Division of Coastal Sciences, School of Ocean Science and Engineering, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, USA.
Division of Coastal Sciences, School of Ocean Science and Engineering, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, USA.
Sci Total Environ. 2020 May 20;718:137181. doi: 10.1016/j.scitotenv.2020.137181. Epub 2020 Feb 25.
We studied the ecological resilience of salt marshes by deriving sea level rise (SLR) thresholds in two estuaries with contrasting upland hydrological inputs in the north-central Gulf of Mexico: Grand Bay National Estuarine Research Reserve (NERR) with limited upland input, and the Pascagoula River delta drained by the Pascagoula River, the largest undammed river in the continental United States. We applied a mechanistic model to account for vegetation responses and hydrodynamics to predict salt marsh distributions under future SLR scenarios. We further investigated the potential mechanisms that contribute to salt marsh resilience to SLR. The modeling results show that salt marshes in the riverine dominated estuary are more resilient to SLR than in the marine dominated estuary with SLR thresholds of 10.3 mm/yr and 7.2 mm/yr respectively. This difference of >3 mm/yr is mainly contributed by larger quantities of riverine-borne mineral sediments in the Pascagoula River. In both systems, sediment trapping by the above-ground vegetation appears to contribute more to marsh platform accretion than organic matter from below-ground biomass based on the medians of the accretion rates. However, below-ground biomass could contribute up to 90% of accretion in the marine dominated estuary compared to only 60% of accretion in the riverine dominated estuary. SLR thresholds of salt marshes are more sensitive to vegetation biomass in the marine dominated estuary while biomass and sediment similarly affect SLR thresholds of salt marshes in the riverine dominated estuary. This research will likely help facilitate more informed decisions on conservation/restoration policies for these two types of systems in the near-term needed to minimize future catastrophic loss of these coastal marsh habitats once SLR thresholds are exceeded.
我们通过在墨西哥湾中北部两个具有不同高地水文输入的河口研究盐沼的生态弹性，得出海平面上升（SLR）阈值：格兰德湾国家河口研究保护区（NERR），其高地输入有限，以及由美国大陆最大的无坝河流帕斯卡古拉河排水的帕斯卡古拉河三角洲。我们应用一种机械模型来解释植被响应和水动力，以预测在未来海平面上升情景下盐沼的分布。我们进一步研究了有助于盐沼对海平面上升弹性的潜在机制。建模结果表明，与以海洋为主的河口相比，以河流为主的河口的盐沼对海平面上升的弹性更强，海平面上升阈值分别为 10.3 毫米/年和 7.2 毫米/年。这种 3 毫米/年以上的差异主要是由于帕斯卡古拉河携带的大量河流矿物质沉积物。在这两个系统中，地上植被的沉积物捕获似乎比地下生物量的有机物质更有助于沼泽平台的堆积，这基于堆积率的中位数。然而，在以海洋为主的河口，地下生物量可能贡献高达 90%的堆积，而在以河流为主的河口，只有 60%的堆积。在以海洋为主的河口，盐沼的海平面上升阈值对植被生物量更为敏感，而在以河流为主的河口，生物量和沉积物同样影响盐沼的海平面上升阈值。这项研究可能有助于为这两种类型的系统在短期内做出更明智的保护/恢复决策，以尽量减少一旦海平面上升阈值被超过，这些沿海沼泽栖息地未来灾难性损失。
