Seasonality of pCO₂ in a hard-water lake of the northern Great Plains The legacy effects of climate and limnological conditions over 36 years

• Published in: Limnology and oceanography Vol. 64; no. S1; pp. S118 - S129
• Main Authors: Finlay, Kerri, Vogt, Richard J., Simpson, Gavin L., Leavitt, Peter R.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley and Sons, Inc 01.01.2019; John Wiley & Sons, Inc
• ISSN: 0024-3590; 1939-5590
• DOI: 10.1002/lno.11113

Biogeochemical processes are active year-round in ice-covered lakes, such that processes in one season can affect limnological conditions in subsequent seasons. However, the extent and nature of these legacy effects are poorly understood, particularly for the CO₂ content of lakes and when considering gas exchange with the atmosphere. Here, we used a unique 36-yr dataset of weekly limnological measurements of Buffalo Pound Lake in the northern Great Plains to assess seasonal changes in CO₂ concentration and flux and determine how dependent lake pCO₂ is on limnological conditions of previous seasons. We found that the lake was a net source of CO₂ to the atmosphere (mean 18.5 ± 7.4 mol CO₂ m−2 yr−1), with spring potentially accounting for the majority (∼ 64% ± 20%) of CO₂ efflux, assuming ice in spring was permeable to gas exchange (32.9% ± 19.8% if not). Analysis with generalized additive models (GAMs) demonstrated that current and antecedent seasonal conditions combined to explain 72.6% of deviance in spring pCO₂, but that the strength of model predictions and the importance of antecedent conditions diminished in GAMs of summer (43.6%) and fall (23.3%) CO₂ levels. This research suggests that pCO₂ is regulated by a combination of coeval and historical environmental conditions and shows that quantification of seasonal and annual fluxes requires a mechanistic understanding of the legacy effects of preceding time intervals.