Response of the Deep Chlorophyll Maximum in Lake Superior to Changing Temperatures

Session: 48. - Physical Ecology in Large Lakes and their Watersheds

Kaitlin Reinl, Large Lakes Observatory, University of Minnesota Duluth, [email protected]
Robert Sterner, University of Minnesota Duluth, [email protected]
Jay Austin, Large Lakes Observatory, UMD, [email protected]

Abstract

Using data from three sources (autonomous gliders, CTD casts, and laboratory analyses) we were able to explore drivers of Deep Chlorophyll Maximum (DCM) structure in Lake Superior including width, depth, and maximum concentration, and test for signals of climate change using surface water temperature as a proxy. No differences in nutrient concentrations were observed, indicating that DCM structure is not driven by a nutricline. Thermocline depth and euphotic depth were also tested and thermocline depth was not found to be a significant predictor of DCM characteristics, indicating that sinking phytoplankton may not be responsible for DCM formation. Euphotic depth was a significant predictor of all DCM characteristics, which may indicate that the DCM is driven by photoadaptation of the phytoplankton community. Signals of climate change in the DCM were evaluated using surface water temperature. A strong negative relationship was found between surface temperature and DCM width (R2 = 0.62), while surface temperature and DCM maximum chlorophyll concentration were positively related (R2 = 0.41). It remains unclear what the primary drivers of DCM formation in Lake Superior are; however, it is clear that the DCM is changing as temperature continues to warm, which may have important implications for whole lake productivity.

1. Keyword
climate change

2. Keyword
Lake Superior

3. Keyword
phytoplankton

4. Additional Keyword
deep chlorophyll maximum