Terrestrial soils in forested landscapes represent some of the largest mercury (Hg) reserves globally. Wildfire can alter the storage and distribution of terrestrial-bound Hg via reemission to the atmosphere or mobilization in watersheds where it may become available for methylation and uptake into food webs. Using data associated with the 2007 Moonlight and Antelope Fires in California, we examined the long-term direct effects of wildfire burn severity on the distribution and magnitude of Hg concentrations in riparian food webs. Additionally, we quantified the cross-ecosystem transfer of Hg from aquatic invertebrate to riparian bird communities; and assessed the influence of biogeochemical, landscape variables, and ecological factors on Hg concentrations in aquatic and terrestrial food webs. Benthic macroinvertebrate methylmercury (MeHg) and riparian bird blood total mercury (THg) concentrations varied by 710- and 760-fold, respectively, and Hg concentrations were highest in predators. We found inconsistent relationships between Hg concentrations across and within taxa and guilds in response to stream chemical parameters and burn severity. Macroinvertebrate scraper MeHg concentrations were influenced by dissolved organic carbon (DOC); however, that relationship was moderated by burn severity (as burn severity increased the effect of DOC declined). Omnivorous bird Hg concentrations declined with increasing burn severity. Overall, taxa more linked to in situ energetic pathways may be more responsive to the biogeochemical processes that influence MeHg cycling. Remarkably, 8 years post-fire, we still observed evidence of burn severity influencing Hg concentrations within riparian food webs, illustrating its overarching role in altering the storage and redistribution of Hg and influencing biogeochemical processes.

森林景观中的陆地土壤是全球最大的汞 (Hg) 储量之一。野火可以通过重新排放到大气中或在流域中流动来改变陆地汞的储存和分布，在流域中汞可能会甲基化并被食物网吸收。利用 2007 年加利福尼亚州月光和羚羊火灾的相关数据，我们研究了野火烧伤严重程度对河岸食物网中汞浓度的分布和程度的长期直接影响。此外，我们还量化了汞从水生无脊椎动物到河岸鸟类群落的跨生态系统转移；并评估了生物地球化学、景观变量和生态因素对水生和陆地食物网中汞浓度的影响。底栖大型无脊椎动物甲基汞 (MeHg) 和河岸鸟类血液总汞 (THg) 浓度分别相差 710 倍和 760 倍，其中捕食者体内的汞浓度最高。我们发现不同类群和行会之间以及内部的汞浓度与水流化学参数和烧伤严重程度之间的关系不一致。大型无脊椎动物刮刀的甲基汞浓度受到溶解有机碳 (DOC) 的影响；然而，这种关系受到烧伤严重程度的调节（随着烧伤严重程度的增加，DOC 的效果下降）。杂食性鸟类的汞浓度随着烧伤严重程度的增加而下降。总体而言，与原位能量途径联系更紧密的类群可能对影响甲基汞循环的生物地球化学过程更敏感。值得注意的是，火灾发生 8 年后，我们仍然观察到烧伤严重程度影响河岸食物网内汞浓度的证据，说明其在改变汞的储存和重新分配以及影响生物地球化学过程方面的首要作用。