250 years of climate-mediated ecological change in Santa Fe Lake, NM
Date
2022
Authors
Shampain, Anna, author
Baron, Jill, advisor
Leavitt, Peter, committee member
von Fischer, Joe, committee member
Sibold, Jason, committee member
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Abstract
Mountain lakes are sensitive indicators of anthropogenically driven global change. Lake sediment records in the western United States have documented increased percent carbon and nitrogen and heightened primary productivity indicative of eutrophication in mountain lakes. Recent paleolimnological studies suggest atmospheric nutrient deposition and warming underlie these changes. We analyzed a short sediment core from Santa Fe Lake, NM, the southernmost subalpine lake in the Rocky Mountain Range to investigate patterns in lake biogeochemical and algal biomarkers since 1747. Lake sediments were dated using 210Pb activities and analyzed for percent C and N, δ13C, δ15N, and algal pigments representative of total biomass, chlorophytes, cryptophytes, diatoms, and other primary producers from Santa Fe Lake. Throughout the 250-year sediment record from Santa Fe Lake, we observed changes in algal community composition alongside biogeochemical alterations. During the cold dry conditions of the Little Ice Age, there were greater proportions of cyanobacteria, diatoms, and sulfur bacteria. Total algal biomass increased under increased warming and climate variability with significant increases in chlorophytes and cryptophytes. Significant rates of change occurred concurrently with increases in regional N deposition in the mid-20th century. C, N, δ13C, δ15N remained relatively stable throughout the record, until the mid-20th century when C and N increased exponentially alongside depletions in δ13C, δ15N. Our results suggest climate-driven algal assemblage changes throughout the record with regional N deposition contributing to contemporary productivity increases. The timing and magnitude of these changes differ from other studied lakes. Our findings highlight the heterogeneity of lakes' responses to changing environmental conditions in the Anthropocene and call attention to the role of climate-induced ecological change in the absence of critical N deposition.
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Subject
Anthropocene
climate
paleolimnology
biogeochemistry
alpine
lakes