Trends and controls on lake color in the high elevation western United States
Date
2021
Authors
Austin, Miles T., author
Ross, Matthew R. V., advisor
Hall, Ed, committee member
Bailey, Ryan, committee member
Journal Title
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Volume Title
Abstract
Lakes are perceived to be having an increase in algal blooms across the Western United States due to climate change driven and other anthropogenic drivers. Despite this perception, long-term records do not exist for many lakes, so looking at macroscale patterns is challenging. We present and discuss here our results from using a remote sensing dataset, LimnoSat-US. LimnoSat-US contains Landsat imagery from 1984 to 2020. In the intermountain west, our focus study region of Colorado, Wyoming, Idaho, Montana, New Mexico, and Utah, LimnoSat includes 1,200 lakes and over 150,000 summer observations of water color and reflectance. We used LimnoSat-US to examine what controls lake color and what, if any, changes are occurring lake color, which is a strong indicator of whether a lake is prone to algae blooms. A lake's mean depth and annual temperature were the strongest predictors of whether a lake was, on average, blue and clear or green and murky. Despite the perception of increased algae blooms, we found no consistent evidence of lakes 'greening' or shifting from mostly oligotrophic, blue, and clear to eutrophic, green, and murky. Instead, the vast majority of our lakes (> 80%) had no trend in lake color. Further, we found that our approach did not capture the dominant controls on whether not a lake was shifting from blue to green or green to blue, highlighting the need for additional work.