Decomposition of the seagrass Halophila stipulacea (Forsk.) Aschers. followed in situ over 340 days showed that the plant lost 40.8% of its initial weight during the first 85 days and only 21.2% over the remaining 255 days of the incubation period. The observed overall rate of decay of 0.18% day −1 indicates the high resistance of Halophila tissue to decomposition. An exponential model showing a regularly decreasing decay coefficient was fitted to the data of weight loss. The correlation between observed and calculated weight remaining was highly significant ( r = 0.9881, P < 0.0001). The samples of decomposing leaf litter harboured 2.2 × 10 11 bacteria g −1 dry wt. on average and consumed 0.25−1.07 mg O 2 −1 dry wt. h −1. The early colonizing bacteria of the detritus were mostly non-sporogenous forms. The most prominent genera involved in decomposition were Actinomyces, Arthrobacter, Bacillus and Pseudomonas, all of which are capable of degrading structural carbohydrates.