Abstract
We present and evaluate an update to the process-based lake model MyLake that includes a time-varying linkage between light attenuation of both photosynthetically active radiation (PAR) and ultraviolet (UV) radiation wavelengths to changes in dissolved organic carbon (DOC). In many parts of northeastern North America and Europe, DOC in lakes has rapidly increased, leading to reduced water transparency and increases in light attenuation. These changes alter the vertical light and heat distribution that affect vertical structuring of temperature and dissolved oxygen. We use this model update to test the responsiveness of PAR and UV attenuation to short-term fluctuations in DOC and with a test case of long-term browning at Lake Giles (Pennsylvania). Lake Giles has browned significantly since the late 1980s, and three decades of detailed empirical data have indicated more than a doubling of DOC concentrations, and consequent increases in PAR and UV attenuation, warming surface waters, cooling deep waters, and increasing deepwater oxygen depletion. We found that the model performance improved by 16% and 52% for long-term trends in PAR and UV attenuation, respectively, when these coefficients respond directly to in-lake DOC concentrations. Further, long-term trends in surface water warming, deepwater cooling, and deepwater oxygen depletion in Lake Giles were better captured by the model following this update, and were very rapid due to its high water transparency and low DOC. Hence, incorporating a responsive link between DOC and light attenuation in lake models is key to understanding long-term lake browning patterns, mechanisms, and ecological consequences.
| Original language | English |
|---|---|
| Pages (from-to) | 2278-2289 |
| Number of pages | 12 |
| Journal | Limnology and Oceanography |
| Volume | 66 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 2021 |
| Externally published | Yes |
Funding
R. M. Pilla was supported by the Sentinel North Research Internship Scholarship program for foreign students at Université Laval, and by NSF DEB 1950170, 1754276, and 1754265 grants. This research was also supported the Sentinel North program of Université Laval, and made possible, in part, thanks to funding from the Canada First Research Excellence Fund. R. M. Couture acknowledges funding from the NSERC Discovery grant program. Data collection at Lake Giles was supported by Craig Williamson's Global Change Limnology Laboratory at Miami University and especially E. P. Overholt, and Kevin Rose's Global Water Laboratory at Rensselaer Polytechnic Institute. We thank Lacawac Sanctuary and Biological Field Station and B. R. Hargreaves for collection of and access to meteorological data. Model code and data from this application are available at https://github.com/biogeochemistry. R. M. Pilla was supported by the Sentinel North Research Internship Scholarship program for foreign students at Université Laval, and by NSF DEB 1950170, 1754276, and 1754265 grants. This research was also supported the Sentinel North program of Université Laval, and made possible, in part, thanks to funding from the Canada First Research Excellence Fund. R. M. Couture acknowledges funding from the NSERC Discovery grant program. Data collection at Lake Giles was supported by Craig Williamson's Global Change Limnology Laboratory at Miami University and especially E. P. Overholt, and Kevin Rose's Global Water Laboratory at Rensselaer Polytechnic Institute. We thank Lacawac Sanctuary and Biological Field Station and B. R. Hargreaves for collection of and access to meteorological data. Model code and data from this application are available at https://github.com/biogeochemistry .