Deciphering the Ecology of Key Diatom Taxa to Understand Climate Induced Changes in West Greenland Lakes
Robert Northington, Ben Burpee, Rachel Dicker, Heera Malik, Joan McCue
Across the Arctic, paleolimnological records provide some of the few key archives documenting rates of ecological change in this region over the Holocene. In particular, striking changes in communities of diatoms have occurred over the last 150 years, with species generally associated with warmer conditions increasing at unprecedented rates in the sediment record. However, changes in diatom assemblages in lake sediments from west Greenland are different from those in the rest of the Arctic- they are rich in these “warmer” water diatoms throughout the Holocene. This difference has raised questions about what we can use diatoms to infer in the Arctic, and suggests the need to clarify the ecological traits of key diatom taxa in order to advance our understanding of drivers of change.
Recent research in alpine regions reveals that key diatom species that are used as indicators of 20th century warming in both arctic and alpine lakes respond specifically to both climate-induced changes in energy (i.e., mixing depths) and mass inputs (i.e., nutrients) to lake ecosystems. This suggests that spatially- and temporally-variable interactions between climate-induced changes in the physical and chemical structure of lakes may drive diatom community changes, but this is currently untested in arctic lakes.
We are coupling comparative lake sampling with both small- and large-scale experiments to provide key ecological information that will enable interpretation of climate-induced ecological changes from several existing diatom records from southwest Greenland. Specifically, the objective of this project is to determine the effects of climate-driven changes in nutrients and water column stability on the relative abundances of key diatom taxa, and to apply that information to existing diatom records to determine climate-induced changes in these lake ecosystems. A suite of lakes are being sampled to determine the factors controlling the distributions of key diatom species. Small-scale experiments are being conducted to assess the importance of nutrients and incubation depth on the abundances of these key diatom species. A large-scale experiment (i.e., whole lake manipulation) is being conducted to assess the importance of thermal stratification on these diatoms, which will be tested by deepening the mixed layer of a lake that typically thermally stratifies during the summer. This large-scale experiment will be the first whole-lake ecosystem test of the importance of changing energy influx on the community structure of these arctic lakes.
This research is being conducted in lakes near Kangerlussuaq, Greenland. It is funded by the NSF Arctic System Science Program (Grant #1203434).