Department of Botany, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Department of Geosciences, Federal University of São João del-Rei, São João del-Rei, Brazil.
Environ Microbiol. 2023 Dec;25(12):3592-3603. doi: 10.1111/1462-2920.16515. Epub 2023 Oct 10.
We show that epilithic biofilms are a relevant nitrogen (N) source in a rocky mountain range in Brazil. During different seasons, we quantified nitrate, ammonium, dissolved organic N (DON) and total dissolved N (TDN) leached by a simulated short rain event. We quantified the epilithic autotrophic biomass by taxonomic groups and its correlation with leached N. We hypothesized that leached N would be correlated to heterocystous cyanobacteria biomass since they are more efficient N fixers. We estimated a landscape N supply of 8.5 kg.ha .year considering the mean precipitation in the region. TDN in leachate was mainly composed of DON (83.8% ± 22%), followed by nitrate (12.1% ± 3%) and ammonium (5% ± 5%). The autotrophic epilithic community was mainly composed of non-heterocystous (Gloeocapsopsis) and heterocystous cyanobacteria (Scytonema and Stigonema), except for a site more commonly affected by fire events that showed a dominance of Chlorophyta. Biogeochemical upscaling was facilitated by the fact that N leaching was not different among sites or related to autotrophic epilithic biomass or assemblage composition. In conclusion, the capacity of epilithic biofilms to provide N to surrounding systems is an ecosystem service that underscores the necessity to conserve them and their habitats.
我们表明，巴西山区的附生生物膜是一个相关的氮（N）源。在不同的季节，我们量化了模拟短雨事件淋溶的硝酸盐、铵、溶解有机氮（DON）和总溶解氮（TDN）。我们通过分类群量化了附生自养生物量及其与淋溶 N 的相关性。我们假设淋溶 N 与异形胞蓝细菌生物量相关，因为它们是更有效的固氮生物。考虑到该地区的平均降水量，我们估计景观氮供应量为 8.5kg.ha.year。淋出液中的 TDN 主要由 DON（83.8%±22%）组成，其次是硝酸盐（12.1%±3%）和铵（5%±5%）。附生自养生物群落主要由非异形胞（Gloeocapsopsis）和异形胞蓝细菌（Scytonema 和 Stigonema）组成，除了一个受火灾事件影响更严重的地点，那里以绿藻为主导。生物地球化学放大是由以下事实促成的：淋溶 N 在不同地点之间没有差异，也与自养附生生物量或组合组成无关。总之，附生生物膜提供 N 给周围系统的能力是一种生态系统服务，强调了保护它们及其栖息地的必要性。
