Tracing sewage water by ¹⁵N in a mangrove ecosystem to test its bioremediation ability

Abstract

Mangrove forests could be a simple and effective alternative to conventional sewage treatment, particularly for island communities given its low cost and low maintenance. Due to their high adaptation capacity, these plants are able to tolerate and bioremediate the high levels of nutrients and pollutants found in sewage water. This solution could be applied to small tropical islands with high population density such as Mayotte in the Indian Ocean. This paper reports on a trial by stable isotopic (15)N tracing of such a bioremediation process on pre-treated wastewater near the village of Malamani, in the middle of the large coastal mangrove in the bay near Chirongui. The first results show a boost in the mangrove growth, but a longer period of observation is needed to confirm the beneficial effects, and also to clarify the role of the local crab population, whose engineering activities play an important part in the ecosystem. The exact denitrification process is not yet understood, and the mass balance equation also reveals loss of nitrogen-containing compounds, which needs to be analyzed more closely.

Mangrove microbial diversity and the impact of trophic contamination

“…In the Chirongui bay mangrove, Lambs et al (2011) andHerteman et al (2011) first reported results at the vegetation and crab community scale, showing that their growth was boosted as a result of changes in the nutrient load in the mangrove sediments. However, analyses and observations of mangrove ecosystems as a whole are necessary to evaluate their bioremediation capacities as vegetative buffers against anthropogenic N-loading in coastal waters.…”

Mangrove Facies Drives Resistance and Resilience of Sediment Microbes Exposed to Anthropic Disturbance

“…These proportions remained stable in the impacted areas during the 12 months of the present study, indicating that sediment had reached an equilibrium state despite the continuous PW discharge (Figure 3). This suggests that additional C and N input in impacted areas were quickly removed from sediments either by microbial activities (Wu et al, 2008; Tam et al, 2009) and/or by vegetation assimilation (Ganguly et al, 2009; Lambs et al, 2011). This is confirmed by the absence of C:N ratio modification between T0 and T0 + 12 months in most areas except for the R-II and C-CC areas.…”