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Abstract Ice‐off dates on lakes are some of the longest phenological records in the field of ecology, and some of the best evidence of long‐term climatic change. However, there has been little investigation as to whether the date of ice‐off on a lake impacts spring and summer ecosystem dynamics. Here, I analyzed 274 years of long‐term data from eight north temperate lakes in two climate zones to address whether lakes have ecological memory of ice‐off in the subsequent summer. Five metrics were investigated: epilimnion temperatures, hypolimnion temperatures, hypolimnetic oxygen drawdown, water clarity, and spring primary productivity. The response of the metrics to ice‐off date were variable across latitude and lake type. The northern set of lakes stratified quickly following ice‐off, and early ice‐off years resulted in significantly warmer hypolimnetic temperatures. Oxygen depletion in the hypolimnion was not impacted by ice‐off date, likely because in late ice‐off years the lakes did not fully mix. In the southern lakes, ice‐off date was not correlated to the onset of stratification, with the latter being a more dominant control on hypolimnetic temperature and oxygen. The implications of these findings is that as ice‐off date trends earlier in many parts of the world, the lakes that will likely experience the largest changes in spring and summer ecosystem properties are the lakes that currently have the longest duration of lake ice. In considering a future with warmer winters, these results provide a starting point for predicting how lake ecosystem properties will change with earlier ice‐off.
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Methane and Primary Productivity in Lakes: Divergence of Temporal and Spatial Relationships
Abstract In lakes, the production and emission of methane (CH4) have been linked to lake trophic status. However, few studies have quantified the temporal response of lake CH4dynamics to primary productivity at the ecosystem scale or considered how the response may vary across lakes. Here, we investigate relationships between lake CH4dynamics and ecosystem primary productivity across both space and time using data from five lakes in northern Wisconsin, USA. From 2014 to 2019, we estimated hypolimnetic CH4storage rates for each lake using timeseries of hypolimnetic CH4concentration through the summer season. Across all lakes and years, hypolimnetic CH4storage ranged from <0.001 to 7.6 mmol CH4 m−2 d−1and was positively related to the mean summer rate of gross primary productivity (GPP). However, within‐lake temporal responses to GPP diverged from the spatial relationship, and GPP was not a significant predictor of interannual variability in CH4storage at the lake scale. Using these data, we consider how and why temporal responses may differ from spatial patterns and demonstrate how extrapolating cross‐lake relationships for prediction at the lake scale may substantially overestimate the rate of change of CH4dynamics in response to lake primary productivity. We conclude that future predictions of lake‐mediated climate feedbacks in response to a shifting distribution of trophic status should incorporate both varying lake responses and the temporal scale of change.
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- PAR ID:
- 10455534
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 125
- Issue:
- 9
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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