Moriarty Julia M, Friedrichs Marjorie A M, Harris Courtney K
Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA 23062 USA.
Institute of Arctic and Alpine Research and Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO 80303 USA.
Estuaries Coast. 2021;44(1):103-122. doi: 10.1007/s12237-020-00763-8. Epub 2020 Jun 9.
Sediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic-sediment transport-biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.
沉积物过程，包括再悬浮和输运，通过改变光衰减、初级生产力和有机物质再矿化来影响河口水质，进而影响氧和氮的动态变化。由于多种因素，这些过程对氧和氮动态变化的相对重要性在空间和时间上有所不同，而且难以测量，因此需要采用建模方法来量化沉积物再悬浮和输运如何影响河口生物地球化学。对切萨皮克湾2002年和2003年夏季的水动力 - 沉积物输运 - 生物地球化学耦合模型结果表明，再悬浮增加了光衰减，特别是在海湾最北部地区，使初级生产向下游转移。再悬浮还增加了海湾中部的再矿化，由于初级生产力和河口环流的下游转移，该区域的有机物质浓度更高。结果，由于海湾最北部地区光合作用减少以及海湾中部再矿化增加，整个海湾水柱底部的氧含量下降，铵含量增加。在整个航道上平均而言，再悬浮使水柱底部的氧含量降低了约25%，铵含量增加了约50%。再悬浮引起的变化与单个夏季的短期变化以及2002年和2003年（分别为湿润年和干旱年）之间的年际变化具有相同的量级，并且通常超过这些变化。我们的结果量化了沉积物再悬浮和输运对生物地球化学的影响程度，并深入了解了沿海系统可能如何应对管理措施和环境变化。
