Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China

Global fisheries’ production has intensified rapidly over recent decades, making significant contributions to food security and economic development. However, this growth has exerted pressure on marine ecosystems and altered coastal nitrogen cycling. This study focused on Sansha Bay, an important aq...

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Main Authors: Jianpeng Li, Xuan Lu, Qingmei Zhu, Yanpei Zhuang, Wei Yang, Di Qi
Format: Article
Language:English
Published: MDPI AG 2025-02-01
Series:Journal of Marine Science and Engineering
Subjects:
Online Access:https://www.mdpi.com/2077-1312/13/2/343
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author Jianpeng Li
Xuan Lu
Qingmei Zhu
Yanpei Zhuang
Wei Yang
Di Qi
author_facet Jianpeng Li
Xuan Lu
Qingmei Zhu
Yanpei Zhuang
Wei Yang
Di Qi
author_sort Jianpeng Li
collection DOAJ
description Global fisheries’ production has intensified rapidly over recent decades, making significant contributions to food security and economic development. However, this growth has exerted pressure on marine ecosystems and altered coastal nitrogen cycling. This study focused on Sansha Bay, an important aquaculture harbor in SE China, with measurements of environmental parameters and nitrate N–O isotopic compositions, to explore the impact of distinct mariculture types on nitrogen cycling in a coastal farming bay. The mean nitrate concentration was 120.7 ± 24.2 μmol dm<sup>−3</sup>, with a mean N/P ratio of 69.6 ± 19.6, indicating that the water column is in a state of eutrophication. Different aquaculture practices influence the nutrient status of water, with mixed farming (shellfish, seaweed, and fish) increasing nitrate concentrations and reducing N/P ratios, while seaweed farming reduces nitrate concentrations and increases N/P ratios. In spring, the average δ<sup>15</sup>N and δ<sup>18</sup>O values of nitrate in the water column were 8.4‰ and 8.7‰, respectively, compared with values of 9.8‰ and 4‰ recorded previously in winter. Such variation may be attributed to the greater influence of seaweed farming in spring when nitrate cycling is driven mainly by assimilation. In terms of aquaculture type, nitrate assimilation was stronger in seaweed farming zones, and nitrification was more pronounced in mixed farming zones. Overall, the results demonstrate that different mariculture types in Sansha Bay influence nitrogen cycling in the water body, with seaweed-based aquaculture systems contributing to the sustainable development of marine aquaculture by effectively mitigating eutrophication.
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spelling doaj-art-9e049b0c70ba413eb590e4cb6b1ff08f2025-08-20T02:04:06ZengMDPI AGJournal of Marine Science and Engineering2077-13122025-02-0113234310.3390/jmse13020343Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE ChinaJianpeng Li0Xuan Lu1Qingmei Zhu2Yanpei Zhuang3Wei Yang4Di Qi5Polar and Marine Research Institute, College of Harbor and Coastal Engineering, Jimei University, Xiamen 361021, ChinaPolar and Marine Research Institute, College of Harbor and Coastal Engineering, Jimei University, Xiamen 361021, ChinaCollege of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang 524088, ChinaPolar and Marine Research Institute, College of Harbor and Coastal Engineering, Jimei University, Xiamen 361021, ChinaPolar and Marine Research Institute, College of Harbor and Coastal Engineering, Jimei University, Xiamen 361021, ChinaPolar and Marine Research Institute, College of Harbor and Coastal Engineering, Jimei University, Xiamen 361021, ChinaGlobal fisheries’ production has intensified rapidly over recent decades, making significant contributions to food security and economic development. However, this growth has exerted pressure on marine ecosystems and altered coastal nitrogen cycling. This study focused on Sansha Bay, an important aquaculture harbor in SE China, with measurements of environmental parameters and nitrate N–O isotopic compositions, to explore the impact of distinct mariculture types on nitrogen cycling in a coastal farming bay. The mean nitrate concentration was 120.7 ± 24.2 μmol dm<sup>−3</sup>, with a mean N/P ratio of 69.6 ± 19.6, indicating that the water column is in a state of eutrophication. Different aquaculture practices influence the nutrient status of water, with mixed farming (shellfish, seaweed, and fish) increasing nitrate concentrations and reducing N/P ratios, while seaweed farming reduces nitrate concentrations and increases N/P ratios. In spring, the average δ<sup>15</sup>N and δ<sup>18</sup>O values of nitrate in the water column were 8.4‰ and 8.7‰, respectively, compared with values of 9.8‰ and 4‰ recorded previously in winter. Such variation may be attributed to the greater influence of seaweed farming in spring when nitrate cycling is driven mainly by assimilation. In terms of aquaculture type, nitrate assimilation was stronger in seaweed farming zones, and nitrification was more pronounced in mixed farming zones. Overall, the results demonstrate that different mariculture types in Sansha Bay influence nitrogen cycling in the water body, with seaweed-based aquaculture systems contributing to the sustainable development of marine aquaculture by effectively mitigating eutrophication.https://www.mdpi.com/2077-1312/13/2/343marine aquaculturestable nitrogen isotopesnitrate sourceeutrophicationSansha Bay
spellingShingle Jianpeng Li
Xuan Lu
Qingmei Zhu
Yanpei Zhuang
Wei Yang
Di Qi
Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China
Journal of Marine Science and Engineering
marine aquaculture
stable nitrogen isotopes
nitrate source
eutrophication
Sansha Bay
title Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China
title_full Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China
title_fullStr Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China
title_full_unstemmed Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China
title_short Nitrate δ<sup>15</sup>N and δ<sup>18</sup>O Values Reveal Mariculture Impacts on Nitrogen Cycling in Sansha Bay, SE China
title_sort nitrate δ sup 15 sup n and δ sup 18 sup o values reveal mariculture impacts on nitrogen cycling in sansha bay se china
topic marine aquaculture
stable nitrogen isotopes
nitrate source
eutrophication
Sansha Bay
url https://www.mdpi.com/2077-1312/13/2/343
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