Understanding the threat to ecosystems from excess nitrogen in coastal waters is a priority issue in scientific research and natural resource management. Previous field studies have demonstrated that high nitrogen loading can decrease the health and resiliency of salt marshes through shifting biomass allocation, increasing decomposition, and causing creek bank instability, all of which can lead to increased marsh loss with sea-level rise. However, other studies have shown relatively little impact of increasing nitrogen on the structure and function of these systems. Due to the long history of eutrophication in Long Island Sound, aggressive nitrogen reduction strategies have been enacted in this region, but detrimental nutrient inputs persist at variable levels throughout the watershed. Here, the extent of nitrogen-linked salt marsh change under varying levels of nutrient stress was measured, testing the hypothesis that salt marsh resilience (as measured by Spartina alterniflora belowground biomass and marsh edge stability) decreases with increasing nitrogen loading. S. alterniflora growth (stem height, stem density, and biomass) and within-marsh creek area were quantified in 10 salt marshes along a nitrogen-loading gradient. Increasing nitrogen loading showed a significant negative relationship with dead belowground biomass in S. alterniflora; the loss of this belowground biomass in higher nitrogen systems may decrease salt marshes’ ability to keep pace with sea-level rise. Neither shifts in live biomass allocation nor a positive relationship between aboveground biomass or stem height and increasing nitrogen was observed that might promote additional sediment capture, but higher stem density could play a role in promoting sedimentation on the marsh surface in more sediment-rich systems. Aerial photography analysis revealed marsh creek expansion since 1934 at 90% of the marshes studied, but unlike findings from prior experimental enrichment studies, the rate of marsh loss did not increase with increasing nitrogen loading. Given the importance of these ecosystems and the potential of nitrogen to decrease their resiliency, understanding the impacts of eutrophication on salt marshes is critical. However, these results show that the relative importance of nitrogen in driving salt marsh loss in Long Island Sound may be less than studies from other regions have suggested.

了解沿海水域过量氮对生态系统的威胁是科学研究和自然资源管理的优先问题。先前的实地研究表明，高氮负荷会通过改变生物量分配、增加分解和导致河岸不稳定来降低盐沼的健康和恢复力，所有这些都会导致随着海平面上升沼泽损失增加。然而，其他研究表明增加氮对这些系统的结构和功能的影响相对较小。由于长岛海峡富营养化的悠久历史，该地区已经制定了积极的氮减少策略，但在整个流域中，有害的养分输入仍以不同的水平持续存在。这里，互花米草地下生物量和沼泽边缘稳定性）随着氮负荷的增加而降低。互花米草的生长（茎高、茎密度和生物量）和沼泽小溪内面积在 10 个盐沼中沿氮负荷梯度量化。增加氮负荷与互花米草的地下死生物量呈显着负相关；高氮系统中这种地下生物量的损失可能会降低盐沼跟上海平面上升的能力。没有观察到活生物量分配的变化，也没有观察到地上生物量或茎高与增加氮之间的正相关可能会促进额外的沉积物捕获，但较高的茎密度可能会在更富含沉积物的系统中促进沼泽表面的沉积作用。航空摄影分析显示，自 1934 年以来，90% 的研究沼泽都出现了沼泽小溪扩张，但与之前实验富集研究的结果不同，沼泽流失率并未随着氮负荷的增加而增加。鉴于这些生态系统的重要性以及氮降低其恢复力的潜力，了解富营养化对盐沼的影响至关重要。然而，