Capdeville Cécile, Pommier Thomas, Gervaix Jonathan, Fromard François, Rols Jean-Luc, Leflaive Joséphine
EcoLab, CNRS, INPT, UPS, Université de Toulouse, Toulouse, France.
Ecologie Microbienne, INRA, UMR 1418, CNRS, UMR 5557, Université Lyon 1, Villeurbanne, France.
Front Microbiol. 2019 Jan 15;9:3337. doi: 10.3389/fmicb.2018.03337. eCollection 2018.
Mangrove forests are coastal ecosystems continuously affected by various environmental stresses and organized along constraint gradients perpendicular to the coastline. The aim of this study was to evaluate the resistance and resilience of sediment microbial communities in contrasted vegetation facies, during and after exposure to an anthropic disturbance. Our hypothesis was that microbial communities should be the most stable in the facies where the consequences of the anthropic disturbance are the most similar to those of natural disturbances. To test this, we focused on communities involved in N-cycle. We used an experimental system set up in Mayotte Island where 2 zones dominated by different mangrove trees are daily exposed since 2008 to pretreated domestic wastewater (PW) discharges. These freshwater and nutrients inputs should increase microbial activities and hence the anoxia of sediments. We monitored during 1 year the long-term impact of this disturbance, its short-term impact and the resilience of microbial communities on plots where PW discharges were interrupted. Microorganism densities were estimated by qPCR, the nitrification (NEA) and denitrification (DEA) enzyme activities were evaluated by potential activity measurements and pigment analyses were performed to assess the composition of microbial photosynthetic communities. At long-term PW discharges significantly modified the structure of phototrophic communities and increased the total density of bacteria, the density of denitrifying bacteria and DEA. Similar effects were observed at short-term, notably in the facies dominated by . The results showed a partial resilience of microbial communities. This resilience was faster in the facies dominated by , which is more subjected to tides and sediment anoxia. The higher stability of microbial communities in this facies confirms our hypothesis. Such information should be taken into account in mangrove utilization and conservation policies.
红树林是沿海生态系统，持续受到各种环境压力的影响，并沿着垂直于海岸线的约束梯度排列。本研究的目的是评估在受到人为干扰期间和之后，不同植被相沉积物微生物群落的抗性和恢复力。我们的假设是，在人为干扰后果与自然干扰后果最相似的相中，微生物群落应该是最稳定的。为了验证这一点，我们重点研究了参与氮循环的群落。我们使用了在马约特岛建立的一个实验系统，自2008年以来，两个由不同红树林主导的区域每天都受到预处理后的生活污水排放的影响。这些淡水和养分的输入应该会增加微生物活动，从而导致沉积物缺氧。我们监测了这种干扰的长期影响、短期影响以及在中断生活污水排放的地块上微生物群落的恢复力，为期一年。通过定量聚合酶链反应估计微生物密度，通过潜在活性测量评估硝化（NEA）和反硝化（DEA）酶活性，并进行色素分析以评估微生物光合群落的组成。长期来看，生活污水排放显著改变了光养群落的结构，增加了细菌的总密度、反硝化细菌的密度和DEA。短期也观察到了类似的影响，特别是在以……为主的相中。结果表明微生物群落具有部分恢复力。在受潮汐和沉积物缺氧影响更大的以……为主的相中，这种恢复力更快。该相中微生物群落的更高稳定性证实了我们的假设。在红树林利用和保护政策中应考虑此类信息。
