Ecological Stoichiometry and Nutrient Cycling Dynamics in Degraded and Restored Mangrove Ecosystems of the Niger Delta

Mangrove ecosystem restoration in the Niger Delta requires deeper mechanistic understanding of nutrient cycling dynamics, particularly how the stoichiometric relationships between carbon, nitrogen, and phosphorus shift across degradation and recovery gradients, as nutrient limitation may constrain restoration trajectories in ways not captured by conventional biomass assessments. This study applies ecological stoichiometry theory to investigate nutrient cycling dynamics in degraded, actively restored, and intact reference mangrove stands across Delta and Bayelsa States. Six stand types were studied across twelve sites, encompassing different degradation causes (oil spill, logging, erosion) and restoration ages (three, seven, and twelve years post-restoration). Soil nutrient pools, leaf stoichiometric ratios, litter decomposition rates, microbial biomass carbon-to-nitrogen ratios, and nitrogen fixation rates were measured seasonally over two years. Stoichiometric imbalances in degraded stands showed nitrogen limitation as the primary constraint on microbial decomposition and plant growth recovery, particularly in oil-spill affected sites where hydrocarbon loading elevated carbon-to-nitrogen ratios significantly above threshold values. Twelve-year restored stands showed stoichiometric profiles approaching reference conditions for carbon, nitrogen, and phosphorus pools but not for leaf nitrogen-to-phosphorus ratios, suggesting continued phosphorus limitation in older restoration plots. Nitrogen fixation by pneumatophore-associated cyanobacteria was significantly higher in three-year restored stands, indicating compensatory biological nitrogen input during early recovery. The study develops the first nitrogen-cycle-centred restoration management protocol for Niger Delta mangroves, identifying targeted nitrogen amendment strategies for accelerating stoichiometric recovery. Keywords: ecological stoichiometry, mangrove restoration, nutrient cycling, Niger Delta, nitrogen limitation