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<p>Carbon (C) and silicon (Si) are vital elements in aquatic biogeochemical cycling, closely linked to climate change. However, mechanisms governing their coupled burial in estuaries, especially regarding eutrophication, are not well understood. To address this knowledge gap, a synthesis of C and Si (C-Si) burial was conducted using a comprehensive dataset to investigate the primary drivers in a river-dominated estuary. Core samples collected from the Changjiang River Estuary indicate significant alterations in C-Si burial over several decades. A direct temporal correlation was observed between the declines in mass accumulation rates in the Changjiang estuary and the suspended sediments of the Changjiang River. Additionally, C-Si burial was directly associated with river inputs and shifts in the composition of estuarine algae. Anthropogenic influences increased phytolith diversity while concurrently decreasing diatom diversity from 1964 to 2017. The variations in C-Si burial, attributed to changes in the composition of organic C (OC) resulting from shifts between marine and terrestrial sources, as well as contributions from diatom and non-diatom sources, represent the primary processes driving fluctuations in C burial within this riverdominated estuary, exhibiting a cyclical pattern in estuarine sedimentation approximately every 60 years. Measurements of δ<sup>13</sup>C associated with biogenic silica (δ<sup>13</sup>C<sub>BSi</sub>) and OC (δ<sup>13</sup>C<sub>Org</sub>) from sediment samples reveal that δ<sup>13</sup>C<sub>BSi</sub> is more depleted in carbon- 13 than δ<sup>13</sup>C<sub>Org</sub>, suggesting a higher degradation of the sedimentary OC. By utilizing the carbon-to-nitrogen ratio in OC alongside OC associated with biogenic silica particles, we developed a methodology to quantify the carbon contribution derived from nondiatom sources. Our calculation indicates an increase in the burial of C from non-diatom sources, with an average enhancement of 9%. This approach provides a robust method for examining changes in C preservation associated with Si under the increasing anthropogenic nutrient inputs in coastal waters.</p>

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Changes in carbon and silica burial in a river-dominated estuary

  • 期刊论文

  • 发表日期：

    2025年5月30日

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  • Xiangbin Ran,
  • Hao Wang

摘要

Carbon (C) and silicon (Si) are vital elements in aquatic biogeochemical cycling, closely linked to climate change. However, mechanisms governing their coupled burial in estuaries, especially regarding eutrophication, are not well understood. To address this knowledge gap, a synthesis of C and Si (C-Si) burial was conducted using a comprehensive dataset to investigate the primary drivers in a river-dominated estuary. Core samples collected from the Changjiang River Estuary indicate significant alterations in C-Si burial over several decades. A direct temporal correlation was observed between the declines in mass accumulation rates in the Changjiang estuary and the suspended sediments of the Changjiang River. Additionally, C-Si burial was directly associated with river inputs and shifts in the composition of estuarine algae. Anthropogenic influences increased phytolith diversity while concurrently decreasing diatom diversity from 1964 to 2017. The variations in C-Si burial, attributed to changes in the composition of organic C (OC) resulting from shifts between marine and terrestrial sources, as well as contributions from diatom and non-diatom sources, represent the primary processes driving fluctuations in C burial within this riverdominated estuary, exhibiting a cyclical pattern in estuarine sedimentation approximately every 60 years. Measurements of δ13C associated with biogenic silica (δ13CBSi) and OC (δ13COrg) from sediment samples reveal that δ13CBSi is more depleted in carbon- 13 than δ13COrg, suggesting a higher degradation of the sedimentary OC. By utilizing the carbon-to-nitrogen ratio in OC alongside OC associated with biogenic silica particles, we developed a methodology to quantify the carbon contribution derived from nondiatom sources. Our calculation indicates an increase in the burial of C from non-diatom sources, with an average enhancement of 9%. This approach provides a robust method for examining changes in C preservation associated with Si under the increasing anthropogenic nutrient inputs in coastal waters.