Acosta Kailani G, Juhl Andrew R, Subramaniam Ajit, Duhamel Solange
Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, 10964, USA.
Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, 85721, USA.
Sci Rep. 2024 Mar 27;14(1):7305. doi: 10.1038/s41598-024-58044-4.
Dissolved inorganic nutrient concentrations in the surface waters (0 to 5 m) of the Northern Gulf of Mexico (NGoM) were analyzed from 1985 to 2019 (> 10,000 observations) to determine spatiotemporal trends and their connection to nutrients supplied from the Mississippi/Atchafalaya River (MAR). In the NGoM, annual mean dissolved inorganic P (DIP) concentrations increased significantly over time, while dissolved inorganic N (DIN) concentrations showed no temporal trend. With greater salinity, mean DIN:DIP decreased from above the Redfield ratio of 16 to below it, reflecting DIN losses and the more conservative behavior of DIP with salinity. Over the same time period, annual mean P (total dissolved P, DIP, dissolved organic P) loading from the MAR to the NGoM significantly increased, annual mean DIN and total dissolved N loading showed no temporal trend, and dissolved organic N loading significantly decreased. Though DIP increased in the MAR, MAR DIP alone was insufficient to explain the surface distribution of DIP with salinity. Therefore, increases in surface DIP in the NGoM are not simply a reflection of increasing MAR DIP, pointing to temporal changes in other DIP sources. The increase in NGoM DIP suggests greater N limitation for phytoplankton, with implications for N fixation and nutrient management.
对1985年至2019年期间（超过10000次观测）墨西哥湾北部（NGoM）表层水（0至5米）中溶解无机养分浓度进行了分析，以确定时空趋势及其与密西西比河/阿查法拉亚河（MAR）提供的养分之间的联系。在NGoM中，年平均溶解无机磷（DIP）浓度随时间显著增加，而溶解无机氮（DIN）浓度则没有时间趋势。随着盐度增加，平均DIN:DIP从高于16的雷德菲尔德比值降至低于该比值，反映出DIN的损失以及DIP随盐度变化更为保守的特性。在同一时期，MAR向NGoM输送的年平均磷（总溶解磷、DIP、溶解有机磷）负荷显著增加，年平均DIN和总溶解氮负荷没有时间趋势，而溶解有机氮负荷显著下降。尽管MAR中的DIP增加，但仅MAR的DIP不足以解释DIP随盐度的表层分布情况。因此，NGoM表层DIP的增加并非仅仅是MAR中DIP增加的反映，这表明其他DIP来源存在时间变化。NGoM中DIP的增加表明浮游植物对氮的限制更大，这对固氮作用和养分管理具有重要意义。
