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Delving deeper: metabolic processes in the metalimnion of stratified lakes

Giling, D. P., Staehr, P. A., Grossart, H. P., Andersen, M. R., Boehrer, B., Escot, C., Evrendilek, F., Gómez-Gener, L., Honti, M., Jones, I. D., Karakaya, N., Laas, A., Moreno-Ostos, E., Rinke, K., Scharfenberger, U., Schmidt, S. R., Weber, M., Woolway, R. I., Zwart, J. A. and Obrador, B. (2017) Delving deeper: metabolic processes in the metalimnion of stratified lakes. Limnology and Oceanography, 62 (3). pp. 1288-1306. ISSN 0024-3590

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To link to this item DOI: 10.1002/lno.10504

Abstract/Summary

Many lakes exhibit seasonal stratification, during which they develop strong thermal and chemical gradients. An expansion of depth-integrated monitoring programs has provided insight into the importance of organic carbon processing that occurs below the upper mixed layer. However, the chemical and physical drivers of metabolism and metabolic coupling remain unresolved, especially in the metalimnion. In this depth zone, sharp gradients in key resources such as light and temperature co-occur with dynamic physical conditions that influence metabolic processes directly and simultaneously hamper the accurate tracing of biological activity. We evaluated the drivers of metalimnetic metabolism and its associated uncertainty across 10 stratified lakes in Europe and North America. We hypothesized that the metalimnion would contribute highly to whole-lake functioning in clear oligotrophic lakes, and that metabolic rates would be highly variable in unstable polymictic lakes. Depth-integrated rates of gross primary production (GPP) and ecosystem respiration (ER) were modelled from diel dissolved oxygen curves using a Bayesian approach. Metabolic estimates were more uncertain below the epilimnion, but uncertainty was not consistently related to lake morphology or mixing regime. Metalimnetic rates exhibited high day-to-day variability in all trophic states, with the metalimnetic contribution to daily whole-lake GPP and ER ranging from 0% to 87% and<1% to 92%, respectively. Nonetheless, the metalimnion of low-nutrient lakes contributed strongly to whole-lake metabolism on average, driven by a col- linear combination of highlight, low surface-water phosphorous concentration and high metalimnetic volume. Consequently, a single-sensor approach does not necessarily reflect whole-ecosystem carbon dynamics in stratified lakes.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:70399
Publisher:Wiley

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