Evaluating seagrass leaf litter decomposition: An experimental comparison between litter-bag and oxygen-uptake methods

Comparison of the decay rates of leaves of the seagrass Posidonia oceanica (L.) Delile have been performed under different experimental conditions (season, depth, and kind of material), using two methods: litter-bag incubation and oxygen uptake measurements. Weight loss in litter-bags was higher (i) in summer than in winter (ii) in shallow zones than In deep zones (iii) in senescent leaves still attached to the plant than in leaf litter fragments. Oxygen uptake rates were higher in summer add in senescent leaves, but no effect of the incubation depth was shown, indicating that mechanical effects are relevant for weight loss inside bags but not for metabolic processes. When compared on the same basis (carbon loss), decay rates obtained from oxygen uptake measurements were always lower than those obtained using litter bags. On average, only 40% of the weight loss observed in the litter bags is explained by respiratory consumption.