected so far supports this hypothesis.

While ferruginous lakes are of interest to a geochemist, an ecologist might ask, does iron matter? If time permits, I will discuss a few examples of how this redox-active element and nutrient influences the ecology (encompassing phytoplankton and microbes) within ferruginous lakes, and therefore in-lake cycling of carbon. Hypotheses and data arising from these observations bring me back full circle, and enrich our understanding of how the marine carbon cycling might have operated in its redox-stratified past.

[1] Bright, E. (2020) “Prominent acid rain researcher Eville Gorham dies.” Minnesota Public Radio News, 15 January.

Geological Society of America Abstracts with Programs. Vol. 52, No. 5

doi: 10.1130/abs/2020NC-347828

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.