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<p>Large benthic rays are increasingly recognized as important bioturbators in estuarine systems, yet their influence on nutrient cycling, particularly nitrogen dynamics, remains underexplored. In this study, eagle ray (<i>Myliobatis tenuicaudatus</i>) foraging pits were simulated in the Whangateau Harbour, New Zealand, to investigate short-term effects on sediment solute fluxes across a gradient of mud content (1.3–9.9%). Using in-situ chambers, net oxygen (O<sub>2</sub>), ammonium (NH<sub>4</sub><sup>+</sup>), and dinitrogen (N<sub>2</sub>) fluxes were measured alongside sediment organic matter content and chlorophyll-<i>a</i> concentration. Multivariate analysis revealed that experimental pits altered sediment ecosystem processes, with mud content modulating the effect. Strongest pit effects were observed in net fluxes of N₂, NH₄⁺ and concentrations of chlorophyll-<i>a</i>. Net N<sub>2</sub> fluxes increased by up to 138% in the experimental pits compared to controls in sands with higher mud content but were lower than the controls in low-mud sands. Net NH₄⁺ fluxes also rose in pits, with increases of 96% in intermediate mud content and 50% in the highest mud group. These findings demonstrate that sediment characteristics like mud content establish the geochemical context in which ray bioturbation acts as a dynamic modifier of net nitrogen fluxes. </p>

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Simulated Ray Bioturbation Reveals Effects on Nitrogen Dynamics Across a Sediment Mud Gradient

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月2日

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  • Alessandra L. Vallim,
  • Stefano Schenone,
  • Ines Bartl,
  • Simon Thrush

摘要

Large benthic rays are increasingly recognized as important bioturbators in estuarine systems, yet their influence on nutrient cycling, particularly nitrogen dynamics, remains underexplored. In this study, eagle ray (Myliobatis tenuicaudatus) foraging pits were simulated in the Whangateau Harbour, New Zealand, to investigate short-term effects on sediment solute fluxes across a gradient of mud content (1.3–9.9%). Using in-situ chambers, net oxygen (O2), ammonium (NH4+), and dinitrogen (N2) fluxes were measured alongside sediment organic matter content and chlorophyll-a concentration. Multivariate analysis revealed that experimental pits altered sediment ecosystem processes, with mud content modulating the effect. Strongest pit effects were observed in net fluxes of N₂, NH₄⁺ and concentrations of chlorophyll-a. Net N2 fluxes increased by up to 138% in the experimental pits compared to controls in sands with higher mud content but were lower than the controls in low-mud sands. Net NH₄⁺ fluxes also rose in pits, with increases of 96% in intermediate mud content and 50% in the highest mud group. These findings demonstrate that sediment characteristics like mud content establish the geochemical context in which ray bioturbation acts as a dynamic modifier of net nitrogen fluxes.