Happi Johann Ludovic Martial, Nzigou Aimé Roger, Schaal Gauthier, Rouget Marie-Laure, Mabicka Obame Rolf Gael, Le Loc'h François, Mbega Jean-Daniel, Leboulanger Christophe, Mickala Patrick
Université des Sciences et Techniques de Masuku, Franceville, Gabon.
MARBEC, Université de Montpellier, CNRS, Ifremer, IRD, Sète, France.
PLoS One. 2025 Jun 17;20(6):e0326172. doi: 10.1371/journal.pone.0326172. eCollection 2025.
Among the most productive ecosystems worldwide, mangroves contribute to global carbon sequestration and play a pivotal role for many species, including supporting the sustainable provision of intertropical fisheries resources. Despite the many essential ecosystem services they provide, mangrove ecosystems are facing increasing anthropogenic pressure, primarily because they develop in littoral areas where human activities are rapidly expanding, causing deforestation, urban extension and pollution. Mangroves cover over 1,700 km² of Gabon's coastline, stretching within protected zones or located alongside populated areas, raising concerns about the potential impact of pollution. This study assessed pollution levels in mangrove surface sediments from 24 stations in the capital city of Libreville and the two adjacent Marine Protected Areas (MPAs), Akanda and Pongara, where human impact has not been fully characterized. From 2021 to 2023, we measured chlorophyll a, fecal indicator bacteria (FIB: Escherichia coli and fecal streptococci) and six trace metals (As, Cd, Cr, Cu, Pb and Zn). Our results show that while Pongara National Park remains relatively pristine, human influence has resulted in significant contamination of sediments by FIB and trace metals, with Cu, Pb and Zn being associated with boat traffic and fuel spills. Chlorophyll a at the surface of sediments, indicative of microphytobenthic biomass, reflect the eutrophication from urban discharge. Spatial differences in contamination patterns are significant between Libreville and Akanda, and between Akanda and Pongara parks (p < 0.05), but not significant between Libreville and Pongara National Park (p > 0.05), suggesting a possible rapid dispersion of urban pollution. Despite localized pollution, contamination levels remained generally low, suggesting that patterns are influenced more by the specific characteristics of each area than by MPA status. This study provides a first assessment of pollution pressure on mangrove tidal flats within protected areas in Gabon, emphasizing that the success of MPAs could be enhanced through contamination monitoring to achieve long-term conservation goals.
作为全球生产力最高的生态系统之一，红树林有助于全球碳固存，对许多物种起着关键作用，包括支持热带渔业资源的可持续供应。尽管红树林生态系统提供了许多重要的生态系统服务，但它们正面临着越来越大的人为压力，主要是因为它们生长在人类活动迅速扩张的沿海地区，导致森林砍伐、城市扩张和污染。红树林覆盖了加蓬1700多平方公里的海岸线，分布在保护区内或人口密集地区附近，这引发了人们对污染潜在影响的担忧。本研究评估了首都利伯维尔以及两个相邻的海洋保护区（阿坎达和庞加拉）中24个站点的红树林表层沉积物的污染水平，在这些地方人类影响尚未得到充分描述。在2021年至2023年期间，我们测量了叶绿素a、粪便指示菌（FIB：大肠杆菌和粪链球菌）以及六种痕量金属（砷、镉、铬、铜、铅和锌）。我们的结果表明，虽然庞加拉国家公园相对原始，但人类影响已导致沉积物受到FIB和痕量金属的严重污染，铜、铅和锌与船只交通和燃油泄漏有关。沉积物表面的叶绿素a是微型底栖植物生物量的指标，反映了城市排放造成的富营养化。利伯维尔和阿坎达之间以及阿坎达和庞加拉公园之间的污染模式空间差异显著（p < 0.05），但利伯维尔和庞加拉国家公园之间差异不显著（p > 0.05），这表明城市污染可能迅速扩散。尽管存在局部污染，但污染水平总体上仍然较低，这表明污染模式更多地受每个区域的特定特征影响，而非海洋保护区的状态。本研究首次评估了加蓬保护区内红树林潮滩的污染压力，强调通过污染监测可以提高海洋保护区的成效，以实现长期保护目标。
