Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake
Algal blooms have increased in frequency, intensity, and duration in response to nitrogen (N) cycling in freshwater ecosystems. We conducted a high-resolution sedimentary study of N transformation and its associated microbial activity in Lake Taihu to assess the accumulation rates of the different N...
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doaj-639b400117684d5f95e50fedf2176d672021-02-19T00:00:19ZengMDPI AGWater2073-44412021-02-011352452410.3390/w13040524Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic LakeYu Yao0Huaji Liu1Ruiming Han2Dujun Li3Limin Zhang4School of Environment, Nanjing Normal University, Nanjing 210023, ChinaSchool of Environment, Nanjing Normal University, Nanjing 210023, ChinaSchool of Environment, Nanjing Normal University, Nanjing 210023, ChinaSchool of Environment, Nanjing Normal University, Nanjing 210023, ChinaGreen Economy Development Institute, Nanjing University of Finance and Economics, Nanjing 210023, ChinaAlgal blooms have increased in frequency, intensity, and duration in response to nitrogen (N) cycling in freshwater ecosystems. We conducted a high-resolution sedimentary study of N transformation and its associated microbial activity in Lake Taihu to assess the accumulation rates of the different N fractions in response to algal blooms, aiming to understand the mechanisms of N cycling in lacustrine environments. Downcore nitrification and denitrification processes were measured simultaneously in situ via diffusive gradients in thin-films technique, peeper, and microelectrode devices in a region of intensified algal blooms of shallow lake. The decomposition of different biomasses of algal blooms did not change the main controlling factor on different N fractions in profundal sediment. However, the decomposition of different algal biomasses led to significant differences in the nitrification and denitrification processes at the sediment–water interface (SWI). Low algal biomasses facilitated the classic process of N cycling, with the balanced interaction between nitrification and denitrification. However, the extreme hypoxia under high algal biomasses significantly limited nitrification at the SWI, which in turn, restricted denitrification due to the lack of available substrates. Our high-resolution results combined with estimates of apparent diffusion fluxes of the different N fractions inferred that the lack of substrates for denitrification was the main factor influencing the positive feedback loop between N and eutrophication in freshwater ecosystems. Moreover, this positive feedback can become irreversible without technological intervention.https://www.mdpi.com/2073-4441/13/4/524algal bloomsnitrogen cycleLake Taihunitrificationdenitrificationeutrophication |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Yu Yao Huaji Liu Ruiming Han Dujun Li Limin Zhang |
spellingShingle |
Yu Yao Huaji Liu Ruiming Han Dujun Li Limin Zhang Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake Water algal blooms nitrogen cycle Lake Taihu nitrification denitrification eutrophication |
author_facet |
Yu Yao Huaji Liu Ruiming Han Dujun Li Limin Zhang |
author_sort |
Yu Yao |
title |
Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake |
title_short |
Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake |
title_full |
Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake |
title_fullStr |
Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake |
title_full_unstemmed |
Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake |
title_sort |
identifying the mechanisms behind the positive feedback loop between nitrogen cycling and algal blooms in a shallow eutrophic lake |
publisher |
MDPI AG |
series |
Water |
issn |
2073-4441 |
publishDate |
2021-02-01 |
description |
Algal blooms have increased in frequency, intensity, and duration in response to nitrogen (N) cycling in freshwater ecosystems. We conducted a high-resolution sedimentary study of N transformation and its associated microbial activity in Lake Taihu to assess the accumulation rates of the different N fractions in response to algal blooms, aiming to understand the mechanisms of N cycling in lacustrine environments. Downcore nitrification and denitrification processes were measured simultaneously in situ via diffusive gradients in thin-films technique, peeper, and microelectrode devices in a region of intensified algal blooms of shallow lake. The decomposition of different biomasses of algal blooms did not change the main controlling factor on different N fractions in profundal sediment. However, the decomposition of different algal biomasses led to significant differences in the nitrification and denitrification processes at the sediment–water interface (SWI). Low algal biomasses facilitated the classic process of N cycling, with the balanced interaction between nitrification and denitrification. However, the extreme hypoxia under high algal biomasses significantly limited nitrification at the SWI, which in turn, restricted denitrification due to the lack of available substrates. Our high-resolution results combined with estimates of apparent diffusion fluxes of the different N fractions inferred that the lack of substrates for denitrification was the main factor influencing the positive feedback loop between N and eutrophication in freshwater ecosystems. Moreover, this positive feedback can become irreversible without technological intervention. |
topic |
algal blooms nitrogen cycle Lake Taihu nitrification denitrification eutrophication |
url |
https://www.mdpi.com/2073-4441/13/4/524 |
work_keys_str_mv |
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