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Article

Nutrient Loading, Temperature and Heat Wave Effects on Nutrients, Oxygen and Metabolism in Shallow Lake Mesocosms Pre-Adapted for 11 Years

1
Department of Bioscience, Aarhus University and Aarhus University Centre for Water Technology (WATEC), 8600 Silkeborg, Denmark
2
Sino-Danish Centre for Education and Research, University of Chinese Academy of Sciences, Beijing 100190, China
3
Limnology Laboratory, Department of Biology, Middle East Technical University, 06800 Ankara, Turkey
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Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Turkey
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Ecosystem Research and Implementation Center, Middle East Technical University, 06800 Ankara, Turkey
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Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
7
Nuclear Research Center, National University of Mongolia, 14201 Ulaanbaatar, Mongolia
*
Author to whom correspondence should be addressed.
Water 2021, 13(2), 127; https://doi.org/10.3390/w13020127
Received: 30 October 2020 / Revised: 29 December 2020 / Accepted: 31 December 2020 / Published: 7 January 2021
(This article belongs to the Special Issue Effect of Extreme Climate Events on Lake Ecosystems)
Global changes (e.g., warming and population growth) affect nutrient loadings and temperatures, but global warming also results in more frequent extreme events, such as heat waves. Using data from the world’s longest-running shallow lake experimental mesocosm facility, we studied the effects of different levels of nutrient loadings combined with varying temperatures, which also included a simulated 1-month summer heat wave (HW), on nutrient and oxygen concentrations, gross ecosystem primary production (GPP), ecosystem respiration (ER), net ecosystem production (NEP) and bacterioplankton production (BACPR). The mesocosms had two nutrient levels (high (HN) and low (LN)) combined with three different temperatures according to the IPCC 2007 warming scenarios (unheated, A2 and A2 + 50%) that were applied for 11 years prior to the present experiment. The simulated HW consisted of 5 °C extra temperature increases only in the A2 and A2 + 50% treatments applied from 1 July to 1 August 2014. Linear mixed effect modeling revealed a strong effect of nutrient treatment on the concentration of chlorophyll a (Chl-a), on various forms of phosphorus and nitrogen as well as on oxygen concentration and oxygen percentage (24 h means). Applying the full dataset, we also found a significant positive effect of nutrient loading on GPP, ER, NEP and BACPR, and of temperature on ER and BACPR. The HW had a significant positive effect on GPP and ER. When dividing the data into LN and HN, temperature also had a significant positive effect on Chl-a in LN and on orthophosphate in HN. Linear mixed models revealed differential effects of nutrients, Chl-a and macrophyte abundance (PVI) on the metabolism variables, with PVI being particularly important in the LN mesocosms. All metabolism variables also responded strongly to a cooling-low irradiance event in the middle of the HW, resulting in a severe drop in oxygen concentrations, not least in the HN heated mesocosms. Our results demonstrate strong effects of nutrients as well as an overall rapid response in oxygen metabolism and BACPR to changes in temperature, including HWs, making them sensitive ecosystem indicators of climate warming. View Full-Text
Keywords: climate change; extreme events; ecosystem processes; lake restoration climate change; extreme events; ecosystem processes; lake restoration
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MDPI and ACS Style

Jeppesen, E.; Audet, J.; Davidson, T.A.; Neif, É.M.; Cao, Y.; Filiz, N.; Lauridsen, T.L.; Larsen, S.E.; Beklioğlu, M.; Sh, T.; Søndergaard, M. Nutrient Loading, Temperature and Heat Wave Effects on Nutrients, Oxygen and Metabolism in Shallow Lake Mesocosms Pre-Adapted for 11 Years. Water 2021, 13, 127. https://doi.org/10.3390/w13020127

AMA Style

Jeppesen E, Audet J, Davidson TA, Neif ÉM, Cao Y, Filiz N, Lauridsen TL, Larsen SE, Beklioğlu M, Sh T, Søndergaard M. Nutrient Loading, Temperature and Heat Wave Effects on Nutrients, Oxygen and Metabolism in Shallow Lake Mesocosms Pre-Adapted for 11 Years. Water. 2021; 13(2):127. https://doi.org/10.3390/w13020127

Chicago/Turabian Style

Jeppesen, Erik, Joachim Audet, Thomas A. Davidson, Érika M. Neif, Yu Cao, Nur Filiz, Torben L. Lauridsen, Søren E. Larsen, Meryem Beklioğlu, Tserenpil Sh, and Martin Søndergaard. 2021. "Nutrient Loading, Temperature and Heat Wave Effects on Nutrients, Oxygen and Metabolism in Shallow Lake Mesocosms Pre-Adapted for 11 Years" Water 13, no. 2: 127. https://doi.org/10.3390/w13020127

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