Tidal freshwater marshes (TFMs) are threatened by seawater intrusion, which can affect microbial communities and alter biogeochemical processes. Here, we report on a long-term, large-scale manipulative field experiment that investigated continuous (press) and episodic (pulse, 2 months/yr) inputs of brackish water on microbial communities in a TFM. After 2.5 yr, microbial diversity was lower in press treatments than in control (untreated) plots whereas diversity in pulse plots was unaffected by brackish water additions. Sulfate reducer abundance increased in response to both press and pulse treatments whereas methanogens did not differ among treatments. Our results, along with other lab and field measurements that show reduced soil respiration and extracellular enzyme activity suggest that continuous seawater intrusion will decrease macrophyte C inputs that reduce bacterial diversity in ways that also diminish ecosystem carbon cycling.

中文翻译：

---

压力与脉冲海水入侵对潮汐淡水沼泽微生物群落的不同影响

潮汐淡水沼泽 (TFM) 受到海水入侵的威胁，海水入侵会影响微生物群落并改变生物地球化学过程。在这里，我们报告了一项长期、大规模的操纵性野外实验，该实验研究了微咸水对 TFM 中微生物群落的连续（压力）和偶发（脉冲，2 个月/年）输入。2.5 年后，加压处理的微生物多样性低于对照（未处理）地块，而脉冲地块的多样性不受添加微咸水的影响。硫酸盐还原剂丰度随着压力和脉冲处理而增加，而产甲烷菌在处理之间没有差异。我们的结果，