Leaf litter degradation and nutrient supply in the mangroves of Mecoacán Lagoon, Gulf of Mexico. Mangroves are ecosystems with a high primary productivity that is mainly driven mainly by degradation processes. Energy (nutrients) flows from mangroves toward adjacent zones and the surrounding aquatic environment. The objective of the present study was to estimate the daily degradation coefficient (k) of mangrove leaves in relation to physical-chemical soil factors and in situ nutrient supply (phosphorus and nitrogen) in Mecoacán Lagoon, Gulf of Mexico. Leaf litter degradation bags were placed at six monthly monitoring sites to evaluate degradation and to calculate the corresponding degradation coefficients. A rapid degradation of up to 51 % was observed for Avicennia germinans (L.) Stearn during the first month in association with leaching resulting from flood conditions. The degradation of Rhizophora mangle (L.) (k= 0.0052±0.0002) (F= 12.2 p< 0.05 n= 216) and Laguncularia racemosa (L.) Gaertn (k= 0.005±0.0003) (F= 3.7 p= 0.2 n= 108), differed significantly from that of A. germinans (k= 0.009 ± 0.0003) (F= 1.2 p= 0.2 n= 216) did not present significant differences. To reach T50 degradation, R. mangle and L. racemosa required more time (133 and 138 days, respectively) than A. germinans (74 days). Organic matter and soil humidity were significantly correlated with the decay constant of A. germinans (r= 0.65 p< 0.05 and r= 0.55 p< 0.05, respectively). Total nitrogen content was highest in the Pajaral site (2 683 mg.kg) and was also highly correlated with organic matter content (r= 0.9 p= 0.003). Total phosphorus content was highest in the Boca site (2 031 mg.kg) and was also negatively correlated with pH (r= -0.61 p= 0.004). In conclusion, differences in the rate of mangrove leaf degradation depend on the involved species (leaf composition), time of exposure or immersion in water (flooding patterns) and sediment heterogeneity (i.e., texture, pH, humidity content and bulk density). Rev. Biol. Trop. 66(2): 892-907. Epub 2018 June 01.