Response of Meiofauna to Mangrove Degradation in a Dry Semi-Desert Coastal Habitat of the Red Sea (Sudan)

摘要

The response of meiofauna to human-induced mangrove degradations in the Red Sea coast of the Sudan was investigated. Three sites were sampled. The mangroves have not been affected at one site, cleared partially from the second and completely from the third sites by human disturbance. At the two latter sites, sediment sorting declined and mean grain size decreased. In addition, spatial variations between shoreward and seaward stations of mud, organic and water contents were intensified. Although slight changes in total meiofauna density occurred among the three sites, the dominance structure differed significantly. Foraminifera and ostracods densities decreased significantly (P < 0.01) in the direction of the impact, as well as Acari (P < 0.05), while nematode density decreased significantly at the affected sites only in summer. In contrast, a sharp increase in copepods and nauplii densities (P < 0.01) occurred in the same direction. A natural gradient exists in the non-affected site, along which both sediment characteristics and meiofauna abundance slightly varied in seaward direction. At the affected sites, this gradient was disturbed by the intensified differences between shoreward and seaward stations, and by deviation from the general dominance structure in the meiofaunal communities. Seasonal variations were also exaggerated with increasing impact at the affected sites. Most of these modifications were significant as indicated by statistical analyses. The mangroves were shown to be important for improving sediment sorting and capacity to capture organic matter and water in such extreme muddy habitats. The overall feature of the change at the impacted sites was a gradual shifting from these characteristics, which was also indicated by changes in meiofauna assemblages. Consequently, the efficiency of the ecosystem as a nursery for marine organisms deteriorates. Conservation and local CZM plans should consider the importance and the ecological role of these mangroves in such extreme environments.