Stuck in the mangrove mud: The risk of trace element exposure to shore crabs in restored urban mangroves

Impact of mangrove restoration on microplastic bioaccumulation in fiddler crabs across degraded, restored, and natural ecosystems

Understanding the role of mangroves in microplastic (MPs) bioaccumulation is crucial to addressing the pollution in these ecosystems, particularly in restored areas. Here, we 1) evaluate the MPs plastic-biota-sediment accumulation factor (pBSAf) in the fiddler crab Minuca rapax and 2) describe MPs type, colour, and polymeric characteristics in areas with varying restoration and degradation levels in the Southern Gulf of Mexico. We used regression models to evaluate the role of mangrove tree height, basal area, and crab individuals' density in explaining pBSAf. The highest pBSAf values were observed in natural and restored mangrove areas, particularly those with higher crab densities and taller trees. MPs were more diverse in composition in both crabs and sediments from natural areas. Mangrove biota tissue's bioaccumulation may provide insights into ecosystem health and food web impacts and indicate restoration progress.

How Does Mangrove Restoration or Reforestation Change Trace Metal Pollution in Mangrove Ecosystems? A Review of Current Knowledge

In recent years, mangrove restoration has gained significant attention due to its carbon storage capacity, role as a pollution sink, and ecological and economic benefits. Moreover, the United Nations Sustainable Development Goals' strategies include mangrove restoration. This review investigates the status of mangrove restoration research and the influence of restoration on trace metal accumulation, speciation, and associated risks in mangrove sediments. Our analysis reveals that research on mangrove restoration is increasing globally, with a notable surge in publications after 2017. However, fewer than 25 articles published between 2007 and 2024 address trace metals in restored mangroves, indicating limited focus from researchers on this topic. Research shows that mangrove restoration can quickly alter sediment properties, such as texture, salinity, and pH. As a result, restored sediments tend to accumulate higher organic carbon content than barren areas. Most studies also suggest that trace metal accumulation is higher in restored sites than in non-restored areas. However, metal speciation varies considerably between sites due to local environmental factors. Furthermore, many studies suggest that restoration may increase the risks posed by trace metals to aquatic biota. The challenges of mangrove restoration research include short study timeframes, low success rates, poorly defined targets, small-scale efforts, conflicts with local communities over resources and benefits, insufficient government funding, and a lack of historical data on community health and pollution status.