Mangrove leaf litter decomposition under mangrove forest stands with different levels of pollution in the Niger River Delta, Nigeria

摘要

Nutrient cycling often moves between litter fall and decomposition. It is hypothesized that hydrocarbon pollution will slow down mangrove litter decomposition because of the reduction in microbial activities. We studied decomposition rates at different levels of pollution (i.e. high and low) and amongst different mangrove species (i.e. red, white and black). For the first experiment, fresh leaves of Rhizophora racemosa were collected, sealed in a litter bag and placed on the mangrove floor for 1.24 years at which all the leaves had completely decomposed to humus and were oven-dried and weighed to calculate the decomposition rate constant (k) of mass loss. Although there was no significant difference in the rate of decomposition (P > 0.05), leaves at the highly polluted plot had lower rate of decomposition (6.58 x 10(-4)) when compared to leaves at the lowly polluted plot (1.75 x 10(-3)). In the second experiment, there was a significant difference in decomposition rates amongst species (P 0.05). Red mangrove leaves (0.41) decomposed more than white (0.28) and black (0.28) mangrove leaves. This implies that hydrocarbon pollution slowed, but did not stop the decomposition of mangrove leaves.